ISS Transits Orion's Belt - Forums

Topic starter

Nov 8, 2021 · Edited: Nov 8, 2021

Hi all. I had a fun and somewhat fluky observation the other morning (November 7, 2021). I just happened to look out my front window at 6:30 (EST) in the morning and noticed a bright white light moving across the sky. I recognized it right away as the ISS being illuminated by the rising sun. What happened next was pretty cool and a little unexpected.

The constellation Orion was still just barely visible as the ISS moved across the sky. I watched with curiosity as the space station moved towards Orion and headed almost exactly straight through its belt. I couldn’t believe my lucky timing and was excited to double check my observation afterwards.

Looking at the attached sky chart you can see the ISS entering Orion’s Belt exactly over Mintaka and exiting 8 seconds later almost directly over Alnitak. A few minutes earlier and I suspect the the sun wouldn’t have risen enough to so brightly illuminate the ISS and a few minutes later it would have risen more than enough to completely overpower the light of Orion.

I wish that I had my camera ready to go but unfortunately this one will have to remain an observation only.

Just curious… was this just a lucky coincidence of events or is an ISS transit of Orion’s Belt something that can be predicted? If so, is there an easy way to figure out how often this might occur and when the next time might be?

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Aidan Thiessen

Nov 8, 2021

Not sure if there is an easy way but you can use stellarium and see the ISS' future locations in the sky. Then just use the date and time options to scroll through hours and minutes. From my location, this transit will happen again on November 10th at 5:22:53 am (MTN), except it will be less than a degree from M42. Could be a great opportunity for some interesting photos

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Steven

Nov 9, 2021 · Edited: Nov 9, 2021

Usually I only look at the transits for the moon/sun. and there are websites dedicated for that. And is "easy" to predict. Down to the second even.. here is the website for; Transit finder Not sure if there are calculators for transits for specific targets like Orion or others.

I do know that the app "Clear outside" will show a little satellite icon every time the ISS is in the sky on your location.
It will show the starting times, angles, magnitudes, etc..
So, I guess you could:

- take those times,
- go into Stellarium.
- Set the clock to that time/date, and see where the ISS is and see if it passes in front of something interesting.
- It is then possible to pick a target, and take the coordinates from Stellarium,
- plot them into your go-to mount, keep it pointed at those coordinates or at that target.
- And at the exact time ISS would pass in your frame, you start shooting.

This works quite well, and I have done it before.. when I didn't want to wait for a moon transit to shoot the ISS.

One problem though, to get the ISS in frame, at the speed that it's going, you're probably shooting at 1/1600th of a second, if not faster.
At such a shutter speed I very much doubt you can see anything of Orion or even any stars in the background.
So these shots are more interesting if there is a moon or solar transit, as those are the only objects bright enough to show detail + the ISS. Most other images will just be the ISS in a black background.

Obviously this is less of a worry if you're going for a longer exposure to get the trail/movement of the ISS in frame, not just the ISS itself.

here is my moon-transit attempt.
Still waiting patiently for another good transit to try it again!

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bluespeck

Topic starter

Nov 9, 2021

Aidan Thiessen:
Not sure if there is an easy way but you can use stellarium and see the ISS' future locations in the sky. Then just use the date and time options to scroll through hours and minutes. From my location, this transit will happen again on November 10th at 5:22:53 am (MTN), except it will be less than a degree from M42. Could be a great opportunity for some interesting photos

Thanks Aidan. Yes, the ISS through M42 would be pretty cool indeed but would be difficult to capture in one shot (along with any nebulosity). You would probably need to capture the ISS at a really fast shutter speed (e.g, + 1/1000) and of course M42 would need much more time to register enough light. I suspect that it would need to be done in a carefully orchestrated composite, but would no doubt be a lot of fun to try. Please let me know if you do... I'd love to see it.

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bluespeck

Topic starter

Nov 9, 2021

Usually I only look at the transits for the moon/sun. and there are websites dedicated for that. And is "easy" to predict. Down to the second even.. here is the website for; Transit finder Not sure if there are calculators for transits for specific targets like Orion or others.

