Category Archives: Astrophotography

Posts related to astrophotography including posts including a new astrophoto

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

The Pelican in the Nebula – 2015-01-12

I always struggle to get my imagination to see where an astronomical object gets its name. My recent image of the Pelican Nebula (IC 5070) was no exception. I could not find a drawing that showed the pelican and there are only limited and conflicting descriptions of where the pelican is. So i decided to make my own sketch.

IC5070 - Pelican Nebulae - 2014-10-24 - 2views

IC5070 – Pelican Nebulae – 2014-10-24 – 2views

Images of Comet c/2104 Q2 (Lovejoy) – 2015-01-19

Using a Stellavue 80mm APO (with 0.8x reducer) and a Canon T2i, i took some images of comet Lovejoy. The main imaging run was 30 x 2 min exposures at ISO1600. The comet is bright enough that the core is blown at this exposure. So i also took a series of shorter exposure sets at 60s, 30s and 15s. Unfortunately, i could not create a high dynamic range image (HDR) with the short exposures – either automatically with the tools i have nor manually.

I was guiding on a star and not accounting for the relative motion of the comet. At 2 min expsoures, it’s manageable as the comet is not moving so fast that it would show any noticeable signs of being stretched in each frame. However, after an hour it had moved considerably in the FoV, so each frame had to be realigned to the comet’s new location. The 30 aligned frames were then stacked with a rejection filter. This provided the best image of the comet at the expense of dimming the background stars. (A simple averaging would keep each star and the result would be a line of stars giving the impression the comet was racing past them – which it is.)

Comet c2104 Q2 Lovejoy 2015-01-19 comet aligned

Comet c2104 Q2 Lovejoy 2015-01-19 comet aligned

The part of the tail visible in the image above is 2.2deg wide. This works out to 3.3Mkm in actual length and that’s not all the tail. The distance from earth to the comet was about 85 Mkm when the image was taken.

To get an image with the background stars, i reprocessed just 5 of the images and aligned on the stars. Even with a 10min lapsed time, the comet is still not stretched too much in the final image.

Comet c2104 Q2 Lovejoy 2015-01-19 star aligned

Comet c2104 Q2 Lovejoy 2015-01-19 star aligned

North America and Pelican Nebula – 2014-10-24

The region around the brightest star Deneb in the constellation Cygnus is occupied by a giant cloud of ionized molecular hydrogen (H II or H2) which is categorized as an “emission nebula”. Three degrees towards the north are two nebula named the “North America Nebula” (NGC 7000) and the “Pelican Nebula” (IC 5070).

NGC7000-IC5070 - North America and Pelican Nebulae - 2014-10-24 v1

NGC7000-IC5070 – North America and Pelican Nebulae – 2014-10-24 v1


The image spans 3.2 x 3.0 degrees which translates to an object size of 96 x 89 ly

The interesting  “North America” shape is caused by interstellar dust blocking some of the light from the nebula. Therefore the stars in the “”Gulf of Mexico” are in front of the dust and closer to us than the actual nebula. The peninsula is referred to as the “Cygnus Wall” and the bright filaments along the wall are regions of intense active star formation.

IC5070 - Pelican Nebula 2014-10-24 v3 high contrast

IC5070 – Pelican Nebula 2014-10-24 v3 high contrast


The Pelican nebula is supposed to look like a pelican taking flight. With the low contrast in my image it’s hard to make out. The pelican is facing towards us and to the left. The top of it’s head is the peak above the bright filament in the upper centre and it’s full beak is pointing down to the left and formed by the cloud along the upper left edge of the nebula. The vertical filament itself outlines the back of the pelican’s neck. The right part of the nebula is then the bird’s right wing on the downward part of a stroke. The left wing would be behind the pelican’s beak.

The pelican shows up better in the high contrast version of just IC 5070 (reprocessed from the same image above).

Generally emission nebula are difficult to see. Although quite large and bright in H-alpha, it is not possible to see this object unaided. The ionized hydrogen glows strongly deep red from the primary Blamer series Hα (hydrogen alpha) at 656nm. Unfortunately our night time vision (scotopic vision) tops out at 620nm, so we cannot see the Hα faint red glow. (Our day time vision – photopic vision – can see deep reds up to about 750nm when they are bright daylight intensities.) But the nebula also glows in other wavelengths so it is possible to see it.

There are some reports that the formation can be seen with binoculars or a small telescope using a UHC filter. I suspect this has to be done under dark skies and ideal conditions. I have never been able to make it out from my semi-rural location.

