M108 1hr 51 min exposure with OMC300 at FL 2967mm (Rick Evans)

M108 1hr 51 min exposure with OMC300 at FL 2967mm

Posted Today, 10:26 AMLast night was mostly clear, but high thin clouds passed over from time to time. M108 is getting a bit low in the sky and I thought this might be my last good chance to image it. Even though the moon was quite bright, it wasn't near Ursa Major. I used my OMC300 f9 Klevtsov variant of a Maksutov Cassegrain that I bought new from Orion Optics in the UK about 2009. It isn't made any longer but there are smaller versions that are. To image M108 I chose not to use a focal reducer, and a specific one was never made for this scope which I think was considered mainly for lunar/planetary work. The OMC300 is on my G11 Galaxy 1 mount. My guide scope is not adequate for work at focal lengths greater than 1500mm and my setup last night had a focal length of 2967mm. So I only used it, connected to PHD2 and APT for dithering. I don't have a specific OAG for this scope so my decision was not to guide at all, just to track. Even though the Losmandy is a good tracking mount, exposures had to be limited to 15 seconds to avoid mis-shapen stars. Every 30 exposures I took a minute to re-center M108 using APT's Point Craft feature. I collected 481 subs of 15 sec each. A small percentage showed mis-shapen stars and some were affected by clouds. I was able to stack 446 subs in Sirl. I did not bother with flats, darks, or biases. My camera was a ZWO ASI6200MC and I used it binned 4x4 for about 1.15 arc sec/pixel resolution which I thought was appropriate to local seeing conditions.

Original
Final
B

B

Title: M108 reprocessed

Description: Reprocessing using Photometric calibration in Sirl.

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Status	Advanced success
Started	...
Astrometry.net job	5982483
PixInsight job	LDDVX7NLDSKZV1LZJRC7MIBSGBCLN593
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	11h11m41s.43
RA (top/left)	11h10m33s.46
RA (top/right)	11h10m45s.71
RA (bottom/right)	11h12m48s.70
RA (bottom/left)	11h12m37s.49

Dec (center)	+55°40′54″.3
Dec (top/left)	+55°50′01″.5
Dec (top/right)	+55°30′19″.2
Dec (bottom/right)	+55°31′44″.6
Dec (bottom/left)	+55°51′30″.1

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