DabsonAstronomy.Com

Solar Filter Project

How could I find a way to further my astronomy habit during the daylight?  I concluded I had to acquire a solar filter for my 120mm refractor.  I priced these on the local UK economy.  With the exchange rate it would cost more than $100.  To expensive for me, so I started constructing my own. 

 

I completed my solar filter in one day with the following materials:

 

· Fiber board

· Jig saw

· Compass (circle drawing kind)

· Wooden knob

· Flat black spray paint.

· Baader solar film

· Glue stick

 

All of the materials listed above were scrap from other projects with the exception of the Baader solar film sheet.  This cost me roughly $25.

Determine size

 

This was the easy part.  I traced the opening of my dew shield onto paper.  I cut out the circle and found the exact center by folding it in half twice. 

 

I measured this with a compass and transferred it to the fiberboard.  Then I reduced this circle by 1/2 inch and made a concentric circle inside the first.  This resulted in the first layer of the filter.

 

I then transferred this same size circle to a separate section of the fiber board.  I expanded the circle by 1” and made concentric circle outside the second circle.  This resulted in the second layer of the filter.

 

 

 

 

Cut out both layers of the filter

 

I cut out both layers.  Since you don’t want to cut through the edges of either layer start by drilling a hole with a spade bit inside both inner circles.  Use a jigsaw to cut out both layers.

 

 

 

 

 

Test fit the both layers

 

If you did the measurements correctly the inner circle of both layers should be the same.  Sand both parts with a fine grit sand paper.  I painted both parts with Krylon Ultra Flat black paint.  I did not want any reflections spoiling the view.

 

 

 

 

 

Insert the Baader solar film

 

Cut the solar film to size using scissors.  Glue to inside side of the larger circle, completely covering the opening.  Then glue the smaller part on top, sandwiching the filter between the layers of the filter.  (Sorry no picture, I forgot during this step.)

 

 

 

 

Finished product

 

Here you can see the finished product.  This should give me nice views.  It is not an especially tight fit, gravity will keep it in place.  The external side of the filter has a large enough lip to stop any unwanted light.

 

 

 

 

Finished product

 

Here is one I made for my son’s 130mm newt.  Same basic principle.  I just used a hole saw to make the outside layer inner circle.  Make sure to use a hole saw that will fit between the spiders of the mirror secondary holder.  This will eliminate spikes from the spider arms.