Date: May 21, 2010
Title: Common Questions and Answers
Podcaster: RapidEye
Organization: RapidEye Observatory – a private observatory in rural Lee County, NC http://www.rapideye.us/astro/RapidEye-ClearSky.html
Description: Common Questions and Answers about Telescopes
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 sponsor: This episode of “365 Days of Astronomy” is sponsored by The Planetary Society, celebrating 30 years of inspiring the people of Earth to explore other worlds, understand our own, and seek life elsewhere. Explore with us at planetary.org.
Additional sponsorship for this episode of “365 Days of Astronomy” has been provided by the International Centre for Radio Astronomy Research. Discovering the hidden Universe through radio astronomy. Visit us on www.icrar.org to find out more.
Transcript:
Podcast for 365 Days of Astronomy – May 21, 2010
Common Questions and Answers
Anyone that walks into my office knows right away that I am an astronomy nut. On one wall I’ve got a NASA GALEX Poster hanging next to an Orion DeepMap 600 and on the other wall two different Astronomy calenders hanging next to eyepiece sketches done by myself and/or friends. I’ve also got pictures of several of my telescopes scattered around, with the photo of me, my daughter, and my 18″ Obsession where everyone can see it. Almost without exception, new visitors will look at that picture of the 18″ Newtonian and ask “How many X can you get with that?” Anyone that I haven’t bored to death with the “magnification discussion” with will then point to one of the more interesting galaxies on the GALEX poster or a deep sky photo on one of the calenders and ask if I can see that object with my scopes and do they really look like that? I’m certain that I’m not the only person listening to this podcast that fields these exact questions on a regular basis. In fact, I’m pretty sure almost anyone that subscribes to this podcast can answer those questions right off the top of their head. I’m hoping that with this recording, we’ll have a handy and easy reference that we can point people towards to easily answer these questions.
So what are some of the more common questions people new to telescopes ask and what are the common misconceptions they have.
Lets start with what is the most common question I am asked: “How many X or how much power does that telescope have?” I usually start off by explaining that within reason any telescope can reach any power depending on what eyepieces are used, the power isn’t really determined by the telescope by itself. I know this is technically the right answer, it usually isn’t what they are looking for. So after the awkward moment of silence passes, I append to the answer – with the proper eyepieces, the practical range for an average 8″ telescope is between 30X and 400X with the higher magnifications really hard to reach due to atmospheric turbulence. An upper limit of 250-300X is probably more realistic. The good news is that at 250X and lower, thousands of objects are easily visible in that 8″ telescope and higher powers really aren’t necessary. On evenings where the atmosphere is still, objects like Mars, Jupiter, Saturn, and the Moon will look awesome at 250X. Additionally, many showpiece objects actually look better at lower powers. The Great Orion Nebula, the Veil Nebula, and the Andromeda Galaxy often give their finest views at powers closer to 30X. So the power the scope can achieve really isn’t that important compared to other factors.
If the visitors haven’t started to glaze over or start checking their watch, I’ll try and expand the discussion a bit more: Trying to use power higher than the conditions and or telescope will allow will actually make things look worse, rather than better. This makes a good place to take a first shot at department store telescopes. I explain that the telescopes seen at the store with 700x or 800x on the side of the box are not realistic, but rather, are just using marketing hype to try and sucker people into buying a telescope that really isn’t capable of giving good views at those powers. Now most of the subscribers to this podcast know that there are many other limitations and/or issues with the typical 60mm f/10 telescope on a shaky tripod, and why it will never be useful at anything close to 700X, but I’ve found that those discussions are usually best to be had later on after they’ve gotten a little more familiar with telescopes.
So lets move to the next most common question I hear: “Does that galaxy on your picture really look like that in your telescope?” This one can be a bit tricky, depending on what picture is being displayed on the calender that month. This month, May 2010, the Scientific American Space Calender shows a Hubble picture of elliptical galaxies near the center of the Coma Galaxy Cluster. My first inclination is to say no – nothing we look at with our telescopes looks like what they do with the Hubble. But if I pause for a moment and look at the picture and try to imagine it without any colors, it actually does look pretty close to what you can see through the eyepiece of an average 8″-10″ telescope under dark skies. Sure, not of those exact galaxies – the FOV of the entire image is approximately 10 arc seconds across and distant galaxies are clearly visible in the image that are probably magnitude 20 or dimmer. But if take my 10″ f/5 dob out to the middle of my pasture, far away from big city lights and point it towards the center of the Coma, Virgo, Leo region of they sky this is pretty much what I’ll see – numerous nondescript elliptical galaxies with a handful of field stars tossed in for good measure. So while the exact galaxies in the view may not be achievable in our telescopes, there are many other galaxies that look very similar that are viewable.
