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Posts Made By: David Simons

February 7, 2006 01:43 AM Forum: Telescope Making

A telescope makers Pot Of Gold!!!

Posted By David Simons

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john porretta said:

I recently finished a rather ambitious project of building a 8.5" refractor..

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Hi John,

May I ask who made the lens, and have you had a chance to test it yet ?

I have an old 8" R.E. Brandt lens that needs mounting, and this is quit an inspiration !

Thanks for posting you project !


February 7, 2006 02:19 AM Forum: Deep Sky Observing

Celestial Sampler - a Sampling Book Review

Posted By David Simons

Ron Bee said:

... a review of Sue French's new deep sky observing guide.
http://www.cloudynights.com/item.php?item_id=1364


Hi Ron,

Thanks for the heads up, just ordered it !

I also ordered the new book from David Levy:

Deep Sky Objects: The Best And Brightest from Four Decades of Comet Chasing

Have you had a chance to see that one yet ?

February 12, 2006 01:05 AM Forum: Equipment Talk

C-14 reducer/corrector

Posted By David Simons

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Charles Geiger said:

>>>
... Could a reducer/corrector be designed for the C-14 which would give it wide, flat field photographic potential...
<<<
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Charles,

Lumicon makes a C14 reducer, but I don't know if it flattens the field.

February 22, 2006 07:52 AM Forum: Equipment Talk

Do it Yourself Coatings

Posted By David Simons

Sirius Optics has done transmission coatings in the past for amateurs.

He might do a custom anti-reflection run if there are enough of us that want the coatings done.

http://www.siriusoptics.com/righthome.htm


March 4, 2006 10:36 PM Forum: Refractors

placement of MV-1 filter in front of diagonal

Posted By David Simons

I suppose the farther up the optical path you go, the more area of the filter glass you use. So if there are defects in the glass, you start to bring them into play more. If the filter glass substrate was of high quality, flatness, homogeneity etc., then I would think it would not be a problem.

How did you get your lens ? I thought the RR lenses were NLA ?

March 5, 2006 11:56 PM Forum: Eyepieces

Lowest Power and FOV in a C-14

Posted By David Simons

Chuck,

Lumicon makes a focal reducer "Giant Easy Guider" that gives about f5 to f6.5 with an 80mm lens, so it should allow you to fully illuminate a 2" ep.

At f5, a 31 Nagler gives 57.4X @ 1.43 degree.

However there could be obstruction issues showing up at these low powers, central blackout effects, distortion because the reducer lense is not fully corrected etc.

I have used one of these with mixed results visually. I may try it with the 31mm Nagler if we ever get another clear sky here in North CA ?!

As the exit aperture of the C14 is about 3", I suppose a special EP could be built with that size field lense, but I have not yet seen anything like this. There may be some military ep's like this though.

March 9, 2006 07:00 PM Forum: Beginning Astronomy?

How do you do it?

Posted By David Simons

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Aaron Tornow said:

While I am not exactly a beginner, there is something I (and others I am sure) would like to know:

What is it that all of you do that you are able to afford the amount of equipment you have?

....

How do/did you guys do it? How can you afford to make that kind of investment?
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Hi Aaron,

Very good question.

1.) No RV

2.) No Boat of any kind

3.) Almost no other expensive hobbies, ie. wood shop, Golf etc.

4.) Less house than I might have been able to afford

5.) No Cabin on the lake (miss this one)

6.) Minimal skiing in the winter. (hmm, might change this one)

7.) Herb has setup a virtual "loan" system. If you buy good used equipment, you can get back most of the original investment when you sell it, so unless it's the bottom end Chinese stuff, or it gets broken, there is only a hole in your pocket while you physically own the eqp. You can generally come out fairly even.

8.) Kids are still in grade school smile



March 12, 2006 04:46 PM Forum: Equipment Talk

Cheapest way to get GOTO...

Posted By David Simons

Hi Ben,

This may sound drastic, but unless you can easily adapt something like an old Meade DS-Autostar motor set to your scope, I would suggest selling what you have, and getting a used GOTO scope.

If you consider yourself very adapt at mechanical modifications, then there are some Yahoo groups that do this sort of thing.

Let us know your inclinations smile

March 30, 2006 10:08 PM Forum: Telescope Making

10% obstruction (1% area)

Posted By David Simons

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Stu Lieberman said:

I have been playing around with Newt and I have calculated a 4.5" mirror with a 0.5" diagonal that is doable with no loss or vignetting. A sled focuser with the eypiece barrel bottom just inside would push the focal plane way up the tube.

How would the contrast be for a 10% obstruction?

Are there any reflectors with very small diagonals out there?

Stu
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Hi Stu,

I made a 10" scope with a 12% obstruction, and no spider at all, but technically my secondary is 100% wink

I have some pictures on my web site:

www.planetatm.com

Stars focus down to very small points, and no spider diffraction on bright objects either smile

if 10% gives you a 1/8-1/4" illuminated field, then you should have a fine view.



April 6, 2006 11:28 PM Forum: Refractors