Questions tagged [frame-of-reference]
For questions regarding the frame of reference of an observer in an astronomical situation.
34 questions
0 votes
0 answers
74 views
convert velocity from barycentric to LSRK
I am a student studying HI HVC clouds, and I need to compare results from several HI surveys. I ran into a problem of "How to convert HIPASS barycentric velocities to LSRK velocities". ...
- 311
0 votes
1 answer
97 views
Astropy - radial velocities relative to the Local Standard of Rest
Why does this code, using astropy LSR, give the same result in RV despite differing proper motions, i.e. 8.2802 km/s? I would expect that a change in proper motion should have an influence in the ...
- 559
1 vote
0 answers
55 views
Does WGS 84 use a flat metric?
The Geocentric Celestial Reference System (GCRS) and the International Terrestrial Reference System (ITRS) are based on an approximate Schwarzschild metric, as discussed for instance in Soffel & ...
- 203
0 votes
0 answers
299 views
Tool to convert between GCRF and (Earth-centered) J2000 reference frames
I want to convert some Cartesian vectors between the Geocentric Celestial Reference Frame (GCRF) and Earth-centered J2000 frame. I know that these two frames are nearly identical and, for most ...
- 2,761
-1 votes
1 answer
231 views
CMB redshift used to determine the difference in aging between the two inertial observers
If CMB redshift tells us our cosmological time dilation and we have two inertial observers in relative motion, who measure slightly different CMB redshift at the direction of their motion relative to ...
user57748
7 votes
1 answer
276 views
Finding stars that would be visible from satellite
I'm working on a mock image of a picture taken from a satellite (like ISS). Lets say I have a camera on ISS pointing in the direction of velocity (I have this velocity vector defined in ITRF and ...
- 329
7 votes
2 answers
1k views
Why is there a difference between the ICRS and EME2000
The International Celestial Reference System (ICRS) defines coordinate axes that are closely aligned with those of the J2000 (aka EME2000) reference frame. The International Celestial Reference Frame (...
- 625
1 vote
0 answers
39 views
What would be the new Equation of motion if the magnetic field's origin is shifted from the origin of a co-rotating spherical polar coordinates?
The equation of motions due to the dipole magnetic force of a planet in a frame corotating with the planet and origin at the centre of planet assumed to be sphere components wise are given as below: \...
- 145
2 votes
1 answer
611 views
How to convert TEME (or ITRF) to horizontal
I have TEME coordinates from sgp4 propagation. I can convert those (in python) to ITRF given date and time of observation. How to convert coordinates from one of those two frames to horizontal azimuth ...
- 329
3 votes
3 answers
243 views
Reverse polynomial model for reverse astrometry
I have a polynomial model that can transform pixel X,Y coordinates to standard $\xi, \eta$. This model looks like this: $\xi/\eta = a_1 + a_2x + a_3y + a_4x^2 + a_5xy + a_6y^2 + a_7x^3 + a_8x^2y+a_9xy^...
- 329
4 votes
2 answers
2k views
How is Earth's Rotation Angle (ERA) defined and measured
UTC typically ticks with TAI. But to keep UTC from drifting far from the rotation angle of the Earth we occasionally add leap seconds to ensure that UTC does not drift too far from the UT1 timescale. ...
- 405
0 votes
0 answers
93 views
What is the galactocentric aberration?
At the Wikipedia about an aberration, there is the phrase: a recommended galactocentric aberration constant of 5.8 µas/yr What is the galactocentric aberration? How is it calculated correctly? An ...
- 339
8 votes
2 answers
995 views
Does the barycenter of an n-body system remain constant during collisions?
I am developing an n-body simulation software which simulates collisions. Most of these have a stationary frame of reference, meaning that orbiting objects may eventually move off the screen. To ...
- 6,892
2 votes
0 answers
80 views
Satellites or UFOs? [closed]
Last night in Greenville MI at around 9:15pm-9:25pm (I don't know the exact time) I saw what appeared to be a satellite appear and disappear and then a few seconds later another possible satellite ...
- 31
2 votes
2 answers
583 views
Measurement of Planetary Aberration (similar to stellar aberration)
It is often stated that, "Planetary aberration is a combined result of the observer's motion and the time taken for light to travel from a body in the Solar System to the observer". I am not ...
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