Unguided imaging tip

[kalasinman]

In the course of learning unguided imaging I had to learn to deal with periodic error. PE as the name implies is a repeating error that results from inherent defects in the mount. As far as I know all mounts in the low to medium price range have it.

The period is different for different mounts, but 10 minutes is common.

There is so much talk about achieving long unguided subs here and elsewhere, it's easy for a beginner to assume that longer is always better ( I did ). Actually in the world of unguided imaging, that has it's limits.

If you go for 10 minute subs, regardless of whether your mount can do it, you will be sure of having each frame rubbish as the PE is 10 minutes.

So develop a strategy that maximizes data collection per session. In the case of a 10 minute period, I've settled on 180 to no more than 200 second subs. At best one will net 2 out of 3 keepers. 140-150 seconds yields potentially 3 out of four, etc. For dimmer objects, I prefer to go with 180 seconds, as the longer subs give more detail on faint features. For brighter , better defined objects, 120 second subs yields 4 out of 5, a compromise I like also.-Jack

[kalasinman]

Admittedly the ultimate tip is to start guiding, which should eliminate PE from the picture and get you close to 100% keepers, tracking wise, as well as opening up the potential for longer subs.