My 12" LX200 ACF was received back from a warranty repair on 2010-02-11 (the repair comprised a replacement of its control panel + new handbox)

Two days (2010-02-13) later the scope was taken back out to the observatory and reinstalled on to its equatorial wedge + pier 
The scope was setup with a revised optical train (taking out the F6.3 focal reducer + T.Agos Adapter which had been used through 2009)

Optical Train :	F/10 12" LX200 / Optec TCF-S /  CFW10 / ST-10XME
Expected Values
Expected Focal Ratio :	f/10
Expected Focal length :	3048mm
Expected Image Scale :	1x1: 0.46 arc sec /px,   2x2: 0.92 arc sec/px,  3x3: 1.38 arc sec/px
Expected Field of View :	16.5 x 11.5 arc mins
Actual Values	(determined on 2010-02-13)
Actual Focal Ratio :	f/9.7
Actual Focal length :	2960mm
Actual Image Scale :	1x1: 0.47 arc sec/px,   2x2: 0.94 arc sec/px,  3x3: 1.41 arc sec/px
Actual Field of View :	117.1 x 11.5 arc mins

Scope was roughly focused using main focuser, with the Optec TCF-S set at 3800 steps (just beyond its mid-point), and images were taken to determine image (plate) scale and rotate the camera to in lay very close to 180 deg rotation (leads up position)

Although the 12" LX200 was re- mounted onto a wedge that was already well aligned to celestial north pole axis (based on polar alignmemt of 8" LX200 last month), star drift check showed that  some adjustment to the wedge is required (to be adjusted at start of next session)

Slewed to South Sky Point
Measured Star drift (1)
Sky Position :	SOUTHERN SKY (Azimuth : 177.4 degrees)
First Dec :	-00 40 05.07
Second Dec :	-00 40 00.94
Time Interval :	4.12 min
Brightest Star Drift :	0.99 arc sec/min SOUTHWARDS
N/S Drift :	1.00 arc sec/min SOUTHWARDS
Polar misalignment :	3.84 arc min (approx)
Diagnosis (N.Hemisphere):	Telescope's polar axis is pointing too far east and needs to be rotated slightly anticlockwise
Suggested Correction :	a) Centre a bright star at Dec 0
	b) Jog W by 3.84 arc min. Check Jog Amount
	c) Rotate mount anti-clockwise until star is recentered
Measured Star drift (2)
Sky Position :	SOUTHERN SKY (Azimuth : 179.1 degrees)
First Dec :	-00 39 59.37
Second Dec :	-00 39 53.06
Time Interval :	6.15 min
Brightest Star Drift :	1.01 arc sec/min SOUTHWARDS   (Warning: Different brightest stars ? (Please check))
N/S Drift :	1.03 arc sec/min SOUTHWARDS
Polar misalignment :	3.92 arc min (approx)
Diagnosis (N.Hemisphere):	Telescope's polar axis is pointing too far east and needs to be rotated slightly anticlockwise
Suggested Correction :	a) Centre a bright star at Dec 0
	b) Jog W by 3.92 arc min. Check Jog Amount
	c) Rotate mount anti-clockwise until star is recentered
Slewed to West Sky Point  / Measured Star Drift
Sky Position :	WESTERN SKY (Azimuth : 271.7 degrees)
First Dec :	+16 15 23.47
Second Dec :	+16 15 29.89
Time Interval :	5.12 min
Brightest Star Drift :	1.26 arc sec/min SOUTHWARDS   (Warning: Different brightest stars ? (Please check))
N/S Drift :	1.25 arc sec/min SOUTHWARDS
Polar misalignment :	4.79 arc min (approx)
Diagnosis (N.Hemisphere):	Telescope's polar axis is pointing too high and needs to be lowered
Suggested Correction :	a) Centre a bright star at Dec 0
	b) Jog S by 4.79 arc min. Check Jog Amount
	c) Adjust wedge with clockwise (loosening) turn of the     latitude control knob until star is recentered (then firm up)

Deteriorating sky conditions prevented making any polar alignment corrections. This will be done at start of next session

As part of returning to imaging using my 12" scope with new optical configuration  focus offsets were determined for the principal photometric filters relative to the C (Clear) Filter. This was performed by taking images of a moderately bright star at different focuser step positions and determining the position of optimal focus from the resulting focus profile. 

Sky conditions and temperature changes required a number of repeat focus attempts, and deteriorating sky conditions meant that there wasn't time to recod focus offsets for Ha, RGB, U & S filters. Focusing quality was somewhat compromised by a degree of mis-collimation (collimation having been lost due to the two way journey of the scope down to England) 

Notes:
 1)  S Filter (#9) = Star Analyser 100 
 2)   All three setups used exactly the same camera to filter wheel distance.

 

Width of the profile at 10 arc secs FWHM is around 1425 steps (average)  

Theoretical CFZ (Critical Focus Zone)  =   (focal ratio)^2 * 2.2    (in microns)

Step size for  Optec TCF-S focuser = 0.000085" (or 0.00216mm,  or 2.16 microns)

PEC refinement was performed during session S413, based on an original refined PEC recorded during session S403