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Tuesday August 4th 2015

‘Planet Positions’

Top 10 Night Sky Objects for Astronomy Beginners

Orion Nebula (M42), Image credit: Wolf DammYour first telescope has just arrived and now you can’t wait to try it out. Trust me, I remember this feeling very well. The universe is calling and it want to be discovered by you. There are so many exciting objects to explore. So, what to aim your telescope at?  I created a list of ten celestial objects that are great for beginners who own binoculars or small telescopes. The targets described represent different kinds of objects that exist in the universe. All objects are easy to find, and their size makes them equally suited for refractors, reflectors, catadioptric telescopes or binoculars. With the exception of the last listing, the Dumbbell Nebula (M27), all objects can be observed even with full moon.

Top 10 Objects for Binoculars and Small Telescopes

Top 10 Night Sky Objects for Astronomy Beginners A short version of the Top 10 Night Sky Objects can be download as PDF and printed. It is a one pager and serves as reference for the field. Links to constellation maps are offered for all stars and deep sky objects. I really recommend a planisphere for beginners; it makes it so much easier finding constellations at a certain day. Alternatively, SkyMaps offers a great monthly two- pager that shows all visible constellations and provides useful further information about current stargazing objects.  These maps are also free and can be downloaded as PDF.

 

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Moon

MoonThe Moon is an ever fascinating object that can be observed almost throughout the year. Common presumption is that the moon can be seen best at full moon, but this is actually not the case. The best time is when it is a quarter or less. Sun light comes now from the side and moon features cast long shadows which render the telescope view almost plastic. It is most exciting to observe along moon edges and the Terminator, the line where the dark and illuminated areas come together.

Facts:
The Moon came into existence when a Mars-size planet crashed into the early Earth. Fragments orbited the Earth and coalesced within just several weeks to become the Moon. The dark areas visible today at the moon are called Maria, from Latin “Sea”. They are meteorite craters that flooded with hot lava. Lava layers can be up to 10 km (6.2 miles) thick, higher than Mount Everest. Diameter: 3 476 km (27% of Earth)
Distance to Earth: 384 000 km (199,000 miles)
Mass: 7.350 x 10E19 tons (1.2% of Earth)
Density: 3.341 g/cm3 (61% of Earth)

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Jupiter

Jupiter is the fifth and largest planet in our solar system. It is a gas giant which is primarily composed of hydrogen and helium (very similar to our sun). Jupiter may also have a rocky core of heavier elements.

Jupiter is the largest planet in our solar system. It is a very bright and exciting object to observe. Four moons can be seen even with small telescopes or binoculars. If the conditions are good some cloud bands are visible, and with larger telescopes it might be possible to see some cloud details and the great red spot.

TIP: It is fun to draw the position of the moons and follow them over a period of time.

Click here for more information about the position of planets.

Facts:
Jupiter is a gas giant with over 100 moons. The four largest are Io, Europe, Ganymede, Callisto. They are also called the Galilean moons. When Galileo saw the movement of the moons he could no longer accept a geocentric model of the universe. Diameter: 142 980 km (11.2 x Earth)
Mass: 1.899 x 10E24 tons (318 x Earth)
Density: 1.32 g/cm3 (24% of Earth)
Distance from Sun: 4.95 AU

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Saturn

Saturn, Image credit: Wolf DammSaturn is probably the most enigmatic of all planets. Its rings have given awe to many people who saw it the first time. Since Saturn is double as far from the Sun than Jupiter, it receives only a quarter of the light. While it has almost the size of Jupiter, Saturn’s larger distance results in a smaller, fainter view in the eyepiece. We tend trying to compensate by increasing magnification, but this multiplies air layer disturbances as well. Unless seeing conditions are perfect, a good compromise is a magnification between 100 and 150.

With a very small telescope or under not so good seeing conditions, Saturn’s rings might just be seen as “ears”.  In fact, this is what Galileo saw when he first looked at Saturn with his telescope. He concluded that these “ears” must be two close moons on either side of Saturn, but two years later the moons were gone, and again two years later the moons re-appeared. We know today, that the “disappearance” was caused by looking at the ring edge on but it was very confusing for Galileo at that time.

