Lower Orion Constellation

Just when you think you have a good “recipe” to process astronomy images taken with your gear, things don’t quite work out and you end up spending three evenings trying different settings, techniques and steps because you know there’s a better image waiting to be teased out.

M72 and Lower Orion Constellation

M72 and Lower Orion Constellation – Benoit Guertin

The image above (click for a full frame) is as much as I can stretch out from the lower half  of the Orion constellation and nebula with a 20 seconds ISO 800 exposure on 85mm F5.6 Canon lens from my light polluted backyard.

Below is the sky chart of the same area showing the famous Orion Nebula (blue and red box) and the Orion belt with the three bright stars Alnitak, Alnilam and Mintaka.  What is unfortunate is there are lots of interesting deep space nebula structures that glow in the hydrogen-alpha spectral lines of near infra-red, but all photographic cameras have IR filters to cut on the sensor those out.  That is why many modify the cameras to remove the filter, or get dedicated astro-imaging cameras.

Sky Chart - Lower Orion with nebula and open star clusters

Sky Chart – Lower Orion with nebula and open star clusters

Now, back to the main topic of trying to process this wide field image.  I had various issues with getting the background sky uniform, other times the color just disappeared and I was left with essentially a grey nebula; the distinctive red and greenish hue from the hydrogen and oxygen molecules was gone.  And there was the constant hassle of removing noise from the image as I was stretching it a fair bit.  I also had to be careful as I was using different software tools, and each don’t read/write the image files the same way.  And some formats would cause bad re-sampling or clipping, killing the dynamic range.

Below is a single 20 seconds exposure at ISO 800.  The Orion nebula (M72) is just barely visible over the light pollution.

orion_2017-02-27_original

Original image – high light position for 20 seconds exposure

The sky-flog (light pollution) is already half way into the light levels.  Yes, there are also utility lines in the frame.  As these will slightly “move” with every shot as as the equatorial mount tracked I figured I could make them numerically disappear.  More on that later…

Light levels of a 20 second exposure due to light pollution

Light levels of a 20 second exposure due to “sky fog”

The longer you expose, the more light enters the camera and fainter details can be captured.  However when the background level is already causing a peak mid-way, longer exposures won’t give you fainter details; it will simply give you a brighter light-polluted background.  So I needed to go with quantity of exposures to ideally reach at least 30 minutes of exposure time. Therefore programmed for 100 exposures.

Once the 100 exposures completed, I finished with dark, flat and offset frames to help with the processing.  So what were the final steps to reach the above final result?   As mentioned above, I used three different software tools, each for a specific set of tasks: DSS for registration and stacking, IRIS for color calibration and gradient removal and finally GIMP for levels and noise removal.

  1. Load the light, dark, flats and offset images in Deep Sky Stacker (DSS).
  2. Perform registration and stacking.  To get rid of the utility lines as well as any satellite or airplane tracks, the Median Kappa-Sigma method to stack yields the best results.  Essentially anything that falls out of the norm gets replaced with the norm.  So aircraft navigation lights which show up only on one frame of 100 gets replaced with the average of all the other frames.  That also meant the utility lines, which moved at every frame due to the mount tracking, would vanish in the final result.
  3. As my plan is to use IRIS to calibrate colors, where I can select a specific star for the calibration, I set the no background or RGB color calibration for DSS.
  4. The resulting file from DSS is saved in 16-bit TIF format (by default DSS saves in 32-bit, but that can’t be opened by IRIS).  I didn’t play around with the levels or curves in DSS.  That will be dealt later, a bit in IRIS, but mostly in GIMP.
  5. I use IRIS to perform background sky calibration to black by selecting the darkest part of the image and using the “black” command.  This will offset each RGB channel to read ZERO for the portion of the sky I selected.  The reason for this is the next steps work best when a black is truly ZERO.  While IRIS works in 16-bit, it’s actually -32,768 to + 32,768 for each RGB channel.  If your “black” has an intensity of -3404, the color calibration and scaling won’t be good.
  6. The next step requires you to find a yellow Sun-like star to perform color calibration.  As a white piece of paper under direct sunlight is “white”, finding a star with similar spectral color is best.  Sky chart software can help you with that (Carte du Ciel or C2A is what I use).  Once located and selected the “white” command will scale the RGB channels accordingly.
  7. The final step is to remove the remaining sky gradient, so that the background can be uniform.  Below is the image before using the sky gradient removal tool in IRIS.
  8. Image before removal of sky gradient in IRIS

