ToddSpace: John's Astrophotography Page

Interacting galaxies in Canes Venatici

Took this photo on Thursday, April 20th of the grand spiral galaxy M51 along with its companion, NGC5195.  These galaxies are technically located in the constellation Canes Venatici (Latin for 'hunting dogs'), but for all intents and purposes, they are just slightly to the south of the first star in the big dippers handle (Alkaid).  This is not an easy target to pick out in either binoculars or small telescopes, the best you can hope for is to detect a fuzzy blob in that general vicinity, under exceptionally dark steady skies you can possibly pick up more detail.  In my old 12" scope (aperature) I was able to see some of the spiral arms.  However, long exposure photography reveals an entirely different wonder.  This photo is a composite of 7 10 minute exposures with my canon 350d (digital rebel) and my Takahashi E-160, click on the photo for the big picture.

Note in this photo the larger spiral galaxy (M51, Messier object 51) and its companion galaxy NGC5195 (National Galactic Catalogue 5195).  You can see the outer arms of M51 being tidally torn apart by this galactic flyby.  This pair of galaxies is 37 million light years distant (meaning what we see today is what the galaxies looked like 37 million years ago). 

Comet Schwassmann-Wachmann 3 in May '06

Comet Schwassmann - Wachmann 3 (comet SW3) will be passing close to earth during mid-May this year, want to photograph it?  Believe it or not, you don't need any fancy equipment, the simplest of setups is a camera on a tripod with a lens of your choosing.  The longer the focal length the better chance you have of picking up more detail in the tail, but even a 50mm lens should show the comet.  With that said, this is one of the simplest and most rewarding solar system objects to photograph.  Typically, a 30 second exposure is enough to show a reasonably bright comet.  To read about comet SW3 go to sky and telescope's page http://skyandtelescope.com/observing/objects/comets/article_1704_1.asp

You can photograph a comet through a telescope, a 50mm lens, a 200mm lens, whatever, if you have a digital camera that's capable of taking 30 second exposures, then put your camera on a tripod, point it at the comet in Mid-May and shoot.  Here's a 30 second exposure I took of Comet Ikeya-Zhang in April '02 with a film camera and a 600mm lens.

  I can't remember if I took this photo on a tripod or mounted piggyback, but the point is, even if you get some rotation of the stars, it's not going to be all that bad in a 30 second exposure.  OK, so read the article, learn where the comet will be in Mid May, and get some good photos so I can display them here!

Here's a photo of the same comet taken with a 200mm lens (cropped to the comet):

The trio in Leo

From time to time I'll post some of my new photos without much regard for the learning aspect, here's my first time doing this.  Last night, on the evening of April 19th I was able to get out under clear skies and photograph a dazzling trio of galaxies in the constellation Leo.  If you look directly overhead on March, April and May evenings here in New England shortly after nightfall, you'll see a backwards question mark, that's the head of Leo, the lion.   The constellations Leo and Virgo are home to countless galaxies, most of which are visible in small telescopes and some even in binoculars under clear dark skies.  The following photograph is a composite of 4 10 minute exposures of "the Leo Trio" consisting of M66, M65 and NGC3627 (that's the one shaped like a hamburger).  The photo was taken with a brand spankin new modified Canon 350d (aka digital rebel xt), my Takahashi E-160 and the Losmandy G-11 mount.  There's also another component to these 10 minute exposures that I take called guiding, that's done electronically with a seperate ccd called an ST-4, I'm not going to get into that right now, that'll be a seperate post when I have a little more time.   Anyway, click on the photo to see the larger version.

These three galaxies are gravitationally bound and are sometimes referred to as the "M66 group", but are part of the much larger super cluster called the Virgo cluster. 

So I have a Telescope, now what?

In this post, I'll address photography with beginner telescopes, that is, those without a right ascension driver (RA drive).  A little divergence here, what the heck is a RA drive?  First off, right ascension, if you you stand in your favorite celestial viewing area and face north (toward polaris), and turn to your right (east), then that is the direction that the celestial objects ascend into the sky, thus the term, right ascension.  Beginner telescopes typically are refractor type (objective lens in the front, eyepiece in the back) or reflector (mirror in the back, eyepiece in the front) and are stationary on a tripod, i.e. they don't have a right ascension drive.  Now that we have that out of the way, what can you photograph with your telescope?  Fortunately, depending on the magnification your telescope can achieve, lots! 

