Jump to content


Making a solar filter - binoculars advice

Recommended Posts

I have purchased a sheet of Baader solar film to make pair of solar filters for my Canon 15x50 IS binoculars.  I had intended to modify some pop up objective lens caps, outer diameter 70mm, by making 2 circular cells with 50mm central openings, out of the film and stiff card, then gluing them to the inside of the lens caps which have a good 25mm of depth, so that the cap can still be closed and protect the film when not in use.  That was my plan,  However the film comes with instructions showing an overlap around the objective lenses which could be square or circular.

Is it necessary to have this overlap, considering that with binoculars your eyes are looking directly towards the Sun, whereas with a telescope they are not?  The issue is that the 15x50 objectives almost touch so there is no room for any overlap.  I would need to make a rectangular or oval shaped filter?  I do have another option which is to make filters for my smaller 8x30 Nikon Monarchs, or even for a cheap pair of Nikon 8x42's?  or should I go the whole hog and make a filter for my 127 Mak.  Does aperture or magnification matter when observing the Sun?  

I hope that's not too confusing I have tried to be as clear as possible.  I am torn because I love the 15x50's, the objectives do not move so a single, rectangular filter would probably be the solution?

Thanks everyone for any advice.  (Of course, safety is the most hugely important issue!!)

Clear skies


Link to comment
Share on other sites

Generally the overlap is to fold down along the bino body to ensure no stray light gets in. The sun in small binos is not very big in the field of view.  Whats the field of view of you 15x50's?

The filters I made just slip over the lens and are held on by sticky tape or rubber bands.

Link to comment
Share on other sites

Solar filters need to be secured to any objective lens be that binoculars or bino. You can easily boil your eyeballs. Elastic bands can easily flip off. Just be really careful you've only one set of eyes. Personally I'd go the whole hog and make a solar filter for your 127 mak. 

  • Like 2
Link to comment
Share on other sites

8 hours ago, davekelley said:

Does aperture or magnification matter when observing the Sun?  

Yes, absolutely, these two things make a huge difference when observing the sun.

In your binoculars you would just be able to make out the larger spots but with little detail. A full aperture filter made for your scope should offer you much better, high resolution views showing much more detail of the spots and granulation when conditions are good. I frequently use magnifications between x100 to x200 when the seeing allows, but certainly x50 to x100 will give some great results.

So, whilst it would be fun to make filters for the binos, the results with the scope would be much more rewarding I think.

For the binos, have you considered making something using screw-in step down rings to fit the threads on the front of the objectives? I had a pair of these binos before and used to fit UHC and OIII filters to the front for viewing the Veil and North America nebula at dark sites, it worked very well.

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.