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Zavatar
2003-Dec-08, 08:57 PM
I just received my very first telescope. Unfortunately, the circumstances in which I got it are less than happy. My sister's godmother passed away recently from cancer... She was more a member of the family than anything else. A few months before she died, she bought this telescope. I didn't know about it, but my mother tells me she bought it because I was always talking about astronomy. She left it for me...

I decided to try it out yesterday. I'm living inside Lisbon right now, a big city with lots of lights, so the only thing I could hope too see in any detail was the Moon. I did manage to see it, and it was a wonderful sight, but I think there's something wrong with the controls on the scope. I can manage moving in R.A. without much trouble but when it comes to Declination, the controls just won't seem to respond. I have to turn the knob a few times before the scope starts to move, and even then, the movement is erratic.

Does anyone have any ideas on what might be the problem?
By the way, the scope is a 114mm reflector from Tasco

Glom
2003-Dec-08, 09:02 PM
The slow motion controls on the declination have a range of turn. If you reach the limit, you'll have to recentre and use the main declination axis to realign.

Zavatar
2003-Dec-08, 10:21 PM
I've been checking up on the scope. It seems the slow motion controls work fine when I'm increasing declination, but don't work so good when I'm decreasing declination...

SarahMc
2003-Dec-08, 11:15 PM
I've been checking up on the scope. It seems the slow motion controls work fine when I'm increasing declination, but don't work so good when I'm decreasing declination...

There may be some backlash in the gears, or you may have the scope balanced improperly. Both will cause that problem (with either axis). Try to adjust the counter weights. Depending on the mount and tube, you may be able to adjust the tube back and forth on the mount as well. You could have too much weight forward or backwards of center.

If adjusting the weights and tube position doesn't help, you may need to take a closer look at the declination gears. Typically they're a worm and spur gear arrangment. Either the teeth of the spur aren't meshing with the worm properly (or fully), or the worm is loose on it's shaft. Both conditions will cause a backlash problem. There's usually an adjustment of some kind that maintains the pressure between the two, or locks the worm to it's shaft (like a set screw).

Because you say it works fine when increasing the declination, I'm going to assume that the scope is front heavy and is loading the gears. When you decrease the declination (drop the altitude), the gears unload and you get some backlash.

Hope that helps some. If you can't find the problem, maybe a trip to a local astronomy store, or a helpful amateur nearby can take a look at the mount for you. Glom is correct with smaller mounts too - make sure you're not forcing the declination axis beyond it's range. Loosen the lock and recenter, then the controls will work again.

Zavatar
2003-Dec-09, 12:35 AM
I found out what the problem was: the controls worked fine until a certain point and then they started to act weird. I found out why. The counterweight was pressing against one of the tripod legs, so of course I couldn't move the scope anymore! If I lay the scope on it's side, I don't have this problem, but I'm afraid it might drop because of it's weight or because of the counterweight's weight...