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Lawrence Parchman

Eastern Veil Nebula

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Posts Made By: Tom Rodstrom

September 25, 2002 04:56 PM Forum: Equipment Talk

Too Many Telescopes

Posted By Tom Rodstrom
Tested the 8" f5 with the yellow (minus blue) filter installed. It was very sharp to 300x and beyond. With the filter out, there is just too much color at 33x.

I figured out how to add 25 pounds of weight to the JMI mount and I can use pipe straps to mount this OTA so I will see what wide field yellow views are like. I still think that the lenses can be respaced to bring the correction into the visual range.

The picture shows the test set up. I removed the back plate of the 5" f7.5 and used the focuser on the 8". I used a Chesire eyepiece to check alignment and it was good. On the right you can see the focuser end of the 5" with the 5" diameter coma corrector. The focuser extends 1" into the 1 3/8" sagita of the last lens.

September 26, 2002 01:56 AM Forum: Equipment Talk

Too Many Scopes

Posted By Tom Rodstrom
Great collection, refractors are always nice. What is the first one on the left? Hope I can get to a meeting before I sell the house.

P.S. Good Luck with the coming weather.

October 28, 2002 01:28 AM Forum: Telescope Making

Triplet objective lens

Posted By Tom Rodstrom
As I understand it, with three elements an optical design can have better color and coma correction for a given focal length.

November 27, 2002 04:32 AM Forum: Telescope Making

flocking paper

Posted By Tom Rodstrom
Try:

http://www.mcmaster.com/

Do a search for "velvet". There is a very nice adhesive back fabric. The adhesive is strong, but forgiving when you first apply it. At $4.26 per foot for 45" wide material, price is also great.

December 10, 2002 06:01 PM Forum: Telescope Making

Refractor objective question

Posted By Tom Rodstrom
Larry

Before you put very much work into the project, I suggest that you make a quick test set up to check performance. You might strap the lens to a board and use a small block of wood to support an eyepiece against the board about centered on the lens. With something like this, you will get a fair idea how it is going to work.

I have tried a few of these 5" Beselers and was unhappy with the results. These lenses are designed to focus on a 10"x10" surface 18" from the lens and project the image 10' to 20' away. They are not optimized for infinity focus.

Good Luck
Tom

January 8, 2003 12:49 AM Forum: Telescope Making

Where can I buy clear focuser grease?

Posted By Tom Rodstrom
Radio Shack has a clear Teflon based grease that works well and is very clean for a grease.

February 24, 2003 12:39 AM Forum: Equipment Talk

Attention all CG-5 tinkerers & experts

Posted By Tom Rodstrom
I had a bad experience the second time I used my CG-5. The manual buttons moved the scope ok, but it just wouldn't track a star at all. I double checked the polar alignment fiddled with it a bit and finally gave up.

When I got the scope inside, I found that I had plugged the RA cable into the DEC motor and vice versa. These days, I check pretty carefully.

Good Luck
Tom

March 3, 2003 12:38 AM Forum: Equipment Talk

AstroMart deal gone bad, Part II

Posted By Tom Rodstrom
This is obviously a misunderstanding that has mushroomed out of control. The deal is between a seller with a 125 rating and a buyer with a rating of 9. A seller could not get a rating of 125 if he makes a habit of stiffing buyers and I think a rating or 9 for a buyer is good.

More than likely it is something like an address that was sent or transcribed in error. In a case like that, the item would not show up and neither party would know why. I wonder if they ever checked. In any case, feedback has been left and the mud is being thrown. IMO it appears that the seller can be less than cordial when there is a problem, but who knows who triggered what.

In any case, I don't think that there is any good reason that this problem needs to be posted TWICE in the Equipment Forum.

March 3, 2003 05:22 AM Forum: Equipment Talk

Portable Scope For Backpacking?

Posted By Tom Rodstrom
You might consider an Astro Rubinar. This 4" F10 Russian Mak weighs 4 3/4 lb and is 5 1/4" in diameter by 8" long when stored inside it's dewcap. It can be used as a telescope or a telephoto lens. It is light enough to use with any tripod. With a small modification it makes a nice macro lens.

March 4, 2003 05:06 AM Forum: Telescope Making

1st Telescope-Making Project?

Posted By Tom Rodstrom
One of the best sources of information I have found is "All About Telescopes" from Edmund Scientific. It has a ton of information about telescopes and telescope making. It was first printed in 1975 and is now in it's fourteenth edition. For $12.95 you can't go wrong.

http://www.scientificsonline.com/ec/Products/Display.cfm?CategoryID=192375

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