Evostar 72mm question

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ffellah
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Evostar 72mm question

Post by ffellah »

Hello all: If I want to use my SW Evostar 72mm for Ha with an external, front mounted etalon, what would be an appropriate choice ? What are the options ?

Thank you for your help,

Franco


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Re: Evostar 72mm question

Post by Sol seeker uk »

Front mounted etalon?
Do you mean a front mounted ERF ( energy rejection filter)?
You will still need a etalon of some description, either within a quark or from a lunt or PST mod.. A ERF is to protect the tube/ camera from getting too hot, not to view the sun in the ha wavelength.. caution is always needed to view the sun, especially using your eyes


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Re: Evostar 72mm question

Post by JochenM »

Hi Franco.

To the best of my knowledge, there's three available options:

- Coronado SM60
- Lunt LS60FHA
- Solarscope SF60/SF70

Or any of the above in a smaller version obviously.

I only have experience with Lunt etalons and have nothing negative to say about it. I'll leave it up to others to comment on the other two options.


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Re: Evostar 72mm question

Post by rsfoto »

Hi Franco,

Jochen gave you the three available options but if you want to have a good etalon adjustment solution then only the Coronado can be adapted with my remote etalon adjuster :lol: as of today ...

What a shameless advertising :mrgreen:

Of course one has to think about the 10mm more aperture of the 70mm filter if it is worth or not. It has a 36% more surface ...


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Re: Evostar 72mm question

Post by ffellah »

Thank you all for your responses. If I get a front mounted etalon that is tunable and add a diagonal with blocking filter (I already have the 15mm Coronado) I should be in business, right ?

Franco


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Re: Evostar 72mm question

Post by Sol seeker uk »

You have the Coronado bf15? Which is a blocking filter.. etalons serve the purpose of the parallel beam of light
Etalons are optical components based on the principle of the Fabry-Perot Interferometer. They are effective
narrowband filters, transmitting only light of specific, periodic frequencies with tight bandwidths. They are
commonly used in applications such as telecommunications, lasers and spectroscopy.
An Etalon consists of two flat, partially reflecting plates separated by a distance. The gap between
them, either in vacuum or filled with air or some solid substrate forms an optical cavity. These two
types are known as “Air Spaced” and “Solid” Etalons respectively and possess different advantages and
disadvantages.
Are you talking about a double stack, which are usually from mounted?


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Re: Evostar 72mm question

Post by rsfoto »

ffellah wrote: Fri May 06, 2022 7:20 pm Thank you all for your responses. If I get a front mounted etalon that is tunable and add a diagonal with blocking filter (I already have the 15mm Coronado) I should be in business, right ?

Franco
Hi Franco,

That is correct. You will need an adapter for the etalon to get it onto the front of the scope.


regards Rainer

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Re: Evostar 72mm question

Post by marktownley »

IMHO, the best value option at the moment is the Lunt 50c etalon. You will need an adapter to mount to the scope but you can use your coronado blocker.

https://luntsolarsystems.com/product/lu ... ck-filter/

It's what I use on my ED60.

Image20220329_181535 by Mark Townley, on Flickr

Works for me!

ImageHa-FD-DS50-bw by Mark Townley, on Flickr


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Re: Evostar 72mm question

Post by ffellah »

Thank you all for your input. Mark: the 50mm etalon from the link seems to be a second stack to reduce the bandpass to 0.5a. Would it also work as a single stack with a higher bandpass i.e. 0.7a ?

Franco


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Re: Evostar 72mm question

Post by marktownley »

Yup, I used mine for years as single stack before getting the second etalon.


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Re: Evostar 72mm question

Post by ffellah »

Thank you Mark


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Re: Evostar 72mm question

Post by Highbury Mark »

Agree that the Lunt 50mm is the best value external etalon out there for small scopes. The 60mm is double the price. Solarscope 70mm filters are also excellent. The factory will manufacture an adapter to fit your scope, and provide dedicated blocking filters for either single or double stack systems. But as mentioned in other threads, they are particularly expensive outside the UK. Within the UK, they are roughly compatible with Lunt prices. Coronado external etalons appear to be difficult to find at the moment, at least in Europe. The hope is that new owner Orion will reintroduce them at some stage.


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Re: Evostar 72mm question

Post by ffellah »

Thank you Highbury Mark.

Franco


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Re: Evostar 72mm question

Post by OlegLviv »

Highbury Mark wrote: Mon May 09, 2022 10:51 am Agree that the Lunt 50mm is the best value external etalon out there for small scopes. The 60mm is double the price. Solarscope 70mm filters are also excellent. The factory will manufacture an adapter to fit your scope, and provide dedicated blocking filters for either single or double stack systems. But as mentioned in other threads, they are particularly expensive outside the UK. Within the UK, they are roughly compatible with Lunt prices. Coronado external etalons appear to be difficult to find at the moment, at least in Europe. The hope is that new owner Orion will reintroduce them at some stage.
Yes 50mm Lunt good but you dont say 50mm have etalon size 20 mm but 60mm Lunt have 38mm :seesaw If you have 290mm 50 Lunt good,if you have 174mm or Apollo 432mm not good.


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Re: Evostar 72mm question

Post by nicosolcy »

Oleg, you need to match the scope's focal length with the pixel size of the camera and the FOV you want.

Potential grid patterns aside, the 178 is the best matched sensor for full disks on the Lunt 50 and Lunt 60 scopes.


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Re: Evostar 72mm question

Post by OlegLviv »

nicosolcy wrote: Tue May 10, 2022 9:22 am Oleg, you need to match the scope's focal length with the pixel size of the camera and the FOV you want.

Potential grid patterns aside, the 178 is the best matched sensor for full disks on the Lunt 50 and Lunt 60 scopes.
Ok yes had 178mm dont love her because small fps but 174mm loves very much+global sensor love big focal lenght.


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Re: Evostar 72mm question

Post by nicosolcy »

I would get about 68 fps with the 178 on a Lunt 60mm, using ROI. Yes, 174 has global rolling sensor and is suitable for longer focal lengths, but if you have to resort to barlows / telecentrics to increase focal lengths with small scopes, you are actually increasing focal ratio a lot and end up having to pup up gain...


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