Should I use CLS-CCD for Galaxies in Bortle 4 Skies?!

[Anthony RS]

Hello,

I've modified my Canon 500D (t1i) following Garry Honis' video; however, I did not replace the IR cut filter with a clear glass filter. I just removed the IR filter and put back together all the other filters. I'm using a Newt. with the Skywatcher Aplanatic coma corrector.

Here's my issue, I already have the Astronomik CLS-CCD filter which is a light pollution filter as well as an IR blocking filter but I will be shooting M81/82 in bortle 4 skies this weekend so I'm not sure if using the CLS-CCD is a good idea. First, I'm in relatively dark skies with low light pollution, second, I'm shooting a galaxy, which as far as I know, and please correct me if I'm wrong, the CLS-CCD will do more harm then good blocking probably some of the details or requiring much longer exposures to get the same details as without the filter. I could remove the filter since i'm not worried about light pollution, but would that cause bloated stars since I'm using a coma corrector? or are the remaining filters in the DSLR enough to block IR?

If removing the CLS-CCD does mean I'm going to get bloated stars, the question is can I remove the filter to get as much detail as possible from the galaxies and deal with the stars in processing, or is keeping the filter not that detrimental to galaxies?

Appreciate any insights and opinions especially if you have any experience with this.

Cheers,

Anthony 

[wimvb]

I moved to a Bortle 4 place, and haven't used my light pollution filter since. I do suffer from Stockholms light dome about 30 km to the south, but that only affects objects that are low in the sky.

[Anthony RS]

1 minute ago, wimvb said:

I moved to a Bortle 4 place, and haven't used my light pollution filter since. I do suffer from Stockholms light dome about 30 km to the south, but that only affects objects that are low in the sky.

is you DSLR modded without removing LPF#1 filter? If yes, are you seeing some star bloat?

 

Thanks

[wimvb]

I use a mono cooled cmos camera. You may need to adjust the exposure time, because the absence of a filter means that you collect more star light. Just don't expect the histogram to be as far to the middle/right as you are used to. The skies will be a lot darker, but the brightest stars are about the same. Because of the darker skies, you'll experience more contrast and see more faint stars. In general, your total integration time needs to be less.

[Adam J]

1 hour ago, Anthony RS said:

Hello,

I've modified my Canon 500D (t1i) following Garry Honis' video; however, I did not replace the IR cut filter with a clear glass filter. I just removed the IR filter and put back together all the other filters. I'm using a Newt. with the Skywatcher Aplanatic coma corrector.

Here's my issue, I already have the Astronomik CLS-CCD filter which is a light pollution filter as well as an IR blocking filter but I will be shooting M81/82 in bortle 4 skies this weekend so I'm not sure if using the CLS-CCD is a good idea. First, I'm in relatively dark skies with low light pollution, second, I'm shooting a galaxy, which as far as I know, and please correct me if I'm wrong, the CLS-CCD will do more harm then good blocking probably some of the details or requiring much longer exposures to get the same details as without the filter. I could remove the filter since i'm not worried about light pollution, but would that cause bloated stars since I'm using a coma corrector? or are the remaining filters in the DSLR enough to block IR?

If removing the CLS-CCD does mean I'm going to get bloated stars, the question is can I remove the filter to get as much detail as possible from the galaxies and deal with the stars in processing, or is keeping the filter not that detrimental to galaxies?

Appreciate any insights and opinions especially if you have any experience with this.

Cheers,

Anthony 

I would have thought that the problems that you are introducing with colour balance would not be worth any gains from using a LP filter in those sky conditions. 

Edited May 2, 2019 by Adam J

[Anthony RS]

1 minute ago, Adam J said:

I would have thought that the problems that you are introducing with colour balance would not be worth any gains from using a LP filter in those sky conditions. 

I understand that but my worries is star bloating since the CLS-CCD is also a UV/IR Cut filter. My camera still has LPF#1 but I'm not sure it's enough.

[Adam J]

3 minutes ago, Anthony RS said:

I understand that but my worries is star bloating since the CLS-CCD is also a UV/IR Cut filter. My camera still has LPF#1 but I'm not sure it's enough.

You wont see any star bloat from just the coma corrector on a Newtonian. The LPF#1 does cut UV and IR to an extent anyway. I think you will be fine I would be more worried if you were using a refractor.   

Edited May 2, 2019 by Adam J