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08-03-2016, 05:51 PM   #1
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Astro Tracking, First Attempt.

I was camping over the weekend and had a nice clear starry night, so i thought I'd give astro photography a shot!

5324 was 121.0 secs at f3.5 100 iso, no star trails. I had to increase exposure by 2 stops in LR.

5325 was 208 secs same settings, both at 18mm, again added 2 stops in LR. Both had white balance adjustments, noise reduction and sharpening. I found star trails in the second shot, so Astro Tracking has it's limits.

I'm fairly pleased for a first attempt, but any advise would be welcome.

Tuggie76


Last edited by tuggie76; 12-02-2016 at 06:55 AM.
08-03-2016, 06:25 PM   #2
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The main issue here is that both shots are out of focus. You'll have to set the focus manually (either through trial-and-error, or using live view magnification) and once it's right, you can begin shooting your star trails.

Apart from that, it looks like the astrotracer is working fine. 60-120s is where I'd expect it to give you the best results.

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08-03-2016, 08:19 PM   #3
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QuoteOriginally posted by tuggie76 Quote
I was camping over the weekend and had a nice clear starry night, so i thought I'd give astro photography a shot!

5324 was 121.0 secs at f3.5 100 iso, no star trails. I had to increase exposure by 2 stops in LR.

5325 was 208 secs same settings, both at 18mm, again added 2 stops in LR. Both had white balance adjustments, noise reduction and sharpening. I found star trails in the second shot, so Astro Tracking has it's limits.

I'm fairly pleased for a first attempt, but any advise would be welcome.

Tuggie76
Hi Tuggie76,

When I started out trying to do astrophotography I soon discovered that getting the focus right was surprisingly difficult and quite frustrating. I think tethering is the gold standard but using a lens with a distance window or markings so you can manually set the focus to infinity helps simplify things enormously (see below). I use an O-GPS1 on my K3 and find the astrotracing function works very well for exposure values in the range Adam mentioned above, I also found the calibration procedure to be a bit fiddly to start with.
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08-03-2016, 09:46 PM   #4
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Hi Tuggie - I have a couple of suggestions....
  • Focus - I have absolutely no patience for 20 to 30 minutes of trying to focus, so I cheat. The motto "Tape is your Friend'. While it's still light out in the afternoon, early evening - I go focus (auto focus using live view so that there is no chance of front/back focusing error or manual focus - depending on the lens) on something as far away as possible (a mile away, ridge line - really whatever). Then put the camera into manual focus, and use some gaffers tape to tape down the focus ring so that it doesn't move. You are all set.
  • ISO - I would boost it up from ISO 100 to at least ISO 800 or 1600 in order to gather more light. That will pull in more stars.
  • Exposure Time - I would go for 60 seconds. This will limit the amount of tracking errors that results in star trailing in the corners.



08-03-2016, 09:53 PM   #5
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It's a good start. So, you're on the right track.

One of the things you must consider is the position to the sky. To the Polar star, the movement is very small, but increase very much to the Ecliptic, at 90 degrees of the pole. So, the performance can differ.

IMO, your images present some small movement, even the short one, of 125s. Probably, 18mm is to much for such a long time. Try 80s, or 60s, and rise the ISO to 400 and even much more, depending of your camera.

I don't know if you had used a cable, or a remote to take the shot, but is better this way. Even better is to use mirror lock-up, to take night shots.
08-04-2016, 06:19 AM   #6
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Thanks for the feedback guys. I did have a lot of trouble trying to focus, it's not easy in the dark, on your knees trying to look through the viewfinder or at the screen - especially when balanced on a ledge over the lake! The pre-focus tips are well noted! I did expect to be able to set the lens at infinity, but it just kept turning, no stop.

I'm kinda hooked now, but living in the city it's tough to get somewhere dark enough, we were camping in northern Ontario for the weeekend, the other nights were over cast.

Tuggie76
08-04-2016, 06:53 AM   #7
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The best way for manual focus on a starry night:
Live View then select Ok for a 10x Zoom. Then i select a bright star, and adjust focus on it.

I use it for my astrophotography session like my last: https://www.pentaxforums.com/forums/172-pentax-k-3/242797-k-3-astrophotograph...ml#post3722402
08-04-2016, 08:19 AM   #8
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QuoteOriginally posted by tuggie76 Quote
Thanks for the feedback guys. I did have a lot of trouble trying to focus, it's not easy in the dark, on your knees trying to look through the viewfinder or at the screen - especially when balanced on a ledge over the lake! The pre-focus tips are well noted! I did expect to be able to set the lens at infinity, but it just kept turning, no stop.

I'm kinda hooked now, but living in the city it's tough to get somewhere dark enough, we were camping in northern Ontario for the weeekend, the other nights were over cast.

Tuggie76
If your light pollution at home is mostly from sodium lamps (orange/yellow) you might like to try one of these: Hoya 58mm Enhancing (Intensifier) Glass Filter S-58INTENS B&H.

N

08-04-2016, 01:10 PM   #9
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Thanks again, I'll try some night focusing and look into the filter, will I be able to use it in my back yard?

Tuggie76
08-04-2016, 01:44 PM   #10
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QuoteOriginally posted by tuggie76 Quote
Thanks again, I'll try some night focusing and look into the filter, will I be able to use it in my back yard?

Tuggie76
Probably but it will all depend on the intensity and type of light pollution you suffer from. Astronomers are always messing with the colours of their images, so if it is is okay for NASA or ESA then I wouldn't worry too much.
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