M56 and M71

[p1taylor]

Hi All, I think there is something not right with theas images, all help gratefully accepted.

peter

[nmoushon]

Looks to me like your focus is out a bit. Also maybe exposure time a bit too long and stars are blowing out a bit. But hard to tell if its that or focus. Think its the focus though. What where the specs for these images?

[p1taylor]

FWHM = 5.67 and 4.68, prosest in maxim and photoshop CS3.

peter

[rfdesigner]

with a 10" cassegrain, that's a lot of focal length. I don't know how good the tracking is on the RCX what's the focal length on your guide scope?

How did you focus?.. that looks a bit out too, you mention FWHM, is that in pixels or arc seconds?

Sorry to be all questions, just that one of the answers may show up the problem.

Derek

[p1taylor]

Hi Derek, Tracking is good according to PHD log, RCX is 2032mm f/l on a wedge, guide scope is ZS 80II ED f/l 610mm, digital focuser 0.01mm in slow in very slow a good bit les, I think it is pixels for FWHM, hop this helps.

peter

[rfdesigner]

That means your lodestar is guiding at about 2.5 arc seconds per pixel.

if seeing was 2 arc seconds FWHM that would equate to 0.8 arc seconds rms, and on your lodestar that comes out at about 0.3 pixels. I'd want PHD to be reporting less than this as your RMS guide error on a 1 or 2 second guide frame rate.

Derek

EDIT: your FWHM suggests 3.77arc sec x 3.11arc sec. First they should be equal, I assume the 3.77 is East-West and the 3.11 is North-South, which points at guiding hurting your performance. Also you should be doing better than 3.11 in dec if your mount is as good as I think they're supposed to be.

So it looks like you might have a very slight focussing issue too.

[p1taylor]

guiding.bmpHi Derek, Sorry I think I may have misled you the FWHM is what Maxim reports for focus one for each image, enclosed is a screen shot of what PHD is doing, hope this helps thank for all your help.

peter