Sky & Telescope - USA (2020-06)

MARS SIZE COMPARISON: GARY SERONIK /

S&T

,

SOURCE: COELIX AND USGS

JUNE 2020 OBSERVING
Celestial Calendar by Bob King

A Martian

Sneak Peek

One of the best showings of

the Red Planet in decades

starts now.

UK imager Damian Peach created this sequence of Mars images during the planet’s close 2018 apparition. North

is presented up, and the sequence progresses from left to right with the earliest images on the left, the latest on

the right. Notice that the disks photographed just prior to the July 31st closest approach have muted features, the

result of a planetwide dust storm raging at the time.

G

rab all the Mars you can this appa-

rition. The Red Planet won’t be this

close to Earth again until 2035. Closest

approach during the current appari-

tion occurs on October 6th, when the

tiny orb will swell to 22.6′′. That’s only

1.7′′ less than at its perihelic opposition

in 2018, which was less favorable for

Northern Hemisphere observers due to

the planet’s southerly declination. This

time Mars stands 31 ° farther north,

where atmospheric turbulence and poor

seeing typical of lower altitudes should

have much less affect on the view.

Longtime Mars observers know that

every arcsecond counts, which is why

48 JUNE 2020 • SKY & TELESCOPE

I encourage you to rise at dawn this

month and catch the planet when it’s

at its highest before sunrise. On June

12th, Mars grows to 10′′ in diameter —

the generally accepted minimum size at

which useful observations can be made.

While only half as large as it will be at

opposition, now is the time to start get-

ting acquainted with the planet’s most

prominent surface markings, called

albedo features. Finding your way around

Mars early will prepare you to make the

most of the upcoming close approach.

The Martian South Polar Cap (SPC)

should be prominent throughout June

and appears glaringly white, like snow

on a sunny day. Watch for the SPC to

gradually shrink during the month as

spring deepens in the planet’s southern

hemisphere. A 6-inch telescope used

at 150× or greater should reveal the

thumb-shaped Syrtis Major, the “wand”

of Sinus Sabaeus, Mare Cimmerium’s

dark band, and the mottled blotch of

Mare Erythraeum. Use higher magnifi -

cation if seeing conditions allow it, and

boost the contrast of these often-tenu-

ous features with the help of an orange

Wratten 21 or red Wratten 23a fi lter.

Patience is key. Eyeball the planet

for at least 15 minutes (a half hour is

better), and you’ll often catch enough

South is up in this pair of illustrations showing the changing phase and diameter

of the Martian disk as the planet grows to its maximum size when it’s closest to

Earth on October 6th.

June 12

10.0′′

October 6

22.6′′

March
2018

April

2018

May

2018

June

2018

July

2018