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rmuhlack
24-02-2012, 09:41 AM
Last night's efforts, and my first decent go with a guided exposure. Took a chance and went for 8 min subs.

Turned out that PHD lost the guide star 5 sub exposures from the end of the program (and I wasn't watching it constantly to notice...) so i was left with 13 x 8min subs. Rejected 2 subs in the stacking process with DSS, and then tweaked the curves in Darktable to give the resulting image.

My camera mod has moved the focal plane forward slightly, and so now i think im getting some slight coma in the corners even with my MPCC. Not sure how I can correct this (as i'd need to move the CC closer to the camera body, and its already flush with the t-ring) - guess in due course i'll just need to move to a cooled CCD :)

With an ambient temp of ~22C there looks to be a fair bit of noise as well, so maybe 8min subs is pushing it a little at this time of year with my un-cooled DSLR. Need to get thinking about that cooling mod...

So in the end:

11 x 8min subs @ISO800
20 darks
5 flats (I took more but they were twilight flats and i was too slow in between each shot and the sky illumination changed)
20 dark flats

comments, advice appreciated :)

Edit: larger image available here: http://astrobin.com/5884/

scagman
24-02-2012, 11:30 AM
Hi Richard, That looks good, nice colors. Pity about the guide star.

orion58
24-02-2012, 01:05 PM
Very nice image - good job... :thumbsup:

rmuhlack
24-02-2012, 02:19 PM
thanks :)

Another thought I just had is whether the slight elongation could be due to colimation error (particularly re the secondary?). It could be my imagination, but the issue seems more pronounced in the top left and bottom right, rather than the other diagonal corners. Is this astigmatism from a secondary, or something else :confused2:

peter_4059
24-02-2012, 02:39 PM
Nice Rosette Richard. The elongation in two of the might be tilt. I had it in one corner and squaring the focuser up seemed to improve things.

multiweb
24-02-2012, 05:42 PM
Nice shot. :thumbsup: Got some Ha on this one last night and hope to complement tonight to smooth things out.

Visionoz
24-02-2012, 10:43 PM
Not bad at all Richard!:thumbsup: - own mods + imaging the Rosette

I've been in this since 2009 and still haven't imaged the Rosette yet!:(

Cheers
Bill