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MtnGoat
Carpal Tunnel


Reged: 02/18/07
Posts: 1685
Loc: Columbia Gorge, WA
Can an LXD75 run a teensy bit slow (or fast)?
      #3054690 - 04/20/09 12:03 PM

I've been trying to figure out the source of a slight drift over time in my images.

I've got the polar nailed (pier mounted) and get the 'less than 5'' messages each time I do an alignment. This is supported by the fact that I get very little if any DEC drift over any period of time.

However I am getting RA drift, which to me seems to indicate a slight speed issue with the RA drive.

It is possible I need to dial the RA drive speed up or down a percent or two? (haven't analyzed if it appears fast or slow yet, I just know I have RA drift).

Is this something I would deal with using the 'tracking rate' field in Autostar, or by changing the gear ratio a tiny bit?

--------------------
"Ignorant people think it's the noise which fighting cats make that is so aggravating, but it ain't so; it's the sickening grammar they use." Mark Twain



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JAT Observatory
NOT a Wimp


Reged: 02/20/05
Posts: 8893
Loc: In the Primordial Soup
Re: Can an LXD75 run a teensy bit slow (or fast)? new [Re: MtnGoat]
      #3054803 - 04/20/09 12:41 PM

There is a menu item that allows you to set the % of sidereal tracking speed. You need to change the % number to increase or decrease the tracking speed.

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-Marcus

Hey what did you expect? After all, I am just a pig with a nice smile!



www.jatobservatory.org


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jgraham
Postmaster


Reged: 12/02/04
Posts: 11575
Loc: Dayton, Ohio
Re: Can an LXD75 run a teensy bit slow (or fast)? new [Re: JAT Observatory]
      #3054827 - 04/20/09 12:48 PM

Also, make sure the drive rate is set to sidereal and not lunar.

--------------------
-John

The best advice on imaging I've ever been given... don't forget to look!


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MtnGoat
Carpal Tunnel


Reged: 02/18/07
Posts: 1685
Loc: Columbia Gorge, WA
Re: Can an LXD75 run a teensy bit slow (or fast)? new [Re: jgraham]
      #3054886 - 04/20/09 01:12 PM

thanks for the tips so far. I'll make sure I check what my drive rate is set to.

am I crazy in thinking that the rate could need a tiny bit of tweaking? I mean...it's all digital timing with very accurate clocks and known gear ratios..how could this be?

--------------------
"Ignorant people think it's the noise which fighting cats make that is so aggravating, but it ain't so; it's the sickening grammar they use." Mark Twain



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sang33ta
scholastic sledgehammer


Reged: 07/08/08
Posts: 767
Loc: UK
Re: Can an LXD75 run a teensy bit slow (or fast)? new [Re: MtnGoat]
      #3055083 - 04/20/09 02:34 PM

Make sure your weight is balanced in both axis if it's out it'll drag or pull.

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Hioptic 152mm f12.5 Maksutov, CG5-AGT, Meade Super Plossl Set, Casio QV-2900UX


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gordianknot
professor emeritus


Reged: 09/04/05
Posts: 542
Re: Can an LXD75 run a teensy bit slow (or fast)? new [Re: sang33ta]
      #3055188 - 04/20/09 03:17 PM

I agree about checking balance. My first guess is that something is slipping.

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MtnGoat
Carpal Tunnel


Reged: 02/18/07
Posts: 1685
Loc: Columbia Gorge, WA
Re: Can an LXD75 run a teensy bit slow (or fast)? new [Re: gordianknot]
      #3055270 - 04/20/09 03:56 PM

yes, checked the balance. if anything, it's a bit too balanced! I was going for the slightly E heavy approach, but backed off on it when I started noticing this.

--------------------
"Ignorant people think it's the noise which fighting cats make that is so aggravating, but it ain't so; it's the sickening grammar they use." Mark Twain



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Skywatchr
Carpal Tunnel


Reged: 06/03/06
Posts: 2626
Loc: North-Central Pa.
Re: Can an LXD75 run a teensy bit slow (or fast)? new [Re: MtnGoat]
      #3056856 - 04/21/09 09:54 AM

The tracking rate can be affected by a small amount of extra friction somewhere slowing it down some. Could be the lube on the worm isn't spread out enough, or a bearing is dragging (polar bearing too tight), or something rubbing that shouldn't be. Being heavy on the East will slow it down a little unless it's only about an ounce or so. Just enough to take out any flex.

Jeff

--------------------
18" F/5 Home-Built Dob. with Mike Dudley Mirror
6" F/15 Brass w/ D&G Lens on DS-16 Mount
DS-10 10" F/4.5 Newtonian
LXD650 and LX200 Classic Autostar Converted!
DayStar 0.45 T-Scanner with multiple ERFs
11x80 Meade, 20x80 Celestron binocs (Vintage Japan Made).
A few Naglers and 8mm and 13mm Ethos.
Gadgets and parts everywhere.


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