<p>In the geocentric solar ecliptic (GSE) system of coordinates, the position of the Moon is described by its longitude and latitude. The former is, with great accuracy, the angular distance between the sun and the Moon, and thus can be determined by the Moon phase. If it is totally new moon, the longitude is 0°, and if it is a full moon, the longitude is 180°, and, with some geometry, the longitude can be determined for any phase and, therefore, with simple equipment, such as a camera.</p>
<p>My question is: Is there also a simple way to determine the Moon's latitude, that is, it's angular distance to the ecliptic?</p>

CC BY-SA 4.0
2022-09-03T23:09:20.377Z
Wouldn't that just be the GSE latitude, by its very definition?
Greg Miller
CC BY-SA 4.0
2022-09-03T23:18:49.040Z
That is precisely what I am asking how to determine
WordP
CC BY-SA 4.0
2022-09-04T00:04:54.327Z
@GregMiller OP gets (a good approximation to) the GSE longitude by equating it with lunar phase, and (I think) is looking for a similarly simple way to get GSE latitude. It's going to have to be something that takes into account (in a simple, sine-wavy way) the [precession](https://en.wikipedia.org/wiki/Orbit_of_the_Moon#Precession) of the [lunar nodes](https://en.wikipedia.org/wiki/Lunar_node) cf. [Lunar standstill](https://en.wikipedia.org/wiki/Lunar_standstill) so it's going to have an 18.6 year cycle to it.
uhoh
CC BY-SA 4.0
2022-09-04T09:37:17.637Z
How accurate do you need to be?  In estimating longitude from phase, you can probably be quite accurate when the moon is about half illuminated because then the terminator moves quickly.  It is much harder to determine longitude at the full moon as the terminator is almost impossible to see, and moves very slowly. So would ±5degrees be considered to be sufficiently accurate in the determination of latitude?
James K
CC BY-SA 4.0
2022-09-04T18:39:26.047Z
In the case of longitude, an error of 5 degrees is not very significant, but 5 degrees in the latitude is almost 100% of error, since the inclination of the moon's orbit is about 5.1 degrees
WordP
CC BY-SA 4.0
2022-09-04T19:39:43.020Z
Are you talking about actual geocentric measurement through observation, e.g. photography (as opposed to calculation which is now pretty accessible at high precision thanks to the ephemerides available through JLP and the Astronomical Almanc online)? (Geocentric measurement with precision is not so simple, you have to allow for effects of refraction and parallax. After that, the moon's latitude also affects its apparent elongation from the sun. The apparent elongation also never exactly reaches 0d or 180d because of the effects of latitude at conjunction and opposition.)
terry-s
CC BY-SA 4.0
2022-09-04T20:28:21.090Z
Yes. I was able to have an error of about 1 degree when determining the longitude from a high quality picture of the Moon, by taking the ratio of the bright pixels to the total area of the Moon in pixels - so it would be great to have another method for measuring the latitude with simple equipment. As you said, there are many factors that go into account to precisely measure the latitude and longitude, but since I am considering an amateur context, it doesn't need to be extremely precise.
WordP
<observational-astronomy><the-moon><amateur-observing>
How to measure the latitude of the moon?
WordP
# How to measure the latitude of the moon?

(Asked by: username_0 on 2022-09-03)

In the geocentric solar ecliptic (GSE) system of coordinates, the position of the Moon is described by its longitude and latitude. The former is, with great accuracy, the angular distance between the sun and the Moon, and thus can be determined by the Moon phase. If it is totally new moon, the longitude is 0°, and if it is a full moon, the longitude is 180°, and, with some geometry, the longitude can be determined for any phase and, therefore, with simple equipment, such as a camera.

My question is: Is there also a simple way to determine the Moon's latitude, that is, it's angular distance to the ecliptic?

**Tags:** observational-astronomy, the-moon, amateur-observing

> **Comments:**
> **username_1**: Wouldn't that just be the GSE latitude, by its very definition?  
> **username_0**: That is precisely what I am asking how to determine  
> **username_2**: @GregMiller OP gets (a good approximation to) the GSE longitude by equating it with lunar phase, and (I think) is looking for a similarly simple way to get GSE latitude. It's going to have to be something that takes into account (in a simple, sine-wavy way) the [precession](https://en.wikipedia.org/wiki/Orbit_of_the_Moon#Precession) of the [lunar nodes](https://en.wikipedia.org/wiki/Lunar_node) cf. [Lunar standstill](https://en.wikipedia.org/wiki/Lunar_standstill) so it's going to have an 18.6 year cycle to it.  
> **username_3**: How accurate do you need to be?  In estimating longitude from phase, you can probably be quite accurate when the moon is about half illuminated because then the terminator moves quickly.  It is much harder to determine longitude at the full moon as the terminator is almost impossible to see, and moves very slowly. So would ±5degrees be considered to be sufficiently accurate in the determination of latitude?  
> **username_0**: In the case of longitude, an error of 5 degrees is not very significant, but 5 degrees in the latitude is almost 100% of error, since the inclination of the moon's orbit is about 5.1 degrees  
> **username_4**: Are you talking about actual geocentric measurement through observation, e.g. photography (as opposed to calculation which is now pretty accessible at high precision thanks to the ephemerides available through JLP and the Astronomical Almanc online)? (Geocentric measurement with precision is not so simple, you have to allow for effects of refraction and parallax. After that, the moon's latitude also affects its apparent elongation from the sun. The apparent elongation also never exactly reaches 0d or 180d because of the effects of latitude at conjunction and opposition.)  
> **username_0**: Yes. I was able to have an error of about 1 degree when determining the longitude from a high quality picture of the Moon, by taking the ratio of the bright pixels to the total area of the Moon in pixels - so it would be great to have another method for measuring the latitude with simple equipment. As you said, there are many factors that go into account to precisely measure the latitude and longitude, but since I am considering an amateur context, it doesn't need to be extremely precise.  

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## 0 answers

