Making a solar filter cap.

[JB80]

Hey

I have got some baader solar film on the way and will be attempting to make solar filter for my telescope, but I have a question.

I have seen a couple of threads around that people use different sizes of the cut out film.

For example there is this thread...

http://stargazerslounge.com/diy-astronomer/109614-nescafe-baader-astro-solar-filter.html where it is a full arpeture cut out of the film. I thought you only needed one smaller or even two smaller circles cut out and not the full arpeture. As a person in the thread mentions my telescope has a small cap already in place, is that what it is for, can it be used for that?

So I guess what I'm asking is what would be the best way to go about it, making a full arpeture or only need to do a smaller one?

[G4YVM]

When I made mine I wrapped a strip of card around the scope, then the film, then another strip of card. I made a full apperture filter.

David

[JB80]

Thanks David for the reply.

That is what I was originally going to do but then seeing other types has made me second guess. I was just wondering what the benifits and downsides to the different types are.

[brianb]

what would be the best way to go about it, making a full arpeture or only need to do a smaller one?

You don't say what sort of scope you have.

Up to 5", no doubt, full aperture.

Over 8", full aperture will rarely if any be as useful as you'd think (the Sun makes its own bad seeing by heating the air, it tends to be much worse than night time observation with the same scope). With a Newtonian / SCT / Mak, a good plan is to make an offset aperture which just touches the outside of the objective aperture and the secondary. You may want to make a full aperture filter as well, for the odd occasion when the seeing is really good.

5" to 8", make a full aperture filter and a cardboard mask to reduce its aperture to 5" for use when seeing is, as usual, pants. Best kept symmetric with the axis even though the central obstruction in a reflector will "grow" as a proportion of the illuminated aperture - this is better than the weird shape that a partially obstructed offset mask would cause.

[JB80]

Oops, it's a Skywatcher 150pl. Suppose that could be useful information.

So a full arperture would probably be best for me then, maybe even make a offset one as well if I have enough film left over for comparisom.