CaK ERF filter for Lunt module

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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Sergio Alessandrelli
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CaK ERF filter for Lunt module

Post by Sergio Alessandrelli »

Hi to all

It's the first time I write on SolarChat but I've always found al lot of useful information on that pages. So, just a question: I use a WilliamOptics FLT132 with a full aperture Baader D-ERF for the H-Alpha and a Baader cool-ceramic for the other filters. Now I'm using a lunt CaK module but I'm not sure I can use it with the cool-ceramic (back focus, filtering etc.) and the Lunt suggest not to use the CaK module with a diameter larger than 100mm.
What could be used as full aperture ERF in front of the lens or internal as sub-aperture before the CaK module?

I see that Altair has multiband ERF filter like Baader for its SCT etc, but I'd like not to replace the D-ERF I already have also to separate Ha and CaK band...

I'm using the telescope at full aperture but I don't want to damage it, so alternatives are internal/front ERF or diaphragm it.

Thank you for your suggestion ;)

Sergio


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marktownley
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Re: CaK ERF filter for Lunt module

Post by marktownley »

Hi Sergio,

Welcome to the forum. I would suggest stopping the scope down to 90m to use with the CaK module. At full aperture the scope will be full of spherical aberration at CaK wavelengths. 90mm will give significantly better results.

Mark


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Re: CaK ERF filter for Lunt module

Post by Sergio Alessandrelli »

Yes I think it could be a good solution to reduce the aperture of the lens also to balance my local seeing.
Thank you.


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