The Sun’s photosphere extends near its surface, in the region where the gas becomes opaque, with an optical depth of up to 400 kilometers. Despite the light emitted, the photosphere is one of the coolest regions in the Sun’s atmosphere with a temperature of about 6000 K. This region is also the densest part of the solar atmosphere but still incomparable to Earth’s atmosphere. At a closer look, the photosphere is comprised of convection cells known as granules, which are gas cells with a diameter of about 1000 kilometers with a life span of about eight minutes, following a continuous boiling pattern. This region in the solar atmosphere often appears as dark specks called sunspots, which is caused by the Sun’s magnetic field.

Other astronomical bodies have a photosphere like the Sun. This region in an astronomical body’s atmosphere is often the deepest, which is transparent for photons in different wavelength of the electromagnetic spectrum. The photosphere is a visual description of the Sun’s or another star’s surface.

These illuminated reticles are actually needed to accurately align telescopes. It also has a grid of patterns placed in the eyepiece of an optical instrument and is also used to establish a scale or position. A reticle control would allow manual rotation of the reticle for use when it comes to lunar surface alignments. Crossing by the line on the star image defines a plane containing the star. Crossing of the other line defines another plane containing the same star or a different one.

The intersection of these planes forms a line that defines a direction of the star. To define the internal orientation of the particular star being viewed, sightings on at least two stars are required. Each star sighting requires the same procedure. Multiple reticle crossings and their corresponding marks can be made on either or both stars to improve the accuracy of the sightings. Upon completion of the second star sighting, the guide computer would then calculate its orientation with respect to a predefined reference coordinate system.

Centering stars without a reticle would be very difficult. It would be best to select the best reticle for your telescope to make sure that finding the stars and centering it would be easier.

However, if you were to view the same image through one that has got better resolving power, you would be able to see the details clearer. How is the resolving power measured? This is measured by the absolute smallest angle that can be resolved.

Did you know that there are some really powerful modern telescopes that are capable of counting the number of lines in President Roosevelt’s hair that was placed upon a dime located 3.7 kilometers away? For astronomers, it is all about getting the best telescopes with the greatest resolving power as this means that they would be able to view celestial objects better. This is also one of the reasons as to why radio telescopes are far bigger than their optical counterparts.

A good way of increasing resolution is to make an interferometer which is basically connecting telescopes together. The image would have the same sharpness as one that was taken by a single instrument which would extend from one end of this interferometer to another.
So there you have it, a few bits and bobs with regards to gauging a telescope’s resolving power.

With regards to astronomy, the universe has been known to be continuously expanding and along with it galaxies tend to move away from us. Accordingly, the light emanating from these galaxies is redshifted or change into longer wavelengths. This shift isn’t observed by the naked eye and is usually measured by comparing the spectrum produced by this light to that of a reference laboratory spectrum. By comparing the spectrum to known wavelengths, astronomers are able to determine the redshift occurring from these distant sources.

Stars with 10 solar masses become red supergiants once they have used up their fuel source which is usually made up of hydrogen. Once this happens, the stars turn to other sources of fuel such as helium, which does not produce as much energy. As a result red supergiants have very cool surface temperatures that range from 3500-4500 K. As the star progresses on its evolution, it fuses heavier elements together until such a time when iron builds up in its core – this marks the life of a star that is at its very end. A red supergiant will take about a few hundred thousand years before it reaches this stage.

The largest known red supergiant is VY Canis Majoris, while the most popular is Betelgeuse. Betelgeuse belongs prominently in the constellation Orion and is part of the famous winter triangle seen in the night sky. This star is found to be about 370 times larger than the sun with a luminosity that is 10,000 times brighter.

Red Supergiant Star

Currently there are seven main types of stars based on their temperature, O, B, A, F, G, K, M. Depending on their mass and stage of development however; stars may be classified as either dwarf stars or giants. Based on this grouping, scientists have found out that the most common stars in outer space are what they call red dwarf stars.

Red dwarf stars get their name because of their relatively smaller size and mass than the sun. These stars are known to have only a little less of the half of the weight of the sun. Their small size enables them to live for a very long time because they burn their fuel very slowly. However, because they burn only a little bit of fuel, red dwarf stars are also cooler compared to other stars and thus isn’t able to shine as brightly. Typically these stars only have a temperature below 4,000 K resulting in a faint light.

Though quite numerous in outer space, it will be very hard to see red dwarf stars in the night sky because of their small size and the faint glow that they give off. Probably the most popular red dwarf is the Proxima Centauri.

Currently there are different types of radiometers, each with its own way of detecting and measuring electromagnetic wavelength, but the most popular model still remains to be the Crookes radiometer. Made in 1873 by a physicist named Edward Crooks, this model is one of the earliest to have been used. It is made of a spindle fitted with a rotor and a set of vanes inside a partial vacuum. The vanes, which are painted silver on one side and black on the other, rotate upon exposure to light. This motion is commonly explained by physicists as the result of the heat generated upon absorption of the blackened side of the vanes of the photons from the light. The Crookes radiometer is used to provide a quantitative measurement of electromagnetic radiation. In principle, the more intense the light is that hits the vanes, the faster the rotation will be.

But as popular as the Crookes radiometer is, its use has been usurped by newer models such as the MEMS and Nichols radiometer which tend to be more diverse and sensitive in measuring electromagnetic radiation.

Crookes Radiometer

But what is relativity all about and how was it able to answer these questions? We can begin with what Einstein came up with, the idea that if we are to believe that the natural laws of the universe are absolute and true then they must be true under all circumstances and at all times. According to him, this is only made possible when elements such as space, time, matter, and energy are altered or are changed constantly in order to present us with the same circumstance every time. Applying that to observations of the universe, he supposes that even empty space can contract or expand depending on the position of the person observing it.

In astronomy, relativity has found its place especially when observing or studying objects that move in a strong gravitational field as well as those that are moving near the speed of light.

On earth, the regolith is typically called soil and is made from natural processes such as the weathering of rocks. The soil in this case is vital to the survival of the organisms residing in the planet because it is where plants grow and where human beings build. In the case of the moon however and other objects in outer space that have no known signs of life on them, the regolith serves no other known function except to reflect light from the surface. The regolith from these celestial bodies comes mostly from the debris left over from impacts with meteors or asteroids. Because most of these bodies do not have an atmosphere surrounding them, the impact is often very hard and even small meteorites can cause damage or leave debris.

The moon’s regolith in particular is called lunar regolith and was found to be around 20 meters only at its thickest portions. The composition is mainly rocks and minerals along with glass particles from impacts with asteroids. A famous photo of the lunar regolith was taken during the Apollo 11 mission and showcases the footprint of renowned astronaut Neil Armstrong.

The first convex lenses to be used in refracting telescopes were designed and made by a Dutch optician named Hans Lippershey in 1608. What he discovered about how looking through a concave and convex lens positioned in front of each other can make distant objects look very much nearer paved the way for the use of these lenses in telescopes. Just a year later, the first refracting telescope to be used in the study of space was made by Galileo Galilee. It was through this device that he was able to map the surface of the moon and to discover four of the moons circling Jupiter.

But how exactly does a seemingly simple device enable you to peer into outer space? Well for starters, refracting telescopes basically have two parts that function to gather and collect light – the objective lens and the eyepiece. The objective focuses the light by bending it into a focal point. This focal point is where the image is formed. Once the person looks into the eyepiece, a concave lens will gather and focus more light than the eye could so that a magnified image can be seen.