By two great events, nonetheless.

Last Friday afternoon I had the utmost pleasure of attending a meet and greet with Mike Portnoy, the drummer for Dream Theater.  He is well-regarded as one of the greatest drummers in the world.  Do yourself a favour and watch this for an example of his wizardry.  I had photographs taken with him, and, got my CD liner notes for Metropolis Part II: Scenes from a Memory signed (across the lyrics of Finally Free, no less), as well as above Mike's photograph on the liner notes to Images and Words.  I also had the DVD cover slip of Score signed.

Later on in the evening, I went and saw G3 live in Sydney.  It was the single most greatest night of my existence.  To see John Petrucci (Dream Theater) live was a dream come true.  If that wasn't enough, Steve Vai and Joe Satriani also played individual sets in the evening.  They then all came together on stage to have a mega-jam.  I can't put into words what I experienced that night, suffice it to say that you can imagine what happens when three of the world's best guitarists get on stage.  Mike Portnoy drummed for John Petrucci's set.  After John had finished playing, Mike ran to the microphone and said, "Thank you so much, hopefully we'll see you next year with Dream Theater," at which point the crowd went wild.  Dream Theater has been around for 20 years but they've never been to Australia.  I will no doubt see them in all their concerts on the eastern seaboard.

Well, that's the first event taken care of; the second is the following, which happened earlier this evening:

Hi Humayun,

I've just seen your Large Magellanic Cloud picture. Fantastic!

Would you be interested in seeing it published in Australian Sky & Telescope magazine? I'd be keen to publish it.

Cheers,
__________________
Greg Bryant
Editor
Australian Sky & Telescope

My dream was to get published in a magazine, and, that too, has now been realised.  He is also interested in publishing my other images, too.

In other news, my Losmandy G-11 has arrived in Australia.  I just have to make the final payment and it will be shipped to me.

I guess, all I can say is, brace yourselves for humbling deviations of the Universe in which we live in, to grace your deviantWATCH pages, soon.

I sold my equipment and now I feel empty.

Truth be told, I pushed my equipment as far as I could take it.  The periodic error on the LX90 was disgusting to say the least; even with an autoguided set-up I was having a lot of problems with overcorrection and losing guidestars.  Of course, it didn't help that the guiding software I was using was rubbish, too.

I have a new Losmandy G-11 with Gemini en-route from the United States.

Losmandy G-11

I'm going imaging this weekend at Lake Bathurst, where I shot my NGC 2070 (Tarantula Nebula in Dorado) image.  I will be making use of a 5" Borg F/5.3 apochromatic refractor mounted on a Takahashi EM-200, and probably guided with an SBIG STV.

I will be reshooting my Pleiades image as I'm not 100% satisfied with it.

Scroll down for a new test picture.

DAILY DEVIATION FEATURE: JUNE 24TH

I am so pleased to report that on the 24th of June, 2006, my recent deviation, Antares in Scorpius - Mk II was selected by ^hesitation as a Daily Deviation Feature.  Thank you to the many people who viewed the image, as well as my other deviations and left me with so many nice comments, notes and favourites.  A big thank you must go to ~Beachrockz4eva for suggesting it in the first place.

WORK IN PROGRESS AND/OR TEST IMAGES

M6 (The Butterfly Cluster)
Single JPG F/10, 65 second, ISO-1600, prime focus sub-exposure
Pre-processing: none
Post-processing: slight levels and curves adjustment
Yield: approximately 1 minute

M8 (The Lagoon Nebula)
Crop of kappa-sigma stack of 30, F/6.3, 60 second, ISO-400 sub-exposures (no flat frames)
Pre-processing: dark frame subtraction; calibration; registration; kappa-sigma stacking; logarithmic stretching
Post-processing: black/white points; levels
Yield: approximately equivalent to a half-hour long exposure

M45 (The Pleiades)
Crop of single JPG F/6.3, 120 second, ISO-1600, prime focus sub-exposure
Pre-processing: none
Post-processing: slight levels adjustment
Yield: approximately 2 minutes
Note: Field curvature is quite apparent as the Meade Series 4000 F/6.3 focal reducer I'm using isn't of good quality

M20 (The Trifid Nebula)
Kappa-sigma stack of 37, F/10, 45 second, ISO-1600 sub-exposures
Pre-processing: dark frame subtraction; flat frame division; calibration; registration; kappa-sigma stacking; logarithmic stretching
Post-processing: black/white points; levels; curves
Yield: approximately equivalent to 28 minutes of exposure

