SXVF-H16 handbook.pdf - Starlight Xpress

Handbook for the SXVF-H16 Issue 1 August 2006 

Starlight Xpress Ltd 

SXVF-H16 

CCD camera user manual 

Thank you for purchasing a Starlight Xpress CCD camera. We hope that you will be 

very satisfied with the results. The SXVF-H16 is a high-resolution cooled CCD 

camera, especially designed for astronomical imaging. The SXVF-H16 uses a Kodak 

Interline CCD, with 2048 x 2048 pixels in a 15.1mm x 15.1mm active area. The use 

of high performance microlenses on the CCD surface gives the greatest possible 

throughput of light to the pixels and the resulting QE is very good over the entire 

visible spectrum. Our new ‘F’ type USB2 interface hardware gives an exceptionally 

fast download speed of about 2 megapixels per second, and so the SXVF-H16 can 

download a full resolution 16 bit image in only 2.5 seconds. 

1


Please take a few minutes to study the contents of this manual, which will help you to 

get the camera into operation quickly and without problems. I am sure that you want 

to see some results as soon as possible, so please move on to the ‘Quick Start’ section, 

which follows. A more detailed description of imaging techniques will be found in a 

later part of this manual. 

‘Quick Starting’ your SXVF-H16 system 

In the shipping container you will find the following items: 

1) The SXVF-H16 camera head. 

2) A power supply module and cable. 

3) A 3 metre USB2 camera cable. 

4) An adaptor for 1.25” drawtubes. 

5) An adaptor for 2” drawtubes and ‘Pentax’ thread lenses. 

6) A guider cable for ‘ST4’ style mount guiding inputs. 

7) A CD with the ‘SXVF_H16’ software. 

8) This manual. 

You will also need a PC computer with Windows 98SE, Windows 2000 or Windows 

XP. This machine must have at least one USB2.0 port and at least 256 Megs of 

memory. If you intend to view the finished images on its screen, then you will also 

need a graphics card capable of displaying an image in a minimum of 1024 x 768 

pixels and 24 bit colour. A medium specification Pentium with between 1GHz and 

3GHz processor speed is ideal. Please note that the SXVF-H16 is not designed for 

USB1.1 operation and will give inferior results if used on USB1.1. 

Connecting up: 

Plug the 5 pin DIN connector into the socket on the power supply box, and plug the 

power supply into the wall socket. The yellow LED on the power supply should light. 

2


Connect the miniature 4 way power plug to the socket on the rear of the camera and 

screw the retaining ring into place. The LED on the rear of the camera will light a dim 

yellow. The other connections should not be attached until after the software has been 

installed. 

Installing the software: 

Switch on the computer and allow it to ‘boot up’. Once you have the system ready to 

run, insert the program disk into your CD drive and select ‘Setup.exe’ if the disk does 

not autostart. The initial installation is to set up the USB drivers required by the SXV 

electronics. The files SXVIO.sys and Generic.sys are copied to your 

Windows\System32\Drivers folder and SXVIO_H16.inf is copied to Windows\Inf. 

After this, the program ‘SXV_H16_usb.exe’ will be installed into your ‘CCD’ 

directory and a new directory called ‘Autosave’ will now exist on the same drive. 

‘Autosave’ is where SXV_H16 will normally store its configuration file, 

‘SXVH16.ini’, and any image files, which are recorded using the ‘Autosave’ mode in 

SXV_H16 and saved in FITs format. 

Please note that the version of SXVIO.sys supplied with the H16, is an improved 

issue that should replace any copy that is already resident on your machine. Failure to 

update will result in a tendency for white spots and streaks to appear in your images. 

3


You now need to set up the camera control defaults (shown above), as follows: 

Start SXV-H16 by clicking on the icon and select the ‘File’ menu. Now select ‘Set 

program defaults’ and a window, which contains the various software settings, will 

appear. Suggested starting defaults are as follows: 

1) Background Image area Red (or as preferred) 

2) FITS Unsigned Integer format Off 

3) Star mask size (area used for photometry and guiding) 8 pixels 

4) Telescope guiding to autoguider socket 

The other default settings are not important for current purposes and may be left as 

the software start-up values for now. 

Recording your first image: 

We now have the camera and computer set up to take pictures, but an optical system 

is needed to project an image onto the CCD surface. You could use your telescope, 

but this introduces additional complications, which are best avoided at this early 

stage. There are two simple options, one of which is available to everyone: 

1) Attach a standard ‘M42’ SLR camera lens to the SXVF-H16, using the 27mm 

spacer to achieve the correct focal distance. 

4


2) Create a ‘Pin hole’ lens by sticking a sheet of aluminium baking foil over the end 

of the 1.25” adaptor and pricking its centre with a small pin. 

If you use a normal lens, then stop it down to the smallest aperture number possible 

(usually F22) as this will minimise focus problems and keep the light level reasonable 

for daytime testing. The pin hole needs no such adjustments and will work 

immediately, although somewhat fuzzily. 

5


Point the camera + lens or pinhole towards a well-lit and clearly defined object some 

distance away. Now click on the camera icon in the toolbar of the SXV-H16 software 

and the camera control panel will appear (see above). Select an exposure time of 0.1 

seconds and press ‘Take photo’. After the exposure and download have completed 

(between 1 and 3 seconds) an image of some kind will appear on the computer 

monitor. It will probably be poorly focused and incorrectly exposed, but any sort of 

image is better than none! In the case of the pinhole, all that you can experiment with 

is the exposure time, but a camera lens can be adjusted for good focus and so you 

might want to try this to judge the image quality that it is possible to achieve. 

