Old cooke


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Old cooke

  1. 1. Old Cooke; new perspectives OLD COOKE; NEW PERSPECTIVES Can a make of refractor over 150 years old rival the quality of modern optics? Neil English looks at the experience of a number of accomplished astronomers to discover the legacy of the Cooke refractors,,,[To] our English Fraunhofer. .. whose science and skill We shall begin with the Reverend eight-inch (203mm) Cooke (that later had restored to England the pre-eminent position she William Rutter Dawes (1799-1868), became known as the Thorrowgood),held a century ago in the time of Dollond." revered among double star observers usually with a magnifYing power of So wrote the mystery obituarist in 1868 concerning for bringing us his empirical formula 258x. His drawings, wrote Richardthe legacy of Thomas Cooke, master optician and used to work out the minimum Anthony Proctor, "are far betterfounder ofT Cooke and Sons of York. It was a fitting aperture needed to resolve double stars than any others ... the views by Beeraccolade for a self-made Yorkshireman who had of a given angular separation. What is and Miidler are good, as are some ofre-established the prestige of Britain as great telescope less well known is that the Reverend Secchis (though they appear badlybuilders throughout the Victorian era and beyond. From was also a first rate planetary observer, drawn). Nasmyths and Phillips, Dehumble origins and with little formal training, Cooke apparently possessing extraordinary La Rues two views are also admirable;went on to build some of the frnest telescopes of his visual acuity. And he had an interesting and Lockyer has given a better set ofgeneration, including tlle giant 25-inch (635mm) Newall purchasing history, having used views than any of the others. But thererefractor, which briefly enjoyed the distinction of being refractors crafted by Dollond, Merz is an amount of detail in Mr Dawesthe largest instrun1ent of its kind in the world. and MaJUer, Cooke and even the views which renders them superior to Having had the pleasure of looking through a few shining light of An1erican optics, any yet taken." Camille FlammarionCooke refractors ranging in size from four inches (102mm) tile portrait painter turned telescope concurred: "The drawings by ...up to ten inches (254mm), the images they served up never maker, Alvan Clark. Dawes brought a new precision tofailed to impress me. But were my views of the Cooke Yet, in the autumn of his life, old studies of Mars."refractors coloured or even representative of what other Eagle Eyes returned to a Cookeobservers have found? Curious to find out, I first explored refractor. Dawes had already made Red star delightsome of the comments of historical observers who had used some drawings of Mars in 1862 and at Across the Irish Sea, at a beautiful,Cooke refractors during the course of their careers. earlier oppositions. In 1864, he used an windswept rural estate near Milltown,341 Astronomy Now I July 2011
  2. 2. Old Cooke; new perspectives six-inch telescope, and for many eight inches seems to be the smallest aperture theyd be happy with. The Encke division (marking) is typically regarded today as a good target for a ten-inch instrument (for the record, Ive personally not seen it). So, was it the fme optics Raman had in his five-inch Cooke, or exceptional eyes, or both? I guess well never know for sure! We return, once again, to England and to the fondly remembered British actor and comedian WIll Hay (1888-1949). Though playing the consun1mate idiot on stage, behind the scenes Hay was a gentleman of encyclopaedic knowledge, with a predilection for astronomical adventure. He set up a fine six-inch Cooke refractor in a private observatory established at his home in Norbury, London, to study the planets. On the faithful night of 3 August 1933, Hay used this instrument and an eyepiece delivering a power of 175 x to detect a prominent white spot on Saturn. The spot, located in the planets equatorial zone, remained prominent for a few days before mysteriously fading away. Although similar phenomena were recorded by earlier observers (Asaph Hall in 1877 and E E Barnard in 1903), Hay is credited with the official discovery. Curiously, Hays beloved six-inch Cooke, like the spot he discovered, inexplicably disappeared after his death and, despite diligent attempts to locate .it, we are still 11I[i. none the wiser concerning its current whereabouts! ~: Modern perceptions How did these refractors of old settle with folk who have had the pleasure of using them over years and decades? First, I contacted Douglas Daniels, President of the Hampstead Scientific Society, England, who has had the iinmense good fortune of using the observatorys six-inch £l5 Cooke since 1967. Doug spoke to me about his background and how he became acquainted with Cooke refractors. "I have always been a keen lunar and planetary observer and telescope maker since I first became seduced by astronomy at the age of 13 in 1953," he says. "I joined County Galway, John Birmingham (1814-1884) made ... A portable four- the British Astronomical Association [BAA] in 1956,use of a 4.5 -inch (114mm) Cooke refractor to embark inch (102mm) fl15 which was the year of a very close opposition of Mars.on a special study of red stars, in which he wished to Cooke refractor. circa 1860, fixed At that time, I had built a six-inch Newtonian reflectorundertake a revision and extension of the best resource onto an original using a mirror made by the late Henry Wildey. I