[ranmar850]

I do quite a few ISS pass captures. usually a case of trying to get it all, or as much as practicable, of the pass in one Bulb exposure. These can be as long as 4 minutes, which brings in obvious problems . And, as the best visible passes are not too long after sunset , exposures can get muddy--also, there is always star streaking. So I decided on a different approach--I am also keen on pano stitches so why not try to combine the two. This will involve careful setup, and panning it just right to a) get enough overlap for a good pano stitch, and b) getting a continuous exposure on the pass.
So I looked at how long the pass would take (6min 30 sec) , how much of the compass it would cover (157 deg) , and how much it would transit per minute.
So I settled on 20 second exposures, and started exposing 20 seconds before the scheduled visibilty time. I panned slightly between exposures, keeping it in frame, quick look at the preview confirmed it. I thought I had nailed it, but, on stitching the pano in PS ( via Lightroom) I came up with the below result.
My question to the assembled brains trust is this--Do I need to have longer exposures, to get more coverage in each frame, or less, and man more often?

[DeadJohn]

I think panning overly complicates things. For the ISS you want as little time as possible between consecutive exposures.

ISS passes usually occur during twilight so the background will get blown out with too long of an exposure. I take multiple consecutive exposures, minimum time between exposures.

For processing, I load each frame as a Photoshop layer, pick one good frame as the main image, then stack the other layers in "lighten" mode.

That will by default give you star trailing plus the entire ISS pass. Of you don't want star trails and just have stars from a single photo, crudely mask each of the lighten layers by selecting a buffer around the ISS.

[ranmar850]

That's an approach I tried early on, but ended up with gaps--my problem was too long between exposures. IIRC, I was doing 30 sec exposures with a remote, so there were slight gaps. Assuming you would do Interval with Minumum Time selected between exposures? I'd like to see some of your results, if you don't mind posting them?

This was the first time I tried shooting multiple frames and doing layering --big gaps as well as multiple stars.






The one below is layered, using the alternative method you outlined above--background short exposure as a layer, then remove the stars from the ISS pass long exposure.





Capturing a shorter portion of the pass will give less star streaking, obviously.

[MossyRocks]

I would almost think that the correct method would be to shoot things separately and combine in post. As in shoot the foreground at what ever is needed to get that right, shoot the night sky to get that right and then shoot the ISS transit. I don't know how long was between each shot of what you used for for creating the pano but maybe trying blending brightest or manually adjusting the layer mask in photoshop if that was used.

[photoptimist]

Cool project!

Unfortunately, the gaps are not avoidable because you or the camera always take non-zero time to store one shot and set-up the next shot. (The ISS waits for no man or camera!)

One solution is to tile or stack images using two cameras. While one camera is taking a shot, you are reorienting the other camera for it's next shot (if you need to do that to pan across the full track). You could set both cameras to 20 second exposure time with 35 seconds between triggers (15 seconds between shot end and start of the next shot). Start one camera 15 seconds after starting the other camera and the successive frames will include 5 seconds of ISS trail overlap. Each time you hear a camera close the shutter, you have about 15 seconds to reposition it for the next frame (if needed).

[ranmar850]

Thanksfor all the replies. I tried again last night--the pass was west to south this time, meaning the sky, at 7.30 pm local was dark, but will still show a bit brown on onger exposures. I tried the interval shooting method firrst suggested by DeadJohn, and creating a layer mask. I used the excellent Interval function of the K-x, set to Minimum interval, 15 second exposures. I ended up with 13 frames, including the clear one I wanted for background. I did one composition using all frames complete, so i had star streaking. The pass crossed the Milky Way. Some clone stamping was necsssary to fill the gaps in the ISS track.




I then took that image and made it into a Layer mask, blacking out all but the track. I really struggle with layers in PS, having not used it much and at widely spaced intervals. The only way i can get it to work is to have the images in LR, select Edit>Open as layers in PS. After much tutorial watching, I ended up with the result below.





I think I can do better, the background layer needs more ( or less?) work in PP, still looks muddy and cluttered.



I then did a

[MossyRocks]

Nice job. I love learning how things are done and seeing how people approach different problems. As always the more practice you do the better the results.

[MarkJerling]

Thanksfor all the replies. I tried again last night--the pass was west to south this time, meaning the sky, at 7.30 pm local was dark, but will still show a bit brown on onger exposures. I tried the interval shooting method firrst suggested by DeadJohn, and creating a layer mask. I used the excellent Interval function of the K-x, set to Minimum interval, 15 second exposures. I ended up with 13 frames, including the clear one I wanted for background. I did one composition using all frames complete, so i had star streaking. The pass crossed the Milky Way. Some clone stamping was necsssary to fill the gaps in the ISS track.




I then took that image and made it into a Layer mask, blacking out all but the track. I really struggle with layers in PS, having not used it much and at widely spaced intervals. The only way i can get it to work is to have the images in LR, select Edit>Open as layers in PS. After much tutorial watching, I ended up with the result below.





I think I can do better, the background layer needs more ( or less?) work in PP, still looks muddy and cluttered.



I then did a

That looks lovely!

[DeadJohn]

Those 2 newest photos worked well. The versions with star trails and with frozen stars both look good.