Sean Walker said:
...what in bejeezus am I doing wrong in trying to align my Celestron ASGT mount and be able to GOTO...
Sean,
Since a lot of other people have offered some suggestions, I figure I'll throw in my two cents worth. I don’t pretend to be an ASGT expert but I’ve been working with the one I bought my daughter in 2003 for the past 5-1/2 years and have trained a few others in using later versions and have run into and fixed a few glitches along the way. For the most part, the Celestron ASGT is pretty good for the money, but it has its issues. Here are some things to check.
1. The ASGT can (barely) handle a C11 or a 10” Newt, so it shouldn’t have any problem with your 6” Newt.
2. The built-in bubble level on the ASGT is not too accurate and I found one on a friend’s mount that was loose and eventually fell out. Try using a real (known good) bubble level on top of the tripod yoke platform before mounting the head, then check the reading on the head’s bubble level.
3. The manual alignment stickers on the RA and Dec axes seem to be put on by a blind person in the factory (maybe the same guy who installs the bubble levels) and are not very accurate. I suggest manually aligning the mount by eyeball, confirming that the counterweight shaft is perfectly vertical when viewed from the front and that the OTA is pointed exactly toward Polaris, regardless of what the stickers indicate. (A Telrad helps with this.)
4. Check the RA and Dec worm gears for looseness or being too tight. There should be virtually no slop in either axis and the motors should not sound like they’re straining. If you’re somewhat mechanically inclined, it’s not too difficult to adjust the gears. Make sure they have grease all the way around.
5. Although I have a Celestron polar alignment scope, I’ve found it unnecessary to get good GoTo accuracy. I just carefully eyeball Polaris so it’s visible in the center of the holes through the RA axis and that’s good enough. This takes a little practice.
6. Make sure the Latitude adjustment hardware is firmly snugged down but don’t over do it. The same goes for the RA and Dec clutch levers. The ASGT head is made of rather fragile aluminum/pot metal and doesn’t like over-torqued screws.
7. Assuming you know how to input all the required information into the hand controller, just stick with a two star or three star alignment, making sure that the alignment stars are as far apart as possible. (Sirius and Betelguese are way too close together for an accurate alignment.)
8. Does your hand controller allow you to continue through all the menus in the proper sequence as described in the printed instruction manual? I ran into one that wouldn’t and it turned out to be defective and had to be replaced.
9. Check the condition of the RJ11 connectors between the RA & Dec motors and the hand controller connector. Make sure they’re secure, clean and without damaged pins. I’ve run into bad cables that looked good and they can make you crazy. I found an intermittent cable only by testing it with a DVM. I now have my own kit for making new cables.
10. While on the subject of cables, take a close look at your Dec. motor connector cable and both RJ11 connectors. (See attached photo.) Note that there is an orientation rib on one side of the cable and the other side is smooth. When you hold both RJ11 connectors side by side with the gold contacts up, one end of the cable must have the ribbed side up as it enters the connector and the other end must have the smooth side up. If your cable has ever been replaced or repaired, and it was done wrong, the Dec. motor won’t work right because the wire sequence is reversed.
11. Are you supplying power to the mount with an A/C adapter or a 12 volt DC battery? I would recommend using a 12 volt battery (12 volt battery pack with a lead-acid battery), making sure the connector cable is fused and is in good condition. Keep the power connector cord short and check the actual voltage delivered at the connector which plugs into the mount with a DVM. Confirm that polarity is correct – center contact is Positive.
I've concentrated on a lot of mechanical and electrical issues that can affect the ASGT mount, most of which I've had problems with. It sound's like your hand controller is probably working OK, so there might be a problem elsewhere.
This is all I can think of at the moment. Good luck in getting your ASGT to work properly.
Attached Image:
Sean.
