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Here's some of the modifications that I've made to my 10" Starfinder that have required little or no money as well as only minimal dexterity and skill. Notes on Collimation
Notes on
Collimation…..
The three main points I want to make about collimating the starfinder are; get the right tools for the job, properly mark the center of the primary mirror, and define the correct position for the focuser during collimation and observing. 1: First as with most things, you get what you pay for. This still holds true for collimation tools. You just can't do better than the tool set from Tectron. For around $100 you'll get three tools and a great little booklet that will tell you everything you've ever wanted to know about the collimation process. 2: Second, In order to know where the center of the primary mirror is during collimation, you'll have to first find and then mark its position. To find the center of the mirror, use the soft clean paper that the mirror was wrapped in for shipping. Gently spread it over the face of the mirror (don't press down onto the surface or you may scratch it). Use a pencil and gently rub the side of the pencil lead against the side edge of the mirror in a manner to produce a traced outline of the entire circumference of the mirror. Once completed, remove the paper from the mirror and fold it in half and then once again into a quarter (with the mirror's circumference outline all neatly matched up to each layer of the folded template). Now take a pair of scissors and snip the tip of the corner off (from what should be the center of the mirror). Unfold you paper and check to make sure that there is indeed a hole in the exact center of the circle. Place the paper gently back over the mirror one more time so that the templates circumference lines up with the outside of the mirror. Use a permanent marker to dot the mirror inside the templates exposed hole. (To make the dot easier to distinguish, place a notebook paper hole reinforcement ring onto the mirror so that it outline the dot. There will be no loss in optical performance by the dot or the reinforcement ring.) You now have a proper reference mark to perform your collimation. 3: Third, with the image shift that is ever present in the factory supplied focusers, it is best to place the focuser to a common reference position when performing the collimation or observing. As best as I can tell, the optimum position for the focuser is with the tube assembly traveling inward toward the secondary mirror. It appears to be relatively centered in the focuser shaft and stabilized. However, I would play around and come up with your own analysis, your focuser could be different than mine. To verify, put in the different collimation tools and observe the changes to the collimation as you move the focuser in and out. Shimming the Focuser…..
The pinion is held in place by a sheet metal cover which doubles as the bearing surface. The absence of a bearing cap or the like causes the pinion shaft to wiggle about in sympathy with the tube assembly. So by reducing the extent to which the pinion moves in its mount will in turn reduce the distance that the tube assembly can move, thus effectively reducing image shift. To accomplish this I used two small pieces of 1/16" thick, lightly lubricated, rawhide leather that were cut to fit on either side of the pinion gear and encase the shaft in a U-shape (approximately 1/4"x1/2"). Pay attention that the leather shims don't bind on the shaft, and that you do not over lubricate the focuser. Any dripping of lubricant will either end up on the eyepiece or on the primary mirror (If this happens clean the mirror with a mild soap as recommended by Meade.) The image shift will still be present, but to a lesser degree than before. The overall action of the rack and pinion assembly should be much smoother and satisfying too. Make sure to read the section on collimation for additional information regarding the proper set up and use of the focuser for maximum image resolution.
Repositioning the Altitude Bearing's Teflon Pads…..
I carefully pried the teflon pads from their former location and repositioned them with my oldest daughter's protractor so that their centers were exactly 70 degrees apart. Wow, what a difference. the telescope moves buttery smooth in the altitude axis now. It had been sticky, which made it hard to track at higher magnifications. The pads came loss from their original positions with minimal prying, but do me careful. A helpful note is that the pads come from the factory held down by what appears to be staples that have had there tops trimmed off. So don't worry about trying to get the nails out first, they're not nails and therefore don't have a head to pry on. I was able to successfully get one out. It was about 3/4" long and obviously not reusable. So I saved myself the hassle and simply drove them further into the mount (out of sight, out of mind). To reattach the pads, I used 1/2" long brass finishing nails. Be sure to use a small punch to drive the head of the nails far enough into the pads so that they do not interfere with the bearing. Cleaning up the Azimuth Motion…..
You should make sure that all the teflon pads are properly staked and that the staples are not protruding out of the teflon so that it could interfere with the motion of the upper half azimuth board. If they are, use a punch to drive the staples further into the pad. Make sure that when you assemble the rocker boards to the upper azimuth bearing board that the screw heads are recessed far enough into their counter sunk holes to not interfere with the teflon pads. Also, use some candle wax (beeswax is best), to fill in on top of the screw head to help eliminate the friction that the holes can cause as they pass across the teflon pad. Use a razor or sharp chisel to carefully flatten the wax out level with the formica. Before assembling the two azimuth boards, use some car wax (Turtle Wax, Rain Dance, or the like), on the underside of the upper boards formica surface. Follow the wax's instructions for its application. When the wax dries, buff it off nice and clean. This will make the formica surface nice and slick. You'll need to repeat the application of the wax a couple of times a year to maintain the smooth buttery feel. Pay close attention to the shimming of the center azimuth bolt area. Meade provides a half dozen or so plastic shims that you can use to build up and provide the proper head spacing that will help insure smooth movement. If you find that your stuck between too few shims to have smooth movement and too many to where the mount wobbles if you add just one more, fashion your own shims from different thickness plastic or leather scraps using the Meade shims as a template. Experiment to find the best combination. Lastly, make sure that you only
apply three of the little rubber feet , and be sure to apply them directly
under the teflon pads. This will provide both the optimum balance for the
varying surfaces that you will set your Starfinder upon, as well as help
ensure that the teflon surfaces are dimensionally stable as possible. (I
also recommend that you go buy bigger solid rubber feet at your local Home
Cheap-O for about $4. The ones that Meade supply are pretty small.)
Adding a Telrad Finder…..
First, simply remove the factory finder and replace it with the Telrad. Place the Telrad in way that it won't obstruct the old finder should you change your mind and want to reinstall it. Be sure to use the hole caps that are sent with the scope to fill in the open holes that are left uncovered by the absence of the finder. Since your replacing the finderscope and not really adding much appreciable weight to the top end of the telescope you probably won't need to add a counter-weight to the mirror end. Second, (and this is the approach that I took), place the Telrad between the factory finder and the focuser. It's a little on the crowded side, but it fits fine. The down side to this is the extra weight that is added to the top end of the telescope which will have to be countered by attaching extra weight to the mirror end. Cheap Adjustable Counter Balance…..
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