Category Archives: Astronomy

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Vega and the Constellation Lyra – 2015-10-30

The bright star Vega at magnitude 0.03 is the 5th brightest star in the sky and the third brightest star visible from the 45th parallel (Ottawa). Sirius at magnitude -1.46 is the brightest star in the sky and Arcturus magnitude -0.05 is the second brightest in the north. Although the yellow-orange star Arcturus is only marginally brighter than Vega, Vega has the advantage of being near the zenith on summer nights and the slight blue tint makes it seem even brighter.

Vega Closeup - 2015-10-30

Vega Closeup – 2015-10-30

Vega is in the constellation Lyra – the lyre or harp. Lyra is one of 48 constellations listed by Ptolemy in the second century and is on the International Astronomical Union’s (IAU) official list of 88 constellations. The long exposure image below shows the 4 bright stars of the harp as well as Epsilon Lyra (ε1, ε2 – the Double Double) left of Vega and Kappa Lyra (κ) to the right.

Vega in the Constellation Lyra - 2015-10-30

Vega in the Constellation Lyra – 2015-10-30

The chart overlay below  shows the location of the bright stars as well as the location of the M57 Ring Nebula. Vega is 25ly from earth while the other stars are at various distances. So the lyre shape is just a chance alignment when viewed from earth.

  • Vega: mag 0.03, dist 25ly
  • Epsilon 1: mag 4.65, dist 162 ly
  • Epsilon 2: mag 4.56, dist 161ly
  • Kappa: mag 4.31, dist 238ly
  • Zeta: mag 4.31, dist 154ly
  • Delta: mag 4.21, 906ly
  • Sheliak: mag 3.50, 882ly
  • Sulafat: mag 3.25, 640ly
Lyra Constellation Stick Figure

Lyra Constellation Stick Figure

The next image is modified to reduce the fainter stars and is more representative of what the sky might look like from a dark site. With this image, the bright stars of the constellation Lyra are more obvious.

Vega in the constellation Lyra - Less Stars -2015-10-30

Vega in the constellation Lyra – Less Stars -2015-10-30

While we think of constellations as the stick figure above or the elaborate drawings of mythical figures, the IAU defines a constellation as a non-overlapping region. So Lyra extends a little past the obvious 7 bright stars and defines a region in the sky between Cygnus to the east and Hercules to the west.

Lyra Constellation Boundaries

Lyra Constellation Boundaries

Lyra is home to a few interesting night sky objects:

Within the “stick figure” there are:

  • Epsilon – the double double
  • Messier 57 – The Ring Nebula
  • Zeta, Delta and Sulafat are doubles

Within the boundaries there are also:

  • M56 – an 8.3 magnitude globular cluster with an apparent size of 5arc-minutes
  • NGC 6791 – an 9th magnitude open cluster spanning 19′

The pair of stars Epsilon Lyra 1 and 2 (ε1, ε2)  are gravitationally bound to each other – meaning they are in the same region and rotate around each other (although in thousands of years). Each of ε1, ε2 is also a pair of stars that can be seen as doubles though a medium to large telescope. ε1, ε2 have a separation of 3.5′ which can be seen in binoculars. The doubles of ε1, ε2 each have separations of 1.3″ and 2.3″ making them challenging doubles to split in a 4″ scope. However, the two pairs are oriented 90° with respect to each other making it easy to compare the star shapes and aiding in detecting the separation. The periods of each pair are in the range of 600 to 1200 years. The finder chart below helps when trying to “split” the doubles.Finder_Chart_Epsilon-Lyra

The image below of the double-double doesn’t quite manage to show a gap between the close pairs. This is what might be typically seen in a smaller scope or a night of poor seeing. Still, by noticing that each pair is actually oval shape, the direction at least of the doubles gives a clue that they are doubles.

