M42 – The Amazing Sky

January 22, 2021

Tracks of the Geosats

This short video, below, captures time-lapses of the trails of geostationary satellites through southern Orion. It demonstrates the “crowded sky” we now have above us.

If you have tried photographing the Orion Nebula and Sword of Orion area with long tracked exposures you have no doubt seen these trails in your photos. Here I shot to purposely capture them in a time-lapse, for demonstration purposes.

Please note, these are not Starlink satellites. So do not blame Elon Musk for these!

These are the much more established geostationary or “geosynchronous” satellites that orbit 35,785 kilometres above Earth and so take 24 hours to orbit the planet. As such they remain apparently motionless over the same spot on Earth, allowing fixed dish antennas to aim at them.

(For more about geosats see the Wikipedia page.)

So why are they moving here?

The camera is on a mount that is tracking the sky as it turns from east to west, so the stars are staying still. What would normally be satellites fixed in one spot in the sky (after all, they are called “geostationary” for a reason) instead trail into short streaks traveling from west to east (right to left) in the frame. But in reality, it is the stars that are in motion behind the satellites.

The region of sky in Orion below the Orion Nebula (the object at top) lies south of the line that bisects the sky into northern and southern halves called the “celestial equator.” Most geostationary satellites also orbit in Earth’s equatorial plane and so appear along a belt near the celestial equator in the sky.

This chart from SkySafari shows the belt of geosats through southern Orion with the satellites identified. The green box is the field of view of the telescope (shown below) that I used to take the time-lapses.

In this video, however, they appear about 5° to 7° south of the celestial equator (which runs through the famous Belt of Orion off frame at top). That’s because I live north of the equator of the Earth, at a latitude of 51° north. So parallax makes the geosat belt appears south of the celestial equator in my sky. From a site in the southern hemisphere the geosat belt would appear north of the celestial equator.

You’ll notice some satellites travelling diagonally — they are not geosats. You’ll also see some flashing or pulsing satellites — they are likely tumbling objects, perhaps spent rocket boosters.

The satellites are visible because they are high enough to reflect sunlight even in the middle of the night, as the sequences each end about 11:30 to midnight local time.

But in this video the satellites are not flaring — this is their normal brightness. During flare season around the two equinoxes geosats can become bright enough to be seen with the unaided eye. For a video of that phenomenon see my video shot in October 2020, below.

TECH DETAILS FOR “TRACKS OF THE GEOSATS” VIDEO:

The video at top contains time-lapses shot on two nights: January 18 and 20, 2021. Both are made from hundreds of frames taken through a William Optics RedCat astrograph at f/5 with a 250mm focal length. The field of view is 8° by 5.5°.

The William Optics RedCat 51mm f/5 astrographic refactor.

Each exposure is 30 seconds long, taken at a one second interval. The camera was a Canon 6D MkII at ISO 3200 on January 18 and ISO 1600 on January 20 in the brighter moonlight that night.

In the first sequence from January 18 the equatorial mount, an Astro-Physics Mach1, is left to track on its own and is unguided. So the stars wobble back and forth slightly due to periodic error in the mount. The field also drifts north due to slight misalignment on the pole. Clouds pass through the field during the shoot.

In the second clip from January 20, taken with a quarter Moon lighting the sky, the mount was autoguided, using an MGEN3 auto-guider. So the stars remained better fixed over the 5.5 hours of shooting. A slight glitch appears near the end where I swapped camera batteries, and the camera turned ever so slightly causing the stars to enlarge a bit for a moment.

LRTimelapse at work processing the second sequence, deflickering some of the oddly exposed frames.

The frames were processed in Adobe Camera Raw and LRTimelapse

TimeLapse DeFlicker at work assembling the video, showing its All Frames + Lighten blend mode for the Accumulating version of clip #2.

I then assembled exported JPGs with TimeLapseDeFlicker, using a 3-frame Lighten blend mode to lengthen the trails. The final version was assembled with TLDF’s All Frames mode (shown above) where every frame gets stacked for an accumulated total, to show the busy sky traffic!

Thanks!

December 11, 2015December 14, 2015

The Wonder-Filled Winter Sky

Mosaic of the Wonder-filled Winter Milky Way

The sky of December contains an amazing array of bright stars and deep-sky delights.

At this time of year we peer out toward the edge of our Galaxy, in the direction opposite to what we see in July and August. Even though we are looking away from the centre of our Galaxy, the Milky Way at this time of year contains a stunning collection of sights – for the naked eye, binoculars or a telescope.

I can’t list them all here, but most are in the lead image above! The image is a mosaic of the northern winter Milky Way, including the brilliant stars and constellations in and around Orion the Hunter.

