RE: [ATM] Low altitude dob

["Jerry" <wa4guu@verizon.net>]

Hello again John

My 12.5 inch can go to about -20 degrees so that I can watch beached whales
on the beach.

I should put a limit on it. Once an out of the blue high gust of wind caught
that thing and just whipped it around and down violently. The "clips" bent
but held the mirror in the cell. The clips clear the surface a couple of
hundredths of an inch. You might think that it couldn't develop that much
momentum in that distance but really it is how much momentum it got in that
whip and slam down before the sudden stop. Moral is to plan for more than
the expected. 

Are you still doing photography? I remember seeing some of your awesome pics
on a website somewhere. Is there a link you can give me? You know, I am a
renowned photographer. I specialize in pics of the back of people's heads,
macro shots of fingers (I didn't say I shot fingers) and camera straps.
Makes me all the more appreciative of real talent.

Jerry



-----Original Message-----
From: john sherman
 
Hi Jerry,

>The clips even if not touching the glass will
>cause some diffraction if they extend over the mirror

My dob has a stop preventing it from going down to horizontal. So I use
gravity to hold the mirror in the cell. 

      ************************

I think that any cell which has any possibility of pinching the mirror
should be avoided. A mirror should be free to do what it wants. At least,
that is so if one wants a high-resolution scope. If you just want a fuzzy
light bucket, then mount it any way you want. If you only have 2 arc-second
seeing, then it doesn't matter (you should move!).

C-ya,

John




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