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02-19-2018, 02:40 PM   #1
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Showstopper level issue with star trail stacking

I tried some star trail stacking tonight with KP by using 30 second exposures and in-camera interval shooting set to minimum delay. This causes 5 second gaps between exposures and makes the stacked trail look like Swiss Cheese. I have all filters and noise reductions disabled and nothing seems to help. This does not happen with shortish exposures like 5-10 second per photo.

So, for astrophotography stacking purposes, Verdict 0/5.

02-19-2018, 02:45 PM   #2
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I assume the delay is due to long exposure noise processing... Have you deselected it, or is there even an option to allow that? I'm sure others with specific experience will be able to confirm or refute this. I trust you've asked about this, and checked that it's not a similar issue on other cameras, before giving a "0/5" score? You know for a fact that you're not doing something incorrect, or haven't understood something about operation of the camera?

Last edited by BigMackCam; 02-19-2018 at 02:51 PM.
02-19-2018, 02:55 PM - 1 Like   #3
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QuoteOriginally posted by MJKoski Quote
I tried some star trail stacking tonight with KP by using 30 second exposures and in-camera interval shooting set to minimum delay. This causes 5 second gaps between exposures and makes the stacked trail look like Swiss Cheese. I have all filters and noise reductions disabled and nothing seems to help. This does not happen with shortish exposures like 5-10 second per photo.

So, for astrophotography stacking purposes, Verdict 0/5.
Sounds like a configuration issue. Definitely disable the noise reduction and set the interval equal to the shutter speed + 1 second.

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02-19-2018, 02:55 PM   #4
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Another note to add, the KP has an interval composite mode, so it can do the stack for you automatically.


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02-19-2018, 03:34 PM   #5
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I assume you’re talking about the Star Stream mode right? Because on my K-1 I can only set a „minimum“ delay in that mode. The normal interval mode only has an interval time setting. I just tried using Star Stream mode with 30 seconds exposure and delay set to minimum and the delay time is about a second on my K-1. So I guess there is still some in camera corrections enabled that cause the five second delay.

I haven’t used the Star Stream mode but I did two startrail photos with interval mode (see my 500px link below). I took 100 pictures with 30 second exposure and used Starstax to blend them together. But I had to find out that the interval needs to be set to 33 seconds because the camera actually exposes for 32 seconds when set to 30 seconds. As described in this thread: https://www.pentaxforums.com/forums/173-general-photography/359667-actual-sh...rd-values.html

Last edited by alpheios; 02-19-2018 at 03:52 PM.
02-20-2018, 12:21 AM   #6
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This is not configuration issue. As I said everything is disabled what comes to delays and noise reductions AND *shorter exposures fire instantly* one after another with interval timer. In KP you can configure it so that you set only the amount of exposures and use "Minimum" as delay between the exposures (instant with shorter exposure time).

Same thing happens when manually using single or continuous shooting modes, camera stalls after 30 second exposures.

Did not happen with K-1. Never. And I do know how to set up my camera for everything I do with it.
02-21-2018, 09:20 AM   #7
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When you say it fires faster at shorter shutter speeds, have you tried 25s? I know its might not be ideal, but that doesn't seem like that much of a tradeoff if you're stacking later anyway.

I'm don't have a KP or I'd try it myself, but is there any difference in delay between 5s or 25s exposures? If there is it might suggest some background processing involved that relates to exposure time. If there is no difference at any speed other than 30s I would guess it's a software glitch or designed delay. It might be to let the sensor cool slightly and completely discharge before each exposure since 30s is the longest exposure available and implies people want the most sensitivity the sensor can get.
02-21-2018, 10:17 AM   #8
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Okay, I found the limit which is 15 seconds. After 15 second exposure camera is instantly ready for another exposure. When set to 20 seconds it begins to stall for ~3 seconds until another exposure can be made. I really hope K-1 MK2 does not do this...I preordered it already. This looks like spatial filtering Sony does with their MILC offerings and there the limit is 3.2 second. Difference is that their bodies do not "freeze" after long exposures. All signs look like K-1 mk2 has this "enhancement" as they suddenly upped the ISO range and speak about some accelerator chip.

There is a bubble-gum fix for this - remote interval release and bulb-timer in-camera which cuts the holes in trails somewhat. One can for example take 30x2min exposures instead of 120x30 second exposures for 1 hour trails.


Last edited by MJKoski; 02-21-2018 at 10:23 AM.
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