There are generally speaking two types of photography with a telescope, prime focus and eyepiece projection. 

With prime focus, you essentially take the eyepiece out and mount the camera directly to the telescope.  In the photo on the left, you can see one of my typical setups.  In this instance, I'm shooting three cameras at once, but the one of interest is the scope (refractor) on top, note the camera mounted directly to the telescope.  This is done with a readily available part called a t-mount.  It's fitted to your brand of camera, I use olympus and canon cameras, so the t-mounts I use fit the bayonet mounts of these two camera types.  T-mounts are readily available at all online telescope vendors (anacortes, adirondack video astronomy, optec, etc...) and locally at Rivers photography in Dover, NH.  Once you have the t-mount, all you need is a shutter release cable and a t-mount to focuser adapter.  Most telescopes have a 2" or 1.25" focuser, so you'll need an adapter to screw mount the t-mount to your scope, once you do this, hook up the camera to your telescope, point it at the moon, and shoot!  Here's one I took in Apr '06 of the crescent moon using this method:

  I liked this photo because the part of the moon not illuminated by the sun is still quite visible, this phenomenon is called earthshine.  If you get the proper filtration for your scope, then you can also photograph the sun.  Here in the northeast we had the pleasure of having a nice cloudless day on June 8th 2004 to view the first time in any of our lives that venus passed between the earth and the sun, using a small refractor, a nikon coolpix 4500 and a thousand oaks solar filter, I took this picture. 

This same method can be used to photograph a solar eclipse, although the last really good one here in New England was in may 1994, well before my first venture into astrophotography (although I did try photographing it with a film camera and three pairs of sunglasses for filtration, needless to say, this didn't come out).

Eyepiece projection

The other very useful technique for solar system photography is called eyepiece projection, using this method, you can either hold the camera right up to the eyepiece and shoot (and some people get some amazing results) or you can use a similiar method as described above where you buy a tele-extender and the t-mount, and you put the eypiece in the tele-extender, mount the camera to the tele-extender via t-mount, put the tele-extender in the eyepiece holder (typically called a diagonal) and shoot.  Because this is a setup prone to vibration, best to use a shutter release cable.  The advantage to this technique is that you can get much more magnification.  Using this technique, as well as a technique called averaging (where you take multiple photos and use an application such as registax to layer them together), you can get some really nice results, here are some examples of eyepiece projection:

 

Solar system objects are bright enough that they really don't require long exposures, typically about 1/16th to 1/8th of a second, but bracketing your exposures is best, especially if going with a digital camera.  One thing I haven't touched on much thus yet is focusing, it becomes challenging with dimmer objects, but with bright objects such as the moon and planets, it's not much of an issue. 

john

Bring on the Milky Way!

Some of the most dramatic astrophotos I've ever seen have been the result of the most simplistic of setups, but require some knowledge of the celestial sphere.  The milky way, we've all seen it, especially on dark moonless nights stretching from one side of the horizon to the other.  It's most pronounced in the dog days of summer, with the summer constellation, cygnus the swan riding high overhead.  Cygnus is also the home of another easily recognized asterism, the northern cross.  The cygnus region of the milky way is one of the most easily photographed and breathtaking areas of the sky, and can be done with a simple guiding system and camera capable of 5 minute exposures.  Before we go any further, he's a sampling of a photograph of cygnus taken from a dark sky with a good guidance system:

I took this photo about 4 years ago, really before I had any idea what I was doing, and was shocked to see it come out.  The idea is really simple, you have to have a telescope mount, and you need to have that mount polar aligned, this means having the optical axis of the scope pointed to the north celestial pole (which is very near polaris).  This is somewhat difficult to grasp, but if you can do this, then the rest is a breeze, literally.  Others have pontificated on this at length, so I will you point you to this web page, DarkskyImages.com.  I have referenced them repeatedly.  In general, the better your polar alignment, the long exposures you can take.  A lousy polar alignment, you can shoot for a minute or two, a good one, you can go 15+ minutes with a camera with a 50mm lens.  So how do I couple the camera to the telescope or the mount?  Take a look at this picture:

Your eyes do not deceive you, this is whats called "piggyback photography", where the camera is mounted to the telescope (or directly to the mount), in this image, I mounted it to the telescope with a homemade wooden bracket and bungee cords (hey, any port in a storm).  With this setup I was able to shoot 5 minute exposures, you can do the same.  So to recap, polar align your mount (it must have a RA drive, right ascension), mount the camera to the scope or directly to the mount, point the camera at the milky way, and shoot.  To give you an idea of what's possible after some experience, here is a digital stack (more about that in another post) of three 15 minute exposures of the southern part of our milky way.  If your ever standing at the north end of a lake in the summer time with a clear dark sky to the south, be prepared to have your breath taken away, it's one of the most amazing sights to behold, I saw it when I was 9 and will never forget it, the center of our galaxy stretching down to the horizon.  Enough of my walk down memory lane, here's the photo:

In these milky way photos, you'll see blotches of red, that's hydrogen alpha emission nebula, or more commonly known as, nebula.  Don't bother looking for them with your eyes, you won't see them as anything more than a hazy smoky blotch, why is this?  Two reasons, your eyes take snapshots of the world around you, long exposure photography collects multiple snapshots so it shows more.  Secondly, your eyes ability to pickup light falls off dramatically as the light waves approach infrared.  Hydrogen alpha emission nebula are at 656.3nm, very close to IR light, so only films and DSLRs that are sensitive to this light can record it.  The best film still in print for this purpose is E200 slide film, although there are some others.  Even if you don't care about recording hydrogen alpha, other films can record the starlight, which is a worthy photo in and of itself.

Beginners Astrophotography

So, you're looking to get into astrophotography but don't want to spend an arm and a leg (or the equivalent of a tank of gas) and just want to use the camera you have?  Well, there's three targets you should consider, the moon, star trails, and aurora.  The easiest of course is the moon, if you have a good lens, just about any size will do, and a well composed foreground, then it's pretty easy, put the camera on a tripod and bracket your exposures.  What does that mean?  To bracket your exposures mean you try lots of different exposure times, in my experience, a crescent moon with an f/4 lens requires about 1 second, a full moon with the same lens requires about 1/125th of a second.  Here's a shot I took of a setting crescent moon in the western hills of Maine with an 85mm lens:

Not much to it, sometimes you just need to find the right target.

Next up is star trails, all you need is a camera that can do long exposure photography, a lens, a tripod and a shutter cable.  Star trails are rather cool, because if done well, you can get a very good appreciation for the movement of the heavens in any given evening as well as the different star colors out there.  In order to do star trails, you will need to find a very dark location, ambient light will completely ruin a star trail shot as you will need to do very long exposures, typically at least an hour.  Oh, this goes without saying, most modern Digital SLRs are just not capable of taking hour long exposures, so go with film, 400 speed is the best for this application in my opinion.  OK, so you found a dark location, the most dramatic star trails are those that show the motion of the stars moving around the north star, aka polaris.  But John!  I have no idea where polaris is!  No problem, try this little trick, find the big dipper (if you can't find that, well... I don't think I can help you), the last two stars in the "cup" part of the dipper, if you draw a straight line that goes through the two stars then about two fist widths (held at arms length) you'll find another bright star, that's polaris.  Anyway, point the camera on a tripod with an approximately 50mm lens at f/16 or so, put the camera on bulb and hit the shutter cable, come back in about an hour, you'll be surprised at your results.  Here's a 4 hour star trail I took back in 2003:

You can see the motion of the stars around a central star (polaris) unfortunately, that darn tree blocks the view of polaris!  Anyway, you get the idea, no telescope no mount no guidance system necessary, just very dark skies and a FILM SLR that can do long exposure photography.  Make sure you stop down the lens to f/16 or so, that way you won't flood out the image with too much light.

