Larry, I'm very impressed by what you got, particularly considering your challenge in finding dark skies. Where were these taken? The beauty of the O-GPS1 is that you don't have to futz with polar alignment. The downside is that you do have to futz with "precise calibration", which would often confirm working before I had even completed three axis OR fail to confirm when I had done everything (carefully) correctly. Then all of the sudden it might work.
Regarding the ballhead, I think that with a decent ballhead you can do widefield work, but it helps to have a red dot finder or laser pointer in the hotshoe to help you aim. As you know, it is best if your subject is in the center of the field since that is were the best lens performance will be - corners being where coma and changes in flatness of field might show up. Regarding the lens selection, nothing torture-tests a lens like astrophotography. Astrophotography will reveal CA and coma like nothing else. Not all lenses will be suited to astrophotography, given just those two criteria. You are also NEVER going to get the lenses best image wide open, regardless of maximum aperture. You should always try (or compare) stopping down 1 stop from maximum. Since that is the case, I think that you should give more weight to the aperture and less to the focal length, particularly when you are starting out. f/6.3 obviously requires a much longer exposure time than f4 for example. That longer exposure time is going to make more evident problems in your tracking (or influences from other things like vibrations in the ground, sagging of your ballhead, etc. The longer the exposure time the smaller percentage of your subs will be acceptable for stacking. Plus, it is in stacking that you effectively build up the integrated exposure. Finally, longer exposures in less than dark-sky conditions are going to result in you recording the background as less than black. Once that happens you aren't gaining anything with a longer exposure because you have reached the contrast limit. You don't HAVE to do it with single long exposures. That's for the guys with the "real" equatorial set-ups. That being said, I was able to get decent exposures of up to 45 seconds with a K135mm f2.5 stopped down to f4. Even in the film days, a 200mm f/4 lens was the one most often used for widefield astrophotography. That equates to a 135mm on APS-C. Your 200mm shots look very very good. With a DA* 200mm f2.8 you might even have the option of using it wide open AND you can get the benefits of the lens profile corrections. Regarding DeepSkyStacker crashing, make sure you are using the latest beta. For some reason if you Google DSS the page you get doesn't give you access to the latest program. Check to see if you are using this version: http://deepskystacker.free.fr/download/DeepSkyStacker333beta51.rar -d On Sun, Dec 1, 2013 at 11:53 PM, Larry Colen <[email protected]> wrote: > On Sun, Dec 01, 2013 at 10:36:13PM -0600, Christine Aguila wrote: >> Very nice, work, Larry! Excellent. Cheers, Christine > > Thanks Christine. > > I spent most of the day trying to get stacking programs to work and > get a cleaner version. I finally got an image out of nebulosity, but > it looked worse than what I got from a single frame. > > Meanwhile I loaded Deep Sky Stacker on the Windows laptop I use > for work, and it would just choke and crash. > > At some point, I'll give it another try, and I learned some important > things. Like, with astrotracer, it seems like focal length time > seconds seems to need to be below 3,000 (200mm * 15 Sec) maybe a bit > less. > > That's five times better than the 600 rule. > > >> >> Sent from my iPad >> >> > On Dec 1, 2013, at 6:06 AM, Larry Colen <[email protected]> wrote: >> > >> > >> > http://www.fluidr.com/photos/ellarsee/sets/72157638239972733/ >> > >> > Even with the astrotracer 30 seconds at 500mm is too long. >> > Now, I need to find stacking software for my mac. >> > >> > These were photographed on Empire grade at the gate for Grey Whale ranch, >> > with my Pentax K-5 II, using my O-GPS 1 in astrotracer mode. >> > Some were shot with John Francis' 80-200/2.8 and some with my bigma. >> > >> > I learned that using a ballhead sucks for astrophotography. It is >> > impossible to make fine adjustments in just one axis. Hell, it is >> > impossible to make accurate fine adjustments period. >> > >> > -- >> > Larry Colen [email protected] >> > http://red4est.com/lrc >> > >> > >> > -- >> > PDML Pentax-Discuss Mail List >> > [email protected] >> > http://pdml.net/mailman/listinfo/pdml_pdml.net >> > to UNSUBSCRIBE from the PDML, please visit the link directly above and >> > follow the directions. >> > >> >> -- >> PDML Pentax-Discuss Mail List >> [email protected] >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> to UNSUBSCRIBE from the PDML, please visit the link directly above and >> follow the directions. > > -- > Larry Colen [email protected] http://red4est.com/lrc > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- I don't have a problem with idiots. I have a problem with the fact that they have an internet connection. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
