Backyard Astronomers Capture Impact on Jupiter

Video

With Earth having passed between Jupiter and the Sun on March 8th, we have some of the finest observations of the Jovian planet.  It’s only normal to have a few backyard astronomers setting their sights on the largest planet (myself included, still got unprocessed videos from March 27th).  However Gerrit Kernbauer was lucky enough to record an unusual event: something slammed into Jupiter!

Phil Plait of Bad Astronomy reported that Gerrit Kernbauer with his 20cm telescope in Austria, captured on March 17th what appeared to be an impact of sort.

The issue was to confirm that it was an actual impact, and not some other natural effect or electronic noise in his setup.  What better than to have a second independent observation, and that came from John McKeon with a 28cm telescope in Ireland.

Maybe I should go take a look at my videos on Jupiter from March 27th just in case…  Actually with my 80mm telescope,  I don’t think it would have picked up such an impact.

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Messier 38 and NGC1907 – Open Clusters in Auriga

Image

Following my previous post on Messier 36, a simple 2 degree slew of the telescope and I was centered on Messier 38 (NGC1912).  This open cluster measures 21 light years across ( 21′ apparent) or twice the size of M36.  It is also much older than M36 which is why you’ll find less hot blue stars within the group if you compare with M36.

Just half a degree below is an older and smaller open cluster NGC1907.  While some have speculated that they are locked together (a binary cluster?) this cluster is 500 million years old, almost twice the age of M38, hence were formed at different periods and most likely from different molecular gas.  This is just a chanced fly-by with no interactions.

Open Clusters Messier 38 and NGC1907

Open Clusters Messier 38 and NGC1907

Skywatcher 80ED
Canon Digital Rebel XTi (400D)
30 x 30sec (ISO 800)
Registration with IRIS
Post-Processing with GIMP

Messier 36 – Open Cluster in Auriga

Image

Open Cluster Messier 36 (NGC 1960) is located in the Auriga constellation.  Located about 4,100 light years from Earth, and 14 light years across, it has at least 60 members.  It is very similar to the Pleiades (M45) and if M36 was at the same distance (M45 is 10 times closer) it would be of similar magnitude.  Two other open clusters from Messier’s catalog are located nearby: M37 and M38.  The stars in the cluster are of spectral type B2, and fairly young: 25 million years.

Open Cluster Messier 36. Skywatcher 80ED, Canon 400D 18x30sec

Open Cluster Messier 36. Skywatcher 80ED, Canon 400D 18x30sec

The blue-ish stars contrast with the older yellow and orange stars in the background.  This can be further enhanced by using the SBLUR function in IRIS to selectively blur and enhance the colors of bright stars.  While the colors are exaggerated in the image below, it is nevertheless interesting to see the vast diversity of stars and their color.

Open Cluster Messier 36. Skywatcher 80ED, Canon 400D 18x30sec

Open Cluster Messier 36. Skywatcher 80ED, Canon 400D 18x30sec (SBLUR for colour)

Telescope: Skywatcher 80ED
Camera: Canon Digital Rebel XTi (400D)
Exposure: 18 x 30sec (ISO 800)
Date: 18Mar2016

Composition with Landscape

I’ve mentioned it before that you don’t need a fancy telescope and tracking equatorial mount to get into astrophotography.  Simply a camera on a tripod with a short focal lens can do wonders, especially with the high ISO settings in new cameras. A single 10 seconds exposition can reveal lots of stars, however to capture more photons a longer exposure is not better as the stars will become streaks.  But one can easily improve the image and get better signal/noise ratio by stacking multiple images.

However, there is one drawback to stacking multiple exposures if you decide to also capture the landscape: Earth rotates, therefore the sky moves while the landscape stays still.  If you align the images using the stars, then the landscape becomes a blur.  Not the end result that we want.  Luckily a quick composition with two layers and a mask solves everything.

Below is a single 10 seconds exposure at ISO 800 with a 17mm F4 lens; you have the landscape with city lights and the stars above.  Yes that is Orion…

Single 10sec exposure (ISO 800)

Single 10sec exposure (ISO 800)

In order to improve my signal, I worked with IRIS to align and stack 5 frames, this reveals many more stars, but also amplified the light pollution.

