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Tail Size in Miles on Jan 25-26, 2003

Here are some useful calculations about pixels width and height in Miles, Meters, etc.

 |                              h\   
PX              R             Earth 

Here, we have:
d = R * tan(h)

d is the distance in length units, such as Sun-Pluto, or miles.
R is the distance between PX and Earth, same units as d.
h is the angel in degrees at Earth side.

Since each frame is 1024*1024 pixels, and the field of view is 23.6*23.6 Arcminutes, each pixel represents 3.8411458333333e-4 Degrees.

Assuming that PX is at 3 SunPluto,


R = 3 SunPluto
h = 3.8411458333333e-4 Degrees
AU = 1.496e11 Meters
SunPluto = 39.91136 AU = 5.970739456e12 Meters = 3.71004549431e+9 Miles
EarthMoonDistance = 3.844e8 Meters

Pixel Size:

d = R * tan(h)
  = 3 * tan(3.8411458333333e-4)
  = 2.0112192552579e-5 SunPluto
  = 8.0270495735532e-4 AU
  = 1.2008466162035e+8 Meters
  = 120084.66162035    KM
  = 74617.149360458097 Miles
  = 0.312395 EarthMoonDistance

Moons tail size in pixels:

From existing ZetaTalk:

You can consider the Moons to be within 5 million miles of Planet X, as the maximum distance they will stray. 
Maximum Moons tail size at 3 SunPluto = 5e6 / 74617 = 67 Pixels

Note: This is a 2 D distance, not a 3 D distance. We are looking at a projection of 3 Dimensional objects into a 2 D surface. If 2 objects are behind each other, and one is slightly to the side, then you cannot really tell how far apart are they by looking at a 2 D image.