CWS

Geo belt.

May 21, 2013. Wrote some stuff to figure out pointings as a function of obs latitude and delta longitude between observatory and targets. 

For +33 deg latitude the mean dec is -4.74 degrees, and it ranges from -5.383 to 4.177 deg if we could observe around the entire geo belt. But the elevation angle goes to the horizon for a longitude difference of 80 degrees. So we only get to observe 160 degrees of span, centered on the meridian. Neglecting a small error due to definition of angle (centered on Earth or obs) then that means we span a dec range of  -5.383 to -4.771, i.e. a span of 0.61 degrees.How many stars are there, brighter than 10th mag? 

Sat's

From Krasner email to Tom Prince:

Link for geosats

Imager options.

So this suggests that a simple turntable, rotation axis pointed to N pole and dec pointed at -5.1 degrees would be good. Celestron 8 inch telescope has focal length of 2 meters, f/10, 200 mm aperture. 

35mm focal plane then spans 1 degree FOV. A 10 Mpix camera would have a span of about 3Kpix for 1 degree, or around 1 arcsec/pixel. If we took stuttered imaging of 1 sec expose, 2 sec pause,

times 10-20 for a total integration time of 10-20 seconds, with tracking off, at 10th magnitude we'd expect:

3080 Jy at R=0, and 1 Jy in R is (0.23 X 3080 x 1.51E7) = 1E10 for R=0, for 1m^2 of aperture. We lose factor of 1E4 for 10 magnitudes, and 0.2^2 for aperture, so 40K/sec at 10th.

That should be plenty.  

Canon EOS control

Canon EOS D5 Mark II has been modified to remove IR blocking filter. 

It can be operated in remote control mode over a USB cable. Use Canon's EOS Utilities App on MAC. 

There is a pulldown menu, Tool, that has a Timer Shooting option. That allows time lapse imaging.

EOS 5D Mark II operation

• can do piezo sensor cleaning to shake off dust, but the filter removal seems to have broken that
• this compromises automatic acquisition of dust-suppression flats, so will have to do that manually
• Pick RAW rather than RAW S1 or S2 for full frame.
• turned off high-iso noise reduction, since that just bins things
• turned on noise reduction with dark subtraction

• 8 micron pixels, gives plate scale of theta=8E-3/f(mm), or 1.6461e+03 arc sec per mm of focal length

  f	plate scale	FOV (deg)
  50 mm (portrait)	32.9 arcsec/pixel	40 X 26
  135 mm (telephoto)	12.19 arcsec/pixel	14.8 X 10
  200 mm (telephoto)	8.23 arcsec/pixel	10 X 6.6
  500 mm (mirror lens)	3.3 arcsec/pixel	4 X 2.66
  2000 mm (Celestron)	0.66 arcsec/pixel	1 x 0.66

  
  
  

Geo-coords

Refraction correction in arcminutes as a function of altitude,h, (in degrees) from Wikipedia:

R=1.02*cot(h+(10.3/(h+5.11)))

Included this correction in new version of matlab code. Results for Boston:

