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Solar Filter Advice


Bart
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Hello All,

I'm sure you've all seen this question before. I have a 6' Newtonian and have recently bought some Baader film. The dust cap on the telescope has a small aperture with a cap. I'd say it is about 2' wide. Should i make a solar filter just to fit that, or should i make it for almost the 6' aperture available. What would the difference be at the eyepiece between the two differing size solar filters? Thanks for any advice.

Bart

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Sorry to hijack this thread... I too am dabbling in the "home made" solar filter arena, does it make a difference where the Baader film goes on the aperture mask, ie centred or would it be better off centre?

L.

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Sorry to hijack this thread... I too am dabbling in the "home made" solar filter arena, does it make a difference where the Baader film goes on the aperture mask, ie centred or would it be better off centre?

L.

I think that depends on your scope. If you have a frac, it should go centre, because that's where the best part of your optics is. If your scope is a Newt or a CAT, then you will need off centre because otherwise the secondary will be in the way.

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One thing struck me, surely the secondary will only get in the way for a solar filter as much as it does when observing at night, i.e. not noticeable. Therefore I should be able to use the full aperture, am i right???

Bart

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Yes Bart, you can use the full aperture with your 6" Newt. The filter would

only need to be off axis (away from the centre) if you were just using a much

smaller filter area. If you were using the 2" aperture you mentioned, and put

that in the centre, then most of it would be blocked by the secondary mirror.

HTH, Ed.

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Hello Bart, I've found that a good 60mm to 80mm aperture is pretty good for solar viewing and some mild imaging. That size also gives you good contrast in the image. In the past I experimented with a SCT 11 and an 80 ed, both at full aperture and while the 11's images were larger they just weren't as contrasty as the 80's. Lots of tube heating and other issues were probably to blame. If it were me I'd make a large filter cell then make a smaller removable mask for the front of it so you would have the best of both worlds. You could switch between them and see which you like best. Clear Skyz, :D

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