Wednesday, August 5, 2015
I estimated the lady in the park to be in her sixties. Intent on engaging me in conversation, the dialogue moved from small talk about the dogs to grave concerns she held for the world nearing the end of the Mayan calendar. The world didn’t end, and predictably so! Extinction, at the hands of the Conquistadors, put an end to the Mayan calendar. This somewhat permanent and obvious fact, absent.
There was more to this dear lady than conversation. Her style of dress and preoccupation with New Age Pantheism was an odd but familiar persona. She reminded me of a past acquaintance taken up with the philosophy of the Age - crystals, talismans and all the paraphernalia - possessed of an all embracing outlook, frequently a source of conscious self-contradiction.
Far from demonstrating a shade of consistency to their thoughts and conversation, the lady in the park was graceful, quirky and apparently genuine in her concern. The other, possessed of a vengeful, and oftentimes, duplicitous spirit, mildly disturbing, if not nutty and demonstrably dysfunctional.
“The Universe,” I came to understand, is that oddly indefinite source of New Age consciousness, presumably guiding the human soul on life’s journey. An indefinable path to higher expression - reincarnation - or whatever else hopeful hearts conjure up, seeking the promise of better things, though determined to have their way in the present.
Having shared the same world-view, at a time long gone, I am reminded that the age-old-expression of self-determination, wishing unfettered independence - the desire to be perfect in one’s own right - is merely another expression of human independence - to be one’s own God, apart from God.
This diverges from the lady in the park, quite apart from the other intent on including all in her personal chaos. Nonetheless, and despite her good and kindly ways, the desire for self-determination, no less motivated, and no less virulent, within this seemingly gentle soul.
Saturday, July 18, 2015
Findings of the New Horizons probe, as it flew by Pluto and its moons, has surprised some and confirmed the predictions of others.
This wonderful feat of engineering, a vehicle of discovery, is a remote messenger contributing to the inevitable debate about origins.
As some seek to prove the universe old, and say “no God,” its youth becomes more apparent, and the probability of a happenstance realised for what it is - wishful thinking.
Friday, June 12, 2015
When first using PixInsight, I found that DSLR preprocessing was not easily facilitated. Following several forum discussions scripts became available smoothing the way for DSLR preprocessing tasks. There was however no documented workflow and it was up to the user to work it out, with help from other users in the same boat.
The following is a copy and paste from the PI thread.
This thread is a description of an alternate method of DSLR RAW image reduction/preprocessing. It is partly intended for newcomers to astrophotography, and PI, who are using DSLR cameras, and hopefully it provides a degree of flexibility when using PIs excellent image calibration tools.
The method described here is a simpler option and is not intended to replace the standard PI dark optimization/scaling method of image calibration.
This guide assumes that DSLR RAW data is non-linear compared to dedicated astronomical imaging devices, for the following reasons; DSLR sensor data is modified by camera firmware to produce a photo quality image - this affects the linearity of DSLR RAW data (downloaded from the camera) - it is assumed that the various makes and models differ as to the degree of firmware modification.
“sRGB Colorspace Correction
Saving an image using a sRGB Colorspace is very similar to Gamma correcting an image, but is slightly more complicated so as to better reproduce the actual response of the human eye, specifically with very dark shades of color.” (Magick).
DSLR cameras usually have two colour format options, sRGB and AdobeRGB. sRGB is a standard format used in many applications. AdobeRGB increases the colour gamut to include more cyan and green hues. As a rule, sRGB is used for astrophotography.
DSLR cameras internally process the linear data obtained from the camera’s sensor (CMOS or CCD) to produce an image which is clean and within the response of the human eye. The RAW image from a DSLR camera is a modified version of what the sensor ’saw’. As such the image produced is just a rendition, rather than a faithful representation of the sensor (linear) data - which is to say, DSLR RAW data is not linear.
Despite the non-linearity of DSLR RAW data PI handles it very well, even when linear processing methods are applied.
A data set usually comprises, bias frames, dark frames, flat frames and light frames. However, because DSLR cameras are generally not cooled and because DSLR RAW data is not linear, poor acquisition technique almost always results in data which is not representative of the other data in the set - and invariably leads to preprocessing problems.
The alternate work flow is partly intended to offer an option which may assist producing a reasonable image - though, it is primarily intended to overcome the issues of DSLR RAW data non-linearity, and to some extent poor data acquisition technique.
It is very desirable to match dark and light frames in particular, with the following caveats.
For the alternate work flow described here, it is best to match dark and light frames to ISO, temperature and exposure time. If using the PI standard linear work flow, which involves dark optimization/scaling, then light frames and dark frames are matched to ISO. However, because dark noise is a function of exposure time and temperature, it is possible to match dark noise to light frames by changing one variable or the other. The dark optimization/scaling method is explained here, and is not discussed further.
In practice an alternate method of preprocessing DSLR RAW data in Pixinsight does not leave the user without options where one or the other is not producing the desired results. There are of course no silver bullets. Good acquisition techniques and learning the art of preprocessing PI style can produce excellent results with DSLR RAW data, despite its vagaries.
It cannot be overemphasized, that if the following workflow is not successful there is most likely a problem with acquisition of the frames. Acquisition is an aspect that doesn’t get enough attention - time spent getting acquisition right is time well spent and will avoid complications down stream.
Conventions - Menu toolbar selections; e.g., > View > Explorer Windows > Format Explorer > DSLR_RAW - this is first settings dialogue.
What follows is my method (long hand for illustration) of preprocessing DSLR_RAW data in PixInsight. It should be no problem to plug the same values into the BatchPreprocessing script, with the caveat that the master bias, dark and flat frames are created long hand. We can then load our master dark, master flat and light frames, tick the master dark and master flat boxes and press [ Run ]
Note: If this method doesn’t produce good results in the final image, first check the quality of darks and / or flats. This method has been tested over and again.
6. Calibrate Light Frames with Master Dark and Master Flat and deBayer calibrated lights.
This shows light raw frames loaded for calibration - that’s OK, but it’s just as well to convert to tiff first.
Note: the optimize dark box is now NOT TICKED - this is NOT default. It is recommended to clear this box. However, try it both ways if you have time and compare the results.
Note: Cosmetic Correction may be applied at this point.
The result is a PixInsight .xisf file. The output format can be changed in the BatchPreProcessing script.
In summary, the DSLR RAW calibration has been simplified by subtracting the bias from the flats only - note: the bias is not subtracted from the dark or light frames. Next the master dark is subtracted from the lights and the result divided by the master flat. The calibrated/reduced light frames are debayered, registered and integrated to produce an integrated image for post processing.
A good set of frames properly acquired is essential. Dodgy frames will mess very badly with DSLR RAW data.
Here is the BatchPreProcessing script set up once bias, dark and flat master frames have been created long hand.
Light frames can be loaded RAW as shown. Alternatively, convert all files to 16bit .tiff
Saturday, October 25, 2014
To put things in perspective. After what seems a lifetime subscribing to scientific naturalism - evolution - and upon examining the arguments about origins, I conclude that the universe must (by way of reason and probability) be a work of intelligent creation - The Creator and His creation, Man, the epicentre of its purpose.
Further concluding, that all arguments about origins can be categorised as Creator, no Creator (God, no God), worldview - there being no middle ground. Speculation about natural origins is, as I eventually discovered, wishful thinking - a calculated diversion from reality. An “escape from reason.” There is, I am convinced, no sound argument to the contrary, however well constructed.