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! WELCOME TO THE MAS WEB SITE !
MEMBERS see General Data Protection Regulations |
Annual Photo Compitition 2019. You have to be a member to enter. Next closing date 6th May 2019. Further details in the Members section. If you have problems logging in, contact the Membership Sec. or Webmaster
Next Months Meeting |
Friday, 3rd May 2019 13 Journeys in Space and Time (Colin Stuart)
All our indoor meetings run from 7.30 to 10pm in the Church Hall, St James-the-Less, Stubbings, Maidenhead, SL6 6QW (for directions, see our About & Contact page)
Meetings are normally on the first Friday of the month, September to June. There are no indoor meetings in July or August (unless indicated)
Beginners and visitors are always welcome at our indoor meetings (you don't have to join, however a £2 contribution toward the costs of the hall hire would be most welcome !)
To contact the society between meetings, please complete the on-line General Enquiry form
If you would like to receive, by email, advanced notification of our free public events, or you would like further information about the Society please use the Enquiry form mentioned above - or just turn up at any meeting and speak to any member of the Committee.
We also have a page on the Maidenhead Arts Council web site (where you will find details of other local clubs and societies if, for some inexplicable reason, Astronomy fails to fire your imagination and seize your interest :-) )
This seasons meetings |
(download printable guide PDF )
Friday, 7th September 201813 Journeys through space and Time (Postponed new date TBA) |
Friday, 1st February 2019Ask the Expert (members panel) |
Friday, 5th October 2018The Future is out of this World ( Dr Stuart Eves FRAS) |
Friday, 1st March 2019The Extremely Large Telescope (ELT) (Dr Aprajita Verma) |
Friday, 2nd November 2018Short talks (by members) |
Friday, 5th April 2019Space Weather (Dr Colin Forsyth) |
Friday, 7th December 2018Christmas Quiz and Social ( ) |
Friday, 3rd May 201913 Journeys in Space and Time (Colin Stuart) |
Friday, 4th January 2019Equipment exhibition (and EGM) |
Friday, 7th June 2019MAS 61st AGM ( ) |
(Table: http://www.maidenhead-astro.net/public/Home/index#2_bm)
Members :- Please log-in to the Members Only section for details of our next members only Event
Next Public Event |
11 Nov 2019 Transit of Mercury (2nd of pair)
11 November 2019: Transit of Mercury, start 12:35, mid 15:19, ends 16:015 (all times for Reading)
Like Transits of Venus, these occur in pairs, this being the second of the 2016/19 pair. Although Transits of Mercury are less rare than a transit of Venus, the next Mercury pair will not be until 2032/39 (see wikipedia).
For more on this transit, visit the time and date website
This note last modified: 27th Feb 2016 11:09.
See our Events page for more information about all our Events
Click here for MAS Facebook page
Monday, 9 May 2016: Transit of Mercury, members of MAS gathered in Ockwells Park to show the Transit to the public. For more details, see report on Events page
WARNING: never look at the Sun through a normal telescope !!
Doing so, WILL BLIND YOU !!!
Most recent Event Report |
Details of all our planned and past activities can be found on the Events pages.
Note that Outreach events are not usually open to the public, so are reported here only AFTER the event (Members can see planned Outreach dates in the Members Only section, Activity planning pages)
4 Apr 2019 Newlands School (Outreach)
Thursday, 4th April 2019 - Newlands School (Outreach)
Team: Andy (lead), Robin, Steve report by Steve
We were invited to deliver a talk to the 6th form Physics Class on some specific elements of Astronomical telescopes.
The School is just around the corner from my house, so for once I arrived first - and was amazed to find parking places had been Reserved for us directly outside reception ! This was very welcome, especially when it turned put the classroom was at the very end of the main corridor ! Fortunately two of the teachers helped with the unloading and it was managed in only two trips.
As usual, it was spitting with rain when we arrived, so the plan for outdoor solar viewing was shelved.
Andy had prepared a PowerPoint presentation and would lead the talk, whilst Robin and I would mention the advantages of Refractors v's Reflectors whilst showing off our telescopes.
Andy covered basic ray diagrams, how Magnification is calculated and how the minimum angular resolution, the Rayleigh criteria or Dawes Limit, is calculated from the diameter of the objective lens or mirror. He also mentioned how lens refraction leads to chromatic aberration and how this has to be designed out in modern telescopes.
