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Spectrum Full Aperture Glass Solar Filter for 86 mm - 92 mm OD Telescopes - ST375G

To ensure that the solar filter you buy will fit properly, please take a few moments and measure the outside diameter of your telescope, spotting scope or binoculars before you order. Remember, the solar filter needs to fit snugly around the front of the tube assembly that holds the optics. If the filter is slightly larger than its diameter, the filter can be made to fit by the addition of self-stick felt spacers to the inside of the cell. However, if the filter is too small it will not fit, and that would be a shame. So please, measure before you order. Thanks.

Spectrum Glass Solar Filter for 86 mm - 92 mm OD Telescopes

This Spectrum Full Aperture Glass Solar Filter fits the following instruments:

  • Celestron FirstScope 60 AZ & EQ, 80 EQ
  • Meade ETX-60AT, ETX-70AT
  • Orion Observer 60 AZ & EQ
  • TeleVue 76, Pronto
  • Vixen A80Mf, A80SSWT, ED81SWT

The Spectrum Full Aperture Glass Solar Filter with 76 mm inside diameter allows the greatest possible amount of light pass through to your optical device, enabling a safe method for directly viewing the sun. Your telescope's entire aperture is utilized when viewing for maximum daylight observing quality with extremely reduced atmospheric vulnerability, which can be countered by placing a mask over the filter for sufficient aperture decrease.

When directly viewed using this durable premium solar filter, the sun will appear in a natural organic yellowish-orange state. This filter features a centered aluminum cell, felt padding, and nylon thumb screws for installing over the end of the telescope. It is designed using hand-picked glass of superb quality with reflective coatings that are meticulously inspected.

This filter arrives in a foam-lined box with plastic wrapping to prevent any possible damage during shipping. The box is also useful as a means of storing the filter between uses. Complete instructions detailing correct use and maintenance are included.

Spectrum ST375G Full Aperture Glass Solar Filter Specifications

  • Inside Diameter: 3.75" (95 mm)
  • Clear Aperture Diameter: 3.15" (80 mm)
  • Fits instruments with an outside diameter range of 3.375" - 3.625" (86 mm - 92 mm)

In order to assure a proper fit, please be sure to measure the outside diameter of your telescope before committing to purchase a specific solar filter as telescope specifications may be modified with subsequent versions due to re-designs, etc.

What About Your Finderscope?

Adding this solar filter to your telescope will adequately filter the light coming through your focuser, but have you considered what you’ll do about your finder scope?

Here are some suggestions for dealing with your finder that will assure you do not damage your eyes (or anyone else’s) by looking at the Sun through your telescope’s unfiltered finder:

  • Remove Your Finder. Ditching your finderscope when solar viewing will remove the possibility of someone accidentally looking through it to spot the Sun. Of course, not having a finder makes centering the Sun in your eyepiece more difficult, but with practice, it can be done. Set the mount down so the telescope is pointing in the direction of the Sun. Put the main solar filter on so you can check your progress, and then move the telescope around until it casts a shadow that produces a nice, sharp silhouette of the scope. The OTA will look circular. Now move your telescope up or down with your hand controller, slow motion controls, or very carefully by hand if required while looking through the eyepiece. You will not get a warning when you are close, but you should be able to align with the Sun using this method. Practice ahead of time before any big event, like an eclipse, to make sure you’ve got the process down.
  • Filter Your Optical Finder. This solution is not recommended for a reflex or red dot finder since it is too easy to accidentally look around the window. If you have one of these finders we recommend you either remove it or replace it with a dedicated solar finder (see below).

    To make your optical finderscope safe for solar viewing you’ll need to buy a piece of Baader Solar Film for Visual Use. This film comes in different size sheets and cuts easily with scissors, allowing you to make your own filter. You can go super low-tech and use a rubber band to hold a piece of the film firmly around the finder or you can get fancy and build your own slip-on solar filter. However you attach the solar film, you need to make sure there are no light leaks at all and that it doesn’t accidentally fall off when you move your telescope around. Any unused film can store flat between two pieces of cardboard and will keep for years. It is nice to have around, just in case of a solar emergency :-)

  • Buy a Dedicated Solar Finder. Check out the Tele Vue Sol-Searcher Solar Finder. This special finder can only be used when observing the Sun, but it works very well. The Sol-Searcher is reasonably priced and can be attached to your telescope with Velcro or with #10-32 screws (user supplied).