Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

stargazine_ep3_banner.thumb.jpg.5533fb830ae914798f4dbbdd2c8a5853.jpg

Vroobel

My next project: tracking the ISS

Recommended Posts

Hi, 

As my GoTo is successfully finished (some cosmetic issues remain) I shoud focus my attention on planets' positions. I have proper source of information: fantastic book "Astronomical Algorithms" by Jean Meeus, thus I will sort the planets soon. But planets are not a challenge for me at this moment, they are just something obvious to do in my list. 

I have another idea and ambitious plan for next project within the year: locating and tracking the ISS to be able to make a video of its fly, not only transition. 

Similarly to other objects, I need some equations. I'm pretty sure they are available somewhere, because plenty websites or apps offer showing current position of the ISS. 

I will use this topic for sharing a progress ot the project. 

  • Like 1

Share this post


Link to post
Share on other sites

Oddly enough I was considering how I might go about this earlier this evening, even adding it to one of my many "things to do" lists.

James

Share this post


Link to post
Share on other sites
9 minutes ago, JamesF said:

Oddly enough I was considering how I might go about this earlier this evening, even adding it to one of my many "things to do" lists.

James

Just a coincidence :)

I will be happy to do it together with others. What kind of telescope do you have? 

Share this post


Link to post
Share on other sites
Just now, Vroobel said:

What kind of telescope do you have?

Well, I don't have a RASA or an RC :)

I'm guessing in my case the C9.25 would probably be the preferred choice, unless a wider field is required to stand a chance of actually finding the target.

James

Share this post


Link to post
Share on other sites
46 minutes ago, JamesF said:

Well, I don't have a RASA or an RC :)

I'm guessing in my case the C9.25 would probably be the preferred choice, unless a wider field is required to stand a chance of actually finding the target.

James

I realised it was improper question. What kind of mount do you have? :) And what is your idea for the ISS tracking?

I think it's too fast to simply use any GoTo feature to catch it and follow, so my idea is to calculate its position for 5-10 minutes later, to aim the OTA there and to wait, then to start the tracking in exact time. 

Look please at this site:

https://www.n2yo.com/?s=25544

They evidently use some equations for achieving Ra and Dec of the ISS. I need them only for the job. 

Another question is its radial speed. 

Now look please at this video:

https://youtu.be/qROmsXf8-fg

I understand that the ISS pass about 0.5 degree within about 1 second, so my stepper motors will work really fast and the tracking will be similar to a slew... 

BTW, I have 10" Newtonian scope on a Dobsonian mount. 

Tomasz 

Edited by Vroobel

Share this post


Link to post
Share on other sites

I'll have a look at the videos later.  I'm in the observatory at the moment and my network connection from here is not great.

I can use either a NEQ6 or HEQ5 for this.

There are videos online of people tracking the entire ISS pass, which sounds like it would make imaging much more practical.  I'll see if I can find them when I'm back in the house.

James

Share this post


Link to post
Share on other sites

Great! I'd like to ask an author or the site for his method of calculation the Ra and Dec. 

We have different mounts, so our ways will be different as well. I have the Raspberry Pi onboard and software written in Python completely by me, thus I can do whatever I want with my drives. But what are you gonna do to encourage your mount to find and track the ISS? 

Tomasz 

Share this post


Link to post
Share on other sites

At the moment I have no idea :D

First I think I need more information about the entire problem of tracking at speed.  I do recall the mount moving at quite a pace.  I imagine the sky model has to be pretty accurate to be able to hit the path of the ISS.

James

Share this post


Link to post
Share on other sites

For you, as an owner of better EQ mount, it can be quite easy using dedicated software working with the mount in EQMODE (I'm sorry for mistake if happened - I don't have this kind of mount):

https://github.com/AstronomyLiveYt/SatTraker

I just seen the video about tracking the Starlink, looks good. 

https://www.cloudynights.com/topic/644609-presenting-satellite-chaser-a-free-software-made-for-tracking-and-guiding-on-satellites-using-ascom-compatible-equatorial-mounts/

or

I'm not so clever in EQ area, the links are given me by users of Polish astro-forum in similar topic which I created earlier. 

