A note on using hyperfocal. If you're going to estimate distances be
sure that any error is on the long side. If you're under the hyperfocal
distance you'll miss infinity. If you're over it you'll just slightly
lengthen the minimum focus distance.
Chuck Norcutt
On 7/26/2014 4:21 PM, Chuck Norcutt wrote:
Looks pretty good to me. Better than anything I ever did with a
telescope. The upper left of your image seems to show a bit of rotation
so maybe you need to move the camera more frequently. I guess I need to
study how this is done. I don't understand the need for so many "dark
images" or the very large number of light frames for that matter.
As to hyperfocal distance for 100mm on 4/3 sensor
f/2.8 about 700 feet
f/5.6 about 300 feet
You can cut those distances in half for use on small images like a 4x5
print or web images.
Chuck Norcutt
On 7/26/2014 11:58 AM, Paul Braun wrote:
One of the corporate subcontractors brought in to help with the tech
nightmare being dumped on us turns out to actually be a nice guy, a
fellow photographer, and really into astrophotography. He and I were
talking, and he was showing me some of the results he's gotten with a
dslr and a 300mm, using Deep Sky Stacker and shooting anywhere from
200-300 frames at a time. He challenged me to try it the other night,
so I drove out about 30min East of here, found a rural driveway in the
middle of nowhere, set up the tripod and the E-M5 with the OM 100/2.8
and shot 179 frames (sadly, I realized that I forgot my cable release,
so it was an extreme annoyance to do so...)
You can shoot about 10 4-sec frames before you need to slightly
reposition. Also, after you shoot your "light frames" or actual image
frames, then you put the lens cap on and shoot roughly 50 "dark frames"
or "bias frames" which the software uses to detect sensor noise.
Then you dump 'em all into the software, click "go to work', and go do
something else for a while.
Since I didn't have my iPad with the gps-enabled sky watching app, I
just focused on two of the stars in the Big Dipper. The image I got
isn't spectacular, but it is a start. Once I get more comfortable with
getting better source images (I discovered that DSS can read DNG, so
next time I'll shoot RAW, import into LR as DNG, then ship 'em over to
the Win7 box for stacking (DSS is a Windows app. Would like to find one
that plays in OSX-land). I then saved the result out as TIFF, sent it
back to the Mac, imported into LR, and did some tweaking to bring out
the dimmer stars.
I'll post one once I'm happy with the results.
Oh, what the hell. We're famiily. Here:
http://zone-10.com/tope2/main.php?g2_itemId=13917
Enjoy. I will try to find a nebula or other more exciting things next
time. By the way - anyone know offhand the hyperfocal point for that
lens?
I also want to try a wide-field shot using the DZ 14-54 wide open, and
it at least has a focusing scale, unlike the MFT lenses...
--
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