Wednesday, 13 August 2014

Mare Humorum (Sea of Moisture) & Gassendi

Hello again,

This is the third sketch completed over three consecutive nights.  And as often happens, the best was saved for last.

In November last year I did a sketch of Rimae Hippalus.  This area shows a series of what looks like co-centric riles.   When I did some research on this area after this Rimae Hippalus area, I came so see that there is a ‘mirror image’ set of riles to the north-west of Rimae Hippalus, Rimae Mersenius.  All of this happens along the shores of Mare Humorum.

As it turns out, this is no coincidence.   Both sets of riles are all related.  They are the resulting massive fracture lines that were formed when an enormous rock slammed into the Moon that formed Mare Humorum.  Both these rile systems are the fracture lines formed when the thin crust was smashed, much like the fracturing that forms when a stone or bullet slams into reinforced glass.  The terrible destructive force of that collision not only resulted in the crater being flooded by lava, but much of the resulting riles were also partially flooded.

Mare Humorum also has other treasures within its lava fields.  A pyroclastic deposit sits on the southern edge.  These areas are ancient remains of volcanic activity on the Moon!  And just west of this long extinct volcano is another volcanic anomaly, a dome.  Domes are volcanos that force their way to the surface, but not quite rupturing through.  Instead there is a ‘dome’ formed as the pressure from underneath pushed up causing a blister-like effect.  While doing this sketch, I noticed an odd ‘mountian’ close to the south western shore, very much out of place as it is well inside the lava fields.  It turns out that this ‘mountain’ is one such dome!

This entire area makes for magnificent examination.  This particular night turned out to have sensational seeing conditions.  This allowed me so reach the best resolution I’ve been able to achieve for over a year, with details as small as 2km in diameter.

However, the sensation that is this area is not limited to the history of rile system.  The crater Gassendi contains an astonishing series of riles within its floor.  The floor of Gassendi is a partially flooded one as the central peak of the crater is still visible.  But the resulting lava field is criss-crossed with a maze of riles.  Their curious structure could well be the result of collapsed lava tunnels.  However I am not convinced as yet that this is the case as these riles are over 3km wide.

Whatever the origin of this valley system, it makes for a very pretty filigree pattern inside Gassendi.

Object:  Mare Humorum & crater Gassendi.
Telescope:  C8, 8” SCT
Gear:  8mm Celestron Ultima LX, 250X
Date:  7th August, 2014
Location:  Sydney, Australia

Media:  Soft pastel, charcoal & white ink on A4 size black paper.

Below is the sketch of Rimae Hippalus, done in November last year, which is off the south-east edge of Mare Humorum, showing the rile system that reciprocates those pictured above.  You will see the crater Hippalus in both sketches that gives the reference point between both pieces.

Tuesday, 12 August 2014

Dawn over Gassendi

Hello again,

This night, while conditions didn’t allow for too high magnification, one striking feature demanded attention.  Very little of it was in illumination, but what was sunlit, made for a gorgeous subject.

Gassendi is a large crater on the northern shore of Mare Humorum.    Being dawn, its eastern face is brilliantly lit.  The crater floor is still in shadow and inky black.  Then, appearing as fragments of a shattered Moon, the highest peaks of its western rim and its central peak reaching out from the depths with fingertips to touch the first rays of the sun.

It was a challenge to depict the strong shadows.  And over the course of the two hours at the eyepiece, it was wonderful to witness the shadows and highlights change as the sun rose higher and higher.   For all the challenges, there is always something beautiful to behold.

Object:  “Dawn over Gassendi”
Telescope:  C8, 8” SCT
Gear:  8mm LVW, 250X
Date:  6th August, 2014
Location:  Sydney, Australia

Media:  Soft pastel, charcoal and white ink on A5 size black paper.

Monday, 11 August 2014

Early morning Copernicus

Hi all,

We had a great spell of clear nights last week that allowed me to do three sketches of the Moon over three consecutive nights.  The first was a revisit of Copernicus that I had sketched the month before but on a more advanced phase.

On this particular night, the phase was two days after Copernicus’ appearance on the terminator.  This made for a shallower angle of incidence of sunlight so many more of the smaller secondary craters to be visible.  Conditions on the night were not brilliant, and magnification at 250X still saw a lot of atmospheric thermal current distortion to the image, limiting how small the details I could see.  With a bit of perservierence a lot of these secondary craters could be made out.  You will find information on the formation of these ‘secondary impacts’ in my earlier write up on Copernicus below.

