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06-16-2012, 07:43 AM   #16
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so it looks like switching to firmware 1.13 got rid of the tracking issue. I am ready to try this again.

06-16-2012, 07:50 AM   #17
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Sounds good. I know I was able to use the unit with an old 400mm lens with a screw mount.

Even though the unit says that you can expose for up to 5 minutes I don't know whether I'd really believe that.

The slightest breath of wind on the camera or even you walking nearby while waiting could affect the image unless your camera mount is in a big piece of concrete buried in the ground.

Long timed exposures require a really solid mount.
06-16-2012, 11:18 AM   #18
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QuoteOriginally posted by mtansley Quote
Sounds good. I know I was able to use the unit with an old 400mm lens with a screw mount.

Even though the unit says that you can expose for up to 5 minutes I don't know whether I'd really believe that.

The slightest breath of wind on the camera or even you walking nearby while waiting could affect the image unless your camera mount is in a big piece of concrete buried in the ground.

Long timed exposures require a really solid mount.
were you able to calibrate using the manual lens? I cannot calibrate with any manual lenses mounted as the accellerometer ends calibration and dims the screen when the camera is tilted even a little. must have something to do with the contacts??
06-16-2012, 03:20 PM   #19
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Works OK with my old lens, it has no contacts at all.

Does the calibration actually report OK or does it just quit.

06-16-2012, 03:46 PM   #20
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QuoteOriginally posted by mtansley Quote
Works OK with my old lens, it has no contacts at all.

Does the calibration actually report OK or does it just quit.
ok, so when using A lenses, calibration carries out just fine. When using M lenses, after a couple of tilts, the LCD screen goes black and if i press menu, i am back at the main menu page (ie out of the GPS page). My workaround for this is to change to an A lens to calibrate and then mount the manual lens. very aggravating.
06-16-2012, 05:29 PM   #21
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When you put on the M lens, what are you entering for the focal length. The maximum I've ever had to use has been 400mm. Just wondering if it 'crashes' if you're using a longer lens or something like that.

Almost grasping at straws here, we have the same equipment except for lenses.
06-16-2012, 11:48 PM   #22
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i enter the correct FL. i will try with my shorter manual lenses, ie 28mm and see if i still get the problem.

06-18-2012, 12:44 AM   #23
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QuoteOriginally posted by mikeSF Quote
were you able to calibrate using the manual lens? I cannot calibrate with any manual lenses mounted as the accellerometer ends calibration and dims the screen when the camera is tilted even a little. must have something to do with the contacts??
I just took delivery of my O-GPS1. The behaviour you describe sounds strange to me: I started out my astro tests with my fully manual smc Pentax-M 2.8 / 100mm and have had "text-book" behaviour as far as calibration and precise calibration are concerned.

So far, I have restricted myself to reasonably short exposure times (about 30 sec.) fairly high in the sky with this lens because I live in a severely light polluted area, but results with this lens have so far been encouraging.

Althoug the manual doesn't say, I am pretty certain that the higher the altitude in the sky, the more error will one have in the compass reading and thus in the tracking. However, Your account of the effects of firmware upgrade from 1.12 to 1.13 triggers me. I'd better do that tonight as well !!!

Last edited by Stone G.; 06-18-2012 at 12:50 AM.
06-20-2012, 02:04 AM   #24
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Finally a bit of clear (although very bright) skies last night. So, I managed to do some more "systematic" tests on Arcturus (42 degrees above the horizon) and the pair Alcor-Mizar (60 degrees above the horizon) around local midnight. Examples shown are unprocessd, non-resized crops 750 pixels wide. Lens used was my old Tamron Adaptall-2 200mm f/3.5 Model 04B.

I think, this is about what I had hoped for. Now I am curious to see if calibration works even better, when I get away from my 4th floor balcony with all its surrounding, potential magnetic disturbances.......
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07-23-2012, 11:04 PM - 1 Like   #25
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got out under clear skies (still lots of light pollution though) and got this shot using the O-GPS for a 2 minute exposure at 10mm. Though the device indicated I could go to 5min max time, i found anything over 2 minutes started making streaks.


Night Glow


composite of 2 images, 1 with the tracer on and one with it off.
07-23-2012, 11:36 PM   #26
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another composite, 1 with the moving sensor for the stars, a 2nd shot with the tracer off for the shed. This is 2min at 10mm. Note, at very wide angles, you are bound to see star trailing due to the extreme distortion from the lens. Likewise, the moving clouds here look like rays emanating from the structure for the same reason.

Heavenly Shed
10-07-2013, 10:55 AM - 2 Likes   #27
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Well, I put the device in a drawer for over a year and just pulled it out again over the weekend to try for a Milky Way shot.
Results were good using a short-ish exposure time of 80 seconds. No visible trailing.

10-07-2013, 04:21 PM - 2 Likes   #28
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And I continue to be happy with the performance of my O-GPS1 with longer focal lengths and shorter exposure times (200 - 400mm and 30 seconds or shorter). Here's a 20s shot of Orion's Sword (crop) taken with the smc Pentax DA* 200mm f/2.8 on a K-5:

10-09-2013, 09:34 PM   #29
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Great info in this thread - Thanks guys. I just acquired a used O-GPS1 - and suffered some trails with 4 minute exposures... so I'll have to revisit with shorter exposure times.
10-09-2013, 10:51 PM - 2 Likes   #30
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I just pulled my unit out after a few months of neglect and managed this with the Pentax-M 50mm f/1.7 wide open (or close to it).

I've come to realize that as a general rule of thumb I tend to have the best results if I take the suggested max exposure time and halve or even third it.

Really horrid light pollution (I shot it out the window across the rooftops here in town), but I was able to beat it down in post fairly well.


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