One potential problem with taking daylight images is the strong infrared response of 

the SXVF-H16 as this will cause ‘soft focus’ with camera lenses. Soft focus is much 

reduced by keeping the aperture setting below F8. Also, IR blocking filters are 

available from various suppliers (True Technology, Edmunds etc.) and are 

recommended for the best results when using a lens. 

If you cannot record any kind of image, please check the following points: 

1) Is the power LED on 

2) Does the software indicate that the camera is successfully connected An attempt 

to take a picture will fail with an error message if the USB is not properly installed. In 

this case, try unplugging the USB cable and then reconnecting it after about 5 

seconds. Restart the camera software and see if it can link now. If not, check in 

Windows device manager (via ‘System’ in ‘Control Panel’) and see if the 

BlockIOClass device is installed properly. If all looks OK, try checking the ‘Disable 

VID/PID detection’ in the ‘Set program defaults’ menu and try again. 

6


3) If you cannot find any way of making the camera work, please try using it with 

another computer. This will confirm that the camera is OK, or otherwise, and you can 

then decide how to proceed. Also check on our web site to see if there are any updates 

or information about your camera software that might help. The message board might 

prove useful to ask for help with getting your camera operating properly. 

Our guarantee ensures that any electrical faults are corrected quickly and at no cost 

to the customer. 

Enhancing your image: 

Your first image may now be reasonably good, but it is unlikely to be as clear and 

sharp as it could be. Improved focusing and exposure selection may correct these 

shortcomings, and you may like to try them before applying any image enhancement 

with the software. However, there will come a point when you say, “That’s the best 

that I can get” and you will want to experiment with various filters and contrast 

operations. In the case of daylight images, the processing options are many, but there 

are few that will improve the picture in a useful way. 

The most useful of these are the ‘Normal Contrast Stretch’ and the ‘High Pass Low 

Power’ filter. The high pass filter gives a moderate improvement in the image 

sharpness, and the effects of image processing. This can be very effective on daylight 

images. Too much high pass filtering results in dark borders around well-defined 

features and will increase the ‘noise’ in an image to unacceptable levels, but the ‘Low 

Power’ filter is close to optimum and gives a nicely sharpened picture, as above. 

The ‘Contrast’ routines are used to brighten (or dull) the image highlights and 

shadows. A ‘Normal’ stretch is a simple linear operation, where two pointers (the 

‘black’ and ‘white’ limits) can be set at either side of the image histogram and used to 

define new start and end points. The image data is then mathematically modified so 

that any pixels that are to the left of the ‘black’ pointer are set to black and any pixels 

to the right of the ‘white’ pointer are set to white. The pixels with values between the 

pointers are modified to fit the new brightness distribution. Try experimenting with 

the pointer positions until the image has a pleasing brightness and ‘crispness’. 

At this point, you will have a working knowledge of how to take and process an 

SXVF-H16 image. It is time to move on to astronomical imaging, which has its own, 

unique, set of problems! 

********************************************************************* 

Astronomical Imaging with the SXVF-H16 

1) Getting the image onto the CCD: 

It is fairly easy to find the correct focus setting for the camera when using a standard 

SLR lens, but quite a different matter when the H16 is attached to a telescope! The 

problem is that most telescopes have a large range of focus adjustment and the CCD 

needs to be quite close to the correct position before you can discern details well 

7


enough to optimise the focus setting. An additional complication is the need to add 

various accessories between the camera and telescope in order that the image scale is 

suitable for the subject being imaged and (sometimes) to include a ‘flip mirror’ finder 

unit for visual object location. 

A simple, but invaluable device, is the ‘par-focal eyepiece’. This is an eyepiece in 

which the field stop is located at the same distance from the barrel end, as the CCD is 

from the camera barrel end. 

When the par-focal eyepiece is fitted into the telescope drawtube, you can adjust the 

focus until the view is sharply defined and the object of interest is close to the field 

centre. On removing the eyepiece and fitting the CCD camera, the CCD will be very 

close to the focal plane of the telescope and should record the stars etc. well enough 

for the focus to be trimmed to its optimum setting 

Several astronomical stores sell par-focal eyepieces, but you can also make your own 

with a minimum of materials and an unwanted Kellner or Plossl ocular. 

Just measure a distance of 22mm from the field stop of the eyepiece (equivalent to the 

CCD to adaptor flange distance of the camera) and make an extension tube to set the 

field stop at this distance from the drawtube end. Cut-down 35mm film cassette 

containers are a convenient diameter for making the spacer tube and may be split to 

adjust their diameter to fit the drawtube. 

Another popular solution to the ‘find and focus’ problem is the ‘flip mirror’ unit. 

These operate on a similar principle to the single lens reflex camera, where a hinged 

mirror can drop into the light path and reflect the image through 90 degrees into a 

viewing eyepiece. 

In this case, the camera and eyepiece are made par-focal with each other by locking 

up the mirror, focusing the camera on an easy object, such as a moderately bright star 

and then flipping the mirror down to view the same star with the eyepiece. Once the 

eyepiece has been locked into the correct position, you can use it to focus on the 

image by lowering the flip mirror and operating the telescope focus wheel until the 

image is sharp. When the mirror is raised, the image will fall onto the CCD surface 

and should be accurately in focus. Most flip mirror units allow several adjustments to 

8


be made, so that the image can be centred properly in the eyepiece and CCD fields, 

which are not necessarily coincident when you first buy your unit! 

Opinions vary as to the utility of flip mirrors. They are a convenient way to find and 

focus, but they add quite a bit of extra length between the camera and telescope. This 

can be very inconvenient with Newtonians, and not a lot better with SCTs, especially 

if the assembly is somewhat flexible. They also make it difficult to use a focal reducer 

with your camera, as the rapidly converging light cone from a reducer cannot reach all 

the way through the flip mirror unit to the CCD surface. If you are using one of the 

popular F3.3 compressors for deep sky imaging, you will NOT be able to include a 

flip mirror unit in front of your camera and a par-focal eyepiece is your best option. 

