Re: Satobs help-Scope and imaging recommendations

From: Björn Gimle (b_gimle@algonet.se)
Date: Mon Apr 21 2003 - 08:49:34 EDT

  • Next message: Björn Gimle: "Re: Distribution of Geosynchronous Satellites"

    I have very similar requirements like yours, and I welcome comments to my
    own views. I also anticipate using it to 99% for Earth-orbiting objects,
    excluding Moon (except for transits). I was intrigued by Greg Roberts'
    success with CoSaTrak, but that is only available as freeware program +
    instructions. As I am not capable of locating and assembling the
    mechanical and electronic parts, I decided in 2001 to get a Meade ETX-70
    AT with their Autostar controller. Celestron NexStar has similar cost and
    capabilities, but there seems to be more activity with updates etc. from
    Meade (although I am also reading selectively). What stopped me initially
    was the first comparative review in S&T May 2001, saying that "GOTO"
    RA/Dec often consistently jumped to the wrong position, and that I never
    got any info from manufacturers against that, nor any info on how much
    piggy-back equipment the mechanisms could support.
    >
    1. ETX-70 (60) and NexStar 80 are in the $300-$500 range, 114 mm versions
    slightly more. After I got a small inheritance, and read lots of positive
    reviews, I ordered a LXD-55 8" f/4 (not yet delivered). With the success
    of Rainer Kracht, Greg etc. I feel I could have stayed with budget
    models.
    
    2. They do.
    
    3. AutoStar has a programming interface (subset of LX200's), I assume
    NexStar also has. They need a serial cable, so if you are close to the
    scope that will do. Otherwise, a simple computer near the scope with
    Ethernet cable to your indoors computer can do it. I believe the existing
    TLE programs just allow slight corrections in time, and don't correct the
    track if a satellite is early or late. So I think I will have to write a
    program to search for such objects.
    
    4. I will probably switch to digital, when I have sorted out
    price/performance issues, and postprocessing alternatives.
    >
    6. For visual work, you should have as short focal length as possible
    (low f-ratio, f/6 to f/3), and only enough magnification to use the full
    aperture, to get a FOV much larger than pointing+TLE accuracy. ETX-x0AT
    are 350 mm, NexStar 80GT 400 mm, LXD-55 6" 760 mm, 8" 810 mm. These are
    refractors and newtonians (beware of the Schmidt-Maksutov-Cassegrains
    with much longer focal lengths). Also note that binocular view may gain
    some 0.5-1 magnitudes over a monocular the same size, but a binocular
    eyepiece will cost many hundred dollars.
    
    http://www.lxd55.com/Reviews.html
    http://www.celestron.com/nexstrgen.htm
    http://www.meade.com/catalog/etx/etx70at.html
    http://www.meade.com/catalog/lxd55/lxd55_series.html
    
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