Amateur Astronomy

[El Fiji Grande]

Have you ever looked up at the night sky, and wondered what lies beyond? If so, this might just be the thread for you.

Growing up, I was fascinated by astronomy, and loved to pore over pages of nebulae and galaxies, many as seen by the Hubble Space Telescope. Nevertheless, I never really became personally acquainted with the constellations, and had only occasionally observed stars through telescopes at star parties. While my connection with space is an intrinsic part of who I am, to this day I feel lost when I look up at the sky. Instead of providing a foundation, I only feel confusion when attempting to find patterns in the heavens. I've been meaning to change that for some time, so this thread will be as much a personal exploration of my adventures as it will be a guide for those who wish to follow in my footsteps.

One of the things I should get out of the way before we begin though is that you should lower your expectations. Photos of nebulae, galaxies, and star clusters help inspire the imagination of the public, but you can't take them for granted. A question I often get is if the photos we see of these objects are real. And the answer is... yes, but only from a certain perspective, and it can be difficult to tell what you're really looking at. Astronomers often observe deep space objects in different wavelengths of light in order to understand their composition, texture, and other properties. These wavelengths are often not within the visible spectrum, but can be recolored to provide meaning in a way we can see. One example is the famous photograph New Horizons sent back from Pluto. Seen below, the left-hand image is what is often publicized, but the right-hand image presents true color (though it is rotated a bit relative to the other). One isn't more correct than the other; they're just different ways of viewing the same object. This is important to bear in mind, because many nebulae you see in photos are somewhat embellished by these color corrections, and may not be what you can expect to see with your own eye. Moreover, many of these objects are extraordinarily dim, and so can be exceedingly difficult to see unless you stack many exposures on top of one another, forming a composite image.

So with that aside, let's get started! The first thing I recommend is to simply spend a bit more time outside past sunset, stargazing. You don't need any special equipment, though depending on the weather and your environment, you may want to bring a coat and some bug spray. I'd also recommend on bringing some water in case you get thirsty. You can stargaze from anywhere - even if all you have is a small apartment in a bustling city. As a rule, though, you'll want to find a place that's suitably dark. I recommend checking light pollution maps to help find a decent spot. You'll want somewhere that's not too far out of the way, because you want it to be convenient enough that the distance doesn't prevent you from going frequently. I generally find a quiet park where I can lie on my back and look up at the sky.

The darker your environment, the more you will see. Even so, it can take time for your eyes to adjust, so turn off any light sources like flashlights or your phone, and breathe in the smell of nature around you. Looking up, you'll notice that some stars are visibly brighter than others. These stars are either brighter or closer to Earth. If you draw lines between the brightest stars in the sky, you'll start seeing patterns. If you do a bit of research on what constellations you can expect to see in your hemisphere, you may start recognizing them in the sky above. Some of the easiest to see in the northern hemisphere are:

In the above order, the constellations shown are: Cassiopeia, Ursa Major & Ursa Minor, Orion, and the Pleiades. Cassiopeia forms a distinctive 'W' shape. Ursa Major (the big dipper) points to the North Star (Polaris), as shown, which can be used to find Ursa Minor (the little dipper). Orion is easily recognizable by his belt, which is formed by three very bright stars all in a row. The Pleiades are a small cluster of bright blue stars. I recommend getting a guidebook, starmap, or phone app to help you learn the constellations. Of note is that not all constellations can be seen at once. Depending on your hemisphere and time of year, only certain constellations can be seen. The tools I use for finding and learning about constellations are the Philip's Night Sky Atlas, one of the northern latitude Miller Planispheres, and the phone app Star Walk 2.

Once you've spent a bit of time observing the night sky, you'll also start to see faint points of light that look like stars, but are actually moving. They're most certainly not planes since they don't make any noise, don't have blinking lights, and move at a constant rate from one horizon to another. What you are seeing are satellites. Best seen after dusk and before dawn when the sun's rays reflect off of their metallic bodies, satellites are constantly zipping around our planet. You're likely to see at least one satellite if you spend at least fifteen minutes stargazing. There are thousands of satellites and pieces of debris orbiting Earth, but you won't be able to see them all. Many of these objects are too small or don't reflect enough light to be made out by eye. A good way to tell if you might be able to see a certain object is by researching its apparent magnitude, which is the brightness of any object in the sky. The more bright an object is, the lower its apparent magnitude is, with the brightest objects even having negative magnitudes. Thus, seeing Venus - which has an apparent magnitude of -4.2 - is much easier than seeing Vega - which has an apparent magnitude of 0. If you see a satellite in the sky and want to know what it is, a great app is Heavens Above, which will give you a lot of information about the object, and help you predict other passes of objects within your field of vision.

To help improve your experience with stargazing, a quality pair of binoculars can expand your ability to make out details in the sky. You don't want to purchase binoculars with too high of a magnification, since doing so will make the set heavier - and thereby more tiring to hold - as well as more difficult to get the image to remain still within your view. A good option would be binoculars that offer about 8-10x magnification and have fairly wide lenses. I use 10x50 binoculars. Binoculars will enhance your view of the sky, allowing you to see much more detail on the moon and other night sky objects. My friends swear they've seen detail on the gas giants with a decent set of binoculars, but I have yet to have any luck with this.

 

[El Fiji Grande]

If you've spent a bit of time stargazing and have been enjoying your time outside, humbled by the magnificent scale of the universe, but are interested in seeing more, then investing in a telescope might be for you!