Whichever device you use, it is necessary to set up a good optical match between your 

H16 and the telescope. Most SCTs have a focal ratio of around F10, which is too high 

for most deep sky objects and too low for the planets! This problem is quite easy to 

overcome, if you have access to a telecompressor (for deep sky) and a Barlow lens for 

planetary work. The Meade F6.3 compressor is very useful for CCD imaging and I 

can recommend it from personal experience. It does not require a yellow filter for 

aberration correction, unlike some other designs, so it can be used for colour imaging. 

Barlow lenses are less critical and most types can be used with good results. However, 

if you are buying one for CCD imaging, I recommend a 3x or 5x amplifier, or the 

planets will still be rather small in your images. As a guide, most CCD astronomers 

try to maintain an image scale of about 2 arc seconds per pixel for deep sky images. 

This matches the telescope resolution to the CCD resolution and avoids 

‘undersampling’ the image, which can result in square stars and other unwanted 

effects. To calculate the focal length required for this condition to exist, you can use 

the following simple equation: 

F = Pixel size * 205920 / Resolution (in arc seconds) 

9


In the case of the SXVF-H16 and a 2 arc seconds per pixel resolution, we get 

F = 0.0074 * 205920 / 2 

= 762mm 

For a 200mm SCT, this is an F ratio of 762 / 200 = F3.8, which is too short to be 

achieved with the Meade F6.3 converter, but a slightly longer focal length will not be 

a problem. Any F ratio from about F4 to F6 will give good results and you might try 

experimenting with the camera to reducer spacing to optimise the performance. 

Because of the large CCD size used in the H16, field vignetting will be a problem 

with many ‘scopes when used with a converter. The larger SCTs and many of the new 

‘APO’ refractors will not suffer from this issue, but you may have to compromise on 

vignetting when using a small SCT. Application of a ‘flat field’ to your images will 

help to remove the edge shading, but the star images may well be distorted around the 

periphery of the image, due to field curvature. 

The same equation can be used to calculate the amplification required for good 

planetary images. However, in this case, the shorter exposures allow us to assume a 

much better telescope resolution and 0.25 arc seconds per pixel is a good value to use. 

The calculation now gives the following result: 

F = 0.0074 * 205920 / 0.25 

= 6088mm 

This is approximately F30 when used with a 200mm SCT and so we will need a 3 x 

Barlow lens to get a reasonable size of planetary image. 

Achieving a good focus: 

Your starting point will depend on the focus aids, if any, which you are using. With 

the par-focal eyepiece, you should slip the eyepiece into the drawtube and focus 

visually on a moderately bright star (about 3 rd magnitude). Now withdraw the 

eyepiece and carefully insert the camera nosepiece until it is bottomed against the 

drawtube end and lock it in place. With the flip mirror unit, all that is needed is to 

swing the mirror down and adjust the focus until the star is sharply defined and 

centred in the viewing eyepiece. Now lift the mirror and you are ready to start 

imaging. 

SXV_H16 has a focus routine that will repeatedly download and display a 100 x 100 

pixel segment of the image at relatively high speed. This focus window may be 

positioned anywhere in the camera field and can be displayed with an adjustable 

degree of automatic contrast stretching (for focusing on faint stars). To use this mode, 

start up the software and select the H16 camera interface (File menu). Set the camera 

mode to ‘Bin 1x1’ and select an exposure time of 1 second. Press ‘Take Picture’ and 

wait for the image to download. There is a good chance that your selected star will 

appear somewhere within the image frame and it should be close to a sharp focus. If 

the focus is still poor, then it may appear as a pale disk of light with a dark centre (the 

secondary mirror shadow in an SCT, or Newtonian). Now select the ‘File’ menu again 

and click on ‘Focus frame centre’; you can now use the mouse pointer to click on the 

star image and the new focus frame co-ordinates will be displayed. Now return to the 

camera interface window and click on ‘Start’ in the Focus frame. The computer will 

10


now display a continuous series of 100 x 100 pixel images in the focus window and 

you should see your selected star appear somewhere close to the centre. A ‘peak 

value’ (the value of the brightest pixel) will also be shown in the adjacent text box and 

this can be used as an indication of the focus accuracy. Although the peak value is 

sensitive to vibration and seeing, it tends towards a maximum as the focus is 

optimised. Carefully adjust the focus control on your telescope until the image is as 

sharp as possible and the peak value reaches a maximum. Wait for any vibration to 

die down before accepting the reading as reliable and watch out for bursts of bad 

seeing, which reduce the apparent focus quality. Quite often, the peak value will 

increase to the point where it is ‘off scale’ at 4095 and in this case you must halt the 

focus sequence and select a shorter exposure if you wish to use the peak value as an 

indicator. Once you are happy with the focus quality achieved, you might like to trim 

the settings of your par-focal or flip mirror eyepiece to match the current camera 

position. Although you can reach a good focus by the above method, many observers 

prefer to use additional aids, such as Hartmann masks (an objective cover with two or 

three spaced holes) or diffraction bars (narrow parallel rods across the telescope 

aperture). These make the point of precise focus easier to determine by creating 

‘double images’ or bright diffraction spikes around stars, which merge at the setting 

of exact focus. The 12-16 bit slider control allows you to adjust the contrast of the 

focus frame for best visibility of the star image. It defaults to maximum stretch (12 

bits), which is generally ideal for stars, but a lower stretch value is better for focusing 

on planets. 

