Triangulum Galaxy

[StarzSkies]

Thanks Brian.
Yea, I've been creating my Darks to sync with the light frames since I started.
In last nights case my Darks were 70s exp and 110 gain to match what my lights were to be.
When I increased the gain to 120s due to the reject issue, I knew the darks were at that point probably not good.
I'll be creating a Darks library of likely scenarios I may be confronted with.
Thanks for the information.
Frank

[oopfan]

Gotcha. So light frames would not stack at 70s with 70-second darks? But when you increased the exposure to 120s, it started stacking almost all frames? How long did you wait for the image to build in LiveStack before stopping?

[oopfan]

Frank,

So it's best that you use the "The Brain" to sample the sky brightness and recommend an exposure. I've been basing your sky brightness on a light pollution map at astrospheric.com. Now there is a possible issue with the filter. I'm no longer confident with these estimates amid other mitigating factors. "The Brain" will ask you to point your scope at or near the object. It uses the sensor to actually measure the sky brightness. Use the Brain with the filter in place. Even if you revert to using the IR/Cut filter, use the Brain. It will give a better measure than any light pollution map can. Personally, I use a Sky Quality Meter to measure the sky, but it does the same thing as the Brain.

Brian

[StarzSkies]

Correct,
I increased the gain twice. First time to 90s and all were rejected.
I was ready to pack it up and decided to try 120s.
They started stacking at 120s and I stopped at 99 stacked frames.
You could see the galaxy forming but it never really got that punch. Stars looked good. Tracking was good.
I replayed the raw frames this morning in the folder monitor. Not very impressive.
Probably a couple of factors.
1. Filter not compatible with F4.
2. Increasing gain caused darks to be no good, but, it did tell me that my workflow was not the problem.
As I mentioned, focus looked good. I did not see any issues there.

The Brain. I've seen comments regarding that. Is it a live stack feature in SC?
If not, where is it if you don't mind. I'll take a look.

Frank

[nexusjeep]

With the ASI2600MC I have used darks of a different exposure to the lights without issue as there is absolutely no amp glow with that sensor and I do not find that the longer exposure introduces anymore hot or cold pixels when comparing 60s 120s 180s darks so if you do not have an exact dark using a different one as a quick fix should not be an issue in the live stacking.

Also I always shoot at gain 100 as that is the point when the noise drops, I only ever use a higher gain when polar aligning or running a focus script for all actual imaging light frames I just leave it at 100 and that is what all my masters are built on.

However, when I reprocess the raw frames through PixInsight I do then shoot a dark of the correct length to add to the master's library for future use if necessary.

I would not have thought F4 would cause a filter issue unless it is a particularly bad filter or a insanely tight tight band pass even at 3nm band pass I have never had an issue at F4.5 which is the fastest I can go if you have something like a RASA at F2 then yes you would need specific filters for that but I think anything F3.5 and above should not suffer Band shift.

I have used the brain function in the past but it generally gives me a sub 1 minute time (usually sub 10s)on the exposures and as I image the same target for 5 to 7 hours I usually opt for 3min - 5min times unless the object is incredibly bright but bear in mind I am generally using a multi band narrow band pass filter. If using the scope unfiltered the generally I never go over 90s. Otherwise, I have a massive number of subs to run through Pixinsight.

Cheers
Nick

[oopfan]

Frank,

I did a search on SpaceCat and found f/4.9. Is that not correct? Either way I'd recommend using The Brain. It will give you the most accurate reading. Use it the next time you go out. Only use the IR/Cut filter. It should say that the exposure is in the 5-second range, therefore it doesn't cost you much time to capture 30x 5-second darks right there on the spot before you start live-stacking. It's been a long while since I used the Brain so it's best that you read the documentation on its use.

Brian

[nexusjeep]

The other thing to check is if you have changed any of the setting in the alignement tab of live stacking as that could cause an issue if it is not detecting enough stars, Also I do not filter on brightness or FWHM as this has caused me to lose live stack frames.

Cheers
Nick

[StarzSkies]

Thanks Brian!
Thanks Nick!

Frank

[oopfan]

Nick,

Thanks for your input, but exposure really depends a lot on your light pollution. Frank is at Bortle 6.5 according to a map. If he had darker skies then a longer exposure would make sense. How are your skies?

Brian

[StarzSkies]

Nick,

I have not changed anything in the Alignment settings. They are all default.

Frank