September 2009 - Utah-Astronomy - mailman.xmission.com

Re: [Utah-astronomy] LCROSS Guide to observing and imaging
by Canopus56 16 Sep '09

16 Sep '09

Tyler, Since you are a far more accomplished imager than I am, all I can provide you is my best reasoning as to what would be the better selection. Use the Lumenera Infinity 2-1 monochrome camera. I have not used one, but it is the gold-standard among advanced amateur imagers who make publish the best lunar images on the web. If a high effective focal length is used as I suggest, you will have wasted space on the large chip size provided by the Lumenera 2-1, but you can simply crop the image during processing or use its region-of-interest feature as you purpose. As background materials related to me answering the why of your question, please see See Sinnott's Effective Focal Length to Pixel Size nomogram, url - http://media.skyandtelescope.com/images/Linked.gif - and the more detailed discussion in another message in the LCROSS Observation newsgroup regarding the difference between the lucky imaging strategy used by lunar and planetary imagers and the larger seeing disk based strategy employeed in traditional DSO imagers - Post by K. Fisher 9-8-2009 LCROSS Observation Group Efls for imaging the LCROSS impact http://groups.google.com/group/lcross_observation/msg/764ceeede969207a http://tinyurl.com/owkdf7 Additionally, please review slides 28, 46 and 50 of my revised slide presentation. Slides 28 and 50 show a line profile histogram bisecting the shadowed and light portions of Cabeus A1 and Cabeus A taken 9-10-2009. Slide 50 concerns TFOV and lunar glare. You may need to redownload the presentation that grabbed this morning. For lurkers, the Freid parameter is mentioned below. The Freid parameter numerically estimates the maximum diameter aperature that can be supported given good seeing conditions at a given wavelenght. The poorer the seeing, the larger the arcsec size of the seeing disk, and the lower maximum aperature that can be effectively used. The imaging strategies should focus on the profile line histogram across the shadowed floor of Cabeus A1. The imaging objective is to record the smallest pixel value changes in that line profile that your gear and circumstances permit. It is qualitatively true that smaller aperatures have relatively better Freid parameter than larger aperatures, but here we purpose to use small sized pixel elements, extra long focal lengths, and fast camera frame rates to beat both a 1 or 2 arcsec seeing limit and the Freid parameter. Therefore, in this "lucky lunar" imaging strategy, smaller aperatures (130mm) lose their inherent Freid parameter advantage over larger aperatures above 254mm. "Beating the seeing" by using lucky imaging, you access the greater resolution and smaller arcsec Airy disks (0.6 arcsecs at 254mm at 254mm of aperature vs 1.1 arcsecs for 130mm of aperature) that Dawes limit describes for larger, as opposed to smaller aperatures. The larger size of the Airy disk inherent to smaller aperatures also works against you in the instant context. The target is a linear object 5.6 arcsecs long by 1.7 arcsecs high. If you use a smaller aperature with an Airy disk size of 1.1 arcsecs, odds are that the brighter value pixels related to the adjacent sunlit surface area outside of the crater rim of Cabeus A1 will be blended in and averaged with the pixel values in the shadowed portion of the crater. This will reduce the lowest pixel value that you will be able to extract out of the shadowed portion of Cabeus A1. By using a larger aperature and lucky imaging, you should be able to grab 0.6 arcsec Airy disks and the pixels of the surrounding surface area will be cleanly separated from the pixels of the dark shadowed area. With respect to the large chip size of the Lumerina 2-1, in the instant case you want to use effective focal length to match pixel element size to telescope resolution. Do not use an effective focal length to match chip