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Lawrence Parchman

Sculptor Galaxy (NGC 253)

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Posts Made By: Doug Scobel

March 5, 2004 03:22 AM Forum: Telescope Making

Ground board. Ebony Star or Teflon?

Posted By Doug Scobel
The problem with that is that dust and dirt will collect on the surface of the ground board, and find its way between the laminate and the Teflon pads. It's better to have the Teflon pads on the ground board and the laminate on top to keep the bearings cleaner and hence smoother.

Doug

March 26, 2004 01:42 PM Forum: Deep Sky Observing

12" vs. 14" Scope

Posted By Doug Scobel
About two inches. grin

Seriously, the 14 has about 36% more light grasp, about 17% more resolving power. Not a big difference, but enough that I would say go to the 14 if you can afford it.

Either one is a significant step up from an 8 inch.

Best regards,
Doug

March 26, 2004 05:03 PM Forum: Solar System Observing

Jupiter - Io - Europa Photo

Posted By Doug Scobel
Very Nice, Bob! That's exactly the view I had visually that night (except that mine was inverted).

Doug

March 26, 2004 05:18 PM Forum: Solar System Observing

Jupiter - Io - Europa Photo

Posted By Doug Scobel
Bob, be ready around 3:00 am (EST) Sunday morning. There will be a triple shadow transit.

Doug

March 30, 2004 01:48 PM Forum: Telescope Making

Improving a dobsonian azimuth movement

Posted By Doug Scobel
It's the "riding on the painted wood" part that's likely the problem. Add some Ebony Star laminate and you'll see a big improvement. Make sure the Teflon pads are clean, too.

You should be able to find small quantities of Ebony Star at your local Lowe's or Home Depot.

Good luck,
Doug

March 30, 2004 09:32 PM Forum: Equipment Talk

ClearSky Problem?

Posted By Doug Scobel
I have no problems with it, other than the fact that all the squares are white! ARGH!

March 31, 2004 08:22 PM Forum: Telescope Making

Another ATM152

Posted By Doug Scobel
Simply beautiful!

Don't worry about the red color. Under red light it will look white.

April 1, 2004 02:06 PM Forum: Telescope Making

parabolical mirror

Posted By Doug Scobel
Assuming you're talking about Newtonians, paraboloids are the only way to go unless you're talking extremely long focal ratios in which case a sphere will work. Plus if you want a sphere then you must go longer with increasing aperture. For example, a 4" f/10 sphere is "diffraction limited" but an 6" f/10 sphere is not. The bottom line is that at most practical apertures and focal ratios the paraboloid is the only game in town.

April 1, 2004 03:00 PM Forum: Equipment Talk

Re-coating Mirror

Posted By Doug Scobel
I believe that the rainbow effect you're seeing at an angle is normal. Someone can correct me if I'm wrong, but I think you're seeing interference from the SiO (or SiO2) overcoat.

The best way to tell if you need recoating is to hold it up to a strong light and see if you can see through the coating. If it looks real translucent then it may need recoating.

April 1, 2004 08:08 PM Forum: Equipment Talk

I'm Quitting Astromony This April!!!

Posted By Doug Scobel
LOL! You don't know how many times I've *seriously* considered the same thing.

What part of MI are you in? It's been downright dismal here in Ann Arbor.

Doug

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