Home Made Solar Filter

June 25 2011
A couple of days ago I decided to buy some Baader Solar Film to make a solar filter for my scope. As the nights are far to short and light at this time of year I thought I would try and get more use of my kit during daylight hours during the summer months.
Today I made the filter cell, which would be used infront of the smaller aperture revealed on my scope cap. This is for two main reasons. Firstly to reduce the aperture down giving better contrast, this converts my scope into an f24 instead of the usual f4.8. Secondly the size of the film was not large enough to cover the complete aperture of the scope.
The filter cell was made in twi parts. The first part was made from cutting four pieces of mountboard  into 70 x 70mm squares. Out of the centre of these squares I cut an aperture to suit the scopes cover. Next I cut out two 100 x 100mm squares with the same central aperture. All these pieces were glued together and a strip of thin card was used to line the centre.

© Lee Diggle 2011
This gives me something that I can slot onto the smaller aperture hole on my scopes cap. For extra security this can be held in place with some tap, as will the scope cap itself to prevent it slipping off.
The next stage was to cut two further squares each one 100 x 100mm in size. These two pieces will have a central, square, aperture cut out of them measuring 70 x 70mm. These two pieces will be used to sandwich the solar film.
To do this the solar film was placed between two pieces of paper, onto which one of them had a 100 x 100mm square marked onto it. This was then cut out to allow the solar film to be cut without causing any finger marks or scratches.
Double sided tape was then added to each of the two pieces of card. One is then gently dropped onto the solar film and firmly pressed home. It is important not to stretch the film otherwise it could not perform properly. This assembly is then turned over and other piece of card is then added sealing the solar film. The edge of the complete holder are then sealed with tape.

© Lee Diggle 2011
As finger prints can contain acid, they can degrade the solar film over time. As such I also made a pouch to keep the filter in when not in use.
When used the square holder, containing the solar film, will be clipped to the aperture sleeve and secured in place with some tape.

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