by Gregg Blandin
Well I finally did it! I purchased the Lumicon Sky Vector system with the 12K and high res encoders. I spent the better of Saturday hooking it up. Nothing is ever quite as simple as it seems. Since a lot of people are planning on getting these devices from what I'm hearing, I thought I'd share what I learned. Some of you probably already know this stuff, but perhaps I can help someone who doesn't. The work was bit time consuming, but the best observing time investment I could ever make!
I suspect that altitude bearing will be easy for most dobs. Mine were a snap, since I have a complete circle to work with. I built a small bracket that went the length of the bearing and used the existing bearing bolts to hold it on. I also put a small shelf on it to set the little computer box. Lumicon provides a "hat" like device that the encoder shaft fits into. It has four mounting screws which went into the bracket. The part which is supposed to go from the encoder to the rocker wasn't long enough, and I'd guess that it wouldn't be for anything with oversized bearings even for a 16" although they say it will work for a 17.5" I made my own (quite easy).
The azimuth encoder was much more of a challenge. Most people try to build their dobs with as little clearance from the mirror box to the rocker to cut down on the scope's height. Adding an encoder that stands up another 2" or so off the rocker base will create a problems for a lot of folks, especially when one of the three collimation knobs is dead center and protrudes almost down to the pivot bolt already. I used a small chain drive at one-to-one ratio and moved the encoder away from the center. It worked well and was accurate. Otherwise, I would have had to raise up the entire rocker box (what a hassle).
I had a couple dumb problems that I solved like my pivot bolt rotating and not tightening the altitude encoder set screw. The biggest problem I had was getting the scope to vertical accurately, this creates major problems if it's not perfect. I would strongly recommend that anyone putting these devices on make an vertical indicator (during the daylight hours!) that can be read at night, other than struggling with the scope in the dark, like I did. For 2 hours I got major errors when I tried to do the star alignment. I almost gave up at more than one point, not knowing what was wrong.
At 2:00 I was about ready to hit the hay, disappointed. Finally I managed to get it right, and was ready to view my first object. Suddenly I caught a second wind and had new energy. I selected M51 and followed the instructions which indicated that I should go something like 130 degrees PAST the altitude stop and rotate the scope 180 degrees. Doesn't this thing know that I can't possibly do what it's asking? I know these devices have a polarity setting so that you can mount the altitude encoders on either side of the scope for example. I had followed the directions, though I didn't agree. To me lowering the altitude should make the encoder go negative, but their dircetions say that the encoder goes + as you move the altitude down. Well, so much for WRONG instructions! And of course, after fixing that, I learned that vertical had to be found again!
So, finally at 2:30, I managed to get everthing working!!!!! It took no time at all to catch to where I would have been, had I spent all that time star-hopping.
I checked out NGC 6894, a small ring nebula look-alike in Cygnus. Normally it takes me about 15 minutes to find it. I followed the instructions and there it was! No up and down the ladder, looking at charts, trying to measure distance between stars and ultimately wasting the night away. Then I viewed several other planetaries nearby and a couple star clusters. At one point I accidentally dialed NGC 6824 intstead of 6826 for the Blinking nebula. Oh my goodness! Luckily the description came up as a round galaxy in Cygnus before I accidentally viewed an "extra" object! But what the heck, I checked it out anyway. I love this. It was so fast, I almost didn't know what to view next!
I'm sorry I don't have much of report here, but I just had so much fun just flying around the sky, brainlessly following the computer's instructions. I'll make up for it next session. I will hopefully have the bugs worked out and have a detailed report.
Warning: It could be fairly long!