I am most grateful for the wonderfully complete set of plans that are provided on the original MiataScope site. To help repay this karmic debt, I am placing as much of my plans up here as possible. I cleaned up my drawings and did my best to correct any last minute changes made during construction.
The plans are broken up by the major components of the telescope. I have tried to keep the plans that follow close to a spec for what the final scope looks like. The construction notes includes more detail on why certain ideas worked or didn't. Taken together they form a fairly complete picture of how to build a copy of my scope.
I don't really expect anyone to build a clone though so I have also tried to include some explanations for the factors that influenced my design decisions. They should be a good starting place for anyone trying to build something similar.
Here is a list of errors I can think of in my original plans.
I goofed during the scope's original construction and didn't adjust my modifications of Kriege's mirror cell (pg 136) to make sure that the mirror would remain in the center of the mirror cell. The problem is the top bolt in mirror cell that holds the mirror in place. My mirror cell is 16.5" square. It has three, 3/8" bolts with clips to hold the mirror in place as it is jostled in transport. Each bolt is centered in the bar of the mirror cell and "covered" with a 1" diameter dowel rod drilled off center to protect the mirror from rubbing against the threads of the bolt.
The math is:
| Width of the top half of mirror cell | 8.25" | |
| minus mirror radius | 7.5" | |
| minus 1/2 of ladder rung width | 0.5" | |
| minus 1/2 of bolt diameter | 0.1875" | |
| equals the room left for bolt cover | 0.0625" |
While the hole in the dowel rod is meant to be drilled off center, clearly having a hole in a piece of wood only 1/16" of an inch away from the edge is asking for trouble.
To work around the problem, I have created a wrapper to go around the bolt that is made out of a single layer of the "seat belt" material I used for the mirror sling. It is about 1/8" thick though. Plus, a little slop (perhaps 1/8") is needed so the mirror doesn't press against the bolt when it gets tilted during collimation. So the mirror is about 3/16" below perfect center.
This solution also suffers from problems with holding the clip at the top of the bolt in place. The nut beneath the clip is at risk of coming in contact with the mirror.
The other problem is that occasionally turning the collimation knobs in the mirror cell doesn't result in the mirror moving. This is a result of gradual changes in the sling's wrapping around the bolts it is attached to as the material stretches over time. It is made worse by the lack of a suitable gap between the mirror and the top mirror cell bolt. Periodically I need to adjust the sling because of this. In the field I can also manually pull the mirror down onto the support triangles which will correct this problem even if it does complicate collimation.
As I discuss elsewhere, I switched from using "Plop" to "Cell" for designing the mirror support system. In the end, this meant that I had "Cell" mirror support triangles on mirror cell ladder rungs spaced based on "Plop's" design. Based on field use of the scope I don't think that this has any impact on the scope's performance however.
The digital setting circles are not working as well as I would like. Part of the problem may be that I may need to improve my technique when using them. For example I want to try using a cross hair eyepiece when going through the alignment procedure. Using a bit of masking tape to hold the alt. encoder still has helped to keep it from rotating in the "C" shaped wood block that houses it and improved performance.
I also think I may have left too much wiggle room between the outside edge of the mirror cell and the inside edge of the rocker box. I believe this allows the mirror cell to slide around inside the rocker box when I move the scope.
Here is a list of problems I have had using the scope along with the solutions I've found so far.
Stray light was a problem. Adding a shroud and using a bigger light shield to extend the secondary cage seems to have fixed this.
I originally thought that the secondary mirror was too far down in the secondary cage. After much examination I finally realized that I had failed to make sure my focuser was mounted squarely to the cage. Correcting this problem cleared up the issues with the secondary mirror.
I wanted the Miatascope to have the eyepiece down far enough for adults to be able to look at objects at the zenith without needed a ladder. This was important to me because I tend to do a lot of public events and obviously do not have room in the car for a ladder. The scope is too tall though for anyone under about 5' 10" when the scope is pointed up towards the zenith. Fortunately, this isn't a problem for me at least.
For everyone shorter, I use my ultra heavy duty eyepiece case as a step to stand on. It is made by Underwater Kinetics and it is rated to hold a lot more weight than a single person. I purchased it from Shutan Camera. I am rather fond of Shutan by the way, as I was told that they donated many (if not all) of the telescopes I use when I show the public the night sky while volunteering at Adler Planetarium here in Chicago.
I hadn't anticipated how hard it would be to look at objects low in the sky. With such a low center of gravity, the eyepiece is only a couple feet above the ground when pointing near the horizon. To my amazement, I found that the Star Dust observing chair is able to squeeze in behind the front seats. It has become a required part of my gear when using this scope. Thanks to it I can now spend as much time as I want scanning the galactic center without my back becoming a problem.
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Last updated 1/12/06