size to an asthetic image scale to better "frame" the target. The reason for this is lunar glare, as illustrated in Slide 58 of the slide presentation. Lunar glare is directly proportional to the fraction of the lunar disk captured on your telescope's TFOV. Lunar glare pervasively floods the entire TFOV. Flocking, aperature masking or a Lyott mask is not going to make it go away. The only remedy is to use a high efl to reduce the fraction of the sunlit portion of the Moon's disk that goes through your optical system. The effect of a relatively higher lunar glare is to raise the minimum pixel value that you can record from the shadowed portion of Cabeus A1. Finally, the extra aperature gives you some extra insurance against the ejecta plume being fainter than the pre-impact prediction model that has been issued by the LCROSS Team. If it looks like the plume is not reaching its expected brightness over the 30 second post-impact time frame, you can up the gain on your camera and utilize the superior light gathering power of the 254mm mirror as compared to a 130mm lens. All of this being said, the test imaging that I have done was using a Meade ETX at 125mm of aperature. My 254mm GEM mounted Newt would have been the better technical tool to use, but most of the test imaging times were during the work week and in the early morning hours. It was simply easier to setup the Meade ETX and make some images under those work day constraints than to setup and use the 254mm GEM-mounted scope. On the impact day, I intend to set up two scopes - an imaging 254mm GEM - and use the Meade ETX 125mm for visual observing under conditions of good seeing. I found the Meade ETX 125mm with a 4mm TMB eyepiece more than adequate for seeing into the shadowed portion of Cabeus A1 with good resolution. If I have a particular rough work week and don't have the personal energy to cart the 10" Newt around, I will happily arrive and setup only the Meade ETX 125mm. However, other club members should understand that I'm a pretty big guy and this will give me a comparative ex-football player advantage over Patrick when it comes to elbowing other club members away from the Grimm's eyepiece. -:) I hope that outlines the applicable considerations and helps you make your final imaging gear choice. A final disclaimer - my opinions on the optimal imaging strategy differ from those published by the LCROSS Team on their Citizen Science About page. You should compare my minority opinion to their recommendations. http://apps.nasa.gov/lcross/about/ Clear Skies - Kurt Author: Tyler Allred Date: 2009-09-16 10:40 -600 To: 'Utah Astronomy' Subject: Re: [Utah-astronomy] LCROSS Guide to observing and imaging Kurt, Thanks. This pdf was excellent and very informative. I am thinking about setting up my AP130 with a 5X Barlow to record the event. I also have a Lumenera Infinity 2-1 monochrome camera that is capable of very high frame rates. The camera has a 1.4 megapixel (1392 X 1040) sensor with 4.65um pixels. I think this camera may be excellent for recording the event. It is possible to select a smaller portion of the sensor for recording to the computer, if using the full sensor does not add any meaningful data. I could set up my own equipment, but perhaps the Lumenera would better utilized by attaching it to a scope that is larger than my AP. I know that the AP is capable of incredible resolution, but still the camera may be better used on a really large aperture scope. What are your thoughts on the matter? Do you have any ideas for how best to take advantage of this exquisite little camera? Is there a really good scope that is in need of an equally great camera? Let me know. Thanks, Tyler Allred PS - I know that sometimes smaller aperture scopes are less susceptable to atmospheric conditions than larger scopes, because of the scale of the turbulent structures in the atmosphere. Is it possible that the little AP is the best choice? Maybe??? I am interested in your opinion.

