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.

Observe a solar eclipse or sunspots with enhanced clarity with the AstroZap Baader Film Solar Filter! Assembled in Germany, this filter has been expertly crafted using Baader AstroSolar film, one of the most renowned names in solar astronomy. Approved by the National Bureau of Standards for eye safety, the AstroZap solar filter will protect your eyes from the Sun's harmful rays. This solar filter is designed for telescopes with an outer diameter of 165 mm to 175 mm.

Astrozap mounts the AstroSolar film in an aluminum cell. To install, you simply slide the filter cell over the end of your telescope and tighten the three thumbscrews so that the filter is firmly attached to your telescope.  With the filter securely in place, you can look at the Sun through a standard eyepiece.  Just remember not to look through your finderscope unless it has its own little filter installed!  Most observers remove their finder altogether so as not to be tempted in the first place since it is relatively easy to center the Sun in your eyepiece once you've learned a trick or two.

When viewed through an Astrozap solar filter,  the Sun appears neutral white. Other films and some glass filters produce a blurry bluish or reddish solar image, thereby cutting out 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.

Due to its neutral color balance, the use of an Astrozap Baader Solar Filter enables the use of various color (or interference) filters, allowing the observer to concentrate on certain spectral passbands for investigations of different layers within the solar "atmosphere".

Eye safety

AstroSolar™ is essentially free from pinholes, since - other than with even the most expensive glass filters - it is coated on both sides so that the chance of two pinholes overlapping each other is extremely faint. Pinholes do appear, but to 1 out of 10000 only in optical density 2.5! Baader AstroSolar™ safety film has been approved for eye safety by the National Bureau of Standards in Germany, the PTB. Unlike any other Solar Filter on the market, AstroSolar™ is CE-tested according to EG-Norm 89/686 and EN 169/92 ( notified body 0196). All processes connected to this product have been thoroughly tested. Coatings are inspected constantly for consistency to ensure your eye safety!

Sizing your solar filter

Each solar filter is designated in two ways—by the typical telescope or aperture it was designed for, and by the outside diameter range of the telescope it will fit.  Before you order your solar filter, take a minute and measure the outside diameter (OD) of your telescope so that you can be sure you are ordering the right one.  Each filter has 10mm of wiggle room.  Three thumbscrews are provided to snug up the fit.  

Once your solar filter arrives, slip it over the end of your scope and tighten the thumbscrews to make sure it fits properly.  This is important, as an ill-fitting solar filter is not something you want to mess around with.  If the filter does not fit, or you have any other concerns, contact our sales department and we will work with you to solve the problem.  Don't wait until that once-in-a-lifetime solar eclipse to find out your solar filter doesn't fit!