From: F. C. <fab...@go...> - 2008-06-27 10:26:30
|
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 |
From: Johannes G. <joh...@gm...> - 2008-06-27 12:15:38
|
> 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 -- GMX startet ShortView.de. Hier findest Du Leute mit Deinen Interessen! Jetzt dabei sein: http://www.shortview.de/wasistshortview.php?mc=sv_ext_mf@gmx |
From: F. C. <fab...@go...> - 2008-06-27 13:35:24
|
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 > > -- > GMX startet ShortView.de. Hier findest Du Leute mit Deinen Interessen! > Jetzt dabei sein: http://www.shortview.de/wasistshortview.php?mc=sv_ext_mf@gmx > > ------------------------------------------------------------------------- > Check out the new SourceForge.net Marketplace. > It's the best place to buy or sell services for > just about anything Open Source. > http://sourceforge.net/services/buy/index.php > _______________________________________________ > Stellarium-pubdevel mailing list > Ste...@li... > https://lists.sourceforge.net/lists/listinfo/stellarium-pubdevel > |
From: Johannes G. <joh...@gm...> - 2008-06-27 14:00:26
|
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. 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. 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 > > > > -- > > GMX startet ShortView.de. Hier findest Du Leute mit Deinen Interessen! > > Jetzt dabei sein: > http://www.shortview.de/wasistshortview.php?mc=sv_ext_mf@gmx > > > > > ------------------------------------------------------------------------- > > Check out the new SourceForge.net Marketplace. > > It's the best place to buy or sell services for > > just about anything Open Source. > > http://sourceforge.net/services/buy/index.php > > _______________________________________________ > > Stellarium-pubdevel mailing list > > Ste...@li... > > https://lists.sourceforge.net/lists/listinfo/stellarium-pubdevel > > > > ------------------------------------------------------------------------- > Check out the new SourceForge.net Marketplace. > It's the best place to buy or sell services for > just about anything Open Source. > http://sourceforge.net/services/buy/index.php > _______________________________________________ > Stellarium-pubdevel mailing list > Ste...@li... > https://lists.sourceforge.net/lists/listinfo/stellarium-pubdevel -- Ist Ihr Browser Vista-kompatibel? Jetzt die neuesten Browser-Versionen downloaden: http://www.gmx.net/de/go/browser |
From: F. C. <fab...@go...> - 2008-06-30 08:47:06
|
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 >> > >> > -- >> > GMX startet ShortView.de. Hier findest Du Leute mit Deinen Interessen! >> > Jetzt dabei sein: >> http://www.shortview.de/wasistshortview.php?mc=sv_ext_mf@gmx >> > >> > >> ------------------------------------------------------------------------- >> > Check out the new SourceForge.net Marketplace. >> > It's the best place to buy or sell services for >> > just about anything Open Source. >> > http://sourceforge.net/services/buy/index.php >> > _______________________________________________ >> > Stellarium-pubdevel mailing list >> > Ste...@li... >> > https://lists.sourceforge.net/lists/listinfo/stellarium-pubdevel >> > >> >> ------------------------------------------------------------------------- >> Check out the new SourceForge.net Marketplace. >> It's the best place to buy or sell services for >> just about anything Open Source. >> http://sourceforge.net/services/buy/index.php >> _______________________________________________ >> Stellarium-pubdevel mailing list >> Ste...@li... >> https://lists.sourceforge.net/lists/listinfo/stellarium-pubdevel > > -- > Ist Ihr Browser Vista-kompatibel? Jetzt die neuesten > Browser-Versionen downloaden: http://www.gmx.net/de/go/browser > > ------------------------------------------------------------------------- > Check out the new SourceForge.net Marketplace. > It's the best place to buy or sell services for > just about anything Open Source. > http://sourceforge.net/services/buy/index.php > _______________________________________________ > Stellarium-pubdevel mailing list > Ste...@li... > https://lists.sourceforge.net/lists/listinfo/stellarium-pubdevel > |
From: Johannes G. <joh...@gm...> - 2008-06-30 20:59:32
|
On 2008.06.30 10:47:02 CEST, Fabien Chéreau wrote: > 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. I have written nonsense. sideral time is the hour angle of the vernal point not the meridian. the hour angle of the meridian is 0. > > 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. Funny. What decent scope did you use? The first scope of a friend of mine was a 10cm Tasco Newtonian. With a very wobbly German equatorial mount, tiny setting circles, and no electrical motor for compensation of the earths rotation. Instead you could set it according to declination and hour angle. This was 25 years ago, we were kids 13 years of age. We did never use the sidereal time/hour-angle/Ra for pointing it somewhere. Just locked through it and used the finderscope. It was great fun. Some months later I also got a telescope (Celestron C90), which was somewhat smaller (9cm), but already had electric power for compensating earth's rotation. And nice setting circles. The Ra setting circle moved around together with the Ra-Motor of the scope. You need no sidereal time and hour angles for this, just Ra/Dec. Very conveniant. Johannes |
From: F. C. <fab...@go...> - 2008-07-01 06:19:48
|
It was in OHP (Observatoire de Haute Provence). A 80cm diameter scope. It is a very old one used before by professional astronomers. In each telescope rooms there was a big clock showing local sideral time and we always had to subtract the RA of an object we wanted to observe to the sideral time, which was pretty tedious (using HH:MM:SS). I don't know who really need to use that today, but I was asked several times (usually from club members), so I guess there must be still some old scopes like that used by clubs. Fabien On Mon, Jun 30, 2008 at 10:59 PM, Johannes Gajdosik <joh...@gm...> wrote: > On 2008.06.30 10:47:02 CEST, Fabien Chéreau wrote: >> 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. > > I have written nonsense. sideral time is the hour angle of the vernal > point not the meridian. > the hour angle of the meridian is 0. > >> >> 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. > > Funny. What decent scope did you use? The first scope of a friend of > mine was a 10cm Tasco Newtonian. With a very wobbly German equatorial > mount, tiny setting circles, and no electrical motor for compensation > of the earths rotation. Instead you could set it according to > declination and hour angle. This was 25 years ago, we were kids 13 > years of age. We did never use the sidereal time/hour-angle/Ra for > pointing it somewhere. Just locked through it and used the finderscope. > It was great fun. > > Some months later I also got a telescope (Celestron C90), which was > somewhat smaller (9cm), but already had electric power for compensating > earth's rotation. And nice setting circles. The Ra setting circle moved > around together with the Ra-Motor of the scope. You need no sidereal > time and hour angles for this, just Ra/Dec. Very conveniant. > > Johannes > > ------------------------------------------------------------------------- > Check out the new SourceForge.net Marketplace. > It's the best place to buy or sell services for > just about anything Open Source. > http://sourceforge.net/services/buy/index.php > _______________________________________________ > Stellarium-pubdevel mailing list > Ste...@li... > https://lists.sourceforge.net/lists/listinfo/stellarium-pubdevel > |