{"id":29601,"date":"2022-02-11T09:16:34","date_gmt":"2022-02-11T09:16:34","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=104504"},"modified":"2022-02-11T09:31:09","modified_gmt":"2022-02-11T09:31:09","slug":"how-to-observe-and-photograph-the-moons-terminator","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/how-to-observe-and-photograph-the-moons-terminator\/","title":{"rendered":"How to observe and photograph the Moon\u2019s terminator"},"content":{"rendered":"

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By Patrick Moore\n \t\t<\/p>

Published: Friday, 11 February 2022 at 12:00 am<\/p>

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In general, the best time to view a given feature on the Moon is when the terminator line is nearby.<\/p>\n

The terminator on the Moon is the line that separates lunar day and night; the illuminated and the shaded sections of the Moon from Earth\u2019s perspective.<\/p>\n

The lunar terminator is the region where the Sun is either rising or setting, where crater rims\u00a0and mountain peaks stand out in stark relief, casting inky black shadows across the lunar surface that exaggerate their presence.<\/p>\n

Get weekly lunar times and phases sent directly to your email inbox by signing up to the <\/strong><\/em>BBC Sky at Night Magazine<\/strong><\/a> e-newsletter<\/a>.<\/strong><\/em><\/p>\n

\""The\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
The terminator highlights features like mountains and craters on the lunar surface. Credit: William Ian Hamilton, Gloucestershire, UK. Equipment: Canon EOS100D, Mead LX90.<\/span><\/figcaption><\/div>\n

Lunar features further from the terminator show hardly any shadows and are harder to make out.<\/p>\n

At day zero of the phases of the Moon<\/a> \u2013 new Moon \u2013 the whole of the dark lunar hemisphere points towards Earth.<\/p>\n

Over the next 15 days the terminator slowly creeps across the surface of the Moon from east to west until the disc is fully illuminated at full Moon<\/a>.<\/p>\n

Then the tables are reversed as the encroaching darkened hemisphere heads west with each passing day, until the diminishing crescent becomes lost in the pre-dawn twilight.<\/p>\n

Here we\u2019ll discuss how to make the most of the terminator; how to observe and photograph the play of light and shadow on the surface of the Moon as it changes for a particular lunar feature.<\/p>\n

Observing the Moon\u2019s terminator<\/strong><\/h2>\n
\""Clair\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Clair obscur effects on the Moon. Upper row, left to right: Lunar X, Lunar\u00a0V, Plato\u2019s Hook. Lower row, left to right: Face in Albategnius, the Jewelled Handle, Cassini\u2019s Moon Maiden (south-up view). Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

W<\/span>hether you\u2019re observing the Moon through <\/span>an eyepiece or via a camera sensor, the features you see will initially appear fairly static.<\/p>\n

But\u00a0if you pick a feature close to the <\/span>terminator and monitor its appearance over 30-minute intervals, you will see changes.<\/p>\n

For help picking a feature, read our guides on the Moon\u2019s best features<\/a> or interesting clair-obscur effects<\/a>.<\/p>\n

The view you get from one night <\/span>to the next is different and changes must have occurred over the hours between views.<\/p>\n

\""Down\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
The terminator of the first quarter Moon by Julie Straayer, Albany Creek, Queensland, Australia.<\/span><\/figcaption><\/div>\n

Each night the lunar terminator moves about 12\u02da in longitude around the Moon\u2019s globe.<\/p>\n

For the best results you\u2019ll need to start observing a lunar feature when the Moon is visible for (at least) a few hours above the horizon.<\/p>\n

The Moon\u2019s altitude needs to be 30\u02da or higher for the most stable results.<\/p>\n

Try and pick surface subjects that have a good relief height as these will generate the most dramatic and fast-moving shadows.<\/p>\n

\""Mare\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Mare Crisium on the Terminator by Ian Peck, Londonderry, N. Ireland. Equipment: SkyWatcher 200p, Logitech c270hd webcam.<\/span><\/figcaption><\/div>\n

Look for flatter surrounding areas as these are better than complex, contoured ones for showing faster moving shadows.<\/p>\n

Mountain ranges make excellent subjects for this as many border the relatively flat lava surfaces of adjacent lunar mares<\/a>.<\/p>\n

High peaks will cast dramatic pointed shadows across a mare\u2019s surface and these appear to move surprisingly fast, certainly quickly enough to show the sort of motion we are after here.<\/p>\n

For more advice, read our guide on how to observe the Moon<\/a>.<\/strong><\/em><\/p>\n

Photographing the Moon\u2019s terminator<\/strong><\/h2>\n
\""A\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
A sequence of shadow shots can show how the terminator moves across a lunar feature such as the Lunar X. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

One way of really capturing the changes in light and shadow across a specific lunar feature is to photograph it.<\/p>\n

Choose a night that looks as if it will give you a few hours of clear sky.<\/p>\n

There\u2019s nothing more annoying than having to terminate an astophotography sequence due to cloud or high haze.<\/p>\n

The latter will also affect the appearance of your results and, if creating an animation, will cause unwanted frame flickering which will detract from the overall effect.<\/p>\n

Shadow movement animations need magnification <\/span>for the best results.<\/p>\n

\""Clair\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
The Lunar X. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

Low image scale shots can show shadows change over time, but it takes longer for the movement to be revealed.<\/p>\n

But a high-resolution, highly magnified image can show impressive shadow movement <\/span>over a short time.<\/p>\n

High frame rate captures work best for this, as they give the sharpest results.<\/span><\/p>\n

Use a high frame rate camera and capture around <\/span>1,000 frames for each shot.<\/p>\n

Carry out image processing<\/a> on the results with your preferred registration-stacking<\/a> software (eg AutoStakkert!) combining the final results into your animation.<\/p>\n

Be sure to maintain a constant interval between <\/span>sequences, or the shadow movement will appear to judder.<\/p>\n

Start with 30-minute intervals to give a decent number of frames to animate.<\/p>\n

If you like the end result, consider doing animations using shorter time intervals to give more frames.<\/p>\n

Below we\u2019ll show you how to image a feature like the Lunar X<\/a> as it changes over time.<\/p>\n

For more advice, read our guide on how to photograph the Moon<\/a>.<\/strong><\/em><\/p>\n

Equipment you will need<\/span><\/strong><\/h2>\n