Astrophotography Highlight – The Cygnus Loop

The Cygnus Loop in the Hubble Palette.

As Summer draws to a close we find Cygnus the Swan nearly directly overhead by astronomical twilight. Cygnus is a narrowband wonderland overflowing with emission objects for both small and large fields of view. One fine example is the Cygnus Loop, or the Veil Supernova remnant. Formed by a supernova that occurred some 5,000 to 8,000 years ago, this large loop of nebulosity spans some 100 lightyears across and is located approximately 1,470 lightyears away (an update over older estimates which placed it at least 2,500 light years away).

You need about a 4 degree field of view to capture the entire extent of this object, such as the one shown here captured with a 200mm focal length telephoto lens (Canon 200mm f/2.8) on a QSI 683 camera (8300 based chip). This was imaged with 3nm narrowband filters and then colorized using the popular Hubble Palette mapping colors to the individual narrowband wavelengths (green to hydrogen, red to sulphur, and blue to oxygen).

On the far right hand side of this image is the Western Veil Nebula (NGC 6960), often just called the Veil Nebula. My favorite unofficial moniker is the Witches Broom. It is especially striking when imaged with not just RGB filters, but also supplemented with some Ha and OIII data, such as the one shown here. (Esprit 80 Refractor, Starlight XPress Trius 694, Baader filters). The bright star riding the broomstick is the star 52 Cygni, which is a bit closer than the nebula (only 291 light years), and is just in the line of sight of the edge of this feature.

The Western Veil, or the Witches Boom.

Backing out from the Witches Boom, we see Pickering’s Triangle (NGC 6967) up near the northern end of the loop. To me, this looks like a river delta on the Mississippi, or Nile river perhaps.

Pickering’s Triangle or Fleming’s Wisp

High resolution images of this area reveal a complex cosmic web of smokey tendrils. Not only is the area bright in RGB broadband light, but it’s also brilliant in Hydrogen Alpha, and OIII.  In fact, the OIII emissions of the entire super nova remnant here is among the brightest of many emission objects you can shoot.

The object is named for a director of the Harvard Observatory, but it was actually discovered by a female astronomer who was once his maid (you can’t make this stuff up),Williamina Fleming. Fleming’s Triangular Wisp is another popular, but also unofficial name for this feature.

The Eastern Veil nebula (NGC 6992) is also an amazing object in and of itself. Presented here in monochrome shot with a narrowband filter that captures light from glowing Hydrogen gas (Officina Stellare, RH-200, Starlight Xpress 694 camera).

Eastern Veil

Sometimes called Cirrus Nebula East, or the Spider, or Bat nebula, it is a worthy member of the Veil complex. The wispy filaments of glowing gas are simply etherial. It should be pointed out that in addition to photography, an OIII visual filter renders most of the Veil complex quite well with a glowing ghostly quality that is breathtaking. I’ve seen it in scopes as small as 6″ and it even very closely resembles the images shown here.

Cygnus is one of my favorite regions of the sky, especially for narrowband backyard imaging. The Veil complex has treasures for all focal lengths and chip sizes too, and if you don’t have narrowband capabilities, it is bright enough to shoot well even with a one shot color camera using a light pollution filter. Go get some of it before it’s gone!

Clear Skies!

 

 

 

 

 

 

 

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Astrophotography Highlight – June 2018

Messier 13 – The Hercules Globular Cluster

The summer is not just galaxy season, it’s also globular cluster season! Most globular clusters are located in the halo of the Milky Way and while a few can be found amongst the dense star fields of the Milky Way, most are well separated visually from our galactic arms. My favorite globular cluster is M 13 in the constellation Hercules. At the beginning of June, you can find M13 already getting high in the east, just north of due east, right along the edge of Hercules’s quadrangle.

M 13 is well placed just after dark.

M13 holds a special place in my heart as it was my first “deep sky” object that I ever had to find by star hopping with with my trusty red “Christmas Trash Scope” many decades ago now. Later, as my telescope collection grew in both quality and quantity M13 has been my benchmark target to judge the quality of my gear, both visually, and photographically.

