Graph Right Ascension & Declination on Globe Graph

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Discussion Overview

The discussion revolves around the process of graphing Right Ascension (RA) and Declination (Dec) on a globe graph, particularly in the context of locating celestial objects on a blank map of the night sky. Participants explore the similarities between RA/Dec and longitude/latitude, and the challenges of using a blank celestial map.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that Right Ascension is analogous to longitude and Declination to latitude.
  • One participant questions how to begin locating objects on a blank map of the night sky, asking whether to start with RA or Dec and if the starting point matters.
  • A participant provides a link to resources on polar aligning telescopes and includes a diagram that illustrates how RA and Dec work.
  • Another participant expresses confusion about the utility of a blank map, suggesting that it is challenging to plot coordinates without additional grid lines or measurement tools.
  • It is noted that the zero-point on the RA and Dec grid is the first point of Aries, with RA following the celestial equator and Dec being perpendicular to it.
  • One participant mentions that while estimation is possible, it may lead to inaccuracies.

Areas of Agreement / Disagreement

Participants generally agree on the conceptual relationship between RA/Dec and longitude/latitude, but there is disagreement regarding the effectiveness of using a blank map for plotting coordinates, with some expressing confusion and others providing guidance.

Contextual Notes

Participants mention limitations in the provided materials, such as the absence of grid lines or measurement tools on the blank map, which may affect the ability to accurately plot RA and Dec.

Commodore
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Can anyone explain how to graph Right Ascension and Declination on a globe graph?
 
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Do you know how longitude and latitude are plotted on a globe? Right Ascension is like longitude and Declination is like latitude.
 
I understand that it is like longitude and latitude, but if I am presented with a blank map of the night sky and am asked to find what is at some number RA and Dec, how do I start, RA or Dec? And, does it matter where I am starting from?
 
Commodore said:
I understand that it is like longitude and latitude, but if I am presented with a blank map of the night sky and am asked to find what is at some number RA and Dec, how do I start, RA or Dec? And, does it matter where I am starting from?

What do you mean, a "blank map?" How is a blank map useful?

If you're given a map with coordinates on it, all you need to do is... find the spot with the given coordinates. You can start with either coordinate first. When you find the right RA, you've found a specific line of "longitude." You can then follow that line until you find the given declination.

- Warren
 
The zero-point on the RA and Dec grid is the first point of Aries (the location of the sun in the sky on the Vernal equinox). RA follows the direction of the celestial equator (the projection of Earth's equator in the sky) and Dec goes perpendicular to that.
 
chroot said:
What do you mean, a "blank map?" How is a blank map useful?

If you're given a map with coordinates on it, all you need to do is... find the spot with the given coordinates. You can start with either coordinate first. When you find the right RA, you've found a specific line of "longitude." You can then follow that line until you find the given declination.

- Warren

The teacher gave us a blank circle with the Vernal Equinox line and the Celestial Equator listed, no other grid lines or way to measure degrees and said put a dot at the such and such RA and Dec points. Is it just me or was this kind of crazy?
 
You could always estimate, but you might not be very accurate.

- Warren
 

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