narrowband exposure times

[Wirral man]

Hi all had a go at narrowband this weekend but what would be a ideal exposure time i have the zwo narrowband filter set ha7 oll sll i took 300sec subs on the asi1600mm set at unity gain i got some detail from the ha but nothing on the other two the subject was ngc7000.

do the olll and sll need longer exposure or just more subs?

[drjolo]

Basing on my experience with QHY163M (the same sensor) camera with telescope f/7.5 300s sub is ok, but its better to increase gain to unity gain. I wrote more at my blog https://astrojolo.com/gears/cmos-gain-settings-part-ii/ . Side effect is that for each gain setting you need new dark frames. Also more subs will definitely help. 

[kens]

With narrowband I generally image at gain 200 with the ASI1600. As always, aim to bury the read noise so expose to an ADU value in the range of 1000 to 1500. There is quite a difference between filters (depending on sky background)  but I like to keep things simple so I use the same exposure on all three filters - whatever gets the lowest response over 1000 and preferably  matches my darks library. I also allow for some reduction in the sky background over the night as the sun sets and people turn off their lights.

Typical exposures range from 180s to 300s under light pollution at F/5.5. You'll need experiment under your own skies.

[whipdry]

Visually these my help on what to expect... QHYImg2Pro & SXVh9 same sensor Ha7 & SII 8nm Baader filters both 900sec.

 

Peter

[Wirral man]

18 minutes ago, kens said:

With narrowband I generally image at gain 200 with the ASI1600. As always, aim to bury the read noise so expose to an ADU value in the range of 1000 to 1500. There is quite a difference between filters (depending on sky background)  but I like to keep things simple so I use the same exposure on all three filters - whatever gets the lowest response over 1000 and preferably  matches my darks library. I also allow for some reduction in the sky background over the night as the sun sets and people turn off their lights.

Typical exposures range from 180s to 300s under light pollution at F/5.5. You'll need experiment under your own skies.

with 200 gain what do set your offset to ?

[kens]

I always use offset 50 at all gains. I like to keep things simple.

[Wirral man]

2 hours ago, kens said:

I always use offset 50 at all gains. I like to keep things simple.

yes thanks i like simple