Drive problem??

Hey All
I was out last saturday night and i took a few pictures using my 10" f5.8 mounted on EQ6, i had the mount aligned and it appeared to be tracking ok. But nearly all of my picuters had a problem. So i went out again last night and did a bit more work on setting up the mount but i still get the same effect. See the link below of a small area of the pleides, notice how the stars seem get exposed in one area and then there is a shift where the star starts to get exposed at a different location. Can any explain this or tell me what should i be looking at to sort this? The pictures i took last
saturday had a similar effect as can be seen in the picture of andromeda?

&lt;a href=" photobucket.com " target="_blank"><img src="/ i226.photobucket.com/albums/dd110/mlkcampion/IMG_1118.jpg " border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>

&lt;a href=" photobucket.com " target="_blank"><img src="/ i226.photobucket.com/albums/dd110/mlkcampion/IMG_1002.jpg " border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>

The camera is setup at prime focus with a remote shutter control and with the mirror lockup function enable.

Thanks

Sorry i put the wrong link in


i226.photobucket.com/albums/dd110/mlkcampion/IMG_1118.jpg

i226.photobucket.com/albums/dd110/mlkcampion/IMG_1002.jpg

hmm, that looks like periodic error to me in the first image and the second image looks like periodic error in addition to a slight misalignment to polaris. Could be wrong though.

I think the EQ6 has a PEC (periodic error correction) function. As far as I remember (at least on the heq6) the mount can have up to 30 arcseconds PE, but when trained it can be brought down to a fifth of that.

Trev

Do not know if this will help or not but if you purposely misalign the mount and then take a long exposure you will see the "shape" of oscillation that causes the error. A random zigzag could be wind / backlash. A regular pattern would be drive error.

Another possibility...

I'm not so sure that it is all down to PE. The stars in both pictures look like the mount was kicked during the exposures, producing a noticable shift. Now, assuming that you &gt;didn't&lt; kick your mount on both nights, I would point the finger of blame at either a loose RA-axis lock (it may have slipped during the exposure) or there is some other problem with your RA-drive - whether it be too stiff for the motor to move (and so moves in jerks) or a dodgy bearing. It might be worth dismantling the EQ-head and giving it a close inspection.

Jed Glover's and Dave Gradwell's G11 mounts both suffered from lubrication grease that had dried up to the consistency of hard varnish, paralising the needle bearings and resulting in uneven tracking. I cured both mounts by stripping them down and soaking them in kerosene overnight before giving them a thorough scrubbing with an old tooth brush. After cleaning them up and reassembling them with a light grease they both worked perfectly.

Dr. Phil.

Thanks

Unfortunately i only have the standard EQ6 controller and as far as i know that doesn't have PEC or backlash compensation. I wasn't sure until now how much of an effect PEC would have and these exposure are both hardly 6 minutes long.

I will try you test mjs and i actually was thinking of pointing the scope in different directions (i.e. zenith, due south e.t.c) and do long exposures at each position do you think this might give clues?

I have the mount about 3 years now and i have only started to use it but definately i will take a look at the gears? Is there a special grease needed for the gears due to low temperatures?

Cheers for the suggestions.