DoubleDouble_Epsilon_Lyra_2008-06-10_v1_SJM

Messier 57 (NGC6720) – the Ring Nebula is a large bright planetary nebula. Its visual magnitude is 9.5 and 3 arc-min across. On good nights and a large telescope, the remnants of the central star that exploded is visible. The ring is the expanding cloud of hot gas thrown off when the star shed its outer shell. The image below easily captures this detail as well as the colour which is not discernible through the eyepiece.

M57 - Ring_Nebula - 2011-07-30 - v2

M57 – Ring_Nebula – 2011-07-30 – v2

Vega rises during the late evening in April. It will be low in the north-east at about 9:30pm edt mid-April and makes its way across the sky during the night. By midnight it’s still in the north-east and only 25° above the horizon. It doesn’t transit (crosses due south) until 6am though!

Of course, if one is willing go out at much later times, Vega is also visible in the winter but after midnight. I tend think in terms of what objects are visible during normal evening hours.

Lyra Finder Chart - Sky facing East on 2015-04-15 at 21:30hrs EDT

Lyra Finder Chart – Sky facing East on 2015-04-15 at 21:30hrs EDT

Each month Vega rises two hours earlier. Which means it transits two hours earlier each month. By late summer at 9:30pm edt, Vega is due south and high in the sky near the zenith. The chart below shows Vega and Lyra high in the sky due south nestled between Pegasus and Hercules.

Lyra Finder Chart - Sky facing South on 2015-09-01 at 21-30hrs EDT

Lyra Finder Chart – Sky facing South on 2015-09-01 at 21-30hrs EDT

By December, Vega is low in the west in the evening and soon will disappear altogether from the evening sky.

Lyra Finder Chart - Sky facing East on 2015-04-15 at 21:30hrs EDT

Lyra Finder Chart – Sky facing East on 2015-04-15 at 21:30hrs EDTj

But … as said earlier, if one wanted to go out at other times, Vega can still be seen during winter. Starting in December, Vega is also visible in the early morning sky! The chart below shows Vega rising at 6:30 am (when it’s still dark in Ottawa) the day after it set in the west on the evening before.

Lyra Finder Chart - Sky facing East on 2015-12-16 at 06-30hrs EST

Lyra Finder Chart – Sky facing East on 2015-12-16 at 06-30hrs EST

Each month Vega will rise 2hrs earlier. So in January it rises at 4:30am and in February it rises at 2:30. By April it will be rising at 9:30 again.

So Vega is actual visible all year long, but to see it might mean going outside to look for it while sleeping is a better alternative.

 

 

 

 

 

Lunar Eclipse – 2015-09-27

The weather reports of the preceding days and even the day of the eclipse predicted clear skies. So i planned a photography project to create a time lapse sequence covering the entire event from penumbra advance, through total eclipse and then the receding shadow.

As it turns out, the clouds moved in about the time the eclipse started. By the time the umbra shadow started, there was a significant risk of total overcast. The clouds did manage to behave themselves for most of the waxing eclipse, but just before full eclipse the cloud cover was 100%.

I was using the Canon XS (filter removed) with the AstroTech 106 (AT106) mounted on the Skywatcher EQ5-Pro. The plan was to take images every 20sec for the duration of the event. To reduce disk space i choose the “S” setting of 1936×1288 pixels as having adequate resolution for a movie. Not having done this before, i was not prepared for the changes required in exposure settings. I started with ISO 400 and 1/2000s exposures (the scope is f/6.5). I had expected to adjust the EV (exposure value) as time went on to account for the diminished light of the eclipsing moon, but was not prepared the problems caused by the clouds.

The intermittent cloud cover exacerbated the changes to EV making it somewhat unexpected if not random. This and required dramatic changes to the TV time during periods of partial cover resulted in widely varied exposure values. I ended up with frames that were too dark as well as too bright. And whole sequences that differed substantially from the previous frames.

Because of the location require to get a clear view of the entire eclipse, it was not possible to pre-align the scope. So i also had to contend with Polar Alignment  drift between frames. This required minute by minute adjustments to the framing to keep the moon more or less in the centre of the frame. I was hoping for some auto-alignment tools to refine this during post-processing (more later).