The Milky Way extends from Perseus in the north at top, to Canis Major in the south at bottom. Throughout the scene are dark lanes and dust clouds, such as the Taurus Dark Clouds at upper right.

The Milky Way is dotted with numerous red “hydrogen-alpha” regions of emission nebulosity, such as the bright Rosette Nebula at lower left and the California Nebula at upper right. The curving arc of Barnard’s Loop surrounds the east side of Orion. Orion is below centre, with Sirius, the night sky’s brightest star, at lower left.

The constellation of Taurus is at upper right and Gemini at upper left. Auriga is at top and Perseus at upper right.

There’s an unusually bright area in Taurus just right of centre in the mosaic which I thought might be an image processing artifact. No. It’s the Gegenschein – a glow of sunlight reflected off comet dust directly opposite the Sun.

Two highlights of this sky that are great regions for binoculars are the Hyades cluster in Taurus ….

The Hyades Cluster with Aldebaran — The Hyades open star cluster in Taurus with the bright star Aldebaran, not a part of the cluster iteslf. The smaller and more distant cluster NGC 1647 is at left. This is a telephoto lens image taking in a field similar to binoculars, and is a stack of 5 x 2.5-minute exposures with the 135mm lens at f/2 and Canon 5D MkII camera at ISO 800, plus two other exposures taken through the Kenko Softon filter to add the star glows. Taken from Quailway Cottage on Dec 7, 2015 using the iOptron Sky-Tracker.

…and the Belt and Sword of Orion.

The Hyades – the face of Taurus – is one of the nearest and therefore largest open star clusters.

Orion the Hunter, who battles Taurus in the sky, contains the famous Orion Nebula, here overexposed in order to bring out the much fainter nebulosity in the region.

The magenta and blue arcs in the image below are photographic targets, but the bright Orion Nebula in Orion’s Sword is easy in binoculars, shining below the trio of his Belt Stars.

Orion Belt and Sword Mosaic — A mosaic of the Sword and Belt region of Orion the Hunter, showing the diverse array of colourful nebulas in the area, including: curving Barnard’s Loop, the Horsehead Nebula below the left star of the Belt, Alnitak, and the Orion Nebula itself as the bright region in the Sword. Also in the field are numerous faint blue reflection nebulas. The reflection nebula M78 is at top embedded in a dark nebula, and the pinkish NGC 2024 or Flame Nebula is above Alnitak. The bright orange-red star at far right is W Orionis, a type M4 long-period variable star. This is a 4-panel mosaic with each panel made of 5 x 2.5-minute exposures with the 135mm Canon L-series telephoto wide open at f/2 and the filter-modified Canon 5D MkII at ISO 1250. The night was somewhat hazy which added natural glows on the stars. No filter was employed here. The camera was on the iOptron Sky-Tracker for tracking but no guiding. Shot from outside Quailway Cottage near Portal, Arizona, Dec 7, 2015. All stacking and stitching performed in Photoshop CC 2015. Stacking done with median combine stack mode to eliminate geosat trails through the fields.

For us in the northern hemisphere, Orion and company are winter sights. But for those down under, in the southern hemisphere, this is the summer sky. So pardon the northern chauvinism in the title!

Either way, on a dark, moonless night, get out and explore the sky around Orion.

TECHNICAL:

I shot the segments for the main mosaic at top on a very clear night on December 5, 2015 from the Quailway Cottage at Portal, Arizona. This is a mosaic of 8 segments, in two columns of 4 rows, with generous overlap. Each segment was made of 4 x 2.5-minute exposures stacked with mean combine stack mode to reduce noise, plus 2 x 2.5-minute exposures taken through the Kenko Softon filter layered in with Lighten belnd mode to add the star glows. Each segment was shot at f/2.8 with the original 35mm Canon L-series lens and the filter-modified (by Hutech) Canon 5D MkII at ISO 1600, riding on the iOptron Sky-Tracker. All stacking and stitching in Photoshop CC 2015. The soft diffusion filter helps bring out the star colors in this area of sky rich in brilliant giant stars.

December 7, 2013December 8, 2013

Orion and His Hunting Dogs in the Milky Way

Orion parades across the northern winter sky followed by his two odedient hunting dogs, Canis Major and Minor.

I shot the images for this panorama of the winter sky last night, December 6/7, on a frosty and cool night at our retreat in New Mexico.

The scene takes in Orion at upper right, with his signature stars, red Betelgeuse and blue Rigel, plus the dog stars Procyon at upper left (the brightest star in Canis Minor), and Sirius at lower centre (the brightest star in Canis Major). Canis Major itself appears in full at the bottom of the frame. Canis Major and Minor are depicted in mythology as Orion’s two Hunting Dogs .

