Solar Viewing Filter

[Amra]

Hi guys, I've started using Baader AstroSolar Safety Film to make filters for my telescopes. But have a few questions.

Luckily my dustcap for the Explorer 200P had a removable cap, so I could simply tape solar film to the other side and hey presto I've got a solar filter!

Wanted to ask if you think this one I made for my Explorer 200P looks good and more importantly safe? Will I always be able to see if there is any stray light shining through any micro fractures? I was careful not to stretch the film, but maybe taping all the way around still has had an adverse effect, not sure. I want to be super careful around viewing and imaging the sun!

Should I ever desire a full aperture solar filter for more detail or will this one be sufficient? The small hole is like 55mm and I read or heard somewhere that filters never need to be more than 3" large.

This is the observing solar film from Baader, but would it work well with imaging as well? Am I right in thinking that the solar film for viewing is safe for both the retina and cameras, whilst the foto solar film (which I don't have atm) lets a bit more light through, which the cameras cope just fine with (and those films provide more detail?)

Or could I get fine results imaging with the same solar filter I use for viewing?

[Bizibilder]

Your filter should be fine for visual and photography. The only comment I would make is that clear tape (as you have used) may not stay in place for long - maybe you could try a heavy duty tape (Duct tape) that will last for years. You must also remember to check your filter for damage and pinholes before every use.

[Amra]

Yeah, I know the clear tape is weaker, I used it in case I want to remove that sheet some time for some reason, without making a mess on the dust cap. But yeah if I check inspect it carefully before every use I'll hopefully be fine.

[steveb1977]

Obviously always check that the tape is still fully secure secure. You wouldn't want thetop part falling away or a breeze blowing the film away a bit from the hole.

I have used the same sized filter and the views are fine. Although I'm not sure if their is benefit to having a larger filter. I'm looking to build a new one of these so would beinterested to hear what other people thought about how big to make these filters?

[Bizibilder]

There is little point in going bigger than about four inches (100mm) aparture as the resolution of the image is governed by the atmosphere (which by definition is hot and turbulent on a sunny day) rather than the aparture of the scope you are using.

[steveb1977]

Thanks for that Roger.

The mirrorI have is 8", I would want to mak the filter the full 4" for when daytime seeing is at its best, could stop it down a bit at other times.

This would meen the secodary infringing on the feild of view a bit for an off axis filter. Could this have any detrimental effects?

[JamesF]

I'd be concerned about the adhesive on the tape degrading too.

I can't see that the secondary being in the field of view should be a problem -- it's not a problem when you're looking at anything else. Perhaps you could go for a 5" aperture to make up for the loss of light, but it's probably no big deal.

James

[steveb1977]

Thanks James. Just checked and i have a piece of film just under 5" so might as well use the lot. As I say will probably add somthing to stop it down to a smaller size.

[JamesF]

For what it's worth I use a full aperture filter on my 127 Mak. Obviously the central obstruction is quite small compared with a newt and there's no spider.

James

[Ohmless]

neat job. I am looking to do the same thing soon, but my cap is a lid from an old oatmeal box.