The cloud cover was 100% a few minutes before full eclipse. I decided to abandon the time lapse project in favour of getting a high resolution RAW file of the mostly eclipsed moon. I managed only one full resolution image before the clouds covered up everything, I also choose ISO 1600, which is quite noisy on the XS with only 1/10s exposure. Lower ISO and longer exposure would have provided a cleaner image.

Lunar Eclipse 2015-09-27

Lunar Eclipse 2015-09-27

I did mange to grab 360 frames at the lower resolution to create a time lapse sequence of the event. I could not find a tool to accurately align the  images, so i manually aligned them with the Canon DPP tool. This allows alignment to the pixel level, which is adequate, but still not quite good enough. I also had to manually adjust the EV levels for groups of images as well as individual images. The resulting movie is at best interesting but not quite the epic i had planned.

The video covers the time period from 8:04pm to 10:06pm EDT. The penumbra shadow started at 8:12 with the umbra starting at 9:07. Full eclipse started at 10:11. It takes quite awhile before the penumbra is evident.

The video compresses the 122 min lapsed time into 36 seconds. So each second of video is about 3 1/2 min of real time.

Hornets -2015-09-08

I opened up the observatory this evening for a quick test of some upgraded software and a mini-guider using a finder scope. I did a quick scan of the roof before opening it to check for bugs – wasp and hornets in particular. I didn’t find anything untoward so i opened up the roof and went to work.

As there were a few misquotes and black flies, even this late in the summer, i started the Thermocell. Good thing as it it turned out.

About a half an hour into the project a large bug crawled across the laptop screen. I thought it was a medium sized spider – which i am needless to say, not too fond of. I switched on the white light light to get a better look and found not a spider, but a large hornet! Looking up, i then saw the hornets nest on the side of the dome wall and about 18″ from my nose!

I made a hasty retreat to a comfortable distance and perused the situation. The nest was small but active. It was only about 3″ by 6″ but there were a dozen or more hornets crawling around it and many more near by. They were however rather docile for hornets which i attribute to the Thermocell.

I gingerly shutdown the laptop and closed the cover of the cupboard it’s housed in. I shutdown the mount without bothering to return it to home or even hibernate. Then i went to the garage and fetched a hornet blaster. I soaked the nest and targeted several stray hornets. In the morning there were still many live hornets to be dealt with.

More frightening than realizing the nest was basically in my face, was the thought that i nearly put hand in the nest. The observatory is a skyshed pod. The half roof opens and then the open half dome is rotated around to face the sky being observed. To move the dome i just push on one of the supports which was only inches from the nest. Had the nest been located nearer to the support, i would have put my hand directly onto the nest. Yikes!

Hornets are gone and i think i will check the observatory in daylight more frequently.

The Sky for January 2014

For those attuned to western numerology, they are finally out the year xx13. In Asian cultures 4 is considered unlucky, so perhaps xxx4 will not be a good year for some people.

Winter is upon us in Northern America and aside for short walks for the dog, venturing outside in -25c temperatures in the dark is only done as a necessity and not for the pleasure of viewing the winter sky. However, the winter sky in North America does offer some spectacularly sites.

January Sky 2013

January Sky 2013

Winter Hexagon

Winter Hexagon

 

Orion, one of the most recognizable constellations, is front and centre in January. Surrounding Orion is the “Winter Six” – 6 of the brightest stars in the northern hemisphere arrange in a hexagon. At 9pm mid-month, Orion is about south-east. The winter six – Sirius (m -1.6), Procyon (m 0.4), Pollux (m 1.2), Capella (m 0.1), Aldebaran (m 0.8) and Rigel (m 0.2) surround Orion.

