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Posts Made By: Dick Jacobson

July 20, 2008 02:05 PM Forum: CCD Imaging and Processing/Deep Sky

NGC 7000

Posted By Dick Jacobson

Very nice! For a really stunning image see

March 22, 2009 11:24 AM Forum: Telescope Making

OK, now what can we make with it?

Posted By Dick Jacobson

This is fascinating! If I understand it right, if you had a nanocup film at the focal plane, you wouldn't need an eyepiece. All of the light would beam directly into your eye. The surface brightness could be much greater than the actual object, so a faint nebula might appear far more intense, something conventional optics cannot do. Kind of like an electronic image intensifier without any electronics.

May 19, 2009 12:22 PM Forum: Solar System Observing

Mars Email - Not Again!

Posted By Dick Jacobson

Yes, I got one from a co-worker. I don't know who sent it to him. Another co-worker asked me if I had heard that Mars was going to be close this August. A member of our local astronomy club even fell for the same rumor. Aaaaaarrrrrrrrrgggggggghhhhhhh!

August 15, 2009 09:54 AM Forum: After Dark

Dark sites to go to without being harassed...

Posted By Dick Jacobson

If you have a local astronomy club you may be able to use one of their star party sites. With 10,000 lakes in Minnesota, I've had pretty good luck using public boat launch sites. Another possibility is a wildlife refuge.

August 25, 2009 12:50 PM Forum: Telescope Making

Telescope Conversion from Tube to Split to Truss

Posted By Dick Jacobson

I'm a little bit ahead of you, having converted my 14" solid tube to a split and then later to a truss. Each design has its advantages. The split tube is easy to build and very fast to assemble. The truss is ultra-compact and light weight. The light weight is an advantage not only for transport, but also has a nicer "feel" when pushing the tube and doesn't cause as much vibration in the mount.

One important advantage of a solid tube is that it tends to keep the secondary mirror free of dew/frost. I never had problems with my secondary dewing over with a solid tube, but have had considerable problems with the open truss (maybe I need to use a shroud).

In summary I would say that if the size and weight are not a problem, then go with a split tube; otherwise consider a truss.

November 10, 2009 11:38 AM Forum: Telescope Making

fork mounted newtonian

Posted By Dick Jacobson

I built a fork mounted 20" Newtonian a few years ago. The fork is more like a cross between a Dob-style cradle and a fork. The tines of the fork are made from pairs of 1x16" oak boards glued together. It works very well. For a picture see,,,,,,,f67,,,,,,,&Words=equatorial&Searchpage=7&Limit=25&Main=1368088&Search=true&where=sub&Name=&daterange=1&newerval=3&newertype=y&olderval=1&oldertype=m&bodyprev=#Post1473171

December 27, 2009 06:26 AM Forum: Equipment Talk

Need Crosshairs

Posted By Dick Jacobson

I have used a tiny #0 machine screw. I sharpened the tip and drove it in from the side at the focal plane. This has the advantage of not needing illumination since it is so thick; the disadvantage is that it obscures about 5% of the view.

January 5, 2010 05:18 AM Forum: Equipment Talk

50" monster Eyepieces

Posted By Dick Jacobson

Darn, I thought you meant a 50" diameter eyepiece! I was picturing a giant spherical eye lens that you could crawl inside and get a 360 degree field of view.

January 25, 2010 12:46 PM Forum: Telescope Making

Converting an old telephoto lens

Posted By Dick Jacobson

If you can find an extension tube that fits your lens, you might be able to modify it to make an eyepiece holder, or something that you could mount a focuser onto.

January 31, 2010 06:30 AM Forum: Telescope Making

Spherical Aberration Plates

Posted By Dick Jacobson

Fascinating! I wonder if I could incorporate these into the "periscope" accessory that I am developing? The available apertures look too small. Hmmm...