Wednesday, October 3, 2012

Observed brownish hue on the western inner walls of Eratosthenes listed in ALPO/BAA LTP catalog

Dr Anthony Cook from BAA/ALPO TLP Coordinator reports that he "will add the Galdies observation to the LTP catalog with a weight of 1, just to encourage observers to try to replicate the effects seen. At least the color was not too dissimilar to that seen by Paul Abel and others back in 2009, and also lay in terrace shadings, but in the case of the Abel observation, was more confined to the NW".
The Lunar Observer, September 2012

  
Color images of Eratosthenes by Charles Galdies. Philips SPC 900NC PC camera (color space/compression YUY2) on a Nexstar 8SE telescope. Air temperature 27.5C, dew point 21.8C, wind 9.3 km/h SSW, 15 km visibility i.e. a clear sky. Each image is a result of running Registax 6.0 using 3000 frames, with 95% best frames and wavelet transform. Further processed for reproduction in the newsletter, with a contrast stretch and slight increase in color saturation. North is towards the top left. (Far Left) UT19:44:11-19:45:01. (Centre Left) UT 19:47:28-19:48:18. (Centre Right) UT19:48:19-19:49:08. (Far Right) 19:50:33-19:51:23.

1. OBJECTIVE: Verification of the following historical LTP:

2012-Aug-25 UT 19:30-19:50 Ill=64% Eratosthenes observed by Abel_P on 2009-11-25

On 2009 Nov 25 UT18:42-21:03 P.Abel, T.Little and C.North (Selsey, UK,
15" reflector, seeing II-III, transparency very good), all saw visually a brownish tinge on the north west rim of Eratosthenes crater. P.Abel
made a sketch and T.Little took some high resolution CCD images, some
of which were through coloured filters. Checks were made for spurious
colour, but none was seen elsewhere on the Moon. The eyepiece was
changed but this made no difference. M.C.Cook (Mundesley) was observing
with a smaller scope at the same time, but saw no colour, however
observing conditions were worse. W.Leatherbarrow (Sheffield, UK) was
observing with a instrumenet mid way in size, and saw a brownish tinge
in the NW rim area, but saw a similar colour elsewhere and put this
down to spurious colour. Normally multiple observers seeing the same
thing would result in a weight of 4, however as this was only observers
at Selsey and some of the evidence contradicts, I am allocating an
ALPO/BAA weight=3.


Sketch of Eratosthenes showing brown on the NW rim. Drawn by Paul Abel from 2009 Nov 25 UT 18:42?-20:18. North is towards the top left.

2. METHOD

Equipment & Software Used:
Nexstar 8SE
NEQ-6 Pro mount
Philips SPC 900NC PC Camera
SharpCap, Registax 6.0
LTVT: advanced software tool for lunar topography. 

Atmospheric conditions @ 1800UT:
Ambient air temperature: 27.5degC
Dew point: 21.8degC
Wind: 9.3 km/h SSW
15km visibility
Clear sky

Comments on CCD settings, data capture and processing:
The Gain setting of the camera was adjusted to emphasise the illuminance and colour of the  inner western walls of Eratosthenes. Background detail was not deemed as important and is therefore seen in a rather low illuminance. For normal, routine imaging of the lunar surface, higher Gain values are normally used to keep a balanced level throughout.

No colour filters were used, and camera settings were kept consistently the same throughout the observation session.

[Philips SPC 900NC PC Camera]
Resolution=640x480
Frame Rate (fps)=60.00
Colour Space / Compression=YUY2
Exposure=-4
Brightness=64
Contrast=32
Saturation=0
Gamma=15
ColorEnable=255
BacklightCompensation=0
Gain=45

The total number of images sometimes exceeded 6000 per CCD session. However, because of Registax restrictions, image stacking was done for batches of up to 3000 images taken at 60 fps.  

No post-processing of the final stacked image was performed, other than wavelet transform using Registax.

3. RESULTS

LTVT simulation (for physical data) at start and end of the recording period: 19:44:11 UT &  19:52:14 UT





















Data analysis and comments:

UTC
From:
UTC
To:

Appearance and/or comments

(if brightness being measured, enter value in last column)

19:44:11
19:45:01
Rather low illuminated western inner walls, with a very slight hint of colour change

19:47:28
19:48:18
A hint of a reddish-brown hue is evident in shadowy areas of the western inner walls of the crater. No other area within the image exhibited this change. Most prominent colour change occurred at: Long: 12:04 o W; Lat: 14:78 o N with a sun altitude of 2.16o degrees and azimuth 92.14 o degrees (data taken from LTVT)

19:48:19
19:49:08
Prominent brownish colour still evident but with some slight overall diffusion. Most prominent area however remained located at: Long: 12:04 o W; Lat: 14:78 o N with a sun altitude of 2.17o degrees and azimuth 92.14 o degrees (data taken from LTVT).

