Guiding data

[emyliano2000]

Hi guys.

Last night, for the first time I used ATP to control the DSLR and the guiding.

I enabled the auto cancel exposure in the hope that I will get some shots with nice round stars but unfortunately most of the exposures were canceled with the "1" value in the Auto Canceling Distance box. I increased it to 2.54 (max) and still half the exposures have been canceled.

I downoaded the guiding log from my Lacerta MGEN but I have no idea how to read it and try to correct the guiding. This is the Guiding log. If somebody could please help me understand it.

https://www.dropbox.com/s/d3yuavpcp3gt2p4/MG000006.dat.content.zip?dl=0

I'm trying to generate a Periodic Error too but I don't know if I'm doing it right. I don't know if 10s is ok for the worm gear period, got it from googling EQ6 worm gear period.

 

By the way, should I do a PEC training before each imagins session?

Emil

 

[wimvb]

The worm gear period (= 1 revolution of the worm gear) is usually about 8 minutes (480 seconds). The number 10.2 seconds mentioned on the web is something else entirely. The pec training procedure needs to be at least as long as the period. If you do manual pec training, the mount will keep you busy for about 8 minutes, the correct worm gear period. Pec training with guiding software can take longer and go through multiple periods, in order to average out noise.

[emyliano2000]

2 minutes ago, wimvb said:

The worm gear period (= 1 revolution of the worm gear) is usually about 8 minutes (480 seconds). The number 10.2 seconds mentioned on the web is something else entirely. The pec training procedure needs to be at least as long as the period. If you do manual pec training, the mount will keep you busy for about 8 minutes, the correct worm gear period. Pec training with guiding software can take longer and go through multiple periods, in order to average out noise.

I have thought of entering 480 sec but I wasn't sure and that's why I went to google.

I will soon get the cable to control the mount from the laptop too and I will probably do the PEC trainin with the PECPrep V2.03

But still I don't understand the log data.

For example if I take this

What do they mean? Is it good, is it bad?

[alacant]

Hi.  Was APT connected to the mount at the time you took the frames? 

[emyliano2000]

5 minutes ago, alacant said:

Hi.  Was APT connected to the mount at the time you took the frames? 

no, I don't have the cable yet.

[wimvb]

I downloaded the zip file. Looking at the log, I interpret the data as follows:

The data starts with a 10 minute and then a 15 minute guided exposure which shows dec drift. This is most likely polar misalignment showing.

The DEC drift is only in one direction = polar misalignment

The RA drift shows a longer period, this is most likely due to pec.

You then have a large number of external  exposures. Did APT take over here?? I can't comment on these events.

What you could do on the next clearish night is to connect the Lacerta without bothering with APT or doing any actual imaging. Use a night to get to know your guiding setup. Let the Lacerta track a star away from the meridian for at least twenty minutes or so, without applying any guiding corrections (= guiding is switched off in both RA and DEC). The RA log data will then show your true periodic error plus drift due to polar misalignment. You should see about two full worm gear periods. The DEC drift will be due to polar misalignment.

Your guide star drift log should show something similar to this graph (the first 700 seconds)

After the 20 minutes have passed, turn on guiding, and you should see the guide star being brought back go the original position.

You can use the DEC drift to do a polar alignment as you would do a normal drift alignment. Track a star near the meridian and celestial equator for a while. Then adjust Az to keep the DEC drift flat. Then turn the RA to the eastern horizon and track a star. Adjust Alt to keep the DEC drift flat.

Don't use too short guiding camera exposures, otherwise you may be trying to correct for seeing conditions. No guider can do this.

 

Hope this helps some (and doesn't contain too many errors )