AstroZap Visual Baader Solar Filter for 235 mm - 242 mm OD Telescopes

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.

AstroZap Baader Solar Filter for 235 mm - 242 mm OD Telescopes

This Baader AstroSolar™ Filter cell is powder coated white and fits telescopes with a 235 mm to 242 mm outside diameter range. The cell is constructed from lightweight 18Ga. aluminum. Nylon thumbscrews and heavy-duty threaded inserts secure a proper fit. Please remember to measure the outside diameter of your optical tube before going through with your order.

AstroZap Visual Baader Solar Filters

The Sun appears in colorless white with Baader AstroSolar™ safety film. Other films as well as some glass filters generate a blurry bluish or reddish Solar image, thereby reducing the spectrum. With an orange sun especially, it can be difficult to locate faculae regions which are detectable primarily in the blue spectral region.

The AstroSolar film's neutral color balance enables the employment of an assortment of color (or interference) filters to let the viewer hone in on specific spectral passbands in order to investigate varying layers in the solar "atmosphere."

Because AstroSolar™ film is coated on both sides, it is essentially free from pinholes. The probability of encountering two overlapping pinholes is highly unlikely. There are glass filters on the market that don't have coatings on each side, even some of the more costly ones. Pinholes do occur, but in only 1 out of 10,000 and only in optical density 2.5! Baader AstroSolar™ safety film has been certified safe for direct solar viewing by the National Bureau of Standards in Germany, the PTB. AstroSolar™ filters are CE-tested according to EG-Norm 89/686 and EN 169/92 (notified body 0196), unlike other available solar filters. All procedures associated with this filter have been examined thoroughly. Coatings are constantly tested for consistenty to ensure a safe solar viewing experience!

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).