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04-05-2012, 06:49 PM   #61
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Interesting thread. Dumb comment probably, given this is a GPS unit, but as per the warning in the pentax calibration page linked earlier in the thread, is there an opportunity to enter compass declination to account for magnetic field variance at different locations?

04-06-2012, 12:53 AM   #62
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No...
04-06-2012, 08:48 AM   #63
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I thought doing the 3 way calibration the software was then calibrating for the magnetic field offset.
Hank
04-06-2012, 09:44 AM   #64
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QuoteOriginally posted by Clarkey Quote
Interesting thread. Dumb comment probably, given this is a GPS unit, but as per the warning in the pentax calibration page linked earlier in the thread, is there an opportunity to enter compass declination to account for magnetic field variance at different locations?
The unit determines true north from the GPS data and reports all bearings in true north. For astro purposes only true north is relevant.

DAZ

04-06-2012, 10:27 AM   #65
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That is true all bearings are showing true north because you are moving. At a stationary site with no movement a GPS will tell you where you are and the electronic compass tells you the direction you are pointing the camera. The compass is what is calibrated for true north. True north is what you want but not easy to point. That is why many software programs are written for different telescope mounts to help you find true north.
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04-08-2012, 11:34 AM   #66
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Good points re:GPS. I mention the question about the unit appearing to work well with one axis, and not on the other. I was then wondering why the comment on the pentax calibration website indicated:
QuoteQuote:
At locations that are strongly affected by environmental magnetism, it may be difficult to make a successful calibration, or the O-GPS1 may not point in the proper direction when calibration is completed. The same may result when the O-GPS1 is calibrated indoors.
* At locations affected by geomagnetism, such as in volcanic regions, it may be difficult to make a successful calibration, or the O-GPS1 may not point in the proper direction when calibration is completed.
I then wondered if this was the cause of the poor calibration/ results on one axis that some have noted.
07-22-2012, 11:32 PM   #67
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OMG! I had no idea that the Pentax O-GPS1 GPS unit had the ability to do some limited tracking!

When I read the OP Jephi's posting and his exposure times, I first thought to myself, that is impossible... no way those photos are over 8 - 12 seconds without star trails! Reading further, I learned that the GPS unit works with the K5's sensor to perform a little Earth rotation compensation! How awesome is that?

I'm going out to buy one tomorrow!


Thanks to all who participated in this thread!
12-10-2012, 03:28 AM   #68
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Hi all, I'm new to this. May I know how do you pin point where to shoot (e.g. milkway or Orion Nebula M42). Do you use any apps?

Thanks....

12-10-2012, 06:22 AM   #69
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QuoteOriginally posted by jasonlel Quote
Hi all, I'm new to this. May I know how do you pin point where to shoot (e.g. milkway or Orion Nebula M42). Do you use any apps?

Thanks....
If you have a planetarium program (such as Cartes du Ciel - Sky Charts) you can get the compass heading and altitude above the horizon for celestial objects at any given place and time

- but you will have to learn to spot the constellations and brighter stars by eyesight anyway. Further, you won't be able to see much in your camera viewfinder so, a finder scope parallel with the camera will be a good accessory.
12-10-2012, 06:29 AM   #70
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QuoteOriginally posted by Clarkey Quote
Good points re:GPS. I mention the question about the unit appearing to work well with one axis, and not on the other. I was then wondering why the comment on the pentax calibration website indicated:

I then wondered if this was the cause of the poor calibration/ results on one axis that some have noted.
Precisely. The O-GPS1 will "know" the general magnetic declination quite well, but highly localized magnetic disturbances, for example if you shoot from a re-inforced concrete platform, will degrade the calibration. Also note, that without such disturbances, the O-GPS1 promises an accuracy in compass reading about 5-10 degrees. Thus, there is a limit to the duration of exposures and the focal lenghts used that would make sense.
12-10-2012, 08:39 AM   #71
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I imagine the issue with the GPS1 and polar north is more due to the fact that the the stars don't move across the sky so much as rotate from our perspective.
01-12-2013, 10:22 PM   #72
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Hello all, the O-GPS1 is my most favorite gear of 2012


Name:  DSCF4217-imp.jpg
Views: 2131
Size:  417.7 KB
my setup: Pentax K5 , O-GPS1, DA*200, 7x35 finderscope, Manfrotto 410 Geared Head


Name:  IMGP0877 - Version 2-imp-imp.jpg
Views: 1943
Size:  121.0 KB
Rosette Nebula - NGC 2237
(Bright Nebula in Monoceros)
06h31m0s
+05 ˚02'19.5"


w/ LPS-P2 light pollution filter
ISO3200
F2.8
120s

(PS artificial flat-field)

please check my site for more detail
01-12-2013, 11:07 PM   #73
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QuoteOriginally posted by Stone G. Quote
If you have a planetarium program (such as Cartes du Ciel - Sky Charts) you can get the compass heading and altitude above the horizon for celestial objects at any given place and time

- but you will have to learn to spot the constellations and brighter stars by eyesight anyway. Further, you won't be able to see much in your camera viewfinder so, a finder scope parallel with the camera will be a good accessory.

use bright stars as a guide to finding fainter objects, that's call Star hopping

as Stone said, you will need a finderscope and a star map/sky chart(mine is Skysafari+ for iPhone) ,
01-04-2014, 10:41 AM - 1 Like   #74
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Hello everybody,

Here my last shots with my K5 + O-GPS1 + 50 mm f/1.4, near Toulouse (France) :

Pleiades - M45 & NGC 1499


27/11/2013
Stack: 3 images ISO 400 F2.8 (2 x 120 sec + 1 x 300 sec)

Andromeda Galaxy - M31


28/11/2013
Stack: 6 images
- 3 images ISO 800 F2.0 (3 x 60 sec)
- 3 images ISO 3200 F2.0 (3 x 30 sec)

Orion - M42


28/11/2013
Stack: 3 images
- 2 ISO 400 F2.0 (2 x 60 sec)
- 1 ISO 200 F2.4 (1 x 60 sec)

Chris A.
01-04-2014, 02:46 PM   #75
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QuoteOriginally posted by Chris A. Quote
Hello everybody,

Here my last shots with my K5 + O-GPS1 + 50 mm f/1.4, near Toulouse (France) :

---------


28/11/2013
Stack: 3 images
- 2 ISO 400 F2.0 (2 x 60 sec)
- 1 ISO 200 F2.4 (1 x 60 sec)

Chris A.
Congratulations - very good! I even spot a faint trace of the Horsehead Nebula (below the belt star Alnitak) in your Orion Image. That's quite an achievement with such relatively simple means!
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