Occultation Light Curves for Teachers/Students/Others

Posted on by

RECON Example JCDO vs Yerington Objectives:

1. Construct an Excel graph of an asteroid occultation using video data and video software.

2. List and explain the steps involved in making observation –> collecting data –> processing data –> displaying data for interpretation

Key Vocab: Occultation, Light Intensity/Flux

Procedure

1. Visit & Download: Virtual Dub

2. Visit & Download: LiMovie

3. Obtain & save video data of an occultation event (raw-data)

  • i.e. “occultation practice.avi”
  •  this avi file is usually compressed. LiMovie needs an uncompressed avi file, so you need now to uncompress it with VirtualDub – it’ll be much bigger

4 Run Virtual Dub

  • Goal is to make an .avi file which LiMovie can read.
  • File –> “Open Video File” –> select the proper data file
  • File –> “Save as AVI” –> virtual dub will now process the video
  • When finished, save the new file with a “marker” that indicates this is the file to use for LiMovie, i.e. “occultation practice-vd.avi”

5. Run LiMovie

  •  Limit is about 2041-frames or 68 seconds per analysis running at 29.97 frames/sec
  • File –> “AVI File Open” –>select “occultation practice-vd.avi”
  •  Click on your target star and adjust the red circle (radius in number of pixels / radius box) until it encloses all of your star and as little sky as possible
  •  adjust the blue annulus to be beyond the red circle and not include any other stars or bad pixels. Make sure your star can’t slop over into this “doughnut.”
  •  make sure Kiwi is checked (middle right edge of the screen) if you have Kiwi OSD, then LiMovie will read the time stamps
  • Star Tracking –> “drift” mode
  • Use “Star Image [3D]” for proper radius aperture and background radius selections. Can use “noise reduction” mode for assistance
  • “Measurement Panel”  –> Start
  • Light Curve Data will appear on the right-side. Note the frames being processed on the left under “Current Frame.” (29.97 Frames/sec)
  • When complete, “Save to “CSV-File” (Excel-Lite), i.e. “practice occultation”
  • Open CSV-File, Select entire column “k”. Make graph, the output will be Light Flux (Y-axis) vs Frame Number (X-Axis). Save as an Excel file with filename yyyymmdd_curve
  • Optional…You might want to format the x-axis to make each major unit 29.97. Each mark is about 1-second of time duration.

Video Longer than 68-seconds

  • Use video software to separate file into 2-smaller files under 68-seconds each. Note the exact frame when you separate
  • Perform the above steps for each video file.
  • Combine the two CSV files into one, i.e. copy-paste

OTHER LINKS

Courtesy of www.occultations.net