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Narrow band imaging with ASA 10N

narrow band filter

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#1 chlopak

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Posted 20 May 2013 - 12:33 PM

Hello,

 

I have an ASA 10N and I want to go for narrow band imaging.

Since my telescope works in a very light polluted area I want to take the filters as narrow as possible, e.g. Astrodon 3nm.

 

However I know that filters can be too narrow, especially when playing together with fast optical systems like f/3.6 or even f/2.8.

 

Which filters do you use and what are your experiences and recommendations ?

 

Regards,

Ralph

 



#2 Konihlav

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Posted 20 May 2013 - 12:42 PM

Hi Ralph,

 

here is the answer (I hope):

http://blog.astrofot...avelpech/?p=207

and

http://blog.astrofot...avelpech/?p=299

 

personally, I own only one 5nm filter now as I already sold all other 5nm filters I ever had due to an upgrade for 3nm set :) I would always recommend 3nm OIII, 3nm SII and based on your budget decide between 3nm or 5nm Ha (I own both 3nm Ha and 5nm Ha as the 5nm one also covers the NII line found in few planetary nebulas).

 

do not worry about mixing different bandwidths (unless the difference is too big like 35nm and 5nm filter) it's all question of post processing where you can do wonders (if some filter produces bigger stars then the other one, you can deal with everything in Photoshop).

 

For NB imaging I own a CCD camera with ultra low readout noise.

For HaLRGB imaging I own a large format low sensitivity high noise camera because LRGB imaging is far different from NB.

 

hope this helps

Pavel

 

BTW the fastest system I use is F/3.6. For F/2.8 I would think of 5nm filters for "safety" (Ha and SII, keeping the OIII at 3nm) :)


Edited by Konihlav, 20 May 2013 - 12:56 PM.


#3 mattssporre

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Posted 21 May 2013 - 08:00 AM

Ralph,

 

I use an N10 with Astrodon filters (5nm for Ha and SII and 3nm for OIII). It was a big improvement in contrast going from 5nm OIII to 3nm OIII.

 

Here are some links to my images. At the bottom you find the stacked Ha, SII, OIII - just stretched to have a similar lightness.

 

I have detected no issues with the OIII 3nm and would go for 3nm for Ha and SII as well sometime in the future.

 

http://istarion.net/...an Nebula.shtml

 

http://istarion.net/...s/NGC7822.shtml

 

Pavel: Nice write-up:-)

 

BR
Matts



#4 chlopak

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Posted 21 May 2013 - 08:50 PM

Hi Pavel and Matts,

 

thanks for your answers, sounds good so far.

 

@Matts: I assume you are working with f/3.6, too. Have you compared lights with OIII 5nm and 3nm filters? Are differences in vignetting? Very nice pictures, btw ;-)

 

Regards,

Ralph



#5 mattssporre

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Posted 22 May 2013 - 07:54 PM

Ralph,

Yes, I am working at f3.6. I have not made a comparision of 3nm and 5nm, at least not a "scientific" one.

I had a Baader 5nm OIII and had a lot of issues with large halos around bright stars. In addition sky glow was comming thru the filter. Switching to Astrodon 3nm solved both issues and gave better contrast.

After I made the change I have understood that the Baader filter is sensitive to which side you point to the sky (they might have chamged that now). Since I already had the 3nm and it worked I never bothered to check.

BR
Matts




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