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Re: XLT

Jim S — Fri, 24 May 2013 04:05:11 GMT

Moderators, you may delete the earlier message that starts out this way. I neglected to remove the wrong subject line and replace it with a correct one for

Blown Diode in Advanced GT goto tripod.

Jim S — Fri, 24 May 2013 04:02:54 GMT

I need some technical help. I have a Celestron Advanced GT GoTo tripod with the Nexstar Hand controller. While I was using it, my "wall wart's" voltage

Re: XLT

Jim S — Fri, 24 May 2013 03:57:47 GMT

I need some technical help. I have a Celestron Acvanced GT GoTo tripod with the Nexstar Hand controller. While I was using it, my "wall wart's" voltage

Saturn 05/23 NNTZ Dark Spot

Christopher Go — Thu, 23 May 2013 23:19:19 GMT

I spent some time re-collimating my OTA. Seeing was also okay this evening. This is an image with the ASI120MM camera. Note the dark spot on the NNTZ. Note

Re: Can a scratch cause a diffraction spike?

Dale M — Thu, 23 May 2013 18:39:19 GMT

I think I shall do that Thad! thanks..lol Hoping for Clear Skies! From: thad_floryan To: sct-user@yahoogroups.com Sent: Thursday,

Re: Can a scratch cause a diffraction spike?

Chris Peterson — Thu, 23 May 2013 14:03:57 GMT

That's not true. Any linear structure wider than the wavelength of light in the aperture will produce a linear diffraction spike, with the energy in that spike

Re: Can a scratch cause a diffraction spike?

Rod Mollise — Thu, 23 May 2013 12:53:08 GMT

It would take a very deep scratch to cause a spike. Might want to keep looking. Rod Mollise Contributing Editor Sky and Telescope Magazine Uncle Rod's

Re: Can a scratch cause a diffraction spike?

Chris Peterson — Thu, 23 May 2013 04:18:22 GMT

Spots and other round defects in the optical path produce much less pronounced diffraction effects than linear structures like scratches and sleeks. Chris

Re: Can a scratch cause a diffraction spike?

thad_floryan — Thu, 23 May 2013 04:01:57 GMT

... The primary mirror of the 107" telescope of McDonald Observatory in Texas has a handgun bullet hole in the primary:

Re: Can a scratch cause a diffraction spike?

thad_floryan — Thu, 23 May 2013 03:56:21 GMT

... I wouldn't worry much about it. There are folks who deliberately fasten criss-cross fishing line at the front opening of their Astro-Physics refractors to

Re: Can a scratch cause a diffraction spike?

Dale M — Thu, 23 May 2013 03:53:56 GMT

Don, you can cover a scratch on the Primary in black marker? Because I was under the impression that I needed to keep my primary looking good! But if I

Re: Can a scratch cause a diffraction spike?

Chris Peterson — Thu, 23 May 2013 03:48:44 GMT

It will still make a spike. What you may be able to do is soften the edge of the scratch using a black marking pen, which apodizes the defect. That can diffuse

Re: Can a scratch cause a diffraction spike?

jphosey0724 — Thu, 23 May 2013 03:36:24 GMT

Won't it still make a diffraction spike if I do that?

Re: Can a scratch cause a diffraction spike?

jphosey0724 — Thu, 23 May 2013 03:36:20 GMT

Chuck, It is on the primary. I bought the scope used, the previous owner did that.

Re: Can a scratch cause a diffraction spike?

Dale M — Thu, 23 May 2013 03:10:03 GMT

you can really put black marker over the scratch, on your corrector? wouldn't that harm the view in any way ? or not. Hoping for Clear Skies! From: Don