Lodestar guider handbook - Starlight Xpress

Lodestar handbook Issue 1 September 2007Handbook for the SX ‘Lodestar’ guide cameraThank you for purchasing a Starlight Xpress ‘Lodestar’ guide camera. We hope that you will be verypleased with the performance of this product.The Lodestar is a very compact guider which is powered and operated via a single USB2.0 computerconnection. It also provides an opto-isolated output connection for direct control of most mounts, viatheir ‘Autoguider’ sockets. This output is compatible with the ‘ST4’ style of RJ12 connection andsupplies 4 ‘pull down’ direction lines and a common return. Alternatively, you may send the mountcontrol signals via a serial connection from the guider control computer.The Lodestar utilises a very sensitive Sony ‘ExView’ CCD (the ICX429AL) with an array of 752 x 580pixels in a ‘half-inch’ format. Although the chip is not cooled, it has a very low dark signal and verylittle readout noise, so it can be used to guide on faint stars that are beyond the reach of webcams andCMOS chip based guide cameras.The Lodestar specification:CCD - Sony ICX429AL ExView monochrome CCDPixel count - 752(H) x 580(V)Pixel size - 8.2 x 8.4uMBarrel size - 32mm dia. x 72mm long (1.25 inch eyepiece push fit size)Barrel thread - 25.4mm x 0.75mm ‘CS’ mount lens threadInput connection - ‘Mini B’ USB socket for USB2.0Output connection - 5 way JST ‘ZH’ style 1.5mm pitch plug to RJ12 autoguider plugOutput type - Opto-isolated 4 lines (N,S,E & W) pull down with common return lineDownload rate - Approx. 10 frames per second in binned 2x2 mode (recommended)

Lodestar handbook Issue 1 September 2007Installing the Lodestar:A new installation will require the driver files SXVIO.sys and Generic.sys, plus theSXVIO_Lodestar.inf file. If you run the ‘Setup.exe’ file on the supplied CD, it will install the driversand operating software automatically. If you are installing manually, copy these files into a convenientfolder on drive C and then connect the USB cable to the Lodestar. Point the installer at this folder whenit asks for the location of the drivers and you should see it set up the hardware as a ‘BlockIOClass’device in Device Manager.The Lodestar control software is Lodestar.exe and the latest version may be downloaded from theStarlight Xpress web site (http://www.starlight-xpress.co.uk), if necessary. Copy the exe file and dllsinto a folder on drive C and run the exe file to start the software. Alternatively, both ‘AstroArt’ and‘MaximDL’ support the Lodestar and may be preferred.Using the Lodestar:The Lodestar is generally used with a separate guide telescope, or via an off-axis guider. It is designedto be inserted into a standard 1.25” focuser assembly, but also has a 25mm ‘C’ type camera lens threadin the front to allow standard CCTV lenses to be attached. Please note that the chip to lens distance isonly 12.5mm and so a ‘CS’ to ‘C’ extension will be needed to permit a standard C lens to reach focus.Lenses designed for ‘CS’ mount cameras will focus without an extension tube, but many of these

Lodestar handbook Issue 1 September 2007lenses cannot fully illuminate a half-inch format CCD, so take care when selecting a lens for thispurpose.A typical set up might consist of an inexpensive 80mm F5 refractor ‘piggybacked’ onto an SCT, withthe Lodestar fitted directly into its focus barrel. Many such telescopes are designed to be used with aninverting prism ahead of the eyepiece and so the focuser may be too short when the Lodestar is inserteddirectly. In this case, an extension tube may often be made from a cheap Barlow lens assembly with thelens removed. This configuration can be seen in the picture below.The Lodestar attached to an 80mm F5 guide ‘scopeThe focal length of your guide telescope is not especially critical for good guiding, as the guidingsoftware searches for the ‘centroid’ of the guide star image and can resolve shifts of far less than 1pixel. Using a guide scope with a relatively short focal length (between 300 and 500mm) makes guidestar finding very easy and this is a recommended setup for general purpose guiding.

Lodestar handbook Issue 1 September 2007The control of your telescope mount will depend on what inputs are provided. The Lodestar outputconnector supplies 4 pull-down lines and a common return line to simulate an ‘ST4’ style autoguideroutput. The lines are isolated from the Lodestar electronics by opto-isolator chips and so there is norisk of damage when connecting the outputs to mounts with unprotected electronics. A standard ‘RJ12’style output lead is supplied with the Lodestar and this may be connected to any ST4 compatibleautoguider input socket on the mount. It is also possible to guide by using serial data from the computerto an RS232 input on the mount, but this will be covered later and is less effective than the directhardware connection.The preferred guiding mode is 2x2 binned, as this gives both fast downloads and high sensitivitywithout any ‘interlacing’ issues. The ‘Fast’ 2x1 mode is also useful if you are working with a shortfocal length guide ‘scope, as it offers somewhat finer RA guiding resolution in the X axis if this isoriented East-West.Guiding with the Starlight Xpress softwareWith the Lodestar connected to the PC and mount, open ‘Lodestar.exe’ and find the ‘Set programdefaults’ menu under the ‘File’ heading. If this is the first run of the software, you will get a warningabout the ‘ini file not found’, but ignore this and click on OK. You should now see a screen similar tothe one shown below:The settings shown above are generally satisfactory as a starting point, although some will probablyneed refinement for best results. In the example shown, the ‘autoguider socket’ on the Lodestar isproviding the control signals to the mount, but you might alternatively use the ‘LX200’ mode via theserial port of the computer, if this is preferred. The Guiding Parameters are set to 6 pixels per second,which corresponds to the typical drift rate of a 1000mm focal length guide telescope when the mount isguiding at 0.5x sidereal speed. Longer focal lengths and/or higher guiding rates will require a larger

