Define parallex angle,and parallatic angle.how can we find the distance of moon by parallax method?
Answers
Answer:
parallax is the name given to change in position of an objext with respect to the background,when the objext is seen feom different position. parallactic angle is the angle made by the arc of length of 1 AU. You can find the distance by the formula distance = angle/Radius of moon.
ANSWER
PARALLAX ANGLE :
The parallax angle is the angle between the Earth at one time of year, and the Earth six months later, as measured from a nearby star. Astronomers use this angle to find the distance from the Earth to that star. ... Because of this, nearby stars will seem to move relative to distant, "background" stars.
PARALLATIC ANGLE:
In spherical astronomy, the parallactic angle is the angle between the great circle through a celestial object and the zenith, and the hour circle of the object. It is usually denoted q. In the triangle zenith—object—celestial pole, the parallactic angle will be the angle at the celestial object. Despite its name, this angle is unrelated with parallax. The parallactic angle is zero when the object crosses the meridian.
The Experiment
Materials Required:
* An inclinometer or similar angle measuring device
* A DSLR Camera or any camera that allows for long exposures
* A lens that can show the Moon with modest detail while also showing the surrounding star-field. A 75–300mm zoom lens is perfect for this
* A tripod to mount the camera on
* A shutter release cable to take long exposures without disturbing the camera
* A friend with a similar or identical setup
* Several hundred miles between you and said friend.
* Astronomy software such as the free program Stellarium
* Image processing software such as Photoshop or GIMP
Introduction to Parallax
Stick out your finger, now close one eye, and then the other. Notice how your finger appears to move between the two viewpoints? This is parallax. Parallax is the apparent displacement of an object when viewed along two different lines of sight. It’s important to our experiment because by measuring the amount of parallax an object displays, one can find its distance via trigonometry. Parallax is often used by astronomers to measure the distance to nearby stars, and was used by early astronomers to determine the distance to the planets and the Sun. In this experiment we’ll be measuring the Moon’s parallax in order to determine its distance.
Image for post
An example of Lunar parallax. (Not to scale)
The Observation
Pick a night when the moon is visible to both you and your friend, preferably one where the moon is near a bright star. This can be planned in advance using astronomy programs like Stellarium and websites like CalSky.
Ensure you have everything set up and focused at least fifteen minutes before the the observation. Punctuality isn’t crucial to this experiment but it is worth practicing.
Ensure you have reliable communication with your partner in the experiment. The synchronization of the photos you will be taking is crucial as the Moon is not a static object and has its own motion besides its apparent motion caused by Earth’s rotation.
Have the camera set on a remote shutter so you don’t bump the camera while it is shooting.
Each synchronized shot should be long enough in exposure to show your target star, but short enough to show a sharply defined terminator on the Moon. This will be important for image alignment later.
Make sure to also measure the elevation angle of the Moon from both locations using your inclinometer. This will be important later. You can find a guide to making a basic inclinometer here. Or you can use a smartphone app such as Theodolite (iOS) or Dioptra (Android).
This essentially ends the main bulk of observing, though it is wise to take multiple shots and then discard the bad ones (i.e an airplane passes through the frame or wind shakes the camera), that way only the best data is selected.
As a final part to your observing session take a long exposure photo of the night sky after the Moon has drifted out of frame. Make sure to not change the focus or the zoom of your lens. This star field image will be useful in calculating the scale of your image, which will be important for measuring angles later.