Click here for more information about the position of planets.

Facts:
Saturn is a gas giant, and has over 62 moons, with Titan and Rhea as the largest ones. Saturn has a very low density, in fact if we could build a bathtub large enough to hold Saturn, it would float on the surface. Diameter: 123 000 km (9.4 x Earth)
Mass: 0.569 x 10E24 tons (95 x Earth)
Density: 0.67 g/cm3 (24% of Earth)
Distance from Sun: 9.54 AU

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Mizar & Alcor

The Big Dipper is probably the best known asterism for stargazers in the Northern hemisphere. Big Dipper consists of seven stars and belongs to the constellation Ursa Major, or Great Bear. It is easy to find and its serves as guidepost to Polaris. Find the brightest two stars at the outer bowl edge, Dubhe and Merak. Take 5 times their distance and you reach Polaris, the Northern Star.

Mizar & Alcor
Mizar & Alcor (click on image for larger scale)

Big Dipper holds some surprises that are revealed at closer observation. Point your telescope at the handle bend and what you see are not one but two stars. The brighter one is Mizar, the dimmer star is Alcor. They are also known as “Horse and Rider”. People with good eyesight can distinguish these two stars with bare eyes. If the seeing conditions are good, choose high magnification and take a closer look at Mizar. You will see that Mizar itself has another close companion star.  The image above shows an actual photo of Mizar A, his close companion Mizar B and Alcor (click at the image to open a larger scale version).

Click here for a star map of Ursa Major.

Facts:
The Mizar – Alcor system consists of even more stars that are however too faint for small telescopes. Four stars belong to the local Mizar system and the Alcor system consists of two. New research has revealed that both systems are gravitationally linked, making Mizar & Alcor a true 6-star system. Constellation: Ursa Major, UMa
Magnitude (Mizar/Alcor): 2.2 /4.0
Separation: 11.8′
Distance: 83 Light years
Mass (Mizar/Alcor): 7.7 /2 x Sun, Diameter: 4.1 / 1.8 x Sun
Luminosity: (Mizar/Alcor): 63 / 13 x Sun

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Albireo

In the night sky: late Spring to Fall.

Albireo, HunterAlbireo is the fifth brightest star in the constellation Cygnus (Swan). With naked eye it appears to be single star but a telescope resolves it as double star. Both stars offer a striking color contrast. The brighter star shines in yellow color, the smaller star in blue.

Image credit: Hunter Wilson.

When observing colorful stars, it can be beneficial to do this somewhat out of focus. Since the star disks become larger, colors become more prominent. The reason for this is that a larger number of color receptors in the eyes can collect color information . Play with your focuser and see what works best for you.

Click here for a star map of Cygnus.

Facts:
At this point it is unknown whether the stars are optical doubles or gravitational linked and orbiting each other.The brighter star itself has a very close companion, too close though to be resolved with a telescope. Constellation: Cygnus, CYG
Magnitude: A 3.2, B 5.8
Separation 35″
Distance 390 / 390 Light years
Mass: 5 / 3.2 x Sun
Diameter: 16 / 2.7 x Sun
Luminosity: 950 / 120 x Sun

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Orion Nebula (M42)

In the night sky: Winter and Spring.

Orion Nebula (M42)The Orion Nebula is part of the constellation Orion. This truly beautiful nebula can be found just below Orion’s belt as a part of Orion’s sword. It is one of the brightest nebulae and is visible to the naked eye.

Because M42 is over an arc minute wide use your lowest magnification to ensure it fits in the field of view. The four stars at its center are called “Trapezium”, they energize and ionize surrounding gasses which leads to this beautiful spectacle.  Due to its brightness the Trapezium stars draw the observers attention, but scanning the area around them, you will see many smaller stars and layers of ionized gas.

Click here for a star map of Orion.

