Making an Inexpensive Filter Cell for
BAADER AstroSolar™ Material
PLEASE READ AND FOLLOW ALL SAFETY PRECAUTIONS AND INSTRUCTIONS.
Failure to do so could result in permanent blindness or other serious damage to your eyes.
The film must be mounted reasonably flat and free of any tension. It is more desirable to have slight wrinkles
than to stretch the material, which will damage the optical quality and possibly the coatings. Wrinkles, creases
and folds in the material are normal and will not affect the function and performance in any way. When mounted
carefully, AstroSolar™ Film can reach the quality levels of truly precision-made, diffraction-limited glass filters (notto be confused with inferior, inexpensive glass filters made ofthin, machine-polished plate glass).

The "Cylinder"
Construct a cylinder out of posterboard to fit over the front
aperture of your telescope or dewcap. Start by cutting several
long strips of the posterboard approximately 2” wide and wrap
these around the lens cell or dewcap until you have 3 or 4 layers.
Glue the layers to each other to form a thick, sturdy cylinder
approximately 1/4” thick (do not glue this to the scope, please!).
The finished cylinder should fit snug on the scope yet slide easily on and off. The fit is very important – too tightand you can’t get the filter on and off without damaging it – too loose and an accidental bump or a gust of wind
could knock the filter off.
Hint: For small aperture telescopes, you might be able to findjust the right-sized cardboard tube to fit over the aperture.
Simply cut off 2” and use that as your cylinder. If the tube isslightly too large, use an adhesive felt liner or cork pads to makeit fit snuggly.

The "Filter Cell"
Cut out two rings of posterboard or cardboard with the outer
diameters equal to or slightly larger than the outside diameter ofyour fabricated cylinder. The inner diameter should correspondto the actual aperture of your telescope (8” or smaller; otherwise, see off-axis cell below). On one side of eachring near the outer edge, attach a number of pieces of double-sided tape.
Now comes the tricky part – how to get the AstroSolar™ film onto the taped ring without wrinkles or ripples.
[Note: there is a protective material over one side of the AstroSolar™ film that must be removed before
proceeding. It may be either clear or white in color.] The film must not be scratched. So, put one sheet ofKleenex™ (or other soft tissue) onto a flat table. Tape the tissue onto the table so that it is stretched out evenly
and cannot move. Now put a square piece of AstroSolar™ material (slightly larger that the outer diameter of thecardboard rings) onto the piece of soft tissue. Do not tape the film and do not stretch it! Just let it rest relaxed andflat on the tissue.
Take one of the cardboard rings with the sticky tape face down andlower it straight down onto the film until the entire ring has madecontact with the film. Turn this assembly around and tape the otherring onto the opposite side of the film. Now you can trim away any
overhanging parts of the film. Your AstroSolar™ film should now be
free from strain and wrinkles, sandwiched between the two
cardboard rings. Finally, glue this “filter cell” assembly onto yourprefabricated “cylinder.” Lift the filter up to the sky and inspect thecell for light leaks prior to using it on your telescope or binoculars.
You must be sure that absolutely no unfiltered light gets
through. Use a black felt-tip marker on the inside of the filter (foraesthetic appearance) to cover tiny pinholes in the filter material.

Now your “do-it -yourself” filter is ready. Enjoy!

Special tip for owners of large aperture reflecting
telescopes
When covering a larger Newtonian or Schmidt-Cassegrain
Telescope (9”-10” or larger) for solar observation, it may be that"Less is More"! Do not try to make a filter as large as thetelescope aperture. The bigger aperture will be greatly affectedby air turbulence, which can ruin fine detail. We suggest that you
produce an off-axis filter cell, to observe the sun with a smaller(but much improved) telescope.

Safely Storing Your Filter
It is very important to store your filter safely so that it will not bedamaged. If the filter is small enough, we suggest that you use aplastic food storage container with a cover. In addition toprotecting the filter material, it will keep the cardboard material
from becoming wet and soft.

Cleaning Your Filter
Please refer to separate document: “Cleaning AstroSolar™ Film” for instructions.

PLEASE OBSERVE THE FOLLOWING SAFETY PRECAUTIONS WITH
EACH AND EVERY SOLAR OBSERVATION!
Failure to do so could result in permanent blindness or other serious
damage to your eyes!
Before using your solar filter, check the filter’s fit and integrity. If your filter is damaged in any way,
it must be replaced. DO NOT use if the AstroSolar™ material has any holes or the cell is weakened andwill not stay on the telescope.
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Slide the filter on and off your telescope and be sure that it won’t get knocked off by accident or
get blown off by a gust of wind.
We recommend that you tape the filter onto the telescope for added safety.
Make sure the filter cell and cylinder are still securely glued together.
Hold the filter up to the sky and look for any pinholes in the filter cell itself or light leakage wherethe filter cell and cylinder are glued together.
Tiny pinholes in the filter material can be covered on the inside with a black felt-tip marker.

 NEVER use the filter material at the eyepiece or anywhere else in the telescope’s optical path.

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The intensely concentrated light energy at the eyepiece will burn up the filter in less than a second. (Doyou remember burning leaves with a magnifying glass as a child?) The filter will ONLY work when
attached to the FRONT aperture of a refractor objective, in FRONT of the Schmidt plate (SchmidtCassegrain telescope) or in FRONT of the tube of a Newtonian telescope.
If you use a binocular, protect both objectives with a filter.
Be sure that the viewfinder of your telescope is properly covered, either with a solar filter made as
described above or with the original dust cover. Unprotected views through your finderscope would havethe same catastrophic consequences for your eyes as a look through the main telescope itself!
A filter made of AstroSolar™ filter material is relatively resistant to breakage in comparison to a glassfilter. However, care should be taken with sharp pointed objects. A punctured filter should be thrownaway and replaced with a new one (same as with a cracked glass filter).
Emphasize the importance of safety to those observing with you, especially children. Intentionally
removing or damaging the filter can endanger their eyesight. This is no place for jokes. Never leave thetelescope outside unattended during the daytime!

Revised: July 2, 2012