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Filter advice / recommendation

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#1 Ken_nneth

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Posted 20 March 2019 - 12:42 AM

With galaxy season starting I was wondering if there are any filters that would help me get around the light pollution (red zone) I have from my back yard.

I am imaging with an Edge 8” with reducer, ASI1600 mono, ZWO filter wheel with Baader LRGB filters.

I have the possibility of placing a 2” filter in my imaging train, but will any filter really help? I have been trying to find information on the subject but most of what I have found concerns filters for OSC.

I need some advice before I spend money on something that does not help. Any recommendations?

Kenneth



#2 mistateo

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Posted 20 March 2019 - 02:39 AM

Unfortunately the filter really won't help your situation much.  The RGB filters are already designed to try and cut out certain sources of light pollution.  You could TRY using a 1.25" light pollution filter in your filter wheel instead of the L filter, but they don't work all that well for galaxies.  The best thing you could do is get to a darker location.  If that isn't feasible, you just need A LOT more integration time.  Now for certain types of nebulae, that light pollution filter instead of the luminance filter can do some pretty nice things.


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#3 ngc7319_20

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Posted 20 March 2019 - 04:14 AM

There are some reports of light pollution filters being useful on galaxies, though mostly OSC cameras.  I don't see why you couldn't stack the light pollution filter with your color filters (unless perhaps some filter reflection problem results). Probably you would need to do some non-standard weighting when combining the colors in post-processing.  

 

https://www.cloudyni...e-and-galaxies/

http://www.astropix....cls_filter.html

http://www.hrastro.c...galaxy-group/\\

 

I expect the benefit will depend on the source of your light pollution -- Sodium and Mercury vapor lights have spectral lines which can be filtered.  But incandescent or LED lights are mostly continuum and filters won't help there -- they will filter out the galaxy and pollution by similar amounts.

 

Hopefully someone with hands-on experience can respond.


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#4 bobzeq25

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Posted 20 March 2019 - 09:40 AM

With galaxy season starting I was wondering if there are any filters that would help me get around the light pollution (red zone) I have from my back yard.

I am imaging with an Edge 8” with reducer, ASI1600 mono, ZWO filter wheel with Baader LRGB filters.

I have the possibility of placing a 2” filter in my imaging train, but will any filter really help? I have been trying to find information on the subject but most of what I have found concerns filters for OSC.

I need some advice before I spend money on something that does not help. Any recommendations?

Kenneth

I too image from a Red Zone.  Recommendation, which is the same for OSC or mono plus filters.  Forget LP filters for galaxies.  They work by ripping out chunks of the spectrum.  That can work some on emission nebulae, which emit mostly in specific areas of the spectrum.  For galaxies, you lose too much data.

 

You are doing gradient reduction in processing?  That's effective because it identifies light pollution by spatial variation, not spectrum.   It works on all targets, all sources of light pollution. 

 

Bottom line.  Pretty much all serious imagers use gradient reduction, some will add a LP filter, some won't.  Some will add one only for emission nebulae.

 

I pretty much don't, on anything.  I am experimenting with a very mild neodymium filter as an L filter, does a bit of good on emission nebula (not galaxies), doesn't remove much data.


Edited by bobzeq25, 20 March 2019 - 09:48 AM.

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#5 Ken_nneth

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Posted 21 March 2019 - 02:04 AM

Thanks all, think I’ll save my money for something else.

all I have to do is find the best gain/offset/exposure combination to get a good amount of signal.

Does anyone have any suggestions?
Kenneth




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