163 lines
4.1 KiB
Markdown
163 lines
4.1 KiB
Markdown
# skymap Mini HOWTO
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HOWTO find a particular satellite for viewing with skymap
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for use with stvid imaging.
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From notes by Cees Bassa mixed with my misunderstandings.
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This example will use the Bluewalker 3 satellite, with NORAD ID 53807.
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# TLE
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First a TLE is needed. I get this from Celestrak, ala:
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```
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wget -O ~/devel/spacecruft/TLE/bluewalker3/bluewalker3.tle \
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"https://celestrak.org/NORAD/elements/gp.php?CATNR=53807"
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```
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Should look something like this:
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```
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BLUEWALKER 3
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1 53807U 22111AL 22323.16311390 .00001894 00000+0 10565-3 0 9997
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2 53807 53.2016 312.3504 0014195 129.0685 231.1577 15.18596984 10510
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```
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# Skymap Script
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Run skymap (with my branch):
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```
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#!/bin/bash
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LENGTH=86400
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TIME="2022-11-19T17:20:45.000"
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TLE=~/devel/spacecruft/TLE/bluewalker3/bluewalker3.tle
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SITE=9990
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LAT="40.568912"
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LONG="-105.225852"
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# Set elevation in data/sites.txt
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# 9990 JM 40.568912 -105.225852 1843 Jeff Moe
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#ELEVATION="1843"
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skymap \
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--no-stars \
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--width=1600 \
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--height=1000 \
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--all-objects \
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--nmax=128 \
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--length=${LENGTH} \
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--catalog=${TLE} \
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--latitude="${LAT}" \
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--longitude="${LONG}" \
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--time="${TIME}"
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```
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# Skymap Window Overview
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Above is a 24 hour (86400 seconds) prediction for
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Bluewalker 3 for the example location.
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* Grey tracks are in the shadow.
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* Orange tracks are in sunlight but during daytime.
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* Yellow tracks are in sunlight but during night time.
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The example has two passes during night time:
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* Low South East.
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* Low South West.
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# Skymap Interactive
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In interactive mode, use `l` to change the track length to 3600 secs (1 hour).
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To use `skymap` in interactive mode, launch `skymap` from the command line.
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When you hit `l` in the graphical display, the prompt will be in the terminal
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window.
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Then use `.` to move time forward with these 1 hour steps.
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It makes it faster if `skymap` is run without drawing stars until needed,
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especially during frequent re-renders.
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Disable viewing stars with `shift-Q`.
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At some point you'll get the first pass.
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* Use `<` a few times to reduce the timestep size to something like 450 seconds.
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* Step forward with `.` until it is above the horizon.
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* In example, move time forward to `00:37:37`.
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# Skymap Satellite Info
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Press `i` with the cursor near `53807`.
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It gives this output:
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```
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BLUEWALKER 3
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1 53807U 22111AL 22323.16311390 .00001894 00000+0 10565-3 0 9997
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2 53807 53.2016 312.3504 0014195 129.0685 231.1577 15.18596984 10510
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Age: 0.9 d
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x: +5351.2801 km; vx: -0.38650 km/s
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y: -2422.0234 km; vy: +6.04035 km/s
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z: +3590.7817 km; vz: +4.61568 km/s
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r: 1633.97 km; v: -0.343 km/s
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l: -92.78; b: 31.44; h: 506.35 km
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R.A.: 01:13:17.38 Decl.: -19:10:17.4
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R.A.: 01:12:10.33 Decl.: -19:17:33.2 (J2000)
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Azi.: 127.8 Alt.: 11.3
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Phase: 53.17
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Magnitude: 6.25
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Angular velocity: 0.2593 (deg/s)
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```
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This gives you the Az/El and RA/Dec to read off.
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# TLE with `tleinfo`
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Cees dumped the TLE for `53807` into a text file with
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```
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tleinfo -i 53807 >53807.txt
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```
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This results in two TLEs, though ? XXX compare with TLE from above.
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```
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BLUEWALKER-3
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1 53807U 22111AL 22291.57105995 .00000747 00000+0 51211-4 0 9998
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2 53807 53.2021 96.3521 0013619 43.3355 316.8709 15.18466480 5717
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0 BLUEWALKER 3
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1 53807U 22111AL 22291.57105995 .00000747 00000-0 51211-4 0 9999
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2 53807 53.2021 96.3521 0013619 43.3355 316.8709 15.18466480 5717
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```
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# Views
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View with `e` for East.
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View with `s` for South.
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# gpredict
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This is view of BW3 in `gpredict`, for comparison.
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# stellarium
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This is view of BW3 in `stellarium`, for comparison.
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