    Image before removal of sky gradient in IRIS

  9. Once the sky gradient is removed, the tasks in IRIS is complete, save the file in BMP format (will be 16-bit)  for the next software: GIMP
  10. The first step in GIMP is to adjust light curves and levels.  This is done before any of the filers or layer techniques is performed.
  11. Then I played around with the saturation and Gaussian blur for noise reduction.  As you don’t always want the transformations to take place on the entire image, using layers is a must.
  12. For the final image above, I created two duplicate layers, where I could play with color saturation, blurring (to remove the background noise) and levels until I got the desired end result.  Masks are very helpful in selecting what portion of the image should be transparent to the other layers.  An example is I wanted a strong blur to blend away the digital image processing noise, but don’t want a final blurry night sky.

EXOPLANET SERIES – TRAPPIST-1

On Wednesday NASA made headlines by announcing that researchers had detected seven exoplanets orbiting a dim dwarf star.  These exoplanets are determined, based on measurements, to be approximately Earth-sized solid planets and three happen to fall in the “Goldilocks Zone” where water could exist in liquid form; not too hot, not too cold.  Lots of people started speculating that in a few years we’ll find out if one of those planets harbors life.  However that is just plain crazy-talk.  The importance of this discover is that complex exoplanet systems do exist; the Solar System is not an exception, and that life is also not an exception.

The TRAPPIST-1 system

The TRAPPIST-1 system contains a total of seven planets, all around the size of Earth. Three of them — TRAPPIST-1e, f and g — dwell in their star’s so-called “habitable zone.” [NASA/JPL]

0.60m Ritchey-Chrétien Reflector [TRAnsiting Planets and PlanetesImals Small Telescope–South / ESO]

0.60m Ritchey-Chrétien Reflector [TRAnsiting Planets and PlanetesImals Small Telescope–South / ESO]

The TRAnsiting Planets and PlanetesImals Small Telescope–South made the discovery back in May 2016 of three exoplanets around the small star.  But it was with the help of larger telescopes and the space-based Spitzer telescope that the count increased to seven and their orbits could be confirmed.  What I find interesting is the initial discover was done by a relatively “small” 0.60m telescope.  OK not your typical backyard astronomy gear, but scale that down by 1/3 and you have equivalent optics for about $3000.  Add a mount and CCD and for $10,000 you could probably have your very own exoplanet hunter!

Back to the crazy-talk of finding life in this exoplanet system… Anyone who has studied the history and formation of the Solar System knows that there have been a series of unlikely events that have led to where we are today.  Starting with the Sun, probably a 3rd generation star, where heavy elements like Calcium and Iron necessary for life as we know it were produced by previous stars and supernovas that used to exist in this spot of the galaxy we now occupy.  All elements beyond Hydrogen are produced by stars, either through fusion or when they dramatically explode as supernovas.  The atoms making up the air, the trees, the oceans, ourselves were not created in our Solar System during its formation.  The Sun is currently only generating Helium and Lithium out of Hydrogen through the wonders of fusion.  All the heavier atoms within us were created by previous stars that no longer exist.  Hence for solid Earth-like exoplanets to exists there needs to have been one to two previous generation of stars in the region.

An alien race observing our Solar System would surely first spot Jupiter.  One could almost say that it characterizes our home in this part of the galaxy.  With its strong gravity this gas giant plays the vital role of neighborhood vacuum cleaner.  It is either mopping up or launching away asteroids and comets that would otherwise impact Earth, bringing relative calm to the inner Solar System.  If Earth was constantly bombarded by solar objects, there is no way that life could suitably evolve from slimy unicellular organisms.  It took 3 billion years for multi-cellular organisms to show up once life appeared on Earth.  If cataclysmic comet and asteroid impacts are a frequent occurrences, then there is little chance that complex organisms would come to be.