Dlong     Az           Zenith     Zenith_corr

-90.0000 -89.2034 98.5924 98.6756
-89.0000 -89.9422 97.8693 97.9521
-88.0000 -90.6813 97.1450 97.2236
-87.0000 -91.4207 96.4195 96.4862
-86.0000 -92.1609 95.6929 95.7323
-85.0000 -92.9018 94.9653 94.9579
-84.0000 -93.6438 94.2369 94.1088
-83.0000 -94.3871 93.5077 93.1744
-82.0000 -95.1318 92.7778 92.1835
-81.0000 -95.8783 92.0473 91.3071
-80.0000 -96.6265 91.3163 90.6200
-79.0000 -97.3769 90.5849 90.0092
-78.0000 -98.1296 89.8532 89.3910
-77.0000 -98.8848 89.1214 88.7469
-76.0000 -99.6427 88.3896 88.0800
-75.0000 -100.4036 87.6578 87.3966
-74.0000 -101.1676 86.9261 86.7017
-73.0000 -101.9351 86.1948 85.9989
-72.0000 -102.7061 85.4639 85.2906
-71.0000 -103.4809 84.7335 84.5785
-70.0000 -104.2598 84.0038 83.8638
-69.0000 -105.0430 83.2749 83.1475
-68.0000 -105.8306 82.5470 82.4301
-67.0000 -106.6230 81.8202 81.7123
-66.0000 -107.4203 81.0946 80.9945
-65.0000 -108.2228 80.3704 80.2771
-64.0000 -109.0307 79.6478 79.5605
-63.0000 -109.8443 78.9269 78.8448
-62.0000 -110.6638 78.2078 78.1305
-61.0000 -111.4893 77.4908 77.4177
-60.0000 -112.3213 76.7760 76.7068
-59.0000 -113.1598 76.0637 75.9978
-58.0000 -114.0051 75.3539 75.2912
-57.0000 -114.8576 74.6470 74.5871
-56.0000 -115.7173 73.9430 73.8858
-55.0000 -116.5846 73.2423 73.1875
-54.0000 -117.4597 72.5450 72.4924
-53.0000 -118.3429 71.8513 71.8008
-52.0000 -119.2343 71.1615 71.1129
-51.0000 -120.1342 70.4759 70.4290
-50.0000 -121.0429 69.7946 69.7494
-49.0000 -121.9606 69.1179 69.0742
-48.0000 -122.8876 68.4461 68.4039
-47.0000 -123.8240 67.7794 67.7386
-46.0000 -124.7700 67.1182 67.0786
-45.0000 -125.7260 66.4627 66.4243
-44.0000 -126.6921 65.8132 65.7759
-43.0000 -127.6686 65.1700 65.1338
-42.0000 -128.6556 64.5334 64.4982
-41.0000 -129.6534 63.9038 63.8696
-40.0000 -130.6621 63.2815 63.2482
-39.0000 -131.6820 62.6668 62.6343
-38.0000 -132.7131 62.0600 62.0284
-37.0000 -133.7557 61.4616 61.4308
-36.0000 -134.8100 60.8719 60.8418
-35.0000 -135.8759 60.2913 60.2619
-34.0000 -136.9538 59.7201 59.6914
-33.0000 -138.0437 59.1588 59.1307
-32.0000 -139.1456 58.6078 58.5802
-31.0000 -140.2597 58.0674 58.0404
-30.0000 -141.3859 57.5381 57.5117
-29.0000 -142.5244 57.0203 56.9944
-28.0000 -143.6752 56.5145 56.4890
-27.0000 -144.8381 56.0210 55.9960
-26.0000 -146.0133 55.5403 55.5158
-25.0000 -147.2006 55.0729 55.0487
-24.0000 -148.3999 54.6191 54.5954
-23.0000 -149.6111 54.1795 54.1562
-22.0000 -150.8340 53.7545 53.7315
-21.0000 -152.0686 53.3445 53.3218
-20.0000 -153.3144 52.9499 52.9276
-19.0000 -154.5714 52.5713 52.5493
-18.0000 -155.8392 52.2090 52.1873
-17.0000 -157.1176 51.8635 51.8420
-16.0000 -158.4061 51.5352 51.5139
-15.0000 -159.7044 51.2244 51.2034
-14.0000 -161.0120 50.9317 50.9109
-13.0000 -162.3286 50.6573 50.6367
-12.0000 -163.6537 50.4016 50.3812
-11.0000 -164.9866 50.1650 50.1448
-10.0000 -166.3270 49.9478 49.9278
-9.0000 -167.6742 49.7504 49.7305
-8.0000 -169.0276 49.5729 49.5531
-7.0000 -170.3866 49.4157 49.3960
-6.0000 -171.7506 49.2789 49.2593
-5.0000 -173.1189 49.1629 49.1434
-4.0000 -174.4907 49.0677 49.0482
-3.0000 -175.8655 48.9935 48.9741
-2.0000 -177.2424 48.9404 48.9210
-1.0000 -178.6209 48.9085 48.8892
0 180.0000 48.8979 48.8785
1.0000 178.6209 48.9085 48.8892
2.0000 177.2424 48.9404 48.9210
3.0000 175.8655 48.9935 48.9741
4.0000 174.4907 49.0677 49.0482
5.0000 173.1189 49.1629 49.1434
6.0000 171.7506 49.2789 49.2593
7.0000 170.3866 49.4157 49.3960
8.0000 169.0276 49.5729 49.5531
9.0000 167.6742 49.7504 49.7305
10.0000 166.3270 49.9478 49.9278
11.0000 164.9866 50.1650 50.1448
12.0000 163.6537 50.4016 50.3812
13.0000 162.3286 50.6573 50.6367
14.0000 161.0120 50.9317 50.9109
15.0000 159.7044 51.2244 51.2034
16.0000 158.4061 51.5352 51.5139
17.0000 157.1176 51.8635 51.8420
18.0000 155.8392 52.2090 52.1873
19.0000 154.5714 52.5713 52.5493
20.0000 153.3144 52.9499 52.9276
21.0000 152.0686 53.3445 53.3218
22.0000 150.8340 53.7545 53.7315
23.0000 149.6111 54.1795 54.1562
24.0000 148.3999 54.6191 54.5954
25.0000 147.2006 55.0729 55.0487
26.0000 146.0133 55.5403 55.5158
27.0000 144.8381 56.0210 55.9960
28.0000 143.6752 56.5145 56.4890
29.0000 142.5244 57.0203 56.9944
30.0000 141.3859 57.5381 57.5117
31.0000 140.2597 58.0674 58.0404
32.0000 139.1456 58.6078 58.5802
33.0000 138.0437 59.1588 59.1307
34.0000 136.9538 59.7201 59.6914
35.0000 135.8759 60.2913 60.2619
36.0000 134.8100 60.8719 60.8418
37.0000 133.7557 61.4616 61.4308
38.0000 132.7131 62.0600 62.0284
39.0000 131.6820 62.6668 62.6343
40.0000 130.6621 63.2815 63.2482
41.0000 129.6534 63.9038 63.8696
42.0000 128.6556 64.5334 64.4982
43.0000 127.6686 65.1700 65.1338
44.0000 126.6921 65.8132 65.7759
45.0000 125.7260 66.4627 66.4243
46.0000 124.7700 67.1182 67.0786
47.0000 123.8240 67.7794 67.7386
48.0000 122.8876 68.4461 68.4039
49.0000 121.9606 69.1179 69.0742
50.0000 121.0429 69.7946 69.7494
51.0000 120.1342 70.4759 70.4290
52.0000 119.2343 71.1615 71.1129
53.0000 118.3429 71.8513 71.8008
54.0000 117.4597 72.5450 72.4924
55.0000 116.5846 73.2423 73.1875
56.0000 115.7173 73.9430 73.8858
57.0000 114.8576 74.6470 74.5871
58.0000 114.0051 75.3539 75.2912
59.0000 113.1598 76.0637 75.9978
60.0000 112.3213 76.7760 76.7068
61.0000 111.4893 77.4908 77.4177
62.0000 110.6638 78.2078 78.1305
63.0000 109.8443 78.9269 78.8448
64.0000 109.0307 79.6478 79.5605
65.0000 108.2228 80.3704 80.2771
66.0000 107.4203 81.0946 80.9945
67.0000 106.6230 81.8202 81.7123
68.0000 105.8306 82.5470 82.4301
69.0000 105.0430 83.2749 83.1475
70.0000 104.2598 84.0038 83.8638
71.0000 103.4809 84.7335 84.5785
72.0000 102.7061 85.4639 85.2906
73.0000 101.9351 86.1948 85.9989
74.0000 101.1676 86.9261 86.7017
75.0000 100.4036 87.6578 87.3966
76.0000 99.6427 88.3896 88.0800
77.0000 98.8848 89.1214 88.7469
78.0000 98.1296 89.8532 89.3910
79.0000 97.3769 90.5849 90.0092
80.0000 96.6265 91.3163 90.6200
81.0000 95.8783 92.0473 91.3071
82.0000 95.1318 92.7778 92.1835
83.0000 94.3871 93.5077 93.1744
84.0000 93.6438 94.2369 94.1088
85.0000 92.9018 94.9653 94.9579
86.0000 92.1609 95.6929 95.7323
87.0000 91.4207 96.4195 96.4862
88.0000 90.6813 97.1450 97.2236
89.0000 89.9422 97.8693 97.9521
90.0000 89.2034 98.5924 98.6756

For La Jolla:

Dlong      Az         Zenith    Zen_corr

-90.0000 -86.4392 98.5924 98.6756
-89.0000 -87.2764 97.7701 97.8526
-88.0000 -88.1142 96.9462 97.0225
-87.0000 -88.9527 96.1206 96.1786
-86.0000 -89.7921 95.2934 95.3027
-85.0000 -90.6326 94.4648 94.3812
-84.0000 -91.4743 93.6347 93.3440
-83.0000 -92.3173 92.8032 92.2173
-82.0000 -93.1619 91.9705 91.2272
-81.0000 -94.0081 91.1365 90.4675
-80.0000 -94.8562 90.3013 89.7723
-79.0000 -95.7062 89.4651 89.0525
-78.0000 -96.5585 88.6279 88.2992
-77.0000 -97.4130 87.7897 87.5208
-76.0000 -98.2700 86.9506 86.7252
-75.0000 -99.1296 86.1108 85.9178
-74.0000 -99.9921 85.2703 85.1023
-73.0000 -100.8575 84.4293 84.2809
-72.0000 -101.7260 83.5877 83.4551
-71.0000 -102.5978 82.7457 82.6260
-70.0000 -103.4731 81.9034 81.7945
-69.0000 -104.3520 81.0609 80.9611
-68.0000 -105.2346 80.2183 80.1263
-67.0000 -106.1212 79.3757 79.2905
-66.0000 -107.0120 78.5333 78.4539
-65.0000 -107.9069 77.6912 77.6169
-64.0000 -108.8064 76.8494 76.7798
-63.0000 -109.7104 76.0082 75.9426
-62.0000 -110.6192 75.1677 75.1057
-61.0000 -111.5330 74.3280 74.2693
-60.0000 -112.4518 73.4892 73.4336
-59.0000 -113.3759 72.6516 72.5987
-58.0000 -114.3054 71.8154 71.7649
-57.0000 -115.2404 70.9806 70.9324
-56.0000 -116.1812 70.1475 70.1014
-55.0000 -117.1279 69.3163 69.2722
-54.0000 -118.0806 68.4871 68.4448
-53.0000 -119.0394 67.6602 67.6196
-52.0000 -120.0046 66.8359 66.7968
-51.0000 -120.9763 66.0143 65.9767
-50.0000 -121.9546 65.1957 65.1595
-49.0000 -122.9397 64.3803 64.3454
-48.0000 -123.9316 63.5685 63.5348
-47.0000 -124.9305 62.7605 62.7279
-46.0000 -125.9366 61.9566 61.9251
-45.0000 -126.9499 61.1570 61.1266
-44.0000 -127.9706 60.3623 60.3327
-43.0000 -128.9987 59.5726 59.5439
-42.0000 -130.0345 58.7883 58.7605
-41.0000 -131.0778 58.0098 57.9829
-40.0000 -132.1290 57.2375 57.2114
-39.0000 -133.1879 56.4719 56.4465
-38.0000 -134.2547 55.7132 55.6885
-37.0000 -135.3295 54.9620 54.9380
-36.0000 -136.4122 54.2188 54.1954
-35.0000 -137.5030 53.4840 53.4612
-34.0000 -138.6018 52.7581 52.7360
-33.0000 -139.7087 52.0417 52.0201
-32.0000 -140.8236 51.3353 51.3142
-31.0000 -141.9466 50.6395 50.6189
-30.0000 -143.0776 49.9548 49.9348
-29.0000 -144.2167 49.2820 49.2624
-28.0000 -145.3636 48.6216 48.6025
-27.0000 -146.5185 47.9743 47.9556
-26.0000 -147.6811 47.3408 47.3225
-25.0000 -148.8514 46.7218 46.7039
-24.0000 -150.0293 46.1180 46.1005
-23.0000 -151.2147 45.5302 45.5130
-22.0000 -152.4074 44.9591 44.9423
-21.0000 -153.6072 44.4055 44.3890
-20.0000 -154.8140 43.8703 43.8541
-19.0000 -156.0276 43.3542 43.3382
-18.0000 -157.2477 42.8580 42.8423
-17.0000 -158.4741 42.3826 42.3672
-16.0000 -159.7067 41.9288 41.9136
-15.0000 -160.9451 41.4973 41.4824
-14.0000 -162.1890 41.0891 41.0744
-13.0000 -163.4382 40.7049 40.6904
-12.0000 -164.6924 40.3455 40.3312
-11.0000 -165.9512 40.0117 39.9975
-10.0000 -167.2142 39.7042 39.6902
-9.0000 -168.4813 39.4236 39.4097
-8.0000 -169.7519 39.1707 39.1570
-7.0000 -171.0258 38.9460 38.9324
-6.0000 -172.3024 38.7501 38.7366
-5.0000 -173.5816 38.5835 38.5701
-4.0000 -174.8628 38.4466 38.4332
-3.0000 -176.1456 38.3398 38.3264
-2.0000 -177.4297 38.2632 38.2499
-1.0000 -178.7147 38.2172 38.2039
0 180.0000 38.2019 38.1886
1.0000 178.7147 38.2172 38.2039
2.0000 177.4297 38.2632 38.2499
3.0000 176.1456 38.3398 38.3264
4.0000 174.8628 38.4466 38.4332
5.0000 173.5816 38.5835 38.5701
6.0000 172.3024 38.7501 38.7366
7.0000 171.0258 38.9460 38.9324
8.0000 169.7519 39.1707 39.1570
9.0000 168.4813 39.4236 39.4097
10.0000 167.2142 39.7042 39.6902
11.0000 165.9512 40.0117 39.9975
12.0000 164.6924 40.3455 40.3312
13.0000 163.4382 40.7049 40.6904
14.0000 162.1890 41.0891 41.0744
15.0000 160.9451 41.4973 41.4824
16.0000 159.7067 41.9288 41.9136
17.0000 158.4741 42.3826 42.3672
18.0000 157.2477 42.8580 42.8423
19.0000 156.0276 43.3542 43.3382
20.0000 154.8140 43.8703 43.8541
21.0000 153.6072 44.4055 44.3890
22.0000 152.4074 44.9591 44.9423
23.0000 151.2147 45.5302 45.5130
24.0000 150.0293 46.1180 46.1005
25.0000 148.8514 46.7218 46.7039
26.0000 147.6811 47.3408 47.3225
27.0000 146.5185 47.9743 47.9556
28.0000 145.3636 48.6216 48.6025
29.0000 144.2167 49.2820 49.2624
30.0000 143.0776 49.9548 49.9348
31.0000 141.9466 50.6395 50.6189
32.0000 140.8236 51.3353 51.3142
33.0000 139.7087 52.0417 52.0201
34.0000 138.6018 52.7581 52.7360
35.0000 137.5030 53.4840 53.4612
36.0000 136.4122 54.2188 54.1954
37.0000 135.3295 54.9620 54.9380
38.0000 134.2547 55.7132 55.6885
39.0000 133.1879 56.4719 56.4465
40.0000 132.1290 57.2375 57.2114
41.0000 131.0778 58.0098 57.9829
42.0000 130.0345 58.7883 58.7605
43.0000 128.9987 59.5726 59.5439
44.0000 127.9706 60.3623 60.3327
45.0000 126.9499 61.1570 61.1266
46.0000 125.9366 61.9566 61.9251
47.0000 124.9305 62.7605 62.7279
48.0000 123.9316 63.5685 63.5348
49.0000 122.9397 64.3803 64.3454
50.0000 121.9546 65.1957 65.1595
51.0000 120.9763 66.0143 65.9767
52.0000 120.0046 66.8359 66.7968
53.0000 119.0394 67.6602 67.6196
54.0000 118.0806 68.4871 68.4448
55.0000 117.1279 69.3163 69.2722
56.0000 116.1812 70.1475 70.1014
57.0000 115.2404 70.9806 70.9324
58.0000 114.3054 71.8154 71.7649
59.0000 113.3759 72.6516 72.5987
60.0000 112.4518 73.4892 73.4336
61.0000 111.5330 74.3280 74.2693
62.0000 110.6192 75.1677 75.1057
63.0000 109.7104 76.0082 75.9426
64.0000 108.8064 76.8494 76.7798
65.0000 107.9069 77.6912 77.6169
66.0000 107.0120 78.5333 78.4539
67.0000 106.1212 79.3757 79.2905
68.0000 105.2346 80.2183 80.1263
69.0000 104.3520 81.0609 80.9611
70.0000 103.4731 81.9034 81.7945
71.0000 102.5978 82.7457 82.6260
72.0000 101.7260 83.5877 83.4551
73.0000 100.8575 84.4293 84.2809
74.0000 99.9921 85.2703 85.1023
75.0000 99.1296 86.1108 85.9178
76.0000 98.2700 86.9506 86.7252
77.0000 97.4130 87.7897 87.5208
78.0000 96.5585 88.6279 88.2992
79.0000 95.7062 89.4651 89.0525
80.0000 94.8562 90.3013 89.7723
81.0000 94.0081 91.1365 90.4675
82.0000 93.1619 91.9705 91.2272
83.0000 92.3173 92.8032 92.2173
84.0000 91.4743 93.6347 93.3440
85.0000 90.6326 94.4648 94.3812
86.0000 89.7921 95.2934 95.3027
87.0000 88.9527 96.1206 96.1786
88.0000 88.1142 96.9462 97.0225
89.0000 87.2764 97.7701 97.8526
90.0000 86.4392 98.5924 98.6756

So if we can go to a zenith angle of 70 deg, that corresponds to mag(along)=50 deg which is longitude span of (71-50)=19 W to (71+50)=121 W

Geostationary_satellites (PDF file, sorted by longitude)

So some good targets accessible from Boston that are on Jerry's list are at 

June 9 2013. 

I have collected a few images using 135mm lens and Canon D5 Mark II (modified to have IR blocking filter removed). Pointed towards az = 195 and zenith angle of 50 deg, which should be longitude of 82W in geo belt. A few test images were taken on nights of June 5-6 and June 8-9, 2013. Did crude pointing using iPhone app. Camera on tripod inside house, looking out a S-facing window. On each night managed to catch a glint that appears in more than one frame. Dave Monet ran images through astrometry.net to get boresight pointing, and also obtained lens distortion map as well!

On June 5-6 IMG_4760, 4761, 4762 is has geo-glint in upper left corner (1759, 359). Image should be roughly N up E left if displayed with x increasing L to R and y increasing top to bottom.

Monet's analysis is in stubbs.tar.gz

For image 4760:

Field center: (RA,Dec) = (204.7, -7.935) deg.
Field center: (RA H:M:S, Dec D:M:S) = (13:38:43.632, -07:56:06.119).

Dave's matching to stars shows Vmag vs. instrumental mag scale

Pincushion distortion terms: Quoting Monet's email:

Just a quick update on your Canon lens.  At least in the SLALIB sense
of pincushion distortion, PCD is a decent model.  For your three frames:

4760:
  Poly:  Ncoef=10  PCD=  0.0000  Sx=14.109  Sy=12.945
  PCD:   Ncoef= 3  PCD=  0.1848  Sx=14.612  Sy=13.888

4761:
  Poly:  Ncoef=10  PCD=  0.0000  Sx=20.555  Sy=14.455
  PCD:   Ncoef= 3  PCD=  0.1910  Sx=21.380  Sy=14.597

4762:
  Poly:  Ncoef=10  PCD=  0.0000  Sx=18.314  Sy=15.701
  PCD:   Ncoef= 3  PCD=  0.2176  Sx=20.264  Sy=17.353

I haven't dug deeply into the subtle art of trimming large residuals,
but a simple linear (Affine) transformation and a PCD=0.19 seems to
do just about as well as the cubic polynomial in each coordinate.
The Sx,Sy are the RMS errors to the fit in the tangent plane, and
the units are arcsec.  I have taken the boresight from the solution provided
by astrometry.net.

Cheers.
-Dave

==========  From SLALIB, units of (x,y) are radians in the tangent plane

void slaPcd ( double disco, double *x, double *y )
{
 double f;

 f =  1.0 + disco * ( *x * *x + *y * *y );
 *x *= f;
 *y *= f;
}

So my interpretation of what Dave sent is that the effective focal length has a term that just depends on R^2 off axis, so that f=f(1+0.198*(x^2+x^2)) where x and y are in units of radians.

On June 8-9  caught another geoglint in images 4776 and 4777. Had much better focus on camera for second night. Glint at (4246,1893) actually saturates in 30 sec image. 

June 10. 

Trying to do a bit better. Did careful focusing of camera on infinity. Need to dark some 30 sec darks, and some twilight sky flats would be good as well.

Also will try to do a more careful job of pointing. Dec at 195 azimuth should be -5.24. On the meridian, zenith angle of 0 is (no refraction corruption) dec of 42.36. So a zenith angle of 42.36 is dec of zero, and zenith angle of (42.36+5.24)=47.6 should be geo belt at 195 azimuth. 

Observing log for June 9-10. Scattered high cloud. Sunset is 2030, astro twilight ends 2251 local, until astro twilight ends at 0246. Sunrise is 0507 local. So can probably take useful data between 2100 and 0400 or so, 6 hours. We are 1.3 days from new moon, so it's basically dark time. Moonset is 2112, rises at 0656. 

• Display on control window in M mode shows exposure level needed. Have set lens to f/2, focus should be good. 
• 30 second exposures still seem like a good compromise exposure time. Will stick to that, with ISO=500. 
• Morning was cloudy so this surely crapped out at some point. 
• Did clearly catch a N-to-S moving geo-sat in frames 4875-4888, perhaps beyond. It's near center of image at the start
• Time stamp in image headers is way off. Camera thinks 4875 was taken at 0123. Was actually 2134 local. 

Processing:

Converted Canon CR2 files to TIFF with 

dcraw -T -4 4876.CR2

and then split out the 3 color channels into separate fits files with

convert -separate 4876.tiff 4876.fits

That made three images, namely 4876-0.fits, 4876-1.fits and 4876-2.fits, that seem to be RGB for 012. 

The geosat is at (in the fits image) (x=2326,y=2085)

4877 is a much better image. Object is at (2342, 2019) .

Rotation stage is Newport RVS80PP. 1:180 worm gear so one rev of shaft is 2 degrees of turntable motion. Microstepper drive has 51,200 microsteps per rev. So one smallest microstep is 2/51200=0.1406 arc sec/step.

Microstepping controller manual: manual, PDF file

Rotation stage manual: Newport_stage_manual.pdf

So to drive the rotator at sidereal rate would require about 106 Hz drive frequency, as a TTL square wave.

More precisely, at dec of -6 deg the sky moves at 15cos(dec) arcsec/sec = 14.92 arcsec/sec. So sidereal rate at geo would be 14.92/0.1406 = 106.10 Hz. 

Twice sidereal is 212.2 Hz. FOV is 14.8 degrees. It takes 24 hours/360 deg * 14.8 deg~ 1 hour to move by one FOV. 