I have both easier and more difficult task. I don't need to use any MoveAxis mode/command to follow the object, just need to calculate its position and delays between subsequent steps. But how to get the sky model, as you wrote? 

Right, let's continue when we get something. Thanks James :)

Tomasz 

Share this post


Link to post
Share on other sites

A quick hunt around this evening suggests that you just need to grab the latest TLE data for the ISS.  Then it's a case of finding it in the sky.

James

Share this post


Link to post
Share on other sites
1 hour ago, artem said:

Thanks artem. 

The software is for equatorial mounts:

"Satellite Chaser is a software made for tracking and guiding on satellites using ASCOM compatible equatorial mounts." 

I pasted link for it earlier, so maybe James or other owners of equatorial mounts will be interested. I have motorised my Dobsonian mount, which is quite unique, so I have to find another way. 

Share this post


Link to post
Share on other sites
28 minutes ago, JamesF said:

A quick hunt around this evening suggests that you just need to grab the latest TLE data for the ISS.  Then it's a case of finding it in the sky.

James

I agree with you, James. If I understand it properly we can get a kind of set of positions for next 300 seconds. It's not too much. I think the API gives data about now + 300 seconds, but I'd like to have data about 10 mins later + next 300 second. Without some attempts I can't say anything. 

As I read earlier in the linked sites, the software for equatorial mounts use the TLE data as well.

Tomasz 

Share this post


Link to post
Share on other sites

At a second look it seems to be not so easy.

First of all you have to provide coordinates of your location. It can be your home or some other places, more then one, but you have to choose one as default. Every time you request for data from the server sending dedicated license key you do it for the selected location. I just checked: added my home coordinates taken from GPS in my telescope and also another location outside the city taken from Google Maps - the most recent location is always the selected one, but you can change the selection. Thus you have to be prepared and location has to be provided and selected if you want to track the ISS outside your home.

Every request for positions of the ISS is limited to 300 sets of data, every position is for one second, thus you have set of data for following 5 minutes. It not too much. You can ask for the data maximum 1000 times within 1 hour. My Az drive allow to revolve the telescop 360 degrees within 5 minutes (I know, it's not fast...), I shoud reach an opposite (faretst) position within 2.5 minutes. I should figure out how to aim the telescope in position, where the ISS will be after maximum 2.5 minutes, then the tracking shoud do its job within remaining 2.5 minute. It's long enough to make quite nice video. 

Not bad, but it's still not set of desired equations...
 
I'll try to play with that a little bit, but will still seek another way.  How the Stellarium is doing that? It use TLE data as well, but I launched it with no internet conection, so it couldn't get data from the serwer, but it is working despite no link with serwer. Interesting...

Share this post


Link to post
Share on other sites

If Stellarium is working without an internet connection, perhaps it may not be accurate?  Or perhaps Stellarium has some other special arrangements.  However, as it is open source, you could at least have a look at the code and see what is going on.

James

Share this post


Link to post
Share on other sites

BTW, a video linked below shows how it should work. There is Starlink recorded, but the idea is exactly same. I expect a little bit longer delay between the slew and the tracking related with my software, but can't be sure. 

You can hear single "beeps" with decreasing intervals, so I think the mount reaim an OTA several times, then the proper tracking starts. Unfortunately palm-trees are disturbing. 

A most interesting part begins after 16.00 minutes. 

Tomasz 

Share this post


Link to post
Share on other sites
On 27/08/2019 at 00:09, JamesF said:

If Stellarium is working without an internet connection, perhaps it may not be accurate?  Or perhaps Stellarium has some other special arrangements.  However, as it is open source, you could at least have a look at the code and see what is going on.

James

I think the Stellarium is accurate enough within 30 days since update of TLE. Wht is the TLE?

https://en.wikipedia.org/wiki/Orbital_elements#Two-line_elements

You can get it from the https://www.n2yo.com site after registering. Every time I get it I have same numbers, because possibly it's valid for some time or forever - I don't know yet. I saved a file with the data and will check it for every several days. I read on Wiki that it becomes inaccurate after 30 days.

