Kevin_A I am going to try mine on my new Esprit when it arrives soon!

The nice thing about buying a Takahashi is you don't have to constantly "upgrade" the OTA :-). Saves money on the long run. I have yet to find any new 60-90mm scope that makes me want to open up my wallet. One of them needs to produce a chromatic spot diagram close to that from the Baby-Q (Askars are about twice the spot size, although the V series looks better).

If I could take the weight, I would get the real FSQ-106; but as it is, I can barely carry that scope without camera and filters, and that is too much of a hassle. I have set everything up so I can just plop my scoe on the mount and not even do a polar alignment.

Chen

Kevin_A I

1/2 hour before leaving astronomical twilight; same settings as above. I guess the previous image included a lot of sky backgroud. This one looks more promising (M51 vs sky). The dark vignette is one of my antenna masts. Once it clears and I leave twilight, I can try some autorun in ASIAIR after refocusing.

Chen

Kevin_A Idid my first light at unity gain and may drop down to gain 150 but I do not like dropping too much below Unity… here is just slightly less than 3 hours of 180s subs at Unity… better than my 183 for sure.

Clouds came in just a few minutes after I started an autorun. 1 hour later, my all-sky camera shows this :-)

(Hey, night time sky is also blue. Just so dark that you think it is black :-). You can see the dipper on the bottom left. North is to the left.) Daytime is about -11.7 EV on this system (ASI294MC with a Samyang fisheye), the above image is at +8.5 EV. 20 f-stops difference.

Chen

Kevin_A

Hoo boy, this camera is sure noisy at unity gain (180 sec at 457mm-f/4.3). (Doesn't help with the Antlia RGB robbing me of the photons.)

Stable seeing tonight. This is what I got a little earlier in the ASIAIR autofocus routine:

Notice you can actually see a pretty clean Airy disc in the 3 second exposure. ASIAIR Auto focus actually works with this kind of plate scale (and very fast too, with such a small sensor). Temperature is also not changing too much; 0.7ºC in 90 minutes. But I will soon need to refocus the FSQ.

Autoguiding is pretty clean too.

Chen

Kevin_A using HGC increased the hot pixels substantially only so I do not find that would be good overall.

Back of the envelope... Dark current noise at -10ºC is about .002e-/sec, or 0.36e- with 180 sec exposure. At Unity gain, this (0.36e-) should be the actual (unity) contribution of random sensor noise, while the read noise is at a whopping 3.8e-.

With HCG, the RMS random noise is increased by a factor of 2 (HCG kicks in at a gain of about 5.4 dB above Unity Gain), so the 0.36e- dark current noise becomes 0.72e-, while read noise falls to about 1e- : the total noise (RMS) is now about 1.25e-. This should be better than the 3.8e- at Unity gain.

Perhaps I am missing something. If not, are we seeing mostly read noise at Unity Gain and 180 second exposure at -10ºC?

Also, if dark current is the problem, then -20ºC should help. But if read noise is the problem, that extra 10ºC cooling will do nothing.

Chen

Kevin_A Maybe you can test out 150, Unity and HCG and see what your thoughts are.

I just measured two sets of dark frames at -10ºC. One set is at Unity gain, and the second set is at HCG gain.

When I compare the HCG (at half the exposure time of the Unity gain, to equalize the exposure value) with Unity gain, the HCG definitely has lower standard deviation (a.k.a. RMS). Not by much, but definitely there.

The dark current noise is still very dominant -- i.e., you can see the noise rise with exposure time (read noise should be constant with exposure time -- one read per exposure).

This is just one noisy camera for long exposures.

From that result, I think I will try HCG tonight with 100 sec exposure. Also abandon the Antlia RGB and use the Baader Neodymium instead. Moon is going to be nasty -- with more than 60% illuminated (the neodymium might help a little).

The HCG gain also has slightly better dynamic range than gain 150.

I'm taking some -10ºC dark frames at gain 252 and exposure 100 seconds right now to prepare for tonight. I still don't have dark and bias for last night's Unity gain and 180 sec. So, can't process those yet.

Right now, I am not sure it is worth getting the smaller pixels vs using the ASI2600. I can always teleextend the FSQ-85 by 1.5x for the larger 2600 pixels -- slows it down to an f/8 though. I think the 585 is just a cheap cooled camera - better than nothing, but not competitive with the better sensors.

BTW, does it irritate you that the long edge of the sensor, relative to the USB connectors, is 90 degrees from the ASI2600 orientation. No adult supervision.

Chen

Kevin_A I think if I remember even 60s at HGC the hot pixels were plenty!

Yuk. Too noisy (albeit there is no bias, darks or flats here, just simple stacking):

This is what I got in 2022 with the ASI2600MM with just 50 subframes (180s HCG):

I think I give up on the ASI585 and try the color ASI2600MC tonight :-).

Chen