Timeline for Pentax Astrotracer: Lens error on wide angle lenses?
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 31, 2019 at 20:58 | vote | accept | jstarek | ||
| Mar 31, 2019 at 20:58 | comment | added | jstarek | Today, I have finally been able to take an hour under a moderately useable sky and test this. It turns out you were right: With careful calibration, I was able to produce an image that showed almost no streaks at all, except for the most extreme corners. I also could confirm the dependency between tracking accuracy and elevation, with best results around either the celestial pole or along the southern horizon. | |
| Feb 6, 2019 at 20:07 | comment | added | scottbb♦ | @JimGarrison Great question. Honestly, I don't know the scope of the problem, but I'd assume yes, it complicates it, but the degree depends on your location (relative to the shift of the magnetic pole), as well as the "smarts" or updatability of the software that relies on magnetic orientation. I think that's a great question for Geographic Information Systems, though. | |
| Feb 6, 2019 at 18:55 | comment | added | Jim Garrison | Will the recent magnetic pole movement complicate this issue? | |
| Feb 6, 2019 at 13:49 | comment | added | jstarek | OK, then I'll focus on calibration accuracy in one of the next tests -- if the skies ever clear up again here... | |
| Feb 6, 2019 at 13:44 | comment | added | scottbb♦ | @jstarek Yes, I'd rule out lens errors. Lens problems you're likely to see during astrophotography, especially with wide angle lenses, are usually coma, chromatic abberrations (color separation of stars), and astigmatism (causing smearing of the stars). All of these aberrations are worse away from the center of the image, and importantly, have radial symmetry around the center of the image. See: lensrentals.com/blog/2010/10/the-seven-deadly-aberrations, and lonelyspeck.com/… | |
| Feb 6, 2019 at 13:36 | comment | added | jstarek | Great reply, thanks! I took great care to calibrate the device, but that was at the start of a 45 minute series of exposures. Perhaps this should be done more often. The Pentaxforums.com comment reads as if I really hit the worst spot to operate the device in... I'll re-test on a different area in the sky. So, all in all, you would rule out lens errors as the root cause? | |
| Feb 6, 2019 at 13:24 | history | answered | scottbb♦ | CC BY-SA 4.0 |