Taking your first astronomical image: 

I will assume that you are now set up with a focused camera attached to a telescope 

with an operating sidereal drive. If so, you are now in a position to take a moderately 

long exposure of some interesting deep-sky astronomical object (I will deal with 

planets later!). As most drives are not very accurate beyond a minute or two of 

exposure time, I suggest that you find a fairly bright object to image, such as M42, 

M13, M27 or M57. There are many others to choose from, but these are good 

examples. 

Use the finder to align on your chosen object and then centre accurately by using the 

focus frame and a short exposure of between 1 and 5 seconds. The ’12-16 bit’ slider 

in the focus frame allows you to adjust the image contrast if you find that the object is 

too faint with a short exposure. Once properly centred and focused, take an exposure 

of about 60 seconds, using the ‘Bin 1x1’ mode and observe the result. Initially, the 

image may appear rather barren and show only a few stars, however, there is a great 

deal of data hidden from view. You can get to see a lot of this, without affecting the 

image data, if you go to the ‘View’ menu and select ‘Auto Contrast Stretch Image’. 

The faint image data will then appear in considerable detail and I think that you will 

be impressed by the result! 

If you are happy with the image, go to the ‘File’ menu and save it in a convenient 

directory. 

Now you need a ‘dark frame’, if the best results are to be extracted from your raw 

image. To take this, just cover the telescope objective with the lens cap, or drop the 

flip mirror to block the light path to the CCD (make sure that this is light tight), and 

11


take another 60 second exposure. This image will be a picture of the dark signal 

generated during your exposure and it should be saved with your image for use in 

processing the picture. The SXVF-H16 generates very little dark signal and so dark 

frames are not essential for short exposures of less than a few minutes, but it is a good 

idea to record at least one for each exposure time used during an imaging session. As 

variations in ambient temperature will affect the dark signal, it is best to take the dark 

frames within a few minutes of capturing your images. For the same reason, it is not 

wise to use ‘old’ dark frames if you want the best possible results, however, some 

software allows you to scale library dark frames to match the image (e.g. AstroArt). 

‘Flat fields’ are often recommended for optimising the results from your CCD 

camera, but these are generally less important than dark frames, especially if you 

make sure that the optical window of the camera is kept dust-free. The purpose of a 

flat field is to compensate for uneven illumination and sensitivity of the CCD and it is 

better to avoid the need for one by keeping the optics clean and unvignetted. I will 

ignore flat fielding for current purposes and describe the process in detail at a later 

stage. 

Processing the deep-sky image: 

1) Make sure the ‘Auto Contrast Stretch’ is switched off and load your image into 

SXV_H16. Select ‘Merge’ and then ‘Subtract Dark Frame’. Pick the appropriate dark 

frame and the software will then remove the dark signal from your image, leaving it 

somewhat darker and smoother than before. 

12


2) The resulting image will probably look faint and dull, with a bright 

background due to light pollution. It is now time to process the ‘luminance’ 

(brightness and contrast) of the image to get the best visual appearance. First, 

use the ‘Normal’ contrast stretch to darken the background by setting the 

‘Black’ slider just below the main peak of the histogram. Alternatively, you 

can use the ‘Remove Background’ option to let the software decide on the best 

setting. This will greatly reduce the background brightness and the image will 

begin to look rather more attractive. You can now try brightening the 

highlights with another ‘Normal’ stretch, in which you bring down the ‘White’ 

slider to just above the main image peak. The best setting for this is rather 

more difficult to guess and you may need several attempts before the result is 

ideal. Just use the ‘Undo last filter’ function, if necessary, to correct a mistake. 

3) The image will now look quite impressive and I hope that you are pleased with 

your first efforts! Further small refinements are usually possible and you will become 

expert at judging the best way to achieve these as your experience increases. As a 

rough guide, the ‘Filters’ menu can be used to sharpen, soften or noise reduce the 

13


image. Strong ‘High Pass’ filters are usually not a good idea with deep sky images, as 

the noise will be strongly increased and dark rings will appear around the stars, but a 

‘Median’ filter can remove odd speckles and a mild ‘Unsharp Mask’ (Radius 3, Power 

1) will sharpen without too much increase in noise. 

Another thing to try is the summing several images for a better signal to noise ratio. 

Summing can be done in the ‘Merge’ menu and involves loading the first (finished) 

image, selecting a reference point (a star) then loading the second image and finding 

the same star with the mouse. Once the reference is selected, you can either add 

directly, or average the images together. Averaging is generally better, as you are less 

likely to saturate the highlights of the picture. The signal-to-noise ratio will improve 

at a rate proportional to the square root of the number of summations (summing 4 

images will double the signal-to-noise), but different exposures must be used. 

Summing an image with itself will not change the S/N ratio! 

A deep image of the Deer-Lick galaxy group by Rick Krejci 

Although I have concentrated on the use of a telescope for deep-sky imaging, do not 

forget that you have the option of using an ordinary camera lens for impressive widefield 

shots! A good quality 200mm F3.5 lens with an infrared blocking filter will yield 

14


very nice images of large objects, such as M31, M42, M45 etc. If you cannot obtain a 

large IR blocker for the front of the lens, it is often quite acceptable to place a small 

one behind the lens, inside the adaptor tube. 

Taking pictures of the planets: 

Planetary imaging is in many ways quite different from deep sky imaging. Most deep 

sky objects are faint and relatively large, so a short focal length and a long exposure 

are needed, while planets are bright and very small, needing long focal lengths and 

short exposures. High resolution is critical to achieving good results and I have 

already shown how a suitable focal length can be calculated and produced, using a 

Barlow Lens. 

Many camera users comment on the difficulty of finding the correct focus when 

taking pictures of Jupiter etc. This is usually due to poor seeing conditions, which are 

only too common, but may be due in part to poor collimation of your telescope. 

