how to correct field rotation

[skywatcher250]

hi all, so i am planning to start using a logitech webcam on my alt az DOB (with goto) and want to have a go at imaging... skipping past the whole EQ mount thing etc is there a way to de-rotate the alt az field of rotation that anyone knows of (whether using registax or some other software) this will mean that certain other objects moon and jupiter exclusive will become possible.

thanks in advance

[michael.h.f.wilkinson]

I think Registax and Autostakkert! have the option to derotate. On short avis there should not be too much of a problem anyway (and on long avis you get other rotation problems with Jupiter).

[haitch]

You could spend £X00s on a field de-rotator that rotates your camera the opposite way to the rotation or you could just align them in your stacking software for nowt (rotation isn't an issue really with planetary images)

[Cornelius Varley]

I assume that because you are imaging with a webcam / dob you will only be imaging planets and the moon. If this is the case field rotation won't be a problem. Stacking software such as Regitax will be able to rotate the indivual frames when stacking.

[skywatcher250]

initially yes - however ive seen amazing results with DSO's from some people with the same kit as me, which is mainly y i was enquiring

[dph1nm]

DSS will take out the relative rotation between exposures when stacking. However, to avoid rotation *within* an exposure when on an alt-az mount you have to limit your individual exposures to around 1min or less (depends where you are pointing in the sky). However, with a 10" scope you should get pretty decent results with subs this length.

NigelM

[knobby]

I'll be watching this thread with interest, Paulus17 has just produced some cracking stuff with his 127 mak on an Alt Az.

[skywatcher250]

thanks Nigel ! ill start with that then - 1 min exposures it is then

[dph1nm]

There is a technical item explaining how exposure time varies with position in the sky here: http://autostarsuite.net/forums/storage/19/4981/field%20rotation%20v3.pdf

Basically don't point anywhere near the zenith!

NigelM

[ursamajorro]

Learn to use WinJupos. It's a powerfull tool, especially for those who own a Alt-Az mount.

Tutorials.