Solar Filters... Dec 20, 2011 3:38:00 GMT -6
Post by Chicago Astronomer Joe on Dec 20, 2011 3:38:00 GMT -6
Telescope Aperture Solar Filters
I have been looking into solar filtering for awhile now, and Chicago Astronomers are gearing up for the June 2012 Venus Transit with projection and filter ideas and equipment.
Film or glass, blue, neutral white or orange, off-axis or full aperture....it's all about preference. I'm going to do my best, (as as much as I can afford), to test out various types of filtering. I got six months and the material/equipment will be cheaper now, then when the Venus transit hype takes off.
Primarily, the search will be for a suitable filter agent for the C11 beast. Full aperture I think - as limiting the aperture for off-axis viewing, (is good), but steals the magnification and resolution power of any given scope - I don't care what anybody says... Atmospheric & OTA turbulence and secondary obstruction is often quoted against full aperture filtering - but if so, I'll have the option to cut down the usable surface with suitable blocking as the need arises with a full aperture set-up.
No film or filter will be wasted, as there are finders, smaller scopes and binoculars to protect for solar observation.
My first selection is the "Seymour" Solar filter sheet...
At 9"x10", it's large enough to make several test caps for my optics. It's a black material, providing a Yellowish-Orange tint to the disk. Pleasing to the eye, but I understand that this skew to the red part of the spectrum cuts out other wavelengths - primarily the blue...where the sharp definition lays. Granulation and faculae may not be as sharp, but with free shipping...the price is right.
If suitable then I'll order a full 12x12 ($18.00) for the C11 and make a suitable cell holder.
They do have both Off-axis and full aperture rings already made...
If I like this film, I'm seriously thinking about the $179.00 full aperture filter...
Details when it arrives, but the search continues for affordable solar filtering...