Please ensure that the optics are properly aligned as shown by star testing, or by using 

one of the patent collimation aids that are widely available. It is also better to use a 

star for initial focusing, as planetary detail is difficult to judge in bad seeing. Although 

the star will also suffer from blurring, the eye can more easily gauge when the most 

compact blur has been achieved! 

You could begin by imaging lunar craters, but the colour content is low and so I 

recommend Jupiter, Saturn or Mars. The rapid variations of seeing which accompany 

planetary imaging, will ruin the definition of about 95% of your images and so I 

recommend setting the camera to run in ‘Autosave’ mode. This will automatically 

take a sequence of images and save them with sequential file names in your 

‘Autosave’ directory. Dozens of images will be saved, but only one or two will be 

satisfactory for further processing. 

To start the Autosave process, call up the SXV Camera Interface and select the 

‘Continuous Mode’ check box at the top (make sure the rest are unchecked). Now 

check the ‘Autosave Image’ checkbox near the bottom of the window. If you now 

click on ‘Take Picture’ the automatic sequence will begin and will not stop until you 

press a computer key. The images will be saved in FITs format with sequential names 

such as ‘Img23, Img24….’ and will be found in the ‘Autosave’ directory (or a subdirectory 

of Autosave, set up in the program defaults menu). 

The exposure time needed for good planetary images is such that the image histogram 

has a peak value at around 127 and does not extend much above 200 (Ignore the 

major peak near zero, due to the dark background). If you use too short an exposure 

time, the image noise level will be increased, and if too long a time is used you will 

saturate the highlights and cause white patches on the decoded image. With the 

recommended focal length, Jupiter and Mars will both need an exposure time of 

between 0.1 and 1 seconds and Saturn will need between 0.5 and 2 seconds. 

15


Processing a planetary image: 

Planetary images have one major advantage over deep sky images, when you come to 

process them – they are MUCH brighter, with a correspondingly better signal to noise 

ratio. This means that aggressive sharpening filters may be used without making the 

result look very noisy and so some of the effects of poor seeing can be neutralised. 

A raw image 

Try applying an ‘Unsharp Mask’ filter with a radius of 5 and a power of 5. This will 

greatly increase the visibility of any detail on the planet, but the optimum radius and 

power will have to be determined by experiment. In general terms, the larger the 

image and the worse the seeing, then the wider the radius for best results. My Jupiter 

shots are usually about half the height of the CCD frame and I find that the ‘radius 5, 

power 5’ values are good for most average seeing conditions. If you have 

exceptionally good conditions, then a reduction to R=3, P=3 will probably give a 

more natural look to the image, as too large a radius and power tends to outline edges 

with dark or bright borders. 

16


As a finishing touch, the application of a Median filter or a Weighted Mean Low Pass 

filter can be useful to smooth out the high frequency noise after a strong Unsharp 

Mask. 

As with deep-sky images, it is advantageous to sum planetary images together to 

improve the signal to noise ratio. In this case, the ‘averaging’ option should always be 

used, or the result is likely to exceed the dynamic range of the software and saturate 

the highlights. Aligning the images is always something of a problem, as there are 

rarely any stars to use when imaging the planets, but Jupiter’s satellites can be useful 

reference points. Otherwise, you will have to find a well-defined feature on the planet, 

or estimate where the centre of the disk is located. Some more sophisticated software 

can automatically align many planetary images and I recommend ‘Registax’ for this. 

********************************************************************* 

‘Slew & Sum’ imaging: 

Other features of SXV_H16 

The SXVF-H16 can be used in an automatic image-stacking mode, called ‘Slew & 

Sum’. The camera is set to take several sequential exposures, which are automatically 

‘slewed’ into alignment and then summed together by the software. This mode can 

help to overcome a poor RA drive by summing images that have exposure times 

shorter than the drive error period. The resulting image has more noise than a single 

exposure of the same total length, but this method of imaging is still an effective way 

of making long exposures. 

To take an S&S image, go to the camera interface window and select an exposure 

time for one image of the sequence. Do not use a very short exposure time, as the 

read-out noise will become dominant. About 30 seconds is a reasonable minimum. 

Now go to the ‘Multiple Exposure Options’ and select a number of exposures to take. 

You can also select to average the images, rather than adding them, and there is a 

‘Alternative Slew Mode’ available, which uses the correlation of image areas, rather 

than a single star. This mode can be better in dense star fields. 

Another option is ‘Auto remove dark frame’. This is advisable with S&S images, as 

the slewing will mis-register the images with a single dark frame that is applied to the 

finished sequence. To use this option, you will need a dark frame, taken with the same 

exposure time as a single image from the sequence. This is stored on drive C with the 

name ‘dark.def’ 

Now click on ‘Take Picture’ and the sequence will begin. 

Taking and using a flat field: 

Flat fields are images, which display only the variations of illumination and 

sensitivity of the CCD and are used to mathematically modify a wanted image in such 

a way that the errors are removed. Common flat field errors are due to dust motes on 

the camera window and vignetting effects in the optical system of the telescope. Dust 

motes act as ‘inverse pinholes’ and cast out-of-focus images of the telescope aperture 

onto the CCD chip, where they appear as shadow ‘do-nuts’. Most optical systems 

17


show some vignetting at the edges of the field, especially when focal reducers are 

used. This causes a brighter centre to show in images, especially when there is a lot of 

sky light to illuminate the field. 

If dust motes are your main problem, it is best to clean the camera window, rather 

than to rely on a flat field to remove the do-nuts. Flat fields always increase the noise 

in an image and so physical dust removal is the best option. If you have serious 

vignetting, first check whether the optical system can be improved. The most likely 

cause of this problem is trying to use too powerful a degree of optical compression 

with a focal reducer and you might want to try moving the camera closer to the 

reducer lens. 