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Waning Crescent Moon & Venus
by Rodger C. Fry 16 Sep '09

16 Sep '09

Did anyone catch the beautiful waning crescent moon juxtaposed to Venus this morning. It was awe inspiring. I was in the middle of a shift working at a drill rig in the Book Cliffs when I looked up and saw them. I had to stop what I was doing and take a picture. It would have been worth getting up for. Thank You, Rodger C. Fry Consulting Geologist

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LCROSS Guide to observing and imaging
by Canopus56 16 Sep '09

16 Sep '09

As promised at the last night's (Sept 15) SLAS club meeting, here is my slide presentation regarding amateur observing of the LCROSS impact. It includes finders, visual observing recommendations and imaging recommendations. MS Powerpoint version (8 meg) http://members.csolutions.net/fisherka/astronote/observed/LCROSS/20090915LC… http://tinyurl.com/pbb7pw Slide presentation as PDF file (11 meg) http://members.csolutions.net/fisherka/astronote/observed/LCROSS/20090916LC… http://tinyurl.com/pfujnv in directory: http://members.csolutions.net/fisherka/astronote/observed/LCROSS/ It was heartening to see everyone in a roomful of 50-60 people raise their hand when the club was polled to see who will show up at the club's observatory to view the impact. Through Oct. 9, club members may feel free to call me with questions at my club roster telephone number. I would prefer to receive questions via email at canopus56(a)yahoo.com . Clear Skies - Kurt

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Color video camera
by Stephen Peterson 16 Sep '09

