Thanks for all the input guys.
My connections to the scope is like this.
Laptop USB>GPUSB>AP900 guideport
Laptop USB>USB hub>SXVF-H9 (connected to SX EXview autoguider via direct serial connection), DMK21
Laptop USB> Keyspan 4 port USB - serial Hub>AP900
Image aquisition> Maxim
Guiding> Phd or Maxim (via guider relays or GPUSB for the SX autoguider, or GPUSB if using DMK via Maxim. (swapping guider relay cable and GPUSB cable over as required, checked each time))
No ascom being used.
My drift alignment is very very good. >0.3 pixel/min drift (both alt and az) using DMK & VC200L via K3CCDTools. Easily achieve 3 min unguided shots with negligible Dec drift.
Standard AP PEC is on, thought over 3 min there is noticeable PE movement. Mount will need to be retrained.
The mount is well balanced and has been checked a number of times.
For the past few weeks when I have been able to get out to image my standard startup routine is:
- Start Laptop
- Hook up USB cables
- turn mount on
- select location 1 and goto (as per manual)
- Resume from Park
- Select Object;star; usually a star to the east and south (as that is where I'm likely to be imaging)
- goto
- start Maxim and/or not phd> center star in Maxim (and phd, guiderings are good and tight and 1 sec exposures will always allow me to find a good guide star when I need one)
- sync on star
Now normally at this point I would goto a star near the object I want to image and refine my alignment and check focus and then goto the object I want. In recent weeks I've only been shooting stuff from the E the S SE corner and at least 45 deg in elevation, 5128, 3372, 3621 etc.
- Image acquisition procedure:
- Center object
- Calibrate for guiding using either Phd stand alone with DMK21, or using Maxim via GPUSB for DMK 21 or SX, or maxim via guider relays using SX. Never had a calibration fail.
- Set image exposure times and quantities.
- Start guiding, start capture
My SXVF-H9 is attached to the VC200 via 2"+ diameter threaded extensions directly to the focuser and the focuser lock bolt is tight. Up until 2 nights ago my guidescope was WO72 using either a Meade flip mirror or star diagonal on SBS mount, now I'm using 50mm Stellarvue finder in over under with Losmandy guiderings tight. All have been rock solid and I was not able to find any movement in the system even giving it a good hard wobble by holding the WO or the SV. Guide Camera mountings have been and still are good and solid. Checked and double checked and checked again.
Now the pattern of movement appears to be strongly as though the initial mount movement is in equal amount south and west showing a strong movement. As the night progresses and the mount is pointing more vertically the star movement reduces gradually until it is only moving slightly as though the mount is moving southerly, but only minimally. This is what convinced me it was flexure. Now however I am not so sure.
2 nights ago I shot 5128 for 5 min and got strong SW movement as per 'normal'. Cloud came in and i slewed across the meridian to M46 (around the same elevation). I took 2 x 5 min shots and there was no sign of any pronounced flexure. When the sky cleared I slewed back to 5128 and did another 5 min shot. No movement, yet if i had stayed there, going by previous experience, it should have continued to show flexure.
Going by this experience, last night I did my normal alignment procedure and aligned on a star to the eastish but then slewed across the meridian, re synced on Sirius and then shot M46 again. No movement. I immediately slewed back to 5128 and shot 20+ x 5 min shots with no movement (barely a pixel movement between shots in Dec south) and then 17 shots of M83 again with no movement (except pixel movement in Dec south)
So by doing a calibration run on the guiding in the west first and then coming back to the east has somehow removed (?) the problem.
Oh and btw all my guiding graphs prior to 2 nights ago have always been tight and clean whether using PHD or Maxim.
Got me