Orion The Hunter is home to a number of interesting and very accessible night sky objects. The Orion Nebula (M42) is a very bright and large HA emission nebula surrounding the middle star or Orion’s sword.
Unadied, the middle star of the sword appears a bit fuzzy. With binoculars, its apparent that the “star” is actually several stars surrounding by a grey cloud. With a 4″ refractor, the “cloud” starts to take shape as a distinct luminous region. Careful oberservers will also note that the “star” at the centre of the nebula is actually a multiple star. Visually it appears as a group of 4 stars known as the “trapezium”. Even Galileo observed this multiple star system and even noted the 5th and 6th memmbers of this complex multiple star system.

Abell 1656 – Coma Cluster – 2015-05-18

Coma Cluster (Abell 1656)
Imaged 2015-05-18

The Coma Cluster is a large cluster of galaxies that contains over 1,000 identified galaxies. Th image below shows a just a few hundred. The magnitudes of the ten brightest galaxies are between 12–14. The two largest galaxies at the centre are supergiant elliptical galaxies: NGC 4874 and NGC 4889. The Coma Cluster is part of the Coma Supercluster.

Abell 1656 - Coma Cluster - crop - 2015-05-18

Abell 1656 – Coma Cluster – crop – 2015-05-18

As its name implies, the cluster is located in the direction of the constellation Coma Berenices. While the three bright stars in the constellation are between 28 Mly and 167 Mly from us, the Coma Cluster of Galaxies is 321 Million lights years away.

The North Galactic Pole is located in Coma Berenices. So looking towards Coma Berenices is then looking up from the galactic plane and therefore there are fewer stars than when looking through the plane.

The Coma Cluster is one of the first places where dark matter began to be suspected. In 1933 Fritz Zwicky showed that the galaxies of the Coma Cluster were moving too fast for the cluster to be bound together by the visible matter of its galaxies. It is now thought that about 90% of the mass of the Coma cluster is dark matter.

Image details:
AT106 with AT2FF
Canon T2i (Astronomy UV/IR filter mods)
– 17 x 600sec frames at ISO1600 (total integration time 2hr 50m
CGE Pro
Guided with Shorttube 80 and Chameleon
Metaguide with FlexRX
Image capture with Backyard EOS
Calibrated, stacked and processed with PixInsight
Cropped, original pixel scale

M96 Group in Leo – 2015-04-14

M96 Group in Leo (the Leo I Group)
acquired 2015-04-14

The image below shows 5 of the 8 brightest galaxies in the M96 group. There are estimated to be as many as 24 galaxies in the group, all of which are in the same general vicinity and gravitationally bound to each other.

M96 Group - 2015-04-17

M96 Group – 2015-04-17

From left to right:

NGC 3384
– Mag 10.9
– Size 5.5′ x 2.5′
– Distance     35.1 Mly
M105 (NGC 3379)
– Mag: 10.2
– Size: 5.4′ x 4.8′
– Distance: 32 Mly
NGC 3389/3373 (Below NGC 3384)
– Mag: 11.2
– Size: 2.7′ x 1.2′
– Distance: ?
M96 (NGC 3368)
– Mag : 10.1
– Size: 7.6′ x 5.2′
– Distance: 31 Mly
M95 (NGC 3351)
– Mag: 11.4
– Size: 3.1″ x 2.9′
– Distance: 32.6 Mly

There are few other faint fuzzies that may not be part of the group. While visually in the field of view, they are either closer or further away from the M96 cluster of galaxies.

Taken 2015-04-18
AT106 with A2FF
Canon T2i (astrodon UV/IR inside)
14 x 360s @ISO1600 (another 28 subs had lost the guiding)
– total integration 1hr, 24min
CGE Pro guided with Shorttube80 and Chameleon
– Metaguide with FlexRX
Captyured with Backyard EOS
Calibrated, Stacked and Processed with PixInsight
Full Frame, original pixel size.

