G-11 woes....

Lee · #1 03-09-2006, 06:48 PM

Not really woes yet.... frustration really....

no first light yet, unless you count the living room light!

Problem - motor stalls and RA motor lag

Mount seems well balanced.
Power supply - truck battery pushing 12V

Mount slews to do pretend aligns, most of time - others get motor stalls, then usually once a successful slew - I get RA motor lag....

From what I've heard its likely worm tightness (damn worm tightener!)....

Any suggestions to fix/alleviate while I wait for support from merchant?
Any suggestions on fine tuning balance?

Any help would be appreciated - cheers guys....

Dennis · #2 03-09-2006, 06:57 PM

Hi Lee

I don't have a G-11 and am not familiar with its operation, but I am familiar with the "new mount blues" syndrome. So much is promised “out of the box”, yet this is seldom the experience when you first begin to use these mounts.

Even these top end mounts rarely provide an "out of the box" experience. My Vixen GPDX and Takahashi EM-200 required me to interact with them, to learn how they work in the field and then tweak them to get them working correctly. The GPDX required a re-grease and worm adjustment in the end.

Once you have overcome these early issues, I'm sure the G-11 will give you many years of excellent usage.

Cheers

Dennis

bird (Anthony Wesley) · #3 07-09-2006, 05:41 PM

G'Day Lee, sounds to me like you're a bit low on voltage/current for the motors. I also had problems with stalls when I tried to run on a 12v car battery. I don't do that anymore.

Try using a 15v/3A supply from d1ck smith or Jaycar. That will fix the problem. The mount can take up to 18v without complaint and I have found this gives the motors more torque.

cheers, Bird

bird (Anthony Wesley) · #4 07-09-2006, 05:46 PM

ps it might also be a tight gear. I eventually gave in and took the cover off the RA worm housing to fiddle with mine. If you allow yourself plenty of time (a rainy weekend afternoon is perfect) then you can adjust and re-lube the worm. Getting it right is more of an art than science.

After a lot of reading around to find the right sort of lube for the worm and gears I was reccommended to use "SuperLube", a synthetic lube that has really good temperature tolerance and lasts for a loong time. I bought a tube of the stuff from farnell and it'll last me a lifetime.

cheers, Bird

rogerg (Roger) · #5 07-09-2006, 06:26 PM

I have a GM-8, but...

a) I once had problems where the mount would slew a bit and give a error on the screen and stop. People thought it was the slew limits, but it was the cmos battery needing replacing

b) check the slew limits perhaps

c) worm tightness - hmm, I doubt it'd have such an impact especially if your mount is well balanced, I'd expect it to have more of an impact on tracking accuracy (PE, backlash, slop, etc).

d) correct mount type specified in the gemini menu? think it defaults to Titan.

e) voltage - my GM-8 really likes runnning on 17v, 12v it struggles a little.

Hmmm... that's about me out.

Roger.

Lee · #6 07-09-2006, 06:30 PM

Cheers for your reply....

I have adjusted the worms, after speaking to the vendor I purchased from and doing some www research (God bless the web!). Runs fine now from the battery - I have noticed a 13.8V up to 12A regulated supply at Jaycar for $70 - will pick one up for home use.

Must say I was a tad

that the worm needed adjustment out of the box! I wasn't whinging about not getting sub micro-arcsecond tracking, I just wanted the mount to not stall when trying to move! Not a big ask I think......

Anyway - gripes over now! Now I just need to learn to polar align it - have improved already, my first goto missed the moon.......

Lee · #7 07-09-2006, 06:31 PM

Another thing - although I knew it didn't come with a power supply when I bought it - but why not???? Seems to me a power supply giving ideal voltage should come with the thing - would save moans and groans from customers!

rogerg (Roger) · #8 07-09-2006, 08:21 PM

When I bought my 12" LX200 (classic) several years back, it arrived new and straight out of the box the it had "RA Runaway" where it just kept spinning in RA immediately it was turned on.

I think you need to be a technician (of all trades) to own a medium to high quality telescope mount.

