A little ramble through Eridanus the River

Eridanus is the 6^th largest constellation in the sky, but it is often overlooked due to the lack of bright stars. Or at least certainly from the northern hemisphere. Its brightest star Achernar is not visible from the UK. The constellations starts close to the bright star Rigel in Orion and then meanders south and below the horizon. 

To the Greeks Eridanus was sometimes called the River of Orion due its closeness to Rigel. It is often associated with the river into which Phaethon fell after trying to use the chariot of his father, the sun god. Some Greeks also just referred to it as the river.

It was also seen as a river by the Euphratean astronomers who used the name of Erib-me-gali.

Keeping up this theme of a river the Arab astronomers called this constellation Al Nahr which again means the river.

The brightest star in Eridanus is alpha or Achernar which in Arabic is Al Anir al Nahr or the End of the River. An interesting point to note is that this name was first given to the star theta. This was because it was the southernmost bright star to be seen from Greece. When European explorers travelled to the southern hemisphere, they saw a bright star that could not be seen from Europe.

In 1603 the German astronomer Johannes Bayer extended the length of Eridanus and named it Achernar the End of the river. The star theta was renamed Acamar which in Arabic means the Root.

Achernar is a B class star with a magnitude of 0.5 and is the 9th brightest star in the sky, Achernar is139 light years away. We normally think of a star as a sphere of hot spinning gas but Achernar spins so quickly that it is pushed out of shape, so it appears more like an oblate spheroid. It is quite possibly the least known spherical star in our galaxy. It is not a single star it has a companion star. Achernar is around 10 times the diameter bigger than our Sun. The average temperature is about 15,000 degrees much hotter than the Sun; however, this varies because at the poles it is 17,000 degrees while at the equator its 12,000 degrees.

Theta or Acamar has a magnitude of 2.9 and is 164 light years away. Acamar is a double star, and both stars are A class stars indicating they are hotter than our Sun.

Beta or as it is known to the Arab astronomers as Cursa which means The chair or the Footstall of the Central One is located just above the bright star Rigel in the constellation of Orion. To the Chinese this was called Yuh Tsing or The Golden well. It has a magnitude of 2.8 and is an A class star lying  90 light years away.

Gamma was known to the Arab astronomers as either Zaurac or Zaurak which means the Bright Star of the Boat. The star is a red M class giant star around 192 light years away and has a magnitude or brightness of 2.9. As it is an M class star it will be cooler than the Sun with a surface temperature of about 3,500 degrees compared to the 5,800 degrees of the Sun.

 Gamma or Azha as it was known to the Arab astronomer Al Sufi was chief among the stars of the Ostrich’s Nest which the word Azha means. Its an K class star again cooler than the Sun with a magnitude of 3.9 and is 137 light years away.

There are no bright deep sky objects to mention.

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A little ramble through 19th century astronomy - Bath Observatory destroyed by fire in 1867

 Devizes and Wiltshire Gazette Thursday 24^th January 1867.

 

 Destruction of an Observatory. 

—On Sunday last the observatory connected with St. Gregory's College, Downside, near Bath, was totally destroyed by fire. It originated apparently in the heating apparatus, which kindled the joists of the ground floor; the flames, which caught some stuffed birds and other natural history specimens in the museum kept in the lower room, were rapidly communicated to the equatorial room above, in which was a magnificent refracting telescope of 15 inches diameter and 20 feet focal length. 

The observing stages formed capital fuel for the fire, and in less than hour the whole was one mass of flame, leaving no possibility of rescuing anything. The loss of the glass and astronomical plant attached to the telescope is the more unfortunate as the observatory had only just been placed in full working order. The loss to the college of the antiquities, curiosities, and natural history collections in the museum cannot be estimated, for they contained many unique and invaluable specimens, and were the result of fifty years' accumulation.

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The Astronomy Show on Drystone Radio

 Join me, Martin Lunn MBE every Monday evening from 7.00 pm-9.00 pm on the award-winning Astronomy Show on Drystone Radio, probably the only regular astronomy show on any radio station in the country. 

I will take my weekly look at the night sky and look at all the latest news in astronomy. There will be the astronomical anniversaries this week plus the latest news from the astronomical societies in the north of England.

The Astronomy Show every Monday evening only on Drystone Radio live online at www.drystoneradio.com DAB radio in Bradford and East Lancashire, or 102 and 103.5 FM and can also be heard later on the Drystone Radio Podcast.

