In the spring of 2009, the LCROSS Team issued a single frequency estimate at 550nm of the impact ejecta curtain brightness of approximately 3.0 mpsas during the first between 10 and 60 seconds after impact.  Heldman (2009). A version of Heldman (2009) is reproduced as a low-resolution frame on the LCROSS Team Observation Campaign webpage (2009). url: http://lcross.arc.nasa.gov/impact.htm . For amateur CCD or video imaging purposes, this understates the likely mpsas, since CCD cameras respond to the broad integrated wavelengths between approximately 380nm and 1000nm.  CCDs do not respond at a single wavelength.   The LCROSS-EDUS impact will generate a dust ejecta curtain about 10 km x 5 km high between 40 to 60 seconds after impact according to the NASA-LCROSS Team conservative best estimate impact model (CBEIM). Bart(2008) at slides 19-20;  Wooden (2008) at slide 2. This current conservative LCROSS CBEIM translates to a 3 arcsec x 2.5 arcsec ejecta dust cloud at a mean lunar distance of 384,400km. A larger hypothetical 20 x 20 km ejecta curtain converted to a circular shape of equal 400 sq km area has a diameter of about 12 km.  As seen from Earth at a mean lunar distance of 384,400 km,  the 20 x 20 km square billboard would be 11 x 11 square arcsecs, or equivalent to a circle with a diameter of 12 arcsecs. At those ejecta curtain sizes and an irradiance at a single wavelength of 550nm of 3.0 mpsas, the corresponding integrated magnitudes of the curtain would be 1 integrated magnitudes for the 10km x 5km scenario and -1.9 integrated magnitudes for a 20km x 20km, 12 arcsec diameter scenario.  This apparent brightness (3.0 mpsas) provides a favorable contrast index against typical Earthshine (dark limb) irradiance between 12 to 17 mpsas for the dark limb (mean value 15.44 mpsas) but not against Moonshine (bright limb) at 4 to 6 mpsas. The LCROSS ejecta curtain will present a uniquely difficult extended object for amateurs to image.   The impact is hoped to occur when a permanently shadowed region (PSR) is on or near the bright limb terminator with the crater surrounding the PSR being partially lit at a very low sun angle.  The dust ejecta curtain will rise into the sunlight and reflect light back to Earth-based telescopes against the background darkness of the night sky immediately adjacent to the dark limb. At the moment of projected impact, 2009-10-09 11:30UT, the Moon will have the following geocentric empheris characteristics:  Phase angle 65.2984  Perscent illumination 71% illumination Terminator colongitude 158 Lunar age 20.7 days The average sky brightness under moonlight scattered illlumination (expressed in mpsas) at various distances from the Moon was modelled with precision by Krisciunas and Schaefer (1991) based on earlier measurements by Krisciunas (1990) and an earlier rough model by Walker (1987). See Krisciunas (1990) at Figure 8, reproducing the rough model of Walker (1987). The effect of moonlight is additive. Under the rough Walker model, the full Moon adds about -1.9 mpsas to whatever your base sky brightness is.  At a lunar age of 20 days, about -1 mpsas is added.  If you are observing from a light-polluted 3 integrated magnitude urban sky (equivalent to about 16.9 mpsas), the light from a 20 day old Moon adds on average about -1 mpsas to your sky brightness.  That is it would reduce a 16.9 mpsas sky to a 15.9 mpsas sky - equivalent to about 2.1 integrated magnitude sky. Conversely, if you travel to your favorite 21 mpsas - 6.1 integrated magnitude rural dark sky site, the same Moon reduces sky brightness to 20 mpsas or 5.5 integrated magnitudes. The effect of moonlight is dependent on the lunar phase and the degrees of distance between the Moon and the observed target.  Krisciunas and Schaefer (1991) (at Table 2) give the following rough delta mpsas (as measured through a Johnson V standard filter) for the lunar phase angle and distance between the Moon and the observed target.  These results are for their improved model over the Walker (1987) rough model: Phase angle Angular distance Moon-target             05    30    60 30          -4.5  -2.9  -2.2     60          -3.7  -2.1  -1.5 90          -2.7  -1.4  -0.9 120         -1.6  -0.6  -0.3 The value in Krisciunas and Schaefer's table closest to LCROSS impact circumstances is a phase angle of 60 and an angular distance of 5 degrees.  