Hi Bernd,

> Hello Bill,
>
> If you decide to observe remember that your Planetarium program will
> not be able to give you reliable ephemeris...

> can you tell me, if the statement in the first sentence is right? Will
> Guide not be able to show the position of such a near asteroid to an
> accuracy of say 1'?

Sadly, that first sentence probably _is_ just about right. (At least
for Guide; I can't speak for other programs.) The problem is that
perturbations are not included (at least, not yet) in the ephemerides.

The simplest fix is to use elements with an epoch that is closer to
the present. You'll then have an exactly right ephemeris at the time of
epoch, which will degrade slowly for times distant from that. The
following should fill the bill:

Orbital elements:
2011 GP59
Perihelion 2011 Jul 20.318897 TT = 7:39:12 (JD 2455762.818897)
Epoch 2011 Apr 15.0 TT = JDT 2455666.5 Earth MOID: 0.0028 Ve: 0.0584
M 241.864655 (2000.0) P Q
n 1.226502256 Peri. 320.383943 0.962432051 0.263982819
a 0.864351682 Node 24.533221 -0.193659111 0.831409617
e 0.26076462 Incl. 8.802701 -0.190317352 0.488948994
P 0.80/293.51d H 24.4 G 0.15 q 0.638959337 Q 1.089744026
From 174 observations 2011 Apr. 8-13; mean residual 0".343.

Save this e-mail to a text file, and use Extras... Asteroid/Comet Options.
Click on "Add MPC Comets/Asteroids". You'll see various options for automatic
downloading of comet/asteroid data. But you'll see, at the bottom, an
option to add elements from a file. Click on that, and select the text
file in which you saved this e-mail.

Guide will then dig through the text, find the above "Orbital elements:"
line, recognize it as the start of orbital element data in MPC eight-line
format, and extract the data. You'll then be able to find 2011 GP59.
The perturbations over the next few days won't be enough to be a problem.

(Dunno where that data about "you can't use your planetarium program"
came, but you might want to pass along the above elements. The method of
using an epoch close to the observing time will work with other software
as well, of course.)

-- Bill