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09-14-2014, 05:53 PM   #1
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O-gps-1 question

Hello, any gps users know the longest exposure time that can be used before foreground objects blur?

09-14-2014, 06:08 PM   #2
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That depends on the focal length for each given exposure, since that dictates how quickly the sensor will shift. Longer focal lengths will cause the sensor to move more quickly and reduce the maximum exposure time. However, I gotta say that if you want the foreground objects to remain sharp, you might end up with exposures short enough that the O-GPS1 will be redundant.
09-14-2014, 06:33 PM   #3
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Exactly what aremmes posted. At the wide end - up through about 25mm, I am seeing about 40 seconds. That is about an additional 10 to 20 seconds with out shooting with the GPS. You start to get some smearing, but you really need to look.

The best approach is a two shot merge - one with GPS for the stars and another without GPS for the landscape.

09-14-2014, 08:23 PM   #4
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QuoteOriginally posted by interested_observer Quote
Exactly what aremmes posted. At the wide end - up through about 25mm, I am seeing about 40 seconds. That is about an additional 10 to 20 seconds with out shooting with the GPS. You start to get some smearing, but you really need to look.

The best approach is a two shot merge - one with GPS for the stars and another without GPS for the landscape.

Your best bet s to just take two shots - one with the tracker on, and one off, then stitch in post process. Odds are you'll probably need two separate exposures anyhow if you have even the least bit of artificial light going on, since the sky would probably be able to take a much longer exposure than the ground will.

09-15-2014, 05:10 AM   #5
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I've seen a shot of the Milky Way at 2 minutes using the GPS on a K-50. But I can't find it anywhere now. I remember the image was crisp and with out any bloating of the stars let alone streaking.

As for the foreground, I guess that will also depend on the focal length. Best use the two shot approach for crisp results.

I want to get the GPS unit.. how are you finding it?
09-15-2014, 11:33 AM   #6
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I'll just say welcome to the forum and let clever folk that me answer your question.
09-15-2014, 12:38 PM   #7
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Welcome to PF and bonjour from France, Chris ... Please post us an image or two soon. Salut, J
09-16-2014, 04:07 PM   #8
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QuoteOriginally posted by Anticles Quote
I've seen a shot of the Milky Way at 2 minutes using the GPS on a K-50. But I can't find it anywhere now. I remember the image was crisp and with out any bloating of the stars let alone streaking.

As for the foreground, I guess that will also depend on the focal length. Best use the two shot approach for crisp results.

I want to get the GPS unit.. how are you finding it?
I'm still waiting for Pentax Canada to send it, just trying to get as much info as I can right now

---------- Post added 09-16-14 at 07:09 PM ----------

QuoteOriginally posted by Sagitta Quote
Your best bet s to just take two shots - one with the tracker on, and one off, then stitch in post process. Odds are you'll probably need two separate exposures anyhow if you have even the least bit of artificial light going on, since the sky would probably be able to take a much longer exposure than the ground will.
Thanks, this seems to be the best way, what software do you use for merging the 2 photos?

09-16-2014, 09:21 PM   #9
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QuoteOriginally posted by chris seager Quote
I'm still waiting for Pentax Canada to send it, just trying to get as much info as I can right now

---------- Post added 09-16-14 at 07:09 PM ----------



Thanks, this seems to be the best way, what software do you use for merging the 2 photos?
Generally, I don't (I tend to aim more for the foreground and let the sky do its own thing), but I'd probably just pull out Photoshop and play with masking if I did decide to go that route.

Theres a member on here (I want to say MikeSF) who uses this technique to fantastic effect. His flickr stream is here...

https://www.flickr.com/photos/mikeoria/with/14344353593/

He actually does the opposite of what I described it seems - his locations are utterly dark, so he has to expose more for them then the sky, as the sky is brighter for his locations.

I love night shooting, and one thing I've learned is exposure can be a pain to predict at night, as it can change at any given moment. It really is mostly a learning experience through trial and error to figure out what works for your style of shooting.

Even with everything being equal, you'll still have things like the ever changing phases of the moon and shifts in local light pollution that can make what works one day *not* work the next.

I actually had a night when I was out trying to shoot a meteor shower (I failed) when clouds rolled up in front of me with the moon at my back. I was all WELP and ready to pack it in and decided "Eh. Maybe a few more minutes..." When I managed to snag what's personally one of my favorite shots I've done.



That same location on a dark-sky night without the moon gave me this...



Same lens, basically the same exposure times at the same exposure settings. If I'd taken the time to do so, I could have exposed for another minute or two to pull the detail up from the ground on that second shot (though the houselights stage right would no doubt have blown things out) and composited them, but again... not really my style.
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