Facts:
Orion nebula is the closest region of massive star formation to the Earth. It hosts protoplanetary discs and brown dwarfs. New stars and planets are born here right now. The strong radiation emitted by the Trapezium stars is so powerful that young neighbor stars are pushed into the form of an egg. Constellation: Orion, ORI
Magnitude: 4.0
Size: 65’x60′
Distance 1,344 Light Years
Diameter: 24 Light Years
Mass: 2,000 x Sun

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Andromeda Galaxy (M31)

In the night sky: Summer, Fall and Winter.

Andromeda Galaxy (M31)The Andromeda Galaxy belongs to the constellation Andromeda. It is the farthest object that can be seen with bare eyes. It is so large that it will most certainly exceed the field of your telescope view (binoculars have sufficient viewing angle) Nevertheless is a fascinating moment taking a peak at another Galaxy for the first time. The core is very bright and the surrounding areas can be seen nicely.

There are many ways finding the Andromeda Galaxy in the night sky. My favorite is to extend the most pointy part of the Cassiopeia “W”three times.

Click here for star maps of Andromeda and Cassiopeia.

Facts:
The Andromeda Galaxy is a spiral galaxy has an estimated 1 Trillion stars (Milky Way 200 – 400 Billion). Its center comprises a massive black whole. Andromeda Galaxy will and the Milky Way are moving towards each other. They will merge in about 4.5 Billion years. Constellation: Andromeda, AND
Magnitude: 3.44
Distance 2.54 Million Light Years
Mass: 1- 1.5 x Milky Way Galaxy

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Hercules  Cluster (M13)

In the night sky: Spring, Summer and Fall.

Herkules Globular Cluster, Image credit: ESA, NASAAs it’s name already reveals, the Hercules Global Cluster lies in the constellation Hercules.  The Globular Cluster is almost as old as the known universe and offers beautiful view even for small telescopes.

Image Credit: ESA, NASA

It is a bit more challenging to find Hercules Globular Cluster. First we have to find “The Keystone”, four stars of the constellation Hercules that build a trapezoid. M13 lies on the line between Eta Herculis and Zeta Herculis. These are the two stars in “The Keystone” at the side of Arcturus. Move a little bit towards Eta on the Eta-Zeta line and you have found this beautiful globular cluster. If you have difficulties to find “The Keystone”, two bright stars, Vega and Arcturus help. Draw a line from Vega to Arcturus, “The Keystone” is located about one third the distance from Vega.

Click here for a star map of Hercules.

Facts
Despite it’s age, Hercules Globular Cluster has not changed its form much. Pressure of star radiation pushing stars apart and gravity force pulling them together, resulting in an equilibrium. The stable conditions were thought to be beneficial for possible forming of life. In 1974 a radio message was sent to the Hercules Cluster with the large Arecibo radio telescope. The digital message included information about man, earth and the solar system. Constellation: Hercules, HER
Magnitude: 5.8
Distance 25,100 Light Years
Diameter: 168 Light years
Mass: 600,000 times Sun
Age: 14 Billion years

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Double Cluster (NGC 869 & NGC884)

In the night sky: Fall, Winter, Early Spring.

The Double Cluster (NGC 869 & NGC884), Image credit: Wolf DammIn his classic Field Book of the Stars (1929), William Olcott called the Double Cluster: “One of the finest clusters for a small telescope. The field is simply sown with scintillating stars, and the contrasting colors are very beautiful”. Does this not make anyone thrilled to observe this fine object? What we see are in fact two independent open clusters. They are about 800 light years apart but due to their position in the sky, they fit both in the view of a small telescope.

The Double Cluster belongs to the constellation Perseus. It can be easily found with the help of the constellation Cassiopeia. Just follow the inner leg of the shallow half of the “W” (Cassiopeia Gamma – Delta) about two third of the way to the next bright star, and you will find the Double Cluster.

Click here for star maps of Perseus and Cassiopeia.

