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Posts Made By: William Chang

January 30, 2005 07:02 AM Forum: Telescope Making

Mirror cell: Adding more points?

Posted By William Chang
Michael,

Thanks, yes the existing cell uses bolts and the holes are too big. Not having a machine shop (nor a lot of time) my options are limited. I do have a Dremel smile and basic hand tools.

I had thought it was 16" when I bought the mirror here, but it turned out to be closer to 16.5". Nobody sells a 16.5" cell. (And the mass produced ones might not be any better.)

Would you happen to have parts you can spare (or part-numbers), that aren't too difficult to make use of?

-- William

February 1, 2005 04:56 AM Forum: Equipment Talk

Are You a Maximizer?

Posted By William Chang
I carry an old fortune cookie in my wallet:

Simplicity of character is the natural result of profound thought.

Optimized (as opposed to Maximized) instruments are simple to use and effective. They are usually more expensive than merely Maximized instruments that try to do everything, often poorly.

I would like to believe we are Optimizers, not Maximizers.

-- William wink

p.s. No, not the cookie itself! That I ate.

February 8, 2005 06:40 AM Forum: Telescope Making

Binocular Mirror Mount

Posted By William Chang
I have always had a question about these, perhaps only of "intellectual interest".

Say I want to mount a red-dot or green-laser or straight-through finder. Because the reflected axis (where in the sky the bino is pointing) moves twice as much as the mirror's tilt, what mechanical contraption would be needed to keep the finder aligned with the reflected axis?

8O

-- William (Saratoga, CA)

February 11, 2005 06:21 PM Forum: Equipment Talk

Change Secondary Size on a Meade SN?

Posted By William Chang
Bill, I had thought about doing this, and there was a thread (not sure where) where it was reported the SN Schmidt corrector is a real Schmidt corrector. This is good news, in that you can move the corrector further out while you try to reduce the secondary, and actually improve the scope. That thread pointed to a web page where someone had turned the SN10 into a spectacular, bona fide Schmidt camera, albeit twice as long and with spider vanes.

I have coming to me the optics from a damaged SN8, which I can compare against my SN6. In the mean time I'd love to hear more about your project/progress.

That all said, it is a bit crazy to attempt on an undamaged SN8. The hole in the corrector probably isn't much smaller than the secondary (though every percent counts in the upper 30s), and the glass near the hole might be suspect.

-- William (Saratoga, CA)



February 11, 2005 06:55 PM Forum: Refractors

Pentax PF-65ED for astronomical viewing?

Posted By William Chang

Zack,

I have a PF80 straight-through that's only about 3 lb. I mount it side-saddle style via a small ballhead on a carbon tripod. 8 lb total including the XL zoom EP. I did try using it for astro -- it turns out one could focus at infinity with a "barlowed diagonal", after a fashion. With some more work I think it could be made practical, right now it isn't quite useable. A 45-degree PF80 might work OK without mods. Yet another approach for astro is to fashion a periscope-like attachment to the front, holding a 3.1" elliptical diagonal, if you know what I mean.

-- William (Saratoga, CA)

p.s. I might list the PF80 because a 4lb 4" Borg is due to arrive next week


February 24, 2005 06:53 PM Forum: Equipment Talk

Johnsonian Type 5 Platform

Posted By William Chang
Joe, it has been recommended by the Yahoo group that a flat plywood board be bolted to the top, for the scope to sit on. I have been meaning to do mine, but work has kept me from it (I really should sell it).

The design itself is super-clever, great for someone who travels to different latitudes.

-- William

March 6, 2005 07:34 AM Forum: After Dark

G-11 and Cassegrain Collimation

Posted By William Chang
Polar-align your R.A. axis on your artificial star?? -- William

March 9, 2005 05:36 AM Forum: Binoviewers

Denkmeier customer service

Posted By William Chang
Thanks for the report. I'm planning to send mine in for the same upgrade. Question: how did you ship the BV, by itself or in the original "briefcase"?

I'm also tempted by the SCT PowerSwitch but wish the Barlow were less than 2X (high for my 6" f/15 Mak).

-- William

March 11, 2005 06:48 PM Forum: Eyepieces

Re: advice needed on 40mm UO mk-70 and/or Axiom

Posted By William Chang
Good to hear there was no secondary shadow. Doesn't the f/ratio become effectively f/6.7, assuming 6mm exit pupil? The effective aperture becomes 10in, and CO goes up by half.

I have a 16.5" project with 3.1" secondary -- wonder if the MK-70 will show the secondary shadow :S

-- William

March 17, 2005 02:20 AM Forum: Equipment Talk

Best Binoculars while Soaking in Spa

Posted By William Chang
Wow 8O Three suggestions, all of them serious wink

First add a really long dew shield -- that has to help.
Attach a (holed) snorkel mask to the eyepieces to make a uber eyeguard.
You sure you can't bolt a parallelogram bino mount directly to your spa? Too many advantages to list.

-- William

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