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What are the best UHC filters?

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#26 thisismyusername

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Posted 03 April 2023 - 03:37 PM

The opposite.  Its bandwidth in the red is so much wider than its narrow bandwidth in the blue-green that it makes all the stars appear red.

The purpose of a nebula filter is to enhance the visibility of the nebula, not the stars, and it does that quite well.

Not everyone likes the red tinted stars, but I think you can forget about it when you see 3x as much nebula.

The narrowband filters with no red transmission make the stars appear blue-green, which is equally discolored, but for some reason no one finds that objectionable.

I see. But when you say I can see 3x as much nebula, are you comparing it to using no filter or another UHC filter?


Edited by thisismyusername, 03 April 2023 - 03:40 PM.


#27 davidgmd

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Posted 03 April 2023 - 04:50 PM

Don is our narrow-band baloney filter.

  
I bought the Astronomik “UHC” filter because it passes the far red/near infrared, in anticipation of eventually using it with a night vision device. It’s got high transmission for the H-β and both O-III lines, and is pretty narrow at around 25 nm FWHM. It’s a good all-around nebula filter - makes a real difference in my 4” and 8” scopes.



#28 Jim in PA

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Posted 03 April 2023 - 06:35 PM

DGM NPB filters are available new, now.

 

Don, should've asked when I had you on the phone:  Is there a chart anywhere that shows the DGM's wavelength response (kind of like what Baader publishes on theirs, a graph with RGB and IR UV wavelengths with percentage of passing/blocking)?  I looked on your website and didn't see any spectrum info (but I might've missed it).  Thanks, Jim



#29 Starman1

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Posted 03 April 2023 - 06:39 PM

I see. But when you say I can see 3x as much nebula, are you comparing it to using no filter or another UHC filter?

Comparing it with no filter.

The DGM is comparable to other good filters on most nebulae, but has given me superb views of the large H-II star forming regions (M8/M20/M17,M16 for example).



#30 Starman1

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Posted 03 April 2023 - 06:44 PM

Don, should've asked when I had you on the phone:  Is there a chart anywhere that shows the DGM's wavelength response (kind of like what Baader publishes on theirs, a graph with RGB and IR UV wavelengths with percentage of passing/blocking)?  I looked on your website and didn't see any spectrum info (but I might've missed it).  Thanks, Jim

Yes, there is.

I attach a sheet of the lab test on my own, and you can also see the graph here:

https://searchlight....9d-153d7e7c0eb8

And here is the lab test on mine:

Note: The wavelengths you are looking for are: 486.1nm (H-ß), 495.9nm and 500.7nm (O-III lines).

You may have to interpolate between wavelengths.

You can see from the graphs that two different filters are virtually identical, so they are very consistent.

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#31 Jim in PA

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Posted 03 April 2023 - 06:59 PM

Yes, there is.

I attach a sheet of the lab test on my own, and you can also see the graph here:

https://searchlight....9d-153d7e7c0eb8

And here is the lab test on mine:

Note: The wavelengths you are looking for are: 486.1nm (H-ß), 495.9nm and 500.7nm (O-III lines).

You may have to interpolate between wavelengths.

You can see from the graphs that two different filters are virtually identical, so they are very consistent.

 

Thanks, exactly what I was looking for and more, many MANY thanks for the Searchlight data, VERY Handy!  Now to pour over my spring DSO list and pick which filters to use on which targets ;)




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