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SCT suitability for white light solar

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#1 BlueMoon

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Posted 19 January 2021 - 08:58 AM

Hi folks.

Is anyone using an SCT for white light solar? I have a '77 C8 with a anodized aluminum solar mask configured with an offset 3" port. The "welding mask grade" glass filter is intended for observing eclipses and not much else. I'm thinking about removing the glass and using my 1.25" Lunt wedge and filters as the C8 can reach much higher magnification levels than my current "solarized" 72mm refractor does. Thoughts?

 

Clear skies and be well.


Edited by BlueMoon, 19 January 2021 - 09:35 AM.


#2 MalVeauX

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Posted 19 January 2021 - 09:47 AM

Heya,

 

I wouldn't remove the glass and use a wedge. The wedge won't work right with the two mirrors as they absorb some energy, unlike refractor lenses which pass all of it. You need an ERF, be it solar film, etc, on that SCT even if's off axis and partial. Solar film is cheap. It will do the job.

 

That said, aperture being so similar, your 72mm refractor versus a 3" (75mm) aperture on your SCT, you're just getting the focal ratio as the SCT mirror is actually F2-ish and then amplified. You might as well just be using a long high mag barlow on your refractor to get the same thing, with maybe possibly slightly higher brightness even (due to no obstructions and no mirrors absorbing some transmission, as those mirrors are probably less than 94% reflective by now, maybe in the 80's % range at this point). It's heavier and catches more wind; the refractor is much easier to handle and you can use your wedge as normal. You would just need a 4x barlow maybe to mimic the focal-ratio if you need high mag views.

 

Very best,


Edited by MalVeauX, 19 January 2021 - 10:15 AM.

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#3 BlueMoon

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Posted 19 January 2021 - 10:09 AM

Good points. I hadn't considered the mirror absorption an issue outside of potentially generating excessive heat in the enclosed space. I have a Powermate 2.5x I can slip into the optics train so I'll give that a try and see how it works. waytogo.gif

 

Clear skies and thanks.


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#4 photomagica

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Posted 04 February 2021 - 08:51 PM

I use my C8 with a full aperture filter with Baader film in it. Works very well. I don't recall the price but the Baader filter wasn't all that expensive. I've also got a Baader Solar Continuum filter but there has not been an opportunity to try it yet.

Bill


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#5 BYoesle

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Posted 05 February 2021 - 05:05 PM

 

I'm thinking about removing the glass and using my 1.25" Lunt wedge and filters as the C8 can reach much higher magnification levels than my current "solarized" 72mm refractor does. Thoughts?

Don't do it! You risk damaging the secondary mirror and components, as well as the internal baffle tube.

 

Go with a full aperture Baader film filter, and use an off-axis version if your seeing wont support the 8 inch aperture. A 4 to 6 inch refractor would be best for the Herschel wedge.


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#6 ch-viladrich

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Posted 06 February 2021 - 11:30 AM

A few years ago, we had pretty large sunspots. Here is one taken with my C14 and Baader solar film :

AR1785-88-6July2013-C14-red.jpg

 

So yes, you can use a SC telescope for white light solar imaging. It is better to use Baader Solar film. Glass filters are usually of very bad quality, unless you have a Zeiss solar filter (its cost would be much larger than the cost of the C8 ...).

This being said, having stable collimation could be a  little bit tricky. Using a refractor is much easier.


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