Planetary cams compared: DFK vs. IMG

[lukebl]

Hi all,

I've had a quick go this evening at comparing the performance of my two planetary cameras, the DFK 21AU618.AS and the QHY IMG132e.

I originally got the IMG as I was seduced by its smaller pixels which I thought would give a sharper result, but then bought the DFK as that seems to be the planetary imager of choice. The IMG doesn't seems to be used that often, and not highly regarded, perhaps as it is just a 'humble' CMOS sensor. However, I'm increasingly of the opinion that the IMG might actually outperform the DFK. Shock horror. I know my telescope setup isn't best suited to planetary imaging, so this is hardly a proper test, but these images show that the IMG compares well. These are the actual comparative sizes of the images stacked in Registax, and the smaller pixels of the IMG seem to result in a larger and more resolved image.

These are just some captures hastily processed this evening, each of around 2500 frames stacked in Registax. I think the colour is definitely better in the DFK, but the IMG images seem to show more detail. Anyway, I'm sure that the experts will argue that small pixels mean nothing, but I'm thinking that the IMG is quite good for the money.

Enlargement:

[michael.h.f.wilkinson]

Interesting comparison. I do wonder what happens when the pixel size is matched to the seeing disk, or, put differently, when the size of Jupiter is identical in terms of pixels, rather than in mm (as is the case here, where the same barlow is used in either case). For both my ASI130MM and my SPC900, the optimal F-ratio is somewhere between 20 and 25. (5.3 and 5.6 micron pixels). Moving to the ASI120MM with its 3.75 micron pixels, I would have to use something like F/14-F/18 for the same image scale in pixels.

[Cath]

Very good luke. It's nice to see direct comparisons like this, thank you!

What the 'majority' tend to go for doesn't always mean it's the best, people tend to herd like sheep, for better or worst.

Me being me I tend to go in the opposiite direction, I'm not a follower (no desire to lead either), but that's another story.

But anyway, it's interesting to see what effect the 2* drizzle has had on the image too. I wouldn't say it's beneficial looking at those images, which I'm surprised at. Drizzle/Super resolution is suppose to help extract detail, not fuzz it out.

[lukebl]

I would guess that the greater sensitivity of the DFK would benefit longer focal lengths, or fainter objects like Saturn. Not having access to a 14" SCT, I'll have a try with stacked barlows to get a bigger image size next attempt.

[michael.h.f.wilkinson]

I have found that 1.5x drizzle in AS!2 followed by downscaling can help a bit