Telescope drive motor / batteries question

[Christopher Ferro]

I have a Meade TeleStar scope that has a tracking motor. The battery holder is a plastic thing that holds 8 AA batteries, but that holder has a typical 9V battery connector that mates to a 9V connector for the motor. Since the AA batteries have 1.5 V each, that makes a 9V battery pack. Can I use a 9V battery in the thing, or will that kill my motor?

CJSF

[TravisM]

It depends on how those 8 AAs are wired. I'm guessing in the + to - config, where they're stuck end to end train-car style...
In that case, you'll have (1.5v is approx...) about 9~10 volts to play with from those 8 AAs. I think you oughta check the amperage to be sure, but it should be fine.
Post a picture of the thing with and without the AAs and I'll try to see if I can help further. Also, if it has specs in a book or on the case, post them here too.

[Christopher Ferro]

I don't have an easy way of taking a picture of it. (No, I still don't own a digital camera. Actually, the only cameras we have are one-time use ones). The batteries are in two rows of 4, one row stacked on top of the other, the + and - sides alternate.

The Telescope manual doesn't say anything other than "use 8 AA batteries and connect them to the 9V adapter." I'll go back and read it after work, in case I missed anything. It certainly doesn't say "Warning, don't use 9V battery!"

CJSF

[Christopher Ferro]

The cool thing is that I collimated it myself the other night! I've had the thing for almost 2 years, but haven't been able to use it much. I finally joined the area astronomy club and figured I get it all niced up to start using regularly.

The truth is, I've been partly scared to use it and the light pollution is pretty bad at our apt. We've done some lunar viewing and Jupiter as well. I got a fairly good look at Mars for the 2003 close approach.

I've thought about driving it out a ways to some darker location, but then I worry about damaging it in transit. Finally, I just got fed up with it. What's the point of having a telescope if it just sits in the living room looking pretty?

Anyway, the batteries I have are losing their juice. I have a new 9V and wondered if I could just use that.

CJSF

[SarahMc]

It's probably a 12 volt system; most are these days. Get a VOM and check the output with the AA batteries installed (use new batteries). I know my kid's ETX 125 is 12 volt, and it uses 8 AA batteries as well (or at least it used to until I got a 17Ah rechargeable for it).

[Christopher Ferro]

It's probably a 12 volt system; most are these days. Get a VOM and check the output with the AA batteries installed (use new batteries). I know my kid's ETX 125 is 12 volt, and it uses 8 AA batteries as well (or at least it used to until I got a 17Ah rechargeable for it).

[checks back pocket for a VOM]
pat - pat - pat
hmm...

Nope, no trusty VOM... ;-)

I'll see if I can borrow one.

CJSF

[TravisM]

Radio Shack has decently cheap VOMs for a limited price, but you can just get one of those adjustable AC adapters... but that kind of defeats the purpose of 'portable.' #-o If the amperage output matches something you can plug into your car's cigarette lighter then you might be in business...
Also, try a lantern battery, the big square ones with spring connectors on top, usually 12v. Not sure on the amperage though...

[tlbs101]

Connecting a 9V battery probably won't hurt your motor drive unit -- of this I am not absolutely certain because I don't have all the details of the motor drive unit, but I am 99% certain. However, the 9V battery probably won't provide enough power to effectively drive the telescope.

You can try a 9V battery -- it might keep the telescope tracking for a short period of time, but then it will quickly lose power.

There is nothing "magic" about the 9V connector and that adapter. That particular adapter/connector is just what Meade chose to use in that unit. With 8 AA batteries the voltage will be nominally 12V. By using AA cells, the available current will be much more than that of a single 9V battery, thus the total available power will be much greater.

(I am making a reasonable assumption based on experience, that the battery pack connects the batteries in series.)

[Christopher Ferro]

First, thanks for all the replies, everyone.

Part of my confusion is due to hunger induced alternative mathematics. Naturally 8 AA's is 12V not 9V. #-o

That, combined with a 9V connector made me think a 9V battery would work.
But now that I think about it, maybe it's 6 batteries.

Dang it. Just hold on until tonight when I look at the thing again and get it all squared away. I may try some observing too - since it's supposed to be clear tonight.

CJSF

[Charlie in Dayton]

A pair of 6v lantern batteries IN SERIES (+ lead to BATT1 + terminal, BATT1 -terminal to BATT2 + terminal, BATT2 - terminal to -lead) will give you 12 VDC, and it'll last one heck of a lot longer than a double handful of AA's. You also might want to investigate those rechargeable power packs for RC cars or cordless tools, or drop a few buckolas on a good-sized rechargeable power source (Celestron's Power Tank and Orion's Dynamo Pro have rechargeable batteries from either 110VAC or 12VDC sources, various types of takeoff jacks and voltages, built in white and red spotlights, and the Deluxe models have hot chocolate and cold beer spigots, depending on if you buy the Summer or Winter Equinox Specials...).


...okay, I was kidding about the very last part...but other than that, ain't I great at spending other people's money? 8-[

[Kaptain K]

For a lot less money than one of those "Astro-special" power supplies, you can go to Wal-Mart (or Target or ...) and get a lawn tractor battery and a trickle charger.

[Russ]

Sorry to get into this so late CF but I've had other things to do.

Regarding the 9volt style connector. It is just something they used so they could buy a standard part. I'm sure it's not intended for you to use a 9v battery in the scope.

The AA batteries are 1.5 volt so 8 of them in series will produce 12 volts. If you attach a 9v bat. to the connector your scope systems (motor/computer) will work for a while (motor too slow) and then will burn out due to over current. The computer may not work at all.

Most of the Celestron and Meade scopes are set up to run off car batteries which in the USA are 12v. While you can cheat a little with the voltage on either side of correct (10.5-11v or 13-14v) it's not a good idea. If you must cheat it's better to go a little high than low.

If you don't want to us the 8 AA's you can Jurry rig the mating 9v connector to other 12v sources. As CID pointed out, you can series wire 6v lantern batteries or direct wire a car battery. The small motorcycle batteries are also 12v and can be direct wired. They will have much more staying power than the AA's and you can recharge them with cheap equipment. Usually the older guys at Radio Shack know enough that they and draw you a wiring diagram for an alternate 12v system. :D

[Charlie in Dayton]

Electric kiddie-car 12v battery for $50, the appropriate charger for $19 at Wally World...

To be on the safe side, consider sealed batteries ("gel cells"). If they tip over or vent during charging, you won't have acid spraying out and eating holes in things (this is The Voice Of Experience speaking here...), and they seem to hold a charge longer than traditional lead-acid, due to the electrolyte not evaporating.

Also consider (in the sealed battery line) the cells for emergency power failure lights above doors in public buildings. The chargers are cheap (trickle chargers for small cap batteries), and lots of places go through and replace those batteries every couple of years, whether they're needed or not. I've scored a few of those in my day, and a charged one will run my hand-held transceiver literally for weeks before charging is needed. We're talking 5 - 7Ah batteries here, the same sort of stuff that's inside the 'astro-special' power supply. A charger, and a few cigarette-lighter sockets from ElectroJunk'R'us, and you're in business.

[Christopher Ferro]

Thanks everyone for the input. I don't normally get to post over the weekend, so sorry for not posting sooner.

Of course, you are right about the 12v vs 9v... hunger induced alternative mathematics, there! I'll just stick with using the good ol' fashioned 8x1.5 AA batteries for now.

BTW, I thought I had collimated my scope, but now it's worse than before. I think my mirror locking screws don't lock or something. I'll have to wait until the next club meeting to get someone to help me with it.

Thanks everyone, again.

CJSF