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Night of good seeing. Collimation checks were made to see why image quality has been generally poor.
poorer seen collimation was performed at the end of
the last session (S360).
Final estimated collimation error was around 3 - 4 arc secs, compared to a
immediately prior collimation error of 14 arc secs (and compared against original first light
collimation error of around 35-42
arc secs).
It was unclear why the collimation error immediately prior to re-collimation
attempt (14 arc secs) was rather less than the measurements made during session
S358 (31-37 arc secs) (Mirror slop ?, seeing).
To investigate the collimation behavior of the scope, a collimation check was made on a star field lying at around 52 deg altitude. Collimation error (20-25 arc sec) appears to have increased from that shown in the last session, but is still lower then measurements made during S358. It would seem that whilst sub-5 arc sec collimation was not reliable, a 10 arc secs improvement was nevertheless made.
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Collimation Measurement - 2009-04-01 (post Re-Collimation) |
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CCD Inspector plot 15s sec exposure, 2x2 binning, C Filter (#360292) 12" LX200R (at f/5.7) + ST-10XME |
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Collimation Check - 2009-04-05 |
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CCD Inspector plot 20s sec exposure, 2x2 binning, C Filter (#361021) 12" LX200R (at f/5.7) + ST-10XME |
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Table of Collimation / Curvature Measurements - 12" LX200R (at f/5.7) + ST-10XME
Session Images Stars
Aspect
Ratio
Curvature
Collimation
(arc secs)Average FWHM
(arc secs)Tilt X Tilt Y Total Tilt S356 (First Light Session) 30 x 30s 148 +/- 13 38 % +/- 20% 16 % +/- 1% 41.6" +/- 6.3" 5.4" +/- 0.7" -0.9" +/- 0.1" -0.3" +/- 0.1" 16% @ -157 deg S356 (First Light Session) 6 x 60s 410 +/- 22 38 % +/- 10% 27 % +/- 1% 35.0" +/- 6.5" 5.3" +/- 0.3" -1.1" +/- 0.2" +0.5" +/- 0.1" 20% @ -149 deg S357 collimination attempt S358 7 x 90s 575 +/- 40 19% +/- 8% 24 % +/- 2% 36.3" +/- 6.3" 5.5" +/- 0.4" +0.9" +/- 0.2" +0.1" +/- 0.1" 15% @ - 5 deg S358 6 x 45s 633 +/- 73 14% +/- 3% 21 % +/- 2% 31.7" +/- 7.6" 4.9" +/- 0.4" +0.7" +/- 0.2" +0.3" +/- 0.1" 10% @ - 22 deg S358 3 x 60s 695 +/- 80 16% +/- 6% 24 % +/- 1% 36.1 +/- 4.0" 5.9" +/- 0.6" +0.9" +/- 0.1" +0.1" +/- 0.0" 14% @ - 9 deg S360 2 x 20s 199 +/- 1 16% +/- 4% 22 % +/- 3% 13.9 +/- 1.3" 4.0" +/- 0.2" +0.6" +/- 0.1" +0.0" +/- 1.0" 12% @ - 9 deg S360 3 x 20s 184 +/- 27 27% +/- 5% 24 % +/- 6% 14.7 +/- 1.5" 4.2" +/- 0.3" +0.5" +/- 0.1" -0.1" +/- 0.1" 12% @ 19 deg S360 - Collimation attempt S360 - Post Collimation 4 x 20s 223 +/- 13 17% +/- 1% 17 % +/- 3% 3.7 +/- 1.0" 4.0" +/- 0.1" +0.2" +/- 0.1" -0.1" +/- 0.1" 4% @ 20 deg S361 2 x 20s 412 +/- 65 14% +/- 1% 22 % +/- 1% 25.1 +/- 5.7" 4.5" +/- 0.1" +0.8" +/- 0.1" -0.4" +/- 0.1" 15% @ -33 deg S382 (Alt 33 deg) 2 x 5s R 271 +/- 8 17% +/- 2% 22 % +/- 1% 37.9 +/- 2.0" 3.6" +/- 0.1" +1.0" +/- 0.1" 0.7" +/- 0.1" S382 (Alt 51 deg) 2 x 20s VR 322 +/- 32 18% +/- 6% 18 % +/- 2% 26.1 +/- 8.3" 3.4" +/- 0.2" +0.8" +/- 0.2" 0.4" +/- 0.2" S382 (Alt 65 deg) 2 x 5s R 113 +/- 7 12% +/- 2% 26 % +/- 2% 21.6 +/- 4.1" 3.1" +/- 0.1" +0.7" +/- 0.1" 0.4" +/- 0.1"
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Focus positions for the C Filter were collected over an 18
degC temperature range of the course of several observatory sessions (Primary
mirror locked in same position throughout)
The dataset is plotted below. Best fit line indicates
The dataset shows considerable scatter and a session specific
adjustment to datum focus position is frequently required to account for night
to night changes in best focus. A clear reason for this has not yet been
determined
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| This Web Page: | Notes - Session 372 (2009-08-07) |
| Last Updated : | 2015-05-16 |
| Site Owner : | David Richards |
| Home Page : | David's Astronomy Web Site |
