Continent in the Sky


Shining overhead on northern summer nights right now is the blue supergiant star Deneb, in Cygnus. Nearby glow the magenta clouds of the North America Nebula.

This image shot with a telephoto lens takes in roughly the same field of view as a pair of binoculars. But being a long time exposure it reveals much more of the faint nebula than even the aided eye can see. However, even binoculars will show a greyish cloud near Deneb in roughly the shape of North America. It is actually a continent of stars and hydrogen gas, glowing with hydrogen’s characteristic magenta colour, a mix of deep red and blue emission lines. The gas may be electrified into glowing by the searing radiation from the star Deneb, some 1400 light years away from Earth.

I shot this on a July night, with some haze passing by during some of the exposures. The haze added the photogenic glows around the stars.

— Alan, August 8, 2012 / © 2012 Alan Dyer

The Stellar Triangle of Summer




When the Summer Triangle sinks into the west, we know summer has come to an end. While the stars of the Summer Triangle are now high overhead from northern latitudes as the sky gets dark, by late evening the Summer Triangle is setting into the west.

These three bright stars are an example of stellar variety:

– At bottom is Altair in Aquila the eagle. It’s a white main-sequence star 17 light years away, fairly nearby by stellar standards. Leslie Nielson and his crew went to Altair in the 1950s movie Forbidden Planet.

– At top right is Vega, in Lyra the harp, a hotter and more luminous blue-white star than Altair, making it appear brighter than Altair, despite Vega being farther away, at 25 light years distant. Jodi Foster went to Vega in the movie Contact.

– But the third member of the Triangle, Deneb, at top left, is an extreme star. It appears a little fainter than Vega, but looks can be deceiving. Deneb is actually a luminous supergiant star, putting out 54,000 times the energy of our Sun. Deneb is about 1,400 light years away and yet, due to its fierce output of light, appears almost as bright as Vega. Light from Deneb left that star in the 6th century. I don’t know of any movie heroes who went to Deneb. The name means “tail of the Swan,” hardly a romantic destination for space-faring adventurers.

Look toward the Summer Triangle and you are looking down the spiral arm of the Milky Way that we live in. The stars of that arm appear as a packed stellar cloud running through Cygnus the swan, the constellation that contains Deneb.

I took this shot Saturday night, from home, on what turned out to be a very clear night, once some clouds got out of the way in the early evening. This is a 4-image stack of 8-minute exposures, at f/4 with the 35mm Canon lens, a favourite of mine, on the Canon 5D MkII at ISO 800. I added in exposures taken through a soft-focus filter to give the added glows around the stars to help make the bright stars and their colours more visible.

— Alan, September 25, 2011 / Image © 2011 Alan Dyer

September Milky Way


 

This was the scene from my rural backyard on Tuesday night, September 20, with the Milky Way at its best across the sky.

September usually brings the best nights of the year for dark-sky observing and shooting the Milky Way. Nights are clear, dry, and transparent. The Milky Way stretches across the sky from southwest to northeast in the early evening.

Under clear skies on Tuesday the dark lanes and structure of the Milky Way really stood out, both to the eye and to the camera. Image processing for contrast does bring out the dust lanes, including the subtle patches off the main Milky Way band.

The centre of the image contains the three bright stars of the Summer Triangle. They frame the bright Cygnus starclouds and glowing red nebulas that mark the spiral arm that we live in. Above, at top left in the image, is a bluer section of the Milky Way formed by the more distant Perseus spiral arm, the one further out from us in the Galaxy.

I took this shot with the Canon 5D MkII and Canon 15mm lens, for a stack of five 6-minute exposures at f/4 and ISO 800.

— Alan, September 21, 2011 / Image © 2011 Alan Dyer

 

The Glowing Heart of Cygnus


Look straight up on a summer night in the northern hemisphere and you are looking into this region of sky. This is the centre — the heart — of Cygnus the swan, marked here by the bright star called Sadr, or Gamma Cygni.

While the star is easily visible to the unaided eye, the glowing clouds of gas surrounding it are not. Only long exposure images reveal the amazing swirls of nebulosity in the middle of Cygnus.

The main cloud at left, split by a dark lane of dust, is catalogued as IC 1318. The little crescent-shaped nebula at right is NGC 6888, or more appropriately, the Crescent Nebula. It formed when a hot giant star blew off its outer layers, to add to the general melee of hydrogen and other elements. But note the little blue reflection nebulas at top left. Oddly out of place!

New stars are forming in this region, located about 1500 light years away down the Cygnus arm that we live in, in the Milky Way Galaxy.

This field can be framed nicely by binoculars or a low-power telescope, but only the brightest bits of this nebulosity will show up in the eyepiece as grey ghosts, and then only with the aid of a specialized nebula filter.

I took this shot on Saturday night, July 30, 2011 with the Borg 77mm f/4 astrograph lens and Canon 5D MkII camera. Other stats are similar to the previous blog post. It’s certainly my best shot of this area of sky.

— Alan, August 1, 2011 / Image © 2011 Alan Dyer