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Re: [ATM] Double dob-newtonian diagonal?

OR... 
   
  Use a "Flip Mirror" to divert the beam one way or the other with the flip of a lever. No need to modify the scope at all. Takes only a few seconds to make the flip.
   
  OR...
   
  Use a 50/50 beam splitter to feed the eyepiece and camera. Looking at the sun, you won't notice the drop in intensity and you can photo and watch at the same time.
   
  Ken Hunter
  

Hugues.Laroche@ses-astra.com wrote:
  Hello List,

I am coinsidering to attend a total solar eclipse next year, and for this
and the nights before/after I would like mount the optics I have into
a travel dob... nothing new. But, at the crucial moment of totality,
experience tells me there is a rush to fill people's eyes
and also if possible take pictures through the telescope....
I do not see this can be done in 2 minutes
with a single focus telescope.

So, what do you think of using TWO diagonal mirrors and have
two parts of the focal planes reflected at distinct locations, so one
could have an eyepiece and the other a photo device? 

My idea to realise this is to use an undersized (40 mm minor axis) 
diagonal
in front of the normal (58 mm) diagonal, the primary being a
254x1200 mm paraboloid?
Pro: the diagonals can be used as-is.
Con: the spider suport of the first diagonal needs to be extremely thin

An alternative is to have a cored flat diagonal and a normal flat behind.
Pro: no spider vane problem
Con: Cored diagonal is not off-the-shelf

All this needs to be as lightweight as possible, of course!

Thanks for any thought/criticism!

In particular, it might still be better to have a small instrument
piggy-backed on the dob with a camera...

Hugues


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