A Brief History of the Jack Ells APT. Presentation by Keith Rickard 16 May 2013

Transcription

1 A Brief History of the Jack Ells APT Presentation by Keith Rickard 16 May 2013

2 Inception Photometry was a big subject of discussion in the 1980s CMHAS had an active interest in photometry amongst its members, namely Roger Pickard, Dick Chambers and Jack Ells with his son Peter This was demonstrated by the output of its members Roger Pickard wrote a paper for the BAA journal Getting started in photoelectric photometry in 1986 Peter Ells wrote a paper for the BAA journal titled A microcomputerassisted photoelectric system in 1986

3 Inception Dick Chambers was first to suggest that a meeting should be held to discuss the subject and employed his organisational skills to a strong group of variable star observers On 27 April 1985, a Photoelectric Photometry Meeting was held at CMHAS following a meeting of the 3rd European IAPPP Symposium at Herstmonceux in September 1984

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6 Inception Dick Chambers was first to suggest that a meeting should be held to discuss the subject and employed his organisational skills to a strong group of variable star observers On 27 April 1985, a Photoelectric Photometry Meeting was held at CMHAS following a meeting of the 3rd European IAPPP Symposium at Herstmonceux in September 1984 On 24 October 1987, CMHAS held a teach-in meeting at the Crayford Manor House. This was reported in the FAS newsletter of April 1998

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9 Participants of the teach-in at Crayford Manor House A.S.

10 Roger Pickard s report of the meeting

11 Inception Roger Pickard s PEP paper (JBAA 1986, 97,1) discussed the pros and cons of photometry when manually operating a photometer.

12 Inception Jack Ells s photomultiplier head

13 Inception A typical photoelectric tube

14 Inception Using a photometer Pros: Very sensitive sometimes less that 0.01 magnitude can be recorded More objective visual observing can be very subjective Fainter magnitudes can be detected Can be used with different wavelengths of light using UBV filters (Ultraviolet, Blue and Visual) though filters not required for eclipsing binaries as it is their period that is important

15 Inception Using a photometer Cons: Slower to get readings than doing it visually The photometer requires around 1000V at the telescope The unit is very heavy a substantial mount which can hold the starlight in the diaphragm pin-hole for a least a minute is required A lot of tedious pointing is required to get a reading, e.g. Roger suggests that the sequence for a single observation is to point to and read the brightness of: Sky, Comparison, Variable, Comparison, Sky, Variable, Check, Sky Data reduction is required after the observation to get a meaningful result Observing set-up can take about 30 minutes Cost (in 1986, at least 250).

16 Inception There had to be a better way. Jack and Peter Ells developed a computer assisted solution using a 320mm Newtonian reflector, and a BBC microcomputer connected to a photometer head and a remote button box - first light 29 Sept (per paper by Peter Ells in JBAA 1986, 96, 4) The user points the telescope at each star and then users the button box to tell the computer - what is being observed (variable, check or comparison stars of sky) - which filter is being used - when to start integration - whether to accept the reading The computer can then process the results and output the data in a table or light curve graph.

17 Inception At the end of a observing session, the observer could easily obtain a several hundred readings It was still very labour intensive but the rewards must have been enough for the observer to want to carry out future sessions Very few amateurs were producing professional quality work

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20 Inception Although he was producing ground breaking amateur work, Jack must have been looking around at how else he could make the task easier From his research papers, it is clear that he was looking, with his son Peter, at other amateurs automated photoelectric telescopes, using stepper motors to drive a telescope and how to interface the telescope drive and photomultiplier tube with a BBC Micro B computer

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25 Jack Ells Automatic Photoelectric Telescope Employing his remarkable engineering skills he produced a purpose built telescope driven by a stepper motor friction drive Peter built the electronics and programmed the BBC Micro B computer Together, the APT was born 6 years after their first interest in photoelectric photometry

26 Jack Ells Automatic Photoelectric Telescope Designed and constructed principally for the observation of eclipsing binaries (faintest operable magnitude of 9.0) 212mm f4.0 Newtonian reflector Housed in a run-off shed Driven by stepper motors from a 1980s BBC micro B computer (which also captured data) to point the APT to the variable, comparison and check stars and the sky Water proof Is four times as effective as the already fast manual system Saw first light in April 1988 (25 years ago)

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29 Jack Ells APT at 7 Avenue Road, Bexleyheath

30 Jack Ells standing by his telescope He was a founder member of CMHAS and vicechairman of the society Was Probably Great Britain s leading amateur photometrist.

