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SanDiegoPaul
professor emeritus
Reged: 07/22/05
Posts: 598
Loc: San Diego
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I guide & image with both cameras in same orientation at all times. USB cables from both cameras are oriented to come out on the right side (3:00 position) and I do not use any diagonal between the scope and the cameras.
PHD guides very well in RA but my images drift UP in the screen, in between each shot. In a series of 5-minute images, each successive one will be a few pixels higher than the previous.
I've tried telling PHD to guide NORTH using the Dec drive but it didn't work. I've reset the aggressiveness of the adjustments and had no luck. Now it's back to default settings and still doing so.
My Polar Alignment appears fine. I can drift 10 minutes in RA or DEC and get absolutely no drift from the star I'm looking at in the crosshairs.
So if my alignment is good, then the DEC drift HAS to be coming from PHD, right? The scope obviously knows it's in Polar Mode, so when following a star the DEC drive motor should be turned off.
If I'm reading ~that~ correctly, then it's a software issue not a hardware issue. Can you help? 
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Meade 10" Lx200-R with Moonlight SCT Focuser
Mitty Evolution Wedge
AT-80 Guide Scope
SBIG ST402ME CCD Imager
Canon Digital Rebel DSLR
Meade DSI-c CCD for Guiding
Please visit my gallery!
http://www.pbase.com/sandiegopaul/
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Joel
Carpal Tunnel
Reged: 07/08/04
Posts: 2307
Loc: Merrimack, NH
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I've had the same reaction the last couple of nights I've been out Paul. I did some fine tuning a couple of weeks ago with my polar alignment and then it seemed to be staying dead center.
I think it may be bad seeing. The last couple of nights I've been out the seeing was 1/5 or 2/5. Maybe couple of weeks ago the seeing was better but mine drifts up in the video window which actually would be down in relation to the scope.
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Joel
10" LX200GPS UHTC-SMT
Vixen 80EDsf
Canon unmodded 350D
QHY8
Turkey Hill Observatory
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wrather1
AstroBear
Reged: 10/25/05
Posts: 2918
Loc: Dallas, Texas
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I had exactly the same experience as Paul last week. My guide star kept drifting UP on the screen, and I could not get more than 3 minutes per exposure before PHD "lost" the guide star. I attributed it to poor polar alignment since seeing and transparency were letter-perfect that night.
I'm also gonna try out the latest version of PHD once the Moon goes away. I think my version of PHD is outdated.
DW
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"Don't worry about what telescope you own, or its quality. Just get out under the night sky, and enjoy God's wondrous universe." - T. M. Back
Meade RCX400-12 on JMI trolley "Ursa Major"
TMB 130SS on EQ6 PRO "Ursus Polaris"
Orion ED80 "Ursa Minor", WO ZS66ED "grab-'n'-go"
Canon EOS 30D (Hutech), Meade DSI, Philips ToUcam Pro
North Texas Clear Sky Chart
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SanDiegoPaul
professor emeritus
Reged: 07/22/05
Posts: 598
Loc: San Diego
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I think I'll re-join Craig Stark's Yahoo! group and post on there too. Stay tuned.
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Meade 10" Lx200-R with Moonlight SCT Focuser
Mitty Evolution Wedge
AT-80 Guide Scope
SBIG ST402ME CCD Imager
Canon Digital Rebel DSLR
Meade DSI-c CCD for Guiding
Please visit my gallery!
http://www.pbase.com/sandiegopaul/
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MartyT
professor emeritus
Reged: 09/28/07
Posts: 522
Loc: Kansas City
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Lots of possible causes:
* The exposure time on the CCD may be too short and you're chasing bad seeing. Try stretching it to 2 to 5 seconds, or if your CCD won't go that long, there's an option on the settings screen to tell PHD how long to wait between updates.
* Backlash settings may be way off
* Are you *sure* DEC guiding is enabled in PHD? Did PHD calibrate in both RA and DEC?
* Flexure between guide scope / camera and main OTA?
If your polar alignment is good enough, you don't need corrections in the DEC axis.
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Celestron CGE / C-11 (CGE-1100)
Megrez 90 FD APO / 0.8x FR/FF III
QHY8
Modified Canon 350D (Baader UV/IR Filter)
DSI Pro (guider), SPC900NC
ETX-125AT
Meade 12" Lightbridge
Astronomical Society of Kansas City
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SanDiegoPaul
professor emeritus
Reged: 07/22/05
Posts: 598
Loc: San Diego
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How do you know what backlash to set it to?
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Meade 10" Lx200-R with Moonlight SCT Focuser
Mitty Evolution Wedge
AT-80 Guide Scope
SBIG ST402ME CCD Imager
Canon Digital Rebel DSLR
Meade DSI-c CCD for Guiding
Please visit my gallery!
http://www.pbase.com/sandiegopaul/
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Bill W.
Pooh-Bah
Reged: 10/09/05
Posts: 1437
Loc: Western PA, USA
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I would guess it's backlash. Start at the lowest setting PHD has for backlash and gradually increase it. You don't want to over do the backlash setting.
-Bill
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Orion Atlas EQ-G (EQMOD), SBIG ST-2000XM & AO7
Stellarvue SV66ED
Skunk Hollow Observatory
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Bill W.
Pooh-Bah
Reged: 10/09/05
Posts: 1437
Loc: Western PA, USA
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I also wanted to add... make sure your balance in dec is very good. You can adjust the backlash in the hand controller. Start at 5 and work your way up towards 99. You can look through the eyepiece. Then, put the scope on a slow slew speed and look through the eyepiece to figure out when your close in your backlash setting. As you're adjusting the backlash setting you'll notice that the 'lag time' it takes to do a correction decreases. You want to have almost no lag time or very little.
-Bill
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Orion Atlas EQ-G (EQMOD), SBIG ST-2000XM & AO7
Stellarvue SV66ED
Skunk Hollow Observatory
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