If you really do need to use a flat field for image correction, then it must be taken with 

care. It is most important that the optical system MUST NOT be disturbed between 

taking your original images and taking the flat field. Any relative changes of focus 

and rotation etc. will upset the match between flat field and image and the result will 

be poor correction of the errors. The other necessity for recording a good flat field is a 

source of very even illumination for the telescope field. This is surprisingly difficult 

to achieve and many designs of light source have appeared in the literature and on the 

Web. These usually consist of a large lightweight box, containing several lamps and 

an internal coating of matt white paint, which is placed over the objective of the 

telescope to provide an evenly illuminated surface. These can work well, but I prefer a 

simpler method, as follows: 

Most imaging sessions begin or end in twilight and so the dusk or dawn sky can 

provide a distributed source of light for a flat field. However, using the sky directly is 

likely to result in recording many unwanted stars, or patches of cloud etc., so a 

diffuser needs to be added to the telescope. An ideal material is Mylar plastic 

draughting film, obtained from an office supplies warehouse. It is strong and water 

resistant and can be easily replaced if damaged. Stretch a piece of the film loosely 

across the aperture of your telescope and point the instrument high in the sky, to avoid 

any gradient in the light near the horizon. Now take several images with exposure 

times adjusted to give a bright, but not overloaded, picture. Averaging flat field 

together is a good way to reduce their noise contribution and so recording 4, or more, 

images is a good idea. 

To use your flat fields, they must first have a dark frame subtracted. Although this 

may appear to be unimportant with such brightly lit and short exposures, there is the 

‘bias offset’ of the camera in each image and this can produce an error in the final 

correction. As we are mainly interested in the bias, any very short exposure dark 

frame will give a good result. The dark subtracted images should then be averaged 

together before use. 

After the above procedures have been executed, the flat field will be ready for use. 

Load up your image for processing, subtract the dark frame and then select ‘Apply 

flat field’ in the ‘Merge’ menu. The result should be an image with very little sign of 

the original artefacts. 

18


******************************************************************** 

The accessory ports 

The SXVF-H16 is provided with two ports for use with accessories. The Autoguider 

output port is a 6 way RJ11 socket, which is compatible with the standard autoguider 

input of most telescope mounts. It provides 4 active-low opto-isolator outputs and a 

common return line, capable of sinking a minimum of 5mA per output. This socket 

may be used for telescope control if the SXVF-H16 is employed as an autoguider, but 

is primarily intended to be the control output for the optional add-on autoguider 

camera head, available for use with the SXVF-H16. 

The high density parallel port socket provides both control and power for the add-on 

autoguider, but also includes a pair of serial ports for use with other devices. 

Using the built-in serial ports 

The SXVF-H16 incorporates two fast serial ports for use with external accessories. 

The ports are available on 5 pins of the 18 way connector that is provided for the 

autoguider and may be accessed by plugging in a ‘serial port divider box’. The divider 

box and cables are available as an accessory and may be chained in series with the 

autoguider cable, when the guider is in use, or may be used on its own. 

The two serial connections are in the form of standard RS232 PC style plugs and 

provide TX, RX and Ground connections at RS232 levels. Access is via commands 

sent through the USB connection and, at the time of writing, is limited to any serial 

controls that are provided by the SXV software. It is expected that many more 

functions will be added as the software is upgraded. 

********************************************************************* 

Using the add-on autoguider: 

A very useful accessory is the add-on autoguider head, which takes its power and 

control signals directly from the SXV camera, via the 18 way socket on its rear panel. 

The autoguider is only 1.25” in diameter and has a video style ‘CS’ mount thread in 

its nose, so video lenses may be attached. The guider may be used with either an offaxis 

prism assembly mounted in front of the SXV camera, or with a separate guide 

telescope, rigidly mounted alongside your imaging telescope. I personally use it with 

19


an 80mm aperture F5, inexpensive refractor as a guide ‘scope, but a shorter focal 

length lens will make more guide stars available in any given region of sky (See the 

picture below). 

To use the autoguider, first orient it so that the connector plug is roughly parallel to 

the declination axis of your mount. This is not absolutely essential, as the training 

routine will learn the angle of the head and compensate for it, but it is easier to 

understand the motion of the guide star if the guider frame is aligned with the RA and 

Dec axes. Now connect the head to the SXV camera, using the 18 way connector lead, 

including the port divider box, if it is to be used. 

The recommended way of connecting the autoguider output to the mount is to use an 

RJ11 telephone lead between the socket on the SXV camera and the autoguider input 

of your mount. This output is ‘active low’ (i.e. the control relays pull the guider inputs 

down to zero volts when applying a guide correction) and matches most of the 

autoguider inputs on commercial mounts. If ‘active high’ inputs are needed, or a very 

low control voltage drop is essential, then you will need to add a Starlight Xpress 

‘relay box’ between the guider output and the input to the mount. Please contact your 

local distributor if a relay box is required. Some mounts (Vixen, for example) use a 

similar guider input socket, but have re-arranged connections. Details are given on our 

web pages at the end of the ‘STAR2000’ section. 

The autoguider installed on a 80mm refractor guide ‘scope in the author’s garden 

20


To use the autoguider, please proceed as follows: 

1) Having started the SXVF-H16 software, open the autoguider control panel by 

clicking on the autoguider menu button. 

The autoguider control panel with a guide star selected 

2) Press the ‘Start’ button and a series of 1 second exposure guider images will 

begin to appear in the picture frame. If the images look too dim, use the 

‘Stretch Image’ slider to increase its contrast and brightness until the noise 

begins to be visible. 

3) If you haven’t focused the guider lens or ‘scope, move the mount until a bright 

star is visible on the guider image and then adjust the focus until it is as sharp 

as possible. 

