### HORIZON FILES & PLOTS (12 Oct 2001)

I realized that in the old plots, no account was taken of the fact that the telescope increases its distance above the ground as one tilts it up in elevation. The trees are so close that this makes quite a difference when one calculates the radio horizon. Now the worst place is at azimuth 345 where the radio horizon is 31 degrees (instead of >40 degrees). (Please discard any old plots you may have around.)

And the optical horizon is a little different too, because it was estimated from the sun avoidance monitor with the telescope at a constant 12 degrees elevation.

I still may tweak the curves a little, because we didn't check the markings on the sun monitor. I made them 2.5 years ago, but the center mark could be off-center now if the electrical centering of the picture on the monitor has changed. Harold will check that it is centered as viewed from the place he stood to make the optical measurements. (There's some parallax between the glass where the marks are and the picture tube.)

The files are all stored on Kronen in KDATA:[SMT.DOC] in case you want to use them. They are:

```	HORIZON.DOC		The raw measurements of the optical horizon
along with the distance from the avoidance
camera to the forest boundary.

HORIZON.DAT		The corrected optical horizon plus the
calculated Radio Horizon, the height of the
trees at the forest boundary, the amount
they'd have to be pruned to yield a 20-degree
radio horizon, and the distance into the
forest that would have to be cleared if
instead one removed those trees (assuming
the trees behind are the same height).

HORIZON.TXT		Details about how one makes the measurements
along with the equations used for the
corrections and values adopted for the
height of the telescope, the distance of the
camera from the elevation axis, etc.

HORIZON.GRAPHIC		The Graphic macro that makes the calculations
and plots.

HORIZON_FOREST.PS	The forest boundary plot.

HORIZON_AZEL.PS		The radio and optical horizons in rectangular
az-el coordinates.

HORIZON_POLAR.PS	The same in polar coordinates.

```
The 1999 data are in similar files with a "99" appended to the names.

-Bill