Re: [guide-user] Re: colors in horizon.dat

Bernd Klemt Feb 5, 2018

Hello Bill,

thank you for your investigation. I will try the new possibilities.

Clear skies

> Hi Rudi, Bernd,
> First off: Rudi, Guide does have a built-in 'horizon.dat' and
> 'objects.dat'. You won't see the files in the Guide folder, though,
> until _after_ you have turned on horizon objects and they've been
> displayed. (And they don't get displayed unless your viewpoint is
> on the surface of the earth; the moon and Mars have their own horizon
> files, and the geocenter has no horizon file.)
> You're right about the colors for circles. (The comments you found
> are for TDF files; none of those coloring tricks work in the horizon
> drawing code.)
> In 'horizons.dat' and 'objects.dat', circle colors can only be set
> as index values from 0 to 15. Colors for filled areas and polylines
> can be set as red/green/blue decimal values (which is no longer a
> common way of specifying colors, and hasn't been for some years now.)
> I've posted a fix for this. Download
> (about 620 KBytes) and unZIP it there. It'll overwrite some existing
> files, updating both Guide and the horizon and object files.
> With this, colors for 'f' (filled objects), 'c' (circles), and 'l'
> (polylines) can be specified as six-character hexadecimal codes.
> '996633' should come out as a light brown.
> You'll also see a band at 60 degrees above the horizon (roughly).
> This _could_, in theory, have been done by adding
> c 996633
> 0 90 30
> ("draw a circle with RGB color #996633, centered on azimuth 0,
> altitude 90, with a radius of 30 degrees"). However, projection
> effects will make that not all that close to showing an altitude
> of 60 degrees. The circle drawing really only works for circles
> less than about ten degrees across.
> So instead, I put this line into 'horizons.dat' :
> i alt_mark 0 60 1
> If you look in 'objects.dat', you'll see that an 'alt_mark' consists
> of six 60-degree segments, each of which draws six ten-degree pieces.
> Each of those pieces consists of two triangles, which make a 10x10
> degree square. (Well, ten degrees wide in azimuth... at an altitude
> of sixty degrees, that's compressed by a factor of two.)
> Also, note that for the purposes of these files, an altitude of
> zero means "at your visible horizon", which is affected by refraction
> and your height above sea level. You may have to change the '60'
> in the above line to get the altitude marker where you really want it.
> And a final comment: Bernd, you mentioned in a private e-mail
> that you have at least ten different horizon files for different places,
> and would like a way to swap them around. Not to raise your hopes too
> much, but it occurs to me that the most sensible way of doing so would
> be to have lines in 'horizon.dat' that would say
> L -69.9 +44.01 bowdoinh.txt bhm_objs.txt
> ...i.e., "if you are at longitude 69.9 West, latitude 44.01 North,
> stop processing this horizons.dat file; switch instead to bowdoinh.txt,
> getting your objects from bhm_objs.txt'."
> You could have a series of such lines -- at least ten, in your
> case. If Guide read through all ten and effectively said, "No,
> that's not where we are", it would continue and just display the
> default horizon.
> -- Bill
> On 2018-02-02 06:51, chasseurdesgalaxies@... [guide-user] wrote:
> >
> >
> > Hi Bernd,
> >
> > I tried to reproduce your problem, because I am also interested to have a
> "fixed" 60° line around the zenith. (I have a "workaround" but it moves
> position, when i move the map from the zenith position. I will come back on
> this).
> >
> > BUT, I don't even have ahorizon.dat file in my Guide folder?? (Despite the
> fact that I have switched on thea horizon line and can switch it off and change
> color).
> >
> > Found this (first link) and installed the horizon.dat file :
> ,
> >
> > ... but it doesn't work for me either !??
> >
> > Here, , somewhere in the middle of
> the text under "Defining your own custom .TDF symbols" it is said as follows:
> >
> > "It used to be that color was always set with lowercase 'c' followed by a
> number from 0 to 15. That was a legacy of the old DOS days, in which objects
> could only have one of a palette of sixteen colors. This is still available for
> purposes of keeping Guide backward-compatible, but Guide 8.0 can set "full
> colors" with an uppercase 'C'.
> >
> > The easy way to set this is to create your symbol with either a 'c' or
> 'C'-type color selected basically at random. Then fire up Guide, click on an
> object in the dataset, and then on "Display", and then on the color button.
> Select a new color and click OK, and the symbol will be rewritten to use the new
> color".
> >
> > Sorry, I can't help you further. (What is strange is, that the last word in
> the last quoted link is saying "useless" ??)
> >
> > What I am doing is creating an aperture cercle (in "Settings \ Tips, Grids,
> ect") of 60° (in my case). By setting the cercle to 120 ° (you need to add the
> degrees sign (°) behind the number, I have a cercle of 30° above the horizon).
> And with this cercle you can change color as you want.
> >
> > But, as I said, there is the drawback that, if you move the map from the exact
> zenith position, the cercle follows and does not stay around the zenith
> position.
> >
> > Rudi

Bernd Klemt

Sternwarte Herne, MPC code A18
Herne, Germany

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