How to make a solar filter for an 8" dob?

[maxwolfie (Greg)]

Hi all,

I recently bought some Baader solar filter sheet and I was hoping to be able to make a simple/easy solar filter out of it this weekend. I have an 8" dob and the filter that I bought is probably not quite that wide - It's an A4 sheet so I'd say it's good for 6" (at least) or up to 7".

What the easiest/safest/cheapest way to do so?

[BlackWidow (Mardy)]

Hi Greg. You don't need to cover the whole scope end with Baader film. The sun is very bright so what I did on my 10" is as follows. Make a filter using some thin card that will fit in the end on the scope. Or I used a lid from a mayonnaise bucket the fitted perfect th the end of th scope. Then I cut a small hole towards the side about 2" round. Make sure it sits clear of the secondary mirror and spider. Place film over that hole only and you done. This will reduce the amount of light entering the scope and works fine. You will only need a very small amount of your film. Make sure no sunlight can pass into the scope other than via the filter film or you will burn your eyes.


Hope this helps and have fun looking at the sun


Mardy

[maxwolfie (Greg)]

So, if I have an 8" dob, should I make an off-axis one? Or, should I be leaving 7"? all around equally, or 6" or what? Some guides advise that it is better to have a smaller aperture rather than a larger one.

[astroron (Ron)]

Originally Posted by maxwolfie

Hi all,

I recently bought some Baader solar filter sheet and I was hoping to be able to make a simple/easy solar filter out of it this weekend. I have an 8" dob and the filter that I bought is probably not quite that wide - It's an A4 sheet so I'd say it's good for 6" (at least) or up to 7".

What the easiest/safest/cheapest way to do so?

Does your DOB have a front cover
If so there should be a small hole with a cap on it.
Make a filter to cover that hole, that is all the appeture
that is required.
If no cover make a cardboard cover and make a 3"= 75mm hole off axis and cover that with the filter film.
Try to keep the filter film as smooth as possible.
Cheers

[hickny (Peter)]

Hi maxwolfie (Greg),
Mike Salway has an article on making a solar filter here http://www.iceinspace.com.au/63-136-0-0-1-0.html

I've made quite a few using his idea and they work fine.

[maxwolfie (Greg)]

Thanks guys, no the front cover is one piece, it doesn't have a smaller aperture hole unfortunately. My little refractor does though.

Peter I'll probably follow that guide tomorrow, cheers!

[Chif (Andrew)]

Originally Posted by astroron

Does your DOB have a front cover
If so there should be a small hole with a cap on it.
Make a filter to cover that hole, that is all the appeture
that is required.
If no cover make a cardboard cover and make a 3"= 75mm hole off axis and cover that with the filter film.
Try to keep the filter film as smooth as possible.
Cheers

I did this with mine the other day. It works really well. I also bought the Baader film and it had instructions with it on how to make the filter itself (by sandwiching it between two pieces of cardboard.)

It's really cool to look at the sun. Although I'm not getting as much detail as I'd hoped for. I think a shroud for my scope will help. But from what I've read, what I want is a H-alpha filter, is that right?

If that's the case, do they do a film that has this?

(sorry to butt in on your thread Greg, but it may be helpful to you as well.)

[maxwolfie (Greg)]

Originally Posted by Chif

I did this with mine the other day. It works really well. I also bought the Baader film and it had instructions with it on how to make the filter itself (by sandwiching it between two pieces of cardboard.)

It's really cool to look at the sun. Although I'm not getting as much detail as I'd hoped for. I think a shroud for my scope will help. But from what I've read, what I want is a H-alpha filter, is that right?

If that's the case, do they do a film that has this?

(sorry to butt in on your thread Greg, but it may be helpful to you as well.)

No problems at all!