Date: February 2, 2010

Title: Amateur Astronomy’s Affliction – Aperture Fever

Podcaster: RapidEye

Organization: RapidEye Observatory – a private observatory in rural Lee County, NC http://www.rapideye.us/astro/RapidEye-ClearSky.html

Description: An analysis and examples of the dark side of Amateur Astronomy.

Bio: I’ve been captivated by astronomy ever since I was a kid, living in NW Colorado where the Milky Way was bright enough to read by. I can be found most clear nights in my pasture with either my 4.5″ Dob, 10″ Dob, or my binoculars.

Today’s sponsors: This episode of “365 Days of Astronomy” is sponsored by Greg and Heather Thorwald on behalf of our favorite monthly astronomy lecture, “60 Minutes in Space” at the Denver Museum of Nature and Science, learn more at dmns.org.

Also sponsored by Kylie Sturgess of the Token Skeptic podcast, investigating superstitions and the science behind them at www.tokenskeptic.org.

Transcript:

Script for 365 Days of Astronomy – February 2, 2010

Amateur Astronomy’s Affliction – Aperture Fever


People become involved in hobbies for many different reasons.  My brother loves to fish because of the peace and quite he finds while out on a mountain lake or stream.  My father on the other hand loves golf because of that different challenge every course, every hole, and even every shot presents – no two days on the course are the same.  My Mother-In-Law is a very accomplished quilter and will disappear for hours into the patterns and rhythms of the work while time seems to pass by her unnoticed.  As a hobby, astronomy is no different.  I enjoy the relaxing peace and quiet while sitting in a lawn chair on a warm night while scanning the summer Milky Way with a pair of binoculars.  I get an amazing feeling of accomplishment after completing a challenging observing program by star hopping across the sky locating faint, fuzzy objects using nothing more than a sky atlas and a red flashlight to hunt from one object to the next – each starhop presenting a unique and frequently a memorable challenge.  There is also an almost magnetic pull that some objects have, drawing me deeper and deeper into the eyepiece while my eye traces faint swirls, eddies, and finds patterns in nebula, clusters, galaxies, comets, or planets all the while time just seems to flow by without notice.



What is often overlooked, or if it is noticed, discussed in hushed circles, is the downside each of these hobbies has.  Fishermen will spend hundreds of dollars to buy the latest and greatest tackle to help ensure they catch their prey and tens of thousands of dollars on boats and fuel to get them out to where that bigger, smarter, more elusive trophy fish lives.  Golfers will spend many hundreds of dollars on a new club or some other gadget to help them eek out another 5 yards on a drive.  Quilters will spend thousands of dollars on sewing desks and machines to help them complete that next quilt that is just a few feet bigger.  Astronomy is no different, it has its own dirty little secret: Aperture Fever.  Telescopes can be measured many different ways.  Cheap telescopes in department stores try to lure in beginners with promises of high magnifications like 700X!!!  But seasoned astronomy veterans know that the most important measurement of any telescope is the diameter of its primary reflective or refractive component.  So if we are trying to see thing that are, as George Hrab so eloquently puts it, Like Ubber Far away, why isn’t it important how much a telescope magnifies?  The reason a telescope’s most important measurement is its diameter is because a larger primary will collect more light, have a higher resolution, and has a much higher coolness factor.


Lets start with first symptom of aperture fever – the pursuit to see fainter and fainter objects.  Most amateur visual astronomers with a 4, 6 or even 8 inch telescope will observe the Messier list, some of the brighter NGC objects highlighted by the RASC, SAC, or Caldwell lists.  These several hundred beautiful and engaging objects can keep an astronomer happy for years observing them over and over seeing what new details can be teased out from a darker location, a new filter, or a new eye piece.  But eventually the call of the faint fuzzies starts to get louder and become harder to ignore. On an exceptionally clear night while observing the Cigar Galaxy (M82) and Bode’s Galaxy (M81) in Ursa Major with your 6 in telescope, you might notice another small smudge just to the south.  As the seeing comes and goes, the object pops in and out of view.  Using averted vision you can get the object to stay in view but can’t see any details.  You turn to your nearby friend with the 10″ scope and ask him if you can borrow his scope for a couple of minutes.  Sure enough, right there, just where you thought it was, another small galaxy!  You double check your charts, and yes, you have just “discovered” NGC3077!  Because light collecting is a function of surface area, not diameter, that 10″ telescope isn’t just 2/3rd bigger than the 6″ telescope, it collects almost 3 times as much light!   You try that 10″ scope on another small scope favorite, M13, a gigantic and bright globular cluster in Hercules.  Sure enough, not only is the cluster brighter and more resolved, but just to the north of the cluster is a small strip of light that is invisible in your 6″ – you’ve just found NGC6207, a small galaxy that lies tens of millions of light years beyond the cluster.  Don’t even point that bigger telescope towards the no mans land between Virgo, Leo, and Coma Berenices or your friend won’t get their 10″ scope back anytime soon!  Once you start down the path of hunting down fainter and fainter objects there is only one real end point – a bigger telescope.

