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Posts Made By: George Kiger

January 23, 2007 03:52 PM Forum: Reflectors

Mirror chip on the front....

Posted By George Kiger

robert cosgrove said:
... ugly chip on the front...the mirror still throws up fantastic is this possible ...

Painted black, the chip will not harm the image with scattered light, and the only bad thing you end up with is a typically very tiny increase in diffraction. If the mirror is otherwise excellent you will likely not notice any harm to the image. If you already have a scope, put a little piece of black construction paper on the mirror and take a look.

April 2, 2007 07:10 PM Forum: Refractors

Short Tube APO vs Achro

Posted By George Kiger

Not exactly what you are asking but this has a lot of interesting info:

April 11, 2007 07:18 PM Forum: Reflectors

Should there be a profit?

Posted By George Kiger

Floyd Blue said:
... would $4,000 be too much? That would be $25 an hour minus the cost of running the business, including utilities and rent as well as advertising and phone bills ...

Obsession's 12.5 with Feathertouch is $3,370, and Starmaster's 11 with Feathertouch is about $3,400. And I don't think anyone would work that hard and take those business risks for $25/hr.

So, your cost estimate is probably too high.

And, $4,000 is probably too much to charge.

I think there are at least three segments to the 'real telescope' buying public. On one end, price is by far the dominant factor. The middle might be characterized by 'most value for the money'. The high end is highest quality and usually highest prices.
I would guess that the smallest group is the high end buyer, so it is a segment that is not easily penetrated. Established, proven brands attract the high end buyer. If someone wanted to compete in this area they would have to get a big name mirror, Feathertouch focuser, etc. - and charge less than the established brands. Not easy.

July 6, 2007 04:24 PM Forum: Eyepieces

Planetary Eyepieces

Posted By George Kiger

Steve Sands said:
William Optics came out with the SPL line (3,6 & 9mm) for $319 for the set(wow!).

I agree that WO generally puts out fine equipments, but their spl config says 7 elements in 4 groups, which is very odd for eyepieces being advertised as optimized for viewing the planets where simpler is usually better. If price is a major factor, then I would go with a good Ortho.

August 24, 2007 05:04 PM Forum: Equipment Talk

maximum fov of MN56?

Posted By George Kiger

Greg Nowell said:
The secondary at 30mm would not, in a regular Newt design, be large enough to illuminate fully a two inch eyepiece.

My calc shows a fully illuminated field of just over 12mm.

September 4, 2007 05:24 PM Forum: Home Observatories

Scope got a brand new bag

Posted By George Kiger

Any problems with condensation?

September 13, 2007 09:59 PM Forum: Eyepieces

$ 30,000 eyepiece

Posted By George Kiger

Markus Ludes said:

160 mm focallenght
200 mm field stop
lens design: 2 elements , made by Zeiss West Germany
Type Huygens

New cost $ 30,000

see attached image


$30k For a HUYGENS eyepiece! That is the craziest thing I have ever seen.

Markus, what possible use would such an eyepiece have?

September 21, 2007 08:18 PM Forum: Equipment Talk

APO vs. Achromat Focal Length

Posted By George Kiger

Lee Spain said:

I've heard that a long focal length helps an achromat reduce false color issues. For lunar and planetary viewing, is there a point at which a long focal length would allow the performance of a regular achromat telescope to meet or exceed the performance of a shorter focal length APO or semi-APO?

For the sake of argument, I'm thinking about an Jaegers 80mm Achromat with say a 1200mm focal length versus one of the shorter refractors like a WO ZenithStar 80 or a Stellarvue SV80.

The old rule of thumb was that color in an achromat would not be objectionalble if the focal ration was at least the square of the aperture in inches. For an 80mm scope this would be f/10 or slower, so your 80mm f/15 should have good color correction.

October 4, 2007 02:25 PM Forum: Eyepieces

Has anybody built an eyepiece?

Posted By George Kiger

A simpler eyepiece that performs similar to a plossl in longer focal lengths is the symmetrical. Take two cemented achromats, say 30mm diameter and 100mm fl. Place them crown-to-crown to make a 50mm fl eyepiece. I built one more than 30 years ago and had a lot of fun with it.

October 17, 2007 02:45 PM Forum: Eyepieces

What good is a really long FL eyepiece?

Posted By George Kiger

That mag would give you a 13+mm exit pupil - far to large for anyone's eyes (7mm is exceptional) to take in.