Looking at another element, TRAPPIST-1 is described as an ultra-cool dwarf star just shy of 40 light years from Earth in the constellation Aquarius.  If we forget that it’s a fraction of our Sun’s size and brightness (hence heat generation), it is relatively young at 1 billion years old.  So while there may be three planets that could be habitable, life may not have even begun yet.  Our own Sun is 4.3 billion years old, and the animals we see around us have only been around for the last 14-16 million years.  So what could be in a 1 billion year old planetary system? Assuming all the ingredients are there for life to exist, you probably only have bacterial soup.

Now, my article was getting long, and I wanted to cover many more subjects, too many for a single article.  Hence I’ve decided to break them out into the EXOPLANET SERIES and will publish them over time.

 

Fast Moving Comet Before Sunrise

If you are able to get out of bed early and the sky is clear, equipped with binoculars you should be able to catch a fast-moving comet as it swings by Earth at about 32 lunar distances over the next few days.  The best time is just prior to sunrise as the comet will be higher in the sky in the East.  Use Jupiter as well as bright stars Vega and Arcturus to get your bearings.  With each day the comet will rise earlier and will appear higher in the sky as the chart below shows; comet position at 5am for the next week.  However it will diminish in brightness as it moves away from Earth on after February 11th.

Comet 45P over the next few days starting Feb 10th.

Comet 45P over the next few days starting Feb 10th.

This isn’t the closest a recording of a comet passing near Earth, but it does make it to the 8th spot since modern observation and have been keeping track of near Earth objects (1950).  Back in August 15 2011, it happen to pass even closer, only 23 lunar distances, making it also the 5th closest comet approach.

With a storm system moving up the eastern edge US and Canada, my chances of getting any clear morning sky is pretty slim…

Downloadable PDF Sky Chart: 45p_feb2017_chart

Tomorrow Evening: Moon, Mars and Venus

Great photo opportunity tomorrow evening, January 31st, with a thin crescent Moon in a close formation with Mars and Venus.  As the sky darkens simply look between South-West and West and you won’t miss them.  However don’t wait too late, by 9pm they will have disappeared below the horizon.

Early Evening Sky (7pm) - Look WSW for this close formation

Early Evening Sky (7pm) – Look WSW for this close formation

The Moon will be a thin crescent.  Here it is as photographed of the Moon tonight at 5:40pm just a little less than 3 days old.

Crescent Moon - 30-JAN-2017 (5:40pm)

Crescent Moon – 30-JAN-2017 (5:40pm)

No high-resolution photo for this one.  Took it quickly through an open window simply by hand-holding the telescope, and using Venus to quickly find focus through the camera view-finder.

Skywatcher 80ED
Canon XTi (1/50s at ISO400)
Registax6 to align, stack and wavelet on the best 3 frames (out of a dozen)

2017 Product – Meade EclipseView

With the total solar eclipse scheduled for August 21st, expect to see new lines of products catering to the novice observer wanting to get up close with the event.  Meade has recently announced the EclipseView product line for April 2017 which includes a binocular, a small refractor and three small reflector telescopes specifically for those wanting to experience the eclipse but with a limited budget and beginner experience.

Meade EclipseView [Meade]

Meade EclipseView [Meade]

The product line offers the following models, all equipped with removable white-light solar filter required to view the sun at all times.

  • 10×50 Binoculars
  • 60mm f/13.3 Refractor (includes 12.5 and 4mm eyepieces and 2x barlow) with an AZ mount
  • 76mm f/9 Reflector  (includes 26 and 6.3mm eyepieces and 2x barlow) with an AZ mount.
  • 82mm f/3.7 Reflector (includes 26 and 9mm eyepieces and 2x barlow) in a compact table-top mount
  • 114mm f3.95 Reflector  (includes 26 and 9mm eyepieces and 2x barlow) in a compact table-top mount

Of the bunch, only the 114mm has the better parabolic mirror, the others opting instead for the simpler spherical mirror.  Therefore the 114mm will provide a sharper view edge to edge, especially a high magnification.

These aren’t new telescopes from Meade, but existing models from their Infinity, Polaris and LightBridge Mini Series kitted for solar observation.  While Meade advertises that these telescopes can also be used at night to view the Moon, planets and the stars, you’ll want to get a red-dot view finder to replace the existing solar pin-hole finder.

Of course you can also add the appropriate solar filter to any telescope, no need to limit yourself to the above gear.

