PEC, Stacking and Autoguiding

So, now that I have my first moon shot under my belt, its time to cast out a deeper. My next goal is to be able to pull off something like this:

https://photography-on-the.net …hp?p=13736887&p​ostcount=1

In doing the research, I am a bit confused about the relationship between PEC, stacking and autoguiding. I understand each term, but not the interaction.

So, my understanding is that periodic error comes into play with long exposures. If I am doing relatively short exposures of 1-2 min (the above pic was 2 min) and then stacking them, wouldn't the stacking make the adjustment for an individual sub being off because of the PE? I guess the PE could cause an individual sub to be blurry?

And where does autoguiding fit into this?

Confused in California.

Thanks,

Omar

Autoguiding requires a lot set of equipment altogether to correct any drift both of the azimuth and declination axis. Basically it requires a guide camera mounted on a guide scope with a guiding software to correct any drift on both axis. Autoguiding with take care of any PEC error so you don't have to do PEC for your mount if you are guiding.

Stacking is to improve the signal to noise ratio and has nothing to do with guiding.

Periodic error (PE) causes the tracking axis to move at different speeds and the worm wheel rotates. That causes the scope to move slightly faster or slower than it should, which can cause small amounts of star trailing. For short subs, it will likely be negligible, but it won't be zero, and it's not something that stacking can fix by aligning the subs as it processes them. That said, don't worry about it while you're still learning this stuff; it's not nearly as important as getting a good polar alignment and/or good guiding.

Cool--thank for the education, folks.

Omar