Thanks for that, John. It only took 50 years to get the answer!
Alan C
-----Original Message-----
From: John
Sent: Saturday, April 09, 2016 8:48 PM
To: Pentax-Discuss Mail List
Subject: Re: experimental geso Thunderhill at night
If you follow the "rule of 600", the FA31 gives you a maximum exposure
time of 12.9 seconds before you start to see star trails. At 20 seconds
any trails would still be to short to be obvious.
(600/(31*1.5))
On the K-1, without the crop factor, you'd get 19 seconds with the FA31
before the star trails start to show up.
On 4/9/2016 1:42 PM, Alan C wrote:
I'm surprised there is virtually no lateral movement of the stars
visible with a 10 sec. exposure. I suppose the short focal length plays
a part. In 1965 I photographed the Ikeya-Seki comet using a Super Tak
135/3.5, ASA 1250, 5 sec and slight movement was visible.
Alan C
-----Original Message----- From: Larry Colen
Sent: Saturday, April 09, 2016 5:33 PM
To: Pentax-Discuss Mail List
Subject: Re: experimental geso Thunderhill at night
Mark Stringer wrote:
I'm impressed and encouraged. I guess you could call it rich field
photography. I like them all. What was your technique? Just the K-3II
Astrotracer? Any pointers on the setup"
K-3II, no astrophotography, that would blur the foreground. My
exposures were 10-20 seconds. You can get exif data easily by using the
fluidr front end to flickr:
http://www.fluidr.com/photos/ellarsee/sets/72157666817994741
I used the FA 31 wide open for all of them. I didn't really have time
to explore further, I didn't know if/when the gates would be closing
that night and didn't want to be locked at the track.
For photos like this, I would particularly like to have the large sensor
of the K-1, and wish that I could get a sigma 20/1.4 for it, although if
I don't do astrotracer, the samyang 24/1.4 is very good for this sort of
stuff.
I took a lot of panoramas, and stitched them together in lightroom.
I think that the setup that would give the best results, to address Rick
Womer's comment about lunar light washing out the stars, would be to
shoot a scene early at night with just a little bit of moon in the sky,
leaving the tripod set up, then come back later, after moonset and shoot
the stars, from the same position, using astrotracer, and use photoshop
to stitch the photos together.
For most of these, I specifically chose to shoot from approximately the
driver's position on the track, and tried to position myself at critical
reference points, such as turndown, looking through the apex.
The second one on Thursday night was shot from the Turn 11 flagger
stand, which gives a good view of the technical section of the back of
the 3-mile track.
On 4/8/2016 8:26 PM, Larry Colen wrote:
There were relatively clear skies at thunderhill racetrack this week,
and I tried a bit of night time panoramas. I'd really like wider faster
lenses, and bigger sensors. I also think that it would work better with
just a little bit of moon in the sky to light the track, but not so much
as to wash out the stars.
While there are rough bits on the photos, I really want to explore this
concept further:
http://www.flickriver.com/photos/ellarsee/sets/72157666817994741/
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