New Scope

Well, not really.

My 120mm f/8.3 refractor is my main scope for the sun and moon,.  Recently I have been making some aperture masks, 100mm, 80mm and 60mm, this weekend I made a 50mm mask that turns the scope into a 50mm f/20.

Today, I took it out to observe the sun, using a Herschel wedge and Baader Solar Continuum filter I attached the 50mm mask.  The view was excellent, the sunspot 2803 was resolved into a trio of spots with plenty of detail when the view was magnified.  I removed the mask and observed again at 120mm, the view was different insomuch as there was more turbulence around the limb of the sun, when I put the 50mm back on this turbulence was greatly diminished, there was a small improvement in detail of the spots. not so much as I had expected going from 120mm to 50mm.

If the weather behaves itself I will go out tonight and conduct the same test on the moon.  One aspect I am expecting is a lessening of the slight green fringe around the lunar limb that is obvious with an achromat.

I now have five scopes, four of them for the cost of a couple of boxes of cereal.

Paul 

Hi Paul,

Very many thanks for the information on the aperture masks. I've never heard of them before, but they seem to have made a big difference. I take it that they are a DIY job. Shame the clouds were out tonight, as I would have loved to hear how you got with the Moon. 

Clear skies,
Darren.

Hi all

The moon came out to play last night, and it gave me an opportunity to see how the 50mm aperture mask performed.

When using the full 120mm aperture, the moon, two days shy of full, had that uncomfortable feeling, when it is just a little too bright and strains the eyes.  There was slight colour fringing around the limb, nothing too serious,
Popping in the 50mm, the difference was obvious, the light had been cut down dramatically, it was now very comfortable, and the CA was absent, the scope is now operating at f/20, so this is to be expected.

With 120mm or 50mm, there was very little difference in the features that I could observe, I guess going down 70mm in aperture is the equivalent of using an ND filter, a lot of the light is cut out but features are still obvious.

I believe that I shall be using the 50mm on those nights when the moon is around full and larger apertures when when the moon displays crescent and gibbous phases.

For the sun, I will stick with the 50mm, it just looks more pleasing.

Paul 

Fascinating results from those aperture masks...very well done!

Like you I was out looking at the Moon last night. However, as I failed to locate my Moon filter I didn't spend too long observing it - as you so rightly pointed out it had that uncomfortable feeling. 

So, if you're planning on ramping up production of your aperture masks line through lockdown, and cornering a section of the market for those who lose Moon filters, you've your first customer right here  

Clear skies, 

Darren.