Monday, 20 October 2014

GALAXY - M31 Andromeda

The great galaxy in Andromeda

This is what M31 looked like 2.5 million years ago. Shot with a modded 7D through a 60mm refractor @ f/6.2 mounted on an EQ6.

An hour's worth of exposure in 30 shots of 2 minutes each at ISO 1600. I was surprised to see that despite the high ISO the stars show some colour, even in heavily polluted skies. 

M31 - The great galaxy in Andromeda

Saturday, 7 June 2014


A rain shower shortly before 9pm on June 4th produced this particularly large rainbow @ 39° above horizon

A rainbow appears when drops of rain split the Sun’s white light in Red / Orange / Yellow / Green / Blue / Indigo / Violet (order from the top down). There are always two rainbows: the primary and the much fainter secondary (43% less light spread over 1.8x the angular distance of the primary). The secondary is turned around, so that the rainbows’ two red bands face each other. The distance between them is 9°.

Very large rainbow on June 4th, 2014
(Sun at 2.91° above horizon)

I’ll spare you the math, but the diffraction angle for violet is around 40° and that of red is 42° - this tells us that the thickness of a rainbow is roughly 2 degrees (2.36° to be more precise). The center of the rainbow is the antisolar point – the point exactly opposite the Sun. It is always below the horizon and goes as far below as the Sun is high in the sky. This means that larger rainbows will appear when the sun is low, after sunrise or in the evening. When this particular photo was taken, the sun was about 3° in the sky, making this one of the largest rainbows possible.

Three zones of luminosity can be observed: the brightest under the primary (to the right in the image below), the darkest in between the two rainbows (Alexander's band), and the third above the secondary (to the left). Light is scattered in such a way in between the primary and the secondary so that it doesn't reach the observer. There are other rainbows there - but seen by other people.

Alexander's band - Rainbows seen by others

Under the right conditions, the primary bow displays several other greenish-purple bands of color below its lowest, purple fringe. They are called “supernumeraries” (not present in my picture)

Detail of the primary rainbow - Alexander's band is to the right

Detail of the secondary rainbow - Alexander's band is to the left
The secondary bow has 43% less light spread over 1.8x the angular distance of the primary 
making it considerably fainter

Monday, 2 June 2014

PLANET - Saturn

Twenty days after opposition

A hundred or so shots of Saturn through a C8 at 2m10 focal length. With a little good will you can see a hint of the Cassini division and the Northern band currently visible.

Saturn on May 31st 2014

Saturn is currently showing us the northern side of its rings with a tilt of about 21.5°, which will be widening until 2017 or so, and in about 10 years time they will again (diss)appear edge-on, like they did in 2009.

These are shots of Saturn taken over time, showing the variation of the ring's inclination:

Tilt of Saturn's rings over 7 years

Sunday, 1 June 2014

THE SUN - Sunspot AR 2075

Little activity at solar maximum

This solar maximum is one of the weakest since we started gathering data. Here is sunspot AR 2075 on May 29th.

AR 2075

Sunday, 25 May 2014


Large globular cluster in Serpens

It's one of the larger known clusters - light takes 100 years to travel its radius - and harbours as many as half a million stars. 

It lies some 25k ly away: this is an image from when the Bering strait didn't exist and Asia was connected to the American continent.

M5 - Globular cluster in Serpens

100% crop

CLUSTER - M44 Beehive

Open cluster in Cancer 

quite bright at mag 3.7 and spanning about 100 arc minutes which is about three times the size of the Moon. It has 1000 stars, with the most massive concentrated towards the centre.

M44 - Beehive cluster

M44 - Beehive Cluster

Its distance has been calculated at 577 light years, meaning that the light you see in the pictures below left the cluster in 1436 and spent all this time travelling towards my camera. 

M44 - Beehive Cluster

The picture is a single 30s exposure on a Canon 7D through a 200mm Sigma APO, all mounted on a EQ5. The field is big - 7 degrees by 4 - and if you look carefully there are many small distant galaxies all around the cluster

THE SUN - Sunspots AR 2060, 2061, 2066

Apparent dimensions comparable to Jupiter

Stacked a 1.7x extender and a 2x barlow on a 60mm refractor (f/20).

AR 2060, 2061, 2066 - 18V14

Sunday, 18 May 2014


1.2m focal length @ f/20 on APS-C sensor

Stacked a 1.7x extender and 2x barlow on a 355mm f/5.9 refractor. Camera is a 7D.

Apparent dimensions of the Sun, Jupiter and Mars


Sunday, 11 May 2014

THE MOON - Partial eclipse

Photos were taken at 3 minute intervals over a period of about an hour with a 60mm, f/11.8 APO refractor on an APSC sensor.

No alignment. (duh)

Partial Lunar Eclipse 2013

GALAXY - M33 Triangulum

M33 is 50 000 light years across. 

This means that In the time light takes to travel from one end to the other, a (potential) humanoid species would have time to evolve from Neanderthals to individuals capable of recognising such light as being that of faraway star.

It's a spiral galaxy sometimes called the "Pinwheel", despite SIMBAD assigning this nickname to M101. Diffuse source at the extreme limit of naked-eye visibility, it's one of the critical sky-marks of the Bortle Dark-Sky Scale (2001).

It's 3mio ly away: when the light below left the galaxy, the first humans were evolving thanks to a cooling of Earth's climate.

M33 - Triangulum Galaxy
Observation data (J2000 epoch)
Pronunciation /traɪˈæŋɡjʉləm/
Constellation Triangulum
Right ascension 01h 33m 50.02s[1]
Declination +30° 39′ 36.7″[1]
Redshift -0.000607 ± 0.000010[1]
Helio radial velocity -179 ± 3 km/s[2]
Galactocentric velocity -44 ± 6 km/s[2]
Distance 2,380 to 3,070 kly (730 to 940 kpc)[3][4]
Type SA(s)cd[2]
Mass 5 × 1010[5] M☉
Number of stars 40 billion (4×1010)[6]
Apparent dimensions (V) 70.8 × 41.7 moa[1]
Apparent magnitude (V) 5.72[1]