Eskimo Nebula – 2015-03-23

Eskimo (Clown) Nebula (NGC 2392, Caldwell 39)
Taken 2015-03-23, 21:00 to 23:30edt

Eskimo Nebula - Full Frame - 2015-03-23

Eskimo Nebula – Full Frame – 2015-03-23

This is a planetary nebula called the Eskimo Nebula or sometimes Clown Face Nebula. Planetary nebulas get their name because they appeared to early telescope observers like giant planets. They are actually an expanding shell of ionized gas ejected from a catastrophic event in the late stages of medium to small star’s life. (Contrast this to supernova for giant stars.) The Eskimo nebula actually has two shells of expanding gas which gives it an unusual appearance.

Distance 3000 light years
Apparent mag 9.1
Central star mag 10.5
Visual Size 48 x 48 arc-sec

A closer crop and up-sampled 2x is easier to look at, but does not show any more detail:

Eskimo Nebula - - Crop - 2015-03-23

Eskimo Nebula – – Crop – 2015-03-23

Celestron HD11
Canon T2i with Astrondon uv/ir filter inside
Guided with Celstron OAG, Chameleon and Metaguide

HDR at ISO1600
– – 15 x 120s
– – 7 x 180s
– – 18 x 240s
– total integration 2hrs

Venus and Mercury – 2015-05-06

Mercury

Mercury was at its greatest elongation for 2015 om May 6th at 21deg, so i decided to try to capture an image of it. Being low in the sky it’s hard to get a clear view through the murky unstable surface air. So i decided to capture the image just after sunset at 20:19edt when it was still relatively high. Mercury was not yet visible unaided, but it showed up well in the telescope. The sun had just set at 20:16 when i captured the image, so it was only 0.5deg below the horizon. Nautical dusk wasn’t until 21:31. The down side was the bright evening sky reduced contrast. Given it’s very difficult or unusual to resolve any surface details of Mercury in a backyard telescope, the lack of contrast wasn’t going to matter.

Mercury 2015-05-06, 20-19edt

Mercury 2015-05-06, 20-19edt, Monochrome

Being only 7.9″ in angular size, it is very difficult to resolve any surface details at the best of times. And being so low in the sky and taken only minutes after sunset, the unstable surface air and low contrast obscured what details might be obtainable. The only interesting feature then is the phase. Mercury is also grey, like the moon, so a colour image wouldn’t actually have any colour.

I used the Celestron HD11 with a 5x Powermate. The effective focal length is therefore 14,000mm at effectively f/50. I capture a 60sec AVI (movie) at a resolution of 640×480 at 30fps with a monochrome Point Grey Chameleon (no filters). That works out to 1792 frames. Using Autostakkert2, i selected the best 10% of the frames and stacked them into a single image. Further processing with PixInsight (wavelets and curves) sharpened up the edges to reveal a nice waxing crescent – but no surface detail.

The specs for Mercury that evening were:

  • Mag: +0.4
  • Size: 7.9 arcsec
  • Illumination: 38%
  • Azimuth: 286deg
  • Altitude: 18deg
  • Elongation from Sun: 21deg (at maximum)

I tried using a 35nm IR pass filter with the above setup, but at f/50, there wasn’t enough light. The advantage of using IR is it less affected by the turbulent air and the narrow bandwidth improves focus. A future project is to try the IR filter with the HD11 at prime focal length or with a 2x powermate.

Venus

Venus was at a greater elongation [from the sun] so i waited until 21:04edt to capture that image. The sun was now 7.5deg below the horizon and closer to nautical dusk (21:31).

Using the same technique above, i captured two 60sec AVIs and processed them with the same method. Then i combined the two resulting images which reduced some blotches.

Venus 2015-05-06, 21:04edt

Venus 2015-05-06, 21:04edt, Monochome

Venus is blanketed by a thick white cloud, but unlike Jupiter and Saturn, there is no colour or banding visible in white light. (I have seen some images in UV that do show some some cloud details.) So even though Venus is a reasonable 18arcsec in angular size, the only interesting feature is the phase.

