Easy White Light Filter Cell

This guide is for a full aperture White Light Filter for a telescope or camera lens or even if you made 2 you could use them with binoculars.
If you have a central obstruction on the front objective like on a SCT or MAK, then you can either make a full aperture filter (maybe too bright, so for visual you only really need about a 1-2inch aperture) you could make the filter the same way but instead of covering the front with film, make the hole in the front card support smaller, and to one side (off set) for scopes or lenses with a central obstruction.

All you need is double sided tape, card and a piece of Baader film (they do 2 types, Visual which is ND5 which is for visual, and a photographic film which is ND3.8 which is ONLY for imaging, do not look through it and don't even look through a viewfinder on a camera when using it, the photo is I think only available in a roll and about 4 times the price of the A4 sheets sold for visual).

I am demonstrating this guide on a wide angle lens adapter for my DSLR (for another project to capture the movement of the Sun over a year, so need a White Light filter for the lens), but the same principle is used for telescopes.
Cut strips of card, you will need quite a few.

Out with the double sided tape again, and for the first ring just put a bit to make it a snug fit round the front lens.

For the next few strips I find it easier to put the double sided tape on to the card strips first then just wrap them round, you are trying to build up the thickness to allow the front filter to be attached.

Now the fun bit, when you have a good thick card ring, draw round it on another bit of card to make a ring to hold the baader film.

Using double sided tape carefully attach it to the ring.

The easiest way to stick the film on, is to put the film on a flat surface, remembering to remove the clear protective sheet and the tissue paper on the back, and lower the card ring onto it.
It does not have to be tight, as even crinkles won't make a difference to the view.

Trim the film to the outside of the ring, and again using double sided tape on the thick card ring top surface.

This is why the strips were used to build up a thick walled ring.

Peel of the backing of the tape and lower the front filter onto the ring.

Press down and nearly ready, to make it look a bit better and for double safety, I use a bit of duct tape, leave a bit of a overlap on the front and just wrap it round the ring.

Once done, carefully fold over the overlap to double secure the front card filter.

If the card ring is on a telescope it may be wider, so just use two bands of duct tape, and fold one over the front and one over the back.

Always advisable to put a sticker onto the filter so you know what film you used on it.

And job done, this one is for the DSLR wide angle lens, but the same can be used for a custom made telescope White Light Filter.

Before each viewing you MUST check the filter for pin holes, the best and safest way is to let the Sun reflect through the filter onto the floor or a bit of paper, and if there are any holes in it, there will be bright spots as the filter is letting through pure sun light, if it produces a dark shadow with no bright spots then it is working fine and can be put onto the scope and safely used.