Coronagraph

Use this section to discuss "standard" Baader/Coronado/ Lunt SolarView/ Daystar, etc… filters, cameras and scopes. No mods, just questions/ answers and reviews.
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MERRILL
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Coronagraph

Post by MERRILL » Wed Nov 18, 2020 11:30 am

I am making a prototype coronagraph.
However, I have not obtained sufficient results.
The filter I'm using now is Andover Corp's 10A H-alpha.
Does anyone know of a company that sells filters of about 5A?

Merrill55
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Re: Coronagraph

Post by LTHB » Wed Nov 18, 2020 4:32 pm

I think the blocking filters of Lunt and Coronado are about 6A.

Frank



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Re: Coronagraph

Post by Bob Yoesle » Thu Nov 19, 2020 2:02 am

Since you're talking H alpha filters, it seems you're talking about a solar prominence telescope (e.g. the chromosphere), not a coronagraph. There's a huge difference.

https://en.wikipedia.org/wiki/Coronagraph

You may want to review this couple of threads on Cloudy Nights:

https://www.cloudynights.com/topic/6425 ... velengths/

https://www.cloudynights.com/topic/7403 ... yesterday/

The best emission line for a corona filter would be the Fe XIV line at ~ 530.3 nm:

http://www.zam.fme.vutbr.cz/~druck/ecli ... 0-info.htm

There's a much more complicated need for perfectly polished optics, occulting discs, and high altitudes free of dust and other light scattering issues to make a true coronagraph:
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MERRILL
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Re: Coronagraph

Post by MERRILL » Thu Nov 19, 2020 10:53 am

Thank you for your reply.

Of course, coronagraph and prominence scope I understand the difference.
I can't observe the corona with Pic du Midi.
The scope with the interference filter removed is a complete coronagraph.

I would like to see prominence in a wider range of wavelengths.
I used a blocking filter to see if I could see the prominence. But it was a disappointing result. I can't see it at all.
Blocking filter seems to have a different structure from the multi-layer interference filter for prominence.
The combination of Andover Corp's 10A Ha filter and Edmunds' 100A Ha filter It provides a minimal amount of prominence images.

If I have a chance next time, I would like to try two 10A filters on top of each other.

Merrill55
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Re: Coronagraph

Post by MERRILL » Thu Nov 19, 2020 11:16 am

Rondi 's Coronagraph site is as follows;
http://www.astrosurf.com/rondi/coro/
My prominence scope is same as this.



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Re: Coronagraph

Post by Montana » Thu Nov 19, 2020 11:48 am

Hi Merrill,

I own a Baader Coronagraph and recently had it refurbished by Wolfgang Lille. He replaced my Halpha filter so I expect he could supply you with the filters you require?

viewtopic.php?f=10&t=28709

viewtopic.php?f=10&t=27490&p=248471&hil ... ng#p248471

Alexandra



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Re: Coronagraph

Post by MERRILL » Thu Nov 19, 2020 12:17 pm

Thank you Alexandra.
I want to contact Wolfgang Lille.

Merrill55



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Re: Coronagraph

Post by LTHB » Thu Nov 19, 2020 1:01 pm

I am pretty sure Wolfgang Lille uses Lunt blocking filters for refurbishing Baader prominence viewers these days. Baader had used soft-coated 1.5A-filters that are no longer available. Contacting Wolfgang is a good idea, he is very friendly and knowledgeable.

Frank



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Re: Coronagraph

Post by MERRILL » Mon Nov 30, 2020 7:07 am

Andover Corporation makes semi-custom interference filters.
However, it exceeds 2000 dollars at 25 mm diameter 0.5 nm.
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Re: Coronagraph

Post by george9 » Wed Dec 02, 2020 2:56 am

The original Baader coronagraph with its occulting cone used a 10A H-alpha filter and worked well.

Without an occulting cone, 10A is too wide, and I suspect 5A is, too. Most prominence filters I know of use 2A.

I don't find that prominences look better in my 2A filter than in my 0.5A double stack or in my 0.3A single stack. So I don't bother with it. But it was interesting to try.

My next goal is to see prominences in their more natural colors, which means using an occulting cone and passing a series of wavelengths.

George



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