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 - Mankind and his Creator 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 no sound argument to the contrary however well constructed.

Friday, October 24, 2014

To whom shall the writer give account: the bounds of freedom

“Finding expression, to say what you want to say, comes with a wonderful sense of freedom. Then, having written, the responsibility for one’s words clearly defines that no man is free, completely! Bound by the words of our mouth and that of our pen - keyboard - we answer to all, and God.”


Thursday, May 1, 2014

Astrophotography DSLR RAW Data Calibration: preprocessing

This thread has its origins in Craig Stark’s article about the non-linearity of DLSR RAW data, as well as discussions on various forums about preprocessing of DSLR RAW frames.

The non-linearity of DSLR RAW data (compared to 16bit CCD linear data), is a product of camera firmware corrections, which are designed to create a RAW image that is easily processed, out of the box! Non-linearity is a technical term for data that has been manipulated in some way from the RAW linear state captured by the CMOS sensor. This is the case with DSLR RAW images (data) to produce a nice picture.

Because DSLR RAW data is manipulated in camera, it has already been processed to a point which requires unique handling during preprocessing; that is, during the calibration process. To avoid further data loss, typically experienced by applying 16 bit processing methods to DSLR RAW data; the following is recommended

1. Do NOT bias subtract the dark frames or the light frames, as you would if scaling the dark frames.
2. DO bias subtract the flat frames only.
3. DO subtract the master dark frame from the light frames - bias in the dark method.
4. Do NOT apply pixel rejection algorithms to bias, dark or flat frames - avoid data loss.
5. DO take flats and bias at the lowest ISO.
6. DO apply pixel rejection algorithms appropriately to calibrated light frames.

The issues discussed here were more evident when preprocessing cooled, temperature regulated, DSLR images, and does not rule out the same application to uncooled DSLR RAW data. However, if you have one of those supercooled DSLRs, perhaps dark frames are a thing of the past. A carefully constructed master bias and flat may be all that is required.


“The point of this discussion is, that problems arise with DSLR RAW data when dark frames are bias subtracted and then the master dark frame is subtracted from the light frames, as well as subtracting a master bias - as one would do if scaling darks. This is a process normally applied to linear data and is not suited to DSLR RAW data calibration. Linear processes applied to DSLR data may produce less than optimal and sometimes devastating results due to data truncation.”

Because DSLR RAW data is processed in the camera, it is “clean” to begin with, and applying pixel rejection algorithms to calibration frames is unnecessary. However light frames are exposed to unfriendly light sources and pixel rejection is necessary.

A note on bias frames - CMOS sensors do not have a bias and instead produce a pattern of fixed noise, which, to all tense and purpose, may be considered bias and applied in the same way.

The practice of not calibrating dark frames is common place, and has been for years; “the-bias-is-in-the-dark.” However, the advantages and reasons, applied to DSLR RAW data, may not be clearly understood - “it’s always been done that way.” Some software defaults to dark scaling and is not suitable for DSLR RAW data.

“A typical DSLR RAW calibration data set, comprises uncalibrated darks and bias subtracted flats. Flats and bias frames can be taken at the cameras lowest ISO setting.” Denoising the master flat frame is recommended by some imagers.

AstroArt preprocessing is a one time operation, and uncomplicated. In PixInsight, master bias, master dark and master flat frames are prepared separately to avoid bias subtraction of dark and light frames. Either way, pixel rejection is applied to light frames only.

Thursday, October 31, 2013

Welcome to FlatPress!

This is a sample entry, posted to show you some of the features of FlatPress.

The more tag allows you to create a “jump” between an excerpt and the complete article.



The default way to style and format your content is BBcode (bulletin board code). BBCode is an easy way to style your posts. Most common codes are allowed. Like [b] for bold (html: strong), [i] for italics (html: em), etc.

There are also quote blocks to display your favourite quotations.

and 'code' displays your snippets in a monospaced fashion

img and url tag have also special options. You can find out more on the FP official website.

Entries (posts) and Static pages

This is an entry, while About is a static page. A static page is an entry (a post) which cannot be commented, and which does not appear together with the normal posts of the blog.

Static pages are useful to create general information pages; with this new version of FlatPress you are allowed to make one of these pages the opening page for your visitors. This means that now with FlatPress you can now run a complete non-blog site. The option to make a static page your start page is in the option panel of the admin area


FlatPress is very customizable, and supports plugins to extend its power. BBCode is itself a plugin!

We have created some more sample content, to show you some of the FP well hidden functions and gems :) ; you can find two static pages ready to accept your contents (About me) and links (Menu): notice that your links will appear on your sidebar as well, this is the magic of the blockparser widget: see the FAQ for this and more.


There isn’t a single fixed element in the sidebar(s). All the elements you can find in the bars sourrounding this text are completely positionable, and most of them are customizable as well. Some themes even provide a panel interface in the admin area.

These elements are called widgets.

For more on widgets and some tips to get nice effects, read the wiki

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