Catastrophe. Please help me

[DavidB]

I bought a NexStar 130SLT last October and have not really been able to use it since because of illness and cloud cover. However this evening I was taking it out in what seemed like perfect viewing conditions. Unfortunately the tube slipped out of its mount just as I was exiting the garage and crashed to the floor. I was in shock for a considerable time but it still seemed to work OK (although there is a crease mark now in the tube body) and I had a good couple of hours looking at Mars (but still not seeing much) and the Orion area.

However after this time the goto on the mount, which had not been damaged, started to play up and I could not stop the traverse when I pressed any of the direction buttons. It just continued past where when I wanted it to stop and I had to press the opposite button to stop it. It then whizzed past the point I needed in the other direction. This happened both horizontally and vertically. I tried the ultimate of switching off then switching on again but it still continued to play up.

Please can anyone suggest what is happening and how I can correct it. It completely spoilt the rest of my evening and I had to resort to a bottle of red and an hour of television to keep my sanity. Why fail on this of all nights? Any ideas gratefully received.

[Helen]

Sorry to hear of your troubles David

How are you powering your mount? A common cause of runaway slews etc (my fork mounted scope tried to do a backflip once ) is a low power supply. If you are running it from ordinary batteries which you haven't used for a while that might be a problem. Or a partly discharged power tank... The cold can affect batteries too.

HTH

Helen

[jgs001]

Sorry to hear about the tube, it sounds like it's all good though. I'd agree with Helen, how are you powering the mount ? Whilst it has the option to fit AA batteries, they really aren't man enough for the job...

[rwg]

I have had exactly the symptoms you describe from low battery power in my SLT mount. Slews go the wrong way, won't stop, etc...

I find that rechargeable NiMH AA batteries are good for several hours before getting problems, but it's actually *not* a good idea to buy the very highest capacity rechargeable batters. Anything higher than about 2200mAh tends to have a high self-discharge rate, so if you leave the batteries unused for a few weeks, you find them nearly flat. I try to buy 'hybrid' rechargeable batteries, about 2100mAh which are designed to hold their charge longer, since they are sold as 'pre charged rechargables'. Search for 'hybrio' batteries.

I've also had trouble with the tube falling out of the SLT mount (mine is the 102 refractor, which fortunately also survived). After the second time I glued some thin rubber heatshrink materieal to the inside of each jaw of the clamp to provide better grip. I expect cut up cycle inner tube would be good too. See this thread : http://stargazerslounge.com/diy-astronomer/96063-slipping-dovetail.html

Robin

[DavidB]

Many thanks for your help. I will try the inner tube to keep the scope in the mount. I was actually in shock for a about fifteen minutes when I thought the whole shebang would be bits of glass and twisted wire inside the tube. These things can take quite a battering can't they? Or was I very very lucky I wonder?

The battery problem. I was using the AA batteries that came with the scope last October. I didn't realise they did not last long. It got pretty cold last night as well, which I guess would not have helped.

I did buy a couple of sets of hybrid rechargable batteries for when the present ones ran out. Just didn't realise they would run out so soon. I will put them in and try again when we have a good night again.

The night was not completely lost because I had a good go at Mars and a trip round Orion before the problems started. It is really wierd when the star you wants goes at high speed across the eyepiece view!!

I have since read up on the battery situation and it seems the very best to have is a caravan battery. Have started saving the pennies because there is nothing worse than having to admit defeat after an hour and a half on a perfect evening for stargazing.

Once again, many thanks for the information. Good old Stargazers Lounge.

[barkis]

Hi. David.

You must have got a fair old fright when the tube hit the deck. Hopefully though, no lasting damage.

I just worry about the crease in the tube you mentioned though. How severe is it? There is a chance it could have thrown your collimation off a bit. It would be worth checking it out if you find the Images are not as good as they might be.

Ron.

[DavidB]

Thanks Ron. It was a worry. After it happened I went out with some trepidation but all seemed OK. However I am a newcomer to this so don't really know how the scope should behave. There is a guy called Carl who lives near me. I haven't met him yet but he has offered to help. However I didn't want to bother him. I think I might take him up on his kind offer now though.

David B.

[Capricorn]

The battery packs do not really have the oomph to power goto's all that well. And as said the cold will not help.:(

One other point rechargeables are rated at 1.2volts, normal AA, AAA are rated at 1.5volts. So rechargeables will be somewhat down on the required voltage even when fully charged.

If you now think along the lines of a power pack then remember that they have standard lead acid batteries in and they cannot be fully discharged as they tend to not survive being discharged.

I use the mains/car adaptor set ups that you can get for around £25. As everything else seems prone to going wrong. Then again I have managed to blow the mains transformer end of one of these. (It was my fault however):rolleyes:

[The Warthog]

I have a dent in my OTA, caused when it slipped out of my hands when I was demounting it. Hasn't been a problem. I can still collimate it just fine. You should be OK.

[DavidB]

Oh dear, what can i do?

Sky isn't black, and I'm feeling blue

Tell me Oh, what can I do? (apologies to the Beatles)

AA batteries aren't up to it for goto units. Hybrids are possibly the wrong voltage. Lead acid batteries not the best. Mains transformers are no good in the middle of Salisbury Plain where the darker skies lurk. And piggy bank has been hidden by wife. I guess this is where I beg borrow and steal then experiment.

Perhaps I should change my eye piece addiction and start using the microscope which is in the same cupboard as my (very) old Tal. At least I would not be at the whim of the weather.

Must stop drinking this red wine in the middle of the day.

[Capricorn]

The mains transformer thingys are a mains to 12v DC plug unit.

Then the wire bit has a car connector on it that plugs into the 3 pin plug bit.

To get to the middle of Salisbury Plian I am guessing you drive.

Plug the car connector bit into the car.

That was why I bought mine, not to use off of mains but to use from the car.

Then you have the full capacity of the car battery at hand.