Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

The ISS reaches out and touches Mars, transit on September 14, 2020

  • Please log in to reply
95 replies to this topic

#76 Tom Glenn

Tom Glenn

    Soyuz

  • -----
  • topic starter
  • Posts: 3,650
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 08 October 2020 - 03:05 AM

Thanks for the additional comments.  I hope people aren't becoming too fatigued from this thread, as it has gone for several weeks now.....(although it's easy enough to ignore if so!).  I did have one minor update.  Szabolcs Nagy (Space Station Guys) selected my image as the ISS photo of the month.  He also pointed out to me that if I center the gif on the ISS, it provides an interesting perspective of the transit.  Below is an example (this is 50% scale, because for some reason the animation doesn't play automatically if the file is larger......this is also almost 10x slower than a real time playback.....the actual transit was very fast, as can be seen in the original YouTube video).

 

ISS_centered_transit2.gif


  • Yu Gu, dswtan, KpS and 7 others like this

#77 HentySky

HentySky

    Ranger 4

  • -----
  • Posts: 380
  • Joined: 22 Apr 2013

Posted 08 October 2020 - 03:45 AM

That is a one in a million shot, fantastic Tom.  Cheers



#78 Humble Narrator

Humble Narrator

    Sputnik

  • -----
  • Posts: 31
  • Joined: 13 Aug 2020

Posted 08 October 2020 - 06:55 PM

Thanks for the additional comments.  I hope people aren't becoming too fatigued from this thread, as it has gone for several weeks now.....(although it's easy enough to ignore if so!).  I did have one minor update.  Szabolcs Nagy (Space Station Guys) selected my image as the ISS photo of the month.  He also pointed out to me that if I center the gif on the ISS, it provides an interesting perspective of the transit.  Below is an example (this is 50% scale, because for some reason the animation doesn't play automatically if the file is larger......this is also almost 10x slower than a real time playback.....the actual transit was very fast, as can be seen in the original YouTube video).

 

attachicon.gifISS_centered_transit2.gif

Words can't describe. New Thierry Legault.



#79 Tom Glenn

Tom Glenn

    Soyuz

  • -----
  • topic starter
  • Posts: 3,650
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 09 October 2020 - 06:18 PM

Thanks for the kind words Brett and Humble Narrator.  

 

I would be quick to say (in response to the previous post immediately above) that while it is certainly flattering to be compared to Thierry, he has been producing amazing ISS (and other) images for multiple decades now, so I have a fair bit of catching up to do in that department!  

 

As an aside, it came to my attention in another thread that Calsky.com is going belly up!  I had no idea about this, and this is really bad news, because it played an integral part in this capture!  I wonder what alternatives people will use?  TransitFinder.com is just as good for lunar and solar ISS transits, but is limited to only that data.  Calsky had an amazing assortment of satellite data (and asteroids), and also gave very nice star charts, ground maps, and everything you would need to plan an observation.  All of the orbital TLE data is available for download elsewhere, and we have been learning of some other satellite tracking software in the other thread (link here), but I wonder what resources can be used to predict more obscure transit ground paths, such as my Mars transit, in the absence of Calsky?  Or for monitoring all of the other satellites and asteroids that Calsky included, and producing the maps?  Maybe it will be easy replace Calsky with other resources, but it will be missed.


  • dswtan likes this

#80 Tom Glenn

Tom Glenn

    Soyuz

  • -----
  • topic starter
  • Posts: 3,650
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 14 October 2020 - 04:12 AM

I have a little bit of bonus data to share, that was not previously reported.  I captured a video recording with an 18mm lens and my Nikon D5600 during the transit.  I simply set it up on a tripod and let it go without any interference, while I was dealing with the main capture.  In the immediate aftermath of the event, I found the results with the 18mm lens underwhelming, although looking back at the data, there are some interesting aspects.  Although it is impossible to convey what it was like to be there, this wide field view documents the final moments before the transit.  This video begins as the ISS is exiting Earth's shadow.  You can see that it starts out quite dim after shadow exit, and then takes some time to increase in brightness.  In fact, in retrospect, I was lucky that the transit didn't occur any earlier than it did, or the ISS would have been underexposed.  

