The Telescope

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

 

 

 

 

Constellations of the month

 

 
CURRENT MOON

Saturn

Saturn, now well into its new apparition, rises at around 2:15 am at the start of the month and just after 1 am at its end. With an angular size of ~16.7 arc seconds (increasing to 17.5 during the month) it climbs higher before dawn and so becomes easier to spot as the month progresses. Its brightness increases from +0.5 to +0.4 magnitudes during the month. The rings were at their widest a few months ago and are still, at 26 degrees to the line of sight, well open and spanning ~2.5 times the size of Saturn's globe. Saturn, lying in Sagittarius, is close to the topmost star of the 'teapot'. Sadly, even when at opposition later in the year it will only reach an elevation of just over 15 degrees above the horizon when crossing the meridian. Atmospheric dispersion will thus greatly hinder our view and, as for Jupiter, it might be worth considering purchasing the ZWO Atmospheric Dispersion Corrector to counteract its effects.

Jupiter

Jupiter rises in the east-southeast about three hours after sunset at the beginning of the month and about two hour earlier by month's end. Initially it has a 42.6 arc second disk, shining at a magnitude of -2.4 but, as the month progresses, its apparent diameter increases to 44.6 arc seconds and it brightens to magnitude -2.5. Jupiter will transit before around 3:30 BST in early April and by around 1:30 BST at its end and so will enable the giant planet to be well seen with the equatorial bands, sometimes the Great (but reducing in size) Red Spot and up to four of its Gallilean moons visible in a small telescope. Jupiter will reach opposition on the night of May 8-9th. Sadly, lying in Libra during the month, Jupiter is heading towards the southern part of the ecliptic and will only have an elevation of ~20 degrees when crossing the meridian. Atmospheric dispersion will thus hinder our view and it might be worth considering purchasing the ZWO Atmospheric Dispersion Corrector to counteract its effects.

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Mars

Mars starts the month in Sagittarius close to the topmost star of the 'teapot' close to Saturn. Now a morning object, it rises at around 2 am BST at the start of the month. During the month, Mars has a magnitude which increases from +0.3 to -0.3 and an angular size of 8.4 increasing to 11 arc seconds so, by month's end it should be possible to spot details on its salmon-pink surface. It will only reach an elevation of ~12 degrees before dawn at the start of the month and just 11 degrees by month's end. Sadly, the atmosphere will hinder our view. Another reason for purchasing a ZWO Atmospheric Dispersion corrector?
Venus

Venus, seen low in the west after sunset, shines at magnitude -3.9 all month with an angular size of ~10.6 increasing to 11.5 arc seconds. Venus rises a little higher in the sky as April progresses, initially setting around one hour and a half after the Sun but increasing to two hours by month's end as its elevation at sunset increases from 18 to 25 degrees - so by month's end it will become quite prominent in the evening sky. Venus starts the month in Aries but, moving higher in declination, passes into Taurus on the 20th before passing between the Hyades and Pleiades Clusters on the 27th.

Mercury

Mercury passes in front of the Sun (inferior conjunction) on April 1st and, rising out of the Sun's glare, reaches greatest western elongation of 27 degrees on April 29th. But, due to the fact that the ecliptic makes a shallow angle to the horizon at this time of the year, it never gets more than 10 degrees above the horizon even when furthest in angle from the Sun. Not one of its better apparitions.

The Night Sky In and Around Swindon April 2018

Slide Presentation

The following presentation was given at our meeting on the 17th November, 2017 by Rob Slack

The constellation of Gemini

Gemini - The Twins - lies up and to the left of Orion and is in the south-west during early evenings this month. It contains two bright stars Castor and Pollux of 1.9 and 1.1 magnitudes respectivly. Castor is a close double having a separation of ~ 3.6 arc seconds making it a fine test of the quality of a small telescope - providing the atmospheric seeing is good! In fact the Castor system has 6 stars - each of the two seen in the telescope is a double star, and there is a third, 9th magnitude, companion star 73 arcseconds away which is alos a double star! Pollux is a red giant star of spectral class K0. The planet Pluto was discovered close to delta Geminorum by Clyde Tombaugh in 1930. The variable star shown to the lower right of delta Geminorum is a Cepheid variable, changing its brightness from 3.6 to 4.2 magnitudes with a period of 10.15 days


M35 and NGC 2158

This wonderful image was taken by Fritz Benedict and David Chappell using a 30" telescope at McDonal Observatory. Randy Whited combined the three colour CCD images to make the picture

M35 is an open star cluster comprising several hundred stars around a hundred of which are brighter than magnitude 13 and so will be seen under dark skies with a relativly small telescope. It is easily spotted with binoculars close to the "foot" of the upper right twin. A small telescope at low power using a wide field eyepiece will show it at its best. Those using larger telescopes - say 8 to 10 inches - will spot a smaller compact cluster NGC 2158 close by. NGC 2158 is four times more distant that M35 and ten times older, so the hotter blue stars will have reached the end of their lives leaving only the longer-lived yellow stars like our Sun to dominate its light.



