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Distractions and amusements, with a sandwich and coffee.

I'm not real and I deny I won't heal unless I cry.
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If you like space, you'll love my the 12,000 billion light-year map of clusters, superclusters and voids. Find the biggest nothings in Boötes and Eridanus.

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— Viorica Hrincu

Having recently drawn a few skycharts (Superclusters & Voids, Sanctuary Project), I was frustrated by the lack of parsable resources for the IAU Constellations.

Finding a plain-text parsable definition of the asterisms proved impossible. So I created my own.

DOWNLOAD CONSTELLATION SHAPE FILE

DOWNLOAD YALE CATALOGUE OF BRIGHT STARS POSITION FILE

# CHANGE LOG # # 29 Nov 2018 # + line between Betelgeuse (HR 2061) and Bellatrix (HR 1790) in Orion added # # 27 June 2018 # + Greek designations now a separate field # + fixed Proxima Centauri and Barnard's Star, neither of which # are in BSC

All the constellation shapes were derived by manually examining the IAU map and cross-referencing the stars to the Yale Catalogue of Bright Stars.

The list of IAU constellation shapes in the file linked to above conveniently includes the J2000 right ascention and declination for each stars in the pair, along with their HR index, magnitude, Greek letter designation and name. See the file header for all the details.

For example, Cassiopeia's familiar "W" appears as 4 lines that indicate the connections between HR stars 21-168-264-403-542.

Cas 21 2.294583 59.149722 2.27 bet Caph|bet Cas|11 Cas 168 10.127083 56.537222 2.23 alf Schedar|alf Cas|18 Cas Cas 168 10.127083 56.537222 2.23 alf Schedar|alf Cas|18 Cas 264 14.177083 60.716667 2.47 gam BU 499A|BU 1028|gam Cas|27 Cas Cas 264 14.177083 60.716667 2.47 gam BU 499A|BU 1028|gam Cas|27 Cas 403 21.454167 60.235278 2.68 del Ruchbah|BUP 19A|del Cas|37 Cas Cas 403 21.454167 60.235278 2.68 del Ruchbah|BUP 19A|del Cas|37 Cas 542 28.598750 63.670000 3.38 eps Segin|eps Cas|45 Cas

The names are obtained from IAU Catalog of Star Names (IAU-CSN) and Simbad's name fields "NAME", "*" and "**", in that order. You can conveniently browse the Simbad database by any star identifier. For example, for Sirius the URL is http://simbad.u-strasbg.fr/simbad/sim-id?Ident=sirius.

Please report any errors to me.

The shapes of all the constellations and the stars that define the asterisms shown in the image below. I also include all the 110 Messier objects with common names in this map (hollow circles).

The map also shows the galactic equator and the ecliptic. The vernal equinox, summer solstice, autumn equinox and winter solstice occur along the ecliptic at right ascension 0/360 (Pices), 270 (Sagittarius), 180 (Vigo) and 90 (Gemini/Taurus).

Whole-sky star charts are traditionally drawn with 360 right ascention on the left in decreasing order towards 0 on the right.

You can download this file as PNG, SVG or PDF.

If you're interested in more astronomical resources, check out my Universe Superclusters and Voids resource page.

I've also created detailed charts that include all the 9,110 stars in the Yale Catalogue of Bright Stars. These are labeled by their Greek designation with the constellation as well as with their IAU name.

The maps also show all 110 Messier objects, labeled by their index and, where available, a common name. All the labels in these maps have been lovingly adjusted manually to avoid ambiguity and overlap. Available are blue, black and white background versions.

My cover design for Hola Mundo by Hannah Fry. Published by Blackie Books.

Curious how the design was created? Read the full details.

*You can look back there to explain things,
but the explanation disappears.
You'll never find it there.
Things are not explained by the past.
They're explained by what happens now.
—Alan Watts*

A Markov chain is a probabilistic model that is used to model how a system changes over time as a series of transitions between states. Each transition is assigned a probability that defines the chance of the system changing from one state to another.

Together with the states, these transitions probabilities define a stochastic model with the Markov property: transition probabilities only depend on the current state—the future is independent of the past if the present is known.

Once the transition probabilities are defined in matrix form, it is easy to predict the distribution of future states of the system. We cover concepts of aperiodicity, irreducibility, limiting and stationary distributions and absorption.

This column is the first part of a series and pairs particularly well with Alan Watts and Blond:ish.

Grewal, J., Krzywinski, M. & Altman, N. (2019) Points of significance: Markov Chains. *Nature Methods* **16**:663–664.

*Places to go and nobody to see.*

Exquisitely detailed maps of places on the Moon, comets and asteroids in the Solar System and stars, deep-sky objects and exoplanets in the northern and southern sky. All maps are zoomable.

Quantile regression explores the effect of one or more predictors on quantiles of the response. It can answer questions such as "What is the weight of 90% of individuals of a given height?"

Unlike in traditional mean regression methods, no assumptions about the distribution of the response are required, which makes it practical, robust and amenable to skewed distributions.

Quantile regression is also very useful when extremes are interesting or when the response variance varies with the predictors.

Das, K., Krzywinski, M. & Altman, N. (2019) Points of significance: Quantile regression. *Nature Methods* **16**:451–452.

Altman, N. & Krzywinski, M. (2015) Points of significance: Simple linear regression. *Nature Methods* **12**:999–1000.

Outliers can degrade the fit of linear regression models when the estimation is performed using the ordinary least squares. The impact of outliers can be mitigated with methods that provide robust inference and greater reliability in the presence of anomalous values.

We discuss MM-estimation and show how it can be used to keep your fitting sane and reliable.

Greco, L., Luta, G., Krzywinski, M. & Altman, N. (2019) Points of significance: Analyzing outliers: Robust methods to the rescue. *Nature Methods* **16**:275–276.

Altman, N. & Krzywinski, M. (2016) Points of significance: Analyzing outliers: Influential or nuisance. Nature Methods 13:281–282.

Two-level factorial experiments, in which all combinations of multiple factor levels are used, efficiently estimate factor effects and detect interactions—desirable statistical qualities that can provide deep insight into a system.

They offer two benefits over the widely used one-factor-at-a-time (OFAT) experiments: efficiency and ability to detect interactions.

Since the number of factor combinations can quickly increase, one approach is to model only some of the factorial effects using empirically-validated assumptions of effect sparsity and effect hierarchy. Effect sparsity tells us that in factorial experiments most of the factorial terms are likely to be unimportant. Effect hierarchy tells us that low-order terms (e.g. main effects) tend to be larger than higher-order terms (e.g. two-factor or three-factor interactions).

Smucker, B., Krzywinski, M. & Altman, N. (2019) Points of significance: Two-level factorial experiments *Nature Methods* **16**:211–212.

Krzywinski, M. & Altman, N. (2014) Points of significance: Designing comparative experiments.. Nature Methods 11:597–598.