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Acquiring mono RGB data over the city

richorn
06 Aug, 2019 23:23
Total newbie here.  I have a mono camera and a filter wheel.  First light was an underexposed OIII stack of M 16, 3 days ago.  Well, first light was actually 90 minutes of Ha  the day before, but so out of focus to be useless!  ooops.

I have the advantage of shooting over the ocean (to the south) for most of my targets, so the city isn't an issue.

I put shooting the Veil on my to-do list..  I was thinking Ha, OIII, and then an RGB set for the stars.  Is there a trick to getting the stars when shooting over the light polluted city?

I know the NB filters are ok, but how does one deal with 100nm wide filters over Los Angeles??  I do not have a light pollution filter so I assume I need a trick to get the SNR way up.
carastro
09 Aug, 2019 09:28
I live in the suburbs of London, and find LP a real pain.  However I have achieved a fair bit with narrowband and in the early days with a DSLR, mainly the brighter targets.  I tried last year to add RGB stars to NB images, and it does seem to work OK.

I made up a personal website of images I have achieved for Bortle 8, this may give you some idea:
https://sites.google.com/view/carastroimaging/home

Plus I don't have an ocean to the south of me.  Only more town and LP.

Re LP filter, of course you could get one, I have one but I often forget to use it and I don't think a LP filter was used on all the Mono shots on the website above.

Hope this helps

Carole
Edited 09 Aug, 2019 09:32
bobzeq25
11 Aug, 2019 18:53
My "trick" (used by almost all serious imagers) is gradient reduction in processing.  It's surprisingly effective.  Example.  RGB data.  No other processing besides a simple stretch, necessary so you can see the linear data.

https://astrob.in/420460/0/

https://www.astrobin.com/420461/?nc=user

Red Zone, Bortle 7, mag per arc sec squared low 18s.  You do need to do the total imaging time, this was 164X30" at F4.8.

Final image with H alpha added, giving the acquisition details.

https://www.astrobin.com/384117/G/?nc=user
Edited 11 Aug, 2019 19:04
 
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