The second symptom of aperture fever is a little less obvious, but not less important – pursuit of increased resolution.  Lets go back to that 6 inch telescope.  The amount of detail visible on the moon, Jupiter, Saturn and Mars will be amazing.  Under steady skies you’ll see countless craters on the moon, Jupter’s Great Red Spot, the Cassini division in Saturn’s rings, and all the major albedo features on Mars.  I don’t have time here to get into the physics involved, but increasing the aperture of telescope also increases the telescope’s ability to separate objects that are close together.  What this means to an astronomer is the ability to separate a small blob in Jupiter’s atmosphere into two separate and smaller oval swirls.  Or turn what looks like a funny broken line on the face of the moon into a chain of small craters.  The amount of detail that increases is subtle and doesn’t jump out at you like the increase in object brightness does.  Even deep sky objects benefit from this increased resolution.  Globular clusters that are puffy balls in the 6 inch scope explode into a sea of individual points of light in a 10 inch or 12 inch telescope.  Even galaxies that are millions of light years away reveal more detail – spiral arms will become sharper and more pronounced and dust lanes that pepper many galaxies become obvious in the bigger telescope.  Just like the pursuit of faint fuzzies, once you see the increased level of detail a larger aperture gives, there is only one real cure – a bigger telescope.

The final symptom of aperture fever is probably the most insidious, the most obvious, and yet, the symptom most amateurs secretly pride themselves on – the coolness factor!  Go to a club dark sky site or star party and see for yourself.  A new 80mm carbon fiber apochromatic triplet refractor will no doubt turn heads and lure the occasional passer by to move in for a closer look.  A new 127mm Televue IS Imaging telescope will pull in a handful more people.  But the guy with an 8 inch refractor on an Astrophysics 3600GTO mount will have to put up safety cones and tensile barriers to keep the crowds back.  You should see the crowds follow a SUV pulling a cargo trailer with an 30″ Obsession Telescope sticker on the side of it, waiting for it to stop so they can help unload and set up the scope in the hopes of being one of the first to look through the telescope that night.  The bigger the telescope, the longer the line will be to look through it at night – its the second law of Star Parties, right after red lights only!  Everyone at a star party wants to be the guy or gal with the longest line – it becomes a matter of club bragging rights.  Just look around the office or cubicle of any large telescope owner – there is likely to be more pictures of their telescope than the is of their children.  Anyone can have kids, but not everyone can own a 24″ F/3.3 Starmaster, or so the addiction, err, I mean theory goes.

Unfortunately the price of telescopes increases exponentially with the size: an 8 inch refractor costs considerably more than twice that of a 4 inch refractor.  So most folks satiate their aperture fever need with a modest jump in size – say going from a 4 inch to a 6 inch refractor or going from an 8 inch reflector to a 12 inch reflector.  Both jumps will give noticeable increases in brightness, resolution at the eyepiece, and modest increases in stature at the club dark sky site.  But like any addiction, the satisfaction you receive from your new and larger telescope eventually starts to fade and someone shows up to the club field with a newer and bigger telescope that shows just a couple more small faint fuzzie dots in that Hickson Galaxy cluster or shows hints of Olympus Mons on Mars on those few seconds when seeing firms up.  Does it sound like I know just a little bit too much about this affliction?  Yes, its true, I know this addiction first hand. 

After 5 years of touring the heavens with my trusty 10″ F/5 Hardin Dob, I managed to cool my aperture thirst by purchasing an 18 inch F/4.5 Obsession.  This scope has shown me details on Jupiter and Mars I’ve only seen in magazine pictures.  I’ve witness first hand how Globular Cluster Messier 15 explodes into a sea of stars, all the way to the core.  I’ve even had a chance to pick out individual members of Stephan’s Quintet – something I tried in vain to do with my “little” 10″ scope that really didn’t look that little when I first put it next to my 4.5″ F/9 Orion Dob.  Yes, I have to admit, this recent purchase isn’t the first time aperture fever has made me open up the checkbook and make my wife weep.  I’m sure there is a reason she hid the Spring 2010 Orion Telescope catalog from me.  That is OK, I only have to wait until the next Star Party to see what monstrosity they have thought up to liberate unwitting aperture addicts from their child’s college funds. 

This podcast is dedicated to a great scientist, an active amateur astronomer, and a dear friend, Dr Gene Baraff.  His positive impact, helpful manner, and friendly advice on countless amateur astronomy forums will be felt long after his passing.  Goodbye Doctor Wizard – you made a difference you will be missed.

End of podcast:

365 Days of Astronomy
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