Product FAQ

To find the right filter, type your telescope, spotting scope, or binoculars make and model into the search box at the top of the website, then click search. You will get a list of search results that match the search you entered. You may get more than one result because many model numbers and scope sizes overlap. Click on each of the results to find the right model for you. Be sure your telescope, spotting scope, or binoculars are listed in the list of models the item you are viewing will fit. If you do not find your telescope or other optical device, then you will need to measure the optical tube diameter of your telescope or other optical device to determine the best size filter to order.

1. The filter slips over the sky end of your optical tube. You must measure the outside diameter of your optical tube. To measure the diameter use a ruler, tape measurer, or caliper. You want to measure the widest distance across the end of your telescope. Measure from the outside of the casing on one side, across the center, to the outside of the casing on the other side.
2. Order the solar filter size that is just larger than your measurement. You are comparing your measurement with the solar filter inside diameter (ID).

For example: A measurement of 4" (102mm) across the end of the optical tube would require a solar filter with an inside diameter of 4.25” (114mm) because it is the size just larger than your measurement. Therefore you would order a solar filter with the part number of SF425.

Yes. All of our Glass & Thin Film Solar Filters are safe for unlimited visual use and photography. These filters block 99.999% of the sunlight and therefore are rated with a neutral density of 5.  Carefully handling and proper maintainance will ensure a long filter life.

You should be able to see sunspots, surface granulation, and of course a solar eclipse if present.

The heat and intense light is blocked before it enters the telescope. Your telescope may get warm from direct sunlight on the telescope but not from the small amount of visible light transmitted through the filter. Please read and understand instructions before use.

There are many thin films on the market today used for solar viewing. Some of them include Mylar, Baader, Black Polymer, etc. The thin film that we use for our filters is a black plastic polymer. It has a neutral density (ND) of 5 and therefore is safe for solar viewing. The sun is viewed as a sharp natural orange image, not blue or white. It is less expensive than coated glass filters.

An off axis solar filter blocks light into the telescope by only allowing light through a small portion of glass that is off center. By reducing the aperture, visibility of daytime atmospheric turbulence is reduced.  A full aperture filter allows the most light into the telescope because it allows the full aperture of your telescope to be viewed. This allows the best possible daytime viewing when there is minimal atmospheric turbulence. If turbulence is present a mask can be put over the end of the filter to effectively reduce the aperture. With a mask you can effectively change the aperture range to anything less than full aperture depending on the size of the mask.