16 Sep '09

Enjoy and appreciate Kurt's posts RE LCROSS! I have a Sony SSC-S20 CCD color video camera I'd be more than happy to loan the group for the LCROSS impact so that a group could watch the event. It runs on 12V, has 380000 pixels (6.5x4.8mm), & has a 'C' lens mount. I have an adapter that would get it to 'T' mount. Don't know who is heading up the observations or if the camera is out dated or inappropriate for the application. Steve

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Re: [Utah-astronomy] LCROSS Guide to observing and imaging
by Canopus56 16 Sep '09

16 Sep '09

Here is a link to an LCROSS slide presentation made by a member of a New Mexico astronomy club to his club: Dave Dockery LCROSS slide presentation (3Meg) http://tinyurl.com/nf7xek - Kurt

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LCROSS Plume visibility analysis and imaging exposure recommendations
by Canopus56 15 Sep '09

15 Sep '09

In follow-up to my post yesterday, I have a correction and a few after thoughts: I have been reminded that the Kwiki video time stamp vendor has ceased operations. http://www.pfdsystems.com/sundown.htm . There is a comparable replacement product, but it is expensive. http://www.horita.com/gpsvideo.htm Pooling resources in group observation is preferred. This recommendation relates to leverage the unique ability to the known time of the impact. NASA TV will be broadcasting images from the shepherding satellite and is offered as a channel on some commercial satellite signal vendors. NASA TV can be accessed via a portable TV dish setup. This will allow observers to time when start that video imaging capture and minimize the amount of wasted disk space. This compares to SMART-1 and Deep Impact, where many minutes of video capture needed to be done, because the moment of impact could not be determined precisely. This consideration weighs in favor of group observing and pooling resources to support a common dish setup. Another timing option seen on Deep Impact is to have one local club member monitor NASA TV on a cable channel. Just before the impact, cells phones can be used to alert remote site observers to start their imagers. Because of the recommended high magnification, box mounted DOB observers may wish to consider buddying up with a tracking mount scope owner. Smaller 5 inch Alt Az mount owners may wish to consider switching to equatorial mount mode. With my Meade ETX 125, even with tracking, alt az tracking at very high magnification was okay, but bothersome. Switching the Meade ETX over to equatorial polar alignment mode, allowed for much smoothier and reliable tracking. With this improved tracking, observing at 300x through a 4mm TMB planetary eyepiece was much more relaxed and enjoyable. Clear Skies - Kurt

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LCROSS Plume visibility analysis and imaging exposure recommendations
by Canopus56 15 Sep '09

15 Sep '09

P.S. to Patrick - I have posted the first message to this list twice. Please use some of your god-like moderator powers and kill the first copy. Thanks - Kurt To the group as a whole - in anticipation of follow-up questions on filters and stopping down your aperature, I have pre-posted my general response to that question. - Clear Skies - Kurt -------------------------------------------------- S - To observe visually, no filters will be needed. Use at least 5 inches of aperature, 10 inches or more is perferred. Use the highest feasible lunar planetary imaging power that your scope will handle - 300x is what I am using based on test observing and imaging for the last month. At such high magnifications, lunar glare will not present a problem. There will be no glare and so accessory actions like stopping down your aperature or using filters to reduce the brightness of the image are not warranted. David Knisley's useful magnifications list is generally used by amateurs for magnification guidance. Knisley's recommended maximum magnification for "specific lunar and planetary detail" visual observing is: Low Mag Per Inch of Aperature: 30.0 High Mag Per Inch of Aperature: 41.9 Low Exit Pupil mm: 0.7 High Exit Pupil mm: 0.6 Useful Mag Description: Very high Used For: Specific planetary lunar detail For a 10" aperature scope, the maximum recommended magnification range is 300 to 410 power. Such filters or other glare reduction procedures may reduce you chances of seeing the plume by reducing the peak plume brightness that your scope can capture. There is a recommendation on the LCROSS Citizen Science "About" page to use a polarizing filter. I have no comment or feelings about that recommendation. http://apps.nasa.gov/lcross/about/ The above is, of course, IMHO. Clear Skies - Kurt P.S. - The LCROSS Team Citizen Science About page recommendation reads: "However, observations are not trivial as the dust cloud may have a brightly lit Moon surface behind it, depending on the exact impact site selected, making it more difficult to see the dust cloud due to the poor contrast; bright dust against a bright Moon surface. The dust will polarize the scattered light but using polarimetery can help with the observation."