I once thought "fridges 'just work' out of the box, why don't telescope mounts??".

Re power supply - GM-8 doesn't come with one, I guess it's one way they can save on cost, when probably 1/2 the people using it won't need one.

Roger.

JohnG (John) · #9 08-09-2006, 09:50 AM

Lee

As the owner of both a G-11 and GM-8 for quite a number of years, you WILL need to become familiar with the workings of the mount. I would suggest that you join the Losmandy Yahoo Group, in their archives is an enormous amount of information from a lot of very experienced people.

As you have fiddled with the worm, I would suggest that you use the hand paddle and slew to the safety stops in either direction to make sure you haven't tightened the worm on another hight spot or that you have loosened it to much, there is a fine balance between over/under correcting the worm and having a lot of backlash.

The newer G-11 and GM-8 have a different grease now so you should have no need to change that.

As you have a Gemini, I would suggest that you become familiar with it prior to going out under the stars, there are a few new user traps that will get you. You can set it up in your house or garage and slew to targets etc. As already said, check the Gemini and load your mount parameters, Lat and Long, Timezone, UTC Time (important).

As you have found out, the G-11/Gemini combination is sensitive to power requirements, I use a 13.8/10 amp GME power supply with no problems. Just about any problem with the Gemini Unit can be traced back to the CMOS battery so be aware of that.

Have fun learning

Cheers

JohnG

xelasnave · #10 08-09-2006, 10:32 AM

I am happy to have seen this thread. I have been thinking about nothing else but get a new mount get a new mount, but all you have all said tells me to hang on to the lxd55 and eq5 and make them work in spite of themselves. I thought that all the other mounts never had problems but no doubt it is part of the business and one would be foolish not to become sckilled at working on your mount as not to rely on outside help. So I should put off a new mount until I can figure the current ones and better understand a good mount when it arrives
alex

Striker (Tony) · #11 08-09-2006, 10:47 AM

I am running all my equipment of some 2x 12volt 17AH batteries permantly connected to a 4 AH battery charger.

Everything is running of the cigarette lighter fittings.

1) Losmandy G11
2) Sbig ST402XME cooled ccd camera
3) Cooled Canon 350D
4) Dew buster with 3 dew heaters

All works fine with my set up.

Make sure you set the time right UTC time 10 hours behind current EST..I made that mistake...thanks to 1Ponders fixing it up for me.

JohnG (John) · #12 08-09-2006, 11:05 AM

Hi Alex

I was lucky, my mount worked just fine out of the box, worms etc were at the correct tension and I am fussy in that regard, that said though, a lot of mounts, including hi end mounts, AP, Tak, SB Paramount etc do need some work to get them right, you have to learn the workings of your mount to do this.

Cheers

JohnG

Lee · #13 08-09-2006, 11:23 AM

John - I did famil myself in the living room initially, and was happy, with a VERY ROUGH polar align it seemed to point OK, then noticed it said Spica was above horizon, when I knew it wasn't - I had the month set to 8 instead of 9....

Come to think of it, I didn't think my polar align roughness should have caused 30deg errors!

Tony - I am savvy with UTC/GMT/Z/K/L time and adjustments, having just spent 5 months in the Middle East where we had to work in numerous time zones on the hop..... no problems there.

I am going to get a 13.8V DC supply though - will be less back strain than the 70AH deep cycle battery - I should be able to run half a dozen mounts at a star party with that bad-boy!

Now I just need some more clear nights!

Does anyone have any hints for painless (or less painful) polar aligning - I noticed Gemini has polar align corrections in it, where it slews to where a star *should* be, then you alt/az correct it - does this work nicely? - the manual claims accuracy to about 2'.....

JohnG (John) · #14 08-09-2006, 11:44 AM

Hi Lee

In your living room it doesn't matter where the mount is pointing, on startup just use Warm Restart, you can then slew the mount anywhere, you let it bypass Align Mount. Most people get trapped by the Synchronisation and Additional Align menus, practice these in your living room, if you get Additional Align Rejected messages, you have not followed the manual correctly.

