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The central region of IC1396 Ha Emission Nebula
in the Constellation Cepheus. Rendered two ways post capture; the second showing more of the abundant Ha nebulosity. Image Credit: Kurt Thrust. |
" Is astrophotography an art or a science? Well like most questions in and about the Universe, the answer is complicated and far from straight forward. At the Jodrell Plank Observatory we are often amused by the public's response to the use of photo editing software like Adobe Photoshop, Affinity Photo and SIRIL to enhance data captured by telescope-camera combinations. More recently Artificial Intelligence has become available to further complicate the astronomical conversation of 'what is real'.
Well what is real and unreal in our attempts to render our informed view of the Cosmo?
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| This is another JPO image of IC1396 but rendered using a modified RGB SHO colour palette. |
Lets think about this. Is what we see with the unaided eye real Well the eye is a very good bit of kit but it does have limitations as a receptor of light in either photon or wave format. The eye is particularly good at accommodating disparate and large differences in luminosity. Most of us with reasonable eyesight can look at the Full moon and make out the darker Maria against the brighter surrounding uplands and the even darker night sky. Try doing this with the camera on your phone without a special app and it struggles to deliver anything other than an intensely bright disc set against a dark sky. It can however detect colour, which the unaided human eye struggles with at night. So is colour real or unreal in the night sky?
Our eyes are joined to the brain by the optic nerve and together they make sense of the visual world in which we exist. So, what to us is real in real time, is what our brain considers to be real and at best can be no more than a fleeting series of electrical impulses accepted or rejected and finally composed in a cerebral image according to what we know from experience and an accepted set of values. By and large we see what we want to see and through a veil darkly.
The human brain like the eye, is a very fine piece of 'wet ware' but it can be deceived in many ways. The Brain is a master at finding patterns and order in chaos even when none exists.
Let us return to colour in astrophotography, colour is real or at least the spectrum of light is real and astrophysics makes use of the colour difference of stars to determine their temperature and many other scientific things like radial motion. Colour is the eye's or camera sensor's response to the wavelength of incident light. If the image data we capture is to be used for science rather than art the way the data is processed is crucial in protecting the datas' scientific validity. When we capture and process the spectral details of stars at the JPO we follow strict protocols to ensure the data remains uncorrupted.
Much of the posts on the JPO blog are made to bring celestial objects to the attention of the general public and as such the datas are treated with less rigour during post capture processing. We regularly increase or decrease colour saturation and relative luminosity to emphasise interesting features of astronomical objects. We also use specialised filters to identify differences in the chemistry of ionized nebulous gases. We sometimes reduce he number of faint stars in an image to aid clarity. We always seek in our post capture processing, to increase the signal from the astro-target whilst reducing the unwelcome random noise. Latterly, we use AI to do this job.
The JPO team goes the extra mile to follow these goals:
- To create images that have a scientific narrative.
- To create interesting images with artistic impact.
- To avoid adding spurious artifacts by design or accident.
- To use specialist software and AI as required in delivering on the first 3 goals.
The above two images of the central area of the emission IC 1396 shows how different the image can look by just tweaking the luminosity and colour saturation levels. So, you chose what is real and what is not in your Universe!" - Joel Cairo CEO of the Jodrell Plank Observatory.
"The captured image exhibits the wide-field ionized hydrogen emission region within the IC 1396 complex, an H II region and star-forming complex located approximately 400 light-years away in the constellation Cepheus.
Gas Emission and Ionization Physics: The pervasive warm orange-red luminescence across the field corresponds to standard Hydrogen-alpha recombination radiation at a wavelength of 656.3 nm. This emission is driven by intense photoionization from nearby massive, hot stars—principally the O-type multiple-star system HD 206267—which emit energetic ultraviolet fluxes lambda < 91.2 nm that ionize surrounding atomic hydrogen.
Morphology and Dark Dust Structures: Irregular, dark silhouettes and web-like filamentary features interlaced throughout the emission background represent dense, cold interstellar dust lanes and molecular clouds. These optically thick concentrations attenuate background optical light via Mie and Rayleigh scattering, shielding the embedded interstellar gas from ionizing radiation. Near the center-right of the field, a distinctive dense bright-rimmed globule corresponds to IC 1396A (the Elephant's Trunk Nebula), where strong stellar winds and radiation pressure compress the dust to trigger active star formation and protostellar accretion.
Point-Source Characteristics and Field Optics: Overlying the nebular background is a dense field of foreground and embedded Milky Way stars. Bright point sources display pronounced diffraction spikes arranged in a four-point cruciform pattern, an optical artifact characteristic of primary aperture spider vanes or post-processing star-spike algorithms. " - Gary Gemini Coms Manager at the JPO.
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An image of the Great Orion Cloud rendered two ways
on the right to enhance Sll Ionized nebulosity. |
