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11-23-2015, 10:01 AM   #31
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For convenience, I set up a USER mode that does "K" white balance at 3800, RAW, B, remote with 3 seconds, long-exposure and high-ISO in-camera noise reduction off, and have the menu setting for bulb operation on "wax on/wax off" instead of press/release. Come to think of it, I should make sure that the screen brightness is set to -7 too.

I know that the WB doesn't affect the image per se with RAW, but when I use AWB I can get wildly different looks from successive exposures as seen in "As Shot" in Adobe Camera Raw. Apparently the camera is notional as to exactly what WB it's reading off the image. (I'm talking successive identical exposures of the same scene on AWB, mind you.) So it's a convenience to start from a starlight setup.

The Astrotracer -- I know, right? I was just bowled over when I read about it. [Smacks forehead] Of course you could do sidereal-motion compensation -- though certainly I never thought of it. Sensor-based shake reduction wins again! So let me get this straight, you can buy an ancient-but-tack-sharp old manual-everything lens dirt-cheap on eBay, mount it on your Pentax, buy the amazingly affordable O-GPS1, and voila, instant astrophotographer!

And it has another advantage even if you don't have a remote: You can set up timed exposures much longer than the measly 30 seconds that the body gives you. Don't know what the max is but it's always at least as much as the max tracking time.

Now if they'd just update the K-5 II firmware to add a control for that fribberty frakkin' 400-lumen blue LED...well, we'll always have electrical tape.

11-23-2015, 11:57 AM   #32
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The camera body must be in B when using the Astrotracer function of the O-GPS1 since the unit itself takes over the exposure function from the body. Also, the blue LED can be turned off in the K-3 series so a firmware update may indeed be possible for other K bodies. In my experience with comet hunting, I had to give up on the O-GPS1 for tracking because it does poorly at high declinations. I got a real tracking mount instead. This takes nothing away from the genius of the unit; it is just a matter of simple physics that the camera cannot rotate the mirror enough to compensate for the high angular velocities at high declinations.

11-24-2015, 07:53 AM   #33
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Now if they could add a mode like the Live Compensation in Olympus M43s that would be great. It's basically interval shots, with in-camera layering/stacking, so that only areas with an increase in light get changed. So you shoot foreground, then just let it run for a couple of hours to do startrails. Meanwhile, the foreground doesn't change, since it never gets lighter there. Sorta like an ND filter. And Oly Live View is kinda nice too; you can see a bulb exposure build in the LCD, complete with histogram, so you can turn it off once you get the exposure you want.
11-25-2015, 12:40 PM   #34
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My first request for a feature update for the K-3 was to add a 3 to 5 sec MLU before each frame in an interval series. Astro DSO work demands MLU. This would allow me to set a long series and then walking away rather than tending a shutter release.

As for Live Compensation, have you tried the Bright multi-exposure mode? Same idea that only bright pixels above a certain value get added to the image.


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