I just returned from a (camel) trekking holiday in Namibia and would like to share my pictures and experiences using my Pentax K5 and the O-GPS1 for astrophotography in the field.
NOTE: This contains a number of hints for improvement, so Pentax employees should read on :-)
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PREAMBLE
I recently sold my telescope because of two reasons:
I live in the middle of a big, light polluted city (Berlin) :-(
I do a lot of outdoor activities, e.g trekking, so I want minimum weight for my camera equipment.
So I was looking forward to using my K5 with the O-GPS1 device under the dark skies of southern Africa.
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DATE & LOCATION:
End of November 2011 in Namibia, around the tropic of capricorn, i.e. 23.5deg south of the equator.
THE SKY:
- Early summer
- Night temperature 8-15deg Celsius
- Milky way appears late, around midnight :-(
- Dusk starts around 04:30h :-(
- Most pics taken around new moon :-)
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THE GEAR
Total weight of all my photo gear was below 3.3kg including my tripod, filter, spare batteries, charger and the cases.
So it was ok to carry it :-)
- Pentax K5
- Pentax FA 50mm f1.4
- Sigma 10-20mm
- Pentax DA 55-300mm
- Pentax O-GPS1
- My mini tripod (1960s, modified, height 30cm) used when a wall or big stone was a available to place it on
- A Novoflex high-class tripod (borrowed from our tour guide), up to 1.7m used when no wall was available
- 3rd party wireless remote shutter
I use the remote for shutter release in the mirror up mode to reduce shake.
This is the gear I used for the following pictures :-)
So per picture the weight of the set-up was typically around 1.5kg. Beat that!
POST-PROCESSING
Some basic adjustments were done in Apple Aperture.
NO stacking of pictures! As I was in the middle of nowhere I had to keep an eye on battery life, so I decided not to do multiple picture for later stacking
NO denoising!
Pictures are cropped and probably reduced in size to comply with the upload restrictions in this forum.
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USING O-GPS1
- Easy to attach in the camera in the dark.
- The blue light is FAR too bright, especially as it shines right into your eye when looking through the viewfinder :-(
I put duct tape onto the blue LED to reduce its shine :-)
(The same is true for the red blinkenlight on the camera when in the remote shutter mode. Again, tape it dim :-)
- Power consumption is low. I used my O-GPS for some 9h in all and it still runs on the same rechargable AAA battery :-)
CALIBRATION
This somewhat remains a mystery to me.
It seems that the rotational movements during calibration must be above a certain angular speed for getting a successful calibration, but how fast and wild to I have to turn the camera? Is faster better?
There are two menu items concerning the calibration, one in the GPS menu and the precision calibration in the astro tracer menu.
Are they related to each other? If so, is there a sequence to obey?
TRACKING TIME
As a rule of thumb I used no more than 50% of the indicated maximum tracking time.
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RESULTS
Results depend on the orientation of the camera! Looking east or west seems to produce much better results compared to north or south, which produce star trails when using more than 100mm focal length!
This is what I shall refer to as the "calibration mystery".
Focal length Result
10mm middle of picture is ok. Towards the outer edge star trailing occurs (due to wide angle distortion?!)
20mm ok
50mm ok
300mm ok for easterly and westerly directions and elevations below 45deg.
NOT ok for northern and southern directions star trails appear. (The calibration mystery)
STELLAR OBJECTS
Milky Way and Great Magellan Cloud
Southerly, 04:45h
Then it was located north-south passing straight overhead.
10mm f4 ISO3200 160s
Southern cross, coalsack and lambda centauri nebula (IC2948)
Southerly, approx. 30 deg elevation
50mm f2.8 ISO3200 100s
Eta Carina Nebula NCG3372
Above the southern cross
50mm f2.8 ISO1600 100s
Great Magellan Cloud and a meteor
Southerly, approx. 30deg elevation at 22:00h
50mm f2.2 ISO1600 120s
Not pictured: On 300mm star trails appear :-( (The calibration mystery)
Orion Nebula M42
Easterly, approx 30deg elevation at 22:00h
300mm f5.8 ISO6400 60s
Andromeda Galaxy
Northerly, approx. 45deg elevation around 22:30h
300mm f4 ISO6400 40s
NOT ok. Star trails appear :-( (The calibration mystery)
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Recommendations to Pentax:
Must have:
- A tiltable screen would be really useful for shots exceeding 30deg of elevation
- Provide a way to dim all lights on the backside of the camera
- More detailled instructions for a "high quality" calibration
- Debug the north-south calibration mystery (or tell me how I can do it)
Nice to have:
Integrate the piggy bag box into the next camera.
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CONCLUSION
I guess this will / can never replace a tracking telescope, but at 80 grams extra for astro tracking in the field this is an nice device that could become great after some debugging :-)
Last edited by jephi; 02-16-2012 at 11:52 PM.
Reason: Minor corrections in text