C/2022 E3 ZTF - ASI678MC - Not getting color

[Nittany]

I tried:
1) Different exposure lengths
2) Different gain settings
3) I moved all sliders up and down
4) i also had to change Stars filter size to get the window on the comet so it was detecting it right
5) I updated ZWO ASI camera drivers as well
6) 17 mins exposure for below picture.
7) Celestron Edge HD8, 0.7x reducer, 108mm backfocus (need to be at 105mm).

Still no color....

[oopfan]

My two cents:

I'm looking at ZWO's website for your camera:
https://astronomy-imaging-camera.com/product/asi678mc

At Gain 275 your Full Well Depth (FWD) is only about 400 electrons (e-). Seeing that always concerns me. Decrease the Gain to 175. Your FWD will grow to 2000e-. Sure, your Read Noise will increase from 0.8e- to 1.6e- but that is insignificant for your use case.

Brian

[Nittany]

Thanks Brian. I will try that tomorrow. I am also going to try the 4.0 version (Recommendation from another friend) for couple mins tops as it does not have the "Align on Comet" feature. Lets see.

[oopfan]

I just had a close look at your planetary shots. Nice work, however, notice how Saturn is virtually devoid of color except for a tinge of blue? You used Gain of 285 for Saturn and Gain of 275 for the comet. The only color I see in your comet field-of-view (FOV) is a slightly blue star. Also notice that when you lowered the Gain for Jupiter and Mars that colors became more vivid. I think you are onto something there!

Brian

[admin]

Hi,

just to confirm that as long as you have the latest SharpCap 4 (or 4.1) version, then it should support the ASI678. Support for that camera has been in versions of SharpCap released since about the end of July 2022.

cheers,

Robin

[Nittany]

Thanks Robin for confirmation.

Brian - I tried taking the Gain lower to 175, but it wouldnt stack. It kept giving me message " Could not align". It was bit cloudy today so i think it needed a higher setting. I will try again tomorrow. However, when i had 175 gain setting, i still did not get the green color. There is something else in play here. (I am sure it is my error - just does not know what that is).

Thanks

[oopfan]

Just curious are you using a light pollution filter?

I don't have any experience using LP filters in astrophotography, but back when I was a lad with a regular camera and photographic emulsion, using daylight balanced film for indoor photography was not recommended especially in the presence of fluorescent lights. My photos would come out green. So if you are using an LP filter then it is significantly attenuating the green.

Brian

[Nittany]

I am not using any light pollution filter.

0.7x reducer-->adapter (96mm) --> ASI678MC (12.5mm backfocus)

[oopfan]

You mentioned that you primarily practice planetary photography so I can understand why you did not capture Dark calibration frames. Deep-Sky astrophotography is a different beast. The faint glow of green cometary coma is similar in brightness to your sky's light pollution. To properly image it you need to capture Dark frames and ask SharpCap to subtract Darks from your Light frames before stacking. I see that you aren't doing that.

As for the other problem with LiveStack not detecting enough stars when using a lower gain, this is an unfortunate consequence of trying to use a planetary telescope for deep-sky. Your FOV is very narrow: 0.31 x 0.17 degrees from what I can figure. You need a larger sensor, however, that costs money.

First try capturing Darks: Cover your aperture and take 30-50 frames at 5 seconds exposure. SharpCap has a workflow for capturing Darks. SharpCap should automatically use it on your next LiveStack session. Then try the comet again, this time with Dark subtraction. Hopefully you will see an improvement.

If that yields unsatisfactory results, then lower the Gain and increase the exposure to 10 seconds. Capture a new round of Darks, then LiveStack the comet. The increased exposure will make more stars available.

Brian

[Nittany]

Yeah - i am new to the overall astrophotography. I was doing planetary for first 2 months and now trying to get a handle on deep sky. So thought i should start off with this comet with the new feature of Align on Comet and Save as Seen. I will be happy if i get the green color with star trails for now before i get into more detailed Deep Sky photography. Also understand using a long FL for DSO is not so good choice.

I think live stacking not detecting enough stars, what happened yesterday was definitely a result of lower exposure and lowering gain. Today i will get that corrected - overall as i said for now, i want to get the green color and then go into sequence you are taking about below.