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LCROSS Plume visibility analysis and imaging exposure recommendations
by Canopus56 15 Sep '09

15 Sep '09

LCROSS Plume visibility analysis and imaging exposure recommendations The following is an amateur note. Comments and criticisms on the same are welcomed. At url - http://members.csolutions.net/fisherka/astronote/observed/LCROSS/20090915LC… http://tinyurl.com/mqylqf - I have posted another in a series of ongoing discussions between myself and an another active member of the LCROSS Observation Group regarding the expected visibilty of the impact plume. My response is overlength and goes into some technical matters that may not be of interest to general group readers. Therefore, I have posted by link to a separate text file. My amateur analysis of the plume ends with my conclusions regarding whether the plume can be observed visually and imaged. The extended discussion also concludes with a description of what the plume will look like for amateurs using scopes of 5 inches or larger and with recommended strategies for imaging the plume. The support and reasoning for my conclusions are contained in the linked extended discussion file. Those conclusions and recommendations may be of interest to general readers and I replicate that "conclusions" portion of the extended response below. Clear skies - Kurt ----------------------------- - Conclusions On Sept. 11, Rick Baldridge noted that: "NASA will provide professional and amateur observing groups more detail regarding plume size and visibility in the coming weeks. The plume will not extend above the lunar limb, and will not be situated against a dark background such as a shadowed region between craters. However, that does not mean the plume will not be visible. Video and photographic observations must now focus on bringing out the brightening caused by the eject plume in front of a lit lunar surface." September 11, 2009 LCROSS Science Team Announced Target Crater Posted by rickbaldridge on September 11th, 2009. NASA LCROSS Citizen Science Page Blog http://apps.nasa.gov/lcross/ Implications from the foregoing discussion [in the linked extended discussion file] for imaging the LCROSS impact are as follows. If the ejecta plume follows its predicted apparent brightness _and_ if the mpsas of the shadowed portion of crater Cabeus A1 is at least one magnitude lower than 4 mpsas, the impact can be easily imaged and observed using 5 inches of aperture or more. Earth based amateur observers will see essentially a surface contrast effect. As the brightest part of the 10km plume expands within and above the bowl of 17km Cabeus A1 and reaches a brightness of about 4.0 mpsas, the plume will obscure the shadowed portion of Cabeus A1 from Earth observers. The plane of the rim and/or just above the rim will take on a surface brightness equal the surface brightness of the surrounding surface terrain. That surface typically will have an mpsas between 4.0 and 6.0. Normally, Caebus A1 has a bowl shaped appearance caused by crater shadowing when viewed from Earth visually at 300x and/or when imaged, as illustrated in this high resolution amateur image taken in September by Stefan Lammel: http://tinyurl.com/qjex6e (I visually observed the same view a few hours after Stefan took his image using a Meade ETX 125 with a TMB 4mm planetary eyepiece at 300x. The level of detail that I was to observe visually easily exceed what Stefan was able to capture photographically. Stefan when posting his image accompanied the comment that the Moon was at a low altitude and that it was not his best work.) During the first 30 secs, the brightest part of the ejecta plume will create a contrast effect as the surface brightness of the brightest part of the ejecta plume removes the contrast between the crater shadow and surrounding terrain. For visual observers, the crater may see a blurry mesa effect. Caebus A1 will look like a terresterial mesa or will have a slight "raised muffin" appearance. Where the brightest part of the ejecta cloud crosses the sunlit portion of the lunar surface, it will not be visible due to lack of contrast between the cloud and the lunar surface. For low resolution imagers like myself, the crater will simply "disappear" due to this contrast effect beginning near the 30 second mark for a duration of about 30 seconds and then mysteriously reappear on AVI frames. See my 9-10-2009 image for an example of low-resolution image: http://tinyurl.com/qw32fy Although no images have been gathered that match the libration and illuminated fraction of the impact, the reduction in libration in latitude to -6.0 to -3.0 between now and the impact on October 9 will only increase this contrast effect. The Cabeus A1 crater shadow will be relatively thinner (in arscsecs) on the day of impact as compared to that shown in Stefan's image. Imaging of the LCROSS impact will be a fairly straight forward process for amateurs. High focal length imaging is preferred in order to minimize the percent of the sunlit lunar disk captured in a frame. High focal lengths dictate that large pixel DSLR cameras and CCD cameras are disfavored relative to small pixel sized fast moderate and high-end lunar imaging cameras. See Sinnott's Effective Focal Length to Pixel Size nomogram, url - http://media.skyandtelescope.com/images/Linked.gif - and the more detailed discussion in another message in the LCROSS Observation newsgroup - Post by K. Fisher 9-8-2009 LCROSS Observation Group Efls for imaging the LCROSS impact http://groups.google.com/group/lcross_observation/msg/764ceeede969207a http://tinyurl.com/owkdf7 Pre-impact image calibration is an easy three-step process. The goal of this process is to set the pixel value of the brightest edge of the rim of Cabeus A1 to 75% of your camera's well capacity in ADUs. This should assure that the full range of pixel values that can be captured on a line profile across the major axis of crater Cabeus A1 are recorded on images stored to your disk. First, focus your imaging gear on the target crater without concern for the exposure setting. Second, slew to 2.6 stellar magnitude theta Auriga. On the morning of the impact, the Moon will be between the horn stars of Taurus and just next to 1.7 mag bet Taurus (Alnath). 