Hi Oliver,

Thank you very much for your fast and detailed answer.

I was aware of the two messages you mentioned, but I think (may be I am wrong) that user horizon and goto process are independant from one another.

My current horizon, which is the "normal" one, fits perfectly with my site. If I changed it by a -1 deg, Guide would display a wrong horizon. Moreover, If I did that, how could I define an other horizon near to the zenith?
Needless also to say that to display all the sky except a small part near to the zenith, as being "below horizon" is "Not the sort of solution that leaps out at you" as Bill says!

In other words, the trubble comes, at least in my mind, from the goto process, and not of the horizon settings.

But I thank you again for the length and the precision of your answer, and I wait for what Bill is thinking of.

Regards,

Bertrand

----- Original Message -----
From: Oliver Kloes
To: guide-user@yahoogroups.com
Sent: Saturday, March 04, 2006 12:54 PM
Subject: RE: [guide-user] goto


Hi Bertrand,

Your wishes were familiar to me and so I searched the guide-user archive.

> The first one refers to stars very near to horizon.
> Normally, Guide does not allow to go to a star below horizon.
> This seems true and wrong. A star can be theoretically below horizon, but
> visible thanks to refraction. I think Guide does not take this fact into
> account, and, in the reality, one can't go to such a star.
> If it is difficult to manage such a modification, a work around would be
> to be able to go to a star up to, say, one degree below horizon.

I found a mail from Bill in the year 2003:

****
I've just revised Guide so you can edit 'guide.dat' and add,
say,

USER_HORIZON=30

to set the "horizon" to be at altitude 30 degrees. Objects
will rise at correspondingly later times and set earlier; the
dec limits at which objects become circumpolar and "never
visible" will rise 30 degrees. You'll see this the next time I
post an update.
****

So this should work with a negative altitude too?
Why not try to set the user horizon to -1. Does it work?


> The second improvement would be to prevent to go to a given direction, or
> altitude.
> The purpose is to prevent serious "injuries" to big devices placed at the
> rear of fork mounted scopes as Meade, Celstron, etc, when you slew to a
> point near to zenith.
> The way would be for instance to give Guide users the ability to fix a
> maximum value for the altitude beyond which Guide wouldn't accept to slew.
> Same thing could be done for azimut, if the scope is in danger bcause of
> an obstacle (I think, for instance, about walls of balconies!)

I think this was discussed before too. But I found message 2435 about this
only:

****
... about having some sort of "horizon" limit for telescope
control: as admittedly happens too frequently in Guide, there is
a way to do this, but it is not at all obvious. You can edit
HORIZON.DAT and add lines resembling the following:

f 18 48 0 0 ; altitude cap
0 67
20 67
40 67
60 67
80 67
100 67
120 67
140 67
160 67
180 67
200 67
220 67
240 67
260 67
280 67
300 67
320 67
340 67

The above would cause Guide to draw an eighteen-point polygon
that loops around the zenith, at altitude 67 degrees (obviously,
this can be readily changed) in a "danger! alert!"-suggestive red.

Not the sort of solution that leaps out at you, I realize!

My next project in Guide is going to be ripping out the current
telescope control system and rewriting it. One idea suggested long
ago was to have Guide warn you if a scope motion would go below the
user-defined horizon. (You can add in mountains and such on the
horizon, without much difficulty; see the end of HORIZON.DAT for
details.) I should be able to at least leave that option open as I
do the rewriting of scope control... if I do this, you would also
get a warning when attempting to slew into the above "cap", or
any piers, etc. added to the "horizon".
****

I don't know if there is a solution available already.


Regards,

Oliver



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