Visually, M13 looks like crushed diamond with sparkling stars all throughout. It is bright, and the longer you expose, the larger it will appear, however you must take care not to over expose the core, else you will loose the ability to show the individual stars all the way in. Further more, the stars of M13 have colors! If you avoid over exposing, you can bring out the blue and amber star colors, which gives your image more character. All of my earliest attempts at imaging M13 showed a solid white snowball which matched my visual experiences and so I didn’t know any better. Look for those colors; they are there!

At 2000mm focal length, the great globular in Hercules is a magnificent target.

The Hercules globular passes directly overhead for most of us in North America and is an excellent backyard target, as houses or the neighbor’s trees rarely obstruct it when it is highest and at it’s best. Furthermore, it is bright enough to stand up to imaging even in light polluted areas. The image above here was taken just outside Orlando Florida, and with a quarter moon in the sky! Just take lots of exposures to stack down the shot noise from your sky glow.

As a good-sized target, M13 looks great for a wide range of fields of view. A wider field image of at least a degree will reveal two bonus objects. NGC 6207, a 12th magnitude galaxy just 28 arc minutes to the north east is often captured in wider views and with sufficient aperture can be spotted visually. A real prize is to capture the very tiny galaxy IC 4617, a 15th magnitude blip of a galaxy this is only an arcminute across.

Don’t miss a couple of small galactic interlopers when shooting M13.

There is no better target I think to demonstrate an optics resolving power than a globular cluster, both visually and photographically. The view through the eyepiece can never be matched by a computer display (with today’s technology), but a fine optic and camera combination can come close to revealing that powdery essence of M13, plus bring out the colorful stars throughout it’s core and halo.

Clear skies!

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Shoot for the Moon!

For the April 2018 Astrophotography Highlight I’m going to go for some low hanging fruit and talk about shooting the moon!  If I had a dollar for every time I’ve heard a fellow astrophotographer lament that the moon was up… well, I could probably buy the moon! The moon was my first love and is to me one of the most amazing targets in the sky that you can shoot; it is also the easiest. No matter what kind of camera, optics, or mount… and this includes TRIPODS, you can get great images of the moon you can be proud of!

The moon doesn’t know any seasons, it’s available all year long!

The moon was the gateway drug that got me started in astrophotography as a whole taking photographs of the moon through my telescope as if it were nothing but a very long telephoto lens. It is a great (possibly the best) way to get started in astrophotography because you can get results you will be happy with your very first night out. The moon is available all year long, it shines through the worst light pollution any city can muster, and it’s a fascinating world that changes nightly! You can even with some success photograph the moon through very thin clouds or haze.

Plato’s hook shown here as a jagged shadow inside the lower lip of the crater Plato is not visible every month.

You could spend a lifetime exploring the moon (photographically or visually). Once I watched the same crater for several hours one night, and you could see the changes over the course of as little as an hour. Because of libration (the monthly “swivel” of the Moon) you’ll see different features along the limb each month, and even features not near the limb (edges) can cast different shadows that can only be seen every few months.

There are many great ways to get started in lunar imaging. Let’s go quickly over a few of them.

Use a Cell Phone
The most common way people take photographs today is with their cell phone cameras, and just about everybody has one. You can literally hold your cellphone up to a telescopes eyepiece and take a photo. It takes some practice, but I’ve seen teenagers do it on their very first try at outreach events. One trick is to rest the phone on the eyepiece cup to keep it flat and steady. You’ll find quickly that moving to the left actually moves the image to the right, etc. but after a few minutes you’ll get the hang of it. Often when there is a group of people, it becomes almost a game to see who can get the better shot. There are also many brackets on the market designed to hold your cell phone steady so you can take a photo directly.

Using a cellphone on a telescope. This bracket is made by iOptron.

