Suggestions for imaging, targets and time

[Doberamus]

A couple of questions about choosing targets:

Is there any handy rule of thumb, or guide, about how long you should image a given nebula for, to start getting a decent image? 

And, similarly,  is there anywhere you might find a list of "gettable" targets for a given night?

Thanks!

[Marvin Jenkins]

Stellarium is a great free tool. I find that planning a session with it very helpful.

I found at the beginning (still there to some degree) choosing targets that are circumpolar like M81/M82 is a good thing as they visible all night, so are less critical for position.

As for how long to image nebula, longer the better, I am sure someone who knows way more than I will be along soon.

Marv

[vlaiv]

Determining needed time for target is way too complex topic to explain in couple of sentences.

It depends on target brightness, shooting conditions (sky transparency, light pollution levels, position of the target in the sky, ...), gear used (sampling resolution, telescope aperture and light throughput, camera quantum efficiency, filters used ...) to name few

Even if you know all these parameters and know how to model all the (and yes, you can do that in say spreadsheet - or there have even been online calculators) - you don't know target brightness until you record it or until someone else does and publish the data (even then - there is no single value for targets - spiral arms are much fainter than galaxy core for example - you need to look at brightness of faintest area you want to record).

Best thing to do is to get the feel for your location and gear. Start with objects people shoot most often - as these are easiest to shoot. Shoot those that are in "season" - or high up in the sky at the time you shoot in the night (I usually aim for target to cross meridian at midnight or 1am)

Lookup surface brightness of the target in Stellarium - and based on that figure out how much time you'll need.

Say you are happy with 4h of exposure on a target like M81 and want to know for some other target what is good time?

Best indicator is surface brightness of the target. Is your new target also around mag22? In all likelihood - 4h will be enough for it as well.

Is it maybe mag23 perhaps? In that case - be prepared to spend two nights on it. Start with single night and then you'll get to see the result - if you are not happy - well, then you need to spend more time on the target.

That is in general very good rule - do spend some time on the target and don't be afraid to go out again and spend some time more on it (if weather and commitments allow of course).

 

[MARS1960]

15 hours ago, Doberamus said:

A couple of questions about choosing targets:

Is there any handy rule of thumb, or guide, about how long you should image a given nebula for, to start getting a decent image? 

And, similarly,  is there anywhere you might find a list of "gettable" targets for a given night?

Thanks!

I use this site to find my targets, it's very customizable too.

https://telescopius.com

[The Lazy Astronomer]

I've recently started using this website: https://snrcalc.vercel.app/calculators

Input your info, and it'll give you either (depending on which option you select) the total SNR of the final stack for a given integration time, or the total integration time required for a given SNR.

As vlaiv says, there are a lot of variables, so take it as more of an indication, rather than an accurate figure.

Also, the tool was designed to give figures for a mono camera shooting luminance, but again, it should be ale to give you a general indication of the total time needed of you're using a OSC.

[rnobleeddy]

In terms of what to shoot, a +1 for https://telescopius.com. 

In terms of how long, all the other advice is good - I'd simply add that when I was starting out I was a little eager to explore more of the sky, so ended up with too little data on too many targets. More generally, I don't think I've ever regretted spending more time on a single target. It's diminishing returns, but it's never wasted!

[Doberamus]

Those are great recommendations, thanks!

[Marvin Jenkins]

I couldn’t agree more with advice given, especially getting out and imaging multiple nights on the same object if possible. 
Most of us have jobs and family commitments so all night long sessions are normally out of the question.

I for one found my limiting factor being the cold weather 2 hr limit of my camera battery. As #rnobeleddy said, I was too eager as well so I would move onto another target instead of backing it up with more nights.

On the other hand, sometimes the weather was so bad there was simply no chance to get anymore data. The target simply became unviable due to time lost, hence my suggestion of circumpolar targets at first. At least if the skies are clear you know they are there.

Marvin