2.6 magnitude theta Auriga is one of the figure stars of Auriga and is about 11 degrees away. Nearby alternative stars for exposure calibration around 2.5 stellar magnitudes include: zeta Per 2.8mags B0.5V, delta Orion 2.2 mags O9.5II, gamma Gem 1.9 mags AOIV, beta Auriga 1.9 mags A2IV. Take some test images of theta Tau and adjust your exposure setting so theta Tau's brightness peaks at 50% of your well capacity. Note that the preview histogram in some image capture software _does not accurately_ represent what is stored in captured images on a disk. Open the test images stored on the disk and run a profile measurement or histogram on your image of theta Aur using your image processing software so you are sure your exposure setting captures the right amount of well ADUs. Keep this exposure setting and slew back onto the impact target Cabeus A1. Take some test frames and look at some of the raw images on your disk. Use the profile measuring line tool (e.g. one is available in AIP4WIN) and take a profile of the pixels that cross the major axis of Cabeus A1. Now adjust your exposure setting so that high pixel value of Cabeus A1 rim is at 75% of your well capacity. The minimum pixel value shown for the Cabeus A1 crater line profile should also be within the range of a histogram made of the entire test image. You can slightly adjust back from this exposure setting so the Moon is not overexposed _on images stored on your disk._ Again, _do not trust the preview image and histogram_ in your image capture software. Post-image processing will favor software packages that offer region masking like Photoshop. This way individual regions of the bright lunar surface can be supressed in brightness, but pixels that encompass the area within the Caebus A1 crater rim can be selectively stacked and gamma stretched. The impact will provide imagers interested in hobby science with an opportunity to study plume kinematics using photometry measurements from their images. The LCROSS ejecta plume will rise 5 kilometers (5000 meters) to its maximum brightness in about 30 seconds. The vertical plume speed is estimated at an average of 167 meters per second (5000/30). For the first 2 kilometers, the ejecta cloud will be masked from Earth view by Cabeus A1's crater rim. This trip above the crater rim will occur between about 18 seconds after impact through impact + 30 seconds. (30 seconds * 3000 meters / 5000 meters). For the final three kilometers, the plume will be sunlight and the total light from the cloud may have a changing photometric signature related to its vertical travel that will be recorded by amateur video imagers. Such recordings might be examined to extract a plot of the total brightness of the Earth visible ejecta curtain against time. The process for making such a recording and reducing it is generally described as follows. An LPI camera of video that records AVI files including both an audio track and a video track will be needed. For the time signal audio track, the video can be time stamped using a digital metronome as the timed audio source. An inexpensive $30 Ibanez model emits a good sharp tone at a maximum of 180 beats per minute with a different second identifier signal and is available at many local music and guitar stores. url: http://www.ibanez.com/electronics/product.aspx?m=MU40 . Alternatively, imagers can use a more expensive video time stamping rig favored by lunar occulation observers - the KIWI OSDI video-GPS timestamper. url: http://www.pfdsystems.com/ . The NIST WWW shortwave time broadcast is another option for a timing audio signal, but since there is no need to coordinate observations between observers and clear reception of the NIST shortwave signal is usually problematic, the Ibanez metronome may be the better inexpensive no-hassle option. Post imaging, the AVI file is reviewed using movie making software. The individual frames that contain identifable time beats and good images of Caebus A1 are separated. Then each time-stamp identified image is reviewed in image processing software. Most image processing software (such as AIP4WIN) contain a region measuring tool. These tools count the average value of pixels in an identified circular or rectangular area. Use the region measuring tool on each time-stamped image and surround all of Cabeus A1. It will be important to use the same relative pixel coordinates from the center of Cabeus A1 in each individual frame. Note the time stamp and the average pixel value for the uniform measuring region on each frame. Then plot the pixel values against time. Finally, compare your plot against the predicted increases in plume brightness that presumably will be provided by the LCROSS Team. In conclusion, the LCROSS impact can be easily imaged, assuming it reaches the brightness of 4.0 mpsas stated in LCROSS pre-impact modeling. The view may not be as dramatic as one might imagine, but it appears certainly worth trying for. The success of amateur imaging is dependent on the LCROSS Team gathering and publishing for amateur use, the apparent brightness of the surface area around Caebus A1 and the shadowed portion of Cabeus A1 in both mpsas and V stellar magnitudes. If the shadowed floor of Cabeus A1 is brighter than 4.0 mpsas, the impact cannot be observed or imaged by amateurs. By the NASA LCROSS Team calling for amateur imaging and by inducing, through press releases stating that the impact is observable, the public's attendence at private star parties, the LCROSS Team has undertaken the business ethical obligation to gather and publish such photometry data prior to September 27 and before Oct. 9. This ethical obligation is also incured by their dual role as scientists and public governmental employees. September 27 represents the last date in which the south lunar pole will be at 71% illuminated fraction and on which amateurs can make useful "dry runs" of their imaging gear. Advanced amateurs with photometric gear may wish to gather and share their hobbyist studies of the apparent brightness of the shadows of small craters on the opposite east side of the southern polar Moon on September 27. Again, this is an amateur note. Comments and criticisms on the same are welcomed. Clear Skies - Kurt

