Video Formats:

Videos were encoded with variable bitrate at approximately 10 frames per second. 

MPEG videos are encoded using the Microsoft MPEG4v2 codec, and should be compatible with most Microsoft Windows Media Players.

Quicktime videos are encoded using Apple Quicktime MPEG format and should be compatible with most Apple Quicktime Media Players.

Flash videos are encoded using the Adobe Flash Video codec, and displayed via the FlowPlayer web interface which should be compatible with the Adobe Flash plugin available for most modern web browsers. Your mileage may vary.

Background Subtraction:

All of these movies are observed sky with:

  1. Stars brighter than ~6th magnitude individually subtracted
  2. An average residual sidereal sky removed
  3. A modelled zodiacal light contribution removed
  4. A 2 week average residue removed

Intensity Scale:

The intensity scale is ±5 SMEI analog-to-digital units (ADUs), going from black (-5) to white (+5), where a 10th magnitude star brightness spread over one square degree in the sky is an average value of 0.46 ADUs over this area.

Fisheye Coordinates:

The coordinate frame is ecliptic the projection is of an equal-angle fisheye centered upon the Sun out to a square of ± 100°.

This map covers more than a hemisphere of sky.

Fisheye Figure:

Fisheye Image

Angular coordinates with angles [φ ,θ]:

Movies for comets C/2001 Q4 (NEAT), C/2002 T7 (LINEAR) and C/2004 F4 (Bradfield) have been provided in an angular coordinate system (see figure below) which uses comet ephemerides from the Minor Planet and Comet Ephemeris Service to place the comet nucleus at the origin of a standard coordinate frame and orient the coordinate frame's x-axis along the line to the Sun.

Geometric Coordinate Figure

These movies are provided in a resolution of 1000x400 pixels in MPEG and Quicktime format, and 500x200 pixels in Flash format. With the comet at the origin, the movies extend 90° in the antisunward direction of φ and 10° in the sunward direction of φ and also ±20° in the θ direction.

Perspective removed. Linear coordinates [x,z]:

The angular location [φ,θ] of a given point along the comet tail can be converted to [x,z], where x is the 3D linear distance down the comet tail along the Sun-comet line, and z the distance perpendicular to this and to the line from point P to Earth. First, ephemeris values are found for RC, the Sun-comet distance; for RE, the comet-Earth distance; and for elongation ε the Sun-comet angle as viewed from Earth.

Let α be the angle between the x-axis and the comet-Earth line, Then,

  • α = ε + arcsin(REsin(ε/RC))

And for given values of [φ,θ],

  • x = REcos(α) (1 - tan(α)/tan(α + φ))

Finally,

  • z = x tan(θ) (sin(α)/sin(φ))

The movies are provided in a resolution of 800x400 pixels in both MPEG and Quicktime formats, and 400x200 pixels in Flash format. Each pixel is equivalent to a distance of approximately 105km in each dimension, [x,z] for the full sized (800x400) movies.

Linear coordinate [x,z] figure:

NEAT linear coordinates