I found similar need of the Ra and Dec coordinates here:

https://www.physicsforums.com/threads/satellite-right-acension-and-declination-calculations.220399/

then jumped to mentioned subject:

https://en.wikipedia.org/wiki/Orbital_elements

and found the description of the TLE. After then I found the pdf file: spacetrk.pdf - it's there: 

https://www.celestrak.com/NORAD/documentation/spacetrk.pdf

And here my headache began...

I know that the TLE includes coded orbit of the ISS, but is here any matematician / physicist / astrophyisicist able to pass through the equations and receive the Ra and Dec? 

But I found also this: 

https://github.com/brandon-rhodes/python-sgp4 - "Python implementation of most recent version of the SGP4 satellite tracking algorithm".

So will try to sort it out.

Tomasz

Edited by Vroobel

Share this post


Link to post
Share on other sites

NASA publish TLEs daily for the ISS and more than once daily if it's docking.

Did this awhile ago using Meade Wedge mounted SCT,  I had to enter 8 lines of code as a user object, things like AOS (acquisition of signal) set minimum AOS, Epoch (year) (day) from TLE rounded to 4 decimal places to give accuracy of a couple of minutes, inclination, RA ascension node, eccentricity, argument of perigee,  mean anomaly, mean motion etc.

IIRC it was lacking a LOS (loss of signal) to stop it so had to abort it manually otherwise it kept tracking below horizon.

Dave

Share this post


Link to post
Share on other sites

Thanks, Dave. 

Could you please share some details with us? I'm interested in and technically ready tor the accuracy of seconds. 

Tomasz 

Edited by Vroobel

Share this post


Link to post
Share on other sites

Hi Tomasz, I can't pretend to understand the mathematics involved and just followed instructions on how to fill in various parameters using the TLE data.

Data is supplied to a few decimal points and rounded to the desired level of accuracy, IIRC I rounded to 4 points.

This was specifically for a Meade Alt / Az mounted scope, not sure if it applies directly to EQ mounts.

I have a 10Micron EQ mount that does a similar but much more accurate thing, just download updated ISS TLEs into the mount and it will track the ISS perfectly.

Some years ago there was a Windows Java script app that downloaded the TLEs and sorted them into correct format to enter into the mount, around Win XP times I think, not much good now I guess as Microsoft have abandoned Java support.

I'll see if I can find any links to the old Meade site but don't think it's active anymore.

Good luck

Dave

Edited by Davey-T

Share this post


Link to post
Share on other sites

Hey guys,

Developer of Satellite Chaser here. I’ve added support for Alt/Az mounts. I don’t have an Alt/Az mount, so this could be buggy, please give me feedback if you try my software.

In case someone does try my software with an Alt/Az mount: Make sure that in the mount tab N and S correlate to Altitude movement and W and E correlate to Azimuth movement. Also do a test run as detailed in section 9.1 of the manual. In the guide and cockpit tab Ra is synonymous with Azimuth and Dec is synonymous with Altitude.

Specifically to your homemade mount: It needs to support arbitrary MoveAxis commands to work with my software. I too have made my own mount, mine is equatorial, but it also works with a Raspberry pie and python. Nice to see someone else with a similar setup.

A bit about how I calculate the position of the satellite in my software: I use the python library pyephem, the script is only about 30 lines. It takes time, TLE and Longitude/Latitude as Input and gives the Altitude, Azimuth, RA and DEC for a pass as output. Satellite Chaser then uses that info, takes the first derivative of the position data (which results in speed) and then feeds these speeds to the mount 10 times per second.

Because it hasn’t been mentioned yet: The easiest way to get the newest TLEs is via celestrak: https://www.celestrak.com/NORAD/elements/stations.txt

Edited by ngc3031
  • Thanks 1

Share this post


Link to post
Share on other sites

ngc3031, thats very clever!

