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Posts Made By: Doug Peterson

April 9, 2009 07:28 PM Forum: Equipment Talk

Recent Interferometic test results

Posted By Doug Peterson
A friend in the optics biz did a round of tests on his interferometer and came up with some interesting numbers.

Two C-9.25s, each measured .25 waves peak to valley, PV, and .040rms, that is about 94 strehl.

Orion EON 72mm ED, .16PV, .038rms. However since he was using a hene laser, he believes he is mostly measuring the spherochromatism; calculated the spherochromatism for a likely similar design in Zemax and subtracted it for an estimated .10 PV, .021rms, about 98 strehl.

Bushnell Excursion 80mm ED spotting scope, .28PV, .055rms, est about 86 strehl.


May 4, 2009 12:59 AM Forum: AstroMart FAQ

Weird unsolicited email response to my for sale ad

Posted By Doug Peterson
Anyone else seeing this:

Hello,
>
> I don't know what you are looking for, but I have a class act machine shop, specializing in proton & electron particle accelerator work. I'm sure we can do a beautiful job for you with a decent description.
>
> Sincerely,


I left off the contact info in case this is just a mistake, but the user registered today, so could be others are getting this pitch en mass.

May 6, 2009 12:04 AM Forum: Equipment Talk

C65 and C70, whaddya get for 100 bucks?

Posted By Doug Peterson
I had one of the early C65 chinese maks. The first unit was so awfully decollimated you could see by eye the parts were glued out of place and pointing in different directions. The second was collimated but had about 1/2 wave of astig.

I just looked at a C70 mak. A little better, about 1/4 wave of spherical abberation from the all spherical design (you didn't think you were gonna get a hand figured Questar did you). Some roof prism error contributes to a mushy focus, the opposite of snap. The obstruction is only about 1/3, so this had potential.

Back to real telescopes....

May 20, 2009 12:46 PM Forum: Global Warming - REAL or NOT

Global avg temps flat for 10 years--all 4 services

Posted By Doug Peterson
http://wattsupwiththat.com/2009/05/19/comparing-the-four-global-temperature-data-sets/#more-7943

May 21, 2009 12:12 PM Forum: Global Warming - REAL or NOT

CNN talks to Dr. Christy, and Dr. Hansen too

Posted By Doug Peterson
http://money.cnn.com/2009/05/14/magazines/fortune/globalwarming.fortune/?postversion=2009051412

May 22, 2009 12:14 PM Forum: Global Warming - REAL or NOT

HARDBALL: global warming debate on MSNBC

Posted By Doug Peterson


http://www.youtube.com/watch?v=JREbT6FCCFA

May 27, 2009 01:10 PM Forum: Refractors

Nikon 50ED spotting scope, excellent

Posted By Doug Peterson
I had good luck with the Nikon 78ED and 60ED, which are of true telescope quality. A lot of spotters are junk, and many are merely okay. I took a chance on the 50ED and it turns out to be quite good, very good star test at 75x, almost no color. It is only one pound, incredibly light and compact, easily fit in a glovebox. I saw a picture of a birder with one sticking out of his jeans' rear pocket!

I lucked out and got an OTA quite inexpensive if you know where to look, already had an unused Nikon zoom eyepiece (the thread is proprietary, smaller than the 1.25" standard). What's more the oculars are clearance priced from some vendors.

A winner.

June 10, 2009 11:48 AM Forum: Equipment Talk

Vixen 95 and 110mm central obstructions?

Posted By Doug Peterson
The scopes certainly look nice, but the central obstruction looks suspiciously large. Anyone measure it at the exit pupil, or find a spec? How are the optics?

June 13, 2009 04:35 AM Forum: Equipment Talk

Celestron Firstscope 3" desktop newtonian

Posted By Doug Peterson
Well you wouldn't expect much for 49 bucks and you don't get much. However the mount is kinda cool, single arm bandit dobsonian style. I expect to improve the scope's shortcomings or replace with a small cassegrain or short tube refractor.

http://www.celestron.com/c3/product.php?CatID=83&ProdID=568

June 26, 2009 07:09 PM Forum: Global Warming - REAL or NOT

EPA's internal nightmare over global warming

Posted By Doug Peterson
http://www.examiner.com/examiner/x-9111-SF-Environmental-Policy-Examiner~y2009m6d25-The-EPAs-internal-nightmare-over-global-warming-Part-1

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