Tinderboxsky
19-05-2012, 05:07 PM
I received my order of ISS eclipse glasses and that got me thinking. Mounting one of these in front of a telescope should act as a workable solar filter.
The only concern in my mind was that I did not gather too much light to make the final image too bright. Starting from a target magnification of 30X and the area of my eye pupil it was an easy calculation to estimate the size of the aperture stop to deliver an image of approx the same intensity as looking directly at the sun with the IIS eclipse glasses. This came out to 9mm.
My first attempt using a 9mm aperture stop delivered a crisp clear yellow-orange image dimmer than looking directly at the sun with the glasses with black surrounding sky. Quite a pleasing view with sun spots clearly defined. However the FOV was barely larger than the diameter of the sun, so it was difficult to view even with the smooth manual slow motion that the Vixen Porta Mount affords.
After some experimentation I settled on an aperture stop of 23 mm giving the most pleasing image. The sun's disc and the sun spots are crisp and well defined. The color is a yellow-orange with the surrounding dark sky having a slight orange wash through it. It is quite comfortable to view. Venus will definitely stand out well.
The photos show my 85mm spotting scope, an ideal size for this exercise. The disassembled components are a simple cardboard collar to fit firmly over the objective lens of the scope, a large cardboard screen to shade one's eye at the eyepiece and the aperture stop with one half of an IIS eclipse glasses fixed firmly onto it. The final photo shows the assembled solar filter in action.
So I am ready visually for the 6th. The photos show my clear view to the East. Just got to work on clearing the clouds. If it is cloudy I plan to travel inland looking for clear skies.
So, a simple solar filter solution for a small telescope courtesy of one $4 IIS eclipse glasses lens.
The only concern in my mind was that I did not gather too much light to make the final image too bright. Starting from a target magnification of 30X and the area of my eye pupil it was an easy calculation to estimate the size of the aperture stop to deliver an image of approx the same intensity as looking directly at the sun with the IIS eclipse glasses. This came out to 9mm.
My first attempt using a 9mm aperture stop delivered a crisp clear yellow-orange image dimmer than looking directly at the sun with the glasses with black surrounding sky. Quite a pleasing view with sun spots clearly defined. However the FOV was barely larger than the diameter of the sun, so it was difficult to view even with the smooth manual slow motion that the Vixen Porta Mount affords.
After some experimentation I settled on an aperture stop of 23 mm giving the most pleasing image. The sun's disc and the sun spots are crisp and well defined. The color is a yellow-orange with the surrounding dark sky having a slight orange wash through it. It is quite comfortable to view. Venus will definitely stand out well.
The photos show my 85mm spotting scope, an ideal size for this exercise. The disassembled components are a simple cardboard collar to fit firmly over the objective lens of the scope, a large cardboard screen to shade one's eye at the eyepiece and the aperture stop with one half of an IIS eclipse glasses fixed firmly onto it. The final photo shows the assembled solar filter in action.
So I am ready visually for the 6th. The photos show my clear view to the East. Just got to work on clearing the clouds. If it is cloudy I plan to travel inland looking for clear skies.
So, a simple solar filter solution for a small telescope courtesy of one $4 IIS eclipse glasses lens.