The Eskimo Nebula, NGC2392, Hubble Space Telescope
To the lower right of the constellation lies the Planetary Nebula NGC2392. As the Hubble Space Telescope image shows, it resembles a head surrounded by the fur collar of a parka hood - hence its other name The Eskimo Nebula. The white dwarf remnant is seen at the centre of the "head". The Nebula was discovered by William Herschel in 1787. It lies about 5000 light years away from us.
The constellation Virgo

Virgo, rising in the east in late evening this month, is not one of the most prominent constellations, containing only one bright star, Spica, but is one of the largest and is very rewarding for those with "rich field" telescopes capable of seeing the many galaxies that lie within its boundaries. Spica is, in fact, an exceedingly close double star with the two B type stars orbiting each other every 4 days. Their total luminosity is 2000 times that of our Sun. In the upper right hand quadrant of Virgo lies the centre of the Virgo Cluster of galaxies. There are 13 galaxies in the Messier catalogue in this region, all of which can be seen with a small telescope. The brightest is the giant elliptical galaxy, M87, with a jet extending from its centre where there is almost certainly a massive black hole into which dust and gas are falling. This releases great amounts of energy which powers particles to reach speeds close to the speed of light forming the jet we see. M87 is also called VIRGO A as it is a very strong radio source.


The Giant Elliptical Galaxy M87
Below Porrima and to the right of Spica lies M104, an 8th magnitude spiral galaxy about 30 million light years away from us. Its spiral arms are edge on to us so in a small telescope it appears as an elliptical galaxy. It is also known as the Sombrero Galaxy as it looks like a wide brimmed hat in long exposure photographs.


M104 - The Sombrero Galaxy

A Single Imager's Lunar Image

The 8 day old Moon imaged by Ian Morison
April 7th before dawn: Saturn, Mars and a third-quarter Moon

Saturn amd Mars below a waning Moon

If clear before dawn on the 7th, looking just east of south, one should see a waning third-quater Moon lying to the upper left of Saturn and Mars.

Compiled by Ian Morison - Jodrell Bank Centre for Astrophysics
22nd April - early morning: The peak of the Lyrid Meteors

The Lyrid Meteor Shower
Image: Stellarium/IM

After the Moon has set,and so with no moonlight to hinder our view and from a dark rural location one, if clear, would have a chance of observing the peak of the Lyrid meteor shower with up to 10 meteors visible each hour. As one might expect, the shower's radient is close to Vega in Lyra. One might also spot them on the 21st and 23rd.

The planets this month
This image was taken by the author on a night in March 2018 when the Moon was at an elevation of ~52 degrees and the seeing was excellent. This enabled the resolution of the image to be largely determined by the 200 mm aperture telescope and the 3.75 micron pixel size of the Point Grey Chameleon 1.3 megapixel video camera. The use of a near infrared filter allowed imaging to take place before it was dark and also reduced the effects of atmospheric turbulence. Around 60 gigabytes of data, acquired over a 2 hour period, was processed to produce images of 30 overlapping areas of the Moon which were then combined to give the full lunar disk in the free 'stitching' program Microsoft ICE. The Moon's disk is ~5,000 pixels in height. Interestingly, as seen in the inset image, the rille lying along the centre of the Alpine Valley is just discernable and this is only ~0.5 km wide! Due to the time taken to acquire the video sequences, it is unlikely that a single imager (as opposed to the 10 who acquired the World Lunar Record image) could obtain a significantly higher resolution full disk image in a single night.
The constellation Leo
The constellation Leo is now in the south-eastern sky in the evening. One of the few constellations that genuinely resembles its name, it looks likes one of the Lions in Trafalger Square, with its main and head forming an arc (called the Sickle) to the upper right, with Regulus in the position of its right knee. Regulus is a blue-white star, five times bigger than the sun at a distance of 90 light years. It shines at magnitude 1.4. Algieba, which forms the base of the neck, is the second brightest star in Leo at magnitude 1.9. With a telescope it resolves into one of the most magnificent double stars in the sky - a pair of golden yellow stars! They orbit their common centre of gravity every 600 years. This lovely pair of orange giants are 170 light years away.

Leo also hosts two pairs of Messier galaxies which lie beneath its belly. The first pair lie about 9 degrees to the west of Regulus and comprise M95 (to the east) and M96. They are almost exactly at the same declination as Regulus so, using an equatorial mount, centre on Regulus, lock the declination axis and sweep towards the west 9 degrees. The other pair is M65 and M66.


M95 and M96