[Meade]

 

Processing RAW Cassini Spacecraft Images

Did you know that you can get access to the latest RAW images from the Cassini spacecraft directly from the NASA and JPL website?  Not only will you have first look at some stunning images of Saturn, the rings and the Moons like this one below from January 16th.  Click the image below for more information from NASA/JPL on that specific photo.

Daphnis making waves - Cassini spacecraft Jan. 16, 2017 - JPL/NASA

Daphnis making waves – Cassini spacecraft Jan. 16, 2017 – JPL/NASA

But you can also download raw images to try your luck at processing.  For this exercise I selected these series of pictures of the strangely perfect hexagonal-shaped storm on Saturn’s north pole.

Downloaded raw image set

Downloaded raw image set

These are images taken with different filters by the wide field camera, and I noted in an Excel file some information on each image, most importantly which filter was used.  Both the narrow and wide CCD on Cassini operate with two filter wheels, hence each image will always list two filters.  For those surprised at the rather “small” 1 mega-pixel camera, keep in mind the spacecraft was launched nearly 20 years ago, and development started in the 1980s.

There is a very detailed document on how to use, calibrate and process the images found at the following link.  But for what I wanted (quick processing) I only needed to find out which filters were the closest to an RGB setup.

Cassini ISS Broadband Filters

Cassini ISS Broadband Filters

Luckily this is well documented, and found them with the BL1, RED and GRN filters.

The image below is a quick addition of those 3 respective images assigned to red, green and blue channels.  The resulting image would be somewhat near the real colours, but I did not take any time to calibrate, hence they are probably a little off…

Saturn with normal RGB assignment (close to real colours)
Saturn with normal RGB assignment (close to real colours)

I also decided to try something that would provide a little more contrast and dive a little into the atmosphere and went with a IR-Red-Blue for RGB assignment by using a one of the narrow-band filters.

Cassini ISS Narrow Band Filters

Cassini ISS Narrow Band Filters

Saturn with IR, Red and Blue for RGB assignment

Saturn with IR, Red and Blue for RGB assignment

Both images above have not be calibrated, stretch or adjusted other than combine the raw images from Cassini.

The NASA/JPL site even has a section for amateurs to submit their photos and host a gallery to see what others have done.

References:
Cassini NASA/JPL site
Cassini Imaging Science Subsystem (ISS) Data User Guide

Comet 45P/Honda-Mrkos-Pajdusakova

It wasn’t easy but on Friday the weather cooperated and I was able to capture a glimpse of comet 45P/Honda-Mrkos-Pajdusakova.  That’s if you consider -10°C outside temperature to set-up a telescope and operate a laptop cooperation from Mother Nature.

In my previous post I gave myself a 2-day challenge to capture this comet as it was essentially the last few days at a decent magnitude 7 brightness before becoming non-observable as it swings around the sun over the coming weeks.  And when it returns to the northern latitude sky in mid-to-late February it will be dimer at magnitude 10.  In the image below, I labeled some of the brighter stars with their visual magnitude as reported by the Tycho-2 catalog.

Comet 45P/Honda-Mrkos-Pajdusakova

Comet 45P/Honda-Mrkos-Pajdusakova – around magnitude 7 on January 6th, 2017

I had a very small window of about 30 minutes to make any observation and photograph it.  The challenge started with setting up without polar alignment; the sky was still too bright to locate Polaris,  and instead relied on the position of Venus to align the mount.  As it was still twilight, I was limited to short exposures to keep the histogram on the left half on the camera and to make out a star from the background sky.  I actually started at ISO 400 with only 1 second exposure while adjusting the focus around Theta Cap (magnitude 4).  And as the minutes ticked by I was able to slowly increase my exposure as the twilight darkness permitted.  With neighboring trees, and rooftops coming into view I had to grab as many frames as possible. In the end I got 14 images with 6 seconds exposure at ISO 800 before calling it quits.

With such short exposures no chance of capturing any comet tail, but the green halo is unmistakable comet.

I hope to capture a few more comets this year.

Skywatcher 80ED
Canon XTi (450D)
14 x 6sec (ISO 800)
Registered and stacked with DeepSkyStacker.  Post-processing with GIMP.