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05-28-2017, 10:20 PM   #1
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Layering of ISS pass
Lens: Sigma 18-125 DC HSM Camera: K-70 Photo Location: Tom Price, WA ISO: 800 Shutter Speed: Above 6s Aperture: F5.6 

hello all. Still new to night photography, this is really only my second attempt. There was a good ISS pass this morning, beginning 1 hr before local sunrise, coming in from the NNW and peaking at 68 degrees, so a good chance to get a long streak. I had previously tried an Interval Composite, with no success, so decided to try a conventional interval and stack the results in PS. Something else i am new to. From my one previous experience, I knew the camera would do 25 sec exposures at 5 sec intervals, so i just assumed it would do 30 sec exposures at 2 second ( the minimum) interval. Carefully set up, did a couple of test exposures @ 30 secs just before the pass, settled on Is-SO 800 and F5.6. I started the sequence just as it came into view, it did 2 exposures then got a message of Interval Sequence Complete. WT? Quickly started again, same result, and again, to cover the pass. So it is a bit gappy.
When I layered the six exposures the result was as below, after doing some corrections in LR first, and syncing al the changes..



Obviously over-exposed, I should have made the adjustments on the last shot, and synced backwards. So I tried this but not much change. But what is the odd effect around the larger stars, lower in thee more exposed art of the finished composition? They look like dimples-- part of the layering? The layering hasn't worked for the stars, giving that stuttering look. After some adjustment.



Still not good, the only way I could be rid of it was to darken it overall, as below.



So now the stars simply look like I have had camera shake.

The last shot is one of the interval pictures.


So my next attempt in two days time will be a Bulb shot. At least I will have star tracks rather than stutter. My IR remote has chosen a bad time to fail so I will be using the Ricoh Image Capture app on my phone to trigger Bulb. After 30 secs @ F5.6 and ISO 800 gave me a fairly good exposure, and this pass will be across the western sky at the same time, I will be trying 420secs at F.8 and ISO 200. Do my maths add up?

05-29-2017, 12:45 AM   #2
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QuoteOriginally posted by ranmar850 Quote
Carefully set up, did a couple of test exposures @ 30 secs just before the pass, settled on Is-SO 800 and F5.6. I started the sequence just as it came into view, it did 2 exposures then got a message of Interval Sequence Complete. WT?
You would need to make the interval 32 s, otherwise the camera will just think it's done immediately following the first shot.

I'd recommend trying starstax. Might help you get better alignment, too.

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05-29-2017, 01:19 AM   #3
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No, I don't think that is the case--otherwise, how could I have taken hundreds the night of the Eta Aquarids shower, all on a 25 sec exposure and five second interval? But here is the really odd thing, and it must be down to software--if I try to replicate the 25 sec exp/5 sec interval at ISO 800 on my desk with the lens cap on, it does 4 exposures and says it's done. If I do the same thing with ISO 3200 selected, it will shoot either 20 exposures no problems, or only shoot 2?
05-29-2017, 05:12 AM   #4
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For taking multiple sequential shots, I find it easier to just hold down the shutter button. You could probably rig something up with a metal nut and a rubber band to physically hold it down (so you keep your hands off the camera). Your k-70 also has a cable release port, the pinout diagram is in the link below. You just need the male jack part, and you can build something to short out the correct pins easily enough (or get fancy and include a switch):

About the wired remote control. - PentaxForums.com

05-29-2017, 05:42 PM   #5
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Yes, I've read you can cable release via the Mike port. I'll investigate making my own. The exposure test this morning worked out close--did 245 secs @ F.8/iso200. As I won't be getting the whole visible pass across an 18mm lens, i will bring the time down a bit, and open up the aperture a bit more. Ricoh Image capture app worked OK for shutter operation on Bulb. It will only release the shutter for single frame shooting, but has some functionality which might be useful.
05-30-2017, 05:47 PM   #6
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Just shoot high speed continuous with a wired remote connected. Stack in star-stacks, fill in the few caps. My 2 cents.
05-30-2017, 06:28 PM   #7
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Not quite following you. Understand the wired remote, but are we talking very short exposures at a high ISO with no interruption between? ideal would be to get the entire track, erase all the background, then layer it onto a good single exposure star background with no streaking?

06-20-2017, 03:58 PM   #8
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QuoteOriginally posted by ranmar850 Quote
Not quite following you. Understand the wired remote, but are we talking very short exposures at a high ISO with no interruption between? ideal would be to get the entire track, erase all the background, then layer it onto a good single exposure star background with no streaking?
Sorry, been gone for a while. Set the exposure time for more or less correct exposure, could be 5 to 20 seconds or so. Shoot high speed continuous to minimize the shutter/mirror cycle time to reduce caps between images. Stack in star-stax and fill in the small caps in Photoshop.
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06-20-2017, 05:15 PM - 1 Like   #9
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I've done a bit more since then, filmed three passes using Bulb for shutter control. The first was done with the Ricoh smartphone remote, then I made a wired remote with information from this forum. This is the most recent , from yesterday morning. ISO 200, f4 and 131 sec exposure.




I messed up the composition, IMO, by making a pan move between the test shot, below, and the pass shot.




This was a 123 sec exposure, and I didn't realise I'd captured a passing aircraft until PP. There was also a Milky Way shot done just before this, I've posted in the Post Your Photos thread this morning.
06-21-2017, 03:39 AM   #10
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Nice results! I have too much light pollution to expose much longer than about 20 seconds per frame.
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