Multi-Station Reduction Technique

IOTA ANNUAL MEETING November 20th – 22nd, 2009

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(234) Barbara occultation of Nov 21, 2009Orlando, Florida

20090909 (449) Hamburga(attempted) 20 station deployment

S. Degenhardt

20090909 (449) HamburgaPre-deployment setup

20081211 (134) Hertha Post-Deployment…. MESS!

20081211 (134) Hertha Post-Deployment…. MESS!

20090719 (790) Pretoria log sheet for tracking site location data.It is essential to keep good records in order to organize the output data.

Video is transferred to computer via firewire, thus it is already in a DV AVI near lossless format

When the firewire is connected to an active ZR camcorder this window pops up.For data traceability I have adopted a filename format of:

YYYYMMDD (asteroid #) Asteroid name Station ID

This DV control panel allows me to chose which part of the tape to upload to computer

My generic AVISythn script. I simply remove the # symbol from in front of the line I want to use.

I can perform running averages and other processing “on the fly” with this.

What do you get when you cover an objective lens with a ¼” of dew while staring at a part of the sky where the full moon is only 12 degrees away….?

An occultation reduction nightmare!!!

20080618 (19) Fortuna raw video from D. Dunham’s 4th station

Using VirtualDub and ImageJ I was able to take every 100th frame and using a median filter I created one dark frame.

Using an AVISynth script I took the dark frame and subtracted it from the entire movie revealing the target star (circled).

The resulting lightcurve from this simple AVIsynth script process showing the positive event.

AVISynth scripts speeds up the time from downloading video to resulting lightcurve

Time keeping method for multi-station deployments

Using AVISynth you can access the embedded frame counter and internal clock of the miniDV recorder. First, I record an initial KIWI time stamp on all my Canon ZR recorders before my deployment.

Upon retrieving each station after the occultation I record an ending time stamp

Using this spread sheet I enter the initial and ending KIWI time stamps and their associated internal clock reading. Column R is the calculated PPM error for that Canon ZR during the time period of the occultation.

I then copy that PPM error and paste it in the Q13 window which applies that PPM correction to Rows 6-10. I can then enter the Internal Clock value for any frame in Columns J-M and Columns F-I give me the PPM error corrected UT time for that frame.

This is a table of random frame clock times of a 1 hour recording to test this method. The standard deviation of any derived time = 0.013 seconds.

The plot of this data shows that the encoded Internal Clock has an error of up to 1 NTSC video field. This would likely be because the encoded time is applied to an entire frame and not the field where a time transition from 0.999 to 1.000 of each second occurs.

What you hope your results will look like!

For more information on AVIsynth ideas, Steve Preston’s tutorial:http://www.netstevepr.com/Avisynth-LiMovie.htm

Scotty’s multi-station efforts and techniques:http://scottysmightymini.com/