Jokodo
Veteran Member
Any (amateur) astronomers?
Alright, I have this pipe dream to one day measure the moon's distance through the diurnal parallax method with my kid as soon as he's old enough to understand the math involved (basic trig, which isn't my strongest suit either so I'd rather wait till someone who does so for a living teaches him). It's probably going to be 10 years before that happens, but I'm currently in little position to make plans otherwise, why not make plans about this?
The method is fairly simple in theory: You measure the moons position against the background stars four hours before midnight in three consecutive nights, and in the second night you also measure it four hours *after* midnight. The difference from the expected position is due to your own movement as the earth rotates (unless you're at the pole, in which case this method is useless). Measuring the "error" gives you the distance to the moon in multiples of earth's radius. You need to do several nights because the moon moves around 13° a day against the background stars. If you do it at a latitude of 48° where I live and with an eight hours delay between the measurements, you should get an "error" of around 1.15° - hard to confirm by measuring its altitude, but very easy if you can match the moon's position against the background stars on a good celestial map.
That's the theory, but the practical problem is that the full (and you have to do it with a full moon) outshines basically all background stars, so it's hard to get them into the same shot. How would you go about it? Use a physical filter to dim the moon precisely cut to only cover the moon as nearly as it's possible? Any better ideas?
Alright, I have this pipe dream to one day measure the moon's distance through the diurnal parallax method with my kid as soon as he's old enough to understand the math involved (basic trig, which isn't my strongest suit either so I'd rather wait till someone who does so for a living teaches him). It's probably going to be 10 years before that happens, but I'm currently in little position to make plans otherwise, why not make plans about this?
The method is fairly simple in theory: You measure the moons position against the background stars four hours before midnight in three consecutive nights, and in the second night you also measure it four hours *after* midnight. The difference from the expected position is due to your own movement as the earth rotates (unless you're at the pole, in which case this method is useless). Measuring the "error" gives you the distance to the moon in multiples of earth's radius. You need to do several nights because the moon moves around 13° a day against the background stars. If you do it at a latitude of 48° where I live and with an eight hours delay between the measurements, you should get an "error" of around 1.15° - hard to confirm by measuring its altitude, but very easy if you can match the moon's position against the background stars on a good celestial map.
That's the theory, but the practical problem is that the full (and you have to do it with a full moon) outshines basically all background stars, so it's hard to get them into the same shot. How would you go about it? Use a physical filter to dim the moon precisely cut to only cover the moon as nearly as it's possible? Any better ideas?
