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MESSAGE OF THE MONTH
Rates of expansion
I would like to raise a question about the Hubble Constant. I have been reading about the discrepancy with this – in that the further away we look, the quicker galaxies are moving apart – but, every explanation presents the theory of dark energy to explain the discrepancy.
In my layman’s mind surely the discrepancy is explained because the expansion of the Universe is slowing down and not accelerating? My rationale is that the further away we look, the further back in time we are looking, and the expansion is faster there, so does that not mean that the expansion is slowing down?
I have not seen an explanation that spells out why my thinking is wrong; none mention time as a factor to be discounted. I am not looking at the detailed science, as I would not know how to start; that’s why I am hoping to see an answer that explains why I am wrong and puts me back in my place as an IT guy!
Thank you for your thought-provoking message, Stuart! Scientists do take time into account when they’re looking at the expansion rate of the Universe over cosmic distances, with what’s known as the Hubble Parameter. Roughly speaking, this shows changes in the expansion rate over time, while the Hubble Constant is the expansion rate at a specific point in time – now. As the Hubble Constant is a greater value than the Hubble Parameter in the past, it implies that the expansion rate is accelerating. – Ed.
Ready for Xmas
Using my Canon EOS 600D DSLR camera and a standard lens, this was a hastily grabbed shot of the Moon as it was rising over the rooftops. I even slightly overexposed the Moon to give the effect of a Christmas tree with a giant light on the top branch. It’s the ultimate Christmas decoration!
Lost in space
In Chris Lintott’s ‘Comment’ in the December 2021 issue (‘Bulletin’), he mentioned the Huygens spacecraft nearly missing out on sending data back from its landing on Titan. There was also another issue with the mission: Huygens was supposed to send back 700 photos during its descent, using two channels, A and B, so that one photo would go into channel A and the next would go into channel B. But Cassini was missing the command to turn on channel A, and the
700 photos from Huygens all went into channel B’s 350-photo storage location. As only 350 were stored, one photo overwrote the other and half were lost forever.
Morning pair
I was woken early by my son and was treated to an unexpected clear morning, giving great views of Mercury and the crescent Moon over Glasgow (pictured, above). I was unprepared, but managed to grab my camera and get some photos before Mercury faded into the dawn.
By Jupiter!
I have no more than a layman’s understanding of astronomy, and one thing that often baffles me is how ancient astronomers knew so much about our Solar System. For example, ancient Greek and Roman civilizations conflated planets with deities – Mars, the god of war; Venus, the goddess of love and beauty; Mercury, the god of commerce and communication, and so on. They ascribed supremacy to Jupiter and endowed that god with specific properties (such as Jupiter’s ancient Greek equivalent, Zeus, assuming many disguises), which are remarkably close to the properties of that planet discovered later with modern technologies.
How did the ancient Romans know that Jupiter was the largest planet in our Solar System when they didn’t have telescopes? To some extent the properties of Mercury, Venus and Mars are less baffling and could be the result of simple observations like the speed of Mercury across the sky, the beauty of > the evening star, or the red colour of Mars. But surely Jupiter and the outer planets were only dots of light to the Romans?
Reality check
I have found the sky charts in the otherwise excellent Cambridge Double Star Atlas to be rather inaccurate for observers here in the northwest of England. In an attempt to improve matters, I have developed a simple aid (above) which addresses this shortcoming!
Society in focus
In October, York Astronomical Society (YAS) organised an evening of music and astronomy with the York Railway Institute Band. The collaboration between two historical York societies created an inspiring atmosphere. The brass band played a wide variety of music inspired by the night sky, each piece accompanied by a backdrop of images of planets, galaxies and nebulae captured by the Hubble Space Telescope and YAS members. Music ranged from Holst’s The Planets to David Bowie’s ‘Life On Mars’.
YAS was formed in 1972 by a group of enthusiasts in response to the excitement generated by the Apollo Moon landings, and is now a registered charity (#1174488). We currently have 77 members, many of whom have an expert knowledge of the Moon and deep-sky objects. Many are also astrophotographers, with a keen interest in live stacking and plate-solving using the ASIair Wi-Fi control unit.
