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10-23-2014, 10:00 PM   #1
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First attempt at star trails, failed. Need suggestions?

Hey everyone,
Recently decided to try out some star trails for the first time, so I set up my DSLR (K-3) with the following settings:

Exposure time: 30s

f/5.6

ISO: 400

I set the K-3 to "Interval Shooting" with interval speed at 2" and the amount of shots at 500.

If I did the math correctly, I should have been out for 250 minutes with yes, 500 photos of the stars...

Unfortunately, the clouds decided to roll in, but I managed to capture a few minutes of time without the stars being covered.

Here's what the photo turned out like:



Excuse it for being up close, but prior to zooming in, it appeared to have gaps in the trail which were very noticeable.
Also, as the photos were being shot, I noticed that after each 30 second exposure, the amount of shots left
starting from 500 were decreasing by ~15 shots after that photo was taken. With that math, if I was able to stay out longer,
It would've only got me 33 shots to work with.

So, here's my question:
Why are these gaps appearing in my trails (Also excuse me for bumping into the camera once whilst shooting, it moved the position of the brighter star)
and what settings should I adjust to fix it? Also, how can I adjust the "Interval Shooting" setting to actually capture 500 images with the listed settings instead of
~30?

Cheers,
Alex

10-23-2014, 10:59 PM   #2
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That looks like camera shake. Make sure your tripod is sturdy (refrain from walking close by when the camera is capturing images) and that SR is disabled.

As for the settings issue, I can't help you off the top of my head, but I seem to recall that way the camera works in interval mode is a little counter-intuitive, so double-check with the manual.

Adam
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10-24-2014, 12:25 AM   #3
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QuoteOriginally posted by Adam Quote
As for the settings issue, I can't help you off the top of my head, but I seem to recall that way the camera works in interval mode is a little counter-intuitive, so double-check with the manual.
Indeed so (and unfortunately, the manual isn't too clear on this issue). Anyway, the interval count-down starts when the exposure begins and not when the exposure ends. Therefore, with an exposure time of 30 sec. the interval should be set to some 32-33 sec.

I have yet to try it myself, but for star trails shooting with a K-3 one could also consider 'multi exposure+continuous' (requires a remote release) together with the "bright parts only" composite mode.
10-24-2014, 02:21 AM   #4
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I managed this image with the K5 and an elastic band, camera set to continuous shooting 30 second exposure elastic band on shutter release (with a small ball of paper) and just let it go, then stack images in pp. I found the interval timer too difficult to get right though there is a post on here somewhere telling you the best intervals to set to minimize "down time" between frames.

Mike

---------- Post added 10-24-2014 at 05:33 PM ----------

Found the thread I was talking about

https://www.pentaxforums.com/forums/115-pentax-k-5/143409-k-5-astrophotography.html

Mike

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10-24-2014, 04:42 AM   #5
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The gaps are from too long of an interval between shots. The settings I use with my k-30 and 18-55 kit lens are : F4, 15 sec, ISO 1000-2000, and the interval set at about 18sec. These settings are a base point I start with and adjust depending on the amount of Moonlight and other factors. I go one stop up from what ever the lowest Fstop is for the lens I'm using, and it helps eliminate coma/fringing from the stars. The interval time needs to be your exp. time plus what ever the amount of time you want between shots, but it's a little tricky getting it just right (at least with my K-30 it is) Too long and you get gaps when you stack them. You just need to try a few shots & adjust the time till you find what you want. Also I don't know what lens you are using, but at ISO400 you are missing a lot of the faint stars and with the K-3, you don't need to worry about noise, so go much higher, even 3600 or higher depending on how dark the sky and ambient light is.


Here's a good article on lens selection and settings : How-To: Picking a Great Lens for Milky Way Photography


This was 200 shots at the above settings stacked in Startrails



Last edited by Kendigitize; 10-24-2014 at 08:15 AM.
10-24-2014, 05:14 AM   #6
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2" is too short. The interval setting is the time between shutter presses, not the delay between the end of one shot to the start of another. Try 31 with a 30 second shutter, and if you get long gaps from skipped shots increase to 32 or 33.

The sample image looks like the tripod moved a few times.
10-24-2014, 02:11 PM   #7
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Thanks for all of the replies! I'll take all advice and apply them next time when the skies are clear. Not the best weather in Washington right now
10-27-2014, 09:21 AM   #8
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QuoteOriginally posted by DeadJohn Quote
2" is too short. The interval setting is the time between shutter presses, not the delay between the end of one shot to the start of another. Try 31 with a 30 second shutter, and if you get long gaps from skipped shots increase to 32 or 33..

This is what I was going to say. This would also explain why the number of shots would decrease by 15 after each exposure.

10-27-2014, 02:39 PM   #9
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QuoteOriginally posted by mike_perth Quote
I managed this image with the K5 and an elastic band, camera set to continuous shooting 30 second exposure elastic band on shutter release (with a small ball of paper) and just let it go, then stack images in pp.
A cable release locked on will achieve the same result (if you have one).
This is the technique I use as well.
10-27-2014, 02:47 PM   #10
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I did this one last week. It's 150x20s exposures with a 22s interval time set. 2s on the K-3 seems to be enough time to write the raw file and be ready for the next shot. Shooting jpeg you may be able to just add just 1s (test first). I did some light painting too. Fun evening even though I didn't get any good meteor shots which was my mission that night.

10-27-2014, 03:51 PM   #11
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QuoteOriginally posted by mattb123 Quote
I did this one last week. Fun evening even though I didn't get any good meteor shots which was my mission that night.
The Orionids turned out to be a very week showing the peak night of the 21st, according to official sources. I only saw a few that night and expected many more. Nice Photo!
What lens did you use for that shot? I just ordered the Rokinon 18mm F2 and can't wait.

Last edited by Kendigitize; 10-28-2014 at 12:41 PM.
04-15-2015, 01:10 PM   #12
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QuoteOriginally posted by Kendigitize Quote
The Orionids turned out to be a very week showing the peak night of the 21st, according to official sources. I only saw a few that night and expected many more. Nice Photo!
What lens did you use for that shot? I just ordered the Rokinon 18mm F2 and can't wait.
Whoops, I didn't see this when you posted it.
That was with a DA* 16-50 at 16mm
04-15-2015, 01:47 PM   #13
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Ensure that the high ISO and long exposure compensation is turned off when doing star trails.
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