I wonder if there are any Astrotracer users among the members of this group?
I just got the PENTAX GPS Unit O-GPS1, not only because of its Astrotracer function and certainly not as a repalcement of my equatorial mounts, but I do look forward to try out this neat little gadget.
Unfortunately, we are now in the period of very luminous nights - "white nights" - of Scandinavian summer and it won't be until late August that I may produce any "pretty pictures" - if any at all!
Meanwhile, do other memebers of this group have Astrotracer images, tips and tricks to share?
Apart from the morning of the Venus transit (I got 274 pictures of that) weather is extremely cloudy currently, but I did get some proof-proof-of-principle over a copuple of nights:
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Arcturus, 100mm focal length, 30s exposures with and without Astrotracer (on two different nights)
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Alcor-Mizar, details as above
Without knowing for sure, it seems fairly obviously to me that the strength of the O-GPS1, the incorporation of a magnetic sensor and thus the incorporation of an electronic compass, is also its main weakness:
- When you have the true azimuth and altitude and exact position and time, it is straightforward to convert to hourangle and declination and thus determine the proper motion of the sensor to counteract the celestial sphere's rotation. And the Astrotracer seems to have good algortithms for that. So far, I haven't noticed any tendency towards field rotation using a 100mm lens for my first tests.
- However, the magnetic sensor will have ever harder times to read the direction of the magnetic field, the higher the sensor points in the sky, and when it points towards Zenith the direction will be completely undertermined.
- I further wonder, if the camera's inclinometer will work all the way up to a perpendicualr position? We all know, that the display of inclination disappears long before then.
But knowing and understanding these limitations better, it should be possible to choose appropriate times of the year to photograph portions of the sky with decent results - or so I hope, at least........
B.R. / Steen G. B.