Aligning and stacking 5 images. More stars appear.

Aligning and stacking 5 images. More stars appear.

Luckily within IRIS there is a function to remove sky gradient.  The algorithm takes a series of sample points and attempts to make the sky uniform.  Not bad, the images are not a hopeless case.

Removing the sky gradient with IRIS

Removing the sky gradient with IRIS

As mentioned above, the alignment was performed with the stars, hence the background is now blurring.  Below is a close-up.

But when aligning on stars, the landscape blurs.

But when aligning on stars, the landscape blurs.

That is just 5 images, stack a much larger quantity or with more time between frames and it will only get worse.  It becomes pointless to shoot with the landscape if the end result is blurry.  Luckily working with layers in a photo editor can easily solve the issue.  We want to keep the stars from the stacked image, but the landscape from a single frame.  Follow these easy steps:

  1. Load into your base layer one of you single frames.  This is what will be used for the landscape.
  2. Load into a new layer your stacked image.  As your stacked image contains more and brighter stars select to Lighten Only instead of normally adding both layers.  You can play with the brightness of the stacked layer, and/or darken the base layer to get the desired blending.
  3. Create a mask to the stacked layer such that the blurred landscape is not permitted to show through.  See image below, I simply grabbed the airbrush and blackened the landscape area in the mask such that it will not show through the layer.  Note that the I only edited the mask, not the image itself.
Creating a mask for my layer: white is transparent, black will block

Creating a mask for my layer: white is transparent, black will block

The end result, is improved image of the sky, and a landscape that is still sharp.

Both layers added with the mask

Both layers added with the mask

Below is a comparison the composition with stack and layer (left) and a single shot (right).  We are able to achieve both of our goals of getting more stars (more signal) while keeping the landscape from becoming a blur.

Comparing the composition with layers (left) and single shot (right)

Comparing the composition with layers (left) and single shot (right)

And why not take some time to identify some key features in the image.

Constellations Orion and Taurus above the landscape.

Constellations Orion and Taurus above the landscape. (Click to open)

Changes in Lunar Size

Image

While doing some organization in my astrophotos I came across a picture composition that I created back in September 2015 following the Super Moon Lunar Eclipse, but which I never posted.

I had selected two Lunar Eclipse photos that I had taken with the exact same equipment, but on different year and wanted to see the difference in size with this “Super Moon”.  Was it really that much bigger…

Lunar Size Comparison Between February 2008 and September 2015 Lunar Eclipse

Lunar Size Comparison Between February 2008 and September 2015 Lunar Eclipse
– Benoit Guertin

The Moon’s orbit is elliptical and eccentric which causes the Moon’s distance to vary by 50,200km from perigee (closest) to apogee (furthest).  The end result is a 12% change in apparent diameter as viewed from Earth.  The above image only shows a 7% difference as while the background Moon was taken at perigee (famed Super Moon) the foreground was an arbitrary reference of the February 2008 lunar eclipse.

Telescope: Skywatcher 80ED (600mm)

Closest Comet in 246 Years

Status

There’s a good article in Sky & Telescope on comets 252P/LINEAR and the smaller fragment P/2016 BA14, explaining observation opportunities.  A comet hasn’t passed this close to Earth in 246 years.   And as it does the wonderful green halo around 252P/LINEAR  is sure to grow but will probably remain around magnitude 6.

As the comet flies by Earth it will sweep through the constellations quickly and then fade back to below magnitude 12 in short order.  Therefore try not to miss it.

Comets to Pass Near Earth

Status

Two comets will pass near Earth between March 21st and 23rd. Comets 252P/LINEAR and P/2016 BA14 will pass between 14 and 9 lunar orbits with the Earth.  As both comets  have similar orbits they most likely broke in two following a close encounter with a planet’s gravity.

252P/LINEAR  has surprised everyone by brightening to magnitude 6 as it was predicted to remain in the 12-14 range.  Presently accessible to folks in the southern hemisphere it will be visible to northern observers after the Earth fly-by.