Re: [Stellarium-pubdevel] Utility of equ of date position

[F. C. <fab...@go...>]

On Fri, Jun 27, 2008 at 4:00 PM, Johannes Gajdosik
<joh...@gm...> wrote:
> Well, yes. When you have a non-computerized telescope with equatorial mount and setting circles you should set it according to these values.
>
>> displaying the sideral time for this object would be very
>> useful for amateur astronomers.
>
> On the other hand I see no application of sideral time, and although I am an amateur astronomer I never used it in my life. Moreover the sideral time has no connection with a specific object, it is just the hour angle of the meridian.

What I meant is hour angle for an object (as defined here
http://en.wikipedia.org/wiki/Hour_angle)

> For those with the very old scopes (like in antique observatories) you could display the hour angle of specific objects plus the current sidereal time plus declination of date.

Well last time I used a decent telescope it's what I had to give in.
And it was not an antique one. And many other people asked for that,
so I guess it is still quite used.

Fabien

> Johannes
>
>
> -------- Original-Nachricht --------
>> Datum: Fri, 27 Jun 2008 15:35:21 +0200
>> Von: "Fabien Chéreau" <fab...@go...>
>> An: "Stellarium developers public mailing list" <ste...@li...>
>> Betreff: Re: [Stellarium-pubdevel] Utility of equ of date position
>
>> Of course I was aware. What you say is the reason why I asked. People
>> definitely want to visualize the precession, and for this the grid is
>> very good (one J2000 vs one at the current equinox). I am not sure
>> that for understanding this concept, they need to see the real textual
>> value of it.
>> Do you think this textual value can be used for other reasons? Like
>> when using some devices?
>> Fabien
>>
>> On Fri, Jun 27, 2008 at 2:15 PM, Johannes Gajdosik
>> <joh...@gm...> wrote:
>> >> Datum: Fri, 27 Jun 2008 12:26:28 +0200
>> >> Von: "Fabien Chéreau" <fab...@go...>
>> >> An: "Stellarium developers public mailing list"
>> <ste...@li...>
>> >> Betreff: [Stellarium-pubdevel] Utility of equ of date position
>> >
>> >> Dear all,
>> >> I am wondering whether the equ of date info for selected object is
>> >> really useful. Most of the time the position of an object is given in
>> >> J2000, not in equatorial for the given epoch.
>> >> conversely, displaying the sideral time for this object would be very
>> >> useful for amateur astronomers.
>> >> Can I go with the replacement?
>> >> Fabien
>> >
>> > When you go to a different home planet, or to a different epoch (2000
>> years ago) you will see the diffenrence between "equatorial of date" and
>> J2000=IRCF. When you kick the "equatorial of date" you should also kick the
>> equatorial grid and keep the J2000 grid only. Then stellarium looses the
>> ability to show that J2000 and equatorial are not the same.
>> >
>> > Sorry for this explanation. Were you aware of this or did I tell you new
>> stuff?
>> >
>> > However it is up to you if you want to keep or remove it. My opinion is
>> biased and does not count, because I introduced it.
>> >
>> > Johannes
>> >
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