A Newbie’s Adventure in Astrophotography: Part 4

April 6th, 2011

Imaging with a wedge requires a bit more effort during setup, but you can only do so much in Alt-az.  Rather then just dropping the scope into the tripod, and locking it down, the wedge holds the scope at an angle facing Polaris.  This is called polar aligning, and it is something that doesn’t have to be done with an Alt-az telescope.  It is one of the reasons that Alt-az mounts are a good idea for beginners.  Equatorially mounted telescopes have to be aligned on Polaris before you can do any observing or photography.  Alt-az can be aligned on any star or stars.  What Polar aligning does is allows the telescope to track the stars on only one axis.  A poorly polar aligned scope or Alt-az will begin to show rotation in the corners of a long exposure image.  While this may not bother a beginner, as you progress, field rotation as it’s called, becomes the enemy.  What this means, is you spend more time setting up and making sure you’ve got perfect alignment before attempting to image.   The wedge added 20-30 minutes to my setup routine.  It also makes it tough to do a full daytime setup.  I still have to wait to see a star before aligning my telescope.

M27 - The Dumbell Nebula

Since I purchased my telescope, Celestron has offered a firmware update that allows me to polar align on any star, not only Polaris.  This feature is called All-Star alignment and it is great!  This means I can get a head start on my alignment, and can align on any of the bright stars, not just Polaris.

Imaging on a wedge improved my images to the point where I could get 1 minute exposures without trailing.  That was all well and good, but I was only a single, but expensive upgrade away from having a full auto-guiding setup.  I purchased a new refractor telescope as well as rings and a counterweight system.  I also purchased an Orion Starshoot Autoguider.  An auto-guider locks on a single star and guides the mount as it tracks the sky.  It smooths out any bumps in the mount and allows you to image for very long periods of time.  I’ve currently pushed it up to 10 minutes before it shows any trailing.  This does require perfect polar alignment, but it also improves your images considerably.  I’ve posted some of my most recent images with my newest fully guided setup.

leo-trio-labeled

Coming off a spending binge on astrophotography, I now have a serious imaging rig.  While some may not quite look at a fork mounted telescope as a perfect imaging setup, it is stable, has good optics and outperforms many GEM style mounts.    At this point, my photographs are only limited by the darkness of my skies, and the effort I’m willing to put into them.  In future posts, I’ll go into some of my techniques and tips.


A Newbie’s Adventure in Astrophotography: Part 3

November 29th, 2010

So I’ve successfully taken my first Moon photograph, and was looking to go deeper.  At the time, Saturn was high in the sky and I decided to try to photograph it.  I took a few exposures and also learned something.  You can get a much better view of Saturn through the eyepiece.  As it turns out, my DSLR wasn’t the optimal camera to use to photograph planets.  Since then, an number of hardware and software advances make it more possible, but at the time, I chose to move on.

Photographing deep sky objects is nothing like Moon or even planet photography.  Deep sky photography utilizes multiple long exposure photographs.  That is while the mount continues to track a target, the camera opens the shutter and holds it open for a specified duration.  That means a lot is going on while imaging, of course the mount and camera do most of the work.  This fact will allow you to automate the most tedious aspect of the process, so most of the effort goes into the setup.

The first thing you have to do is get the camera focused.  If the Moon is up, you can focus on that.  The same with a bright planet like Jupiter or Saturn.  But your next best option is a bright star.  My camera, the  Canon XS, has live view.  Live view allows you use either the LCD screen on the camera or a laptop computer as the viewfinder.  With live view, you can zoom in on a bright star and turn the focus knob until the star appears to be a pinpoint.  This allows you to get very close to perfect focus.  That said, only the 10 or so brightest stars will be visible on the screen, so don’t expect to see what you would see through the eyepiece.  When it comes to Live view, it is a focus aid and no more in regards to deep sky photography.

A Bahtinov Mask is a handy tool for achieving perfect focus.  My focusing routine went from being a 20 minute affair to less then a minute.  It also gave  me better focus which resulted in more attractive stars.  You can download a template to make your own Bahtinov mask or purchase it at Focus-Mask.com.

My first Deep Sky photograph was of M3 a globular cluster(top right).  Globular clusters are the best targets for newbies.  They are bright, Looking back, my results weren’t terrible, but they weren’t anything to write home about.  Needless to say, I was ecstatic about my results, and was hooked.

I considered myself lucky the first few days I had the telescope.  The weather held out, and I got to use it before the clouds rolled in a couple of days later.  This is another aspect of the hobby that can sometimes be frustrating.  For visual observing, partly cloudy skies can still provide for an eventful outing.  For astrophotography, clouds are a no go.  So I found myself checking the weather and hoping for clear nights.  These days I use the Clear Sky Clock on the top of the page, and it has proven very reliably and handy.

The Telescope I use, a Celestron CPC-800 is on an Alt-Az mount.  What this means is that the telescope tracks the sky on two axis.  This is unlike an equatorial-mounted telescope which tracks the sky on a single axis revolving around the star Polaris.  For deep sky astrophotography,  an equatorial mount is optimal.  That is not to say you cannot get nice images photographing in Alt-Az, but an equatorially aligned mount will allow you to take longer exposure photographs.  The limit in Alt-Az would be around 30 seconds otherwise, images show field rotation.  This is the biggest limitation of Alt-Az mounts when it comes to astrophotography, but there is a simple solution.  An equatorial wedge allows you to equatorially align an Alt-Az fork mounted telescope like the CPC.