Facts:
The Greeks knew about the object as early as 130 BC, but the true nature of it was not discovered not before the telescope was invented.
The radiant of the Perseid meteor shower (Aug 12 & 13) is located in the neighborhood of the Double Cluster (SW).
Constellation: Perseus, PER
Magnitude: 4.2
Distance (NGC 869): 6,800 Light Years
Distance (NGC 884): 7,600 Light Years
Age (NGC 869): 5.6 Million years
Age (NGC 884): 3.2 Million years

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Dumbbell Nebula (M27)

In the night sky: Fall, Winter, Spring

Dumbbell Nebula (M27), photo credit: Wolf DammWith a magnitude of 7.5 , the Dumbbell Nebula is the faintest object in our Top-10 list. It is however the second largest planetary nebula in the northern sky and can be found relatively easily. The Dumbbell Nebula is located in the constellation Vulpecula, Latin for “Little Fox”. Vulpecula is a very small constellation with faint stars, southwest of Albireo in the constellation Cygnus. My preferred way to find M27 is with the help of the constellation Sagitta, the “Arrow”, just south of it. Its stars are brighter so they are easier to make out. They are shaped like an arrow with feathers (or a triangle  with tip). The Dumbbel Nebula, M27 is pretty exactly north of Sagitta’s tip star, Gamma Saggitae.

Click here for star maps of Vulpecula, Cygnus and Sagitta.

Facts:
M27 is a planetary nebula. This term was coined by early astronomers who thought these nebulae were planets. In fact, they have nothing to do with planets. Planetary nebulae are clouds of material, shed by a star. It glows because it is excited by radiation emitted by a nearby object. Constellation: Vulpecula, VUL
Magnitude: 7.5
Distance 1,360 Light Years
Diameter: 1.44 Light Years
Central star
Dia: 0.055 Sun, Mass: 0.56 Sun
Age: only 9800 years

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Further Material

 

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Positions of Planets

Saturn, credit: Nasa
Saturn, image credit: NASA

The tables offer monthly positions of the four brightest planets: Venus, Mars, Jupiter and Saturn. Note, that a constellation may not be visible during the night.  Another good monthly reference is created by the folks of SkyMaps.  It shows monthly events and locations of planets and can be downloaded as pdf for printing.  Also Sky View Cafe and Astronomy Magazine offer very nice online planetaria that show positions of planets and provide a wealth of other information. Both need Java installed on your computer.

2012 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus AQR PSC ARI TAU TAU TAU TAU GEM CNC LEO VIR LIB
Mars VIR LEO LEO LEO LEO LEO VIR VIR LIB SCO SGR SGR
Jupiter ARI ARI ARI ARI TAU TAU TAU TAU TAU TAU TAU TAU
Saturn VIR VIR VIR VIR VIR VIR VIR VIR VIR VIR VIR VIR
                         
2013 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR CAP AQR ARI TAU GEM LEO VIR VIR OPH SGR SGR
Mars CAP AQR PSC PSC ARI TAU GEM GEM CNC LEO LEO VIR
Jupiter TAU TAU TAU TAU TAU TAU GEM GEM GEM GEM GEM GEM
Saturn LIB LIB LIB VIR VIR VIR VIR VIR LIB LIB LIB LIB
                         
2014 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR SGR CAP AQR PSC ARI TAU CNC LEO VIR LIB SGR
Mars VIR VIR VIR VIR VIR VIR VIR LIB SCO OPH SGR CAP
Jupiter GEM GEM GEM GEM GEM GEM CNC CNC CNC LEO LEO LEO
Saturn LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB
                         
2015 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus CAP AQR PSC TAU GEM CNC LEO LEO CNC LEO VIR LIB
Mars AQR PSC PSC ARI TAU TAU GEM CNC LEO LEO VIR VIR
Jupiter LEO CNC CNC CNC CNC LEO LEO LEO LEO LEO LEO LEO
Saturn SCO SCO SCO SCO SCO LIB LIB LIB LIB SCO SCO OPH
                         
2016 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus OPH SGR AQR PSC ARI TAU CNC LEO VIR LIB SGR CAP
Mars VIR LIB SCO OPH SCO LIB LIB SCO OPH SGR CAP AQR
Jupiter LEO LEO LEO LEO LEO LEO LEO VIR VIR VIR VIR VIR
Saturn OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH
                         