Quote

>>> import ephem
>>> mars = ephem.Mars()
>>> mars.compute('2008/1/1')
>>> print(mars.ra)
5:59:27.35
>>> print(mars.dec)
26:56:27.4

I just checked, the Mars show's little difference in comparison to the Stellarium, but the Jupiter is nearly exactly same! I'm impressed! I can use it instead of typing hundreds line of code based on the "Astronomical Algorithms".

After a check of all planets I think is more accurate for the gas giants then other planets, but I gonna play with it! Even with the tiny inaccurates I can use a wider eyepiece to find the planet and then use another one.

Let's try the ISS...

Share this post


Link to post
Share on other sites

Oh, mate, that's awsome! 

I just checked the ISS. Accuracy of the library is equal around 1 arcsecond! 

Regarding your software, the Satelite Chaser, I found out about it from one of our Polish astro-amateur, but I couldn't use it because of not equatorial mount. Moreover, my mount is not compatibile with any existing standard (that can change...).

Actually I am happy to have fantastically working library giving me the required Ra and Dec. 

Now I have to think hard how to make the proper slew to expected position and wait for the ISS. There is no place for mistakes, I can make 1 attempt per sesion, as I read the ISS is well visible once per 63 days. Maybe it's visible through the telescope, byt not so good. It will take some time.

https://rhodesmill.org/pyephem/

Best regards for all engaged! :)

Edited by Vroobel

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Giedrius05
      Dear colleagues,
      I am new in astronomy and got my SkyWatcher Star Discovery 150Pi WiFi AZ GoTo, however I am experiencing one big problem. When I try to align my telescope using SynScan Pro app on laptop or smartphone the telescope always points wrong direction. I do not have hand controller.
      I set telescope north using compass, enter latitude and longitude, but when try to align 1 star or 2 stars, telescope spins way, way off. When the star is in the South East it shows north east, or sometimes points absolutely wrong direction. When it is set on the north and object is 98 degrees east it goes some 30 degrees. It also points lower or higher.
      I am totally lost.
      I use 8 AA batteries.
      What I do wrong?
      How to fix this?
      Thank you.
       
    • By Gryffster
      Hi - I'm a relative newcomer to telescopes with goto - still trying to figure them out.
      I have a problem with Goto on the 8SE.
      Alignment usually works (Not always, but usually)

      I believe my set up is correct - time and date, DST and UTC (It's currently BST in the UK)

      I usually use 2-star alignment (Currently, most convenient for me are Sirius and Procyon)
      Alignment usually succeeds, but goto just doesn't. The scope slews away, sometimes even to a completely different part of the sky from the selected object (I'm familiar enough with
      the sky to be able to identify several bright stars without assistance)
      Bizarrely, this happens even if the goto object is one of the alignment stars - how could it possibly not be able to find a star when you've explicitly told it where it is?
      I've read that goto sometimes doesn't work well on battery power, so I've aquired a mains adapter. No change.
      I haven't yet updated the handset firmware (I'm waiting for a serial-usb adapter.)
      Any help would be appreciated.
      Thanks
    • By CoolJWB
      For quite a while I've had an issue where the images I take have trails that show up when going higher then about 20 seconds exposure time. I do a rough polar alignment where you can still see the polaris in the scope as I live in the north of Sweden and the EQ3-2 mount doesn't allow for accurate adjustment above 64 degrees.
      I'm 100% sure that the locatation, time zone and time is correct, I've also parked the scope to the position with the scope facing polaris and the weights downwards. I did a 3 star alignment and after a 1 min exposure with my Olympus 420 the result was as the first image I attached. For 20 second exposures I get the second image attached but once in a while without having touched the scope (yes I am 100% sure of this, I stood perfectly still a good distance away from the scope and triggered the shutter with a remote control) I get results such as the third image.
      My guess is that the cogwheels are slipping somehow but I'm gonna ask here to be sure.
       



    • By Spider-Man
      Hi everyone,
      I'm looking to get a reasonably portable astrophotography set-up, using a 60-100mm refractor, with a suitable goto mount.  I spotted the Explore Scientifice exos2-gt with pmc-eight goto system, which looks like quite an elegant solution, and wondered if anybody in the forum owns this mount, and what they think of it's performance & usability?
    • By Andy_ZH
      Hello all,
       
      this is my first post at SGL, and it will be quite long. I am not native a English speaker, so please excuse any mistake.
       