The specs for Venus that evening were:

  • Mag: -4.14
  • Size: 18 arcsec
  • Illumination: 64%
  • Azimuth: 280deg
  • Altitude: 28deg
  • Elongation from Sun: 43deg (maximum is 45deg)

Venus and Mercury Comparison

Since i had the two images created with the same gear, i decided to display them side by side to show the relative angular sizes:

Venus and Mercury 2015-05-06

Venus and Mercury 2015-05-06

 

Examples of What Other People Can Do

While it’s difficult to get images that show any detail on either Mercury or Venus, it is possible to capture images using relatively modest ground based equipment (not billion dollar mountain top scope). The links below to Daniele Gasparri’s web site [external link] show some impressive images that have been acquired using a C14 combined with various filters.


Mercury by Daniele Gasparri [External Link}


Venus by Daniele Gasparri [External Link}

Super Moon versus Micro Moon – 2015-03-05

The term “Super Moon” appears in the popular press to describe the full moon when it appears the largest. This occurs when the moon is at its closest to the earth (Perigee). The term gives the impression this is an extraordinary or even catastrophic event. Exaggerated media reports often predict flooding, earth quakes and even volcanic eruptions. Most of which of course are false. It is true that that when the moon is at its closest to the earth the tides can be somewhat higher and an alignment of the sun, earth and moon does have a measurable affect – just not extreme. And if this occurs in the spring, during a spring tide (not the same thing), then the tides can actually be a concern.

The opposite of the “Super Moon” is the “Micro Moon” which describes the smallest full moon. This occurs when the moon is at its furthest from the earth (Apogee).

The difference between the super moon and micro moon is not likely to be noticeable when viewing the moon in the evening sky. But the side by side comparison below of the super moon taken 2014-09-08 and the micro moon taken on 2015-03-05 shows just how different they are!

Super Moon - Micro Moon Comparison

Super Moon – Micro Moon Comparison

The Perigee Full Moon can appear as large as 34.1 arc-minutes (apparent angular size). While the Apogee Full Moon can appear as small as 29.3 arc-minutes (Wikipedia). That’s about a 15% difference. The difference in apparent size is a result of the moon being different distances from the earth.

The moon orbits the earth in an elliptical path (an oval) at an average distance of 385,000km. At its closed point – perigee – the moon is 362,600km from the earth. At its furthest point – apogee – the moon is 405,400 km away from the earth. That’s an 11% difference! The shape of the orbit is constant, so once a lunar sidereal month (360° rotation) of approximately 27.3days, the moon is at its closest to the earth, and about 2 weeks later, it is at its furthest. (It takes 29.5 days for the moon to complete a synodic orbit which returns the moon to the same orientation relative to the sun and earth – e.g. new moon or full moon.)

Moon Elliptical Orbit

Moon Elliptical Orbit

The phase of the moon – the part we see illuminated – depends on the alignment of the sun, earth and moon. As the moon orbits the earth, we see a different portion of the sunlight part and the part in shadow (although we always see the same side of the moon). For example, when we see the waxing crescent moon, the moon is between us and the sun and a little to the left of the sun from the perspective of earth’s northern hemisphere. So the part in sunlight is facing mostly away from us and we see only a small sliver of that. The rest of the moon’s face we see is mostly in shadow.

Waxing Crescent Moon

Waxing Crescent Moon

As the moon orbits the earth, we see a portion of the sunlit part from a different angle. So we see different phases at different points in the lunar orbit.

Phases of the Moon

Phases of the Moon

A full moon occurs when the sun, earth and moon are aligned (in that order) – referred to as “opposition”. A new moon on the other hand occurs when the moon is between the sun and the earth – referred to as “conjunction”. Although aligned when viewed from above, when viewed from the side, the full moon or new moon is usually above or below the earth-sun plane (the ecliptic). This is because the moon’s orbit is tilted compared to the earth-sun orbit by about 5.1°. When the side view also lines up, we get a solar or lunar eclipse.

An “ordinary” full moon can happen at any point around the moon’s elliptical orbit, so the earth-moon distance can be anything between the closest and furthest distance. In the diagram above, the full moon is a little past perigee and so not at its closest. Occasionally the full moon occurs when the moon is at perigee (closest). Because it’s at its closest, it appears larger than other full moons that occur at other points in the lunar orbit. This is what’s called the “Super Moon”!

