Re: Using a DSLR

From: Petter Aslaksen (fluorgutten@googlemail.com)
Date: Sat Dec 15 2012 - 06:42:29 UTC

  • Next message: Wolfgang Hamburg: "Re: Using a DSLR (was Re: North Korea satellite observed)"

    Thank you,
    
    Wonderful tips, tested out the live view zoom on my EOS 500D with Jupiter
    in focus yesterday, and it made it easy to focus very accurately.
    
    Seems like I am on the right track, just need to use my other lenses.
    
    And buy a new camera.
    
    *Petter*
    *31.7361N, 6.0422E / 63.4303N, 10.4525E*
    
    On Fri, Dec 14, 2012 at 10:47 PM, Marco Langbroek <marco.langbroek@online.nl
    > wrote:
    
    > Op 14-12-2012 21:33, Greg Roberts schreef:
    > >
    > > Have no problems with the discussion about "live focus" using modern DSLR
    > > cameras. Ive just purchased a NIKON D3100 which has this feature - I
    > focus on a
    > > bright  star - its easy to see and brightness depends on the f/stop of
    > the lens
    > > used since you are actually viewing through the lens - then use the zoom
    > feature
    > > in "live view" - its actually just a magnified image of the initial
    > image and
    > > not a true zoom but there is no problem seeing where the image is
    > sharpest.
    >
    > To be clear: that is true only for the Nikon D3100. With the canon EOS, you
    > truely zoom in on the sensor pixels.
    >
    > About the lens choice: for LEO I use a 2.5/50mm stopped down one stop to
    > 2.8;
    > for fast LEO (Keyholes near perigee, objects near decay) I use a 2.0/35mm
    > at
    > F2.0 because of the larger FOV, and for faint LEO I use an 1.4/85mm at F1.4
    > (this lens, a SamYang 1.4/85mm which is made with fittings for several
    > camera
    > brands, I can truely recommend, it is marvelous!).
    >
    > For HEO I use a Zeiss 2.8/180mm. I used this for some time for GEO as well
    > but
    > now use the 1.4/85mm for that as it has a larger FOV but almost the same
    > light
    > gathering power (aperture). I still us the Zeiss for HEO because it better
    > shows
    > the tiny satellite trails.
    >
    > I work at ISO 800-1000 for LEO and GEO, sometimes 1600 for HEO in the
    > zenith.
    > How high an ISO setting is feasible depends on your sky AND the noise
    > characteristics of your camera (my new EOS 60D is much better with respect
    > to
    > noise at high ISO than my 450D was).
    >
    > I generally use 10 second exposures (as I initially calibrated my camera
    > for 10
    > second exposures, and it is s fitting exposure for a 50mm lens on LEO
    > objects).
    > In strong twilight I sometimes take shorter exposures.
    >
    > In my experience aperture actually does make a difference: stopping a 2.5
    > lens
    > down to 3.5 does mean you'll lose in limiting magnitude.
    >
    > - Marco
    >
    > -----
    > Dr Marco Langbroek  -  SatTrackCam Leiden, the Netherlands.
    > e-mail: sattrackcam@langbroek.org
    >
    > Cospar 4353 (Leiden):   52.15412 N, 4.49081 E (WGS84), +0 m ASL
    > Cospar 4354 (De Wilck): 52.11685 N, 4.56016 E (WGS84), -2 m ASL
    > Station (b)log: http://sattrackcam.blogspot.com
    > Twitter: @Marco_Langbroek
    > -----
    >
    > _______________________________________________
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    >
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