      I have quite some plan with my telescope mount and its goto control, and I am looking for some feedback and comments. If somebody else did a similar project, please let me know. And please feel free and encouraged to make suggestions, ideas, critics, etc.
      The story in a few buzzwords: Raspberry Pi Zero → direct control of TMC2209 stepper drivers via the Pi's Uart serial interface to drive my telescope mount. I am writing a software (optionally: open source?) to control the mount. The language will NOT be C, as typically used for Microcontrollers (I know for instance OneStep)
      I am using Kotlin, which is a more advanced JVM language.
       
      I think this should be enough information to filter the readers who are interested in reading the rest of my post.
       
      Now the long and detailed story:
      My professional background: I am a physicist, and did a PhD in EE (Power Electronics). Later, I became software engineer. Besides being fascinated by Astronomy, I am a tinkerer (Reprap 3D printer, electronics, …). I did grind my first mirror (a 6'' Schiefspiegler) when I was 15 years old, and I built the cookbook CCD cameras in the 90's.
      After many years without a telescope (study time, relationship, ... ), I settled down with my family, and I started to get back to Astronomy.
      Recently, I did by a quite a massive second hand mount: the “Vixen New Atlux” from another other stargazer in Switzerland. My opinion is that the New Atlux' mechanical design is superb. It has (had...) internal wiring, the counterweight bar can be hidden in the mount for transport, good polar alignment screws, it has an excellent polar finder with a dimmable LED.
      But on the other hand the electronics: two weak servo motors in combination with the incredible Starbook 5.... Seigh... the starbook...(!) it is, well... the mount is just superb, and no more comments about the starbook game boy, which shall rest in peace at the garbage dump.
      I removed the servos and all electronics, and I put 2 stepper motors into the mount, which are coupled to the gear with a timed belt. My original plan was to put an Arduino into the mount in order to control the steppers. I have an old goto Celestron cg-5 with Starsense, and it would have been quite easy to mimic - with the Arduino as interface – the servos of the old cg-5 and translate the Starsense control signals to my New Atlux. I can write C, and there is even an open source project called OneStep, which uses a Microcontroller in a similar way as I do.
      But I don't like to write C code anymore. In the 3D printer community, people need to use real time electronics to control the printer steppers. Due to the real time requirement, C with a real time microcontroler (Arduino & similar) are the only option for 3D printers.
      Do we need real time for our telescope? No. We don't need to control a lot of Motor accelerations and high speed control. For the telescope, we need to set the Motors speed precisely, and we need to drive to any position in an accurate and controllable and slow way.
      Then, there are new stepper motor drivers available with as much as 256 microsteps. The TMC2209 stepper driver , which is very well know in the 3D printer community, is not vibrating at all. It runs just smoothly, also at very low speeds. I do drive my motor with 0.25 rpm (sideral speed). In case of a slew, I can accelerate to 1500x sideral speed, which also would allow me easily to track the ISS. Wonderful.
       