When you input, it is important that you follow the manual correctly, one of the most common mistakes is to input your UTC and date in the wrong format.

The Gemini Polar Alignment procedures are reasonably accurate and they will get you close although a Drift Alignment is the best way. You can see how close you are by looking at the A and E numbers on the hand controller, they will start off quite large when you do a Cold Start but get lower after your Additional Align's. Make sure you at least 4 - 5 on one side of the Meridian before you cross over and do further aligns.

On your intial startup, you only need to be within about a degree or two of the pole, gemini will guide you in then.

Cheers

JohnG

Lee · #15 08-09-2006, 12:03 PM

Thanks John - I did a very basic align (ie altitude set to 33deg, pointed basically south) - so I'd know easily if it slewed the wrong way.... The date format is unusual (yymm.dd from memory....), had to look that up in the manual....

I am getting the hang of the align and additional align menus now - did seem unintuitive initially though....

I didn't read the bit about doing several on one side of the meridian first, and was hop-scotching back and forth across it doing aligns - that's when I missed the moon on a goto I think

I figure I'll use Gemini to get as close to the pole as possible, then drift align to get the gold.... I'm only going to start some basic piggyback imaging soon, so I'm not starting drift aligning yet!

Geoff45 (Geoff) · #16 08-09-2006, 12:43 PM

Quote:

Originally Posted by JohnG

Lee

As you have found out, the G-11/Gemini combination is sensitive to power requirements, I use a 13.8/10 amp GME power supply with no problems. Just about any problem with the Gemini Unit can be traced back to the CMOS battery so be aware of that.

Cheers

JohnG

Can you tell me more about the GMe power supply? Where do you get one? How much? Does it run off a battery or do you need AC power?

I have just got a GM8, which I'm intending to run off a 70AH battery.
Geoff

JohnG (John) · #17 08-09-2006, 12:56 PM

Hi Geoff

My setup is in a dome and I have 240 power direct to my equipment, I dont have any moisture problems.

I power my mount with a GME PSA 1210, see:

http://www.gme.net.au/land/power_products.php

My G-11 with Gemini requires about 3 amps from memory so at 13.8 volts and 10/11 amps this unit is more than satisfactory for my purpose, To avoid the possibility of a ground loop, I use a smaller 2 amp power supply for the ST-4.

If you dont have a gemini on the GM-8, it only uses about 500 milliamps so a battery setup would last all night with no problems.

Cheers

JohnG

JohnG (John) · #18 08-09-2006, 12:57 PM

Lee

Meant to say before, if you still get motor stalls, drop your slew speed down, I use 800 and have never had a stall.

JohnG

Lee · #19 08-09-2006, 01:05 PM

I did drop it - to 600 I think - may try speeding it up a tad now its working.

Have just realised I changed three things at once -
1. loosened worm
2. top-up charged the battery (voltage under load only increased from 12.1 to 12.6V though)
3. slowed slew speed to 600 from 800.

I plan on tweaking the worm now it is working, but am getting a 13.8V supply today to use at home anyway. I really didn't loosen it much though - added about 0.1mm clearance with feeler gauges..... enough to give a little backlash though....
I'll get there!

Panotaker · #20 08-09-2006, 05:13 PM

I use my G11/Gemini for astrophotography and have never done a drift alignment. I just use the Polar Alignment Feature, works like a champ. I do an alignment on 6 to 8 stars on the east side of the meridian, then do the PAC. Then do 5 or 6 alignment stars on the East again and finally a few on the west and I am good to go. The PAC is very accurate, but I guess you can do a drift to fine tune it. All this is true if you use a refractor. If you are using a scope with a flopping mirror, like an SCT, then your better off doing a drift alignment.

I got a gps hooked up to mine so I don't have to worry about putting in the wrong time or place. The GPS does that automatically.

For visual, loose worms are not that big a deal. For photography, you have to spend some time adjusting them tighter until they are right before the stall stage.

On 12 volts, you pretty much have to slew at 800. On 18 volts, you can slew faster.

For accurate alignments, and goto's, you will need a cross hair eyepiece.

Enjoy your new mount.
Ralph