Perigee Full Moon Alignment

Perigee Full Moon Alignment

But the moon is going to be at perigee at some point in every lunar month. For example, from the “Lunar Phases” diagram above we see the waxing gibbous moon is at perigee and therefore would appear larger than other gibbous moon views. What makes the Perigee Full Moon a “Super Moon” is that the sun-earth and moon are aligned so the combined effect of their gravity is also at a maximum. The affect is measurable and at some times of the year can result in significant, but still modest increase in tides. Hence the term “Super Moon” which is chosen to evoke a sense of awe and unfortunately panic.

The compliment to a Perigee Full Moon is the Perigee New Moon. Like the full moon, occasionally the new moon occurs when the moon is at perigee (closest).

Perigiee New Moon Alignment

Perigiee New Moon Alignment

Also like the Perigee Full Moon,  the sun-earth and moon are aligned for a Perigee New Moon, so the combined effects of their gravity is also at a maximum. Since the moon and sun are on the same side during a new moon, their gravitational affects on the earth add together. I would expect any noticeable affects to be larger than the equivalent Perigee Full Moon. The term “Super Moon” then also applies to the Perigee New Moon, but because the new moon is directly in line with the sun, we can’t see it, and hence goes unnoticed and generally unreported.

The alignment of a full moon at perigee occurs about every 14 full moons. Relaxing the definition of “Super Moon” a little to occurring close to perigee, we can get a perigee new moon before and after a perigee full moon. (Or conversely a perigee full moon before and after a perigee new moon.) This means it’s possible to get 3 “Super Moons” in a calendar year; most times 2 (a full moon and a new moon) and rarely no “Super Moon” in a calendar year. (There are 12 and sometimes 13 full moons in a calendar year. )

On the other end of the scale, the new moon and full moon can occur when the moon is at apogee – furthest away. When this happens the moon will appear its smallest and the combined gravitational affects of the moon and sun will be at a minimum when compared to other new and full moon events. The complimentary term is sometimes “Micro Moon”.

When the new moon occurs at apogee, nothing really happens and since we can’t see it in the glare of the sun, it’s pretty much a non-event.

Apogee New Moon Alignment

Apogee New Moon Alignment

When the full moon occurs at apogee, again nothing happens, but we do get to see it. While it is 15% smaller than the perigee full moon, it’s not something that anyone would notice.

Apogee Full Moon Alignment

Apogee Full Moon Alignment

Our perception of the size of the full moon is influenced to a much greater extent by the foreground. For instance, people generally report that the full moon on the horizon is significantly larger than the same moon high overhead. Although in reality, they are the same angular size. There is no mysterious atmospheric affect at play, only our own perceptions.

The precise prediction of when a perigee or apogee moon will occur is a little complicated.

  • it takes the moon about 27.3days to make a 360° trip around the earth
  • but the earth has moved around the sun in that time so it takes about 29.5 days between full moons (or new moons)
  • the earth takes 365-1/4 days to move around the sun changing the earth-sun alignment with the major axis of the moons elliptical orbit as it goes
  • the lunar orbit precesses (the axis of the orbit rotates) once every 3232.6 days or about 8.85 Earth years which also changes the earth-sun alignment with the major axis of moons elliptical orbit
  • so working out all these moving parts to find an alignment is complicated
  • then there is the affects of the other planets on the orbits (perturbations) and tides which changes the shape of all the orbits and speed of rotation

Micro Moon – 2015-03-05

To complement the “Super” moon of September 9th, 2014, the moon was at it smallest for 2015 on March 5th. The conditions were almost just as good as in September 2014, so i managed to capture a view of the apogee full moon (furthest away) that was almost indistinguishable from the Super moon expect that it was 10% smaller.

Micro Moon - 15.14days - 2015-03-05

Micro Moon – 15.14days – 2015-03-05