Re: sats and scopes

From: Bruno Tilgner (Bruno_Tilgner@compuserve.com)
Date: Tue Aug 08 2000 - 14:13:30 PDT

  • Next message: Bjoern Gimle: "Obs 23728"

    >Here is a part of a review of the Vixen... it doesn't appear to do a very
    >good job.
    
    I can offer some comments based on personal experience with the VIXEN
    SkySensor 2000 PC:
    
    > When I tested this with several passes of the International Space
    >Station and Mir, SkySensor never placed the satellite in the main
    telescope
    >eyepiece. Close, within the finder, but not in the main optics.
    
    There are several possible reasons for this:
    1. Inaccurate TLEs; those of ISS are ageing rather quickly.
    2. The internal clock must be set to 1 second or better if possible.
    3. The coordinates of the observer may be inaccurate or in the wrong
    geodetic system (i.e. not in WGS84).
    
    
    >One catch: if the mount slews up from the west, when it reaches the
    meridian
    >it stops and waits for you to command it to flip itself to the other half
    of
    >the sky, where it will resume tracking the satellite to the east.
    
    This is indeed a very annoying feature. I have eliminated it by operating
    the SkySensor in altazimuth mode. This avoids the reversal when the
    meridian
    is crossed.
    
    >Also, it was under high-speed tracking that I did notice some image
    jitter,
    >making it that much harder to make out the shape of an orbiting object
    such
    >as Mir.
    
    To see a shape is fairly hopeless anyway unless one uses very high
    magnification
    uner perfect seeing conditions. I have noticed the jitter as well. It can
    be
    much reduced by carefully balancing the telescope mount. However, with only
    one counterweight not all the torques can be compensated.
    
    In summary, I have seen many objects (satellites and rockets) with the
    Skysensor
    which I would never have found without it. It probably isn't perfect (which
    instrument is ?), but it does a decent job for its price.
    
    Bruno Tilgner
    
    
    
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