Auto-guiding with an AZ GOTO mount?

[imichelena]

Hi folks! My name is Ignacio and I am quite new to this fascinating world of astronomy and astrophotography. I live in Coventry, UK and I got my fist scopes a few months ago (Celestron 130EQ and a sky-watcher Skymax 127 AZ GOTO).

I've been reading the info you guys share in this forum and with some try and error I've managed to take a few nice pictures of planets and the ring nebula. After a few months of experimentation and learning I realized I really like astrophotography and I'd like to take it to the next level.

Just last night I did my first test with a webcam SPC900 and PHD to see how auto guiding works. I've connected PHD to my mount via the serial connection on my SkyScan controller (my mount does not have an auto guiding port) and after doing the darks and calibration it seams to be working. PHD says that it is guiding and I can see the selected star moving around the centre of the green lines (not sure if is actually working or is just my regular guiding)

I haven't had the chance to actually use this while taking exposures as I am still waiting for my guide scope to arrive (I've attached the webcam to my main tube just for testing) so I am not yet sure of much accuracy I can really get with this setup.

I tried to find info about this configuration but I couldn't find any.  Have any of you guys tried this before? Can I actually get decent results with an AZ mount using auto-guiding? Is PHD really correcting my guiding even tough my mount does not have an auto guiding port?

I appreciate your help!

Cheers!

[glowingturnip]

you're going to get field rotation if you're guiding on an alt-az mount I'm afraid.  You'll find that the star you used for guiding will be nice and sharp in your final frame, but that all the stars around it will show some rotation around that point if you run your subs for long enough.

There's probably a max length of sub that you could go for that will leave the star trailing within acceptable limits that you can get away with, maybe others can advise there.

I connect PHD to my mount through my Synscan handset too, though it's an EQ mount.  If PHD got through the calibration steps ok and says it's guiding, then it is probably working.

edit: did a quick google - this page seems to explain field rotation pretty well - http://www.astronomyasylum.com/telescopemountstutorial.html

[imichelena]

you're going to get field rotation if you're guiding on an alt-az mount I'm afraid.  You'll find that the star you used for guiding will be nice and sharp in your final frame, but that all the stars around it will show some rotation around that point if you run your subs for long enough.

There's probably a max length of sub that you could go for that will leave the star trailing within acceptable limits that you can get away with, maybe others can advise there.

I connect PHD to my mount through my Synscan handset too, though it's an EQ mount.  If PHD got through the calibration steps ok and says it's guiding, then it is probably working.

edit: did a quick google - this page seems to explain field rotation pretty well - http://www.astronomyasylum.com/telescopemountstutorial.html

Hi glowingturnip!

Thanks for the info! I'll check it out

[jambouk]

Yes, you are limited to exposures under 30 seconds i suspect with the shorter focal length scope; much ahort times with the 127 mak probably.

Someone asked about guiding this mount on here before so hunt for that thread.

James