M22 (The Sagittarius Cluster)
Crop of kappa-sigma stack of 27, F/7.0, 30 second, ISO-400, prime focus sub-exposures
Pre-processing: dark frame subtraction; flat frame division; calibration, registration; kappa-sigma stacking; logarithmic stretching
Post-processing: black/white points; levels; curves; colour balance; slight unsharp mask
Yield: approximately equivalent to 14 minutes of exposure

The Alnitak Region: The Flame Nebula and The Horsehead Nebula
Kappa-sigma stack of 3, F/7.5, 600 second, ISO-800 sub-exposures
Pre-processing: dark frame subtraction; flat frame division; calibration; registration; kappa-sigma stacking; logarithmic stretching
Post-processing: black/white points; levels; curves
Yield: approximately equivalent to 30 minutes of exposure
Note: The image is extremely noisey as this is the combination of only 3 exposures and because my camera is insensitive to the 6563 angstrom (656.3 nanometre) hydrogen alpha emission wavelength

Note: the diffraction spikes in the M6, M8, M45, and Alnitak images were artificially recreated using 30-pound fishing line fastened (as a cross) to the primary corrector plate housing.  You can never have enough diffraction spikes; classical-looking stars are divinely elegant.

Now for something completely random. Here is an image taken at Wentworth Falls in the Blue Mountains in New South Wales. This image was taken in December, 2005.

Wentworth Falls, Blue Mountains, New South Wales
Click on the image for full size

THE BLACK ART OF ASTROPHOTOGRAPHY

People often wonder how much work is involved in producing breathtaking images of the heavens.  I thought I'd make use of the long weekend and place some images in my journal which show RAW images taken off the camera's sensor (converted to JPG for web) and the final image produced after the long and arduous task of pre- and post-processing.  This journal entry will showcase one of my images.

In addition, this journal entry is not a how-to (which some people have asked for); that is something which is going to come later on down the track.  However, what this entry will display is akin my previous entry which displayed M20 - the Trifid Nebula - before and after some minor processing.

So, enough with the rambling; let's get into some eye candy.

The Pointers and Crux

PRE-PROCESSING
1. Light Frames
Light frames are photographs of the subject or target in question.  They're called light frames, simply because they capture light.

For this target, I shot two sets of 20 images.  One at ISO-800 and one at ISO-1600.

a. Single (1 of 20) RAW 30 second ISO-800 sub-exposure


b. Single (1 of 20) RAW 30 second ISO-1600 sub-exposure

If you look carefully in the second image, you'll notice three diagonal lines; two up the top, and a rather short one towards the bottom left.  You may be wondering what these are.  In actual fact, these are satellites which I just so happened to capture during this thirty second sub-exposure.  These particular satellites are the COSMOS communications satellites.  There's no sign of these diagonal lines in the final image.  This is because the stacking process identifies anomalies, or outliers, in the image data and subtracts them.

2. Dark Frames
Dark frames are photographs of nothing; they are photographs taken with the cover of the telescope in place or the lens cap in place.  Dark frames actually capture thermal noise, dark currents, atmospheric effects on the sensor, hot (saturated) pixels as well as stuck pixels.  The point of taking dark frames is to subtract this random noise from the light frames.

Dark frames are sensitive to temperature, and therefore it is advisable to take them immediately after capturing light frames; at the same exposure length and ISO setting as the light frames.  Therefore, for this target, I had to take two sets of dark frames; one set of nine at ISO-800 and another set of nine at ISO-1600.

a. Single (1 of 9) RAW 30 second ISO-800 dark frame


b. Single (1 of 9) RAW 30 second ISO-1600 dark frame

Notice the (pink) amp glow in both images towards the bottom right of each frame?  This glow is due to electrical noise in the sensor or heat generated within the mechanism.  If we don't subtract dark noise from our light frames, we will be left with noise and glow at the same location in the light frames as where the noise occurs in the dark frames.  Note also the change in intensity from ISO-800 to ISO-1600.