 

https://youtu.be/I2n-GOo3r-I


  • dswtan, John Boudreau, KiwiRay and 2 others like this

#81 kevinbreen

kevinbreen

    Gemini

  • -----
  • Posts: 3,070
  • Joined: 01 Mar 2017
  • Loc: Wexford, Ireland

Posted 14 October 2020 - 04:28 AM

I have a little bit of bonus data to share, that was not previously reported. I captured a video recording with an 18mm lens and my Nikon D5600 during the transit. I simply set it up on a tripod and let it go without any interference, while I was dealing with the main capture. In the immediate aftermath of the event, I found the results with the 18mm lens underwhelming, although looking back at the data, there are some interesting aspects. Although it is impossible to convey what it was like to be there, this wide field view documents the final moments before the transit. This video begins as the ISS is exiting Earth's shadow. You can see that it starts out quite dim after shadow exit, and then takes some time to increase in brightness. In fact, in retrospect, I was lucky that the transit didn't occur any earlier than it did, or the ISS would have been underexposed.

https://youtu.be/I2n-GOo3r-I


Simply amazing!

#82 Thirteen

Thirteen

    Gemini

  • *****
  • Posts: 3,186
  • Joined: 12 Jul 2013
  • Loc: Milford, Michigan

Posted 17 October 2020 - 10:29 AM

Hello Tom!  That capture is pure magic.   Saw it on APOD and other places!   Anyway, I landed here because of the CalSky issue.   Wondering if you had any progress on finding an alternative?



#83 Tom Glenn

Tom Glenn

    Soyuz

  • -----
  • topic starter
  • Posts: 3,650
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 17 October 2020 - 11:48 AM

Hello Tom!  That capture is pure magic.   Saw it on APOD and other places!   Anyway, I landed here because of the CalSky issue.   Wondering if you had any progress on finding an alternative?

Jason, thanks for the kind words.  I see you also have another post asking about Calsky.  Sadly, I know of no equivalent alternative, and from my investigations on the web (including social media), it appears that most ISS imagers likewise have no alternative at the moment.  The raw orbital data is all available, but packaging it into a useful format the way Calsky did would take substantial effort, which is why the website failed.  Most people with the knowledge to create a website such as Calsky also have full time jobs doing something else, and so it becomes unsustainable.  The most likely solution here will be for someone to resurrect it, but as part of a paid subscription program, either working with the creators of Calsky, or as a completely independent endeavor, ideally with sponsors (that have money).  But the free system (with voluntary donations) is obviously not viable (although it did have a long run). 


  • dswtan likes this

#84 Humble Narrator

Humble Narrator

    Sputnik

  • -----
  • Posts: 31
  • Joined: 13 Aug 2020

Posted 19 October 2020 - 06:43 AM

I have a little bit of bonus data to share, that was not previously reported.  I captured a video recording with an 18mm lens and my Nikon D5600 during the transit.  I simply set it up on a tripod and let it go without any interference, while I was dealing with the main capture.  In the immediate aftermath of the event, I found the results with the 18mm lens underwhelming, although looking back at the data, there are some interesting aspects.  Although it is impossible to convey what it was like to be there, this wide field view documents the final moments before the transit.  This video begins as the ISS is exiting Earth's shadow.  You can see that it starts out quite dim after shadow exit, and then takes some time to increase in brightness.  In fact, in retrospect, I was lucky that the transit didn't occur any earlier than it did, or the ISS would have been underexposed.  

 

https://youtu.be/I2n-GOo3r-I

So many factors at play. Brilliant!



#85 dragracingdan

dragracingdan

    Viking 1

  • *****
  • Posts: 596
  • Joined: 21 Feb 2012

Posted 19 October 2020 - 08:33 AM

Awesome job and congrats! I also wonder how this type of work will continue without calsky

Best,
Dan

#86 tchelo

tchelo

    Sputnik

  • *****
  • Posts: 25
  • Joined: 04 Jun 2009

Posted 19 October 2020 - 09:04 AM

Simply stunning. Even caught Syrtis Major. Amazing feat....



#87 Tom Glenn

Tom Glenn

    Soyuz

  • -----
  • topic starter
  • Posts: 3,650
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 19 October 2020 - 03:03 PM

Thanks for the additional comments.  They are much appreciated.

