Re: sats and scopes

From: Bruno Tilgner (
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
    >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
    >it stops and waits for you to command it to flip itself to the other half
    >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
    is crossed.
    >Also, it was under high-speed tracking that I did notice some image
    >making it that much harder to make out the shape of an orbiting object
    >as Mir.
    To see a shape is fairly hopeless anyway unless one uses very high
    uner perfect seeing conditions. I have noticed the jitter as well. It can
    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
    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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