DSLR or Point and Shoot
The most economical entry point for any serious photographer is the so-called “Point and shoot” camera with a fixed lens system (the front lens cannot be removed and is not interchangeable). Put this camera on a tripod, and with an optical zoom, you will easily get full images of the Moon showing craters, Maria, and ray systems in great detail. You can also try holding this in front of an eyepiece, or purchase some commercially made brackets that will hold your camera in front of the eyepiece for you. The same applies to a DSLR with a long lens, except this is more difficult to mount in front of an eyepiece. I’ve shot many lunar eclipses this way, and you can make interesting nightscape images by framing up a large moon with some distant landmark.

It’s quite easy to mount a DSLR on a telescope.

DSLR on a Telescope
You can also find very inexpensive adapters that will mount your DSLR directly to a telescope. The lens comes off the camera, and the adapter connects to your camera just like a lens would, but then slides into your telescopes draw tube. Essentially, the telescope becomes a large telephoto lens.

If you don’t have a remote release cable, turn on mirror lock, and set an exposure delay. Typically I will set the camera for a 10 second delay with mirror lock enabled. Then when I fire the camera, the mirror comes up, and there is a delay before the image is taken. This delay gives everything a few seconds to stop shaking/vibrating and you’ll get steadier images. If your camera does not have mirror lock, you can achieve much the same thing by using live view. Live view however tends to warm up the imaging sensor, introducing more thermal noise so I tend to stick to the previous technique.

CCD image of the moon taken through an SII narrowband filter.

CCD Cameras
Yes, you can shoot the moon with a CCD camera too, although now you need a computer to control the camera! Some CCD’s are so sensitive compared to a DSLR that you can’t get a good image without over saturating. Sometimes this is due to the fact that the shutters on these cameras were designed for long exposure purposes and you simply cannot get the exposure short enough. There are two solutions to this; the first is simply to stop down the aperture of your telescope with a mask at the front. The second is my favorite… use a red or narrowband filter! A red filter (if you have a monochrome camera with filters) will reduce the light considerably, and might improve sharpness of your monochrome image because the red wavelengths are less affected by seeing conditions than the blue and green. If you have a hydrogen alpha, or sulfur filter, use those! They cut down on the light even more, and also have that advantage of helping to mitigate the seeing due to their long wavelengths.

So called “lucky imaging” techniques make use of video cameras to capture fleeting moments of stability in the atmosphere.

Video Cameras
A live view of the moon is also a compelling outreach tool. You don’t even have to be scope side to slew around the surface and show off the moon to a room full of people. Video captured at long focal lengths can also be processed to create stunning high-resolution images using a technique call “lucky imaging”. This is perhaps extreme lunar photography in that it does require a good bit of work using special software to pick out just the sharp frames from the video file and combine them. Never-the-less, it’s still a lot less work to process than the typical deep sky photo!

Any of these methods are within reach of even the most inexperienced beginning astrophotographer. It’s also a great way to get your feet wet processing images just by tweaking levels, curves, and sharpness. I’ll talk about each of these different approaches to lunar photography in turn in future blogs here, or in my Sky & Telescope blog on imaging foundations.

Clear skies!

 

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Astrophotography Highlight – March 2018

Messier Poster

My rather sparse attempt at bagging all the Messier objects!

March brings the beginning of Spring for us in the Northern Hemisphere (at exactly 12:15 p.m. Eastern on March 20th if you must know). March is also Messier Season! With careful planning, you can observe all 110 Messier objects in a single evening, and many clubs and organizations will host marathons the weekend of new moon this month (March 17th). Here is a good link for info about this. There is even “An App for That!” on Apples App Store! (I could not find a corresponding Android app, sorry).

Charles Messier’s list of objects was at first intended to be a carefully cataloged list of bright objects that he did not want anyone to accidentally misidentify as a comet (searching for comets being all the rage in those heady days). A good many showcase nebula, galaxies, and globular clusters have made this list and I can see how these could easily be seen as smudges and thought to perhaps be a comet. However, even given the state of telescopes in the 1700’s, it’s hard to believe some of these open clusters could be mistaken for a comet! Most likely, they just made the list because they were interesting and noteworthy.

