What the problem was

• The problem was that scanning (2006) was not as regular as it was hoped to be:
  • RadioT4ScanningHorAz horizontal scanning in azimuthal "AZ-ZD" coordinates
  • RadioT4ScanningVertEq vertical scanning in equatorial "REC-DEC" (r.a. and dec) coordinates
  • RadioT4ScanningHorEq horizontal scanning in equatorial "REC-DEC" (r.a. and dec) coordinates

Newer version as of revision 1.20.2.17 in cvs

• DONE: Improved algorithm (2008)
  • RadioT4ScanningCvs080619 hor/ver azimuthal and equatorial scanning algorithms revision 1.20.2.17 in cvs

horiozontal/vertrical alt-azimuthal and equatorial scanning algorithms in cvs as of 2008-06-20

• stan ("vertical" scans) is now a wrapper for scan ("horizontal" scans) - no need to duplicate nearly identical code;
• Both scan (horizontal) and stan (vertical) should give more or less straight/rectilinear scans in their coordinate systems for both zen-azimuth (poh) and equatorial (poe) coordinates;
• However, the cost is that for equatorial scans there is a playoff between having straightness/rectilinearity and speed: decreasing SCAN_LINE_TOLERANCE_DEG in rt_main.h decreases pseudo-lissajousness for equatorial scans but slows down scanning speed;
  • possible TODO: if this parameter is seen as useful, probably it should be made into an optional telescope user parameter
• scripts/scan.sh can be used for non-interactive testing to generate files such as the ones below.
• possible TODO: In SetCoor, replace rST ("real Sidereal Time") with an estimate of the future sidereal time at which the telescope is expected to arrive at the coordinates which are being transformed between alt-azimuth ("Hor" or "H") and equatorial coordinates.
  • Complications: this would require SetCoor to do much more than just transform coordinates, it would require it to have some sort of model (e.g. linear) of the near future telescope motion, which depends not only on what sort of command is presently active, but also on the new "set" coordinates themselves. Would such an algorithm be worth the effort?

• The two zen-azimuth scans at dec=85 deg use this cvs revision 1.20.2.17 of 2008-06-20 which deals with absolute azimuth or longitude offsets > 180 deg
• The equatorial scans here are shown using the Lambert equal area projection - for this reason, scans starting at "equatorial offset" poe -1 -1 become successively narrower and more intestine-like as they near the celestial north pole, especially for the vertical scans.

scan times

• AZ means an azimuth-zenith scan
• EQ means an ra-dec scan
• hor0 and hor1 mean the two scanning directions
• decXX means declination XX degrees
• cvs of 19 June 08 has #define SCAN_LINE_TOLERANCE_DEG 0.05

date.coordinatetype.hor/vert.declinationdeg	full scan time in sidereal minutes
log.0806200103.EQ.hor1.dec85	7.11091
log.0806200103.EQ.hor1.dec80	10.0885
log.0806200103.EQ.hor1.dec70	13.9249
log.0806200103.EQ.hor1.dec60	17.0493
log.0806200103.EQ.hor1.dec50	19.2686
log.0806200103.EQ.hor1.dec40	19.6668
log.0806200103.EQ.hor1.dec30	16.9989
log.0806200103.EQ.hor1.dec20	13.2268
log.0806200103.EQ.hor0.dec85	23.7562
log.0806200103.EQ.hor0.dec80	22.3769
log.0806200103.EQ.hor0.dec70	20.5995
log.0806200103.EQ.hor0.dec60	18.9601
log.0806200103.EQ.hor0.dec50	18.1453
log.0806200103.EQ.hor0.dec40	19.0002
log.0806200103.EQ.hor0.dec30	22.1508
log.0806200103.EQ.hor0.dec20	24.7422
log.0806200103.AZ.hor1.dec85cvs080620	16.5324
log.0806200103.AZ.hor1.dec80	12.28
log.0806200103.AZ.hor1.dec70	12.4701
log.0806200103.AZ.hor1.dec60	12.5156
log.0806200103.AZ.hor1.dec50	12.3407
log.0806200103.AZ.hor1.dec40	12.0603
log.0806200103.AZ.hor1.dec30	11.5785
log.0806200103.AZ.hor1.dec20	11.4861
log.0806200103.AZ.hor0.dec85cvs080620	39.4008
log.0806200103.AZ.hor0.dec80	24.3418
log.0806200103.AZ.hor0.dec70	24.1814
log.0806200103.AZ.hor0.dec60	24.1221
log.0806200103.AZ.hor0.dec50	24.1236
log.0806200103.AZ.hor0.dec40	24.0635
log.0806200103.AZ.hor0.dec30	24.0066
log.0806200103.AZ.hor0.dec20	23.9982

scan plots

• AZ means an azimuth-zenith scan - scales are to +- 1 degree
• EQ means an ra-dec scan - dec is +- 1 degree; r.a. is to +- 1 "r.a. degree" by default, or in great circle degrees where the plot has this in the title

• scan.0806200103.AZ.hor0.dec20.png:
  
• scan.0806200103.AZ.hor0.dec30.png:
  
• scan.0806200103.AZ.hor0.dec40.png:
  
• scan.0806200103.AZ.hor0.dec50.png:
  
• scan.0806200103.AZ.hor0.dec60.png:
  
• scan.0806200103.AZ.hor0.dec70.png:
  
• scan.0806200103.AZ.hor0.dec80.png:
  
• scan.08062015xx.AZ.hor0.dec85.png:
  
• scan.0806200103.AZ.hor1.dec20.png:
  
• scan.0806200103.AZ.hor1.dec30.png:
  
• scan.0806200103.AZ.hor1.dec40.png:
  
• scan.0806200103.AZ.hor1.dec50.png:
  
• scan.0806200103.AZ.hor1.dec60.png:
  
• scan.0806200103.AZ.hor1.dec70.png:
  
• scan.0806200103.AZ.hor1.dec80.png:
  
• scan.08062015xx.AZ.hor1.dec85.png:
  
• scan.0806200103.EQ.hor0.dec20.L.png:
  
• scan.0806200103.EQ.hor0.dec30.L.png:
  
• scan.0806200103.EQ.hor0.dec40.L.png:
  
• scan.0806200103.EQ.hor0.dec50.L.png:
  
• scan.0806200103.EQ.hor0.dec60.L.png:
  
• scan.0806200103.EQ.hor0.dec70.L.png:
  
• scan.0806200103.EQ.hor0.dec80.L.png:
  
• scan.0806200103.EQ.hor0.dec85.L.png:
  
• scan.0806200103.EQ.hor1.dec20.L.png:
  
• scan.0806200103.EQ.hor1.dec30.L.png:
  
• scan.0806200103.EQ.hor1.dec40.L.png:
  
• scan.0806200103.EQ.hor1.dec50.L.png:
  
• scan.0806200103.EQ.hor1.dec60.L.png:
  
• scan.0806200103.EQ.hor1.dec70.L.png:
  
• scan.0806200103.EQ.hor1.dec80.L.png:
  
• scan.0806200103.EQ.hor1.dec85.L.png: