Observations 16 MAY 2012
---------------------------------------
Cosatrak 1 (Computerised satellite Tracking System).
FLI ML8300M CCD camera with mechanical shutter + Trimble GPS
Used with NIKON ED AF NIKKOR 80-200mm f/2.8 telephoto lens
set at ~150mm focal length. Field of view 6.9 x 5.3 degrees,
Time is accurate to within 50 milliseconds.
Site 0433 : Longitude 18.51294 deg East, Latitude -33.94058 deg,
Elevation 10 metres-situated in Pinelands (Cape Town),South Africa
FOR CLASSIFIED.TLE:
--------------------------------
33490 09 001A 0433 F 20120516170050448 55 15 1150153+063050 58
33490 09 001A 0433 F 20120516170938596 55 15 1159031+062301 58
33490 09 001A 0433 F 20120516171942275 55 15 1209074+061354 58
33490 09 001A 0433 F 20120516175332706 55 15 1242550+054253 58
20963 90 097B 0433 F 20120516172219235 55 15 1428115+033029 58
20963 90 097B 0433 F 20120516172753801 55 15 1433222+030748 58
20963 90 097B 0433 F 20120516173616716 55 15 1442008+022951 58
20963 90 097B 0433 F 20120516174059622 55 15 1446414+020949 58
25967 99 063A 0433 F 20120516172219235 55 15 1416194+063107 58
25967 99 063A 0433 F 20120516172753801 55 15 1421335+062441 58
25967 99 063A 0433 F 20120516173259825 55 15 1427005+061829 58
15543 85 010B 0433 F 20120516174312949 55 15 1509336-041846 58
15543 85 010B 0433 F 20120516174627868 55 15 1512459-043154 58
15543 85 010B 0433 F 20120516174844714 55 15 1515008-044136 58
27168 02 001A 0433 F 20120516163538177 55 15 1020413+104108 58
27168 02 001A 0433 F 20120516164042579 55 15 1025467+103907 58
27168 02 001A 0433 F 20120516164929423 55 15 1034364+103500 58
19976 89 035A 0433 F 20120516163538177 55 15 1021283+103439 58
19976 89 035A 0433 F 20120516164042579 55 15 1026297+102718 58
19976 89 035A 0433 F 20120516164929423 55 15 1035119+101414 58
33491 09 001B 0433 F 20120516165145125 55 15 1129121+063227 58
33491 09 001B 0433 F 20120516165345186 55 15 1130590+063049 58
33491 09 001B 0433 F 20120516165736992 55 15 1134307+062805 58
33491 09 001B 0433 F 20120516170050448 55 15 1137250+062517 58
35815 09 047A 0433 F 20120516165145125 55 15 1119354+053251 58
35815 09 047A 0433 F 20120516165345186 55 15 1121370+053308 58
35815 09 047A 0433 F 20120516165736992 55 15 1125287+053315 58
35815 09 047A 0433 F 20120516170050448 55 15 1128406+053244 58
35815 09 047A 0433 F 20120516170938596 55 15 1137312+053246 58
35815 09 047A 0433 F 20120516171942275 55 15 1147341+053218 58
STRAYS SEEN:
------------------
12618 81 069A 0433 F 20120516165345186 55 15 1137206+044320 58
27825 03 026A 0433 F 20120516170050448 55 15 1149463+063525 58
22931 93 078B 0433 F 20120516171942275 55 15 1155166+082938 58
25010 97 062A 0433 F 20120516172219235 55 15 1432462+051242 58
38107 12 013A 0433 F 20120516172219235 55 15 1433139+050846 58
32779 08 019A 0433 F 20120516172219235 55 15 1435202+050402 58
37344 11 001A 0433 F 20120516172219235 55 15 1430571+050955 58
33108 08 033A 0433 F 20120516172219235 55 15 1440298+052858 58
29163 06 020B 0433 F 20120516172219235 55 15 1441319+050352 58
32295 07 056C 0433 F 20120516172219235 55 15 1425165+051128 58
25924 99 053A 0433 F 20120516172219235 55 15 1426310+050755 58
21111 91 010A 0433 F 20120516172219235 55 15 1426473+051450 58
23968 96 042B 0433 F 20120516174059622 55 15 1452195+054056 58
27298 02 002A 0433 F 20120516172219235 55 15 1422240+050645 58
32050 07 037A 0433 F 20120516172219235 55 15 1422329+051038 58
37934 11 069B 0433 F 20120516172219235 55 15 1419370+053851 58
27525 02 043A 0433 F 20120516191341354 55 15 1614000+055024 58
23766 96 002C 0433 F 20120516191341354 55 15 1624384+054924 58
16199 85 102A 0433 F 20120516174312949 55 15 1510125-033153 58
14783 84 022A 0433 F 20120516174312949 55 15 1506175-055647 58
26487 00 052A 0433 F 20120516165345186 55 15 1132400+060917 58
NOTES:
-----------
(1) Did not intend to observe but long range weather prediction
indicated bad weather for the next few days so thought I had
better check up on the two unknowns observed on the 14 May
and I wanted to try a few experiments.
(2) Unknown 1 is in fact APSTAR 7- the elset I had was two days
old and indicated that the satellite was still drifting. As
Mike pointed out the later elset indicated the satellite was
now stationary and thus the unknown so that ones solved.
(3) Unknown 2 is almost certainly the missing PAN. It is still
drifting very slowly to the west and it looks like
HELLAS SAT 2 could be the next target.
(4) Did some more experiments. By measuring star trails at corners
and in centre I find the following
Top left corner 49.9 mm
Top right corner 47.1 mm
Centre 47.9 mm
Bottom left corner 47.1 mm
Bottom right corner 49.7 mm
In addition I have a field rotation of about 4 to 5 degrees in
going from left to right edges. Offhand I dont have a physical
explanation so is this due to defects in the camera lens ?
Since I am constantly changing the lenses that are used with
the camera I dont know if its really worth while trying to
improve these figures since the system is not static.
(5) I did try reducing the aperture. To date I have been using the
lens at f/2.8. I tried f/4.0 with a significant improvement in
image quality, especially in the corners so I went to f/5.6 and
even better quality. This is effectively reducing the aperture
of the camera from 150/2.8 = 54 mm, to 150/4 = 37.5 mm, to
150/5.6 = 26.8 mm so loosing magnitudes. One can compensate for
this by using longer exposures as one stops down from f/2.8 to
f/5.6, for example 30 sec at f/2.8 is roughly equal to 60 sec
at f/4 or 120 sec at f/5.6. As the geostationary satellites are
barely moving and are effectively a point source they integrate
well and appear to have the same brightness throughout but star
trails get longer and fainter as exposure increases.
At f/2.8 the faintest star trail is about mag +12 but at f/5.6
the faintest trails are about mag +9 so one has to decide what
is optimum and for the present f/4 seems a good bet.
A disadvantage of using too long an exposure is that the star
trails become too long which means less star trail ends to use
as a reference measure. In addition the image is criss-crossed
with leo satellites that passed through the field of view in
the (say) 300 seconds exposure.
(6) The current field of view is about 6.9 x 5.3 degrees with a focal
length of about 150 mm and if 1 bin mode is used for the CCD camera
the image scale is 7.6 arc seconds per pixel. Next time I fiddle
with the camera I will decrease the focal length to give about a
10 deg field - this makes the system even better for searching
for satellites or observing satellites a long way off time.
(7) I will continue measuring the geo survey images secured 14 May-
will keep me busy while it rains outside :-))
(8) For leo sat work I propose to use a 10 degree field with camera
in 4 bin mode for high sensitivity. If the positional resolution
proves inadequate I could go to using 3 bin or even 2 bin mode
but the lower the bin numer the bigger the image
4 bin is about 1 Mbyte whilst 1 bin is about 13 Mbytes.
(9) The term "bin" may not be familiar to non- CCD uses. With 1 bin one
uses the CCD camera at maximum resolution.( 1 bin = 1 pixel).
2 bin means the light from 2 pixels are summed together , which
means half the maximum resolution but double the sensitivity of
1 bin. Similarly 4 bin means adding the light from 4 pixels into
one, reducing resolution by 4 but increasing sensitivity to 4
times that of 1 bin mode. For leo satellites I use 4 bin mode but
for geosats use 1 mode.
(9) Sorry for the "details" but this might help other observers who
are contemplating using CCD cameras for satellite work.
Anyway my wife is always telling me I "talk" too much!
Cheers
Greg
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This archive was generated by hypermail 2b29 : Thu May 17 2012 - 12:39:19 UTC