We meet twice a month, and run an outreach programme in which we host schools and other local groups at our observatory on the outskirts of York. We also hold public star parties in and around York, including at Fountains Abbey. In October we held an event at Sutton Bank to celebrate the North York Moors achieving International Dark Sky Reserve status. The skies were crystal clear and many members of the public joined YAS members in enjoying spectacular observing and imaging opportunities.
Freda Rockliffe, YAS committee member for outreach
Tweet
StrollingShuttereyes @strollingshutte • Nov 22 From a vantage point above Bde Maka Ska [in Minnesota], I took a composite image showing the phases of the partial lunar eclipse from start to peak. Enjoy! @skyatnightmag #LunarEclipse2021
On Facebook
WE ASKED: What are your New Year’s resolutions for 2022?
Carol Miller I don’t normally do New Year’s resolutions, but I want to learn more about the Sun. I’m fascinated by recent sunspot and solar flare activity and, as I have a solar filter for my telescope, I want to record sunspot activity and changes.
Gary Anderson Now I have my mini-Dobsonian, my New Year’s resolution is to make use of every clear night.
Martin Jørgensen To get out more, and look up more!
Kriss Jupiter Appear on The Sky at Night programme and say, “Don’t forget, keep looking up” (hint hint! I don’t think Maggie and Chris would mind).
Steve Walker Sort out my guiding and get to grips with my imaging setup; possibly invest in a new imaging telescope.
Maad Khalil If I don’t manage it before the end of 2021, I would like to be able to see and identify the location of the planets Mars, Neptune, Uranus and Mercury.
Youdhisthir Rai I would like to try and collect pictures of all my favourite objects.
alba_astrophotography • 22 November
Last night I was blessed with a crystal clear sky here in Loch Lomond, albeit rather frosty and cold. There was no way I was passing up what has become a rarity of a clear night. Here is just one of the many deep-sky objects I shot over the course of the night – the Cygnus all of the North America Nebula – processed a la Katie. @bbcskyatnightmagazine @ firstlightoptics @astrobackyard #astronomy #astrophotography #darkskies #cosmos #universetoday
CORRECTION
In the second part of ‘DIY Astronomy, Build a roll-off roof garden observatory’ (December 2021 issue), it incorrectly states that the observatory’s runner “…is supported by corner posts and a 100mm 2 fence post.” This should be a 100mm square fence post.
SCOPE DOCTOR
Our equipment specialist cures your optical ailments and technical maladies
Email your queries to scopedoctor@skyatnightmagazine.com
I have an Altair refractor telescope on a Sky-Watcher AZ-EQ6 Go-To mount. Can I leave this outside or will the damp be a problem?
STEWART BALL
Leaving a mount and telescope outside in the open is always going to be problematic, but the advantage of instant access and consistent polar alignment may make it worthwhile for you. However, the risk regarding dampness should not be underestimated: mount electronics, fixings and telescope optics will not respond well to moisture.
A multi-pronged approach to protection can make all the difference, by tackling various issues separately. Starting at the core of the system, using an anti-corrosion treatment like ACF-50 spray on the mount, fixings and electrical connections will make a difference to their long-term reliability. The internals of the equipment outside telescope can be protected with a desiccant cap like the Astro Essentials Dual-Fit or Farpoint 1.25- and 2-inch Desiccant Caps, installed in the eyepiece holder. Moving outwards, a soft breathable material cover over the complete system will protect your gear from abrasions. To top this off, a breathable, water-repellent and UV-resistant cover from TeleGizmos or Cygnus Astro Covers will offer a final layer of protection.
Steve’s top tip
What is a Barlow lens?
The magnification of a telescope-eyepiece combination is calculated by dividing the focal length of the scope by the focal length of the eyepiece, so increasing the scope’s focal length will increase the magnification. The actual focal length of a scope is fixed by the design of its optical components, but the effective focal length can be altered with optical attachments.
The Barlow lens, an optical tube containing lens elements that diverge the light passing through them, increases the scope’s effective focal length, normally by a factor of two, though there are some designs that can have a greater effect.
Steve Richards is a keen astro imager and an astronomy equipment expert