 

 

I also wonder how this type of work will continue without calsky

Planetary transits were rare images to begin with.  With the discontinuation of Calsky, there are really only two ways this will move forward:

 

1) Some individuals have the necessary skills to calculate the trajectories themselves using the TLE orbital data that is publicly available.  However, I have yet to see this implemented in practice (everyone used Calsky), and people with the necessary skills often are not themselves planetary imagers.  But such individuals would now be the only ones able to capture planetary ISS transit images.

 

2) Somebody with the necessary skills will step forward and fill the void left by Calsky.  Websites such as transit-finder.com already do an equivalent job as Calsky did for solar and lunar transits, and it doesn't seem overly difficult to start including planets in the calculations.  But everything takes time, and therefore money, which is why Calsky ultimately failed.  


  • dswtan and dragracingdan like this

#88 Orion58

Orion58

    Apollo

  • -----
  • Posts: 1,178
  • Joined: 28 Oct 2011
  • Loc: Southern Wisconsin

Posted 02 November 2020 - 10:26 AM

Well done Tom.  Nice to see that all your planning and effort paid off.



#89 Tom Glenn

Tom Glenn

    Soyuz

  • -----
  • topic starter
  • Posts: 3,650
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 02 November 2020 - 11:58 PM

Well done Tom.  Nice to see that all your planning and effort paid off.

Thanks Bruce!  

 

Also, thanks to all of the many folks that have liked and commented here over the past many weeks.  I don't yet have any updates about Calsky replacements.  TLE data can be downloaded from a variety of sources.  Here are two (the second one requires you to create an account).

 

http://celestrak.com/NORAD/elements/

https://www.space-tr...cumentation#tle

 

If anyone out there with data analytics and computational programming skills wants to investigate (or already knows) how best to do this, let us know!  The general methods would require that the TLE data be converted into a series of orbital predictions, and then cross reference these with planetary ephemeris data, and calculate the position on the surface of Earth upon which the ISS would be casting a shadow from that planetary body.  



#90 Endymion

Endymion

    Mariner 2

  • -----
  • Posts: 226
  • Joined: 16 Jan 2016
  • Loc: Orange County, CA

Posted 04 November 2020 - 10:30 PM

Just Wow!

#91 Tom Glenn

Tom Glenn

    Soyuz

  • -----
  • topic starter
  • Posts: 3,650
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 11 November 2020 - 05:11 AM

Just a quick update on investigating alternatives to Calsky (also thanks for the comment above!).  For those just joining this conversation, in a strange twist of fate, the website Calsky.com (which was very useful for predicting planetary transits of the ISS, such as my Mars image) shut down just weeks after my image was published.  There are other resources available for predicting solar and lunar transits, but these don't include planetary predictions.  I found a program written by Ed Morana that does include planets.  This is available as a Java application below (also as an Android app, although I haven't used that):

 

http://pictures.ed-m...ions/index.html

 

The source code is also published.  This program has been around for a number of years, but never achieved the level of recognition as Calsky and others.  Getting it to work in Java Runtime Environment requires bypassing some security features, and so there are some annoyances there.  I contacted Ed, and he told me he hasn't updated the Java program in a while.  I've conducted some preliminary investigations about the accuracy of the program, and it works great, although the details involved here are beyond the scope of this post.  The short version is that you have to decide which TLE data you want to use, the two main sources being NASA and NORAD.  The program is based on the SGP4 model of simple perturbations, that have been in use for monitoring satellite orbits for many decades.  The catch here is that TLE data, which are used to define orbital state vectors, are associated with up to 1km error (in absolute xyz coordinates), which will always be reflected by up to several hundred meters of error in any predicted transit ground path.  Ed told me that he has no indication of which TLE data would be more accurate (NASA or NORAD) and that he frequently makes maps of each, and then splits the difference.  I did some retroactive studies on previous transits I have imaged, for which I have the "true" position of the ground path centerline (based upon the image).  It appears that splitting the difference between the two predictions is not a bad idea, although in some cases, one set of data is almost nearly perfect, and the other is ~500m in error.  So, in the end, each imaging attempt is a gamble.  Sometimes you win, and sometimes you lose.  

