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Wratten 82A for DSO's?

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#1 starquake

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Posted 09 March 2011 - 06:26 AM

Hi, I've read somewhere some months ago, that someone was using Wratten 82A (light blue) color filter for observing galaxies. He wrote that it enhanced his view for some low contrast details, like galactic arms.

So the question is simple, did any of you ever tried color filters for deep-sky objects and if yes, what were the results?

Many thanks, Ferenc.

#2 Asbytec

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Posted 09 March 2011 - 07:06 AM

Interesting, but I can't imagine even trying it. It might pass the blue stars in the spiral arms while tending to block background light...maybe. So, maybe there is some improvement in contrast, provided you have the photons to spare. This filter blocks 27% of all light, even blue. A broadband or narrow band filter would be more efficient. If you wanna give it a try, report back. Maybe it works, who knows.

#3 David Knisely

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Posted 09 March 2011 - 01:28 PM

Hi, I've read somewhere some months ago, that someone was using Wratten 82A (light blue) color filter for observing galaxies. He wrote that it enhanced his view for some low contrast details, like galactic arms.

So the question is simple, did any of you ever tried color filters for deep-sky objects and if yes, what were the results?

Many thanks, Ferenc.


A pale blue filter might help a little in larger apertures, but I prefer just using a broad-band LPR filter like the Lumicon Deep-sky or Orion Skyglow. Their light transmission in the critical areas is a little higher than in many 82a equivalent dye filters, and they "notch-out" the common skyglow emission lines of Sodium and Oxygen while passing most of the rest of the visual spectrum. They will increase the contrast of some of the larger more diffuse galaxies, but only mildly. Indeed, I sometimes use my Lumicon Deep-sky as a light blue filter for viewing the Martian clouds and polar cap, and it works pretty well for that application. Sometimes increasing the magnification has a similar contrast boosting effect on galaxies, especially on the smaller objects that require more power in the first place. Clear skies to you.

#4 azure1961p

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Posted 09 March 2011 - 07:53 PM

It's an interesting notion but Ive never tried it though I have used wrattens on comets with questionable results, read; nil. I'm not sure why a W82 would work on galaxies... M45 perhaps? Interesting - first time Ive heard of wrattens for deepsky applications outside of comets dust/gas tails.

Pete

#5 JimK

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Posted 09 March 2011 - 10:27 PM

I believe that I also read of using a W82 (lt blu) on galaxies from a web page of Susan Carroll:

http://sciastro.net/...-use-of-filters

but I keep forgetting to try it for myself...

#6 Asbytec

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Posted 10 March 2011 - 02:58 AM

I'm not sure why a W82 would work on galaxies...


Blue stars in the spiral arms.

A quote from the URL Jim posted. "Quite pronounced?"

"Grins and Giggles: Try this one on bright galaxies, particularly face-on spirals. I accidentally left it in an eyepiece when I swung over to take a look at M51. The detail in the spiral arms was quite pronounced over what I was used to seeing. It took me some time to figure out why. I've tried it on a number of bright galaxies since then and it really does a great job in increasing the detail in galactic structure."

#7 starquake

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Posted 10 March 2011 - 02:59 AM

Dear all, thank you very much for your replies, I'll give it a try as soon as I can put my hands on a 82A filter.

JimK, thanks for the link, this is not the page I remembered to list this feature of the 82A, so this means that there are now at least 2 person out there who claim that this filter works for galaxies.

#8 David Knisely

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Posted 10 March 2011 - 01:49 PM

I'm not sure why a W82 would work on galaxies...


Blue stars in the spiral arms.

A quote from the URL Jim posted. "Quite pronounced?"

"Grins and Giggles: Try this one on bright galaxies, particularly face-on spirals. I accidentally left it in an eyepiece when I swung over to take a look at M51. The detail in the spiral arms was quite pronounced over what I was used to seeing. It took me some time to figure out why. I've tried it on a number of bright galaxies since then and it really does a great job in increasing the detail in galactic structure."


Yes, but she never says what aperture she is using. The Lumicon Deep-sky would be more effective (especially in smaller apertures), as it also has a light blue cast and a passband that has a transmission of 90% or higher over a wide band of wavelengths (the 82a is probably closer to 75% at most). The blue transmission may help the contrast of the spiral arms slightly, but more than likely, much of the contrast boost is from the elimination of the Sodium D and Oxygen I airglow emission lines. Clear skies to you.

#9 JimK

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Posted 10 March 2011 - 06:29 PM

Yes, but she never says what aperture she is using...


Agreed, and I suspect it had a 10-inch aperture, because elsewhere on her web pages she states:

After having a 10" Schmidt-Cassegrain for three years, I sold it in favor of a 10" f/6 Dobsonian, something I can lift and transport easily myself. I’ve logged literally hundreds of hours at the eyepiece... {Ref}

#10 azure1961p

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Posted 10 March 2011 - 07:24 PM

Its a nice thing when a fellow amateur astronomer can do something seat of the pants like tat and have her experiences discussed in an astronomy forum - via her web page.

Pete

#11 Asbytec

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Posted 10 March 2011 - 08:54 PM

David, agreed totally. A band pass filter or magnification will do the same thing, essentially, and probably better.

I though about trying the 82A on M51 last night to see if her observation was a long lost secret.

#12 Simoes Pedro

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Posted 14 March 2011 - 05:56 PM

A CLS helps on my 4"

#13 JoeR

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Posted 14 March 2011 - 07:24 PM

I have a 2" 82A and Orion Skyglow filter which I've used frequently on DSOs. I now only use the Skyglow filter when needed. The 82A did look good on M31 though.

#14 arpruss

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Posted 27 March 2011 - 09:30 PM

I'd like to play with that. Does anyone know which of the Rosco lighting gel filters would be closest to 82A, or know where one can find a transmission curve for 82A?

In my Rosco swatch book, among the palest of the blues, I've got 3208 Quarter Blue "Boosts 3200K to 3500K" and 3216 Eighth Blue "Boosts 3200K to 3300K". The 3216 curve looks to me to be at a little more than 70% transmission and the 3208 at something in the mid 60s.






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