Hello my name is Simon, welcome to my workshop something different this week, I'm going to
be making a solar filter for my telescope for observing sunspots on the sun. Lets get
started.
Now I should say at the outset, that even with the unaided eye you can damage your eyesight
if you look at the Sun, so If you have never built a solar filter, I'd suggest getting
in touch with Lyn at the British Astronomical Association's Solar section. I'll leave a
link in the description and a link to some basic solar observation safety tips, and remember
just as in a workshop, your safety is your responsibility.
I've been an amateur astronomer for about 30 years and observing the Sun, on and off
for much of that period, I've had many solar filters in that time and my current Solar
set-up is a small refractor with a Herschel wedge, however I was curious to see if using
my big telescope and some solar safety film would give better results than the fancy set-up
I usually use.
The cells for these filters are usually made from cardboard, but having just made a circle
cutting jig for my router table I thought I'd have a go making a wooden one.
I start by rough cutting a circle out of 5mm, that's quarter of an inch ply, using my band
saw then complete the job using the router table circle cutting jig.
Then, using the jig, I cut out the centre to form a ring, it's important to note that
when cutting an internal circle using the jig, you shouldn't complete the circle, as
the jig is attached to it, so the last little bit has to be completed by hand and
then sanded.
Then, again, using the 5mm ply, I cut another piece on the band-saw, which is still my favourite
tool in the workshop.
If you are interested in how I added dust collection to this 40 year old machine or
how I restored it using a 3D printer to replace the perished plastic parts I'll leave links
in the video description.
and while I'm talking about my videos, if you are enjoying this then please consider
leaving a thumbs up and subscribing, knowing people are enjoying the videos keeps me making
them.
I then use the circle cutting jig to tidy everything up,
The jig is such a simple tool but lovely to use, if you haven't watched the build video
why not do that next, you can find a link to my router table accessories playlist in
the video description.
I then cut the centre out, remembering not to complete the circle as the jig is connected
to it.
There's then a little bit of sanding to prepare the pieces for painting and I drill the holes
that will later be used to fix the tube clamps to the filter and elongate these holes to
allow for some adjustment.
I now had to make 4 tube clamps, using 3/4 inch (that's 18mm) ply, these have a curve
cut into them the same diameter as the tube of the telescope so will grip the sides of
the telescope to ensure the filter can't be blown off by a gust of wind, which would obviously
be disastrous.
...here are all the components just prior to assembly and painting, the last time i
made one of these i made the filter cell out of cardboard, so this is really very over
engineered...
I fit some m6 threaded inserts into the tube clamps.
When doing this I get a little bit of blow-out on a few of the clamps so I find the chips
and glue them back in place.
... so i should pay more attention to the wood grain on the top surface because this
piece didn't get any blow out and the wood grain is going in this direction, i think
because there is a bit more wood here it hasn't - it's been able to hold and hasn't blown
out - where as the other 3 pieces the wood grain was going in this direction on the top
surface and here or over here or both blew out which is why i had to glue them up...
I now give everything a coat of water-based, satin black, exterior paint.
While the paint is drying I make some m6 thumb screws, using some thread I had left over
from a previous project, first cutting it to size and then fitting them to some knobs
I'd salvaged.
and then I finish painting the other side.
Now I don't want to scratch my expensive telescope, so I add some velvet to the face of the clamps,
you might recognise this velvet from the guitar stand build, that I did a few weeks ago.
I now cover the ring with double sided tape, this will hold the solar safety film in place.
and I use my 30 year old, home-made craft knife and scribe to peel the back off the
tape and stick the frame to the safety film, I then cut off the excess film, note this
isn't tin foil, it is specialist Solar Safety Film, it reduces the total light entering
the telescope by 99.999%
and apply double sided tape to the ring and sandwich the film between the two pieces of
wood.
and when fitting it, it is important not to stretch the film as it will result in a poor
quality image.
Then I attach the clamps.
Here's my telescope, the little refractor on the top is my solar scope, and the white
bot at the end of the solar scope, is the Baader Herschel wedge which I normally use
for white light imaging of the sun. With my New solar filter I'm going to compare the
different solar imaging using the big telescope with solar filter verses the small William
optics refractor using the Herschel wedge.
It's sunny today, but the conditions are not great, there's high cirrus clouds passing
in front of the Sun, this will make getting a good image difficult, but I can't wait to
give it a go and the forecast suggests clouds for the next couple of weeks so this is my
only chance before I publish the video to get some solar images.
I quickly capture some video, that black dot is a sun spot, larger than the Earth, I process
the video to produce the final image, which is not as good as I'd like but given the conditions
is very acceptable.
until I get good conditions I won't be able to compare it with my fancy set-up, but first
impressions suggest I should be able to get some good images with this set-up.
Well thanks for watching this slightly different video, I hope you enjoyed it enough to give
it a thumbs-up and subscribe, if you have any questions don't hesitate to leave them
in the comments and I'll see you in my next video, by for now.