Lunarglow – Astronomy & Space

Archive for January, 2010

I’m currently an undergraduate materials engineering student and I’m very interested in pursuing graduate studies in astrophysics. Is it possible, or am I required to have an undergraduate degree in physics or astronomy? Most of my courses are physics related, and I took linear algebra, differential equations, and vector calculus. However, I didn’t take quantum mechanics (strangely) or relativity. I appreciate all answers, and please if you can give as much details as possible.

If you like to look to the heavens even just occasionally get yourself some decent binoculars and indulge in a little binocular astronomy. Think about it, binoculars are inexpensive, highly portable and require no complicated setting up procedure so are ideal for casual astronomy.

Binoculars allow excellent moon views, and great viewing of star fields, comets and even deep sky objects. They are especially useful for beginners as unlike astronomy telescopes they keep the view the the right way up, making it really easy to navigate the skies. With a little practice you can pick out several of the planets and even the larger moons orbiting Jupiter. Clusters like Pleiades look great because the binoculars wide field of view lets you have more of the cluster in view at one time than a telescope would.

So how to choose which ones? Binoculars have two specifications marked on the body of the binocular in the form of 7x 50, where the first number represents the magnification (in this case 7 times) and the second the aperture in millimeters (50mm in this case). When it comes to selecting the right binoculars for astronomy, aperture is the most important feature to think about. The bigger the aperture the more light is captured so the brighter and clearer the image will be. For astronomy use you will need at least 40mm aperture and preferably larger.

You will need a magnification factor of at least 7, maybe up to 10 if you have a steady hand. Any higher than about 10 times magnification and you will need to mount your binoculars on a tripod as the hand shake effect makes it difficult to get a sharp image.

There are giant binoculars available with higher magnifications and apertures which are designed for astronomy use but you will certainly need a sturdy tripod or mount to use them. These can offer excellent viewing up to about 25 times magnification with 100mm apertures.

This brings us to another point, a specification known as the ‘exit pupil’. This specification refers to the diameter of the shaft of light that exits the eyepieces and into your eyes. You can easily calculate it by dividing the aperture by the magnification so that 7 x 50 binocular has an exit pupil of just over 7mm. Capturing as much of that as possible is good as it means all the available light is getting to where you want it, i.e.your eye. If you are still in your twenties you can probably use all of that 7mm exit pupil mentioned above as your pupils will dilate to about that size in very dark conditions, however as you get older your pupil does not dilate more than about 4 to 5 mm so large exit pupils are wasted (though it starts to make those 25x 100’s look good!).

You might notice another specification marked on the binocular, the field of view (FOV), it refers to the apparent side to side view as you look through the binoculars. It will be expressed as an angle in degrees or a measure such as 340 feet at 1000 yards. For astronomy use we can generally ignore that factor, it really does not matter a great deal at the distances we’ll be viewing at.

So now you have the basics why not get yourself some binoculars and indulge in a little casual astronomy, you’ll be rewarded with some wonderful sights!

The Raymond and Beverly Sackler Distinguished Lecture in Astronomy “The Dawn of Creation: The First 2 Billion Years” Steven Beckwith, Vice President for Research and Graduate Studies, University of California, Office of the President Modern technical wonders like the Hubble Space Telescope have made it possible to look back to a time when the universe looked very different than it does today, when the first galaxies were created and the universe developed structure seen as patterns in the galaxies apparent today. This years Sackler Lecture will look back to the first 2 billion years.

Astronomic binoculars are optical instruments used in stargazing or day and night sky viewing. It allows people to see far objects besides those seen by the naked eye. Choosing good binoculars for astronomic purposes entails some considerations. A good pair of astronomical binoculars is more effective as a telescope.

Binoculars are small telescopes mechanically linked together or mounted side by side, allowing distant viewing. It is handy, durable, light and easy to use. Astronomical binoculars can help you see up to 40% of a more detailed observation as compared to using only one eye with a telescope. In order to get high quality astronomy binoculars, one should follow certain considerations for good results:

Magnification
Choosing the magnification level also reflects the way it is intended for usage. With the handheld method, the setup time is zero. It has no accessories so as to drain the pocketbook. This means that one should keep magnification below 12x in order to maintain the steadiness of your binoculars. However, an objective size combination allows you to view hundreds of stars and galaxies, only through the use of a 7x to 12x binocular.

