I am testing different settings with my setup (listed below) and I have noticed that the amount of elongation/trailing increased rapidly once I expose for 600". I would expect to see a gradual increase in elongation as I increase exposure times.
What is it that causes this sudden change in star shape between 5-6 minutes and 10 minutes exposure time? (I'm thinking differences in polar alignment between imaging sessions, or perhaps the periodic error in the mount factors in)
should I limit my exposures to 300" and play it safe?
400mm - 240" - pinpoint stars consistently
100mm - 360" - acceptable results stars are round for the most part
100mm - 600" - elongation/trailing seen with all filters, most severe with OIII
Mount: EQ6-R Pro - PHD2 guiding
Filters: ZWO - L,Ha,SII,OIII
- Canon 400mm f/5.6L
- Canon 100mm f/2.8L macro