An Ancient Owl (that isn't there)

The Owl Nebula a planetary (starburst) nebula about 2000 light years away in Ursa Major, shot from my backyard on March 24, 2021. At a magnitude of 9.9 it is a very faint target for my street-light bathed backyard, but a 5 inch scope at 90 second exposures begins to pull in the details of the owl-eyes. The two circular dark spots in a green orb give it an owl-eye like appearance. The central star approaching a white dwarf stage in it’s lifecycle. But of course, despite the tempting likeness, there’s no owl there. In fact its not green either. More on that later.

The Owl Nebula is the first of its kind I captured using a German equatorial type mount. This arrived after months of delay caused by a pandemic disrupted supply chain. On the new mount, single exposures can be about three times longer than the measly 30 seconds my prior Alt-Az mount would permit without causing star trails. There is also a steep learning curve and extra effort assembling compared to the prior near grab and go set-up. I convinced myself that this is a small price to pay for catching some 2000 year old photons from the far reaches of our galaxy. This before I got to appreciate the amazing lengths people went to and contraptions they built to view these objects (see below). 

Two centuries - A French and an Irishman

The Owl nebula was discovered by French astronomer Pierre François André Méchain (Pierre Méchain) and published by his observing buddy Charles Messier in his famous catalog (as Messier 97) almost exactly 240 years ago on March 24, 1781. Pierre, the son of a ceiling designer and plasterer, was talented in mathematics and physics but forced to give up studies for lack of money. By a twist of fate he was employed as a hydrographer at Versailles, the suburb of Paris while working in astronomy often in collaboration with comet hunter Charles Messier. Like Messier, Pierre was interested in comets, not in deep sky objects and remains the second most successful comet discoverer after Messier himself. In addition he has about 25-26 deep sky objects to his name including this one.

Drawing of the Owl Nebula (M97)
by Lord Rosse. Source Wikipedia

But the Owl Nebula wasn't named as such until more than 60 years later in 1848 when the Anglo-Irish William Parsons of Ireland drew this sketch (left) probably using the 72 inch reflector he had built for himself at the Birr Castle site in Parsonstown. An astronomer, naturalist and an engineer, Parsons had perfected the right alloy mix to build this massive telescope and a large mirror without cracking it. Known as the "Leviathan of Parsonstown" it was the largest telescope in the century until the 100 inch Hooker telescope came around in California early in 1900s.

An unusual combination of wealth, political and academic interests and love for the natural sciences ran in the family. Parsons himself was the 3rd Earl of Rosse, a member of the British parliament, President of the Royal Society and Chancellor of Trinity College. His wife Mary was an amateur astronomer, architect, pioneering photographer and an accomplished blacksmith. The last skill being unusual for higher class women of her time. One of their four children, Charles, went on to invent the steam turbine founding the Parsons Turbine Company which survives to the day as part of Siemens in Newcastle. The faint recollection that the Parsons turbine was a device I had studied during my undergraduate engineering class, and that now I was admiring a contraption made by his father, created a nebulous sense of curious connection with these men from centuries ago.   

Leviathan of Parsonstown with Birr Castle in the background:
Source: http://www.klima-luft.de/steinicke/ngcic/persons/copeland.htm

Colors Don't Exist (except in our brains) 

Göran Nilsson &
The Liverpool Telescope,
CC BY-SA 4.0
via Wikimedia Commons

It's interesting to note that the Wikipedia image of the Owl Nebula (left) is blue and red, not green. Not surprising since astro-photographers  routinely assign false colors to otherwise invisible light (e.g. infra red) and even visible light for pulling out structural clarity.

While a regular DSLR camera captures color that the human eye sees, the question "what is the true color of the object" is not very meaningful. Color as we know it doesn’t  exist “out there”. It’s merely a human eye/brain trick for identifying various wavelengths of light. 

So how does the color camera used to capture this camera see the green?  It doesn’t.

A color camera image sensor is actually monochrome. It uses an elaborate process to mimic the human eye’s sensitivity to three primary frequencies of light to produce the perception of color.

Incoming light through the lens is split into the three buckets/channels of high low and mid frequencies using either prisms or Red/Green/Blue (RGB) filters (so called only because we perceive the wavelengths that way). The respective channel intensities are then stored (in the same image file) separately as RGB info. Then we play it back on electronic screens in the same ratio using three types of phosphors per pixel that are sensitive to each frequency bucket. In our eye, three types of cone cell receptors sensitive to these three primary frequencies of light convert in into neural electronic signal and the brain interprets the mixture as color. You could apply similar logic to directly viewed natural scenes as well.

So colors exist only in our minds. In fact other species see “color” differently. Honeybees supposedly see more of UV and less red. A certain species of mantis shrimp eyes are known to contain 12 kinds of photo receptor cells which probably leads to a more fine grained color perception. So there are no real colors out there. All perceptions of colors are equally real (or fake) at their own levels. 

In fact the logic applies to all sense organs not just human vision. And while we can pursue the idea of an all encompassing "true reality", one can never say for sure that any reality is the ultimate one. There could always be more unknown layers to it beyond the limits of current observation and interpretation.

The wise owl would probably say: Reality is a perception.

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Imaging details:

Owl Nebula

Mar 24, 2021, 11:42 PM EST

Celestron 127 SLT, f6.3 focal reducer 

Canon 70D ISO 800, AVX mount 

90 s  light X42, 14 dark, 12 bias frames

Additional Reference:

• Lord Rosse and the Birr Leviathan telescope

• The Leviathan’s Legacy: the story of the Birr Castle telescope