Celestron 102 SLT hand controller problem

[majestic0110]

Hi all I hope you are well. I was out stargzing this eve with the above scope and after an hour or so the battery operated hand control would not swivel the unit right, it worked ok in other directions. then it stopped slewing it down and a bit later it woldn't go left either. I tested it again when I got home with the same batteries and it seemed fine. What might be causing this? The same behaviour occurred last night, first it wouldnt slew right, then it stopped slewing down and left. These were the same batteries. Is there a problem with the hand unit do you think or is it just dying batteries? It is interesting to note that this behaviour didnt occur in the firts hour to an hout and a half of usage.

[malc-c]

Batteries don't last long in these scopes. When rested, the batteries will regain a little charge - you're doing good to get an hour and a half out of them. Best investment is a power tank (assuming the mount runs of 12v) or get a couple of sets of re-chargable batteries and just keep swapping sets over

[ronin]

The cold and batteries do not mix well, and you mentioned you had used them before.

Problem with rechargeables is that they are 1.2v not 1.5v so you are 20% down even with fully charged ones and recharegeables dislike the cold even more.

You need a power tank, but do not allow it to discharge fully or you will need another, or a mains supply if you are running it at home - Maplins do a reasonable range.

[majestic0110]

Hi guys, thanks very much for the responses. I think you are right, the batteries were extremely cold when I removed them from the scope so I imagine it is a temperature issue. I then put them back in at some stage yesterday afternnon and they were working fine again. I believe that the batteries are near the end of their life but as malc-c said I think they must have regained a little charge. I am going to try out a new batch this evening and take my scope out again (weather permitting of course!)

[Cjg]

Do be wary about using rechargeable's -have found that in the past, even with high power NiMH batteries, the first alignment worked okay, but subsequent ones would be out, the error getting progressively worse as the evening went on - leading to much frustration.

The problem was solved when I ran the scope from the mains. Failing that, there's numerous threads here about using battery starters etc ti power a GoTo.

Chris

[malc-c]

Found an idependant review here http://www.cloudynights.com/item.php?item_id=2530

It’s a sweet little thing to use, draws only 0.14A off 13V when tracking at sidereal rate and 0.43A peak, then 0.3A average, when full speed slewing both motors. So a 7Ah battery should last a couple of nights in normal use.

If it's drawing an average of 300mA then my guess is that after around an hour or so the batteries are reaching the threshold where they can not maintain drive, so first one motor fails and the then other (normally the DEC motor goes first).

Celestron tend to use servo motors in their mounts rather than steppers as featured in the Skywatcher range, and what effect a low voltage / current will have on the ability to move the mount between the two types I'm not sure. Best bet is to pop down to Maplin and get one of those booster packs as suggested, or if you are observing from home then a 13.8v regulated mains PSU housed in the house / shed with a 5m - 10m run of good quality Low Voltage cable to the mount should fine http://www.firstlightoptics.com/slt-series/power-cable-celestron-slt.html