Making a solar filter - binoculars advice

[davekelley]

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

Dave

[SteveWolves]

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.

[LukeSkywatcher]

I have a set of Lunt 8x32 Sunoculars. Great for a quick scan in white light to check for sun spots, before dragging out the scope and Quark, or Hershel wedge.

 

Lunt-SUNoculars-8x32-Black__23771.1598226882.webp

Edited April 7, 2021 by LukeSkywatcher

[Nigella Bryant]

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. 

[Stu]

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.

[Stu]

I just found this thread which shows that Seymour 70mm glass filters work with the 15x50IS binos.

https://www.cloudynights.com/topic/203175-solar-filters-for-canon-15x50-is/

Another useful thread here

https://www.cloudynights.com/topic/529445-white-light-solar-filters-for-canon-15x50is/

[Stu]

Even better! I see they now make 58mm solar filters which will screw into the thread on the binos, very safe and easy too.

https://www.rothervalleyoptics.co.uk/seymour-solar-threaded-camera-solar-filter.html

or on Amazon...