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Posts Made By: David Tarshis

April 3, 2009 01:07 PM Forum: Telescope Making

How much wood? 12.5 f/6.4

Posted By David Tarshis

Trying to figure out approx. how much wood will it take to to do the bottom half of the project i.e. rocker box, ground board, bearings. Will a 5'x5' sheet be enough? I know there are variables, but looking for "more the plenty" or "could be". Thanks

April 6, 2009 10:41 PM Forum: Telescope Making

How critical? Mirror cell question

Posted By David Tarshis

So I'm putting together my mirror cell. It's a 9 point flotation system from the Kriege book. The triangle's aren't exactly centered, not sure what I did wrong, but the distance from A-C and B-C = 6 3/8 while distance from A-B measures 6 1/4 (measuring center to center of bolt hole). 1/8" off. It's a full thickness 12.5 mirror. How critical is it that the pads are equally spaced? Can an 1/8" make that much of a differance? I suppose I can cut and reweld that center post. Thanks
(it's a rubber band)

April 7, 2009 02:56 PM Forum: Equipment Talk

Need help identifying Cestron drive and motors

Posted By David Tarshis

Trying to get a model number, but most important the worth. I'm selling a mount and tripod and want to price accordingly. Thanks

May 1, 2009 10:28 AM Forum: Telescope Making

Flocking inside of upper cage

Posted By David Tarshis

What have you used, what works well? I looked at Protostar's flocking paper, which would be awsome. But being as cheap as I am, what would work from say a fabric store? 5.00 to ship a piece of paper is a bit pricey for me. Thanks

May 4, 2009 09:47 AM Forum: Telescope Making

Wood finish upper cage rings and focuser board

Posted By David Tarshis

What kind finish is best? Regualar wood stain, someone recommened fiberglass resin (just the resin), any idea's? Thanks

May 29, 2009 11:49 AM Forum: Telescope Making

Upper truss clamps

Posted By David Tarshis

I plan to make my own Astrosystems type clamps. I tried calling, got the answering machine... Can someone give me some dimensions to work off of? Radius etc, thanks.

June 15, 2009 10:50 AM Forum: Telescope Making

Finished upper cage, onto mirror box....

Posted By David Tarshis

Using Kriege/Berry book. Is there anything I should consider before construction(i.e. height, inside dimension's)? For example, upper cage id wasn't totally accurate in the book (apparently on the small side) and followed advice from here (thanks to all who contributed). Upper cage weighs in at about 10.4 lbs with heaviest eyepiece and barlow, and pretty much completed. Going to verify focal length (about 80"). 12.5" two inch thick primary. Using 1" OD truss tubes. .049 thickness. As best as I can tell, the distance from the secondary to the top of the focuser racked in is about 9 3/8" The book talks about a spread sheet, I'm attempting to make one. If anyone has insight to go about this, I'd appreciate it. Thanks!

(I'll post pic soon)

October 15, 2009 10:30 AM Forum: Telescope Making

First light!

Posted By David Tarshis

So I was able to align the primary with the upper cage enough to get some measurements for the poles. Kriege's formula was just about right on. Amazing.

The towers are about 2 miles. The a-focal shots were done with a hand held 20D Canon 50mm 1.8


I do have question about where the focuser should be. No mention in the book about where it should be, racked in or out. He mentioned putting in an eyepiece with the most inward travel. I'm guessing racked in. I have a two inch tube on my focuser and put it at half way. I tried all the eyepieces and there wasn't that much movement with the cage. I didn't try any barlows. So back to the drawing board on that one. I even put the 31 in thinking that it would have the most impact. Not so much. Thanks
So here are the pics for the first daytime first light of my 12.5 f/6.4











My kids got a chance to see first light, they didn't get it. They did see how exited I was smile

November 12, 2011 08:49 AM Forum: Digital SLR AstroPhotography

Afocal with my dob?

Posted By David Tarshis

Here's my 12.5 6.4 home made dob. I would like to know how some others have achieved afocal photography with their dobs i.e. brackets etc. Thanks.

June 22, 2017 11:11 AM Forum: Solar System Observing

Solar filter for my 12.5 Dob

Posted By David Tarshis

I live about 50 miles from where the total eclipse will be Aug 21. All I have left of all my telescopes is my 12.5 F6.4 obsession type homebuilt. I called obsession to see what they would recommend for a solar filter and they said dont' even take that telescope outside during daylight. Used to do it all the time with a mask. But I've since sold my 9.25 and my solar filter went with it. I was thinking of just ordering Baader solar film and make another mask. Anyone doing the same thing? Thoughts?