Finally, everyone's favorite target... aurora.  I'm willing to guess that most of you who are reading this have never seen an aurora.  Count me among those until one brilliant night, sept 7th 2002, I was up in central Maine with my telescopes waiting for nightfall when it just kept getting brighter and brighter rather than darker, and lo and behold, the heavens just erupted in green and pink streamers that lasted off and on through to 2:00am the next morning, truly an evening to remember!  A little bit of a digression here, believe it or not, aurora are actually semi-predictable, please visit SpaceWeather.com for 1-2 day predictions.  Unfortunately, they're not all that accurate and also unfortunately, we're currently at the solar minimum, the bottom of the 11 year sunspot cycle.  Typically, aurora's happen as the result of solar flares, which also typically happen as the result of high sunspot activity, in other words, for 2006, we're probably not going to see many of them at mid latitudes.  However, they do happen unexpectedly on occasion.  Enough John!  How do I photograph them?  Fortunately, this is a no brainer, but you actually need to be ready... have a sight prepared, you need to have a clear view of the northern skies and it needs to be light pollution free.  If you get that, then you'll get some photos worthy of an 8x10 on your favorite wall.  They're simple enough to photograph, when an aurora erupts (once again, visit spaceweather.com frequently, also, they offer a $5/month subscription service) just put your SLR with 400 speed film, or DSLR at ISO 800 with a wide angle lens and snap off 30-60 second exposures.  Not much more to it than that!  On the night before halloween, 2003, this aurora erupted illuminating the skies of Bedford, NH on a night that nobody who viewed it will soon forget:

These two photos were both 30 second exposures with a 1970's style olympus OM-1 and 400 speed film.  Not bad for archaic technology!  Of course, the secret to great aurora photography, is being in the right place at the right time, no easy task, but spaceweather.com can help in a big way.  BTW, for you perpetually curious, the colors of an aurora are the result of what gasses are being energized (ionized, with an electron being ejected resulting in a photon, i.e. a particle of light).  Hydrogen releases red, oxygen, blue, carbon, green, I think I got that right... feel free to correct me if I got that wrong.

My Equipment

While I've gone through quite a few different telescopes over the past 5 years, I believe I've settled in on a good combination of telescope, mount, camera and guidance system.  Back in November of '05 I purchased a 30 year old Takahashi E-160 off of astromart.com (the most comprehensive used astronomy equipment sight out there).  The Tak E-160 is an extremely fast telescope at f/3.3, meaning the ratio of its optical mirror to the focal length (the length of the light path) is approximately 3.3.  In this instance, the mirror is 160mm wide and the focal length is 530mm.   In the attached photo, the E-160 is the big yellow tube.

Coupled to the telescope is an ordinary stock canon 20d DSLR (digital SLR), available at all fine photo shops for around $1200 new.  The telescope is mounted to a Losmandy g-11 mount, this is rated for scopes up to 70lbs, my scope probably weighs in around 25lbs with all the accessories mounted to it.  The mount will properly guide the scope through the celestial sphere as it rotates around us.  Have you ever watched the stars long enough to notice that they rise in the east and continue on a westward path moving about one thumbs width every two minutes?  Therein lies the most difficult problem in photographing the heavens, not just having a camera that can do long exposure photography, but also can track an exact position in the sky (for the sake of these discussions, a DSO, deep sky object) for several minutes and even hours at a time.  While a mount such as the losmandy g-11 can move the telescope in sync with a DSO moving across the sky, getting the precision necessary for long exposure photography requires one additional step, it's the one that drives us all crazy and is the one most prone to failure, that is, guiding.  In this photo, you'll see an additional blue scope mounted on top of the Tak e-160, that's called a guide scope.  There's one last component, called a ST-4 guider, that is essentially a 1990's era CCD camera that takes continuous photos through the guidescope and sends back directions to the losmandy mount on how to move the telescope to stay perfectly trained on that D SO.  Sound easy?  It's not ;-)  Astrophotography is a labor of love, and a byproduct of many sleepless nights.  However, in the end, for me it's well worth it.  I'll also post on some of the easier and equally rewarding aspects of this hobby.