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DIY Solar Filter

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Just thought I'd share my latest project with you.

As this relates to observing the sun.


And now that's out the way.

Rather than take the traditional route of cutting out some cardboard tubes and using lots of sellotape, I decided on a different approach.

My scope of choice for solar observing is going to be my William Optics Megrez 72

Here's the parts list

Baader Genuine Solar Filter sheet x 1

Platic food container x 3

Double sided tape

M6 Plastic nut and bolt x 3

Black PVC tape

Some Araldite

First off, the preparation of the food tubs.

You need three food tubs, one to secure the filter and hold the solar filter sheet in place, one to locate over the top of the filter and one for storage to prevent the solar filter getting damaged.

Take a food tub and remove the inner circle from the base


Remove the Inner circle from underneath with a craft knife and file smooth.


Cover the outer edge with black pvc tape and drill (bore out) three equidistant holes to take a M6 platic bolt

Secure a plastic nut over each hole with Araldite or similar strong glue and leave to dry overnight.

Ensure you keep the bolt in the nut incase any of the glue seeps in while drying. (this also helps keep the nut in place)


When dry, place some double sided tape around the edge of the tub


At this point we need to measure the filter paper. I found that half the sheet was the right amount, if you are going to try this, please measure first before cutting as we all know how expensive this stuff is !!

Cut the filter by sandwiching it between two sheets of card.

Remove the double sided tape backing paper.

IMPORTANT...The solar filter has a tissue protective sheet AND a protective film, remember to remove both.

Secure the filter over the tub and press around the edge onto the double sided tape.


It doesn't need to be perfectly taught, in fact it shouldn't have excess tension applied to it.

Once it is all pressed down, secure the rough edges with a layer of pvc tape.


Now take a second food tub and remove the bottom circle as before.

Place over the top of the first tub and secure with a further layer of pvc tape.

This covers up the edge of the solar filter and protects the outer edge.

You can now fit this onto your scope and secure with the tree bolts


You now have a finished filter.


To store, use the third food tub and place over the end, take one of the three unused lids, cut out three lips to avoid the plastic nuts and secure to top of filter.



Total cost

3 food tubs @ 50p each £1.50

Filter paper 1 sheet £20

M6 nut and bolt x5 £2

PVC tape

double sided tape


Total £23.50 if you already have tape and glue.

All comments welcomed and as before....PLEASE TAKE CARE WHEN OBSERVING THE SUN



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Looks good... Love the fact that you have emphasised the need for safety!

let's hope you get a chance to try it soon

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Looks good and keeps the Baader material a safe distance from fingers which can only be a good thing.

My only concern is the security of the nuts - polythene and nylon are notoriously bad materials for gluing (they 'leach' and break the glue bond) so check them regularly as one day they may just fall off! If the materials are really roughened up first it would probably help. There are specific adhesives but they're expensive.

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thanks , good point.

I did roughen the surfaces before applying but will check each time.

I suppose I could always look at cutting a hole in a spare lid the same size as the dew shield on the megrez?

The dew shield actually has grooves machined into it and the bolts actually line up with one of them.

Thanks for the observation


Edited by smudgeball

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Neat, I will need to nick one of Mrs Baggy cake boxes...

Below is my attempt. I have a Celestron 6SE which has a reasonably large barrel diameter on the OTA.

I got a suitably sized box and on the rear drew two cirlcles. One the diameter of the barrel and the other 1 cm smaller. Cut out the smaller diameter and then cut radial lines around so I had a lot of small flaps. These provide the grip and some stability to the box when on the 'scope.

For the front I cut another circle equal to the optical diameter of the corrector plate and then used duct tape (much stronger than other adhesive tapes) to secure the Baader film.

I check the box before I use it to make sure there are no holes.

Filter 1

Filter 2

Sun Jan 9 2013

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Got to try mine out yesterday morning.

Works just fine.

A very strange feeling the first time using it.

But perfectly safe and great view through the megrez.

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Would a 10 stop ND camera filter work? For photo purposes.

Not safe. A ND10 filter won't reject enough sunlight as a proper Solar Filter would; and you'll risk damaging your camera chip.

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