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The way forward

David Smith

By David Smith
in Imaging - Solar

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David Smith

David Smith

Posted
Posted

I decided some time ago that CaK would be the next step in my solar astronomy journey. I already have the Evostar 120 + Baader filter for white light and the PST for H alpha so seems logical to diversify before upgrading current setup. Now, CaK is not cheap and realistically I need to keep costs as low as I can (this probably means a B600 blocking filter) whilst being practical about the flexibility / usefulness of the kit I end up with so I find myself with a few choices:-

1. Get a Lunt LS60T CaK dedicated CaK scope. Advantages: all in one package with minimal risk of issues and should give me a full disk image with my QHY5 camera. Disadvantages: limited aperture although I could later use the CaK module with another OTA.

2. Get a B1200 module and use this with my Evostar 120 (masked down to 100mm). Advantages: Greater flexibility with the B1200 module and ability to take close-ups with current scope. Disadvantages: Cannot get a full disk with my QHY5, increased cost, I will need to get a better / tracking mount (pushing costs up further).

3. Get a B600 module and a SW ST102. Advantages: Keeps cost down (as I have the opportunity to pick up a ST102 quite cheap at the moment), can get a full disk from my QHY5 camera. I can potentially also use this with a Herschel wedge as well (where as it is borderline with the Evostar 120 although I could use a mask), can use a barlow for close-ups.

Questions: Is the ST 102 suitable for the purpose i.e. will it work and will it provide a significant advantage over the LS60? Are there any other considerations I have missed?

If I am going to go down the route of the ST102 then I need to act relatively quickly even though I will not be in a position to get the CaK module until Q1 2015.

Any thoughts, comments, questions welcomed!

Thanks

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Montana

Montana

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Calcium K imaging is a complicated subject and I am still trying to manage it. There are some on the other forum where the quest is an obsession. It is very important that you pick a refractor which is well corrected in the blue otherwise spherical aberration ruins everything and focus is impossible. I found this out the hard way, the maximum I can use on my scope is 120mm but 110-100mm is optimum. So don't assume the aperture you have will be the aperture you use the module at.

I would avoid the B600, Chris Schur has this and it is not recommended for use above quite a small aperture or focal (I can't remember) but for him he has to use all sorts of barlows etc to get rid of the dark rim and has been nothing but a nightmare.Lunt state the specs on the website, follow them. For 100mm the recommended is the B1200. Always work to f10, the scope should be as close to this f number as possible.

Alexandra

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David Smith

David Smith

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Hmm, this is why I was considering the Lunt scope as a complete package as my research to date has indicated some complexity in identifying a scope suitable for this application. However, having the opportunity to pick up a larger aperture scope for not much money I thought it was worth considering. Looking at the Lunt specs the B600 is recommended for apertures up to 100mm and focal length up to 540 mm and the ST102 meets both of these criteria.

Thanks Alexandra

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Montana

Montana

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I guess the straight though is less glass so better for imaging but I have the diagonal version and it seems OK but then perhaps that is why I am struggling? the only thing I am not so happy about is the 1.25" at the eyepiece end as it is not as versatile and I can't use some barlows.

Alexandra

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