Hence, you can also determine the binoculars exit pupil (a virtual aperture in an optical system) which can match your eyes. It is done by dividing the size of the objective lens via its magnifying power.

A human eye has 2mm of exit pupils during the daylight, making it a type of high magnification. The exit pupil needs to be more than 5mm in low light so as to make it more usable. Since all binoculars have limits, one should consider the amount of distance to be achieved when focusing or the so-called eye relief. Binoculars having a 9mm eye relief can produce uncomfortable viewing.

A tripod can also help you to effectively handle magnifications over 15-20x. Astronomic binoculars have 15x to 30x and can result to a more detailed stargazing. This is while a 25×100mm can be very effective for a dark and clear night viewing.

Most giant binoculars possess a limit, especially for fixed magnification. This is although more model types now offer interchangeable eyepieces.

Sizes
Lens Size – Aperture (opening or a hole through which light is admitted) is referred to as the size of the objective lens. It is a light gathering source that plays a key role in suiting binoculars applications. More apertures mean better and brighter resolved images. The size and bulk can also increase proportionately. Binoculars are very portable, having a size that is less than 30mm. 5×25 or 5×30 models can also fit into the pockets easily. Low magnifications are necessary for this size range in order to keep a bright image.

Binoculars that have 40mm are considered as mid-range sized. It is used by most people for multiple applications. A 50-60mm lens size is far heavier that requires support. However, this is well suited for astronomy.

Mounts
Big binoculars need to have big mounts. The weight of the binocular can be compared with its maximum load capacity on a tripod. A tripod that has the capacity of at least 12 lb. and 15 lb. or more is best for an 80mm binocular.

Prism Type
Z shaped porro prisms are best suited for astronomy binoculars. Porro prisms have no mirrored surfaces and are less expensive. It can even inherent image sharpness which is intended for large hands.

The prism allows the body to be seen onto a far shorter view. This is because it folds the light path. It can also flip images and reflects the light path 3 times.

Focus Type
Astronomy binoculars use both CF (center focus) and IF (individual eyepiece focus). Center focus is versatile and easy to use, especially in refocusing other applications. If the focusing system is a more practical type, it is then easier to seal against moisture and dust.

Quality and Price
Most giant binoculars are made in China. Some Chinese optics is made with high optical standards. Popular brands include the following:
• Celestrons
• Oberweck
• Meades
• and Apogee
Small binoculars that are of the highest quality are sold under $25. Mid-sized types range from $50- $75. While the 80mm binoculars are sold at $100 and $300. Models with 100mm actually run for $400 to $1000, especially for deluxe interchangeable eyepieces.

The enjoyment of astronomy can be lifelong or just a whim but a lot hinges on how you have your first experience. The mysterious and divine beauty of the universe that you can discover could lead to many hours of pleasure but if there is no proper guidance, there can be many hours of disappointment. So it is essential that you get the right and best telescope that you can afford. 

When you are just starting out, do not attach too high an expectation that the universe will open up to your inquisitive nature. Those that you see in fancy science magazines are attributable to high level telescopes that only scientist and astronomer get access to. The sparkling stars that we see at night are just the tip and astronomy can offer many insights to our fabulous universe.

As a beginner, be circumspect before you look to acquire as some cheap telescopes have optics that verge on the worst, offering you hardly any view. But with a decent telescope, you can see the rings of Saturn and the disc of Jupiter. As you get more experience, you can make more sightings but don’t set too high expectations such as able to pinpoint planets that you find in glossy magazine. 

Before you probe deeper into astronomy, try to read magazines for instant “Sky and Telescope” to get an idea of how it is like. Astronomy is a joy and each finding add to your knowledge and satisfaction that our mysterious universe offer. 

To the absolute beginner, you can start with binocular and then advance to a full telescope. The portability and price tag is added attraction for anyone who is just beginning to learn astronomy. The basic telescopes usually come in reflecting and refracting types but reflecting types are less costly and enable you to view galaxies. Refracting telescope, on the other hand allow you to observe planets and stars but considerably more costly.

As telescope is bulkier, you can mount it on a tripod. When you are more experienced, you can try out different telescopes and find one that is suitable for you. Getting a used telescope can build you from the ground up and the alternatives are many. Choose one that you are at ease with and you will be on your way to a lifelong hobby that astronomy can offer. The universe is vast and mysterious and astronomy offers the opportunity to appreciate more of the existence of life and many of the inexplicable things that we are still trying to figure out.