Issues with an LX90

[1ponders] (Paul) · #1 21-09-2005, 11:16 PM

Last night I helped out a couple of new LX90 owners. Showing them how to setup, how to set their time, location, date, train the drives, align the scope yadda yadda. You know the drill

While centering objects I came up against something I've not seen before in the LX90 or 200. Once the scope slewed to the new location and I used the handpiece to center the object, the scope would move back toward where the object was originally by about half an eyepiece (26mm). For example: If I slewed to vega and used the finder to roughly center it in the finder, when I went to the eyepiece, say vega was at the left hand edge of the field of view, I would have to adjust the scope so that vega was at the right hand edge and then the scope would move on its own and vega would finish in the center of the field of view??? After the first time this happened I retrained the drives, (I had a similar prob with a friends LX75 but once the drives were trained the prob disappeared) thinking this might be the prob. Didn't make any difference. The really wierd thing was that the other LX90 right beside it didn't do this?????

Phil or anyone, any ideas?

ps I can't be certain but I think this was only in RA/Az movement

[1ponders] (Paul) · #2 21-09-2005, 11:20 PM

Oh and another thing. Do the LX90 always take forever to finish their slews. These two would slew normally then when they got near the object they would slow down to normal centering rate but take AGES to finally reach their target. Or have I just been spoilt by the LX200 which had a much faster final centering rate. 15 sec as opposed to a minute

RB (Andrew) · #3 22-09-2005, 12:24 AM

Sorry Paul I can't offer any help on that, but can I ask what do you mean by "training the drive" ?

I'm not familiar with that. Do you mean train the periodic error?

RB

beren · #4 22-09-2005, 01:19 AM

Seems like "rubber banding", a term that seems to be used to describe the symptoms you describe , the problem appears to be corrected by calibrating and retraining the drives ....training the drives enables the Autostar to determine how much slack is in the gears and the ability to adjust for it when the slewing key is released. Update to the latest firmware as well.Thats unusal with the final centering speed , i thought the Lx90 would be identical to the LX200

xstream (John) · #5 22-09-2005, 05:50 AM

It will be rubber banding Paul, check the Alt and the Az percentages and see what they are; from memory they should be approx 10-15%, Weasners site will give you the correct percentages.

As for the slow slewing finish I think you'll find High Precision is turned on under Setup turn it off, it's a pain the posterier.

If none of this works just whistle Paul.

http://www.weasner.com/etx/menu.html

[1ponders] (Paul) · #6 22-09-2005, 08:00 AM

I noticed the Alt and Ax percentages when setting up but didn't worry about them. Oh and I did do a motor callibration to. Will check it out. Thanks John.

acropolite (Phil) · #7 22-09-2005, 08:23 AM

I think it's probably rubber banding, the latest firmware has better default values, I think it's about 15% for each. Motor training is easy, but better done in daylight. When training do it only once for each direction and don't overshoot. Do a reset before you recalibrate and retrain as well then check the backlash percentages.

Eardrum73 · #8 22-09-2005, 09:14 AM

The LX90 mount is not the same as the LX200's... the LX200 has a more precise motorised mount - suppose to have larger arc seconds which is much better for photography. Hence the massive difference in price between the LX90 and LX200. (it wasn't just the apeture that was the difference.)

(the guy at the shop said something about the CPU being in the mount and not in the console or something like that amidst a myriad of other differences.....)

Meade is releasing their 10' and 12' with the LX90 mount in the next few months..... for the budget concious... still it will set us back about 4 - 6 grand.

Jonathan · #9 22-09-2005, 12:41 PM

I had the same "rubberbanding" problem with my ETX. I upgraded to the latest Autostar firmware, reset the controller and re-trained the drives and the problem has gone away. Apparently it only occurs in Alt/Az mode and not if its polar aligned.

MarkN · #10 22-09-2005, 05:01 PM

I had this "rebound" effect once and found that the RA lock on the base was not tightened properly. Wonder who the idiot was who left it so!

Astronomy being what it is, wouldn't be at all surprised to find that there were multiple causes of the one problem.

Mark.

rumples riot · #11 22-09-2005, 08:25 PM

Yeah Gadgets (Bob) scope does the same thing, must let him know to update his Autostar software. However, I found if I used sync on this object this would help to prevent the backlash.

Iddon · #12 22-09-2005, 11:10 PM

Sound like anti-backlash ?
And the Precision ON will cause the slow final slew to target I believe Paul.

acropolite (Phil) · #13 23-09-2005, 08:16 AM

You don't necessarily need to update the software to adjust the backlash percentages.

xstream (John) · #14 23-09-2005, 11:20 AM

As Phil stated, Firmware update is not necessary just change the percentages and that will fix the problem.

josh (Luke) · #15 23-09-2005, 12:00 PM

I have once had the same prob. I turned it off then on and calibrated the scope. Only took a minute or so and after that no probs again.
About the slow slewing, ive never noticed a big wait,normally about 5 seconds or so at the most to centre the target.
Had other probs like the Auto align not working the first few times and the autostar turning itself off. All is woking perfect now. Maybe it was just finding its groove.

[1ponders] (Paul) · #16 23-09-2005, 05:44 PM

Thanks everyone. I've taken it all onboard and next time I'm with them I'll give everything a go. I'll leave the firmware update til last. If its anything like the 200 it'll take a while.