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Spectrum Full Aperture Glass Solar Filter for 137 mm - 143 mm OD Telescopes - ST575G

SKU: SPR-ST575G
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 137 mm - 143 mm OD Telescopes


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

  • Celestron FirstScope 102
  • Meade 4500, DS-127, 4" APO, DS2000, DS2114, Polaris DS 114
  • Orion AstroView 120/120ST, SkyView Pro 120, StarBlast, StarMax 127, SkyView Pro 127, Apex 127
  • Stellarvue SV4, SV102T
  • Takahashi FS-102, 106 N, FSQ-106
  • Vixen 102
  • William Optics ZS110 APO, ZenithStar 110 w/Dew Shield, FLT 110 APO, Megrez 110


This 146 mm ID Full Aperture Glass Solar Filter enables safe direct solar observation by allowing the greatest possible quantity of light pass through to your telescope. It uses the full aperture of your telescope for maximum daylight viewing capacity with limited atmospheric fluctuations. In case atmospheric fluctuations do occur, a mask can be installed over the filter for effective aperture reduction.

This sturdy premium solar filter has been designed using superb quality, hand-selected glass with reflective coatings that have been extensively tested. The aluminum cell is centered and fixes to the end of the telescope with the help of felt padding and nylon thumb screws. The sun appears in its organic yellowish-orange state when viewed directly through a telescope with this filter attached.

To keep it from acquiring any damage in transit, the ST575G Solar Filter is wrapped in plastic and placed in a box lined with foam. In addition, this box offers a convenient storage method when not in use. Includes full instructions on how to correctly use and maintain your unit.

Spectrum ST575G Full Aperture Glass Solar Filter Specifications


  • Inside Diameter: 5.75" (146 mm)
  • Clear Aperture Diameter: 5" (127 mm)
  • Fits instruments with an outside diameter range of 5.375" - 5.625" (137 mm - 143 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).