2017 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus AQR PSC PSC PSC PSC ARI TAU GEM LEO VIR LIB OPH
Mars AQR PSC ARI TAU TAU GEM GEM CNC LEO VIR VIR VIR
Jupiter VIR VIR VIR VIR VIR VIR VIR VIR VIR VIR LIB LIB
Saturn OPH OPH SGR SGR SGR OPH OPH OPH OPH OPH OPH SGR
                         
2018 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR AQR PSC ARI TAU CNC LEO VIR VIR VIR VIR LIB
Mars LIB OPH SGR SGR CAP CAP CAP CAP CAP CAP AQR AQR
Jupiter LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB OPH
Saturn SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR
                         
2019 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus OPH SGR CAP AQR PSC TAU GEM LEO VIR LIB OPH SGR
Mars PSC ARI ARI TAU TAU GEM CNC LEO LEO VIR VIR LIB
Jupiter OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH SGR
Saturn SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR
                         
2020 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus AQR PSC ARI TAU TAU TAU TAU GEM CNC LEO VIR LIB
Mars OPH SGR SGR CAP AQR AQR CET PSC PSC PSC PSC PSC
Jupiter SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR
Saturn SGR SGR SGR CAP CAP CAP SGR SGR SGR SGR SGR SGR
                         
2021 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR CAP AQR ARI TAU GEM LEO VIR VIR OPH SGR SGR
Mars ARI ARI TAU TAU GEM CNC LEO LEO VIR VIR LIB SCO
Jupiter CAP CAP CAP CAP AQR AQR AQR AQR CAP CAP CAP AQR
Saturn CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP
                         
2022 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR SGR CAP AQR PSC ARI TAU CNC LEO VIR LIB SGR
Mars OPH SGR CAP AQR AQR PSC ARI TAU TAU TAU TAU TAU
Jupiter AQR AQR AQR PSC PSC PSC CET CET PSC PSC PSC PSC
Saturn CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP

 

Constellation Maps

 
AQR- Aquarius ARI – Aries CAP – Capricornus
CET – Cetus CNC – Cancer GEM – Gemini
LEO – Leo LIB – Libra OPH – Ophiuchus
PSC – Pisces SCO – Scorpius SGR – Sagittarius
TAU – Taurus VIR – Virgo  
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Observing Tips for Beginners

 

Amateur AstronomersAmateur astronomers have to face some challenges with equipment, weather and environment during their stargazing sessions. The tips listed below help to overcome some initial hurdles and make the celestial night show even more exciting. If you have further tips, please contact us. We will be glad to share them with our fellow amateur astronomers.

Finder Alignment

Some telescopes come with finderscope others with red dot finder. Either way, the finders need to be perfectly aligned with the telescope axis. Alignment can be carried out during the day. Point your telescope at a stationary object far away. A chimney, an antenna mast or a mountain peak will serve well. Move the telescope so that the object is exactly in the middle of the eyepiece view. Lock the telescope in that position: Re-check if the object is still in the middle of the view. A adjust the finderscope / red-dot-finder by turning the adjustment screws so that the cross hair / red dot is exactly on the object. Do not compromise. Time spent for propper aligning means less time searching objects and more time observing fascinating objects.

Finding Objects with Finderscope / Red Dot Finder

I look for objects with both eyes open, one directly aimed at the object, the other through the finder. One has to get used to this way but once acquainted with it, objects are found much easier. Using the finder view with two eyes provides not only a small cutout of the sky but you can see a large part of it.

Magnification

Most telescopes come with one or two eyepieces. If you have more than one, start your search for objects always with your lowest magnification (the eyepiece with the largest focal length). The longer the EP focal length, the wider the field of view and the easier it is finding objects. Once the object is centered in the eyepiece, you can increase magnification with shorter focal length eyepieces.

Stay Warm

Besides setting the equipment up, stargazing is really not a very physical activity. Due to the excitement about celestial objects it is ofter forgotten that our body can loose temperature – quite quickly that is. Make sure to wear sufficient layers of clothes to keep you comfortably warm. The winter, nights in the desert or at high altitude remind us permanently to stay warm, but it can become very cold during a night after a nice, warm day in Spring or Fall. Check the weather forecast for the night. Take particularly windchill factors in account and dress accordingly.

