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Posts Made By: Alan French

March 3, 2006 03:33 PM Forum: Equipment Talk

Ultrasonic Cleaning

Posted By Alan French
While paging through the airline's "Sky Mall" magazine on the return from Winter Star Party, I noticed an ad for an ultrasonic cleaner. This is geared for jewelry and eyeglasses, but I wondered if it might be suitable for secondary mirrors. Has anyone tried this?

Thanks.

Clear skies, Alan

March 7, 2006 11:15 PM Forum: Deep Sky Observing

Original Burnham's Celestial Handbook Question

Posted By Alan French
Did Robert Burnham, Jr., self publish the entire handbook in loose leaf format, and was only part of it published this way?

Thanks.

Clear skies, Alan

March 14, 2006 03:36 AM Forum: Telescope Making

Good Secondary Holder Design

Posted By Alan French
Has anyone seen a design for a good secondary holder? By good, I mean one where the tip and rotation of the secondary mirror are completely independent.

I've got some ideas, but wondered what other folks might have come up with.

Thanks.

Clear skies, Alan

March 17, 2006 08:05 PM Forum: Astro Binoculars

10x42 L Impressions

Posted By Alan French
I have been using the 12x36 IS IIs for birding and a little astronomy for 15 months now. I like them very much, but once in a while I have wished they had a shorter close focus. This is one reason I was interested in the new 10x42 Ls. I had a chance to try a pair a few weeks ago.

Some people object to the need to hold down a button to engage the IS feature, but I find it is quite conveniently part of holding the 12x36s. The 10x42s simply require depressing the button once to engage the IS feature. I found the button very poorly placed for my hands.

I was most interested in the close focus on the 10x42s. They do focus quite close, but it takes forever to get there. Far too much turning of the focus knob for my taste.

Finally, the 10x42s are just too much of a handful for me. It's not just that they are heavy, but that they are awkward - at least for me - to hold. Anyway, I crossed them off my list.

Clear skies, Alan

March 30, 2006 10:48 PM Forum: Equipment Talk

Thread Specs - Dakin Barlow

Posted By Alan French
Does anyone know the thread specifications on the bottom of the Dakin barlow from Vernonscope? I know it differs from almost everyone else.

Thanks.

Clear skies, Alan

April 15, 2006 12:35 AM Forum: Refractors

Antique Glass

Posted By Alan French
My modest glass collection includes a pair of blanks for an achromat. They are both plano-plano, 1" thick, and 6.25" in diameter. One is marked "Crown 8959 BSC2" and the other "Flint 4258 DF2."

Can anyone tell me anything about these glasses? Are they worth the time and energy required to make an achromat from them, or would it be better to start afresh with modern blanks with known indices?

Somewhere I have indices someone gave me for BSC2 and DF2, so I suspect I could come up with a reasonable design. At worse, I might have to adjust one surface to bring the color in?

There are several projects - largely household stuff - ahead of anything like this, but I am trying to get rid of stuff with no future. I need some room in the workshop!

Clear skies, Alan

April 23, 2006 06:37 PM Forum: TeleVue

Be Careful Where You Leave Your Eyepieces

Posted By Alan French
This eyepiece was in a briefcase in an observatory. The briefcase became home to a large colony of ants.

Under the dirt is a 4.8mm Nagler. The optics were also damaged, and I think it is a total loss. (No, it is not mine!)

Yes, the photo is not quite in focus.

Clear skies, Alan

May 5, 2006 12:58 PM Forum: Refractors

Re: Stripping Coatings

Posted By Alan French
David Hawkins said:

Does anybody know of a company or person that can strip and re-apply anti-reflective coatings to a telescope lens?

I wouldn't fret too much about re-doing coatings. As others have said, it is not a simple nor cheap process. Uncoated achromats actually work well as long as it is not a design prone to ghost images.

Clear skies, Alan

May 9, 2006 08:09 PM Forum: Astro Binoculars

"Prototype" 15x70s

Posted By Alan French
Marj and Roland Christen of AP brought two binoculars to NEAF. One was a 10.5x70 and the other was a 15x70, both made by a small company in China that makes military optics.

They are waterproof, have individual focus, quality prisms (nice round exit pupils), and excellent coatings. I played quite a bit with the 15x70s and they seemed very nice. (With their large exit pupil, the 10.5x70s held no interest for me.) If AP makes them available, I'll buy a pair.

Clear skies, Alan

May 9, 2006 08:41 PM Forum: Equipment Talk

Refinishing Tripod Legs

Posted By Alan French
I was given an older Super Polaris mount. The wooden legs have suffered a bit and need refinishing. Would some of you wood knowlegeable folks give me some advice on how to get them looking nice, preferably with a finish that will hold up well.

Thanks.

Clear skies, Alan

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