I purchased the Celestron HD Wedge.  Now I could push my exposures a bit further.  In Alt-Az, I was getting 20-30s exposures.  At this point, I am able to go 45s without showing any trailing stars.  My pictures are improving, but I know I still have a way to go before I’m going to be framing them.

A Newbie’s Adventure in Astrophotography: Part 2

November 12th, 2010

One of the first things you realize when doing astronomical observing is that the objects you are looking at don’t look like the photographs. You rarely see color, mostly just faint fuzzies.  But by using long exposure photographs you can bring out more details then you could hope to see with even the best telescope.   While the faint fuzzies are impressive, I found that I wanted to see more detail.  So I began my hunt for a camera.

Which camera to chose?

There are two basic types of cameras used for astrophotography, DSLR and CCD. Each type of camera has it’s own benefits and drawbacks, but I chose the DSLR for a few reasons. First, I liked the fact that I could use a DSLR for daytime photography. I’ve always been frustrated with point and shoots, and this became my opportunity to step up. At the time, I also liked the fact that I didn’t have to bring my laptopThe Moon out into the field with the DSLR. CCD’s require a dedicated laptop computer. As it turned out, I prefer using my DSLR in conjunction with my laptop, anyways. It makes focusing, framing and reviewing a lot easier. It also means that I can review my photo’s while shooting without disturbing the current shot. As well, DSLR’s are much more affordable then CCD’s.

The DSLR I chose was the Canon XS. At the time, it was Canon’s entry level DSLR and it came with features that help during an astrophotography session. Live view, for example, allows you to see and zoom in on whats in the viewfinder from the camera’s LCD or from your computer. It also allows you to set up a series of timed exposures(while hooked up to a computer), which previously required a separate timer hooked up to the camera. All in all, the Canon XS makes a very good imaging camera for astronomy.

Next, I had to attach it to the scope. I purchased a Celestron T-Ring and T-adapter. A T-Ring is specific to the camera model as it threads onto a DSLR just as the lens would. The T-adapter threads into the T-Ring as well as the telescope. Once all of the pieces are attached, the camera is hooked up to the scope. From here, I had to find a way to focus. Fortunately for me, there was a partial moon out, and I was able to use the moon for focus. At this point, I had already brought my laptop computer outside and hooked it up to the scope. Now, rather then looking at the moon through the eyepiece of the scope, I just sat down at my camping chair and observed the moon on my computer screen. I could also zoom in on any point in the image just by clicking.

So I snapped my first astroimage.  Then I adjusted the exposure and took another image.  My results are above.

Moon photography is the easiest type of astrophotography.  It is a big bright target, and doesn’t require much image processing.  A single short exposure photograph can be amazing.   This differs from planets, which tend to be smaller and require multiple short exposures, and stacking or combining of exposures to add detail.  Deep sky photography is the most advanced and requires precise tracking of the target and long exposure photographs.  In future articles, I’ll be concentrating on my introduction to deep sky photography.

Continued in Part 3…

A Newbie’s Adventure in Astrophotography by Adam Jaffe

November 2nd, 2010

This is the first of a series on my experiences in astrophotography and astronomy in general over the last two years.  I came into the hobby with little to no knowledge of astronomy or photography, so I was really dependent on the information available online.  I’m not saying I took the best route, but I’m at the point where I’m happy with my equipment and happy with my results.  Some of the first posts may just be a diary of my trials and tribulations, but later I hope to share some of what I’ve learned in a more instructional format.  But for now, just enjoy…

Part 1

I’ve always been interested in astronomy.  Looking up at the sky has always stimulated so many profound questions in my mind.  How big is the universe?  Where did it all come from?  Is life on Earth an anomaly?  Whenever an astronomy article came up on one of my regular websites, I’d read it.  I had made a habit of checking the Astronomy Picture of the Day.  I wouldn’t miss any Discovery Channel specials on space.  But, I realized,  there is only so much you can experience from second hand sources and I decided to take the next step.

I decided to buy a telescope.  I did some research and noticed that many of the Astronomy pictures I’ve been drooling over were taken by amateurs.  I had always assumed that without a NASA budget, photographs of galaxies would be out of reach.  Once I realized I had been wrong, my excitement grew.  I joined the Cloudy Nights forum, and asked for some advice.  I wasn’t prepared for how helpful the forum could be and I quickly had a telescope picked out and I ordered a Celestron CPC-800.

The telescope showed up the next day, and having read and re-read the manual off of Celestron’s website I began setting it up immediately.  I had absolutely no problems getting it set up and began my alignment.  As per the instructions, I picked three bright objects, centered them, and hit the align button.  My last alignment object was Saturn(for future reference, don’t align on planets).  As it came into the field of view, I was flabbergasted.  I could see the rings clear as day, and even some color detail.  I immediately sprinted towards my house to get my wife, but stopped and realized I forgot to hit the final align button.  I went back, completed the align and then proceeded to run into the house screaming for my wife.

Both my wife and I spent the next few nights out observing.  Saturn was the only planet in view,  but we also got a chance to look at M51 and a few other deep sky objects.  The other Cloudy Nights members did a good job of tempering my expectations, and I was very pleased when I saw the little wisps of The Whirlpool Galaxy and it’s companion galaxy.

We did get lucky, the rain that typically accompanies a new telescope purchase, held out for three days.  So we got three nights of observing before we were relegated back inside.  With only clouds and rain to look forward to, I decided to listen to the voice in the back of my head and begin searching for a camera.

Continued in Part 2…