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    Re: Tinyac on Linux
    From: Paul Hirose
    Date: 2017 Apr 4, 21:45 -0700

    I'm no help regarding Tinyac installation on Linux, but the current
    release of my Lunar4 software has several advantages over Tinyac
    • The Lunar4 "auto delta T" feature is based on a lookup table like
    Tinyac, but outside the table range it implements a set of polynomial
    approximations to cover any date within reason. By contrast, the Tinyac
    table limit has already been exceeded, so any attempt to use its auto
    delta T for dates now and in the future throws in an exception. (Both
    programs allow manual delta T input.)
    • Both programs will convert the JPL ephemeris ASCII download format to
    the binary file format necessary for computation. To perform this
    conversion the program must know the record length of the ephemeris.
    E.g., record length is 1456 for the DE406 but 2036 for DE422. Tinyac
    gets this from an internal table which cross references the DE number to
    record length. But that table doesn't include the latest ephemerides.
    Lunar4 eliminates the lookup table and detects record length automatically.
    • Lunar4 has an internal star catalog (a subset of the second reduction
    of the Hipparcos data) complete to magnitude 3, plus manual input of any
    star. Tinyac has only the latter.
    • Tinyac has a minor refraction discontinuity at about 15° altitude when
    it shifts between the low and high altitude formulas. Lunar4 implements
    an altitude zone in which one model linearly fades out as the other
    fades in. Both programs can display unrefracted altitude if you prefer
    to apply refraction yourself.
    • In the latter case, you need the "station pressure": the air pressure
    at the observer. In the US, at least, what is called "barometric
    pressure" is actually altimeter setting. If the user is a significant
    height above sea level, a formula must be applied to convert height and
    altimeter setting to station pressure. Lunar4 does that for you, and
    even gives the refractive index of the air.
    • Both programs have inputs for deflection of the vertical, but only
    Lunar4 applies the corrections properly.
    The main advantage of Tinyac is its plethora of coordinate systems.
    Also, Tinyac needs only v. 2.0 of the .NET Framework while Lunar4 needs
    4.5 (I think), so the former may be easier to get going on Linux.
    Otherwise, I believe Lunar4 is a superior program.

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