Astronomy Stack Exchange
Astronomy Stack Exchange

Questions tagged [positional-astronomy]

Questions about positions of objects in the sky, either relative to a fixed coordinate system like the equatorial and ecliptic coordinate systems, or relative to an observer's point of view.

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What positional accuracy (ie, arc seconds) is necessary to view Saturn, Uranus, beyond?

My son and I are building an azimuth/elevation controller to point the telescope at planets using servos and a microcontroller. Assuming that our device is calibrated (that is, we tell our device to point at a specific RA/Dec and points in the right…
KJ7LNW
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How/where to check where the Sun is (constellation)?

I would like to check in which constellation the Sun was in at some time in the past, any recommendations how to do that?
user7549
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VSOP for exosatellites? (Io, Titan, Ariel, etc)

VSOP87 (and the subsequent VSOP2000 and VSOP2013) provide reasonably accurate planetary positions while still maintaining a small file size compared to the Chebyshev polynomial files. VSOP includes our moon, but has anyone created something…
user21
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Galactic Coordinate System and distance

If the Galactic Coordinate System is made up of two values, angles of longitude and latitude, how is distance measured? If you have those two values, you get a line from the sun in a certain direction. There might be multiple objects on that line,…
The Gaming Scientist
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Calculating Angular Distance

Given the horizontal coordinates of two objects in the sky, how does one go about calculating the angular separation between them?
ruadath
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What is the difference between ICRS and ICRS2?

When I first learned about Positional Astronomy (50 years ago), everything was described with respect to the Equator and Ecliptic (true or mean, of date or of a specific epoch). Then 'they' invented the International Celestial Reference System…
Ken Duffill
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Why is Eris not a part of the orbital plane like other planets?

I realise that the planets are more or less part of the same orbital plane. But why is the orbit of Eris, or even Pluto, at such significant tilts of orbit (44 degrees and 17 degrees respectively)? I tried to find an answer but couldn't. What is the…
AstroByte
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Synodic period of planets

Many books explain the difference between synodic and sideral periods. The synodic period of planets are tabulated for centuries and it is defined as the time interval between two consecutive repetition of phase, phase in this case meaning the…
Brasil
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Get date and time by position of the sun and the observer position

I am working on an astrology project (don't panic, my question is about astronomy or math), where I need to figure out some values by the longnitude of the planets. I have a program for this, the Swiss ephemeris. With this, I can get the position of…
vaso123
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How do I get from Star Atlas to real life?

This question is about finding the elevation and bearing of a given star at a particular time at Latitude 52N. I look up the RA and Declination of my star. How do I calculate its bearing and elevation at hourly intervals?
user2256790
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How to calculate Local siderial time that is consistent with Stellarium

I have a number of date and times when I am interested in the location of my zenith and what objects might co-locate with these positions. The easiest way to do this was to put my latitude and longitude into Stellarium and create a bookmark at the…
user36093
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Does Earth's movement around the sun contribute to the angular distance between the moon and planets?

This merged image shows the angular distance between the moon and Mars at 10 PM (upper part) and the change in the angular distance at 10 PM the following day (lower part). My understanding is that the moon changes position in the sky by an…
William
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Best Books on Spherical Astronomy

I am preparing for an astronomy olympiad and a good amount of questions in the olympiad come from Spherical astronomy, some of the books ive tried reading were too hard to understand as this topic requires a good amount of visual representation.…
L lawliet
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The Jupiter Effect Book

This evening I have been thinking about the anxiety caused in 1982 by predictions in John Gribbin and Stephen Plagemann 1974 book The Jupiter Effect. I was a teenager in 1982. The planets aligning somewhat together on one side of the Sun did not…
doctorsundar
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Can I derive the position of my house's shadow from sun altitude?

I'd like to pull in my awning if my house's shadow has reached a point where the awning has no use any more. The house is almost perfectly aligned in a North-South direction, the garden with the awning is in the east. My home automation (fhem)…
Markus Grunwald
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