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LCROSS Plume visibility analysis and imaging exposure recommendations
by Canopus56 15 Sep '09

15 Sep '09

On 9-15-2009, Raf wrote: > hoping in your prediction Raf - here it is. - Kurt ----------------------------------- The following is an amateur note. Comments and criticisms on the same are welcomed. At url - http://members.csolutions.net/fisherka/astronote/observed/LCROSS/20090915LC… http://tinyurl.com/mqylqf - I have posted another in a series of ongoing discussions between myself and Jim Mosher regarding the expected visibilty of the impact plume. My response to Jim is overlength and goes into some technical matters that may not be of interest to general group readers. Therefore, I have posted by link to a separate text file. My amateur analysis of the plume ends with my conclusions regarding whether the plume can be observed visually and imaged. The extended discussion also concludes with a description of what the plume will look like for amateurs using scopes of 5 inches or larger and with recommended strategies for imaging the plume. The support and reasoning for my conclusions are contained in the linked extended discussion file. Those conclusions and recommendations may be of interest to general readers and I replicate that "conclusions" portion of the extended response below. Clear skies - Kurt ----------------------------- - Conclusions On Sept. 11, Rick Baldridge noted that: "NASA will provide professional and amateur observing groups more detail regarding plume size and visibility in the coming weeks. The plume will not extend above the lunar limb, and will not be situated against a dark background such as a shadowed region between craters. However, that does not mean the plume will not be visible. Video and photographic observations must now focus on bringing out the brightening caused by the eject plume in front of a lit lunar surface." September 11, 2009 LCROSS Science Team Announced Target Crater Posted by rickbaldridge on September 11th, 2009. NASA LCROSS Citizen Science Page Blog http://apps.nasa.gov/lcross/ Implications from the foregoing discussion [in the linked extended discussion file] for imaging the LCROSS impact are as follows. If the ejecta plume follows its predicted apparent brightness _and_ if the mpsas of the shadowed portion of crater Cabeus A1 is at least one magnitude lower than 4 mpsas, the impact can be easily imaged and observed using 5 inches of aperture or more. Earth based amateur observers will see essentially a surface contrast effect. As the brightest part of the 10km plume expands within and above the bowl of 17km Cabeus A1 and reaches a brightness of about 4.0 mpsas, the plume will obscure the shadowed portion of Cabeus A1 from Earth observers. The plane of the rim and/or just above the rim will take on a surface brightness equal the surface brightness of the surrounding surface terrain. That surface typically will have an mpsas between 4.0 and 6.0. Normally, Caebus A1 has a bowl shaped appearance caused by crater shadowing when viewed from Earth visually at 300x and/or when imaged, as illustrated in this high resolution amateur image taken in September by Stefan Lammel: http://tinyurl.com/qjex6e (I visually observed the same view a few hours after Stefan took his image using a Meade ETX 125 with a TMB 4mm planetary eyepiece at 300x. The level of detail that I was to observe visually easily exceed what Stefan was able to capture photographically. Stefan when posting his image accompanied the comment that the Moon was at a low altitude and that it was not his best work.) During the first 30 secs, the brightest part of the ejecta plume will create a contrast effect as the surface brightness of the brightest part of the ejecta plume removes the contrast between the crater shadow and surrounding terrain. For visual observers, the crater may see a blurry mesa effect. Caebus A1 will look like a terresterial mesa or will have a slight "raised muffin" appearance. Where the brightest part of the ejecta cloud crosses the sunlit portion of the lunar surface, it will not be visible due to lack of contrast between the cloud and the lunar surface. For low resolution imagers like myself, the crater will simply "disappear" due to this contrast effect beginning near the 30 second mark for a duration of about 30 seconds and then mysteriously reappear on AVI frames. See my 9-10-2009 image for an example of low-resolution image: http://tinyurl.com/qw32fy Although no images have been gathered that match the libration and illuminated fraction of the impact, the reduction in libration in latitude to -6.0 to -3.0 between now and the impact on October 9 will only increase this contrast effect. The Cabeus A1 crater shadow will be relatively thinner (in arscsecs) on the day of impact as compared to that shown in Stefan's image. Imaging of the LCROSS impact will be a fairly straight forward process for amateurs. High focal length imaging is preferred in order to minimize the percent of the sunlit lunar disk captured in a frame. High focal lengths dictate that large pixel DSLR cameras and CCD cameras are disfavored relative to small pixel sized fast moderate and high-end lunar imaging cameras. See Sinnott's Effective Focal Length to Pixel Size nomogram, url - http://media.skyandtelescope.com/images/Linked.gif - and the more detailed discussion in another message in the LCROSS Observation newsgroup - Post by K. Fisher 9-8-2009 LCROSS Observation Group Efls for imaging the LCROSS impact http://groups.google.com/group/lcross_observation/msg/764ceeede969207a http://tinyurl.com/owkdf7 Pre-impact image calibration is an easy three-step process. The goal of this process is to set the pixel value of the brightest edge of the rim of Cabeus A1 to 75% of your camera's well capacity in ADUs. This should assure that the full range of pixel values that can be captured on a line profile across the major axis of crater Cabeus A1 are recorded on images stored to your disk. First, focus your imaging gear on the target crater without concern for the exposure setting. Second, slew to 2.6 stellar magnitude theta Auriga. On the morning of the impact, the Moon will be between the horn stars of Taurus and just next to 1.7 mag bet Taurus (Alnath). 