19:50:33
19:51:23
A slight change towards a brownish, diffuse colour was detected. The diffusive effect seemed to have diminished, but this may be due to transient atmospheric conditions. Turbulent conditions probably increased due to decreasing altitude of the moon (altitude=32017” @ 19:48UT).

19:51:24
19:52:14
Brownish, diffuse shadowed colour still evident but of conspicuously less intensity than at 19:48 UT

19:52:15
-
Observation terminated as previous timing of this LTP report expired



LTVT Predictions of the same phenomenon:


Colongitude = 14.682  with  Solar Lat = -1.519
Librations and Moon/Sun positions calculated for observer at 14.260°E  35.520°N  85 m

                          Terminators      Sub-Solar Point      Librations      Center of Moon      Center of Sun
   Date      Time UT   Morning   Evening    Colong    Lat.     Long.   Lat.      Alt.     Azi.       Alt.     Azi
25/08/2012  19:48:45  14.682°W 165.318°E    14.682  -1.519    1.483  -1.308    26.600   208.829   -24.841   305.091  +%
24/09/2012  07:47:05  14.682°W 165.318°E    14.682  -1.283    4.993  -4.970   -63.708    54.156    33.285   119.059  +
16/07/2013  17:58:45  14.682°W 165.318°E    14.682  -1.429   -6.686   2.112    39.791   191.834     2.710   294.320  +
15/08/2013  05:05:24  14.682°W 165.318°E    14.682  -1.495   -4.823  -2.052   -72.715   340.013     7.665    78.245  +
13/09/2013  16:46:10  14.682°W 165.318°E    14.682  -1.155   -1.422  -4.638    32.522   162.243     4.612   271.066  +
06/06/2014  16:29:15  14.682°W 165.318°E    14.682  -1.161   -4.779   3.958    49.652   151.343    19.260   284.629  +
06/07/2014  03:27:29  14.682°W 165.318°E    14.682  -1.507   -7.245   0.950   -52.505   307.748    -5.378    57.088  +
04/08/2014  14:26:55  14.682°W 165.318°E    14.682  -1.457   -7.058  -2.459    24.001   133.378    42.591   260.557  +
03/09/2014  01:51:41  14.682°W 165.318°E    14.682  -1.019   -7.509  -5.237   -40.965   275.334   -31.304    51.329  +
27/05/2015  01:52:08  14.682°W 165.318°E    14.682  -1.318   -0.114   2.816   -20.412   287.954   -20.150    42.653  +
25/06/2015  12:56:50  14.682°W 165.318°E    14.682  -1.555   -1.911  -0.902     9.878   104.547    63.034   250.872  +
24/07/2015  23:52:54  14.682°W 165.318°E    14.682  -1.389   -5.930  -3.349   -12.174   263.059   -33.769    12.309  +
15/05/2016  11:12:30  14.682°W 165.318°E    14.682  -1.431    6.196   0.701   -13.593    73.564    73.249   190.880  +
13/06/2016  22:26:18  14.682°W 165.318°E    14.682  -1.554    2.562  -1.953    19.547   251.323   -30.571   350.151  +%
13/07/2016  09:21:49  14.682°W 165.318°E    14.682  -1.274    0.819  -5.052   -37.660    73.958    62.918   113.379  +
05/04/2017  08:12:51  14.682°W 165.318°E    14.682  -1.079    5.932   3.603   -33.992    27.638    40.731   116.093  +
04/05/2017  20:26:14  14.682°W 165.318°E    14.682  -1.492    6.507  -0.141    54.538   228.989   -26.793   318.113  +%
03/06/2017  07:53:00  14.682°W 165.318°E    14.682  -1.500    6.965  -3.560   -49.645    30.689    47.225    94.802  +
02/07/2017  18:51:49  14.682°W 165.318°E    14.682  -1.112    5.391  -5.502    45.835   191.191    -5.961   303.825  +%

  + = Latitude of sub-solar point within 0.50° of target (= -1.519°)
  % = Moon above horizon/Sun below horizon                   


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