1) N: size of cube data array, N by N by N. If '0' then the user must read the actual data to determine (usually '0' means the user did not specify this and simply used a default header.)
2) Desc: string, a handy run name/identifier for identifying this set.
3) Author: string, name of person who made this/did this run.
4) Program: string, 'cpixon/tpixon/rtwl/idl/other', handy to know what program created this.
5) Date: string, date this was run was created.
6) Axes: string, define individual axes: 'y,z,x', 'y,-x,z', 'cpixon', 'tpixon', 'rtwl', 'cartesian', 'unknown', etc
7) SunCenter: int(3), the sun center in image coordinates (i,j,k), note that this could validly be outside the defined data cube if the sun is not actually in the cube.
8) NorthPole: int(3), defines the direction of the chosen orientation axis as a vector going from 'SunCenter' to here. The default is simply the 'k' axis, i.e. for a SunCenter of 0,0,0 and an axis pointing north along 'k', the pole is 0,0,1.
9) Orient: string, 'solar/ecliptic/other', indicating what the defined rotational axis (SunCenter to AxisNorth) represents. Put another way, states whether the NorthPole of the axis represents the solar rotational, earth orbital, or other pole.
10) Voxelcm: double, the length of each voxel edge in units of centimeters, not Solar Radii (because SR in arc sec is not a constant unit)
11) VOffset: int, a flag specifying whether an X,Y,Z position is relative to the voxel center, or voxel corner. As X,Y,Z positions are relative to the SunCenter position, this item can be considered the specific placement of that center in the density cube. (L=Lower,U=Upper,l=left,r=right,F=front,B=back) 0 = sun center is at center of its given voxel; 1 = LlF, i.e. sun center is at lower left front edge of its voxel 2=LlB, 3=LrF, 4=LrB, 5=UlF, 6=UlB, 7=UrF, 8=UrB
12) EUnits: string, units of electron density (usually electrons/cm3).
Plus, the Image: The data cube, int(N,N,N) or float(N,N,N) or double(N,N,N)
; example of IDL structure using above information:
;cubeinfo.N=
;cubeinfo.desc=
;cubeinfo.author=
;cubeinfo.program='Pixon','WLRaytrace','IDL','Other'
;cubeinfo.date=now()
;cubeinfo.axes='x,y,z'
;cubeinfo.suncenter=[N/2,N/2,N/2]
;cubeinfo.northpole=[N/2,N/2,N/2 + 1]
;cubeinfo.orient='solar','ecliptic','other'
;cubeinfo.voxelcm=1e10
;cubeinfo.voffset=0
;cubeinfo.eunit=1e8