... system. (An epoch is a precise moment when given
celestial coordinates or orbital elements are strictly
correct. That is, an epoch is a time arbitrarily selected
Corresponding Angles and Distances forvJarded expressly for
... orbit; but the stars, which have latterly been gradually approaching, have within the last two years closed up so rapidly as to be in
the early part of the current year quite beyond the power of my
instrument, the distance being estimated as not exceeding o"· 4,
while only a rough guess could be mad ...
Right Ascension / Declination
... one hour at the point where Sirius was, the star you are now looking at is located 1 R.A. hour away from
Sirius. (We do not recommend trying this. There are much better things to be doing with your time.)
There is only one slight hitch with all of this. Due to precession, the earth wobbles and in th ...
Numbers to Keep in Mind
... (as well as positions the Sun, Moon,
and planets) can be found in the
Numbers to Keep in Mind
... § Heliocentric Correction: because the Earth orbits the Sun,
the light-travel time from an astronomical object may vary by up
to ± 8.3 min. This is the heliocentric time correction (sometimes
called the Rømer delay). (Note: there is also a heliocentric
velocity correction, due to the Earth’s motion ...
Coordinate System Notes 3 - School District of La Crosse
... A. year- the time necessary for one complete revolution about the sun 365.25 mean
B.Types of years
1. sidereal year- The time necessary for the sun to return to the same position
with repect to the stars.
2. solar year( tropical) is the intreval between the passage of the sun through the ...
1 The Celestial Equator and the Ecliptic 2 Seasonal Changes in the
... The Greek philosopher Hipparchus first noted that the right ascension and declination of stars were different in his time than they had been recorded by earlier
We now know that this is due to the precession of the equinoxes. This is fundamentally due to the precession of the Earth’s ro ...
Sample pages 2 PDF
... during some part of the year or could be not observable at all, at the position of the
observer. Only circumpolar objects can be observed over the whole year.
The most intuitive coordinate system is the alt-azimuth system, based on the
location of the observer. The reference plane is the local horiz ...
... The Changing Sky
North Pole of the Earth is pointed at
Polaris (the North or Pole star), which
stays stationary as the other stars move
Homework Assignment 1 — Solutions
... (a). The first day of summer is the summer solstice, when the Sun is at a declination +23◦ 300 above
the celestial equator (see Fig. 1.12). For an observer at 42◦ N latitude, the Sun will appear
42◦ − 23◦ 300 = 18◦ 300 from the zenith, corresponding to an altitude of 71◦ 300 above the horizon.
29 Jan: Maps of the Sky
... for 2010: 221,600 miles or 356,600 km, 7 %
less than its average distance. This will make
the full Moon appear slightly larger than usual. “
... Standard error: 0.004
Mean Vt magnitude: 4.159
Standard error: 0.003
Source of photometric data: The Bt,Vt data are median values, rather than de-censored mean
values (mainly relevant for bright stars with Bt<=8.5 mag and Vt<=8.0 mag).
Johnson B-V colour index: 0.541
Standard error: 0.004
Number of ...
... along the horizon is fastest around the
equinoxes, and slowest around the
Around the equinoxes, the declination
(distance from the celestial equator) will
change by 0.5° per day
Near the solstices, it will stay fixed for
almost a week
Notes and Equations
... The planets are moving, approximately in the plane of the ecliptic, with different
orbital periods. We therefore see them approximately in the direction of the ecliptic.
The motion of the planets can be somewhat complicated. On the average, all
the major planets move from west to east as part of the ...
29:52 Characteristics and Origins of the Solar System January 25
... The second of these lines is the ecliptic. The ecliptic is the projection of the
Earth’s orbital plane on the celestial sphere. If we plotted up all the positions of
the Sun against the background stars, it would trace out the ecliptic.
Because of the 23.5 degree tilt of the Earth’s axis, the celest ...
... Example: In Winter sun in Sagittarius, Gemini at night sky;
in summer sun in Gemini, Sagittarius at night sky
... objects, which are defined by reference to the celestial equator and
celestial poles, must also be constantly changing.
• Because of this change in the direction of the Earth's pole with time,
the coordinate systems of RA and DEC that we adopt for one epoch
are actually different for other epochs.
(Lecture 3). The Solar System in the Night Sky (cont)
... The Solar System in the Night Sky (Part 2)
→ Initial pleasantries…watch the position and appearance of the moon over the
next few days.
Let’s think about the significance of the fact mentioned in the previous lecture. 1
tropical year is 365.2422 mean solar days. To simplify things a bit, let’s ass ...
... Can measure distance on the sky in
degrees (360 degrees = complete circle)
Horizon -Zenith -Meridian -- line running from north to
south through zenith
Astronomy 360 - Indiana State University
... This is the preferred coordinate system (Equatorial Coordinates) to pinpoint objects on the
celestial sphere. Unlike the horizontal coordinate system, equatorial coordinates are
independent of the observer's location and the time of the observation. This means that only
one set of coordinates is req ...
Mercury venus and jupiter in March 2014
... Planet easily seen by every one about 30 degree above eastern Horizon. But in the 27th Moon is Close by, so you can keep tract to
observe Venus even after the sun rises and in the day light as well.
3) Mercury Moon 29 March. JPG – Declination: -8° 8' 55.7", Altitude: 8° 23' 16" and Magnitude: -0.1 O ...
Unit 1 Test Review Answers - School District of La Crosse
... 18. The .25 day of the 365.25 days of the year represents: LEAP YEAR
19. Time is based on earth upon: ALL CAN BE USED
20. A star rises at 7:00PM on October 22. At what time would it rise on Halloween?
31-22=9 DAYSX 4MIN/DAY= 36 MIN...7:00-36 MIN=6:24PM
Right ascension =
hours (or degrees) East
of the “Vernal equinox”.
Vernal equinox is
defined as the position
of the Sun on the first
day of spring. Note it is
a point on the sky, not
Astronomy 360 - indstate.edu
... latitude become lines of declination (Dec; measured in degrees, arcminutes and
arcseconds) and indicate how far north or south of the celestial equator (defined by
projecting the Earth's equator onto the celestial sphere) the object lies. Lines of longitude
have their equivalent in lines of right as ...
In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as the celestial coordinates or elliptical orbital elements of a celestial body, because these are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit.The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodies) can be used to generate an ephemeris, a table of values giving the positions and velocities of astronomical objects in the sky at a given time or times.Astronomical quantities can be specified in any of several ways, for example, as a polynomial function of the time-interval, with an epoch as a temporal point of origin (this is a common current way of using an epoch). Alternatively, the time-varying astronomical quantity can be expressed as a constant, equal to the measure that it had at the epoch, leaving its variation over time to be specified in some other way—for example, by a table, as was common during the 17th and 18th centuries.The word epoch was often used in a different way in older astronomical literature, e.g. during the 18th century, in connection with astronomical tables. At that time, it was customary to denote as ""epochs"", not the standard date and time of origin for time-varying astronomical quantities, but rather the values at that date and time of those time-varying quantities themselves. In accordance with that alternative historical usage, an expression such as 'correcting the epochs' would refer to the adjustment, usually by a small amount, of the values of the tabulated astronomical quantities applicable to a fixed standard date and time of reference (and not, as might be expected from current usage, to a change from one date and time of reference to a different date and time).