Posts Made By: Bob Chester

A nice scope and a great wife, the universe has been good to you.
Bob

I own one and love it. Go to 'search forums' and type in astrosky eliminator for some earlier discussions.
Bob

And another. Same gear. Leaving totality.
4 seconds f3.8 (some zoom) ISO 400
Bob

I get 45mm from dew shield stop to front of objective cell. As Mike states, this may vary, albeit very little, with collimation. Dare I ask----no,I better not.
Bob

Floyd,
I don't think this is the case. I would recommend adjusting the primary untill the shadow is centered in the grid. Assuming of course that you've already adjusted the secondary so that the laser hits the center of the primary.
Although written before the day of laser collimators, 'Newtonian Notes' says "There is no effect on collimation." in regards to secondary offset.
Hope this helps and clear skies to ya.
Bob

Very, Very nice image. Print it out and frame it.
Bob

Darren,
A foucault tester in conjunction with the star test is capable of producing a very good figure. Superb? Depends on your definition of the word. Many variables exist in Foucault such as number of zones tested, ones ability to interpret the shadows, quality of tester etc.. Many large manufacturers use laser interferometry or double pass collimators and other equipment we ATMs can't afford.
I once had a reputable optics shop (E & W in Minneapolis) 'look' at a 6" I ground before they coated it. When I told them I used Foucault and star testing they told me I couldn't get it any better using those methods. I was happy hearing that, but, in reference to your question, TO ME, that means the mirror could have been improved upon if I had other means to test it. In my mind, superb means no visible room for improvement.
If you are going to make several mirrors or have a spare grand or so, Ceravolo (.com) is again offering reference lenses for a Ross null tester and an ATM laser interferomter.
Check out his site. This is the route I would take if I were to start pushing glass again.
Herbert and others on this forum can speek much better about the accuracy of Foucault testing than I can. All I know is 'figure till the numbers are dead on'.
( and that may not be 'superb' enough for some.
Hope this helps, Bob

Great image. Best afocal shot I've seen yet. Keep up the good work and thanks for sharing.
Bob

All, except the one I look at.

Denise,
Stop dancing!! It's a well known phenomenon that the 'New Scope Dance' is misinterpreted by the rain gods as a call for rain. Almost all new scopes arrive with a thick layer of clouds. I certainly hope this is not true in your case.

All kidding aside, congrats. Welcome back to the observing community. I hope your new scope gives you many years of ooohs and aaahs. Let us know your impressions of the scope after a few uses.
Bob