4) At this point, you may want to test the guiding control by pressing the manual 

‘Move Telescope’ buttons at the bottom left corner of the control panel. You 

can watch the position of any stars in the guider image and confirm that they 

move in response to the buttons. The movement should be slow if the correct 

guiding rate is selected on your mount (typically 2x sidereal). Adjust this, if 

necessary. 

5) Move the mount until the required object for imaging is properly framed in the 

main CCD image (leave the guider menu and use the main camera control 

panel, as necessary). 

6) Re-open the guider control panel, start imaging and try to locate a clearly 

visible guide star. If necessary, make adjustments to the guide telescope or offaxis 

guider until one is found. 

7) Press ‘Stop’ and then press ‘Select Guide Star’. Use the mouse to left click on 

the selected star and a green cross will highlight it and the co-ordinates will 

appear in the text boxes above the image window. 

8) The various guiding rate defaults, listed on the right-hand side of the control 

panel, are unlikely to be perfect for your particular telescope and mount. You 

have the option of manually selecting values, or asking the software to attempt 

to determine what they should be. This is done by pressing the ‘Train’ button 

and waiting for the software to complete a sequence of automatic moves and 

21


calculations. The training will also determine the angle at which the guide 

camera is oriented with respect to the RA and Dec axes. If you do not wish to 

train the system at this time, the default values of 6 pixels per second will 

serve as a starting point. 

9) Now press ‘Go to main camera’ and the guider control panel will be replaced 

by the camera control panel. Set the required exposure time for the image (say 

5 minutes) and press the ‘Autoguide next image’ button. The autoguider 

window will reappear and, after a few seconds, you should see error values 

appearing in the text windows at the top. The guide star will be fairly close to 

the green cross, although not necessarily accurately centred, and you should 

see the power/ guide LED on the rear of the camera brighten and change 

colour with each correction. 

10) If the star begins to drift away from the cross, despite the corrections being 

made, the chances are that the N/S and/or E/W directions are set wrongly. 

Judge which axis is incorrectly set by observing the direction of the drift and 

then stop the exposure by pressing ‘Esc’. Open the guider control panel and 

check the appropriate swap box(es). After this operation, you will probably 

need to find the guide star again by taking a guider image and reselecting the 

star, as before. Now return to the main camera menu and try the ‘Autoguide 

next image’ button again. 

11) Once guiding is taking place without problems, the main exposure can be 

allowed to finish and, if all is well, you should see an image with tiny circular 

stars. 

If the stars are not circular, you may need to alter the guiding parameters, or 

investigate the rigidity and drive performance of your mount. A lot of information 

can be deduced by watching the behaviour of the guide star in the guider frame. If 

it is continually moving between two locations, either side of the green cross, then 

the RA or Dec pixels per second value is set too low. The higher these values are 

set, the gentler the guiding becomes. Too low a value will cause an overaggressive 

correction to be made and result in oscillation of the star position 

between two points. 

Another source of guiding errors can be a too accurately balanced telescope 

mount! Good balance can result in the telescope mount ‘bouncing’ between the 

gear teeth as corrections are made. A simple fix is to add a weight of about 0.5kg 

(1 pound) on the eastern end of the declination axis, so that there is always some 

pressure acting against the gear teeth. 

Getting a good result from an autoguider will often entail a lot of detective work 

to eliminate the sources of gear error, telescope flexure, mirror shift etc., but the 

final result is well worth the effort! 

22


********************************************************************* 

Camera maintenance: 

Very little maintenance is needed to keep the SXVF-H16 in excellent operating order, 

however two problems, which are common to all CCD equipment, are likely to show 

up on occasion. These are dust and condensation. 

Removing Dust: 

1) Dust can be deposited on either the optical window (not a big problem to cure), or 

on the CCD faceplate (difficult to eliminate entirely). When small particles collect on 

the window they may not be noticed at all on deep sky (small F ratio) images, as they 

will be very much out of focus. However, if a powerful contrast boost of the image is 

carried out, they may well begin to show as the shadow ‘Do-nuts’ mentioned earlier. 

Images taken with a large F ratio optical system are more likely to be affected by such 

dirt, owing to the smaller and sharper shadows that they cast. There is no great 

difficulty in removing such particles on the outside surface by the careful use of a lens 

cleaning cloth or ‘air duster’ and so you should have little trouble with this aspect of 

maintenance. Dust on the CCD faceplate is a much greater nuisance, as it casts very 

sharply defined and dark shadows and it entails dismantling the camera to get rid of 

it! To clean the CCD you will need a good quality lens cloth (no silicone) or tissues 

and some high-grade isopropyl alcohol. A very suitable cloth is the ‘Micro-Fibre’ 

type marketed by PENTAX etc., and suitable alcohol is available from TANDY 

(Radio Shack) etc. as tape head cleaning fluid. A bright light and a strong 

watchmakers eyeglass will also be found essential. 

Procedure: 

1) Disconnect the lead from the camera head and remove it from the telescope. Place 

it on a table with the optical window facing downward. 

23


2) Remove the two M3 screws from the camera back plate and ease the plate out of 

the camera body. You may need to press down with a finger on the USB socket while 

pulling up on the camera barrel to overcome the friction. 

3) Withdraw the body cylinder and unscrew the two long spacer pillars from the heat 

sink plate assembly. The SXV-H9 is shown, but all the SXV cameras are similar in 

design. 

4) The entire camera electronic assembly can now be lifted away from the camera 

front barrel and the CCD will be readily accessible. Note that a layer of white heatsink 

compound is applied to the periphery of the heat sink disc and this should be left 

undisturbed by subsequent operations. 

