WHAT SIZE filter will fit my telescope?:
The application table below lists sizes by clear aperture (filter size) and outer cell wall inside diameter (I.D.) The I.D. of the cell slips over and around the O.D. of the telescope tube or lens holder. If you do not see your brand and model, simply choose the closest outer cell I.D. size larger than the outside diameter measurement from 4" to 4 3/16". Do not choose a size the same as your O.D. since this will be too tight and not allow room for felt lining. Ample felt is included for custom fitting.
full aperture versus off-axis (reduced aperture)?:
For telescopes up to 5" aperture, off axis is not an advantage. Larger apertures suffer more from daytime atmospheric turbulence. This turbulence is magnified by the aperture. Perfect daytime 'seeing" only occurs about 1% of the time. Off-axis reduces the aperture and increases the focal length thus reducing the turbulent effects. We recommend off-axis for 10" and larger telescopes. The solar image is not darker with reduced aperture as we allow for this in the coating density. When viewing through the eyepiece, the field of view is not reduced: it looks the same as full aperture. If full aperture for 10"+ is still preferred for better resolution, it can be stopped down using a simple mask as conditions dictate.
mounting:
The inside of the cell will be lined with felt or unlined depending on the telescope brand and aperture. If your filter is too loose, it can be custom fitted using felt or tape on inside of cell. The filter should not fit too tightly or the optical surface may be distorted due to stress on the cell. If you have purchased an un-mounted filter and will be mounting it in your own cell, be sure to mount it in such a way as to allow for thermal expansion and contraction. The glass should not be firmly cemented or clamped within the cell or holder.
Please note each filter will be shipped with strips of Velcro, which should be used to secure the filter to the telescope for added safety
If you do not have a solar filter for your finder-scope, keep it covered. Looking through the finder-scope at the sun without a proper filter can damage your eye in a fraction of a second. With a little practice you can obtain a close alignment by moving your tube assembly until the smallest shadow of the tube assembly is cast behind you.
Filters by TYPE:
