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Posts Made By: Doug Peterson

October 17, 2005 09:25 PM Forum: Refractors

8" F6 ED Travel Star Refractor

Posted By Doug Peterson
The 8" achromat lens at 2000 is a steal if they are good, he used to show RMS numbers that were quality lenses. At one time he quoted the price for the 11", but doesn't look like its happening.

October 31, 2005 05:08 AM Forum: Equipment Talk

Is a SNT an APO??

Posted By Doug Peterson
My Questar has the word apochromat on it's tube. Raytracing of SCTs, Maks, Schmidt-Newts, Schmidt-Casss, Houghtons, etc., typcially have a residual color error similar to a fluorite doublet. Check out Rutten, etc., Telescope Optics, Willman-Bell. It is all rather academic, because the secondary obstruction causes quite a bit of contrast loss, as much or more than the chromatic abberation of an equivalent achromat.

January 25, 2006 01:16 AM Forum: Refractors

Herron Optical telescope/objective help needed

Posted By Doug Peterson
Can't help with the lens, but I know a little history. Herron was bought out and absorbed into Laser Power Corporation 15-20 years ago, probably for tax purposes. Later, Laser Power and Exotic Electro-Optics (where I worked for many years) came together. EEO was purchased by II-VI and Laser Power eventually ceased to exist. I don't know of a single person there left over from the Herron days, so I think it is truly gone.

March 6, 2006 01:25 AM Forum: Refractors

New Takahashi triplet 102 F 8

Posted By Doug Peterson
I see that OPT is taking pre-porders at US$ 2695 for the OTA.

April 1, 2006 04:52 AM Forum: Refractors

orion 100mm ed

Posted By Doug Peterson
If the astigmatism is only seen at low powers, could be your eye's astigmatism. I have that problem. TeleVue's Dioptrix works!

June 24, 2006 02:12 PM Forum: Equipment Talk

Antares Optical rotating tube rings

Posted By Doug Peterson
It was pointed out that ClearVue optics' site now has info on the rings. $299 for 6-12" tubes, up to 20" tubes coming, each custom made. They clamp to the tube with felt-lining rather than permanently mounted and look a little lightweight compared to Parks and Parallax, but a bargain for ATMs. I would hate to build these things myself.

July 12, 2006 07:58 PM Forum: AstroMart FAQ

Beware of deals thru the Message system

Posted By Doug Peterson
Herb took care of the situation. His exact words:

"he can play elsewhere now"

July 18, 2006 03:05 AM Forum: Refractors

7" F7 ED Petzval

Posted By Doug Peterson
I just posted my review:

http://www.astromart.com/articles/article.asp?article_id=459

Oops, my comments regarding the performance of the 8"F12 D&G were with the Chromacor, didn't make that clear.


July 27, 2006 05:13 AM Forum: Equipment Talk

"ScopeTronix is closed until further notice." Just a bad redirect?

Posted By Doug Peterson
I replicated the closed notice this way: I had bookmarked:

http://scopetronix.com/atmmirrors.htm

When I go there there is no navigation menu, so I click the Scopetronix banner at top of page which says:

(Click the banner above if you do not see a navigation menu to the left)

When I do that I get a white page with the only words:

ScopeTronix is closed until further notice.

However, if I go directly to the site it looks like it is still up. What gives?


August 17, 2006 09:15 PM Forum: Equipment Talk

FC-100: what glass is the front element?

Posted By Doug Peterson
I removed the lens elements from the cell, and carefully cleaned them with acetone. First of all, a fluorite doublet is assembled just like any other, glass on metal, with an axial compression ring and a threaded ring. Foil spacers.

For a 23 year old lens, the rear fluorite element has fared very well, no hazing, staining or fracturing. It is of course uncoated.

The front negative meniscus is coated both sides and also is very clean. The interferometer shows that a very flat spot has been polished on the convex exterior side during the apparent rework, then recoated. This defect mirrors the wavefront error, with twice the apparent amplitude as expected.

A friend in the biz is attempting to restore the surface to a nice sphere; he will be polishing the coating off in the process, of course. I have a quote for 75 bucks for a single surface AR coating, if this works out

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