5) You can now closely examine the CCD faceplate under the spotlight using the 

watchmaker's glass when any dust motes will show clearly. If there is only an odd 

particle or two and the CCD is otherwise clean, carefully brush away the dust with a 

corner of your lens cloth. A smeared or very dusty CCD will need a few drops of 

alcohol to clean thoroughly and you may have to make several attempts before the 

surface is free of contamination. One gentle wipe from one end to the other, with no 

return stroke, will be found to be the most effective action. DO NOT rub vigorously 

and be very careful to avoid scratching the window. 

6) Before re-assembly, make certain that the inside surface of the front window is also 

clean, and then carefully replace the camera front barrel and screw it into place. (If the 

heat sink seal is disturbed, renew it with fresh compound before reassembling). 

7) Replace all the camera parts in reverse order and the job is done. 

24


Dealing with condensation: 

The SXVF-H16 is designed to avoid condensation by minimising the volume of air 

trapped within the CCD cavity. This normally works well, but storage of the camera 

in a humid location can lead to the trapped air becoming moist by diffusion through 

the optical window mounting thread etc. and result in condensation on the CCD 

window. If this becomes a problem, try to store the camera in a warm, dry place, or in 

a plastic lunch box containing a sachet of silica gel desiccant. 

N.B. DO NOT leave the camera switched on for long periods between uses. The 

cold CCD will collect ice by slow diffusion through any small leaks and this will 

become corrosive water on the cooler and CCD pins when the power is removed. If 

substantial amounts of moisture are seen on the CCD, dismantle the camera and 

dry it thoroughly. 

********************************************************************* 

Alternative Software 

Although we hope that you will be satisfied with ‘SXV_H16_usb’, other companies 

are offering alternative software. The most active and successful of these is ‘AstroArt’ 

by MSB software. You can purchase AstroArt from many dealers Worldwide and 

more information may be obtained from their web site at 

http://www.msb-astroart.com 

Maxim DL is also a very popular option and may be purchased from many 

astronomical equipment dealers. Their web site is at http://www.cyanogen.com 

Please note that any ‘Download progress’ indicators in third party software are best 

disabled so as to avoid disturbing the process of reading the camera data. 

********************************************************************* 

Aligning the CCD to the optical axis 

The large area of the KAI 4021 CCD can lead to problems of alignment between the 

CCD plane and the focal plane of the telescope. If you can detect uneven star image 

distortions towards the edge of the CCD field, this may indicate that the CCD plane 

needs to be adjusted. The front plate of the SXVF-H16 incorporates three sets of 

antagonistic screws that allow the plate to be tilted by up to about +/- 1 degree relative 

to the CCD surface. To make an adjustment, slacken the appropriate set screw and 

then turn the adjacent cap head screw in the required direction. Complete the 

adjustment by re-tightening the set screw. 

Avoid raising the plate by more than is necessary to level it, as a slight light leak may 

occur between the disk and camera body if the gap is large. 

25


********************************************************************* 

Some details of the camera and CCD characteristics 

CCD type: 

Kodak KAI 4021 interline CCD imager. 

CCD size: Active area 15.1 x 15.1mm 

Pixel size: 

QE peak: 

7.4 x 7.4uM 

approx. 55% at 500nM 

Spectral response: 

Dark signal: 

Power consumption: 

Typically 0.01 e per sec at 10C body temperature 

220v / 110v AC @ 12 watts max., 12v DC @ 750mA 

26


Dear User, 

Thank you for purchasing a Starlight Xpress CCD Imaging System. We are confident that you will gain 

much satisfaction from this equipment, but please read carefully the accompanying instruction manual 

to ensure that you achieve the best performance that is capable of providing. 

As with most sophisticated equipment a certain amount of routine maintenance is necessary to keep the 

equipment operating at its optimum performance. The maintenance has been kept to a minimum, and is 

fully described in the manual. 

In the unfortunate instance when the equipment does not perform as expected, may we recommend that 

you first study the fault finding information supplied. If this does not remedy the problem, then contact 

Starlight Xpress for further advice. Our message board service on the Starlight Xpress web site will 

often provide solutions to any problems. 

The equipment is covered by a 12-month guarantee covering faulty design, material or workmanship in 

addition to any statutory Consumer Rights of Purchasers. 

CONDITIONS OF GUARANTEE 

1) The equipment shall only be used for normal purposes described in the standard operating 

instructions, and within the relevant safety standards of the country where the equipment is used. 

2) Repairs under guarantee will be free of charge providing proof of purchase is produced, and that the 

equipment is returned to the Service Agent at the Purchaser’s expense and risk, and that the equipment 

proves to be defective. 

3) The guarantee shall not apply to equipment damaged by fire, accident, wear an tear, misuse, 

unauthorised repairs, or modified in any way whatsoever, or damage suffered in transit to or from the 

Purchaser. 

4) The Purchaser’s sole and exclusive rights under this guarantee is for repair, or at our discretion the 

replacement of the equipment or any part thereof, and no remedy to consequential loss or damage 

whatsoever. 

5) This guarantee shall not apply to components that have a naturally limited life. 

6) Starlight Xpress’s decision in all matters is final, and any faulty component which has been replaced 

will become the property of Starlight Xpress Ltd. 

For further info. or advice, please call: 

Mr Michael Hattey, 

Starlight Xpress Ltd., 

The Office, Foxley Green Farm, 

Ascot Road, Holyport, 

Berkshire, 

England. SL6 3LA 

Tel: 01628 777126 

Fax: 01628 580411 

e-mail: Michael.hattey@starlight-xpress.co.uk 

Web site: http://www.starlight-xpress.co.uk 

27

SXVF-H16 handbook.pdf - Starlight Xpress

Create successful ePaper yourself

Delete template?

Save as template?