12 votes
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Usage of $\sim$, $\approx$, $\simeq$, and $\cong$ in observational astronomy?

$\simeq$ and $\approx$ both mean "approximately equal to". I don't think $\cong$ is used so often, but if I read it, I would interpret is as the same as the two others. $\sim$ in principle means "of ...
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  • 32.3k
7 votes
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Superscript-subscript uncertainty notation

When quoted like this they would usually be the most likely value (peak of the probability distribution) or the median value (where half the distribution is above or below), and then the superscripts ...
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  • 116k
4 votes
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What abbreviations, letters, or symbols do we use to denote highly degenerate stars?

Neutron stars and black holes do not have assigned spectral types since they do not have a measurable optical/IR spectrum - which is the basis for assigning a spectral type. There are many ...
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4 votes
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What does Sa and Sab mean for spiral galaxies?

Capitalization is critical here. (As is knowing which classification system is being used.) The traditional spiral stages (going back to Hubble) are Sa - Sb - Sc; this was a sequence from more ...
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  • 14.7k
3 votes

What symbol is used for the moon when doing calculations?

There is no authorative standard - you can use what you want, as long as it is clear what you mean. Besides that: yes, ☽ is reasonably standard. Often also written indices like $M_{moon}$ or $M_m$ are ...
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3 votes
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How to interpret this old degree notation?

The notation $(x;\;y:z)$ seems to be $(30\times 60)x+60y+z$ in minutes of arc. The calculation seems to take just the integer part rather than rounding. Thus, for example, step 8 is $$\begin{eqnarray}...
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  • 7,674
2 votes
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Name and language of symbol in astronomy book

This is a variant of pi, or "pomega". In LaTeX, you can get it by using \varpi $$\varpi$$ TeX has a question on ...
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2 votes

Usage of $\sim$, $\approx$, $\simeq$, and $\cong$ in observational astronomy?

Recently, some in the astronomy literature are adopting $\sim$ in the statistics sense to mean "is sampled from" or "has the distribution of" (the last definition on mathworld). For example, $$ x \...
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  • 21
1 vote

Usage of $\sim$, $\approx$, $\simeq$, and $\cong$ in observational astronomy?

As an (ex) professional astronomer, I can tell you that there are no rules that are followed. There are very very few exact measurements in Astronomy, x rarely technically equals anything. In ...
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1 vote

Usage of $\sim$, $\approx$, $\simeq$, and $\cong$ in observational astronomy?

Wikipedia (where would we be without it) has a handy list of mathematical symbols which is pretty useful in this context. Note that in particular : $\sim$ will crop up often as meaning ...
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1 vote
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From Mean Moon to True Moon in an old procedural calendar

How would you interpret this? "(1780 + 80) * 3 on base 808, and add 2" As before, there is a confusing avoidance of specifying the unit under consideration, but the pattern is still that the last ...
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  • 7,674

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