Great Plains Instruments
Equatorially Mounted Instruments for Exploring the Sky
Helping Amateurs Build Better Instruments Since 1988
Everything offered through this website is free!
Please read the special notice at the bottom of this page first!
This site is best viewed with a screen area setting of 800 by 600
This site is dedicated to my three steadfast friends who made it possible
Table of Contents
Click on picture for each article
The Traditional Symmetrical Equatorial Mounting
The traditional symmetrical equatorial mounting, and in particular the fork equatorial mounting offers so many advantages that it is still the mounting of choice by observatories for Cassegrain reflectors between .5 and 1.5 metres' aperture. We can show you how to build one at very little expense for your Newtonian or Cassegrain optics up to twenty inches' aperture.
Stopping Down: Sometimes Less is More
After a long Period when "deep sky" observing of faint, distended objects was pre-eminently popular, the excitement of observing bright solar system objects has been rediscovered. Lunar and planetary observers seek larger apertures, too, as do deep sky observers, but for a different reason: higher resolution. Sometimes reducing the aperture of your telescope can improve its performance. We'll show you why, when, and how to stop down.
For those of you contemplating making your own mirror, we offer a brand new, easier to understand explanation of the most capable testing method for monitoring the developing figure on your mirror, with new kinds of concept illustrations to help you thoroughly and quickly master the wonderful Foucault test.
Borrow Our Tester
If the design and construction of a tester is what is holding you back on starting your first mirror, we invite you to borrow our very capable over and under style Foucault tester. It comes to whoever borrows it with no strings attached whatsoever, except that you must enjoy using it to help get that elusive, just-right curve on your first mirror.
Drives for Tracking in Right Ascension
We can show you two very inexpensive and easy to build Right Ascension driving mechanisms for large instruments. One of these drives won a first prize award at the 1991 Astrofest in Kankakee, Illinois. These two drives are virtually free of periodic error and can be built from ordinary hardware store parts without any machining. We'll first show you a long radius sector drive. The article about our award winning steel tape measure/disc drive is still in preparation and will be coming to our site soon.
Here is my entire collection of bearings, accumulated over the years for planned monster telescopes. Well, I've built my last monster telescope, my "dream telescope" (featured here on this site) and so will not be needing any of these bearings. This is what my knees, feet, and back are telling me: "Last telescope, Dave". So they need to be broadcast at large to all of you, my fellow ATMs, so you can work some artistry with them. If I can get at least a couple of you to build a large, beautiful instrument (or even a small, beautiful instrument) with some of these bearings, I will be happy to feature what you've done on my site.
This little story will be the only thing on my website that is not about telescope making, but it at least brushes up against our hobby of astronomy in a general way. I wrote this story for my much loved older sister to help cheer her in her struggle with cancer. I also surprised and delighted her by giving her my 100-year-old Elgin pocket watch that she had admired once upon the occasion of seeing it. I wanted her to know that I would send time to her in a box if such a thing were possible. She lost her struggle with her cancer on March 31st of this year and was de-resolved back into our mysterious self-aware universe. Please enjoy the story. I did not write the story to advocate any kind of ideological agenda, but rather, just to give to my sister, who was the real writer in our family. For the story, please click here: "Stars, Singing"
I will not be renewing my website after the end of my current subscribed quarter. Therefore, I wanted to recommend to my readers to save any of those pages on my site that you have found useful and would like to refer to in the future. Saving an entire web page to one's own hard drive is easy and useful, as it allows one to read the page off-line, and of course, after a web site has ceased to exist on the world wide web. As of this date of writing (Oct. 8th) my site will have about eight weeks to run.
I recommend saving whole pages if one has space and time to do so; the pages are rich in large photographs, (except for those articles containing only line art as GIF files) so they will take a while to download for those with slower connections. Articles containing only line art as GIF files should not take too long to download for anyone.
If your system or connection speed limits you in downloading whole pages, then remember that you can save selected individual photographs only to your hard drive. Remember to enlarge them to full screen first with a regular left click with the cursor anywhere on the picture. After the picture is fully loaded, a right click on the picture will provide a contextual menu for selecting "save picture as" to call up a dialog box to select where to save the picture to on your own local directory. None of the line art (illustrations as drawings) will enlarge, but a right click will save them also.
Only my web site is going away, not me, and not the information contained in it. The pages will still be available on disk for anyone who might want to request them to copy into their computer's own local directory. Also, I have many illustrated html emails I have prepared with much useful instructional information on mirror making and mounting design and construction that I can send on request. I will be adding one more page soon about recognizing and remedying figure defects, with many "focographs", illustrations of the appearance of the mirror under test with the knife-edge done after the style you've seen in "Understanding Foucault". Watch for this page and save it if you find it useful.
Sharing my long telescope making experiences with all of you, my fellow atms, has been one of the most wonderfully enriching experiences of my life. My deep-felt thanks to all of you for valuing and appreciating my contributions, and for those of you looking forward to my promised continuing help with your projects, please be assured that I will be right here, not very far away from either of my computers.
Clear skies to all-
© 2001 David Anthony Harbour