APOD 1.8

Over the span of this beautiful October sky-view, from a cushy lakeside campsite in Northern Maine, two important objects can be observed. The Milky Way Galaxy span over the mountains, all aglow with a faint orange. Zodiacal light, a sweep of dust scattering sunlight along the ecliptic, stretches horizontally, the intersection with the Milky Way marked by a bright, shiny Jupiter. Past the star cluster Pleiades and to Jupiter's right is Gegenschein, the brightening of the Zodiacal which typically remains unseen unless the night is right. From behind the mountains, Begirt and many other stars rise, and in the lake is a reflection of the Hunter Orion.

Chapter 5 Sections 1-3 Outline

Telescopes capture as many photons as possible from a region of the sky, focusing the beam of raditation so astronomers may analyse it. Optical telescopes collect wavelengths visible to the human eye, a tool used for centuries and likely the most well known of astronomical instruments. Infrared and ultraviolet radiation, while invisible to us, is also a spectacle for most observed celestial objects as well.

An optical telescope can refract or reflect. Refracting telescopes use a lens to gether and concetrate a beam of light, bending it as it passes from one transparent meduim into another. The beam goes through the focus so an astronomer may take it in, with the distance between the primary mirror and the focus known as the focal length. Reflecting telescopes, meanwhile, use a curved mirror rather than a lens, utilising that to focus on incoming light. The collecting mirror is known as the primary mirror, and the focus of the primary mirror is referred to as the prime focus. Images are formed near the prime focus, capturing a scene of an entire field of stars. This image is magnified by the eyepiece, or otherwise recorded as a digital photograph.

Reflective instruments tend to be favoured over their refractive counterparts due to several facts. For one, in view of a refractor, light must pass through or else they will be left at a crucial disadvantage. Chromatic aberration is the deficancy suffered by these, for they disperse blue and red light differently. Some light can also be absorbed by the glass, creating minor visual problems and major infrared and ultraviolet issues. Larger lenses tend to be on the heavy side, and the lens will deform under its own weight. None of these problems occur with mirrors, which also have but one surgace that needs accurate machining and polishing versus the refractor's two, thus making reflection the simpler choice among light gatherers.

In reflective instruments, light is often intercepted on its focal path by the secondary mirror, redirecting it to a more convinient local. The Newtonian telescope illustrates the light intercepted before reaching the prime focus, then deflected by ninety degrees to the eyepiece. While this remains popular in small instruments for hobbiest amatuers, larger instruments rarely use Newton's design in favour of a Cassegrain telescope, in which the primary mirror reflects light to the prime focus and is then intercepted by a small, secondary mirror, which reflects through a small hole in the primary mirror's centre. Larger instruments typically result in more complicated forms of relfection, with more angles of reflecting for more precise and accurate measurements. The best known of the Cassegrain telescopes is the Hubble, measuring from infrared to ultraviolet waves on the spectrum.

Size and light gathering power are commonly associated, for usually the larger a telescope is, the more power it holds. The resolving power is another factor, for it can focus on more radiation than smaller counterparts and enable more in depth study of fainter celestial objects and gain more knowledge on the brighter ones too. The greater light collecting area allows more capability of gathering large amounts of radiation, increasing and enchancing viewing abilities. Angular resolution also grows finer with size, eliminating some of the cumbersome troubles caused by light's diffraction, which makes the image fuzzy. Diffraction-limited resolution is a quality which, as it states in the name, limits the diffraction and makes for a finer picutre that can be closely studied without unneeded fuzz.

Images coming in from the telescope are just as important, for they are just what the astronomers need to analyse. Charge-coupled devices--also known as CCDs--are widely used, these electronic detectors far more conventional than photographic equipment. The device consists of a wafer of silicon divided into pixels, an electronic charge building upon it when light hits it. The charge is directly proportional to the number of photons striking the pixel, transfering the intensity of said light into the image itself. They serve as much more efficent tools than photographic plates and show a higher level of detail while also possessing the nifty capability of digital duplication,making for easy access.

Computers reduce the unwanted background noise of astronomical images, taking away the static snow that corrupts telescopic images. Imperfections in the detector, interferences in the Earth's atmosphere, and faint, indecipherable noise coming from the cosmos contribute to this nuissance, but origin cannot typically be determined. Computers can produce a clean image that extract the noise and leave a clear picture.

The angle of light is inversely proportional to the accuracy of the focus, an increase in angle resulting in a decrease in clarity in an effect called coma. Thus, wide-angle views are not as common, for it is very easy to degrade the quality so much that the image cannot be salvaged and is a waste.