31 Jack Ells Automatic Photoelectric Telescope Jack and Peter produce three papers on the APT titled A simple automated photoelectric telescope part I Overview and Results (JBAA 1989, 99, 6) A simple automated photoelectric telescope part II Hardware (JBAA 1990, 100, 1) A simple automated photoelectric telescope part I Software (JBAA 1990, 100, 1)

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33 Jack Ells Automatic Photoelectric Telescope After Jack Ells s untimely death on 29 March 1990 (aged 62) it was relocated to a darker site in This was at Malcolm Gough s home in Trottiscliffe, Kent Its disposition was decided with the Ells family in constitution with the Pro-Am Liaison Committee Up to that point, the APT had performed 5,000 observations resulting in 70 timings of minima A small group of CMHAS members (Malcolm Gough, Roger Pickard and John Barry) carried on the work on the APT and he telescope resumed operations in June Requests were always welcome from both the amateur and professional community; i.e. those requiring continuous observation throughout the night, e.g. eclipsing binaries

34 Jack Ells APT at Trottiscliffe

35 Life of the APT in astronomical circles Lots of observations and references noting the APT have been published since its relocation to Trottiscliffe 19 Oct 1991: Centenary Meeting of the BAA VSS... two important UK amateur facilities were described [at the meeting]... with the Jack Ells APT being mentioned JBAA (1994, 104,3) paper: The Jack Ells Automatic Photoelectric Telescope by Roger Pickard The paper reported that in 1992 a total of 1955 observations during 52 observing runs, taking place over 44 nights on 25 stars including 20 eclipsing binaries.

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37 Life of the APT in astronomical circles JBAA (1997, 107, 6) paper: The Jack Ells APT at Trottiscliffe: Results summary by Roger Pickard (noting that most of the work had fallen on Malcolm Gough) The paper reported that from 1 Jan Dec 1995, 80 observing runs had occurred on 34 stars producing 4,389 delta magnitude estimates.

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42 Life of the APT in astronomical circles 11 April 1996: RAS NAM Discussion Meeting on Profession-Amateur Co-operation in Liverpool, Roger Pickard described the CMHAS PEP Programme which commenced on 4 Sept 1984 and described the APT. He said that...the Crayford astronomers are currently looking at rewriting the [APT] software to run on a PC... In the 1996 VSSC92 a report by Roger and Malcolm was included The Jack Ells Automatic Photoelectric Telescope Report for 1996 It was noted that John Howarth had to build a cable and write a program on the PC to import the APT data from the BBC Micro B! For 1996, there were 1528 observations over 23 observing runs on 16 stars

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44 Life of the APT in astronomical circles 30 May 1998: Meeting of the Instruments and Imaging Section Roger presented an account of the operation of the APT 31 Oct 1998: Meeting of the Variable Star Section was held at the Crayford Manor House In the Jun 1998 VSSC96 it was reported that the APT performed 1271 observations on eclipsing binaries where 5 minima timings were obtained. In the Mar 2000 VSSC103 it was reported that in 1997 the APT made 2549 observations over 34 observing runs on 16 stars

45 Recently As can be seen, the APT has been a very productive telescope and provided invaluable data About 10 years ago its liquid light guide became opaque which stopped work but the BAA provided a new one There were many electronic hardware problems since - some were overcome but for about 5-6 years no work has been undertaken due to electronics failure. It deserves a new lease of life!

46 The present

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