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Qualia's Blog

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A View From a City: Tal 100rs

Qualia

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M 57: The Ring Nebula

A Little on Lyra

The constellation Lyra is rather small and faint from the city but it is easy to find due to being home to Vega, the 5th brightest star in the northern hemisphere. Interestingly, around 12,000 years ago, Vega (Alpha Lyrae) served as the Pole star and will again if mankind can survive another 12,000 years.

Strummed like a guitar rather than plucked like a harp, the lyre is an ancient stringed instrument dating back to around 3,000BCE. According to ancient Greek mythology, Hemes, the son of Zeus, invented the lyre by stealing a sacred cow from his half-brother Apollo and stringing the cow's intestines across a tortoise shell. Evidently, Apollo wasn't too happy with the act but forgave his half-brother in return for the instrument.

Sometime later, Apollo gave the lyre to Orpheus who became a master of the lyre, enrapturing not only his fellows and the gods of nature but even Hades himself, the dark lord of the underworld. Orpheus met his own violent end when female followers of Dionysus tore him apart limb from limb but in remembrance of this musical genius, Apollo convinced his father Zeus that the instrument played so majestically by Orpheus should become a heavenly constellation and thus, the lyre of Orpheus rests now between Hercules and Cygnus.

A Little on M 57

Placed between the exquiste multiple binary star Beta Lyrae (Sheliak - The Tortoise) and Gamma Lyrae (Sulafat - The Shell) is M 57, a small but perfect smoke ring structure. It is about 2,300 light years away from us and was probably created when a red giant ran out of fuel to burn and its shell of gas, which could no longer be gravitationally held to the dying star, was blown away, pushed outward by hot and fast stellar winds from the red giant.

M 57 is known is a planetary nebula, not because it has anything to do with planets, but because William Herschel, a great astronomer from the late eighteenth century, saw these nebulae, these great spherical clouds round like the planets. M 57's outer layer of gas is about 2 to 3 light years in diameter whilst its darker core is about 1 light year across. It is estimated that this outer ring, that halo we see, expands at about 50 km/s which I imagine from Earth would look like its growing about an inch every century, and all this nebula activity probably began some 10,000 years ago. Today, all that's left of that original red giant is a dense, white dwarf star, the final evolutionary state for a star whose mass was never high enough to become a neutron star.

Observation Notes

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In my 4" refractor from a city roof top, M 57 looks as if some cosmic wonder has puffed a single smoke ring into the heavens. The halo offers the curious affect of a solid ring of misty light whilst its interior, that central vacuity, black like deep space. Nevertheless, if you remain with M 57 for a while, if you give yourself time, it soon becomes apparent that it is not ring like in shape but oval, tilted from northwest to southeast from its centre and that its central core begins to take on the appearance of feebler, lighter kind of absolute darkness.

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Good work, Qualia. I love the background info you have provided as well.

I have yet to get a decent view of M57 from my heavily LP location; unfortunately I can't get on a roof, and I wonder if that height helps by getting you above much of the light? Do you use any filters?

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Hiya Marki,

I've thought about the height and yes, I do think it helps just that little bit. The city I live has an elevation of about 200 meters (over 650') which is about 5x that of the Manchester area, over twice that of the Bristol area, and 8x that of London. Add to this the height of the ten storey building block and the roof, and I imagine I'm over 250 meters above sea level.

What also enhances seeing conditions (with the EP that is, for just by the naked eye I don't get much better than 3 to 3.5) is the fact that the city is very, very dry but what probably counters this is the general temperature during the summer months (evenings generally don't drop below 25º) which is probably causing unseen city-haze.

With this particular sketch I didn't use a filter but my girlfriend has recently bought me a Baader UHC-S Nebula filter and I tried it out the other night. I've only used it once, so a proper review will have to wait, but what I found with my small 4" was that it 'blacked' out the stars yet enhanced the nebula, bringing it forth, so to say. I realised that in i) better seeing conditions (it was a cloudyish June evening in the city with almost full-moon) and ii) a bigger aperture (but not that much bigger would be necessary), this filter could be of some interest to the urban stargazer. The only downside is its cost and the fact that it does block out a lot of light from the beautiful star patterns.

Qualia

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Ah thats interesting. I've read some good reviews of the UHC - tempted to get one myself. I have the Baader neodymium moon and skyglow filter to try cut some of the sodium haze. It works a little, I think, but there are many "white" lights as opposed to the orange, from a carpark immediately oposite my house. Have you given any thought to the OIII filters? I believe these are supposed to be good for "planetary" nebulas?

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With the 4", the UHC doesn't produce wonders-of-wonders but at about 55x to 83x, it certainly does bring out the nebula, and I reckon with a little darker skies and/or a little better aperture, it would be a fine purchase. I have read a little on OIII filters and, yes, I agree, they do seem to have some very good write-ups. My only concern is that it might be a tad aggresive with my current set up.

What I figure is that a narrow band, like the UHC, has the advantage of working on the largest number of objects from a city and does make a difference to the nebula being viewed. As a second filter, the OIII will be excellent, but understanding that it will probably dim the field of stars quite significantly.

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