DB-15 connector on turntable is male pins. 

1: phase 1+

9: phase 1-

2: phase 2+

10: phase 2-

stepper wants rms of 0.71 A so full amplitude of drive current is 1A, into 1.7 Ohms. 

Microstepper drive unit wants switches 1,2 and 3 all on to get this current limit. 

24 Volt supply should be OK. Stripe is (+) on AC adapter. 

Wired up DC adapter and function generator. Worked best with microstepper controller switch 1 set to increase motor current one notch above the minimum. Seems to do a fine job of driving the turntable. 

Wired up a directional switch with a voltage divider but it didn't seem to work properly- need to fix that. 

Modes:

1. step offset, no tracking. 14 degree field requires only 150/14 ~ 10 images to scan entire geo belt. Get to 30 sec staring depth. Requires coordinated turntable and camera control.

     2. scan from E to W at about the half sidereal rate. With 30 seconds per image we get streaks for both stars and geo-sats. including a few seconds for readout overhead, Takes the entire night to scan the geo belt. Stars move 7 arc sec /sec * 30 sec = 210 arcsec ~ 17 pixels in each image. If we go slightly more slowly than half sidereal then geo-sats have shorter streaks. If we want to get 6 images of each patch of sky, we want about one degree between frames. This is 3600/15 sec = 4 minutes between exposures. Aw what the heck, just take back-to-back sequence of 30 sec images. We would get horizon-to-horizon coverage in one night. 

June 14 2013.

OK, have built up Celestron wedge, plus rotation stage with stepper drive as RA axis, and manual goniometer for declination. Microstepping drive works. Fixed directional switch by choosing an appropriate current limiting resistor for 35V DC supply. Made adapter plates for mounting turntable to wedge, and camera to turntable. 

Now let's think about iPhone accelerometer for pointing information. 

readout is in units of g's. If we place the iphone on the wedge, then the polar axis is at a zenith angle z that obeys

g_z=g*cos(z), so g_z/g=cos(z) and z=arccos(g_z) in units of g. 

Alignment steps:

1. level base of wedge , to attain gz=1, gx=gy=0
2. Point azimuth to have polar axis parallel to N
3. Put iphone on turntable flat disk. Adjust wedge angle to attain gz=cosd(90-latitude)=cosd(elevation).
4. Now put iphone on flat part of Uchannel, so that z axis points along camera boresight. 
5. adjust equatorial drive to get gx=0. 
6. Looking towards the South,  gz=cosd(zenith)=cosd(dec-latitude). So dec=acosd(gz)+latutude. 
7. So with gx=0, adjust dec drive to achieve desired value. For Boston, to point to dec=-5 is a zenith angle of 42.36+5=47.36, or gz=cosd(47.36)=0.6774. 
8. Then put iphone back on turntable disk, to measure HA. This comes from gx and gy, since gz is constant. 
9. gy is max when HA=0. If we're pointing S then if we roll west then gx increases. 

July 5 2013

Tracking mount is operational. Made an optical interlock that can be used to turn tracking off (or on!) when shutter is open. 

Downloaded archived version of Nebulosity program that controls Canon D5 mark II. Note latest version doesn't work, need 3.0.7. 

Requested and received TLE history for Anik F2R, concatenated the TLE data into a single line data file 

column 4 is YYDDD.DDDD 

column 5 is first deriv of mean motion

column 6 is some strange ("decimal assumed") second deriv. of mean motion

column 12 is inclination (degrees)

column 13 is RA of ascending node

column 14 is eccentricity

column 15 is mean anomaly

column 16 is revs/day

column 17 is rev number (use this for timing!) 

Matlab code for mapping az and zenith vs long, geopoint.m

Matlab function to compute az and zenith, geoaltaz.m

Matlab script to compute declinations, geodec.m

SIMBAD dump of geo < 10th, geo_band_stars.dat

trimmed catalog of geo stars, geo_band_stars_cut.dat