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MESSAGE OF THE MONTH
Addressing Earth
I need to know the answer to a very important question; it’s one that my children asked me the other day. The question was: what is the planet Earth’s Universal address? For example, if someone from a distant planet wanted to send me a letter or a parcel in the post, what address would they need to put? I hope you can provide me with this important information, which needs to be 100 per cent accurate.
That’s a very interesting question, David! Your Universal, or cosmic, address would be your postal address, followed by: Earth, Solar System, Oort Cloud, Local Interstellar Cloud, Local Cavity, Orion Arm, Milky Way, Local Group, Virgo Supercluster, Laniakea Supercluster, the Universe. It’s challenging to provide an accurate address, though, since it will depend on our own frame of reference on the Universe, which could be very different where you’re sending the parcel; and in the time it takes to delilver, everything in the Universe will have moved! – Ed.
The ‘Message of the Month’ writer will receive a bundle of two top titles courtesy of astronomy publisher Philip’s: Nigel Henbest’s Stargazing 2022 and Robin Scagell’s Guide to the Northern Constellations
Winner’s details will be passed on to Octopus Publishing to fulfil the prize
Shoot for the Moon
I’ve been meaning to send in my first attempt at catching a photograph of the Moon rising and I’ve eventually got around to it. I turned 40 on 22 July and asked for a monocular and stand as a present.
I got into stargazing, Moon watching and tracking the International Space Station (ISS) while I was shielding due to COVID-19 last year and again this year, and I thought I’d pass the time with something new. For my birthday I received a 12×55 high definition monocular with a smartphone attachment. With a bit of beginner’s luck I managed to capture the Moon rising with a tree and a wind turbine on the horizon (see picture, left). I’ve got a lot more work to do with focusing and steadying the stand, but I can’t believe the start I’m off to!
Fit for the Sun
In response to your reply to Colin Anderson in the September issue (‘Scope Doctor’, page 19), in which he wanted to fit the whole disc of the Sun into his image: he asked if he could use a focal reducer and you laid out why this wouldn’t work. I wanted to let Colin know that he could achieve what he wanted with his Newtonian, and fit the whole disc of the Sun into his image, by using a camera with a larger sensor to capture more of the light cover. He may already have a DSLR camera to hand which would do the job; a DSLR with a smaller APS-C size sensor would work, as his Hypercam 183C has a sensor size of 13.2mm x 8.8mm, while an APS-C sensor is 25.1mm x 16.7mm.
Hazy view
On the morning of 17 August, I looked out of the window in the early morning and the Sun had just risen above the horizon (it was shining through haze and was safe to look at). It appeared much larger than when high in the sky. Could it be that the ‘Moon illusion’ is not confined to the Moon?
It could well be the case the Sun appears larger when close to the horizon, as it’s the way humans perceive the outside world that creates the optical illusion. However, please don’t take any more risks with your eyesight: looking at the Sun even through cloud isn’t safe. The sunlight may be less intense, but its UV light can still damage the photoreceptors at the back of your eyes. If you do any solar observing with the naked eye, you should always use eclipse glasses. – Ed.
Lunar puzzle
I took two photos last year, which have been puzzling me. They were taken from my back garden after I finished my night shift and the detail [EXIF data] attached to the photos says they were taken at 6.19am on the 12 November 2020. I vaguely remember something about an eclipse at that time, but I can’t find any more info. The first photo is from my back garden and the second is an enlargement of the Moon. Do you have any idea what the grid is on the Moon? Thanks in advance for your help!
The grid on the Moon is certainly unusual, Paul! It’s hard to be definite without knowing the camera and software used, but it could be an unwanted artefact (noise) on the image from the camera sensor. The only eclipse in November 2020 was a penumbral lunar eclipse on the 30th, visible from the UK as the Moon set; it’s possible that the time and date settings on your camera may need to be reset. – Ed.
CORRECTION
• In the feature ‘Late summer variables’ (September 2021 issue, page 72), in the widerfield locator chart for R Scuti, the star near R Scuti was labelled wrongly as Beta Cygni. Beta Cygni was also mentioned in the caption. This should be Beta Scuti in both cases.
Society in Focus
The last day that members of the Flamsteed Astronomy Society met together for a main monthly lecture was on 9 March 2020 – though we didn’t know it at the time. We had an inkling that travel restrictions might make it difficult for guest speakers to travel to our home at the Royal Observatory Greenwich (ROG), so we explained to our members that night that we were looking at the possibility of moving talks online.
Two weeks later, the UK was in lockdown, but we had already trialled Zoom with our members, who welcomed the opportunity to keep our talks going. Silver linings in this COVID-19 cloud are few and far between, but we found we could accommodate more of our members at an online event than we could squeeze into our National Maritime Museum lecture theatre. The internet enabled us to bring speakers ‘to Greenwich’ who might not have been able to travel so far, even in ‘normal’ times. We’ve welcomed a range of lecturers – from Prof Dame Jocelyn Bell Burnell and Prof Catherine Heymans, to science writers Dallas Campbell and Jo Marchant, while our ‘history of astronomy’ programme didn’t skip a beat.
Although our usual observing sessions have been cancelled, as have various visits, we have run astrophotography workshops online and a three-part ‘Introduction to astronomy’ series.
But, as of the time of writing, we are all eagerly awaiting a return to ‘real world’ events and being a more ‘social’ society. It will be good to be back in our usual space.
Andy Sawers, former Chair of the Flamsteed Astronomy Society, 2016-21
Tweet
Paul Martin
@Tyrone_skies • 12 Aug #Perseids put on a good show last night for us up at Beaghmore. Caught two meteors in one frame alongside a beautiful Milky Way. #darkskies @StormHour @omdarksky @VirtualAstro @ ThePhotoHour @skyatnightmag @UKMeteorNetwork @barrabest
On Facebook
WE ASKED: What are your top tips for observing and imaging under the light pollution of cities?
Darshna Ladva I’m in Stanmore, London, and you can image here. You either have to manage your exposure times or use a light pollution filter; it all depends on your target and kit.
Brendan Scoular I try to observe after midnight when it seems that the atmospheric conditions stabilise to offer better viewing. That, coupled with my neighbours’ garden lights going off at 11:30pm, certainly helps.
Denis Pius Some astrophotography tips :
1. Avoid direct light to your lens. Set your camera in a place with no streetlights, or block the light hitting your lens.
2. Avoid bouncing light. Don’t set your camera lens facing a wall that bounces light from behind or the side.
3. Use a lower ISO. Normally in the city I use ISO 800; if there are streetlights nearby I use ISO 400.
4. Separate the foreground and the sky with different shutter speeds and blend together in postprocessing.
Nick Williams I use a star tracker and light pollution filter on my DSLR camera. By stacking 30x 2’ exposures at ISO 400, I even managed to image the Milky Way in Chingford, London.
Paul Adamson I live in Somerset under a dark pristine sky, but I’ve spent most of my life in London. That’s how I came to learn the constellations as it was only the brightest stars that I could see. The planets and Moon are no problem anywhere.
rob.barsa • 9 August
This photo depicting the observation of the #Perseids meteor shower was created near a small village, Mníšek nad Hnilcom, in eastern Slovakia. It shows many meteors and demonstrates that all the Perseids are identified by the radiant in Perseus from where the meteor paths appear to originate. It also shows a group of amateur astronomers performing visual observation. @universetoday @thisisslovakia @bbcskyatnightmag @twanight
SCOPE DOCTOR
Our equipment specialist cures your optical ailments and technical maladies With Steve Richards
Email your queries to scopedoctor@skyatnightmagazine.com
I recently purchased a Celestron StarSense Explorer LT80AZ. I’ve aligned it and set it up with my mobile phone, but even though I can see terrestrial objects I can’t see celestial ones. Where am I going wrong? MAGGIE MURRAY
You mention that you can see terrestrial objects but not celestial ones, so the telescope and eyepieces themselves are working. This suggests that we need to revisit the fundamentals of night-time observing.
Your telescope comes with a star diagonal, two eyepieces and a Barlow lens so select the eyepiece marked 25mm and insert it in the diagonal. For now, dispense with the smartphone app, simply point the telescope at the sky on a clear night when it has got truly dark. Ensure that the dust cap is removed (yes, it happens!) and that there is no nearby extraneous light, then position your eye centrally over the eyepiece. Gently rotate the focus knob to move the focus tube fully in and then out until you reach the point at which you can see stars. Make very fine focus adjustments until the stars are as small as possible to attain accurate focus. Now you can start searching the sky for other objects either with or without the app.
Steve’s top tip
What is chromatic aberration?
The glass lenses in a refractor bend or ‘refract’ the light from distant objects and focus it at the focal plane. However, simple glass lenses can’t focus all the colours of light to exactly the same focus position because the refractive index of glass varies with the wavelength of the light passing through it. This phenomenon results in coloured halos around bright stars and colour casts on opposing edges of the Moon and planets. This optical issue is known as chromatic aberration and telescope designers use special low dispersion glass (ED glass) and two or more different glass elements to try and alleviate the problem.