So maybe the better way to phrase the response is, yes and no. Using average sized telescopes, most galaxies, clusters, and nebula are colorless or if they do have any color, its very subtle. But an experienced observer will be able to see the shapes and structures of many objects, although not to the same level of detail captured by CCD cameras. But it is important to stress, it takes years of experience and very good sky conditions to really be able to tease out subtle details from extended objects. Beginners observing from typical suburban skies should really stay focused on easier and brighter objects and not expect to see objects in the eyepiece resembling the pictures on the outside of the telescope shipping box. Part of the challenge and growth in the hobby is training your eyes to see things that aren’t obvious at first glance.
Typically, when the discussion turns to pictures and posters, a frequent statement I hear is: “I hear they photoshop the Hubble pictures and things really aren’t colored like that.” This one can be difficult to field because its true, every image from Hubble, as well as pretty much any other telescope picture posted on the web has been “processed” through a graphics editing package, frequently, Adobe’s Photoshop. Many pictures require stacking of sub frames, stitching together adjacent fields, layering shots taken through different narrow band filters, as well as using post-processing filters to enhance certain features in the photos. Yeah, I know, it sounds like a fancy way to say “photoshopped” and it is. But maybe it is better to focus on the intent of the question, which is: “Are they altering the image to show something that isn’t really there.” This is much easier to answer – No. Certain parts will be adjusted to show more or less detail depending on what the photographer is studying, but what we see in the photos represents photons captured by the camera at that time.
The Hubble color is usually easier: Yes, most colors in those photos are not the same as you would see with your eyes if you could see the object without a telescope. The smirk that starts to cross their face is short lived once I tell them, this is a good thing! Hubble, Spitzer, Herschel, and Chandra space telescopes are scientific instruments that capture data at wavelengths are eyes are not capable of seeing. If the colors were not adjusted to the narrow part of the spectrum we see, many of the really interesting and beautiful things we see would be invisible. A good comparison is wearing sunglasses on a bright day. Those glasses will preferentially allow certain colors of light to pass through to your eye while rejecting others – does that make what you see not real? I know the analogy is a bit of a stretch, but it usually makes the point.
Finally another very common question I hear is “I want to buy a telescope that I can use with my kids in my backyard, can I get a nice telescope for a couple hundred dollars?” I generally field this on a couple of different levels. First I write down this website, www.scopereviews.com/begin.html on a piece of paper and tell them when they’ve got some free time, read that page very carefully. It is a link to Ed Ting’s wonderful page of advice for beginners wanting to buy a telescope. Ed has years of experience both observing and testing various telescopes and his clear and well written page on the topic is without equal. Ed describes the different types of scopes, mounts, and eyepieces in plain English with lots of pictures and gives very sound advice. To me, sending folks to a website without any further discussion seems like I’m dodging the question, so I’ll usually preface the reading by explaining that yes, there are some very nice new telescopes in the $300 USD range and buying used from a reputable source (with help from an experienced telescope owner) can bring that number closer to $200 USD; HOWEVER, that won’t leave any money in the budget for the many other required accessories like eyepieces, red flashlights, atlases, or guides. Additionally, unless they live out in the country, the light pollution in their backyard will severely hamper what they can expect to see. What I usually do at that point is ask them where they live then go to the Astronomical League’s website and find the contact info for the club closest to them. I explain that most clubs will have beginner scopes that are easy to use for club members to borrow, they will have access to “dark sky” sites nearby where they can get away from city lights and see things hidden in the suburban glow, and they will be able to make sure the scope is properly assembled and collimated prior to use. AL affiliated clubs have very reasonable membership dues and by joining a club they will actually be getting access to nicer telescopes and they will be saving a lot of money. Its not that I don’t want them to buy a telescope, but rather, I don’t want to see yet another barely used 60mm f/10 refractor on a shaky tripod for sale on eBay or Craig’s list.
So those are some of the more common questions I’m asked as an amateur astronomer, what are yours?
You can find links discussed in this podcast, transcripts, and post responses or feedback at 365daysofastronomy.org.
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365 Days of Astronomy
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