North America Nebula
– Magnitude: 4.0
– Angular Size: 120 x 100 arc-min
– Distance: 1,600 ly

Pelican Nebula
– Magnitude: 8.0
– Angular Size: 60 x 50 arm-min
– Distance: 1,800 ly

This is a two pane mosaic. The left part of the NA Nebula is from a data set acquired 2010-10-09 using a TV Pronto and Canon XS. The right side of the image, including a good portion of the NA nebula and all of the Pelican Nebula was acquired 2014-10-24 with a Stellarvue 80mm APO and a Canon T2i. The Pronto and SV80 have the same FL of 380mm, but the cameras are different so the image scales of the two sub-frames are different. The Pronto image was up-scaled to match the image scale of the Canon T2i and then aligned and merged to form the composite image.

Super Moon 2014-09-09

A “super moon” occurs when the moon is full (or new) and is also at it’s closest approach to the Earth (perigee). When this happens, the full moon appears bigger and brighter compared to other full moons. The difference in size is only 16% compared to the smallest full moon – a full moon at apogee or micro moon. So it’s actually very hard to notice the larger apparent size unless you see the super moon presented beside the micro moon.

While i don’t like the term “Super Moon” the media has latched onto it, so that’s what i’ve call this post. The correct term according to wikipedia is “perigee-syzygy of the Earth-Moon-Sun”. Ok, doesn’t roll off the tongue very well. But a simpler term is “perigee moon”. Perigee meaning the point where the moon is closest to earth during it’s monthly orbit. Both a full moon and new moon at perigee are considered a “super moon”, but the media doesn’t seem to care about the new moon event. (At new moon you can’t actually see the moon since it’s directly in line with the sun.)

When a full moon or new moon occurs, the sun, earth and moon are aligned so their mutual gravitational forces are also aligned and the combined affect on the earth’s oceans is at it’s greatest. At perigee the moon’s gravitational pull on the earth is also at a maximum. So the combined affect of the sun and the super moon can have a mild affect on tides. And if a perigee moon occurs in spring when tides are already at their highest, the additional affects of a perigee moon can be noticeable.

It’s always reported in the media that the perigee full moon makes the tides higher. But it occurs to me that at full moon, the moon and sun are on opposite sides of the earth. So it would seem their gravitational pull on the oceans should cancel out and the tides would therefore be smaller. I don’t know if this is the case however.

Usually there are 2, and occasionally just one perigee moon in a calendar year. The coincidence of full moon with perigee occurs every 13.94 months. The new moons before and after the full moon can also be at perigee so it’s possible to have 3 super moons in one calendar year. This occurred in 2014 with super moons on July 12th, August 10th, and Sept. 9th.

On September 8th, i took a photograph of the almost full moon just around sunset – or moon rise.

Super Moon 2014-09-07

Super Moon 2014-09-07

The next day was actually the super moon event and i took this photo:

Moon - Super Moon 2014-09-08 v2

Moon – Super Moon 2014-09-08 v2

M81-M82 – Bodes Nebula – 2014-04-24

The data for this image was collected in April but i didn’t get around to processing the image until last week. I was working through a new image processing workflow based on PixInsight. It didn’t really take 6 months to develop the process, it just took that long for me to get around to it.

Bode’s Nebula is in the constellation Ursa Major, and therefore towards the north. Until last year when the trees to the north came down, this target was out of view.

The data was aquired over three nights. However, there were a lot of technical problems (and operator error) so only 2 of the three nights produced usable results. And then only a partial set of the data from the other two nights was acceptable. Still, there is 5hrs of integration time which is enough to produce a reasonable image.

M81 (NGC 3031) Bode’s Galaxy
Face-on spiral galaxy in Ursa Major
Dimensions: 26.9 x 14.1 arc-min
Magnitude: 6.94
Distance: 11.8 mLy

M82 (NGC 3034) Cigar Galaxy
Edge-on spiral galaxy in Ursa Major
Dimensions: 11.2 x 4.3 arc-min
Magnitude: 8.41
Distance: 11.4-12.4 mLy

M81-M82 - Bodes Nebula - 2014-04-24

M81-M82 – Bodes Nebula – 2014-04-24

The bright star in the upper middle of M82 is a supernova SN 2014J which appeared 2014-01-21 at 19.20 UT. A close crop with an annotated view shows the location of the super nova.

M82 -SN 2014J - 2014-04-24

M82 -SN 2014J – 2014-04-24

NGC6946 – Fireworks Galaxy 2014-09-26 v2

The Fireworks Galaxy is technically in the constellation Cygnus, but it is quite a bit to the north. Until the trees were removed last year that obsecured the northern sky, circum polar objects were out of view.

NGC 6946 (Arp 29, Caldwell 12) – The Fireworks Galaxy.
Dimensions: 11.5 x 9.8 arcmin
Magnitude: 9.6
Distance: 22.5Mly (+/- 8Mly)

NGC 6946 - Fireworks Galaxy - 2014-09-26 v2

NGC 6946 – Fireworks Galaxy – 2014-09-26 v2

The data for the image was collected over three nights from Oct 24 to the 26th. Amazingly there were 3 clear night in a row all with good seeing. The total integration time is 15hrs which is a bit of a record for me.

