When to move on?

[MattJenko]

Hi All,

This is a question which has only really come to mind since I moved to mono CCD imaging and it involves completion. Below is 6 x 20 mins of Oiii data on the Crescent nebula in Cygnus. I have seen some amazing examples of this target, and my question is how much data can I realistically get from fainter objects like this in narrowband with an F6.4 system (ED80 + reducer). I know stacking benefits tail off significantly over 25/30 subs and 'most' of the noise will be gone by 20, so while I need more subs (I messed up at least half the moon filled semi darkness whilst gathering this ), do I need to increase sub length which may be a bit of an ask on my HEQ5, or do I just suck it up, get some more data for this filter and just move on to Ha/Sii? In other words, when does one move on !!

Image has been calibrated, stacked, DBE-ed, basically stretched and some mild noise reduction applied for tidiness. Halos are non-optional and I have grown to simply accept them with this particular filter.

All opinions welcome

Thanks

Matt

[johnrt]

20 mins should suffice, shoot as many subs as you can stand, the law of diminishing returns will stat to hurt you after 20/30 subs though. I would set out in narrowband to shoot a minimum of 20 subs and look at the results from there. Often targets with lots of dark nebula areas need more data, the dark patches eat up exposure time. One thing for sure is that there is no substitute for data, no amount of post processing will ever get you close to the results you'd get by going out and shooting double the number of subs.