They report a delta mpsas of -3.7 for those circumstances. (Lunar phase angle is the number of degrees between the Sun, the Moon and the observer. It varies between 0 and 180 degrees.  It is the S-T-O angle reported by the NASA/JPL Horizon's Ephemeris system.  Phase angles less than 90 degrees imply backscattering of light; phase angles greater than 90 degrees imply forward scattered light.) For an urban 16.9 mpsas (3.0 integrated magnitude) sky, 60 degree phase angle moon light would increase sky brightness near the Moon by -3.7 mpsas to about 13.2 mpsas - or -0.5 integrated magnitudes.  At the rural dark sky site with an excellent 21 mpsas - a 6.1 integrated limiting magnitude - moonlight was reduce the limiting magnitude to 17.3 mpsas or a 3.3 integrated limiting magnitude. Equating (roughly and perhaps inapproriately) the LCROSS team's single 550nm wavelength mpas of 3.0 to the LCROSS ejecta curtain to the full Johnson V-band mpsas, indicates that the LCROSS ejecta curtaion might have a positive contrast index even in an urban light polluted environment: Sky brightness 5 degs from Moon  Curtain MPSAS  Contrast Index Urban 13.2        3.0            4.1 Rural 17.3        3.0            5.7 Even though the LCROSS ejecta curtain will be seen rising against a bright background sky, at an average curtain brightness of 3.0 mpsas, it still may be visible or subject to imaging. An obvious implication of the above is that travelling a dark sky site may improve the contrast between the ejecta curtain. Dark skies - even though they are washed out by moonlight - still relatively increase an amateur's likelihood of visually detecting the impact curtain and of imaging the curtain. An extended object fainter than 3.0 mpsas - such as Saturn - has been widely imaged as it was occulted by the Moon.  Saturn has a computed mpsas of 6.7 based on an diameter of 14 to 20 arcsecs and an integrated magnitude ranging between 0.4 to 1.2 mags. But unlike Saturn, the LCROSS ejecta curtain will be a low-density dispered dust cloud.  In an abbreviated literature search, no articles were found concerning the additive effect of moonlight between 0 degrees and 5 degrees from the lunar limb. Lunar amateurs and lunar occultation amatuers are familiar with this effect of moonlight.  Only the brightest stars can be seen next to the bright limb of the full Moon.  Magnitude 4 to 7 stars disappear within an arcminute of the bright lunar limb. Amateurs in the LCROSS Google observation group ( url: http://groups.google.com/group/lcross_observation ) have been attempting to gain some understanding of the brightness of the night sky above and within a quarter-degree of the lunar limb by observing grazes and imaging stars during lunar occulations of clusters.  Example images are: Chris Kitting. Moon occulting  Pleaides  2009-08-14 9;46UT http://01227941410742638900-a-g.googlegroups.com/web/CKitting_20090814_0946P... http://tinyurl.com/oopegs Image details: http://groups.google.com/group/lcross_observation/msg/80c0f58084faec69 In Kitting's image, magnitude 7 to 8 stars in Merope's Tail are co-exposed close to an overexposed lunar terminator. Derek C. Breit April 25, 2007 6.6 mag star graze on dark limb http://www.poyntsource.com/tmp/April_25th_2007_Graze.mpg (24 mb mpg) These experiments have had limited success, principally because the few number of such occultation events and uncooperative weather limits the ability to gather useful data using those techniques. An alternative technique would be CCD photometry analysis. In this technique, the south pole of the Moon is imaged at high focal ratios (f/30 plus) at various exposure times from underexposure to high over-exposure.  The camera and scope are then retargeted without changing focal length or exposure on an open cluster at a similar altitude as the Moon. The V magnitudes of open clusters are well-known and plots of clusters limited by a specific magnitude are easily made using the Webda's online database.  url: http://www.univie.ac.at/webda/  The open cluster provides reference stars to determine simple transform coefficients for the CCD camera at a given exposure setting through standard B and V or C and V filters.  Modern imaging processing packages like AIP4WIN include photometry utilities by which the differential magnitude of stars can be found and correlated to CCD well ADUs.   See single star photometry in Exercise C.5 in the AIP4WIN handbook and the extractive photometry utility on the AIP4WIN menu (Measure | Photometry| Extractive Photometry).  