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Baader ASSF 100 AstroSolar Spotter Solar Filter - 100 mm - ASSF-100

SKU: BAD-ASSF-100
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.

Baader AstroSolar White Light Solar Filters

The world's finest solar filter material, Baader AstroSolar Safety Film, is now available in a complete range of high-quality mounted Baader Solar Filters. Their innovative design and construction enables each filter to fit a wide range of instruments…from telescopes, to spotting scopes and camera Lenses, to binoculars. Each filter is precisely mounted at the factory onto special cells, guaranteeing a stress-free mounting that, unlike other mounted solar film filters, preserves the full optical quality of the Baader AstroSolar film.

Many ready-made filters stretch the filter material like a drumhead in order to make it look like a piece of glass. While it might look more pleasing to the untrained eye, the stretching process absolutely destroys the image quality, rendering the film useless for high magnification work. Baader AstroSolar is mounted entirely stress free in order to perform like a high precision plane-optical window; in other words, AstroSolar film must show slight ripples! When the film is put under stress by an improper cell mount its optical quality is degraded and it then performs just like a common glass filter made of untreated float glass.

With Baader Planetarium AstroSolar™, the color of the Sun is displayed as neutral white, which is its true color. Other films and most glass filters produce a blurry bluish, yellow-orange, or reddish Solar image, thereby cutting part of the spectrum. Especially with an orange sun, it is very hard to see faculae regions which are visible predominantly in the blue part of the spectrum.

Baader ASSF 100 mm Spotter AstroSolar Filter
Fits 105-120 mm OD & 131-146 mm ID
Telescopes, Spotting Scopes & Camera Lenses

Baader ASSF AstroSolar Solar Filters are designed to fit a wide variety of spotting scopes, smaller refractor telescopes using magnifications of up to 120X, and camera lenses. The Baader AstroSolar Safety Film (ND 5.0) is mounted at the factory onto a clear white, IR-rejecting plastic ring that has a similar thermal expansion coefficient to minimize thermal stress on the film. Raised edges along the inner and outer circumference protect the solar film from contact with any sharp metal edges. This ring is then attached to the aluminum front frame of the filter, providing a very rigid and stable filter cell.

Each Baader AstroSolar Filter comes with two different lengths of centering bolts (the 100 mm comes with 13 mm & 24 mm) to give you leeway for mounting on your telescope, spotting scope, or camera lens. These centering bolts, with their non-slip rubber facing, are used to make contact along the outside, or if feasible, the inside diameter of your instrument. Non-rotating sliding aluminum fasteners hold the centering bolts. Additional Phillips head screws are integrated into the sliding fasteners so that, if you wish, you can use a screwdriver to fasten the centering bolts firmly into place. An indexing system is in place to allow repeatable and fast adjustments of the filter cell if you use it on more than one instrument.

You will also receive three security straps which allows you to secure the position of the filter with Velcro-adhesive pads. This extra security feature ensures that the filter will stay put even in windy conditions.

Baader ASSF 100 mm Solar Filter Specifications

  • Best for Apertures: 90 mm - 110 mm
  • Filter Aperture: 100 mm or 3.94”
  • Outer Cell Diameter: 160 mm
  • Net Weight: 93 grams or 3.3 ounces
  • ID Clamping Range with 13 mm Bolt: 131 mm - 146 mm
  • OD Clamping Range with 13 mm Bolt: 105 mm - 120 mm

Check out the Baader Solar Filter Clamping Ranges for more information on filter installation, 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).