When a CCD is places at the telescope's focus, the telescope will act as a high-powered camera; however astronomers often desire more specific radation measurements than just that. The brightness is one of the most crucial components of star studies, the measure of such known as photometry. Filters limit the wavelengths measured by photometric images, and often three images result (taken with blue, red, and green filters respectively). Highly accurate and rapid measurements of light intensity typically are measured by a photometer, measuring the total amount of light recived in all or part of the field view.

Spectrometers study the spectrum of incoming light, redirected and defined by a narrow slit, then displaying a spectrum of light made of its components. This can be used to tell what element or elements dwell in the stars.

Tycho Brahe

Born in a circle of high nobility in the country of Denmark--then an expansive empire which bled into modern Sweden and Norway--Tyge, known more commonly by the latinised version, Tycho, Brahe was born in 1546 on the 14th of December. Jørgen Thygesen Brahe, brother of Tycho's father Otto, raised the young astronomer, educating him as preparation for being his heir. 

Tycho attended several universities, including ones in Wittenberg--where, in 1566, he lost the tip of his nose in a duel, leaving him to using a metallic replacement for the rest of his life--Rostock, Basal, Copenhagen, and Leipzig, his travels around the Germanic area and academia piquing interests in the celestial realm. Alchemy and astronomy caught his eye, his new impulses leading him to observe the cosmos upon his return to Denmark in 1570. 

A precursor to Brahe's claim to fame as documenter of the stars, he discovered a new star in the constellation Cassiopeia, writing about it in 1573 (a year after his find) before taking a job at the University of Cophenhagen lecturing on the science of the stars. A firm believer of the Aristotelian belief of an unchanging celestial sphere due to lack of parallax, he felt as though astronomy could be improved through accurate observations. 

Following another tour of the Germanic states, meeting up with various astronomers, King Frederick II funded Brahe's observatory on the island of Hven. Uraniburg, as it was named, stood as the best observatory of the time, housing newly innovated and calibrated instruments to aid Brahe in his extensive night time observations. There, he trained a new generation of budding astronomers before leaving Denmark after a dispute with King Christian IV. 

He became the Imperial Mathematician of the court of Emperor Rudolph II, settling in Prague to still continue his observing and training. Johannes Kepler, who developed the laws of planetary motion using Brahe's data years after his mentor's death, served as his assistant. At the age of 50, Brahe died on October 24th of 1601, suffering an exploded bladder following a banquet he attended in Prague, valuing party etiquette over basic human need for urinary relief. 

Several of his observation books survived, schooling future generations of the placement of objects in the heavens, which he described as moving in orbits. In 1572, he discovered a supernova--that being the new star in Cassiopeia--and created a geo-heliocentric universe (which his assistant later proved to be a solely heliocentric universe). 

APOD 1.7

In the too beautiful and glorious country of Norway, near the urban centre of Tromsø, two celestial spectacles occurred simultaneously in mid-September on one fateful night. Through a low green aurora shined a red one, the two overlapping to create a strange violet that streaked the sky (don't ask me how red and green make purple!). Then, bursting through the painted sky, the brightest fireball ever recorded by astronomer's eyes shot through the atmosphere, the meteor gifting the distant peak of Otertinden of the Lyngen Alps with a glowing halo round its peak. Several other times in history has such an event been recorded--numerous times in the Tromsø area--however this particular image offers a stunning reflection of the sky in the Signalelva River, as seen in the foreground.

APOD 1.6

The water bearer, Aquarius, houses a dying star seven hundred light-years away. NGC 7293, or the Helix Nebula, is the result of thousands of years on its deathbed, producing a well-studied paragon of a planetary nebula, as many stars will do towards the end of their scintillating days. The photo above is a result of 58 hours of exposure, ensuring the display of the hydrogen red ring and the inner area of oxygen aqua. In the rings, in a photograph taken by the Hubble, gaseous knots form in the detail of the cloud, between the inner region and outer halo. The darker, more prominent inner region spans about 3 light-years, while the faint halo expands its length to over 6 light-years across. The white dot at the centre is the hot and dying star. While this nebula looks simple, it has a complicated geometric structure.

Observation Oct 4

At approximately 6:35am, upon leaving the house to head off to school, I looked up at the sky to see the fading celestial sphere overhead (as my father drives a convertable giving me this oppurtunity to look at the skies often when going to Pine View). I was happy to spot Orion, recognising his belt immediately, the Hunter standing at about 45 degrees in the night. I proceded to watch him during my trip from my home on Siesta Key to Osprey, and only around the Bay Street traffic light at around 6:50am. I could not make out the redness of Betelgeuse, but seeing Orion early in the morn did improve my day.