The Hunt for Exomoons, Image Stacking, and Northwestern Andromeda

In the September 2020 issue of Sky & Telescope, we finish off our three-part series on volcanism with a look at the end of the life cycle of a volcanic world. We also take a look at the pros and cons of image stacking when processing your images. The Andromeda Galaxy is a popular astrophotography target, and this month, we guide readers through several of its subtle wonders. Such little marvels are nowhere near as hard to spot as the so-far elusive exomoon. Read all about the scientists who are painstakingly hunting for moons outside of our solar system. Finally, after a decade of careful observation and comparison, a team of astronomical detectives has estimated the date and time that Johannes Vermeer observed the scene he painted in View of Delft, using his carefully painted patterns of light and shadow as clues.


The Fate of Volcanic Worlds

Comparing the volcanic histories of the inner solar system worlds tells us how rocky bodies age.

By Paul Byrne

Dating Vermeer’s View of Delft

A team of astronomical detectives delves into a masterwork by a mysterious artist.

By Donald W. Olson et al.

The Pros and Cons of Image Stacking

This method is all about improving signal and reducing noise, though you need to know when to apply it.

By Sean Walker

The Hunt for the First Exomoons

A handful of scientists are attempting to discover the first moons outside our solar system.

By Shannon Hall

The Andromeda Outback

Exploring northwestern Andromeda reveals subtle but satisfying wonders.

By Ken Hewitt-White

Beyond the Printed Page:

The View of Delft

See the painting and learn more about Johannes Vermeer.

Triton Tracker

Use our tool to spot Neptune’s largest moon.

The Ring Nebula

Enjoy NASA’s 3D model of M57’s structure.

DIY Eyepieces

Read about more homemade eyepieces on Red Henry’s Facebook page.


Tour the Vega Hour

There’s something to see on September evenings no matter which direction you face.

By Fred Schaaf

Voyaging to Neptune

The most distant planet is at opposition this month.

By Bob King

The Moon’s Biggest Cold Spot

This popular lunar region hides an enduring mystery.

By Charles Wood

The Berkeley Clusters

These groupings are rarely observed but often rewarding.

By Sue French 

Table of Contents

See what else September's issue has to offer.


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