Triband SCTs for Solar Astronomy: sounds very interesting indeed.

[michael.h.f.wilkinson]

I just recently found this page on the Baader website:

https://www.baader-planetarium.com/en/telescopes/baader-planetarium/triband-sct-schmidt-cassegrain-based-multi-purpose-telescope-for-sun-and-deep-sky.html

Much like other adaptations using an H-alpha type ERF coating on the corrector plate, Baader have put a tri-band ERF coating on it, allowing observation and imaging of Ca-K, Solar Continuum, and H-alpha. It could also be used for deep-sky imaging by using narrowband filters (or treating the tri-band ERF as a kind of UHC filter, transmitting O-III, H-beta, H-alpha and S-II). I have seen some dazzling solar shots taken with this type of scope. So I am sorely tempted.

I was considering building a 6" dedicated solar refractor with my Beloptik tri-band ERF halfway down the tube, which would work in a similar fashion, but would be heavier, longer, and only really fits on my Vixen GP-DX mount (the Vixen GP would struggle). The larger aperture would be nice as well, although I am not sure it would be great for CaK, except on days of great seeing. Another advantage of going for the Tri-Band SCT is that it would free up the tri-band ERF for continued use in the 80 mm APM.

[Highburymark]

This is the Holy Grail for solar imaging from what I’ve read Michael - I know you’re based in the Netherlands but Astrograph is the main U.K. retailer for these systems - speak to Rupert if you need advice.

[The Admiral]

3 hours ago, michael.h.f.wilkinson said:

I just recently found this page on the Baader website:

https://www.baader-planetarium.com/en/telescopes/baader-planetarium/triband-sct-schmidt-cassegrain-based-multi-purpose-telescope-for-sun-and-deep-sky.html

Much like other adaptations using an H-alpha type ERF coating on the corrector plate, Baader have put a tri-band ERF coating on it, allowing observation and imaging of Ca-K, Solar Continuum, and H-alpha. It could also be used for deep-sky imaging by using narrowband filters (or treating the tri-band ERF as a kind of UHC filter, transmitting O-III, H-beta, H-alpha and S-II). I have seen some dazzling solar shots taken with this type of scope. So I am sorely tempted.

I was considering building a 6" dedicated solar refractor with my Beloptik tri-band ERF halfway down the tube, which would work in a similar fashion, but would be heavier, longer, and only really fits on my Vixen GP-DX mount (the Vixen GP would struggle). The larger aperture would be nice as well, although I am not sure it would be great for CaK, except on days of great seeing. Another advantage of going for the Tri-Band SCT is that it would free up the tri-band ERF for continued use in the 80 mm APM.

Hmm, interesting. Forgive my asking, but isn't the Ha filter a 'broad band' Ha filter rather than the really ultra-NB, Angstrom-wide, etalon type which are used for viewing the proms etc? Is it's function then more of a blocking filter/ERF, requiring the addition of something like the Quark to view the Ca-K or Ha?

Ian

[johninderby]

You need to add the following or similar for observing Ha with this scope. 

https://www.baader-planetarium.com/en/solar-spectrum-observer-series-15.html

[michael.h.f.wilkinson]

23 minutes ago, The Admiral said:

Hmm, interesting. Forgive my asking, but isn't the Ha filter a 'broad band' Ha filter rather than the really ultra-NB, Angstrom-wide, etalon type which are used for viewing the proms etc? Is it's function then more of a blocking filter/ERF, requiring the addition of something like the Quark to view the Ca-K or Ha?

Ian

 

9 minutes ago, johninderby said:

You need to add the following or similar for observing Ha with this scope. 

https://www.baader-planetarium.com/en/solar-spectrum-observer-series-15.html

It is just an ERF, so an etalon is needed behind it for solar H-alpha, or a DSO H-alpha/O-III/S-II filter for narrowband DSO imaging. I have a Solar Spectrum 0.3 Å filter, a Lunt Ca-K Module (B1800 type, so not the entire sun in the FOV), and a Herschel wedge and solar continuum filter for white light, so that should do nicely. I will probably get a TZ-3 tele-centric lens to get to F/30, although I might first use a Meade 3x TeleXtender.

[michael.h.f.wilkinson]

OK, I have bitten the bullet and ordered one. Should arrive late next week