Fixed equatorial grid with hour angle in decimal degrees

[liam1616]

Hi,

I want to display the fixed equatorial grid (with hour angle in decimal degrees, declination in decimal degrees) in Stellarium 24.2 using scripts. I managed to display the grid using: GridLinesMgr.setFlagFixedEquatorGrid(true).
However, the degrees are going from 0° (south) to 360°, instead, i wish to display the degrees from -180° (north) to 180°. Which command do I have to use? Thank you!

[gzotti]

Hour angles are defined as 0==upper culmination, counting hours from 0 to 24 hours. There are no negative values available.

[alex-w]

@liam1616 where are you from? country...

@gzotti maybe it's something local...

[liam1616]

@liam1616 where are you from? country...

@gzotti maybe it's something local...

I'm from Germany. Is there any possibility to change it in the script? I was thinking something like this:

setFlagFixedEquatorLabeled (const bool displayed)
Setter for displaying Fixed Equator line partition labels

But I don't know how to use it.

Thanks!

[alex-w]

Why you want to see from -180° to 180°?

[liam1616]

Why you want to see from -180° to 180°?

I need the program for educational purposes, so students should be able to determine the hour angle of the sun on their own. Therefore, I need to display the hour angle in decimal degrees. -180° should be north, -90° east, 0° south, ...

[alex-w]

But standard measurement of hour angles is 0..24 hours. Of course negative hours and angles possible for 12h standard of time (0..-12h and 0..12h).

@gzotti are use in Europeian countries 24h or 12h standard for equatorial coordinate system?

[10110111]

-180° should be north, -90° east, 0° south, ...

Shouldn't you be looking for azimuth rather than the hour angle? (This would still be 0°..360°, but at least you'd get this exact assignment of angles to cardinal directions, which the hour angle doesn't yield.)

[liam1616]

But standard measurement of hour angles is 0..24 hours. Of course negative hours and angles possible for 12h standard of time (0..-12h and 0..12h).

@gzotti are use in Europeian countries 24h or 12h standard for equatorial coordinate system?

In many (German) books the hour angle is defined from -180° to 180°...

[liam1616]

-180° should be north, -90° east, 0° south, ...

Shouldn't you be looking for azimuth rather than the hour angle? (This would still be 0°..360°, but at least you'd get this exact assignment of angles to cardinal directions, which the hour angle doesn't yield.)

I know what you mean, but im interested in the hour angle of the sun, and an ha of 0° should indicate midday (the directions aren't that important)

[liam1616]

@liam1616 where are you from? country...
@gzotti maybe it's something local...

I'm from Germany. Is there any possibility to change it in the script? I was thinking something like this:

setFlagFixedEquatorLabeled (const bool displayed) Setter for displaying Fixed Equator line partition labels

But I don't know how to use it.

Thanks!

Any ideas for this approach?

[alex-w]

A quick search in few French and German books - everything using 24h standard for an equatorial system (books from current century)

[alex-w]

In many (German) books the hour angle is defined from -180° to 180°...

Any example please

[gzotti]

The hour angle is a fundamental ingredient for equatorially mounted telescopes since probably the 1700s, i.e. uncomputerized, non-electronic. Scales on Equatorial mounts in many observatories of the 19th and 20th century, Zeiss telescopes, etc. are labelled 0..24 (hours). Computing it from sidereal time and right ascension is a trivial enough operation to train beginners with (or a first hurdle that separates amateur astronomers from touchscreen pushers). RA and HA are conventionally given in positive hours 0...24 (of 60 minutes of 60 seconds), not degrees, at least in the tradition of 19th-century German speaking Central Europe which has evolved since antiquity. One degree movement along the equator means 4 minutes of (sidereal) time have elapsed. It is however possible that astronomical navigation schools taught using a preference for degrees and even negative hour angles, this is visible in the Nautical Stars plugin where Local Hour Angle is available under the LHA key, however again counted 0...360°.

@liam1616 I am not aware of German textbooks where hour angle would be counted negative. Please give two titles.

Yes, working with angles or even hours makes computing slightly more difficult for primary schoolers of the tiktok generation, but in the age of programmable pocket calculators or lately spreadsheet programs it should not pose a significant problem, or just discuss it with your local LLM. Here the larger difficulty is the degree/radians question.

If there is really need for setting flag number 895, we can add this. My first proposal would be to add it in the NavStar plugin to affect the LHA infotext only.

[liam1616]

In many (German) books the hour angle is defined from -180° to 180°...

Any example please

Wikipedia
https://de.m.wikipedia.org/wiki/Stundenwinkel#:~:text=23h%2056m%20(gleich,an%20als%20der%20eines%20Sterns.

