Important. Never view the Sun without a suitable Solar Filter! Solar observing can be dangerous and can be hazardous to eyesight.
I purchased a sheet of Baader astro solar film to try my hand at some white light solar observing and imaging and along with a friend have been playing around with different ways to mount it to my scope safely and effectively.
Please keep in mind there are 2 different filter densities available ND3.8 PhotoFilm and ND5.0 Safety Film. The ND3.8 PhotoFilm is not intended for visual observation. It is only for use with telescopes for high magnification photographic work. The ND5.0 Safety Film is of a higher density and is suitable for observational work and photographic use, it is also a lot cheaper than the ND3.8 so please make sure you purchase the correct film. As I wanted to do both visual and imaging I opted for the ND5.0. I decided to make this "how to" to show you, the reader how we went about making a simple filter attachment for the small 40mm aperture hole on the front of my 150P using some ply wood, glue and a few screws.
To start I cut 3 75mm circles out of some 6mm ply wood
As an alternative you could use thicker ply wood but this is all I had in the store.
I then cut 46mm holes through the 3 75mm circles.
I then glued 2 of the doughnut's together using contact adhesive to give me the required depth (here you could use thicker ply if available negating the need for glue) and drilled 3 pilot holes in the 3rd doughnut.
This left me with 2 doughnuts. 1 at 6mm depth with the pilot holes and the other 12mm deep.
Using the doughnuts as a template I cut a square of solar film large enough to cover the full 75mm diameter
Sandwiching the solar film between the 2 doughnuts I screwed the top piece right through the film and into the wood behind and trimmed of the excess solar film
I had to cut a notch out of the filter to allow for the raised lip around my scope end cover. This allowed the filter to sit over the 40mm hole flat
And here is the finished article. The 46mm internal diameter ensures a nice snug and tight fit over the hole. I will have to keep an eye on the fit as it may become loose over time through use and I’m looking at perhaps making a MkII out of nylon. Another safety feature I’m also considering is a bolt that runs right through the filter and end cover so the whole lot is bolted together.
If you decide to have a go at making one yourself you do so at your own risk. You need to ensure the filter is checked for pin holes or any damage before every use. I do this by shining a bright torch through the filter first and if that’s ok ill hold it up to the sun and check the whole surface of the filter
Here are a couple of images I have taken to date using this filter. The first showing some sunspot groups and the other shows the transit of Venus
Sunday March 16th saw the shadows of Io and Ganymede on the disc of Jupiter at the same time. A few of the Worthing Astronomers and I headed down to Worthing seafront and set up on the promenade to capture this event
The evening started really well with lots of frames being captured in the build up to the double transit which started at 22:22. Almost unbelievably at 22:10 my Battery started to die (My 17Ah battery is no longer adequate). Fortunately I was lent a power supply just in time to capture some frames that I stacked into a half decent image. I have achieved better with the little SPC900 before but I think the power failure and the rush to maintain my tracking didn't help
This is 1600 frames taken using my 150P and the Phillips SPC900 aligned and stacked in Registax 6