[daip] AIPS: HOWTO: Gridding- Spheroidal functions

[Eric Greisen]

VMV writes:
 > Dear Mr/Mrs!
 > 
 > VMV> AIPS documentation and the most of the books on CLEAN mention the so
 > VMV> called spheroidal functions used by gridding algorithm. I was unable
 > VMV> to find the exact mathematical definition of that functions (which are
 > VMV> used specially for gridding). Can you please shed a light on what
 > VMV> functions are exactly used?
 > 
 > LK> Dorogoy Vasiya,
 > 
 > LK> You can find the exact mathematical definition of the spheroidal function
 > LK> at the AIPS COOK BOOK volume 2 in the section G.GLOSSARY, page G-17.
 > LK>                       ^^^^^^^^
 > 
 > LK> Leonid Kogan
 > 
 > Thanks, but it still remains unclear how to calculate this
 > eigenfunction. Are there any polinomial representations of this
 > function or something?
 > 

The aips subroutines which compute this function are

$AIPS_ROOT/31DEC0?/Q/SUB/NOTST/CONVFN.FOR
$AIPS_ROOT/31DEC0?/APL/SUB/NOTST/SPHFN.FOR

There were several studies conducted by Fred Schwab and myself in the
late 1970's that reviewed this and many other functions for use in
convolutional gridding.  They appeared as NRAO Memos and Mr. Schwab
may have published something in a journal around that time.

Eric Greisen