#21  
Old 23-11-2014, 09:41 PM
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Peter Ward
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Originally Posted by Gama View Post
...........
So if you want the low down on what to expect from a Planewave telescope in terms of thermal issues then, I really suggest emailing Rick, and asking him.

Theo.
I think I've met him (fleetingly) at a couple of trade shows...in any event, I'm going to the planewave factory in early December. Thanks one and all for the feedback to date.

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  #22  
Old 24-11-2014, 07:14 PM
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You don't want to take a mirror up with you do you ?..
Im in the process of packing it..
Its only 20 odd inches, and weighs 20kG..
??????????????????????

Theo.
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  #23  
Old 26-11-2014, 06:51 PM
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Peter Ward
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You don't want to take a mirror up with you do you ?..
Im in the process of packing it..
Its only 20 odd inches, and weighs 20kG..
??????????????????????

Theo.
Err..... No.
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  #24  
Old 26-11-2014, 06:55 PM
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multiweb (Marc)
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Err..... No.
Doesn't fit behind the seat
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  #25  
Old 26-11-2014, 09:50 PM
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Use it as a good shaving mirror !.
Or better yet, a reversing mirror for the plane.


Theo
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  #26  
Old 27-11-2014, 08:49 AM
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It does surprise me with these premium intruments that optical defects ( ie astigmatism , corrector lens wedge etc ) can slip through . It suggests that they are not given a thorough end to end artificial star test upon final assembly, to make sure it is meeting spec and that the customer is not going to see optical defects on the real sky. I would have thought that that kind of thing was what you were paying extra dollars for.

It is not rocket science to set up a collimating telescope of larger than the aperture to view an artificial star upon final assembly and tweaking. Celestron for example in their heydey used a 22" of long focus telescope to produce a collimated beam and final checking on hundreds of thousands of telescopes.
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  #27  
Old 27-11-2014, 07:49 PM
ericwbenson (Eric)
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Originally Posted by Satchmo View Post
It does surprise me with these premium intruments that optical defects ( ie astigmatism , corrector lens wedge etc ) can slip through . It suggests that they are not given a thorough end to end artificial star test upon final assembly, to make sure it is meeting spec and that the customer is not going to see optical defects on the real sky. I would have thought that that kind of thing was what you were paying extra dollars for.
The off-axis astig doesn't show up on a star test, only on really big CCDs. The wedge issue was only apparent with a one-shot color CCD in very good seeing on a star near zenith. I might have been able to see visually, but probably would have had to know it was there to distinguish it from atmospheric dispersion. In fact in the normal star testing I did the correction\roughness\on axis astig looked really good.

Quote:
Originally Posted by Satchmo View Post
It is not rocket science to set up a collimating telescope of larger than the aperture to view an artificial star upon final assembly and tweaking. Celestron for example in their heydey used a 22" of long focus telescope to produce a collimated beam and final checking on hundreds of thousands of telescopes.
For a big telescope the artificial star need to be <very> far away (impractically) to be of any use, or you swamp the test image with S.A., so the collimating scope is not the problem, it's the <very> long hallway one needs, see here for example: http://www.telescope-optics.net/two-mirror2.htm#Close_objects_error

Regards,
EB
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  #28  
Old 28-11-2014, 08:16 AM
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Satchmo (Mark)
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Originally Posted by ericwbenson View Post
For a big telescope the artificial star need to be <very> far away (impractically) to be of any use, or you swamp the test image with S.A., so the collimating scope is not the problem, it's the <very> long hallway one needs, see here for example: http://www.telescope-optics.net/two-mirror2.htm#Close_objects_error

Regards,
EB
For a final end star test for commissioning a telescope you just need a collimator telescope which produces a parallel light beam into the aperture of the telescope you are testing . Celestron used one of 22" aperture . In the 80's I made and tested hundreds of mirrors at Astro Optical Supplies by 'looking' into the collimated 14" F6 mirror of good quality which had a laser shining on a ball bearing at the focus of the collimator mirror . Also tested many Celestrons that came in, this way .

If you want to test a scopes off axis image quality , you just tilt the telescope to put the artificial star as far off axis as you want to look at ( and of course you could do all that at the focal plane of CCD if you wished ) . If you need to look at the polychormatic performance of the 'scope you just use a white light source .This is an optical testing technique that goes back to the 18th Century. If a manufacturer wants to rigorously test a compound telescope before delivery , this is the way to do it.

Hope this helps.
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