I do know that the app "Clear outside" will show a little satellite icon every time the ISS is in the sky on your location.
It will show the starting times, angles, magnitudes, etc..
So, I guess you could:

- take those times,
- go into Stellarium.
- Set the clock to that time/date, and see where the ISS is and see if it passes in front of something interesting.
- It is then possible to pick a target, and take the coordinates from Stellarium,
- plot them into your go-to mount, keep it pointed at those coordinates or at that target.
- And at the exact time ISS would pass in your frame, you start shooting.

This works quite well, and I have done it before.. when I didn't want to wait for a moon transit to shoot the ISS.

One problem though, to get the ISS in frame, at the speed that it's going, you're probably shooting at 1/1600th of a second, if not faster.
At such a shutter speed I very much doubt you can see anything of Orion or even any stars in the background.
So these shots are more interesting if there is a moon or solar transit, as those are the only objects bright enough to show detail + the ISS. Most other images will just be the ISS in a black background.

Obviously this is less of a worry if you're going for a longer exposure to get the trail/movement of the ISS in frame, not just the ISS itself.

here is my moon-transit attempt.
Still waiting patiently for another good transit to try it again!

Thanks Steven. Great shot of the ISS transiting the moon. Pretty cool! Thank you also for the links and additional information. Under the right condition, if one could plans things carefully enough I suppose that one could fire off a few quick bursts at 1/1600 of a second to capture the ISS and then immediately go to a greater number of longer exposures to capture the nebulosity or Orion. Does this make sense? (I have been experimenting with N.I.N.A. for data acquisition and think that it might work for this type of session.) It is probably a little too ambitious for my current level of skill, but is definitely something I might try down the road.

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Steven

Nov 9, 2021

Well, yes.. you can shoot M42 normally with long exposures, and shoot the transit of the ISS in short exposures, and composite the ISS into the final long exposure shot in photoshop after.

But, you might run into one problem. In order to composite things "properly" you will want to have a few reference points in order to line up and composite the ISS where it really was at that time.. obviously you can just plop any picture of the ISS anywhere in the frame and call it finished. But... the challenge comes from doing it "for real"

So you would need to line up some stars and such to do that. But, you might not get enough star data in the short exposure to align things with the long exposures... I mean.. something like 1/1600th, makes space pretty darn dark, and might be too short to get any visible stars in the image. You might want to experiment with that one. (I checked my raw file of the transit, and even if I crank up the exposure, I'm not really seeing any stars... granted.. I shot the moon.. at lower ISO and such..it might still be doable with different settings)

My advice; next time you're shooting M42, try to see how fast you can do an exposure and still have some stars in the frame (even at higher gain/iso).. you might need to temporarily up the exposure of the frame in photoshop, and if you can still see 3 or more stars in fast exposure? this could work for sure! next is just luck and timing!

I will say that Orion is probably the best target to try this with, as it's incredibly bright and has some good bright stars that could be good reference points, so this might allow you to have enough reference points in the short exposures, to line things up properly.

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bluespeck

Topic starter

Nov 9, 2021

Well, yes.. you can shoot M42 normally with long exposures, and shoot the transit of the ISS in short exposures, and composite the ISS into the final long exposure shot in photoshop after.

But, you might run into one problem. In order to composite things "properly" you will want to have a few reference points in order to line up and composite the ISS where it really was at that time.. obviously you can just plop any picture of the ISS anywhere in the frame and call it finished. But... the challenge comes from doing it "for real"

So you would need to line up some stars and such to do that. But, you might not get enough star data in the short exposure to align things with the long exposures... I mean.. something like 1/1600th, makes space pretty darn dark, and might be too short to get any visible stars in the image. You might want to experiment with that one. (I checked my raw file of the transit, and even if I crank up the exposure, I'm not really seeing any stars... granted.. I shot the moon.. at lower ISO and such..it might still be doable with different settings)

My advice; next time you're shooting M42, try to see how fast you can do an exposure and still have some stars in the frame (even at higher gain/iso).. you might need to temporarily up the exposure of the frame in photoshop, and if you can still see 3 or more stars in fast exposure? this could work for sure! next is just luck and timing!

I will say that Orion is probably the best target to try this with, as it's incredibly bright and has some good bright stars that could be good reference points, so this might allow you to have enough reference points in the short exposures, to line things up properly.

Thanks