Another Homemade Solar Filter

Back a year or so ago, I built a wood frame solar filter for one of my larger telescopes and, if interested, you can read about it here.  This is another blog entry about a new homemade solar filter that I made about a month ago to be used, mostly, for testing purposes but it never hurts to have multiple ways to view the sky, daytime or nighttime.  

I decided to build this solar filter for two reasons.... 1) I already had the supplies so it wouldn't cost me anything, and, 2) I want to compare one of my Spectrum glass solar filters to this new solar film filter I made as well as compare it to my solar wedge as a comparison between the three types of solar filters.  

To make this comparison as accurate as possible and to keep as many scientific controls as possible in this little test, I decided that I should use the same telescope and the same camera so the only significant variable in this test would be the filter itself.  My small Skywatcher ED 72mm refractor was the best option for this test since I already had a glass solar filter and a solar wedge for it so I needed to make a solar film filter to fit this telescope in order to test the filters as planned.  

Vent slats removed and parts cut to size.

The biggest decision to make in building these solar filters is to choose a material for the frame of the filter.  Most people use cardboard.  A cardboard filter is too flimsy and too unprofessional for the perfectionist in me so that wasn't an option.  I didn't want to make a filter that looked like it was made in a kindergarten class.  

In the past, I mounted a solar film filter in a homemade wood frame.  That was a nice project (linked, above, in the first sentence) but, for this test, I didn't want to go through the trouble of making a wood frame again.  After hunting around for some leftover construction materials that I could adapt to use for this frame, I found two round soffit vents that could work.  

Dry fit of the two vents as a single solar filter.

These vents were round and fit over the end of this telescope perfectly after adding some felt to the inside of the vent.  The felt made the homemade filter a bit more snug and secure on my telescope while also keeping the filter from scratching my telescope.  I would just need to cut out the vent slats because I really only need an open circle where I would mount my solar film.  My Dremel tool made fast work of cutting out the vent slats and then grinding the nubs of the vents slats smooth.  

Getting ready to cut and glue the film filter material.

I wanted to sandwich the film filter material between two "frames" so I cut off the part of one of the vents that would go into the soffit (or around the end of my telescope).  This would leave me with a simple ring that was the same size as the top ring on the other vent.  I would simply sandwich the filter film between these two parts using silicone caulking to glue it all together.  

The film filter material is sandwiched and glued onto the frame.

Between my health and the weather, I haven't yet had a chance to run the comparison test.  I did, however, test this new film filter.  The view of the sun is exactly the same as the view I get from the previous wood frame solar film filter I built.  Unfortunately, it is a view I don't particularly care for which is why I prefer my glass filter and my solar wedge.  

The finished filter slipped over the front of my telescope.

Of the three types of solar filters, the solar wedge provides the most detail, by far.  It is abundantly obvious simply by viewing.  That being said, I need proof of my evaluation and the way to prove this point is to get some photos shot through each filter, one after the other in equal conditions.  I'm confident that the solar wedge will provide the most detail.  I've already used that filter many times and the results are spectacular.  I feel that my Spectrum glass solar filter will come in second place though.  My views just seem crisper through this glass filter than what I see through the Baader film filters.  Shooting photos through each of these filters should prove my point.  If I am wrong, then I will admit it.  The photos should provide a way to closely evaluate each type of filter.

Needless to say, this sounded like a good scientific experiment.  Now I just need to get out there on a very clear morning to run this experiment with proof in photos!