The open cluster image also provides an image scale that can be applied to your image of the south pole. This poster unsuccessfully attempted a preliminary test during the August 14, 2009 lunar occultation of Pleaides.  An image of the south pole was taken, followed by an image of the Alcyone triple.  Unfortunately, weather conditions and an unanticipated glare problem unquie to the Mak imaging scope prevented getting a useable result.  The Meade ETX 125 Mak has a curved corrector plate.  When slewing from the south pole to Alcyone, the Mak's curved surface diverted off-axis lunar glare into the tube and washed out the image. No useable photometry information could be gleaned from the image, but a demonstration information on image scale could be found. A panel summarizing this technique demonstration test can be seen at: http://members.csolutions.net/fisherka/astronote/observed/LCROSS/2009_8_14_0... http://tinyurl.com/n4l8sn The next best - and last - analogous lunar south pole illumination to the LCROSS impact will occur on September 9 11:30UT: Lunar libration data for images and impact Source: LTVT ephemeris data, topocentric W111.8 N41.8 Date-TimeUT     libr_lat lib_long colong illumfrac 20090907 1130   -6.2     -5.5     128    92        20090908 1130   -6.2     -5.5     140.2  85.5 20090909 1130   -6.1     -5.4     152.3  77.3 20091009 1130   -3.5     2.8      158.2  70.9 Impact day 20090910 1130   -5.4     -5.1     164.4  67.7 20090911 1130   -4.4     -4.3     176.5  57.1 20090912 1130   -3.2     -3.3     188.7  45.8 Date-TimeUT     Lunar age (days) 20090907 1130   18.1 20090908 1130   19.1 20090909 1130   20.1 20091009 1130   20.6 Impact day 20090910 1130   21.1 20090911 1130   22.1 20090912 1130   23.1 On the early morning of Sept. 8, there are no appropriate open clusters near the Moon.  NGC752 (Caldwell 28) is higher in the sky. The Double Cluster is also at a higher altitude, but visible. On the early morning of Sept. 9, the Moon and M45 will both be visible, but the Pleaides will be a higher altitude.  On the morning of Sept. 10, the Moon will be near the Pleaides and at the same altitude.  On the evening of the 11th,  a number of open clusters might be used for baseline photometry - M45, M36, M37, M38 or NGC1647.  As we approach full Moon on September 4, the Moon will be 68% illuminated on August 29 (from the opposite direction).  The night of August 29 provides an opportunity to set up and test equipment under test analogous illumination before September 9.  On the evening of August 29, the Moon will be low in the southern sky just below the apex of the Sag "teapot".  Open clusters M21, M23 and M25 are also visible, but at higher altitudes. Amateur photometry to determine sky brightness within one quarter degree "above" the lunar south pole on September 8 through 11 (particularly on September 9) will help determine if the LCROSS impact ejecta cloud will have sufficient contrast against the moonlight night sky to be seen and imaged.  Imaging through filter combinations (V-C, V-I, B-V) will give the most accurate results.  To confirm whether the background sky brightness will not overwhelm the ejecta curtain brightness, better photometry data might be collected by amateurs within zero to 5 arcminutes "above" the south lunar pole.  Clear Skies - Kurt Disclaimer: This is an amateur note. Criticisms and corrections to the above are welcomed. Fisher, Kurt A. (amateur).  2008.  Conversion Calculator for NELM(V) to MPSAS (B) systems. (Web calculator).  url:   http://members.csolutions.net/fisherka/astronote/plan/tlmnelm/html/NELM2BCal... (last accessed 26 Aug. 2009) Heldman, J. (LCROSS Team).  Email Feb. 11, 2009, Slide 4 (slide4.gif). Krisciunas, K. 1990. Further measurements of extinction and sky brightness on the island of Hawaii. PASP 102:1052-1063. Bib. Code 1990PASP..102.1052K url: http://adsabs.harvard.edu/abs/1990PASP..102.1052K (last accessed 26 Aug. 2009) Krisciunas, K. and Schaefer, B.E. 1991. A model of the brightness of moonlight. PASP 103:1033-1039, Bib. Code. 1991PASP..103.1033K url: http://adsabs.harvard.edu/abs/1991PASP..103.1033K (last accessed 26 Aug. 2009) LCROSS Team. 2009. Average and Edge Brightness of Ejecta Curtain (Figure).  LCROSS Observation Campaign website.  url: http://lcross.arc.nasa.gov/impact.htm and http://lcross.arc.nasa.gov/observation.htm Image: observation05.jpg (last accessed 26 Aug. 2009) Walker, A. 1987. ________________. NOMO Newsletter. 10:16.