Quote:
Originally Posted by strongmanmike
Great project Dave, really hope it comes together as you imagine, the specs are close to perfect 
What camera are you planning to use on it? The focuser and focuser attachment are critical issues with a large heavy camera.
What is the ID of the tube?
A 100mm secondary sounds a little small..? What chip size are you illuminating?
I have purchased a (modified) Orion Optics AG12 with FLI Atlas digital focuser, so we will be imaging with very similar scopes 
Mike |
Thanks Mike. I will be using an STL-11000M (the same one I am currently using with my 200mm Newtonian) with an Optec TCF-S3. Far larger and more solid than my current 2" Moonlite - it is a crayford design and I believe is tensioned to 500lb pressure. The focuser will be attached to an adapter plate via a circular dovetail and 6 set screws, and the adpater plate will be shimmed and bolted to the flat focuser platform (seen in earler post image of the tube) at three points on a diameter of about 150mm, so should be rock solid.
The ID of the tube is approx 370mm.
The primary is f/5, and using Mel Bartel's diagonal calculator with my optical configuration gives a 100% illuminated field on a 30mm diameter field, dropping slightly to 94% in the extreme corners of the STL chip. From memory I believe the 3" Keller corrector that I have has similar vignetting so the diagonal size is really quite optimal.
Have you taken delivery of your (modified) Orion Optics AG12 yet? I assume that part of the modification is to incorporate a raised platform for the FLI focuser (due to the backfocus required by the Wynne design corrector)?
Quote:
Originally Posted by multiweb
Amazing stuff. Watching with interest.
|
Me too!! Tell me how it turns out when I'm done - I'm too nervous to look!
Sorry - I guess that's why they call us ATM nuts !!
Quote:
Originally Posted by gbeal
Looks nice Dave, I did one similar a while back, when I was in "C/F Mode". Mine took the shape of two separate triangles of foam core board, over which I layers C/F matting. Bolts stick out, and recessed metal screw in sections allowed the necessary fittings to attach.
Worked, and worked well, plus it was as light as. In the end I opted for a couple of very thin stainless triangles instead, reducing the back focus a heap, and the C/F jobbie has sat unloved ever since.
Gary
|
OK, sounds like you used sandwich core lay-ups. That's how the tube I will use is made (it has a 15mm honecomb cell core - made by Dream Telescopes in the USA). I did actually make my current 200mm scope tube in similar fashion. Trouble is, to get really good results you need to vacuum bag (to achieve a 30-40% resin to cloth ratio) and ideally use an elevated heat cure epoxy. Also, although sandwich panels are structurally quite rigid they tend to lack the mechanical strength needed when high point stresses are applied eg. the push/pull screws that I will be using in the cell. That's why I went for "lami-casting" - it's very strong but still around 40% of the weight of same dimensioned aluminium. I'm not really sure how stiff it is in comparison, but I'm assuming that with such a high number of layers of CF cloth it should be pretty good.