Dew

How does dew form? The dew point is the point at which the air is saturated with water vapor. Warmer air is able to absorb more water vapor than colder air. If the air it cools down, excess water vapor has to go somewhere. On a greater scale, it will rain, on a smaller scale, exposed objects get wet.  Whenever air cools down our equipment cools down as well and the exposed surfaces radiate excess heat. As this happen, moisture condenses at a greater rate than that at which it can evaporate, resulting in the formation of water droplets.

Moist lenses disturb the view significantly. Because they have their mirror deep down in the tube, Newtonian telescopes are relatively save, but all other types of telescopes, including binoculars are unfortunately susceptible to dew. A simple but a little bit cumbersome trick is to point the telescope downwards between observing sessions. When pointing it down, it is more difficult for the radiated heat to escape, and lenses will keep their temperature longer; and with that, they stay longer moist free.

Another defense against dew are large(r) dew shields. Most telescopes come with some dew protection but these shields are often far to small. Larger dew caps are available for every telescope but they can be be made easily with readily available material. Dew shields delay dewing, unfortunately, they cannot prevent it completely.

When the telescope gets moist, take utmost care when de-fogging the lenses. Best is not to touch the lenses at all, especially when they are coated. A fan is often the preferred option. If you have to use a cloth, take a very soft one. Do not rub, only dab the lens to make sure the lens coating is not damaged during cleaning.

Heating telescopes with special telescope heating bands is most convenient. These dew heaters keep the telescope just a bit warmer than the air temperature and with that, preventing dewing and moist surfaces. Heating bands need however a 12 V power source, and they can draw quite some current.

If you bring telescopes from the cold into the warm, lenses will moist almost immediately. Do not put the protection caps on right away, wait until the lenses are completely moist free.

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Mars Express – Scientific Highlights

Mars Express - Credit: ESA/Medialab
Mars Express - Credit: ESA/Medialab

The following DLR article talks about measurements and scientific experiments performed by Mars Express mission.

By: DLR

This success story began eight years ago, with the launch of a Soyuz carrier rocket from the Baikonur Cosmodrome in Kazakhstan that sent the Mars Express spacecraft on its journey to our planetary neighbour. Since then, a wealth of information about Mars, its surface, subsurface and atmosphere has led to a completely new view of the Red Planet.

The Infrared Mineralogical Mapping Spectrometer (OMEGA) has identified phyllosilicates (sheet silicates) on the surface of Mars. Such minerals are rich in iron and aluminium and arise as a result of the prolonged effect of water on volcanic rock. This discovery has led to a new view of the history of Mars; in its early days, at least, vast amounts of liquid water shaped its surface.

Water ice in the northern polar region of Mars - perspective colour view. Credit: ESA/DLR/FU Berlin (G. Neukum).
Water ice in the northern polar region of Mars – perspective colour view. Credit: ESA/DLR/FU Berlin (G. Neukum).

Using images from the High Resolution Stereo Camera (HRSC) operated by DLR, the HRSC team has determined that volcanism on Mars lasted for a long period of time, until the most recent geological past. Consequently the youngest lava concretions in the summit caldera of Olympus Mons are just 100 million years old. In fact, there may still be residual activity here and at a few volcanoes near the North Pole. Data obtained with the Planetary Fourier Spectrometer (PFS) also indicates that short-lived methane gas has been discovered and its concentrations mapped in the Martian atmosphere above volcanic regions. This leads to the assumption that Mars may still be geologically active today, as the methane might be generated and introduced into the atmosphere by volcanic activity present underneath the surface of Mars.

On HRSC images of areas at low to mid-latitudes – close to the equator – surface features that can only have occurred as a result of the action of glacial ice are recognisable. Evidence indicates three episodes of activity in the last 300 million years, the most recent of which may have taken place just four million years ago. An ice age at mid-latitudes is impossible in today’s climatic conditions. Hence scientists presume that dramatic climatic changes must have occurred on Mars, since the inclination of Mars’ rotational axis has undergone major fluctuations. This means that different climatic conditions might have been predominant at the equator and in other regions of Mars at other times.

