Jean-François Coliac Feb 15, 2004
> At 21:10 2004-02-14 +0100, Jean Francois wrote:
> >
> >Hello the list,
> >
> >I thank you all for your answers, that bring me new questions
> >
> >First, I managed to access my asteroid database which was copied on
> the
> >hard drive and I added the file soft02bright.txt in the guide
> directory.
> >I noticed that the magnitude is not displayed for the asteroid that I
>
> >copied on my hard drive ( from the guide CD)
> >but I could see the magnitude of the asteroids that come from the
> >soft02bright.txt file (asteroid that are in opposition in 2004).
> >
> >Secondly, I wondered if it is possible to see graphically the
> asteroids
> >that come from the file inserted with ' Extra, Add asteroid from MPC
> '
> >and those that are in the asteroid directory or in the MPCorb.dat.
> >
> >It would be useful for example if we want to gaze only the asteroids
> >that are in opposition ( = soft02bright.txt )
> >
> >Finally, is it possible to remove the data which come from the file
> >inserted in ' Extra, Add asteroid from MPC '.
> >It seems to me that the only way to remove them is to enter the
> >comets.dat file and delete them.
>
>
> Hello Jean Francois.
>
> I don't have an answer to your question about the Magnitude of Ceres
> being
> 0.0, but here is some information about selecting a particular group
> of
> asteroids to be displayed in Guide. You might also want to look at
> the
> following URLs.
>
> http://www.projectpluto.com/update7.htm and
> http://www.projectpluto.com/hist_idx.htm
>
> which give lots of information about additions to Guide that you can
> use.
>
>
> -----------------------------------------------------------------------------
>
> (30 Jan 2000) Filtering of asteroids: Previously, Guide allowed you to
>
> filter asteroids solely on the basis of magnitude.
> You could tell it to drop asteroids fainter than, say, magnitude 15.4,
> but
> that was the limit of your ability to select which ones
> appeared.
>
> For most people, this limitation is not particularly troublesome. But
> it
> can be pleasant at times to filter asteroids on the basis
> of orbital parameters, and this is now possible. For example: suppose
> you
> wanted Guide to display only Jupiter Trojan
> asteroids. These are distinguished by having a semimajor axis (a) that
> is
> between 5.05 and 5.4 AU. To tell Guide to display
> only these asteroids, you would edit GUIDE.DAT and add this line:
>
> ASTFILTER=5.05 < a & a<5.4
>
> (This is worth giving a try, by the way... do it and turn asteroids
> 'On',
> and you can see two distinct clouds of Trojan-belt
> asteroids, 60 degrees ahead of and behind of Jupiter.)
>
> Alternatively, if you dislike text editors, you can hit Alt-J and get
> a
> little dialog box asking you to "Enter a test flag:" You can
> then enter the text ASTFILTER=5.05 < a & a<5.4, and click OK.
>
> You can also filter on the basis of limits in q (perihelion distance),
> Q
> (aphelion distance), e (eccentricity), i (inclination), P
> (orbital period), and d (distance from the earth). By combining these,
> you
> can define most of the major asteroid groups and
> families. For example, to define the Nysas, you would use:
>
> ASTFILTER=2.41<a & (a < 2.5) & (e > .12 & e < .21) & (1.5 < i & i <
> 4.3)
>
> (As the above indicates, you can use parentheses and spaces as you
> wish.)
> You can also filter on the basis of x (right
> ascension, in degrees) and y (declination, again in degrees.) The only
> real
> situation I can think of where you would want to do
> this is as follows. Let's say that you can't really image any
> asteroids
> below dec -20 (too close to your southern horizon). Let's
> say that the opposition point is currently at about RA=1h (15
> degrees), and
> you want to know which asteroids are within 25
> degrees of opposition. You could set up the following:
>
> ASTFILTER=(y>-20) & (x>350 | x<40)
>
> (The '|' means 'or'. I realize it's not as obvious as the '&' meaning
> 'and', though C programmers will find it a familiar usage.)
> Do this, fire up Guide, and you can go into 'Tables... List
> Asteroids', and
> get a list of asteroids in that area down to your
> desired limiting magnitude.
>
> Also, if you want to filter out Guide's built-in asteroids, using only
>
> those added with the 'Edit Comet/Asteroid Data' and 'Add
> MPC Comets/Asteroids', you would use this:
>
> ASTFILTER=b
>
> I don't actually envision many people making use of these filters, but
> they
> can be educational and (in rare cases) actually
> useful.
>
> ---------------------------------------------------------------------------
>
> ------
>
> Be very careful about deleting data from the "Add comets and asteroid"
> files.
>
> The number of objects in that file must match the number at the top of
> the
> file.
>
>
> Regards.
>
> Bob Elliott
>
>
>
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