www.astrocafe.hk

Date 4 Dec 2011
Time 12am
Telescope: Microtech R200
Focal Ratio: F4
Camera: 300D
ISO:800
Location: Shui Hau Observatory http://shuihau.hkas.org.hk
Mount: HEQ5
Guiding: SG4
Filter: CSL
Stacked by DSS

If there is no sign of guiding error in SG4, there maybe flexure. The stars were elongated in one direction.