New project duration advice

[MattJenko]

I have been setting up a WO FLT110 as an imaging rig for my local society and this week got everything working but given the full moon I put my Atik 414ex on it with an Ha filter and had a go at C31, just to see what would happen. I managed 3 hours worth of 20 mins subs. The results were way better than I hoped, so I am now well and truly hooked on taking this further. The best narrowband images I have seen all have some pretty significant integration times, and my question is about that. In the image below, there are some pretty low SNR areas, and I was wondering just how long I will need to get the kind of SNR that is in the higher signal areas, if this is even going to be possible? Also, do people have a duration in mind when they start, or do you just keep going until you are satisfied?

This is not my scope, so I need to plan imaging around its other uses, so having a rough idea on the kind of duration I will need it for will help me get this done. My current thoughts are at a minimum:

9 x 20 mins more Ha to double it to 6 hours.

12 x 20 mins Oiii

12 x 20 mins Sii.

This is going to mean quite a few sessions for me, as my usable sub:taken sub ratio is not exactly 100% 

Any advice welcome.

Cheers

Matt

[FunkyKoval35]

All you need is more Ha data. 25 - 30 exposures maybe? Or more? OIII and SII will give you color only, so 12 exposures should be fine.

[MattJenko]

I managed to gather whole host of additional Ha subs last night, but am thinking that I will need some pretty strong Oiii/Sii signal to match up with the Ha rather than just gather a bit to colour tone my image, so am looking at pretty long durations for those channels as well. I am not planning on using Ha as Lum, as I believe this gives a false hue to whatever channel I associate Ha with and skews the image, so I am resigning myself to some serious Oiii + Sii sessions when the moon slips past this target in the coming days.

I will process the new Ha and see what difference it makes to the outer regions and then make a call on whether I have enough, or if I want to keep going until Christmas

Thanks

[ChrisLX200]

10-12 decent 20min Ha subs should give you pretty good s/n on an object like that, but if there is a Moon about (>25%) then the fainter stuff will get washed out - and it won't matter how many extra you take. For OIII and SII it's wise to use longer subs - as long as you can comfortably work with. I use 30min and would go longer if I could, and the OIII really should be done when there is no Moon about at all (and transparency is good).

ChrisH

[MattJenko]

Thanks Chris. I will see how my additional Ha shots during a full moon impact, but from what you say, Ha imaging is not a 100% moon-dodger, just the best that can be done, in which case, I may have to back load all my imaging when the moon is away!

[andrewluck]

All things being equal, then doubling the number of exposures will result in the noise reducing by about 1.4 (square root of 2).

Andrew

[MattJenko]

Hi Andrew. That 1.4 figure sounds about right. I managed to add 11 more 20 min subs on Wednesday to the previous 9 and things are starting to come together. They are still shot during a fullish moon and the moon is also in this part of the sky, so as Chris mentioned, not going to get amazing faint detail until it is further away it seems: