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06-26-2016, 10:04 PM   #1
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Optimal Astrotracer Conditions

I'm having a hard time seeing any differences with astrotracer, even though I think I'm doing it correctly - astrotracer on, gps on (green), calibration ok, 17-35 mm lens, f3.5, 30 sec, iso 1600, manual focus, less than 45 deg angle - can't really see any difference with it on/off (granted, star trails are small rectangles, but I was expecting pinpoints with tracer on).

What might I be missing?

Thanks

06-26-2016, 10:32 PM   #2
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Sounds like another calibration or two might be needed since at 30s, your stars should appear almost perfectly stationary.

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06-26-2016, 10:33 PM   #3
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Calibration must be followed by Precise Calibration in my experience.
06-27-2016, 01:43 AM   #4
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Are you sure you are actually using the astro tracer function?
I ask this only because I have seen mistakes done before where everything is set up and in the end they fire off a normal exposure without using the astro tracer anyway.

06-27-2016, 02:03 AM   #5
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Did you have the camera in Bulb mode? Also, the first couple times I used it was in the backyard - but looking for the stationary stuff to be blurred. It turns out the first couple of times, when I went into Astrotracing mode, I forgot to hit the "start" item in the menu - which takes you to a different screen, where you then trip the shutter. Essentially, you are starting the star tracking software then tripping the shutter in quick succession.

06-27-2016, 11:02 AM   #6
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Hey, thanks all for the responses; this is more complicated than I thought.

jbinpg - If I do precise calibration successfully in the astro on/off menu, I shouldn't also need to do calibration (gps/compass menu) as well, should I?

int obs - Didn't realize I needed to be in bulb mode for astro to work; that may be my whole problem right there. However, on the K1, I don't see the "start" menu item you refer to. The menu (camera #3) allows you to turn astro on/off and do a precise calibration, then in bulb mode, you can use the green button to either set the timer for automatic off, or just use bulb and hit the shutter button twice for on/off.

Please explain.

Thanks much for the help.

fred
06-27-2016, 12:17 PM   #7
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I agree the documentation for actually using the astrotracer is wanting with the K-1. Here is my approach:

1) Switch to "B" mode. Astrotracer will not work otherwise.

2) Do a basic calibration before the precise calibration. This means your lat/long/elev is already burned into the astrotracer before you do the precise calibration which means the precise should complete faster. As well, if you cannot get a basic calibration to complete successfully, there is little chance a precise calibration would be successful.

3) Switch to the "Compass" screen on the Info screen. Once in Astrotracer mode, all astrotracer controls and output are visible and workable from the Compass screen.

I could not find this last compass screen tidbit anywhere in the K-1 documentation but maybe I just missed it. Once in the compass screen, you are golden. Note that the limits for exposure length versus focal length versus lat/long versus subtended camera angle are computed by the astrotracer firmware so you will not be able to extend the recommended exposure time beyond the computed time.
06-27-2016, 04:58 PM   #8
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thanks jbinpg, I will give all that a try (next dark night).

I reread the documentation for astrotracer and saw no reference to the compass screen; I agree that the documentation is poor.

I just spoke to someone yesterday who got a K1 a while back precisely for the astro tracing function, but he could never get it to work to his satisfaction, said pentax support was no help, and finally returned the camera in frustration.

I think he should have tried pentax forum.

Thanks much for the help.

fred

06-27-2016, 05:53 PM   #9
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QuoteOriginally posted by PENFRED Quote
Hey, thanks all for the responses; this is more complicated than I thought.

jbinpg - If I do precise calibration successfully in the astro on/off menu, I shouldn't also need to do calibration (gps/compass menu) as well, should I?

int obs - Didn't realize I needed to be in bulb mode for astro to work; that may be my whole problem right there. However, on the K1, I don't see the "start" menu item you refer to. The menu (camera #3) allows you to turn astro on/off and do a precise calibration, then in bulb mode, you can use the green button to either set the timer for automatic off, or just use bulb and hit the shutter button twice for on/off.

Please explain.

Thanks much for the help.

fred
Hi Fred - I just got home from work and saw your post. A few things - Yes, it needs to be in Bulb since the shutter time can be any value up to 5 minutes or 300 seconds. If it's in any other mode, 30 seconds is the longest exposure that the body will allow. While it is in both GPS and Bulb, the body will time the exposure to the duration you specify in the GPS pages.

I don't have a K1, so I went and looked at the K1 manual. They have changed the interface considerably, actually it appears to be a bit simpler but different. It appears that they have removed the "start" from the menu selection. It appears that if you are in both GPS/Astro and Bulb, then by pushing the shutter, you are doing astro tracking.

In terms of the next dark night - it's here, tonight and through mid next week. The moon rises at midnight tonight and moves later each day. The Milky Way rises in the East South East a bit after sundown, with the new moon on July 4.

06-27-2016, 10:45 PM   #10
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That's good to know, interested observer, I'll be out there !
06-28-2016, 06:19 AM   #11
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QuoteOriginally posted by PENFRED Quote
That's good to know, interested observer, I'll be out there !
Well there are some tools that are helpful.
  • The Photographer's Ephemeris - provides a graphical display of where the sun and moon are going to rise and set, along with the times and directions. It uses google earth so you can just move the location to where ever you happen to be. It is free
  • Stellarium - You can set your location and any time (day, time, year) and see the sky, direction. Set everything in movement - faster than real time and see how everything changes. It is free

06-28-2016, 06:14 PM   #12
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very cool, thanks!
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