2.6 magnitude theta Auriga is one of the figure stars of Auriga and is about 11 degrees away. Nearby alternative stars for exposure calibration around 2.5 stellar magnitudes include: zeta Per 2.8mags B0.5V, delta Orion 2.2 mags O9.5II, gamma Gem 1.9 mags AOIV, beta Auriga 1.9 mags A2IV. Take some test images of theta Tau and adjust your exposure setting so theta Tau's brightness peaks at 50% of your well capacity. Note that the preview histogram in some image capture software _does not accurately_ represent what is stored in captured images on a disk. Open the test images stored on the disk and run a profile measurement or histogram on your image of theta Aur using your image processing software so you are sure your exposure setting captures the right amount of well ADUs. Keep this exposure setting and slew back onto the impact target Cabeus A1. Take some test frames and look at some of the raw images on your disk. Use the profile measuring line tool (e.g. one is available in AIP4WIN) and take a profile of the pixels that cross the major axis of Cabeus A1. Now adjust your exposure setting so that high pixel value of Cabeus A1 rim is at 75% of your well capacity. The minimum pixel value shown for the Cabeus A1 crater line profile should also be within the range of a histogram made of the entire test image. You can slightly adjust back from this exposure setting so the Moon is not overexposed _on images stored on your disk._ Again, _do not trust the preview image and histogram_ in your image capture software. Post-image processing will favor software packages that offer region masking like Photoshop. This way individual regions of the bright lunar surface can be supressed in brightness, but pixels that encompass the area within the Caebus A1 crater rim can be selectively stacked and gamma stretched. The impact will provide imagers interested in hobby science with an opportunity to study plume kinematics using photometry measurements from their images. The LCROSS ejecta plume will rise 5 kilometers (5000 meters) to its maximum brightness in about 30 seconds. The vertical plume speed is estimated at an average of 167 meters per second (5000/30). For the first 2 kilometers, the ejecta cloud will be masked from Earth view by Cabeus A1's crater rim. This trip above the crater rim will occur between about 18 seconds after impact through impact + 30 seconds. (30 seconds * 3000 meters / 5000 meters). For the final three kilometers, the plume will be sunlight and the total light from the cloud may have a changing photometric signature related to its vertical travel that will be recorded by amateur video imagers. Such recordings might be examined to extract a plot of the total brightness of the Earth visible ejecta curtain against time. The process for making such a recording and reducing it is generally described as follows. An LPI camera of video that records AVI files including both an audio track and a video track will be needed. For the time signal audio track, the video can be time stamped using a digital metronome as the timed audio source. An inexpensive $30 Ibanez model emits a good sharp tone at a maximum of 180 beats per minute with a different second identifier signal and is available at many local music and guitar stores. url: http://www.ibanez.com/electronics/product.aspx?m=MU40 . Alternatively, imagers can use a more expensive video time stamping rig favored by lunar occulation observers - the KIWI OSDI video-GPS timestamper. url: http://www.pfdsystems.com/ . The NIST WWW shortwave time broadcast is another option for a timing audio signal, but since there is no need to coordinate observations between observers and clear reception of the NIST shortwave signal is usually problematic, the Ibanez metronome may be the better inexpensive no-hassle option. Post imaging, the AVI file is reviewed using movie making software. The individual frames that contain identifable time beats and good images of Caebus A1 are separated. Then each time-stamp identified image is reviewed in image processing software. Most image processing software (such as AIP4WIN) contain a region measuring tool. These tools count the average value of pixels in an identified circular or rectangular area. Use the region measuring tool on each time-stamped image and surround all of Cabeus A1. It will be important to use the same relative pixel coordinates from the center of Cabeus A1 in each individual frame. Note the time stamp and the average pixel value for the uniform measuring region on each frame. Then plot the pixel values against time. Finally, compare your plot against the predicted increases in plume brightness that presumably will be provided by the LCROSS Team. In conclusion, the LCROSS impact can be easily imaged, assuming it reaches the brightness of 4.0 mpsas stated in LCROSS pre-impact modeling. The view may not be as dramatic as one might imagine, but it appears certainly worth trying for. The success of amateur imaging is dependent on the LCROSS Team gathering and publishing for amateur use, the apparent brightness of the surface area around Caebus A1 and the shadowed portion of Cabeus A1 in both mpsas and V stellar magnitudes. If the shadowed floor of Cabeus A1 is brighter than 4.0 mpsas, the impact cannot be observed or imaged by amateurs. By the NASA LCROSS Team calling for amateur imaging and by inducing, through press releases stating that the impact is observable, the public's attendence at private star parties, the LCROSS Team has undertaken the business ethical obligation to gather and publish such photometry data prior to September 27 and before Oct. 9. This ethical obligation is also incured by their dual role as scientists and public governmental employees. September 27 represents the last date in which the south lunar pole will be at 71% illuminated fraction and on which amateurs can make useful "dry runs" of their imaging gear. Advanced amateurs with photometric gear may wish to gather and share their hobbyist studies of the apparent brightness of the shadows of small craters on the opposite east side of the southern polar Moon on September 27. Again, this is an amateur note. Comments and criticisms on the same are welcomed. Clear Skies - Kurt

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Hard to believe it's an amateur shot
by Patrick Wiggins 14 Sep '09

14 Sep '09

http://www.buytelescopes.com/viewphoto.aspx?pid=20143&sg=1 Wow! patrick

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