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12-11-2012, 03:27 PM   #16
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QuoteOriginally posted by mikeSF Quote
i used the O-GPS1 for the long exposure
Agreed that it's a nice image. Did you blend a 2nd non-GPS exposure for the foreground, or were you so wide that the O-GPS1 correction didn't blur your foreground much?

12-11-2012, 03:31 PM   #17
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QuoteOriginally posted by DeadJohn Quote
Agreed that it's a nice image. Did you blend a 2nd non-GPS exposure for the foreground, or were you so wide that the O-GPS1 correction didn't blur your foreground much?
exactly. when i use the O-GPS1, I shoot one with it on and one with it off then blend foreground in with a layer mask.
12-11-2012, 03:38 PM   #18
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QuoteOriginally posted by PentaxJax Quote
Karl. This shot of the Milky Way is stunning.
Can you give us a reason for this lens choice vs others? I too would like to take the first steps in night sky/ Astro photography but have a limited budget and would like to know what lenses and why.
Thanks! Some additional info on that image - it's a combination of 8 30-second exposures, aligned with Hugin and stacked in GIMP.

First - it's cheap (I also have a limited budget.)

Second was focal length - 8mm is wide enough to get the entire Milky Way (you can see the trees on each side of the clearing at the top and bottom) and the wider your lens, the longer your exposure can be before star trails become apparent. (Formula for APS/C is 300 / focal length, in seconds - so the 8mm can do exposures up to 37 seconds.)

Third, manual focus - AF lenses will focus past infinity, so unless you have something to focus on, it can be difficult to achieve proper focus. MF lenses have a hard stop at infinity, so it's just a matter of turning the focus ring to the end (although when I got it I had to calibrate the Samyang 8mm, which isn't unusual for this lens.)

Drawbacks with the 8mm is that it's a fisheye - so including foreground elements would have been distracting (IMHO) with the curvature (unless I put the horizon in the middle, which I didn't want to do.) At f/3.5 it's also a little bit slow. Samyang announced a 10mm f/2.8 rectilinear this autumn, so if you're going to be buying a lens to do that, I'd wait until that's available to see if its IQ is as good as the 8mm.
12-11-2012, 05:31 PM   #19
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QuoteOriginally posted by Karl Stevens Quote
AF lenses will focus past infinity, so unless you have something to focus on, it can be difficult to achieve proper focus.
Karl
Thank you. That is exactly the kind of response I and hopefully the OP was looking for. I see many great examples on this site but it is sometimes hard to know how to improve when you dont know what is holding you back. The info about infinity focus of AF lenses I didnt know, and that was a question I remember asking myself at the time. How do I focus this???
Lately I have gathered some more equipment, as we all do So I have a decent tripod, Adam is sending me my new F remote! and in the coming weeks I will get out from here where the light pollution is pretty bad and test.
I have a 35 2.4 which I will try though this doesnt have an infinity setting. But after reading your post I noticed that my Tamron 28-75 does! Guess I should have looked closer My excuse is it was dark out!

12-11-2012, 06:05 PM   #20
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QuoteOriginally posted by mikeSF Quote
nice!
Thanks! Your shot as well!
12-11-2012, 06:12 PM   #21
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QuoteOriginally posted by mikeSF Quote
when i use the O-GPS1
Mike.
Can you tell me more about how you use the O-GPS1?
I would like to know how much it extends your exposure time for each shotbefore trailing occurs, and are there any obvious drawbacks from using it. I thing this would be a better purchase for me than a new lens right now.
12-11-2012, 08:42 PM   #22
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QuoteOriginally posted by PentaxJax Quote
Mike.
Can you tell me more about how you use the O-GPS1?
I would like to know how much it extends your exposure time for each shotbefore trailing occurs, and are there any obvious drawbacks from using it. I thing this would be a better purchase for me than a new lens right now.
first off, i am not the biggest fan of the O-GPS1. It is ok but has a few buggy things about it.
The max exposure time depends on several factors such as focal length, global position, direction, etc. At first, i thought i was going to be getting 5 minute exposures (this is advertised as a maximum "best case" exposure time), but at least for my shooting, if i am lucky, I can get 90 sec before trailing is evident. that is still good, but maybe not worth the investment for an occasional star shot.

The obvious limitation is that if you want to include terrestrial objects along with the sky, the sensor is moving, so the ground will become blurred. So you need to take two shots and blend them together. This is part of the deal and fairly easy to do.

I dont use it for any sort of deep sky, galaxy, shooting, etc so i have no idea how it performs in that capacity. I did try to use it with my manual K-mount lenses and was not able to calibrate them due to some bug that exits the calibration function whenever I tilt the camera. what a hassle.

The embedding of GPS data into the EXIF is great and very useful for my purposes. I believe the compass is magnetic because sometimes when I am shooting near spinning turbines, the compass switches back and forth 180 degrees rapidly.

oh and that blue LED is so bright when you are in total darkness and need to put your eye up to the viewfinder. You must cover it with tape or you will be seeing blue spots for the rest of the night, lol. Ask me how i know this.

overall, i dont really recommend it at its current price point. fwiw. it was an impulse buy for me.
12-11-2012, 08:48 PM   #23
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QuoteOriginally posted by mikeSF Quote
overall, i dont really recommend it at its current price point. fwiw.
Mike. Good to know! I may have to do more digging. I will try some shots with what I have when the remote arrives, if the clouds will let me. The last week has been nothing but fog here.

12-11-2012, 08:54 PM   #24
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here's another 2 shot composite usiing the ogps1
12-12-2012, 10:09 PM   #25
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Perhaps your question has been answered, but I've had decent luck using a few different lenses (AF and MF) for star/star trail shots. Each of these images was taken with the K5 mounted on a solid tripod with a cable release. MikeSF's pics with the OGPS just make me drool. I would love to try one someday.

From the Sigma 10-20:






From the DA 15:



From the Vivitar 28/2.8 CF K02:




12-15-2012, 06:05 AM   #26
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Original Poster
Thanks for the responses..

Theres another Samyang on its way soon supposedly (the 10mm)

The 8mm fish looks interesting.. Is calibrating the Samyang(s) correctly to infinity difficult?

The 15mm pentax looks good.

How much are you actually using the various lengths on the zooms?
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