Being sooner after sunrise over Copernicus, the shadow structure made for a more dramatic lunarscape.  Longer shadows, greater contrast, and a visual feast.  The surrounding craters that accompany Copernicus also adding to the drama with there illumination.

Object:  “Early morning Copernicus”
Telescope:  C8, 8” SCT
Gear:  8mm LVW, 250X
Date:  5th August, 2014
Location:  Sydney, Australia
Media:  Soft pastel, charcoal and white ink on A4 black paper

Friday, 8 August 2014

M22 Globular Cluster - the magnificent little brother

Hi all,
This was the second sketch I completed at this year’s Astrofest.

M22 is a true jewel of the night sky.  This giant globular cluster from a dark site can be a naked eye object as well.  It is large enough for even smaller telescopes to resolve its multitude of component stars, to reveal its large and intense core.

M22 is beautiful in my 17.5” scope.  It is very different from Omega Centauri and 47Tuc – could even describe it as the ‘runt’ of the giant globulars as its core is not as busy as its bigger brothers.  But the component stars of its core are absolutely brilliant, arranged in so many signature patterns.  It is slowly turning into a favourite of mine with its understated brilliance, loud without being overbearing presence, and sitting on a magnificent carpet of the Milky Way glow.

I won’t say much here.  I’ll let M22 do its own quite whispering of its magnificence.  Yeah, I think one firm fav of mine now…

Object:  M22 globular cluster
Scope:  17.5” push-pull Karee dobsonian
Gear:  22mm LVW, 91X
Location:  Linville, Queensland, Australia
Date:  24th July, 2014
Media:  Soft pastel and white ink on A4 size black paper

Duration:  approx. 2.5hrs

Saturday, 2 August 2014

The Ink Spot - Light vs Dark

Hi all,

This was the first sketch I completed at Astrofest.  I've been wanting to sketch this beautiful dark nebula ever since I first laid eye on it some three years ago.  This dark nebula, B86, goes by the popular name of "The Ink Spot".  It sits smack bang in the centre of the densest star cloud in the whole sky, the Cloud of Sagittarius.  And what sets it off even more is B86 has a gorgeous bright open cluster right next to it, NGC 6570.  Both objects are more-or-less the same size as each other, even though both are not very large themselves.  But it is the juxtaposition of these two very different objects against the blaze of the Milky Way that makes this pair a spectacular pairing.

Dark nebulae are clouds of dust and gas that are drifting through the Milky Way galaxy.  Many of these conglomerations of dust and gas do end up being formed into stars and planets, but most just end up forming the fabric of the galaxy.  In fact, the stars that we see actually only form a small percentage of the actual mass of galaxies.  By far the greatest amount of a galaxy's mass comes from this very dust and gas.  The Ink Spot is a small patch of cloud.  It is a very opaque nebula too.  Dark nebulae are categorised according to their opacity, or how dark they are.  The scale of opacity goes from 1 (very tenuous) through to 6 (very opaque).  While the opacity of The Ink Spot may be a 5, it is because that it sits in the Cloud of Sagittarius that makes is a striking object.

The little open cluster NGC 6520 really works very well in setting off B86.  Open clusters are groupings of stars that are all related to each other having been formed out of the same parent cloud of gas and dust.  Evidence for this is seen in the spectra of the stars displaying the same chemical make up.  The brothers and sisters of our own Sun have been identified this way, with the same chemical signature as our Sun having been identified in several close by stars even though the Sun's 'siblings' have long drifted off away from each other.  Open clusters are loose groupings too, so even though they formed from the same source, their gravitational connection to each other is not strong enough to keep the group together for too long.

For me, this tiny patch of sky is one of my most favourite.  Tiny and oh so precious.  Brilliant, dark, stark, ghostly.  All in one.  Gorgeous.

Object:  The Ink Spot, B86 & NGC 6570
Telescope:  17.5" push-pull Karee dob
Gear:  13mm LVW, 154X
Location:  Linville, Queensland, Australia
Date:  24th July, 2014
Media:  Soft pastel, charcoal and white ink on A4 size black paper.
Duration:  approx. 3hrs