Aperture Masks

Hi all

I was observing the sun this afternoon  with my 120mm f/8.3 refractor in white light.I
I have made two aperture masks to fit over the scope's dew shield, 100mm and 80mm.  Producing scopes of f/10 and f/12.5.  I believed that the view with the 80mm mask offered the best view, perhaps due to the longer focal length, the view just looked sharper.
Tonight I am going to observe the moon and planets using all three apertures, to compare and see how they perform.

Paul

While observing the Moon, Saturn, Jupiter and Mars last night, what I found was when I stepped down to 80mm, it dimmed the image, but it also cut down a lot of the purple halo that is common with the achromatic telescope.  I also found that it was easier to get a better focus and on Mars and Jupiter I was able to see more surface details because they were not being washed out.
When stepping down the aperture, I was turning a 120mm f/8.3 scope into100mm f/10 and 80mm f/12.5 scopes, and the changing to f/10 and f/12.5, really made a difference.
I am thinking of making a 70mm and 60mm mask, just to see what the performance will be.  Scopes operating at f/14.3 and f/16.7, that should be interesting

Paul. 

Hi Paul,

I very much liked reading about the results you achieved with the different masks. Congrats on the innovative approach, and it will be interesting to hear how you get on with 70mm and 60mm masks.

Clear skies,

Darren.