From: Terrence Redding <tredding@mac.com>

Date: September 28, 2009 8:04:48 PM MDT

To: IOTAoccultations@yahoogroups.com

Cc: palmbeachastro@yahoogroups.com, astro_IIDC@yahoogroups.com

Subject: Re: [IOTAoccultations] Video Recording planning and preprations for the LCROSS impact plume


Tom, I am glad you have started this thread.  I too plan to record this event and have the same concerns.


What would be the best filter to use from the east coast of the USA?


How aperture dependent is this event?  


I assume most of us will attempt at 30 FPS.  But would 60 or 120 FPS be better?  I have a firewire camera capable of 120 FPS  recording direct to disk.


What would the optimum setup be for a 3", 4", 5", 6", or larger scope?  What would the minimum scope be for visual observation?


Should one consider a blue filter, red filter, or an infrared cut filter as optimum.  If we don't have an infrared cut filter what other filters should be considered?



Terry - W6LMJ - 14.287 


Terrence R. Redding, Ph.D. 

Redding Observatory South, West Palm Beach, Florida

http://olt.net/learningstyle/Site_2/Learning_Style_Research.html

How do amateur astronomers learn?


American Association of Variable Star

Observers (AAVSO): RTN http://www.aavso.org/




On Sep 28, 2009, at 9:06 PM, Tom Campbell wrote:

I'm starting a new topic just for open discussion of video recording techniques of this lunar impact event.

It appears that a lot of the predicted ejecta sunlight reflected wavelengths from the impact plume will extend from the middle of the visible light spectrum to the longer wavelengths of infrared light. This reflection spectra happens to include the wavelengths that our analog 30 FPS (25FPS for PAL) low light level security cameras are most sensitive to. So I think that a telescope of at least 12.5cm (5 inches) in diameter is capable of recording this manmade event. Of course the impact plume predictions are based on modeling and the real event maybe surprisingly brighter, or it could be dimmer than predicted. But I will not miss the opportunity to video record this rare event for the world. Only bad weather will stop me from observing it.

The subject of using an IR pass filter, or anykind of blue blocking filter has already been brought up for observers in the Eastern USA to use that happen to be in strong morning twilight or when the sun is just beginning to rise. Otherwise the blue sky will greatly reduce the contrast of the impact plume or wash it out completly.

Correct me if I am wrong but I believe video of the impact will be better with our cameras mounted at our telescopes prime focus without any focal reducers. The plume is not a point source object and we want to get a lot of pixels on it which is just the opposite of what we do for asteroid target stars where a field reducer is used to concentrate a point of light on fewer pixels for greater S/N ratio.

In the case of the LCROSS impact plume it will be sunlit and if using an FR lens it will brighten up the surrounding moonscape as well as the plume. We only want to video record a small portion of the moon surrounding the impact crater, high magnification will get most of the sunlit moon outside of the video field of view in order to get better contrast of the impact crater rim and its deep shadow.

The impact plume is predicted to "wash out" the impact crater's deep shadow for several tens of seconds. The contrast of the crater shadow will appear to change momentarily if the plume itself cannot be seen. The latter will not be rising above the limb of the moon.

My prime source of the LCROSS information is from the NASA website in order to give credit where credit is due.

T-11 days before impact; let's share ideas on observing whether it be visual or video recorded.

Tom