3. Flat Frames (Lights)
Flat frames are photographs taken of either the twilight sky or of a flat, evenly-illuminated object, such as a wall.  Flat frames capture optical train aberrations such as vignetting, dust motes or particles on the lens, sensor or telescope's primary corrector plate.  Flat frames are taken at ISO-100, at the same F/ratio as the light frames.  The exposure length is dependant on the illuminated object; typically, the aim is to reach 1/2 to 2/3rds peak histogram display on the output of the camera's LCD display.  For any given illuminated object, this could range from 1/8th of a second, all the way up to 1 second.

a. Single (1 of 9) RAW 1 second ISO-100 flat light frame

Notice the vignetting effect towards the right of the frame?  The image is somewhat darker on the edge than towards the middle.  This is because the outer edges of the sensor are 20% less sensitive to light than the middle of the sensor.  If you look very carefully, towards the mid-top area, there are two or three small dark spots.  These spots were caused by dust motes on the lens and dust particles on the camera's sensor.  If vignetting and dust spots aren't removed at this stage, they detract from the final image.

4. Flat Frames (Darks)
For exactly the same reason as having taken dark frames for our light frames, we also have to take dark frames for our flat frames.  Again, at the same exposure length and ISO setting as our flat light frames.

a. Single (1 of 9) RAW 1 second ISO-100 flat dark frame

After having acquired all this data, what do we do with it?  My workflow (for this example) is as per the following steps, beginning with the ISO-800 data:

1. Create a flat master dark frame by median combining the 9 flat dark frames
2. Calibrate the 9 flat light frames by subtracting the flat master dark frame* (created in step 1) from each flat light frame
3. Create the master flat frame by median combining the calibrated (done in step 2) flat light frames
4. Create a master dark frame by median combining the 9 dark frames
5. Calibrate the 20 light frames by subtracting the master dark frame* (created in step 4) from each light frame and divide the resultant data by the master flat frame** (created in step 3)

*This removes any hot pixels, thermal noise, etc., in the flat light frames
**This removes optical train aberrations such as vignetting and dust particles

Once this calibration process is complete, I then register (align) the images so that they're all in the same orientation relative to each other.  I then split each of the 20 images into their respective red, green and blue channels, perform a kappa-sigma stack (add the images together without clipping (saturating) data) and save the resulting sum of each of the red, green and blue channels.  Next, I rejoin the tricolour sums into the one RGB image.  I then crop the image so that any non-overlapped portions can be removed (think of two rectangles placed on top of each other, but not perfectly; the parts which are not overlapping are redundant); if they're not removed they affect the post-processing stage; set my black and white points, set the RGB balance, remove light pollution gradients (if evident) and perform a levels stretch.  I save the resultant data as a *.PSD file and begin the post-processing component of the black art.

I repeat this process for the ISO-1600 data, except for step 3.

That is the pre-processing stage complete.  That's a lot of information to absorb!

POST-PROCESSING
5. Final Composite
After pre-processing in IRIS is complete, I have a kappa-sigma stacked set of ISO-800 image data, as well as a set of ISO-1600 image data.  I then kappa-sigma stack these two together.  Many hours after adjusting levels for each colour channel, applying multiple curves layers for each colour channel, tweaking hue, saturation, and colour levels, I present the final composite ready for framing and re-sizing for the Internet.

a. The final pre- and post-processed composite:
((40 light frames MINUS master of 18 dark frames)
DIVIDED BY (master of 18 flat light frames MINUS master of 18 flat dark frames))
kappa-sigma stacked

Comments and critique welcome.

June Journal Feature Appearances

*Jezhawk [link]
~EtherealMaybe [link]
=Ailidh [link]
*Kel-----Bel [link]
~skatetopunk [link]
!Japheree [link]
~tedgushue [link]
=WolfPrincess33 [link]
*Hector42 [link]
=DeepKick [link]
~JackOfSpades [link]
*ying-temptra [link]
*osyris [link]

This makes thirteen journal features for this month!  Not a bad effort, that.  Never in my wildest dreams did I imagine that I'd appear in over ten features in the one month let alone one!  Thank you to *Jezhawk, ~EtherealMaybe, =Ailidh, *Kel-----Bel, ~skatetopunk, !Japheree, ~tedgushue, =WolfPrincess33, *Hector42, =DeepKick, ~JackOfSpades, *ying-temptra, and *osyris for allowing me to grace their front pages.

--
H

"For everyone must see that astronomy compels the soul to look upwards and leads us from this world to another." -Plato (427-347 B.C.)
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