Lodestar handbook Issue 1 September 2007value to be set so as to avoid excessively fast corrections, which can cause erratic guiding or evenoscillation of the guiding errors to either side of the guide star.Once the defaults have been set to values which you think will be approximately correct, save thesettings and open the ‘View’ menu. In this you will see an option called ‘Max palette stretch’. Openthis and check the ‘Activate stretch display’ check box. This will automatically boost the imagebrightness so that faint guide stars can be easily seen – if necessary, you can adjust the slider for thebest results.Now click on the camera icon to open the Lodestar control dialog, as below:The image box will be empty at this point, but we need a frame to select the guide star from, so use theguiding options to select a suitable exposure time (say 1 second) and press the ‘Start’ button below theimage box. A sequence of images will be shown and you can refine the image focus and centring asrequired. Before attempting to guide, it is wise to check that you have control of the telescope drive viathe Lodestar software. This is easily done by pressing the ‘Move Telescope’ buttons at the lower left ofthe control box. Check that pressing the arrow buttons causes the star field to drift left, right, up anddown, as appropriate. The LED at the back of the Lodestar should change colour when the buttons arepressed. If all is well, move onto the next step below:Once a good guide star has been found, press the ‘Stop’ button and then the ‘Select guide star’ button.You can now click the mouse arrow on the guide star and a green cross will appear, centred on the star(see above). Don’t select a very bright guide star, as this will result in poor guiding due to saturation ofthe core pixels in the star image. The example above shows the region around Vega and it is clear thatVega itself would make a very poor guide star due to its large saturated core.Once the guide star is selected, a small box appears with the star coordinates. If they look good, justclick on OK.Now click on ‘Start Guiding’:

Lodestar handbook Issue 1 September 2007After a brief delay, the Guiding Info window will open, as above, and you will see the guide star, alongwith error values and a reticule showing the guide star location with respect to the reference position. Ifall is well, you should see the guide star location being forced towards the centre position with eachsuccessive guide image. However, it is quite likely that it will be pushed away from the correctposition, due to an error in the guiding default settings. If this is the case, note the direction of travel,and then reverse the appropriate direction setting in the guiding defaults menu. For example, if the starmoves away to the left or right, try reversing the ‘Swap e/w direction’ setting. If guiding works, but issluggish, try reducing the ‘Rate’ setting in the guider settings, or increase it if the guiding oscillatesfrom one side of the guide star to the other.Lodestar maintenanceThe Lodestar head is designed for a long and reliable lifespan and needs very little maintenance to keepit in good working order. The only common issue is with dust particles which collect on the CCDwindow and can shade areas of the image field. These are best removed with a quick blast ofcompressed air from a ‘Dust off’ aerosol, or similar air blower. More permanent marks may beremoved with a drop of alcohol on a ‘microfibre’ lens cloth.

Lodestar handbook Issue 1 September 2007Dear User,Thank you for purchasing a Starlight Xpress CCD Imaging System. We are confident that you will gainmuch satisfaction from this equipment, but please read carefully the accompanying instruction manualto 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 theequipment operating at its optimum performance. The maintenance has been kept to a minimum, and isfully described in the manual.In the unfortunate instance when the equipment does not perform as expected, may we recommend thatyou first study the fault finding information supplied. If this does not remedy the problem, then contactStarlight Xpress for further advice. Our message board service on the Starlight Xpress web site willoften provide solutions to any problems.The equipment is covered by a 12-month guarantee covering faulty design, material or workmanship inaddition to any statutory Consumer Rights of Purchasers.CONDITIONS OF GUARANTEE1) The equipment shall only be used for normal purposes described in the standard operatinginstructions, 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 theequipment is returned to the Service Agent at the Purchaser’s expense and risk, and that the equipmentproves 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 thePurchaser.4) The Purchaser’s sole and exclusive rights under this guarantee is for repair, or at our discretion thereplacement of the equipment or any part thereof, and no remedy to consequential loss or damagewhatsoever.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 replacedwill 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 3LATel: 01628 777126Fax: 01628 580411e-mail: michael.hattey@starlight-xpress.co.ukWeb site: http://www.starlight-xpress.co.uk

Lodestar guider handbook - Starlight Xpress

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