 

Ed's program gives you .kml files that you can drag and drop into Google Maps or Earth.  Shown below is a map drawn in Google Earth, depicting my Mars transit ground path from September 14, 2020.  Note that Ed's program doesn't let you set the date (for testing past transits), but I found a way to bypass this by changing the time and date on my computer.  Also, I had to download the historical TLE data corresponding to the epoch immediately prior to the transit on September 14, 2020.  In conclusion, planning for planetary transits of the ISS is still possible even without Calsky, but it now requires more work on your part.  The silver lining is that you have the potential to become much more aquatinted with the models used, and therefore can better understand sources of error.  For example, you can conduct numerous experiments using different TLE data and creating maps from each, which is especially interesting for comparison to an actual transit event that you have imaged.  

 

Google_Earth_map_Sept14_Mars_transit.jpg


  • John Boudreau and dragracingdan like this

#92 Borodog

Borodog

    Mercury-Atlas

  • *****
  • Posts: 2,819
  • Joined: 26 Oct 2020

Posted 11 November 2020 - 10:08 AM

That is awesome.



#93 BillHarris

BillHarris

    Viking 1

  • -----
  • Posts: 516
  • Joined: 29 Nov 2017
  • Loc: northwest Alabama

Posted 12 November 2020 - 07:31 PM

Personal anecdote here: in 1967-1968, during the last year of the Echo2 aluminized Mylar passive communication satellite, I got the idea of trying to observe a transit of Echo across the Moon. This was in the pre-personal computer era and the idea of predicting this event was poo-pooed. I tried to observe it, anyway. I regularly timed passages of Echo and could guesstimate where it would pass the next time around, and if it could be near the Moon. I spent a lot of time rapidly-deploying my 6" f/8 Newt. I think the closest I ever got to a Lunar transit was within a degree or two before the satellite re-entered.
I had the notion of seeing the dark balloon silhouetted against the Moon with a bright specular reflection of the Sun. This was an exaggeration since the satellite would only systems 7-8 arc".
Oh well.

#94 BillHarris

BillHarris

    Viking 1

  • -----
  • Posts: 516
  • Joined: 29 Nov 2017
  • Loc: northwest Alabama

Posted 12 November 2020 - 07:32 PM

At any rate, Tom, you did quite an achievement.
Congrats!

#95 Tom Glenn

Tom Glenn

    Soyuz

  • -----
  • topic starter
  • Posts: 3,650
  • Joined: 07 Feb 2018
  • Loc: San Diego, CA

Posted 12 November 2020 - 09:44 PM

Personal anecdote here: in 1967-1968, during the last year of the Echo2 aluminized Mylar passive communication satellite, I got the idea of trying to observe a transit of Echo across the Moon. This was in the pre-personal computer era and the idea of predicting this event was poo-pooed. I tried to observe it, anyway. I regularly timed passages of Echo and could guesstimate where it would pass the next time around, and if it could be near the Moon. I spent a lot of time rapidly-deploying my 6" f/8 Newt. I think the closest I ever got to a Lunar transit was within a degree or two before the satellite re-entered.
I had the notion of seeing the dark balloon silhouetted against the Moon with a bright specular reflection of the Sun. This was an exaggeration since the satellite would only systems 7-8 arc".
Oh well.

Bill, thanks for the anecdote.  You are probably very familiar with the history of orbital predictions, although most readers are probably not, and I only recently have been reading about this topic.  The SGP4 propagator dates back to 1965 with the work of Max Lane, who had the goal of developing a better model to predict the trajectories of high-drag satellites in low-Earth orbit.  This work led to the development of the TLE format (two-line element), which consisted of two simple lines of text, originally designed for punch cards, that contained all the information necessary to generate short term orbital predictions.  This work led to the publication of a 1979 paper, Spacetrack Report #2, and subsequently to the publication of a FORTRAN code for the model in Spacetrack Report #3 in 1980.  An updated paper has been published to include example codes in a variety of programming languages.  NORAD monitors thousands of satellites, and publicly distributes TLE data for non-classified satellites, primarily for the purpose of research and safety in spaceflight, and many companies use TLE data to monitor their satellites.  It is also useful as a first pass analysis for debris and collision avoidance, although secondary sets of data must be used for more precise measurements.  As a side effect to all of this, the amateur imaging community benefits from the data, because we get fairly accurate orbital predictions.


  • BillHarris likes this

#96 wargrafix

wargrafix

    Fly Me to the Moon

  • *****
  • Posts: 5,446
  • Joined: 10 Apr 2013
  • Loc: Trinidad

Posted 14 November 2020 - 04:25 AM

I use that program religiously


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics