Any advice welcomed.

[spaceboy]

Hi All

Any idea why I am getting these stars. I have attempted to drift align the mount as polar scope alignment was not offering anything over 40 seconds. I have this unguided image that shows odd looking stars at 5 minutes exposure.

1st pic is a 5 minute exposure and 2nd a 10 minute just to comparison.

Again below those is 2 x minute exposures but one is showing star trails where the other is much better.

Is there a need to PAE even with drift alignment ? or is there a good chance I fluffed the drift alignment ?? I would have thought if the alignment was out there would have been more obvious star trails not what I am getting.

[JimStan]

The squiggly lines look to me that you have periodic error in your drive train. This means that for visual work, you would probably not notice the effect at all, but due a slight speeding up and slowing down of the output arm holding the scope itself, and a possible minor vibration, for whatever reason, the image is registering on the sensor and showing where the light is being shifted around due to that unevenness.

Sometimes a lot of PEC can be eliminated by checking the "mesh" of the gears in the drive train itself. Generally, the first gear that is attached to the stepper motor of the "clock" has a slotted mount that can be adjusted to make the drive run freely without binding, or the opposite effect of "slop". The better the drive, the more precise the drive mechanism might be.

Guiding may be the only way to eliminate virtually all noticeable effects of PEC, and there are many threads on this forum that discuss that subject.

Hopefully, this will help!

Jim S.

[spaceboy]

Thanks for your input Jim. I think I have found the problem as being poor grease on the drive train and I am looking to service the mount again so will have to adjust the worms at the same time. Hopefully this will sort the problem ???

[garethmob]

it does look like PE sadly spaceboy one thing that might help, when your taking the images perhaps do many exposures and count how many of them show trails and then only stack the non trailing ones, i found on one mount that with 10 30s images only 5 were useable, i usally check all my images first delete any that have any distortion then i bung the remainders into DSS

what mount is it?