Whist talking about the focal length of the telescope and how the field of view varies with magnification, I mentioned how the Dawes limit prevents Earth based telescopes from seeing the Apollo lander on the Moon.
Then, after last months talk on the Extremely Large Telescope (ELT), when I got home, I decided to run the figures.
Rayleigh criteria worked example - What Diameter of telescope can see the Apollo lander ?
What size (Diameter) of telescope is needed to see the Apollo Lander on the Moon from the surface of the Earth ?
We know from the Rayleigh criteria / Dawes limit, that the limiting Angular resolution (radians) = 1.22 * wavelength / objective Diameter.
If we know what Angular resolution we need, then we can work out the telescope diameter, D = 1.22 * wavelength / Angular resolution.
The Moon, diameter 3,475km (3,475,000m), subtends an (average) angle of 0.528 degrees from the Earth. To get radians, we multiply by Pi/180, so 0.528 degrees = .009215 radians (9.215 * 10^-3).
The Apollo Lander diameter is 9.4m. So the angle subtended by the Lander from the Earth is thus 9.4 * 9.215 * 10^-3 / 3,475,000 = 2.5 *10^-8 (radians)
The Wavelength of Green light is 560–520 nm or approx 540 * 10^-9m
Plugging in the numbers we get D = 1.22 * 540 * 10^-9m / 2.5 * 10^-8
D = 26.43m
... and whilst no existing telescope exists with this Diameter, the ELT will have a 39 meter mirror !
Using the ELT, what magnification and eyepiece focal length is needed to view the Apollo Lander ?
The 39-metre mirror ELT has a focal length 743.4m. What Magnification is needed, using a Plossl eyepiece (which has a standard field of view of 50 degrees) and what is it's Focal length if the Apollo lander is to fill 1% of the True Field of View ?
Mag = Eyepiece field of view (Efov) / required (or True) field of view (Tfov)
We know Efov (Plossl) is 50 degrees, what is the required Tfov ?
Lander Tfov = 2.5 *10^-8 radians
If Lander is to fill only 1% of the eyepiece, then required Tfov (degrees) is = 100 * 180/Pi * 2.5 *10^-8
Required Tfov=1.43 * 10^-4 (degrees)
Mag = Efov / Tfov
Mag = 50 / 1.43 * 10^-4
Mag = 349,065
... OK, a Magnification of more than 1/3rd a million is a tad more than the typical Mag of 50 or 60 I use with my Dobsonian, but why not ?
To calculate the eyepiece focal length (fl) we use Mag = Objective fl / Eyepiece fl
Efl = Ofl / Mag
Efl = 743 / 349,065 (meters)
Eyepiece fl = 2.13mm
... Eyepieces of 2mm focal length do actually exist, however they are not very easy to use, Plossl eyepieces having a diameter that scales to the focal length (so you are trying to align your eye with a tiny glass bead about 2-3mm in diameter :-) )
This note last modified: 8th Apr 2019 11:26.
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Laser Pens |
Maidenhead Astronomical Society may use Laser Pens as a pointer during outreach events and talks. Any such use will comply with our Laser Pen Policy, which may be downloaded from here (.pdf)
Essentially, only responsible adults pre-approved by MAS are allowed to use a pointer at an outreach event. Children under the age of 18 and non-approved adults are not be allowed to use the laser pen at any time. Any member of the public bringing their own device (without pre-approval) is asked not to use it during one of our events (and will be asked to leave if they are not willing to comply with this request).
Links
Robotic Telescopes (MAS Links page)
Where we meet (MAS About page)
'Frequently Asked Questions' (FAQ, MAS Beginners page)
exit to: Maidenhead Arts Council (MADAC) MAS web page
exit to: Tim's list of Asteroid Occultation observation opportunities
exit to: European Asteroidal Occultation Network
exit to: Space Weather
exit to: Heavens-Above - times of everything passing overhead, especially ISS, satellites and Iridium flares
exit to: The Astronomer on-line - magazine for the advanced amateur
exit to: BAA (British Astronomical Association)
exit to: SPA (Society for Popular Astronomy) - especially suitable for younger stargazers !
Benefactors and supporters
O2 (award report)
exit to Cash-for-the-community (Baylis Trust)
Royal Borough of Windsor and Maidenhead Lottery grant
RBWM-Education Directorate
Mr B.Smith of Shottesbrooke
Mrs P.Haymes
The Telegraph newspaper
exit to Oregon Scientific
exit to Telescope house