was q.,uiteof its day on such objects, Hans Schjellerups Catalogue Cooke mount. impressed by the performance of this instrument, both onof Red Stars. In all, he included 658 such objects. This Image: Richard Day. Mars and Jupiter, but I was soon to meet another youngwork was presented to the Royal Irish Academy in 1876 BAA member - Terry Pearce. Terry and I became goodand its merit was acknowledged by the award of the friends (and still are!). Terry had managed to borrow aCunningham MedaL In 1881 Birmingham discovered 4.5-inch Cooke from the BAA and had set it up in hisa deep red star in Cygnus, which is named after him. garden at Chingford in Essex. I was amazed at the sheerHe published articles on the transit of Venus and size of it. It was on the usual Cooke, two-part cast ironsunspot morphology made with the same telescope, column and the equatorial mOlUlt was massive for ancorresponding regularly with the leading astronomers of instrument of that size. But I was even more amazed whenhis day. A lunar crater is named in his honour too. I looked through it. The detail on both Mars and Jupiter Moving next to the Far East, to Bankura in India, was astounding - far more contrast than with my six-inchChandrasekhar Venkata Raman (subsequently knighted), reflector. That was my first taste of a Cooke."the recipient of the 1930 Nobel Prize in Physics for hiscontributions to optical science, was fond of using a five-inch(l27mm) Cooke refractor. I came across one curious account "AMATEURS HAVE BECOME SOMEWHATRaman made whilst using this telescope to observe Saturn: OBSESSED WITH OPTICAL QUALITY AND " ... not only was the Crepe ring an easy object," he BENCH TESTING, YET THESE ANTIQUATEDsays, "But for nearly one hour while tl1e definition wasperfect, I made out Enckes marking in the A-ring and TELESCOPES CLEARLY HAVE THE POWER TOheld it steadily for practically the whole period." DELIVER THE READIES" Now the Crepe ring is quite a difficult target for a
  3. 3. --- _- _- _- .._-- _- _-- _- _- _- _- - _-- - I asked Doug how and when he first became acquainted with the Hampstead six-inch Cooke. "In 1967 I joined the Hampstead Scientific Society and was able to use the six-inch Cooke at the Hampstead Observatory," he says. "Again, 1967 was a year with a good opposition of Mars, and the detail observed with the Cooke was so good that I began to attempt photography. I built a special planetary camera with a flip mirror system to keep the planet under close surveillance waiting for clear moments to make exposures - it was a sort of single lens reflex job but without the lens! [remember, this was 1967!]. My photographs came to the attention of an American student called Ron Wells, who was doing a PhD on Martian topography at University College London. Ron was working at the University of London Observatory at Mill Hill - just 15 minutes from my-home. I was introduced to the Director, Professor Allen, and was allowed to use the 18-inch (457mm) Grubb - I had the key to the big dome for six months. On the same site, there were two smaller domes. One contained the Fry Telescope - an eight-inch Cooke. Once again the Cooke was the instrument that impressed most. On most nights of average seeing, it could easily outperform the 18-inch• Some of Doug Daniels Grubb. Only when the seeing was excellent could therecorded detail of the Martian Grubb show slightly more detail."opposition of 1967. Image: Doug was more than happy to recount theDoug Daniels. telescopes long history. "The Cooke was once owned by a member called George Avenell," Doug says. "We know that it was in use at the observatory in 1923. It was finally presented to the society in 1928. Prior to this we have no information. The optical tube appears to have been manufactured around 1900, but we have no hard evidence for this date. When I began using it in 1967, it was mounted on an old Cooke equatorial from a 4.5-inch instrument that was too small. It had the old Cooke falling weight drive and a worm sector, not a complete wheel that was always getting jammed. In the end we built our own heavy-duty mount in 1976, driven by a stepper motor. A couple of years ago, I was in correspondence with Martin Mobberley, who was researching the six-inch Cooke once owned by Will !l./.ool.., Hay. I was able to confirm that the Hampstead Cooke -;,.J.. O·Q ,.,._ ~ )( 3 was not Hays instrument." F.P. 3 e~E.t Sec.. What about the telescopes maintenance? Is it, in ".."..J~ ~o "";"s ....Q fI>du",. any sense, fastidious in its requirements? "Not at all," says Doug. "The objective is best left well alone. It gets an annual wipe over with meths and a lint free cloth and every few years is checked for squaring on, which hardly lS/4/Q needs any adjustment for long time periods. Thats t>1I.""<j .. pl,()fO<j"fh another nice aspect of refractors - they are virtually t4..... S<......... Q4Si.", maintenance free, unlike reflectors which are constantly ~h." 0 .... ~1.1<:l going out of square and need re-coating every few years." ~~ "l.J. IS· "~I() b...J.O.q.. Ph"" t 10<. ." fP· -S f.I~l A new eye on an old telescope ~cN"" l5-~~ De ... fl!Q Next I canvassed the opinion of Dr Richard McKim, Director of the Mars Section of the BAA, who has used Cooke refractors in his extensive studies of the red planet over the last few decades. "I have used many refractors on a regular basis since the 1970s," explains McKim. "The problem is, I have no basis of comparison with other makes. Until 1988, the Northumberland ..................................... - - - -- - ..-..--- ..- - - - ~