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Losmandy Titan 50 PE issue

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#1 magiclight

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Posted 08 July 2014 - 03:24 AM

Yesterday, I tested the periodic error of my 18month old Titan 50 as I noticed PHD making larger than expected RA guide corrections.
Currently I have a GSO 10” f4 Newtonian mounted on the Titan. The Titan is running on 18volts.
I used PECPrep, lodestar camera and PHD2 with ’Enable Guide Output’ unchecked to turn off guide corrections. I did two 30 minute runs (attached) near the equator and near the meridian.
I was expected PE of around 10” peak to peak however I am getting around 30” peak to peak. I shifted balance between the two runs. One east heavy and the other even.
My question is, is this a bad worm ? Should I switch the RA worm block with the DEC worm block and see if this improve things. Any other ideas to improve the PE??
Also I see G11 worms for sale at Losmandy. Is the G11 and Titan worms the same ?

Thanks Dave

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#2 Raginar

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Posted 08 July 2014 - 07:45 AM

It's something simple. Your mount didn't magically change over night :). My guess is you have a loose bolt somewhere running up to your scope. Or, your plate wasn't completely seated in the adapter. Or, it was cable drag.

The list is endless... but my guess is it's something in your setup. One plug would be to call Scott and see if he can walk you through some troubleshooting. He's done it before for lots of G11 users.

#3 David Pavlich

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Posted 08 July 2014 - 07:54 AM

Like Chris said, the list is about 6' long. :crazy: I'd start at the easiest fix like checking cables or loose bolts as Chris suggested and work your way backwards to the most complex part which is internal stuff.

I had a problem with an unstable CGE before I built my observatory. I found that the bolts holding the legs on the tripod were loose. :foreheadslap: Hopefully, it'll be something simple. :fingerscrossed:

David

#4 hungerford

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Posted 08 July 2014 - 08:19 AM

I agree this is probably something very basic. I had some issue with my Titan mount and after scratching my head for a couple of week I found out that the top mounted guider was loose and that made the guide absolutely atrocious.
The worm on the Titan is totally different from the G11. I even asked Ovision if they made a worm for the Titan but unfortunately the don't.
I hope you resolve your problem very quickly as the Titan is a very good mount.
Vince

#5 gdd

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Posted 08 July 2014 - 08:30 AM

The Titan uses a larger worm than the G11.

Is this your first attempt to use the Titan for imaging? Were you expecting 10 arcsec PE based on your prior experience with the mount rather than the specifications? You may not have noticed a 30 arcsec PE using the mount visually, but should expect performance equal to or better than the 10 arcsec specification.

Some loose connections I have contended with:
- Forgot to tighten the alt/az after polar alignment
- focuser not locked down tight enough
- MPCC adapter connection loose

Gale

#6 magiclight

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Posted 08 July 2014 - 06:18 PM

This is my first time imaging with it so I'm not sure if the mount has ever tracked any better. I thought 10secs RMS may be typical as this is what it says on the Losmandy specs.

I'm using an OAG.

Nothing appears loose on the mount or imaging train.

#7 gdd

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Posted 08 July 2014 - 08:58 PM

The spec says +/- 5 arcsec which would be 10 arcsec peak to peak. The RMS is not spec'd but should be much lower.

Depending on the coma corrector you selected these imaging newtonians can have a long stack of heavy equipment hanging on the end of the focuser creating a lot of stress and flexure on the focuser and the OTA tube. Do you have your focuser in the standard down position for imaging?

The OAG should mask the tracking problems, but you should be getting better results for unguided. Did you verify that unguided imaging for 318 second subexposures produces star trails in agreement with the PEC tool results? Do it for a star near the celestial equator.

If you can't find a cause for the high PE give Losmandy a call.

Gale

#8 magiclight

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Posted 08 July 2014 - 09:52 PM

Gale,
Sorry I meant +/- 5 arcsec P2P.

The Moonlite focuser is parallel to the ground so I could try it in the down position.

Good point, I should try to verify with an unguided 318 second image.

Thanks
Dave down in NZ

#9 gdd

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Posted 08 July 2014 - 10:58 PM

My setup illustrating the focuser in the down position.

Gale

#10 magiclight

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Posted 09 July 2014 - 03:55 PM

Yes, my setup is the same in the "counter weight down" position.

#11 Raginar

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Posted 09 July 2014 - 08:33 PM

Sounds like you're pretty new to this. How is your balance? Did you do it both in RA and declination? Did you have all your gear on it the way you'll image with it? Where did you get the mount? Was it shipped? Have you tried re-meshing it?

Again, you can solve all this with a phone call to Scott. He'll pick up the phone and tell you how to troubleshoot it. And, he doesn't care if you bought it new/used/whatever. Best customer service ever.

#12 magiclight

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Posted 09 July 2014 - 09:25 PM

Balanced slightly east heavy and evenly balanced in DEC. Full image train was setup. OAG and guide camera, Baader Coma corrector, spacer and QHY 8L camera.

I re-meshed it 18 months ago shortly after purchase.

The Titan should handle the 10"f4 without raising a sweat.

I bought it new from Optcorp in the US and had it shipped down here to NZ.

Yes, a call to Losmandy might be the answer.

#13 Hilmi

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Posted 10 July 2014 - 12:47 AM

I don't own a titan but I do own a G11. I know that with temperature changes I have had to re-mesh at least 3 times a year as expansion and contraction changed the tightness of the gears. I read the same in a review of an older titan on the internet. I would say you might need to re-mesh again.

18 Months is a long time to have not worked on the worm mesh.

#14 Jeff B

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Posted 10 July 2014 - 11:46 AM

I don't own a titan but I do own a G11. I know that with temperature changes I have had to re-mesh at least 3 times a year as expansion and contraction changed the tightness of the gears. I read the same in a review of an older titan on the internet. I would say you might need to re-mesh again.

18 Months is a long time to have not worked on the worm mesh.


I had the same issue with my GM100. In the warmth of the sun, the mesh got tight and the drive would chatter. As it cooled at night, everything was fine.

Had to do a bit of tweaking to get it just right.

Jeff

#15 Raginar

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Posted 11 July 2014 - 08:35 AM

CALL HIM!!! :D






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