Mars: A dry, rocky river bed, in the shape of a narrow channel, lying in a larger valley in the Libya Montes highland region. The elevation is exaggerated by a factor of three (view looking northeast).
Mars: A dry, rocky river bed. Credit: SA/DLR/FU Berlin (G. Neukum).

Data from the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) radar sounder shows that layered sediments at the Martian North Pole consist of almost pure water ice. Meanwhile the OMEGA spectrometer has produced maps of water and methane ice deposits. Observations by Mars Express have proven that much more water exists beneath the surface of Mars in the form of ice, as was anticipated ten years ago.

The data obtained with ASPERA (Energetic Neutral Atoms Analyser) show that the solar wind penetrates deeper into the Martian atmosphere than was previously assumed (down to 250 kilometres). The loss of energetic ions as a result of this is relatively low. The loss of atmospheric constituents occurs in episodic ‘outbursts’, the cause of which is not yet understood. In the absence of a magnetic field, protons and helium ions in the solar wind penetrate the Martian ionosphere to a depth of 270 kilometres and cause planetary oxygen ions to be accelerated by the energy-rich particles and flow outwards. This occurs at lower altitudes and also with greater efficiency than was previously thought.

For the first time, clouds of methane ice have been discovered, investigated and imaged in the Martian mesosphere using the HRSC, OMEGA, PFS (Planetary Fourier Spectrometer) and SPICAM (Ultraviolet and Infrared Atmospheric Spectrometer) instruments.

The mission has also yielded a wealth of research results; particularly concerning the Martian moon Phobos. These results include the most accurate determination of its mass, its exact path and its volume and density, as well as the discovery of backscattered solar wind protons by the ASPERA instrument. Furthermore, the sharpest images to date of this moon have been captured, with a resolution of 4 metres per pixel. Among other things, these seem to confirm that Phobos is orbiting Mars faster and faster and is slowly getting closer to the planet, before it potentially breaks up as a result of tidal forces in 10-20 million years, colliding with Mars.

Credit: SA/DLR/FU Berlin (G. Neukum).
Source URL: http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10463/701_read-882/

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Astro-Imaging for $100

Astrophotography on a Budget - Orion Image captured with Canon SX120 (10 exposures, 4 seconds each, ISO400)
Constellation Orion - Image captured with Canon SX120 (10 exposures, 4 seconds each, ISO400)

Is is possible to make astro-images with entry level digital point-and-shoot cameras?

The answer to that question is a reluctant “somewhat”. With a basic camera it is indeed possible to shoot decent astro-images but the objects are rather limited: the moon and star constellations. 

It is not about pixels

Basic astrophotography is not about Mega-pixels. Good images can be taken with cameras of 4 MP, or even less.  What is important are three vital camera features, without them astrophotography will become a gamble. These features are:

  • Manual focus
  • Capability to preset exposure time (Tv)
  • Capability to delay exposures. 

Another component is of great importance: a solid tripod. The magic word here is “solid”.

Manual Focus

Manual focus is important because of the way cameras perform auto focus. Some compare contrast changes. Sharp images have more pronounced contrast changes between adjacent pixels, unsharp images deliver more gradual changes. Other cameras compare bit patterns in specials sensors (phase detection). The patterns are shifted when the image is out of focus.

Either way, both methods are not really helpful when imaging a quasi black dark sky. Furthermore, if there is any contour visible in the image (f.e. a tree in the foreground), automatic focus will jump right at it, putting the  actual celestial object out of focus. Astrophotography objects need to be focused manually to infinite.

Manual Time Setting (Tv)

Moon
Moon – Image taken with Canon SX120, post-processed with GIMP

Time setting is important because the amount of light gathered by the CCD is only a tiny fragment compared to that of daylight images. This means, the exposure time need to be long. Typical exposure times for imaging stars are between 1 second and 30 seconds.