[alex-w]

In many (German) books the hour angle is defined from -180° to 180°...

Any example please

Wikipedia https://de.m.wikipedia.org/wiki/Stundenwinkel#:~:text=23h%2056m%20(gleich,an%20als%20der%20eines%20Sterns.

I meant any textbook title

[liam1616]

In many (German) books the hour angle is defined from -180° to 180°...

Any example please

Wikipedia https://de.m.wikipedia.org/wiki/Stundenwinkel#:~:text=23h%2056m%20(gleich,an%20als%20der%20eines%20Sterns.

I meant any textbook title

Zenkert - Faszination Sonnenuhr (2000)

[liam1616]

The hour angle is a fundamental ingredient for equatorially mounted telescopes since probably the 1700s, i.e. uncomputerized, non-electronic. Scales on Equatorial mounts in many observatories of the 19th and 20th century, Zeiss telescopes, etc. are labelled 0..24 (hours). Computing it from sidereal time and right ascension is a trivial enough operation to train beginners with (or a first hurdle that separates amateur astronomers from touchscreen pushers). RA and HA are conventionally given in positive hours 0...24 (of 60 minutes of 60 seconds), not degrees, at least in the tradition of 19th-century German speaking Central Europe which has evolved since antiquity. One degree movement along the equator means 4 minutes of (sidereal) time have elapsed. It is however possible that astronomical navigation schools taught using a preference for degrees and even negative hour angles, this is visible in the Nautical Stars plugin where Local Hour Angle is available under the LHA key, however again counted 0...360°.

@liam1616 I am not aware of German textbooks where hour angle would be counted negative. Please give two titles.

Yes, working with angles or even hours makes computing slightly more difficult for primary schoolers of the tiktok generation, but in the age of programmable pocket calculators or lately spreadsheet programs it should not pose a significant problem, or just discuss it with your local LLM. Here the larger difficulty is the degree/radians question.

If there is really need for setting flag number 895, we can add this. My first proposal would be to add it in the NavStar plugin to affect the LHA infotext only.

Thank you. I was just looking for a possible quick fix, you dont need to change the program.

[gzotti]

OK, I think I have Zenkert, must check. But this is very specialized literature for another related field. Here a single author can use his own convention. Waiting for a second title, preferrably a widely available astronomical textbook, or identified photo of an equatorial mount in a professional observatory labelled in -180...180°.

The WP entry does not count. It is written by whoever wanted to write it and has no reference.

Your earlier comment about -180=north which @10110111 answered really makes it unclear whether you mean hour angle or azimuth. An hour angle of -180° (trivially also known as 12h) is lower culmination, be it north or south.

[liam1616]

OK, I think I have Zenkert, must check. But this is very specialized literature for another related field. Here a single author can use his own convention. Waiting for a second title, preferrably a widely available astronomical textbook, or identified photo of an equatorial mount in a professional observatory labelled in -180...180°.

The WP entry does not count. It is written by whoever wanted to write it and has no reference.

Your earlier comment about -180=north which @10110111 answered really makes it unclear whether you mean hour angle or azimuth. An hour angle of -180° (trivially also known as 12h) is lower culmination, be it north or south.

Astronomie: Die kosmische Perspektive (Benn

[liam1616]

OK, I think I have Zenkert, must check. But this is very specialized literature for another related field. Here a single author can use his own convention. Waiting for a second title, preferrably a widely available astronomical textbook, or identified photo of an equatorial mount in a professional observatory labelled in -180...180°.

The WP entry does not count. It is written by whoever wanted to write it and has no reference.

Your earlier comment about -180=north which @10110111 answered really makes it unclear whether you mean hour angle or azimuth. An hour angle of -180° (trivially also known as 12h) is lower culmination, be it north or south.

Astronomie: Die kosmische Perspektive (Bennett et al., 2020), page 134: if a star is going to pass the meridian in 1h, its hour angle is -1h or 23h

So both ways seem possible. Can we add the feature?

[gzotti]

And how many text books did you now check which count 0...24 hours?
When will beginner textbooks appear which immediately start with angles in -2π..2π, all data in normalized vectors and rotation matrices, ...

OK, registered. One user wants feature flag 895. No, 896, the previous number was just reserved..., But it's super low priority.

[liam1616]

Thank you. When will it be available?

[gzotti]

When it's done. By then you will likely have learned to think in positive hours like the rest of us.

[gzotti]

If you close this, we will forget and never implement it.

[liam1616]

Oh sry, didn't know that, thanks.