Cooke Telescope Tales - Mr Maw and his two Cooke telescopes

William Henry Maw (1836 – 1924) was born in Scarborough on December 6^th 1836, when he was growing up he was friends with the sons of Dr Harland, who would become the founders of the Harland & Wolf ship builders. Both his parents died when he was in his teens, without influences and an advantage of a higher education he was still able to raise himself to become a leading authority in the fields of mechanics and engineering. 

His leisure time was however devoted to astronomy. In Kensington, London in 1887 he built an observatory for his 6 inch Cooke telescope which he used to study the Moon. Later from 1897 when he lived in Surrey he built an observatory for a larger 8 inch Cooke  telescope. This had originally been owned by the Rev R W Dawes and would later be located at the Institute of Astronomy at Cambridge and known as the Thorrowgood Telescope.

 W H Maw made extensive observations of double stars using both Cooke telescopes. In particular the double stars from the Struve catalogue. His observations were considered to be very accurate. Maw was a Fellow of the Royal Astronomical Society and one of the founders of the British Astronomical Society.   

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A little ramble through 19th century astronomy - Moses Holden and the comet of 1840

  Blackburn Standard Wednesday 4^th March 1840 

 

THE COMET 

To the Editor of the Blackburn Standard.

 

 Sir, —Will you have the goodness to insert in the Standard the following account of a comet which is now seen: it is written by Mr. Moses Holden, whose lectures many of your readers will remember, and appeared in the Preston papers of last Saturday:-

 

 " A second Comet has appeared this year, although the month of February is not yet out. This second is very small, and can only be seen with a good telescope. I saw it on the 23rd, it was little above the girdle of Andromeda, and did not look half large as the Nebula in that girdle, nor half as large as Encke's Comet. Its movement for the week along the girdle of Andromeda, as it passes the stars, is as follows,

 

Feb 1840  29    28     27    26    25    24   23

                  o       o       o     o      o      o     o   Comet.

                                                           Nu*            

                   Beta *                Mu*              0 Nebula

 

An equatorial telescope turned to right ascension, in time 1 hour and 15 minutes, and declination 35 deg,  5 min., will be near the place, and with a Comet eye-piece would soon find it this evening.

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A little ramble through 19th century astronomy - temporary observatory near Sydney in 1890

 Colonies and India Wednesday 21^st May 1890 

A temporary observatory is about to be established near Sydney for the purpose of carrying on astronomic photographic work in connection with a chart of the heavens about to be prepared by an Astro-Photo Committee charged by the Conference which met in Paris in 1887. The arrangement of the details has been allotted in zones to 19 observatories in the order of their latitude. Under this arrangement Sydney takes from 34° S. to 42° S., and Melbourne from 70' S. to the South Pole. 

 

H C Russell Sydney astronomer and Sydney observatory

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A little ramble through 19th century astronomy - Repairs to the Madras Observatory in 1890

 Madras Weekly Mail Wednesday 5^th February 1890 

 

THE MADRAS OBSERVATORY

 

Mr. N. Pogson, C.L.E , Government Astronomer, in submitting an estimate of Rs. 2,772 for making certain repairs, reports an follows:

 

Herewith, I have the honor to submit, in duplicate, an estimate for necessary repairs of the Government Observatory, amounting to Rs 2,772, together with an accompanying report by H. Irwin, Esq., C.L.E the Consulting Architect to Government. The repairs have been much needed for some years past, but were deferred, as the transit circle could not then be spared without serious inconvenience. This fine instrument, which cost I, believe about £1,200, was under the very beams, the collapse of which was most imminent; so after Mr. Irwin’s  warning I lost no time in dismounting and removing the transit circle on a strong temporary wooden roller stand to a more secure part of the observatory, pending the repairs of the transit circle room. The telescope cones, bearing the eyepiece and objective, the counterpoises, damps, microscopes, &c., were all taken off on November 16th, assisted by workmen from Messrs. P. Orr and Sons; in consequence of the risk in case of heavy rain, the remainder of the instrument, weighing about 400 lb, was carefully removed bodily on Sunday, November 17th, and the building placed at the Consulting Architect's disposal for whatever emergent precautions in the way of propping and otherwise securing the roof he might consider necessary. During the repairs of the transit room the Madras mean time has to be determined by means of a small transit instrument by Dollond, formerly in use between 1858 and 1862, but with which the time in less certain within half a second than it is within half-a-tenth of a second with the transit circle. The early completion of the repairs is most desirable and advantage will be taken meanwhile for thorough cleaning up of the large instrument on the spot under my own immediate superintendence with such help as I can obtain from Messrs. P. Orr & Sons. The estimate has been sanctioned by government.

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