Tripod – Solid

A solid tripod will keep the exposing camera steady in position. With long exposure images, any vibration will be clearly visible in the images. The camera has to be absolutely still.  For noise reduction purposes we need to take a series of at least 10 images, ideally 30-50. More on this subject later.

Exposure Delay

Even if the camera is firmly mounted on a tripod, pushing the exposure button will cause slight vibrations. The result is star streaks in the image. Exposure delay prevents this effects. Many cameras have a built in 2 seconds or 10 seconds delay. When the button is pushed, there are still initial vibrations, but the delay allows mount and camera to stabilize. The result will be significantly sharper images.

Zoom – Better Not

Some cameras have a zoom feature. Unless you are shooting the relatively bright moon with a very short exposure time – just forget the zoom feature of the camera. Why? Because the Earth rotates. This will show badly in the images in form of elongated stars. Please try to follow the short calculation below – it is indeed eyeopening.

The earth rotates once in 24hours, one rotation equals 360 degrees. That means, in one hour the rotation angle is 360/24=15 degrees, and in one minute it is 15/60 = 0.25 degrees, right?  A quarter of a degree does not sound a lot.

True, but… Lets say we want to expose a the constellation Orion for 12 seconds. The angle the earth moves during this period is 0.25/5=0.05 degrees. A 10x zoom would increase the apparent angle by the same factor of 10. Within 12 seconds the image would shift by 0.5 degree.

One might think, that still seems negligible. Does it really have an effect?  – Yes it does, and very much so. Picture the moon. The angle of the moon is, well, 0.5 degrees. That’s right, within 12 seconds exposure using 10x zoom, stars in our image would become as long as the diameter of the moon is; definitely not what we are looking for.

So, how are images with a high power telescopes possible?

Astrophotography with high power telescopes requires special mounts; they are called German Equatorial Mounts (GEM). These mounts have gear and electronically controlled motors that move the telescope exactly so that it perfectly compensates for the Earth’s rotation.  You have probably guessed it: these mounts are rather expensive. Price depends on their carrying capability and accuracy. Entry level models that can be used for basic astrophotography start at about $500  ($300 used), and with growing demands, mounts can reach quickly true astronomical prices.  

First Photos

Preparations:

  • Make sure the battery is fully charged and the memory card offers enough space.
  • Reduce the brightness of the camera display to minimum. This helps to keep / maintain the night vision.
  • Mount the camera on the tripod.

 Shooting:

  • Choose your object
  • If possible set your camera to the highest ISO speed.
  • Manually focus to infinity.
  • Set exposure delay to 2 (or more) seconds.
  • Set exposure time (Tv) to 5 sec.
  • Take your first test shot. You can see if the object is framed right and the image is in focus.
  • You might need to play with ISO speed and exposure time to optimize image exposure.
  • Once done and you are satisfied, take a series of at least 10 images of your object (recommended 30-50). 

Note: photos of stars look always quite dark in the camera monitor. It is often advised to increase the brightness of the image later during post processing.  

Post processing (very basic):

This following description is for images with stars (not applicable for moon shots).

  • Load your images to your computer and inspect every single image
  • Sort out wiggly images, and such that have unwanted artifacts like plane or satellite trails
  • Stack the remaining images with DeepSkyStacker (DSS) – setting: average
  • Once DSS has created an image, optimize it with the build-in post processing tool

The advantage of stacking a series of astro-images (rather than using just one image), is that the noise portion will be significantly reduced, and the lunimance and saturation of the actual objects (stars) are emphasized. Since we are working usually with high ISO speeds, noise is much more present in astro-images than it is in daylight images.  

Further reading

  • Catching the Light – Great site on Astrophotography with a DLSR by Jerry Lodriguss. Noise reduction in astronomy images

Coming soon:

  • Deep Sky Stacker tutorial
  • GIMP tutorial
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Solar Dynamics Observatory

Solar Dynamics Observatory 2015-08-04T23:55:03Z
Observatory: SDO
Instrument: AIA
Detector: AIA
Measurement: 171

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