The 2017 Great North American Eclipse is less than a year away, With only once chance to get things right, I've decided to do an apples to apples evaluation of white light filters for the Questar. I'm waiting for some good sunspot weather. So far I have the Questar sub-aperture filter and Thousand Oaks film and glass filters. I hope to add the Baader photographic film and Questar full aperture filter for the comparison as well.

White lite filters can be attached to the Questar either via a slip fit over the dew shield or via a standard 95mm camera screw thread mount. Thousand Oaks Optical makes both style mountings. You can make your own threaded mount by re-purposing the mounting ring form an inexpensive 95mm UV filter.

The Questar sub-aperture glass filter with 95mm threaded mount included with most 3.5" Questar scopes is show above.

The Thousand Oaks Optical full aperture RG film filter with slip over mount is shown above. They now use a different film called Solarlite which is reported to not perform as well.

The Thousand Oaks Optical full aperture Solar II Plus glass filter with slip over mount is shown above.

I plan to construct a filter with the Baader photographic grade film to test as well. If anyone near Austin has a Questar full aperture filter that they can lend for the tests, please contact me.

P.S. You can see the results of this project with data taken in December and with a refined procedure and Questar full aperture filter in February..