Trapezium Project – 2014-01-22

Imaging the trapezium – the multiple star cluster at the centre of the Orion Nebula (M42).

Equipment:

Scope: EdgeHD 11 (focal length 2800mm, f/10)
– astro-tech diagonal (too cold to refocus for straight through config)

Camera: Canon T2i modified with astrodon UV/IR filter
– Pixel pitch advertised as 4.30 um
– Width: 22.30 x 14.90mm
– Active Pixels: 5184 x 3456
– Astro SW though uses 5202 x 3465 pixels.

Mount: CGE Pro
– unguided, no PEC, PA hasn’t been done in awhile

I calculate the resolution of this optical train as 0.32 arc-sec per pixel.

However, a platesolve using Platesolve2 (by Dave Rowe) and the UCAC3PS catalog results in a resolution of 0.266 arc-sec per pixel.

From a run last year with the HD11, 5x powermate and a chameleon webcam i got this result:

Trapezium with 6 members resolved

Trapezium with 6 members resolved – 2013-04-01

 

The table below are the stacked versions of several different exposures.
– The picture is a tight crop of just the trapezium with a moderate stretch. Something akin to what the camera does for a non-linear jpg.
– The platesolve is the result of the platesolve2 on the fits file.
– the fits file is the full frame of a the stack of the calibrated and aligned lights for that exposure. The data is linear 16bit RGB.

To download a .fits files, right click and select “save as”. (Clicking on the link just opens up the .fit file as a text file, which isn’t any good at all.)

Note that all fits files are align to the same master. So its possible to combine the individual exposures into an HDR.

trap_1x4s_iso400.fit
integration: 4 * 1/4sec at ISO400
pixels: 5202 x 3465
format: RGB, 16bit unsigned int
Download size: 105MB
trap_1s_iso400.fit
integration: 2 * 1sec at ISO400
pixels: 5202 x 3465
format: RGB, 16bit unsigned int
Download size: 105MB
trap_2s_iso400.fit
integration: 4 * 2sec at ISO400
pixels: 5202 x 3465
format: RGB, 16bit unsigned int
Download size: 105MB
trap_3.2s_iso400.fit
integration: 5 * 3.2sec at ISO400
pixels: 5202 x 3465
format: RGB, 16bit unsigned int
Download size: 105MB
trap_5s_iso400.fit
integration: 5 * 5sec at ISO400
pixels: 5202 x 3465
format: RGB, 16bit unsigned int
Download size: 105MB
trap_10s_iso400.fit
integration: 6 * 10sec at ISO400
pixels: 5202 x 3465
format: RGB, 16bit unsigned int
Download size: 105MB
trap_30s_iso400.fit
integration: 5 * 30sec at ISO400
pixels: 5202 x 3465
format: RGB, 16bit unsigned int
Download size: 105MB
trap_30s_iso800.fit
integration: 7 * 30sec at ISO800
pixels: 5202 x 3465
format: RGB, 16bit unsigned int
Download size: 105MB
trap_30s_iso1600.fit
integration: 6 * 30sec at ISO1600
pixels: 5202 x 3465
format: RGB, 16bit unsigned int
Download size: 105MB

Astrophoto Mare Vaporum – 2013-10-11

The rough patch of ridges south east of Mare Vaporum is quite an interesting formation. This greyscale image taken at about the 1st quarter moon shows nice details in the mountain ridged. A colour image taken a couple years ago when the lunation was a day later shows the region to be reddish brown compared to the surrounding area.

Pyroclastic formation south east of Mare Vaporum

Pyroclastic formation south east of Mare Vaporum

Pyroclastic formation south east of Mare Vaporum
2013-10-11 v1
Lunation 7.08days

The best information i found describes the area as being formed from material ejected from the Imbrium impact and then later overlaid by pyroclastics – ash from volcanic vents. I assume that the valleys of the original ridges were filled in at some point by basalt lava flows.

The formation seems to be unnamed despite being of considerable interest with observations dating back to the early 1800s. On the western ridge to the south is a formation that was once called Mt. Schneckenberg but has since been de-named. It has also been referred to descriptively as the “spiral mountain”. It has also been described as an /e/ shaped formation. On the eastern ridge, about mid way along the ridge, there is half a crater (looking like a cap). This is Hyginus N. The larger creator to the south, and mostly covered from a lava flow, is Hyginus W. Observers in the late 1800s thought it might be a new formation as it was not previously noted in detailed observations from the early 1800s even though the earlier observers had the equipment and skill to have seen it.

Image details:
Scope HD11 with tv 2x powermate
Chameleon at 1280×960 18fps.
Mosaic from 7 x 2min videos – 2200 frames.
Stacked best 10% (220 frames) with Autostakkert2
Processed with Pixinsight and Photoshop