solarscope double stack 70mm or single stack 100mm etalon?

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iseegeorgesstar
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solarscope double stack 70mm or single stack 100mm etalon?

Post by iseegeorgesstar »

Hello,

I've been thinking about getting a front etalon for a long time. To be honest, I'm probably going to go for a single stack 70mm etalon (for budget considerations). But I wanted to ask, in terms of long-term planning.

Do you think I'm better off going double stack 70mm or single stack 100mm halpha? They cost around the same. This is purely for visual use. I don't image. I currently have a 4" refractor and might upgrade to a 5" one.

I'd love to hear people's experience with front etalons use, specifically different sizes and lower bandpass (for visual).

Regarding my visual style. My environment doesn't really support high mags (100-140+x) for the sun but I tend to crank it up anyway and just wait for the half second of good seeing that makes the mush worth it. I love to binoview the sun so I think the large etalon might be better. (?)

Thanks for any and all comments.


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Re: solarscope double stack 70mm or single stack 100mm etalon?

Post by Bob Yoesle »

Front etalons generally offer the best contrast uniformity compared to internal etalon systems, and almost every double stacked filter system will offer much better contrast performance than a single etalon filter system. Another general "rule" is that a double stacked filter system seems for most people to be as good as and comparable to the next larger sized single etalon filter system.

The Solarscope filters are beautifully made and generally excellent. They are now produced by Manx Precision Optics after Ken Huggett retired.

However, one of the issues I had and others have had with the Solarscope 100 mm is thermal instability of such a large etalon. This would have required an new ERF IR blocking coating, or the link's solution of adding a Baader DERF. So before buying the Solarscope 100 I'd want to see if an ERF coating revision has been made, and if not, adding the Baader 110 mm DERF would be mandatory in my opinion.

Then you have to figure the costs of the various choices. Last I recall, the Lunt 100 mm etalon might be about the same price as the Solarscope 70 mm. And because the Lunt has the "Root3" spacer system, it likely has very good thermal stability (no issues from those that have it that I'm aware of). The improved resolution of going from 70 to 100 mm should be very noticeable if your seeing is good.

The double stacked Solarscope 70 mm would also certainly be very good - but if for the same cost of the 70 DS you could go with a Lunt double stacked 100 mm, that would probably be the way to go as well.

Bob


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Re: solarscope double stack 70mm or single stack 100mm etalon?

Post by Montana »

As you say you are purely visual then I would recommend you go for the 70mm double stack. A single stack is just not enough for visual. With double stack you will get much greater surface detail which will allow for greater visual enjoyment. 70mm is more than enough detail for the eye to see, having a double stack far outweigh any benefit that more aperture would give (for visual).

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Re: solarscope double stack 70mm or single stack 100mm etalon?

Post by Highbury Mark »

I haven’t used a 100mm etalon, but I can certainly recommend the double stacked 70mm Solarscope filters. Good consistency across the fov, excellent contrast, and enough transmission to allow 140-150x with a binoviewer on very good days. They were a significant improvement on the Lunt 60DS I previously owned.
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