The northern winter Milky Way runs from top to bottom of the frame, punctuated by patches of red nebulosity such as the circular Rosette Nebula above centre. Orion is wreathed in the sweeping arc of Barnard’s Loop, while his Belt and Sword contain the Horsehead Nebula and Orion Nebula.

While we are looking to the outer edge of our Galaxy in this view, this region of the Milky Way is one of the richest areas of star formation in the sky. It’s a wonderful field and lovely to shoot under civilized conditions in southern New Mexico, at the idyllic Painted Pony Resort.

For this mosaic, I shot 4 to 5 frames for each of the two mosaic segments, plus two images for each segment shot through a diffusion filter to add in the accentuated star glows. I stacked and stitched all of them using Photoshop CC.

So a total of 13 exposures went into the mosaic, each 4 minutes long, shot with the 35mm lens and filter-modified Canon 5D MkII, which helps bring out the red nebulosity.

As a footnote — this is Blog post #400 from me.

February 10, 2013

See, That’s the Orion Nebula!

What a hardy bunch we are in Canada, braving winter weather to see Orion and company.

A well-bundled group of sky fans partakes in an impromptu tour of Orion and his famous nebula.

I shot this scene last night, February 9, at the first of a series of monthly stargazing nights at the local university research observatory, the Rothney Astrophysical Observatory. About 120 people and volunteers gathered to take in the sights of the winter sky, as best they could as transient clouds permitted. Inside, speakers presented talks themed to the Chinese New Year, which is governed by the timing of the New Moon each year. As this was a New Moon night, people were able to stargaze under reasonably dark skies to see deep-sky sights such as the Orion Nebula.

Want to know where it is? An astronomy club member points it out rather handily with one of the best tools astronomers have for public outreach, a bright green laser pointer. Controversial and dangerous in the wrong hands, when used responsibly these laser pointers are wonderful for conducting sky tours.

As a side note, this is a 3-second exposure with a new Canon 6D camera at ISO 8000, yet the photo shows very little noise. In just 3 seconds, the Milky Way is beginning to show up! I could have gone to previously unthinkable speeds of ISO 12000+ and still had a presentable shot. This will be a superb camera for nightscapes and available light shots.

December 12, 2012December 12, 2012

The Amazing Orion Nebula

My Australian nights are proving to be frequently and thankfully clear enough that I’ve got the luxury of shooting some familiar “home sky” objects. This is the famous Orion Nebula in the Sword of Orion, about 1500 light years away.

I’ve shot this nebula many times from the northern hemisphere but my Australian skies are darker than at home, and the nights a lot warmer than when this object is up in our winter sky.

The Orion Nebula is a complex consisting of Messier 42, the main nebula, M43, a small nebula attached to the north (above) and the bluish Running Man Nebula (can you see his dark figure?) at top that is officially catalogued as NGC 1973-5-7. Together, these make up the largest region of star formation in our corner of the Milky Way. It’s easy to see with the unaided eye on a dark night.

To shoot this, I blended three different exposures, short (4 x 1 minute), medium (4 x 5 minutes) and long (4 x 15 minutes), to preserve all the details from the intensely bright core our to the faint tendrils extending into deep space. I stacked the 4 frames taken at each of the exposure times, then blended those stacks using masks in Photoshop CS6 (and its wonderful and editable Refine Mask function) to mask out the overexposed area of the longer exposure and let the shorter exposure content shine through. The result is that the core still shows the little cluster of stars, the Trapezium, and the characteristic green tint of the core. But I applied lots of Curves to bring out the fainter bits and swirls in the periphery.

I shot this through my Astro-Physics Traveler 105mm refractor at f/5.8 using the filter-modified Canon 5D MkII camera, at ISO 400. This turned out to be certainly my best shot of Orion yet in my library.

February 19, 2011February 21, 2011

Orion’s Sword Defeated!

Every astrophotographer has an object or field that seems to defy capture. For me, shooting the Sword of Orion has always been beset by haze, tints from light pollution and low altitude — something has always gone wrong. At last I managed to get a good shot of the region. It was a priority for me on my Australia trip of December 2010. Even though I ended up with only 2 clear nights to do any serious shooting, out of 15 I was there, I really wanted to grab this area, while Orion was high in the north, and higher in altitude than I can get it from home, so less hindered by sky gradient tints.

This is a shot with the wonderful Borg 77mm f/4 astrograph (which is tack sharp across the field) and the modified full-frame Canon 5D MkII camera — both items purchased from Hutech Scientific, a great source of astrophoto gear. This is a stack of five 7-minute exposures at ISO 800, processed in Photoshop CS5.