Created: 07/01/99 by EF
Updated: 12/08/08 by EF
The center of the top box (optical axis) is at x=13000, y=9620. The
probe moves in a U-shaped area with corners at 17928, 3913 (1) ; 6568,
3913 (21); 6568, 15766 (49); and 17928, 15766 (69). Moves between 1
and 21 are from W to E, from 21 to 49 are N to S, and from 49 to 69
are E to W. So, motor 1 moves EW and motor 3 moves NS.
The scale per step is 2mm/200step = .01 mm/step and the telescope
scale is about 21.97 "/mm, giving 0.21997 "/step. Matt Holman
measured the following offsets from the center:
ra dec (both in arcsec)
+1090 -1260 seg 1
-1430 -1260 seg 21
-1430 +1360 seg 49
+1090 +1360 seg 69
So the side with segments 1-21 of the U is 1260" off axis in Y (to the
N), while the side with segments 49-69 is 1360" off in Y (to the S).
The side with segments 21-49 is 1430" off in X (to the E).
The scale of the TV along both X and Y is 0.3 "/pix. So the field of
view is 640x0.3 = 192" in X (East-West) and 480x0.3 = 144" in Y
(North-South).
The EW legs are then 2520" long; the NS leg is 2620" long.
So the U shaped area in total is a rectangular area
2520 + 60 + 60 = 2640 arcs in X and 2620+50+50 = 2720 arcs in Y.
The positions of the Keplercam amps are as marked below.
X
^
|__>Y
N
h____________________________________.d
| 21 1 |
| 9,10 |
| g.____________________________|c
| |
| | Amp 2 Amp 1
| |
2 | |
E 7 | 35 | X W
2 | |
0 | |
" | | Amp 4 Amp 3
| |
| f|____________________________.b
| |
| 49 58,59 69 |
e|___________________________________|a
2640"
S
More helpfully, corners a,b,c... have these offsets in arcsec from the center
a b c d e f g h
RA 1150W 1150W 1150W 1150W 1490E 1370E 1370E 1490E
Dec 1410S 1310S 1210N 1310N 1410S 1310S 1210N 1310N
So the idea is to take a target coordinate (ra(t) dec(t)), and search
for a guide star with ra(g), dec(g) within the horseshoe shaped area.
So for instance the successful Guide Star should have
{ 1490 > ra(t) - ra(g) > -1150 AND
[ -1310 > dec(t) - dec(g) > -1410 or 1310 > dec(t) - dec(g) > 1210] }
OR
{ 1490 > ra(t)-ra(g) > 1370 AND 1410 > dec(t) - dec(g) > -1310}
So, one would then find guide stars that fall within those field
limits, convert the offsets in arcsec to mirror position (using the
scale above), then locate which of the segments below would contain
that star.
Segments
motor 1 3 2
# X Y focus offset
00 13000 9620
01 17928, 3913, 1444
02 17360, 3913, 1310
03 16792, 3913, 1192
04 16224, 3913, 1090
05 15656, 3913, 1005
06 15088, 3913, 937
07 14520, 3913, 885
08 13952, 3913, 849
09 13384, 3913, 830
10 12816, 3913, 827
11 12248, 3913, 840
12 11680, 3913, 870
13 11112, 3913, 917
14 10544, 3913, 979
15 9976, 3913, 1058
16 9408, 3913, 1154
17 8840, 3913, 1266
18 8272, 3913, 1395
19 7704, 3913, 1540
20 7136, 3913, 1702
21 6568, 3913, 1880
22 6568, 4352, 1757
23 6568, 4791, 1644
24 6568, 4791, 1644
25 6568, 5230, 1541
26 6568, 5669, 1447
27 6568, 6108, 1364
28 6568, 6547, 1290
29 6568, 6986, 1226
30 6568, 7425, 1172
31 6568, 7864, 1128
32 6568, 8303, 1094
33 6568, 8742, 1069
34 6568, 9181, 1055
35 6568, 9620, 1050
36 6568, 10059, 1055
37 6568, 10498, 1069
38 6568, 10937, 1094
39 6568, 11376, 1128
40 6568, 11815, 1172
41 6568, 12254, 1226
42 6568, 12693, 1290
43 6568, 13132, 1364
44 6568, 13571, 1447
45 6568, 14010, 1541
46 6568, 14449, 1644
47 6568, 14888, 1757
48 6568, 15327, 1880
49 6568, 15766, 2013
50 7136, 15766, 1835
51 7704, 15766, 1673
52 8272, 15766, 1528
53 8840, 15766, 1399
54 9408, 15766, 1287
55 9976, 15766, 1191
56 10544, 15766, 1112
57 11112, 15766, 1049
58 11680, 15766, 1003
59 12248, 15766, 973
60 12816, 15766, 959
61 13384, 15766, 962
62 13952, 15766, 981
63 14520, 15766, 1017
64 15088, 15766, 1069
65 15656, 15766, 1138
66 16224, 15766, 1223
67 16792, 15766, 1324
68 17360, 15766, 1442
69 17928, 15766, 1577