There's a lot that goes into choosing the right telescope that fits your needs. What do you want to look at? How much storage space do you have? How important is portability? How dark is the sky at your observing location? What kind of mount do you want? What level of automation or computerization are you interested in? What does your budget look like?

Before getting into the details on aperture, magnification, and the pros/cons of different types of telescopes, it's best to address some of the more basic questions here. I think the most important lesson is that it is the telescope you use the most that will show you the most. As such, you shouldn't disregard portability and storage space. The largest, heaviest telescopes will be by far the most difficult to move, and require considerable space when not in use. Will it fit in your car? Is it something you can set up by yourself? Do you have to carry it up or down stairs?

With that out of the way, I suppose it's important to briefly explain how telescope work, or at least discuss what factors are most impactful to their performance. I'll let Greg Foot of the BBC Earth Lab give you the basic rundown of how refractor and reflector telescopes work, because right now I can't be bothered. I also I encourage you to read the wikipedia articles on refracting and reflecting telescopes to learn more about how they work.

The most important factor for determining a telescope's performance is its aperture. The aperture of a telescope is the diameter of its main optical component, whether that be a lens or a mirror. Often, that's pretty close to the diameter of the tube. Aperture is important because it is what allows your telescope to collect light. The larger the aperture, the better, since it gathers more light, often allowing you to see dimmer objects in the sky. Aperture also affects the ability of your telescope to magnify objects in the sky, because after a certain point, the object is either too dim or too blurry to make out any details. The rule of thumb for determining maximum effective magnification of a given scope is about 50x its diameter in inches, or double its diameter in millimeters. So, for a telescope with a 130mm aperture, the best magnification you can probably expect is ~260x, and that's only in the best sky conditions. That said, larger aperture telescopes are still useful for observing the dimmest objects in the sky, like deep space nebulae and distant galaxies.

So what about magnification? It may surprise you, but any given telescope doesn't have just one, set magnification. Rather, any telescope can provide almost any magnification you want, and is only limited by the focal length of the eyepiece you use. To calculate magnification of a particular configuration, take the focal length of the scope and divide that by the focal length of the eyepiece you're using. For example, a 1000mm scope and a 20mm eyepiece would produce a magnification of 50x. As I mentioned before though, don't get carried away just seeking the highest magnification, because the amount of detail you can see clearly is limited by the aperture of the telescope. And further, don't get carried away maxing out your aperture either, since in all but perfect conditions, atmospheric turbulence will cause distortions in your image. As a result, you'll rarely find use for any scope with more than 250-300x magnification.

To minimize these atmospheric distortions, you'll want a cold, dark viewing spot, away from rooftops, city lights, or asphalt, preferably at a high altitude and on a calm, clear night. Naturally, you don't want clouds blocking your view or wind to disturb the air. Rooftops and asphalt (like roads and parking lots) absorb heat during the day, and can let that heat off during the night, causing the air to wobble. This can blur your image. The colder the air, the more still it will be. The higher you are, there will simply be less air for you to contend with. It can really be difficult to perfectly minimize all of these factors, so finding a good spot that is close enough is ultimately worth more, because you'll be able to get out more frequently. It also helps to check the weather before you go out observing to help you predict whether or not the sky will be clear. If you're located in the US, I recommend the Clear Sky Chart and infrared satellite maps.

As was discussed in the video, there are a few different types of telescopes. I won't cover them all here, but I will present a sort of "buyer's guide" to refractors, reflectors, and compound telescopes.

Refractor Telescopes

Advantages
Provide crisp, high-contrast images	Are long and often unwieldy, requiring large, solid tripods
Require less maintenance than other scopes	Are often more expensive at any given aperture

[TH]Disadvantages[/TH]

Reflector Telescopes

Advantages	Disadvantages
Are more often more portable than refractors	Require periodic collimation
Most bang for buck, at least in terms of aperture	Require occasional cleaning
Do not flip image	Mirrors can degrade over time

Compact Telescopes

Advantages	Disadvantages
Are very compact and portable	Require periodic collimation
Often have most flexibility for use and with accessories	May require a collar to prevent misting on objective lens

It would be remiss for me not to discuss telescope mounts as well, since a telescope is completely useless unless you can point it at what you want to look at and have it be steady enough for you to make out detail. There are two very common types of mounts: alt-azimuthal (alt-az) and equatorial mounts. Alt-az mounts have one axis that is parallel to the ground and one axis that raises the scope towards the sky. It essentially pans and tilts like a camera tripod would. In my opinion, they are fundamentally more intuitive to use since it moves in easily described ways that we are already familiar with. Equatorial mounts also have two axes, but they are tilted such that they align with the rotational axis of the Earth. Not only is this motion less intuitive and more difficult to point where you want it, you also have to align it with the North Star (if you're in the northern hemisphere) to get it to work properly. I will describe this alignment process in more detail once I succeed in doing it myself. Equatorial mounts are more difficult to set up and can be quite frustrating for a beginner. That said, once aligned properly, they track objects in the sky much more easily and are thus better for astrophotography. Both alt-az and equatorial mounts will have slow-motion controls which allow you to manually adjust and fine-tune the orientation of the telescope. This is extremely helpful when tracking objects across the sky, especially at higher magnifications.

While I hope this guide has presented some direction, I encourage you to conduct your own research before making a decision.
~ work in progress ~

 

[El Fiji Grande]

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[El Fiji Grande]

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[El Fiji Grande]

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[El Fiji Grande]

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