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27 Feb 2017
INDI development team is happy to announce the release of INDI Library v1.4.0. This new exciting release builds on the maturity of INDI Library and comes with many new supported devices and fixes for existing drivers. Several improvements and enhancements are included in this release including native support for Cygwin and MacOS platforms in addition to Linux, BSD, and Windows (Client only).
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TOPIC: Satellite confusion

Satellite confusion 3 months 3 weeks ago #13390

  • Ihoujin
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I have Python v3.5.2 installed, and is producing that invalid syntax error

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Satellite confusion 3 months 3 weeks ago #13398

It might be not enough to have it installed. You also need to run python3x explicitly if there is also python2 coinstalled, and that depends on your linux distribution.
But have you tried:?
python3 pyephem.py

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Satellite confusion 3 months 3 weeks ago #13402

I tried to reproduce the track of a satellite:

Target Date: 30. Dez. 2016 17:24 UTC+1 (Berlin)
Location:
latitude = '51:3:29.34'
longitude = '13:46:33.24'
Target: ARIANE 40 R/B (Catalog Number: 22830)
Space-Track Data:
0 ARIANE 40 R/B
1 22830U 93061H   16364.00328609 -.00000053  00000-0 -24714-5 0  9995
2 22830  98.8887   9.4732 0011806  66.9235 346.0813 14.31413803213905

If I start kstars and set the target date the satellite is just above the star Mizar (Ursa Major) (only visible disabled).
I also checked in stellarium, the satellite is at the same position.


But when I enter the data in the pyephem script and run it , it tracks a complete different position in kstars:


It seems the script uses the system time in UTC to show the position in kstars but wouldnt it be usefull (i dont know if it is possible) if it where using the time that is currently set in kstars (in cases I want to simulate a session)?

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Satellite confusion 3 months 3 weeks ago #13404

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The computer date is used for the tracking. If you want to simulate the tracking for an other date you can add a bias by changing this line:
obs.date = ephem.now()
in
obs.date = ephem.now() + 4*ephem.hour + 40*ephem.minute
for an event 4h40 in the future

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Satellite confusion 3 months 3 weeks ago #13406

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Great, running it with python3 worked.
I made an account at space-track.org and found the TLEs for the ISS.
I copied TLE lines 1 and 2 in place of the original TLEs in the posted script.
I couldn't seem to input the target name, and get this error:

Configure PyEphem ... Traceback (most recent call last):
File "SatelliteTrack.py", line 130, in <module>
satellite = ephem.readtle('TARGET',TLE_line_1,TLE_line_2)
ValueError: line does not conform to tle format

How do I properly input the target in TLE format?

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Satellite confusion 3 months 3 weeks ago #13410

@lhoujin
There are two lines in the script quite on top. Just replace the text in the quotes with the data you got from space-track "Retrieve TLE Data by Satellite Catalog Number" and enter your location.

@ farom thanks.
I just did a quick and dirty test to track this Ariane 40 R/B with your script. I doubt that you will ever get good precision tracking
of fast objects like satellites or ISS with this method, especially with my EQMod SynScan mount. The tracking commands are way to long.
You would need much shorter guiding pulses or constant pulses and also a very good mechanic in your mount.
Here is an image and at least I found the satellite :) You can see the long spikes of the stars and how the script repositioned the scope. The short faint lines between the two bright stars is the satellite.

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Satellite confusion 3 months 3 weeks ago #13413

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Thanks you for the feedback. It was the kind of problem I was expecting. Reducing the guiding duration may help but I am skeptical about the fact that it will allow a smooth tracking (do not try to reduce update_delay in the script, it wiil have no effect as pyephem has a time resolution of 1s).

It would be better to control individually RA and DEC speed but I haven't found a standard way to do that. I will add a dedicated property in the driver of my homemade mount. For other drivers I was thinking about timed pulse guide but it seems to be limited to very low speed. Do you have an idea ?

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Satellite confusion 3 months 3 weeks ago #13422

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@pauledd Thanks I found my mistake. Problem was I did not include the 1 and 2 at the beginning of the two lines.
I think that image shows great promise. If that were the ISS while recording video, I bet there would be plenty usable frames. I'd be satisfied with simply maintaining it in the FOV for that reason. Absolute precision is likely not achievable. Alternatively implement leapfrogging to a point it will soon cross, then jump ahead a bit and wait for it to pass again.

What mount did you use for this? I have an HEQ5. I'm considering satellite chasing with just a guidescope CCD on it rather than my full setup.

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Satellite confusion 3 months 3 weeks ago #13423

HEQ5 here too. You might get into trouble with the fov. I dont know how much you want to magnify. Just one thought: the image I took was at 550mm focal length. For the ISS you will certainly use a much higher focal length (I dont know, I never tried it). But assuming that you double to 1000mm you then have a 1s guiding pulse that almost fills your fov (with sensor size 5184x3456, if you record with lesser your fov will shink even more) plus ISS is much faster than the Ariane junk that I captured

But hey, I dont want to prevent you from trying this as I really dont have any experience in that area. :P

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Last Edit: by pauledd.

Satellite confusion 3 months 3 weeks ago #13433

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My telescope is 1000mm F5. FOV of 1.28° x 0.85° with Canon 600D DSLR
Guide scope 280mm F4.6 with an FOV of 58.93' x 44.2' with ASI120
Nobody said this would be easy. ;)
I have managed to capture some ISS by manually pushing the scope while trying to keep it in my finder crosshairs on the EQ mount. A task that would have been made simpler with a dob or any ALT-AZ.

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Last Edit: by Ihoujin.

Satellite confusion 3 months 3 weeks ago #13443

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farom wrote: It would be better to control individually RA and DEC speed but I haven't found a standard way to do that.


That sounds to me a bit like how guide rate functions. As a multiplier of some fraction of sidereal rate set and a proportional rate. Just brainstorming here, but as you say, rather than issuing a series of slew target commands; calculate and instruct the mount with differential guide rates instead. I know ASCOM is dumb, but I think it can take instructions to move RA/DEC at such and such rate until told otherwise. That might track better and also free up slew commands to manually enter corrections?
I really don't know if that's how it works or not though, but it seems logical to me. :silly:

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Last Edit: by Ihoujin.

Satellite confusion 3 months 2 weeks ago #13478

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It certainly should be possible to adjust the RA and DEC slewing rates independently.
They describe such a function they call a continuous tracking state for a sattrack app used with EQ-Mod.
http://eq-mod.sourceforge.net/faqs/sattrack.html
Maybe if this is open source it can be ported over?
Edit: It's not open source, it's shareware.
I wonder if they would be willing to collaborate on a Linux port, as it appears to be Windows only.
At least this shows that custom slew rates + pulse guiding commands are possible for satellite tracking.
Their website: heavenscape
Their app in action: EQMODLX: Satellite Tracking

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