M45 Pleiades

shot at PTC
18~135mm zoom @132mm
F5.6
ISO800
3 min x 7 subs
resized to 25%

to make the star without trails is always challenging

done:

• polar scope is better collimated , so that error is 5' to 10' ( 1/4 to 1/5 of 40 min polaris-NCP angular distance) . Now using , done based on astronomyshed's method

• use sturdier tripod

things to do:

to further reduce the polar scope error,
the scope still have "cone error" , reasons can be
- the polar scope optics not in good optical alignment,
- the polar scope arm is not always orthogonal to the polar scope, when the polar scope is rotated
- something else.

All in all, whether the polar scope arm is in parallel to RA axis of the mount, is another question

 change the grub screw to big heard thumb screw
use drift method to increase accuracy