      The current status of my project is:
      The mount is equipped with the two new motors The TMC2209 drivers are connected to the Raspberry pi GPIO Interface, and I can control them via Software. Theoretically, I could attach up to 4 motors with a single Uart interface (1 wire protocol). For instance, a focuser or a filter wheel could be attached. I selected Kotlin as language. Java also would have been possible, but I think for a new project, Kotlin will lead to a much more readable code. The TMC drivers can be driven via a chip-internal clock signal. Different to what the 3D printer community is doing (they use the step / dir pins, and create every single microstep with the microcontoller), I can send a “speed” signal from the Raspi via UART to the 2209 chip, and it will execute this speed for me without any further action. The only time critical issue was that I need to precisely count the steps that the 2209 stepper drivers executed. This is done via a GPIO pin, receiving its index signal (a pulse for every 2209 fullstep). Here comes the pain with Linux (non real-time) and the Pi: For user programs, it is impossible to guarantee that every pulse from the stepper drivers will be registered. But I cannot afford to have a step count drift over time. The solution was that I wrote a Linux kernel module in C. I wrote that I don't want to write any C code. Well, a few lines for the kernel module were indeed necessary. I can live with that, having in mind that the rest will be written in Kotlin. The only task of the Kernel module is to count every registered step at the Pi's GPIO input pins. This kernel module output is then mapped to a character device file in /dev/ for every stepper. In Kernel space, it is possible to register and count interrupts without missing even any one of them. From a hardware point of view, this is indeed everything we I need. The project cost so far: 2x10€ for the stepper drivers, 2x10€ for the motors, 2x20€ for the tooth belts and pulley, 10€ Pi Zero plus some peripheral expenses: Micro SD card, USB charger, and 1200 € for the used Vixen new Atlux mount. And a lot of time.
      I have so many ideas on how to extend the ecosystem of my software, but these ideas are for the longer term (maybe years from now on):
      Multi-star alignment. The alignment should be able to be updated continuously during an observation night. With a set of stars, it should be possible to calculate the quality of the aligment points, and e.g. drop them if they are errorneous. PEC correction (should be easy on the Pi) End-Stop support The polar alignment routines of today's goto scopes are quite good. But what I would like to have is some audio-feedback when I move the alignment screws into the right direction. Possibility to pre-plan an observation night (e.g. the mount could tell you that the Jupiter moon shadow will be on Jupiter in a few minutes). Record the telescope movements during the night in order to be able to tag any picture. The TMC drivers have much more capability than what I am using currently. For instance, they could be current controlled for slews in order to set the stepper current exactly to the value that it needs without stalling. This saves a lot of energy. The TMC drivers have a feature called “Stall Guard”. This could be used instead of endstop switches (for 3D-printers, this is done frequently). Advanced options for tracking: siderial, solar, moon speed, ISS speed. Tracking in both axis (e.g. to compensate polar misalignments of atmospheric refraction) or just in right ascension. Commercial mounts do not allow much customization here. With slow slew speeds, 5V input via a USB-C cable is sufficient for the Pi + Motors. Usb-C and newer usb battery packs allow to output a higher voltage via USB. With an “USB-trigger”, the input voltage can be selected to my needs. Higher voltage allows higher slew speeds, but consumes more power. Autoguider support, or even better: simply connect a webcam via the Pi's USB connector and do the guiding on the Pi The Raspberry Pi touch screen could be used for telescope controlls Advanced German mount limits and meridian flip control (e.g. a warning about a necessary flip when driving to a specific goto target). An Android App, connected via WiFi to the Pi could be used as display alternative Language control (have a look at Mycroft, an open-source artificial intelligence). "Hey mount, please slew to the whirlpool galaxy!" Control the mount via SkySafari and Stellarium The Pi has a built in camera interface. How about an open source auto align? The Pi could look at the stars to align itself, which makes a lot of sense. I did already order a long focal length lens and monochrome camera from Arducam in order to do some experiments (the standard Pi camera has 3.5 mm focal length and is not really usable, although star imagining is possible). My first observation site is my balcony. And there, the real Starsense does not work at all. It always spin-loops on 2 alignment positions where the sky is covered by the roof – how silly is that?. This can be done better. Further, Starsense is doing only a initial alignment. It should update its position and accuracy over the time! I think I could do this better.  
      Besides all my ideas, the first and most important focus of the software will be:
      Readability (therefore my choice of Kotlin), extensibility and open source. I like to have the Maths of the internal mount model clearly visible and understandable in the software. The calculations that are done within all our goto mounts are no rocket science. I admit, I am the nerd guy who wants to go the hard way and implement this from scratch.
      I am looking for a good project name, do you have any suggestions? How about QuickStep? this is possibly too close to OneStep and would offend the creators of OneStep?
      Does anyone of you have interest in joining my plan? Doing such a project in a small group would be more encouraging then just doing it for myself. And of course later on, I would appreciate if other stargazers would update their old mounts with my software.
       
      Any comments on my project plan are welcome!
       
      Clear Skies!
      Andy
       

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.