Messier 13, one of my favorite objects in the eyepiece or with the camera!

How great it must have been to live in a time where with a telescope and eyepiece, you could identify an interesting group of stars, add them to your own catalog, and actually be one of the first people to see them! Today, we take this for granted and just type in M13 into our GOTO telescopes to slew on over to the Hercules globular cluster, a gorgeous jewel of the night sky and my favorite globular.

I’ve started my own poster project (shown above) with the goal of eventually getting a high quality image of each of the Messier objects. As you can see, it’s rather sparse at this point. Some of the images are hours of exposure time and my intent is to have a complete collection of high quality images of the entire catalog. This is still a long term goal, but I have another one for this month.

Photographing all 110 objects in a single night has been attempted and successfully completed by a few very careful astrophotographers. A good resource with a list of objects in the order that they can be observed/photographed is listed here. An all night Messier

M44

The Beehive cluster (M44). Interesting, pretty… but a fuzzy comet?

imaging marathon has long been on my bucket list, but so far, I have not had a clear night at an opportune time to attempt it! I plan to try again this year using the list above as the main basis of the order of objects in which to progress through the evening. Ideally, you will want to use some sort of automation package unless you want to watch… which I actually think is kind of fun. I’ll make some tweaks to Don Machholz’s list linked above as it seems M31 and friends are the lowest to the horizon at twilight and I want to grab them first before they get any lower.

So, a new poster project would be a collection of all 110 Messier objects taken in a single night! A photographic Messier Marathon if you will. For an all night photographic messier marathon we have no such luxury as long multi hour exposures, and in some cases there is only going to be a few minutes that you can spend on any given object. For this reason I plan to use a one shot color camera. I will be the first to tell you that you’ll get better data if

ShrinkMe

Shrinking even the noisiest images improves them!

you shoot monochrome, and a single short exposure through red, green, and blue filters will give you less noise than a single color exposure of their combined lengths (good topic for a future blog!). Never-the-less… tradeoffs! A filter wheel is one more moving part that can fail in the night, and shooting 110 objects in a single night is going to be challenge enough! Further, there are workflow issues. In my (hopeful) chart/poster, the images are not going to be very large. One of my favorite astrophotography tips is that making images smaller always improves them! So, small images will be very forgiving of noise, and images with all three color channels already aligned are going to be MUCH easier to process… times 110! I’m estimating that the tradeoff I’m making will be fine given these considerations. Next year I may change my mind on this… as they used to say in the aerospace industry, a single test is worth a thousand expert opinions!

The size of the various objects in this catalog vary from the very small Ring Nebula (M57), which is hardly 3 arc minutes across, to the enormous Andromeda Galaxy (M31) which can stretch 6 full moons width across at about 3 degrees! An issue to come to grips with in planning this is what focal length and camera chip do you use? You don’t want the smaller objects to be tiny blips in the middle of a large field, and in order to do this you are going to have to select a field of view that compromises the rather large Andromeda galaxy. Bear in mind too that many times you will be able to capture more than one of these targets in a single field of view!

M45 Barely fits!

My recommendation is about 600mm focal length and a mid-sized chip, such as an 8300 or APS-C sized DSLR or larger if you have it. My best cooled color chip is a Sony 694 in a Starlight Xpress Trius body. Very low noise and cooled. I do wish it was slightly larger, but I think it will do fine for most targets. M31 will be cropped, and if I’m careful with placement I can still fit the next largest Messier object, M45 (the Pleiades) into the field of view. My exact field of view is shown here, with my Esprit 100 refractor having a focal length of 550mm. F/5.5 is reasonably fast too and again that is going to help with the fact that I’m only going to have a few minutes on each target.

Another idea is of course to team up with someone, with one person shooting long focal length targets, and another shooting wider field. Teams are fine and all, but of course there’s nothing like being that one marathon runner crossing the finish line. Good luck this month runners!

Richard

 

 

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