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Old 24-01-2018, 06:37 PM
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luka
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Comparison of guidecams

I just tested my new ASI290MM mini guidecam and was "shocked" to see how good the sensitivity was. Where previously I had to move the finderguider around until I found a star now I have a choice of usually over 20 stars in any direction of the sky.

I thought it would be interesting to compare the 4 (guide)cams that I have here. I know that the comparison is not fair but still it is good to see how the technology improved over time. The image shows:
1. SPC900NC webcam
2. Long exposure modified SPC900NC webcam
3. ASI120MC (90% gain)
4. ASI290MM mini (only 50% gain)

As I said the comparison is not fair in any way and I was not trying to be scientific. I also may have bumped the guidescope while swapping the cameras but the images are still representative of the sensitivity increase that I can see.

Very happy with my purchase

edit: fixed typos
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Last edited by luka; 24-01-2018 at 08:52 PM.
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Old 24-01-2018, 07:22 PM
kens (Ken)
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Do you mean ASI290MM mini? I’ve not heard of an ASI260
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Old 24-01-2018, 07:26 PM
glend (Glen)
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Consider the quantum efficency of the sensors, the ASI 120MC (75% QE), and the 290 mini ( 80%+), have very high QE numbers compared to the others, and gain is not that important imho. Note the mini detects far more stars than the 120MC, even at the low gain setting. The clear winner is the 290 mini.
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Old 24-01-2018, 08:51 PM
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Quote:
Originally Posted by kens View Post
Do you mean ASI290MM mini? Iíve not heard of an ASI260
My bad, it is ASI290MM mini. I will edit the original post.
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Old 24-01-2018, 09:31 PM
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Camelopardalis (Dunk)
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Nice one luka, the SNR of the 290 really is in a class apart, for now...
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Old 24-01-2018, 10:18 PM
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Quote:
Originally Posted by glend View Post
Consider the quantum efficency of the sensors, the ASI 120MC (75% QE), and the 290 mini ( 80%+), have very high QE numbers compared to the others, and gain is not that important imho. Note the mini detects far more stars than the 120MC, even at the low gain setting. The clear winner is the 290 mini.
Absolutely. Increasing the gain did not seem to improve things much with the 290 mini or 120MC. I still have to confirm but I have a feeling that with the 290 mini the stars in PHD2 got brighter and bigger with the higher gain and hence saturated, i.e. unusable for guiding.

Also, one of the reasons I said the comparison was not fair is that 290 mini has a mono sensor while the other ones have a Bayer filter which will reduce the efficiency. A better comparison would have been ASI120MM vs 290MM mini and the mono mods of the SPC900NC.

Another interesting thing was how much the good old SPC900NC improved with the long exposure mod. Without it the exposure is limited to about 60ms and the software has to add images to achieve longer exposures. Of course the read noise gets added as well and the effect of this is quite significant, as shown in the top two images.

I forgot to mention, those were all 2 second exposures.
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