Category Archives: galaxies

Virgo Galaxy Cluster

Field centred at (platesolve by nova.astrometry.net):
RA: 12h 26m 15s
Dec:  +12° 52′ 36″
Up is -177 degrees E of N

M86/M84 Region of the Virgo Galaxy ClusterThe Virgo Galaxy cluster is a large nearby cluster of galaxies, that spans over 8 degrees of sky, and consists of over 1300 member galaxies. The cluster forms part of the Virgo super-cluster, of which the Local Group (with the Milky Way, M31, and M33) is an outlying member. 

The cluster is approximately 50MLy distant, and is comprised of three main clumps, with the image here displaying the M86 “subclump” of the “Virgo A” clump. M87 (Virgo A itself), is just off the frame to the lower left. The three largest galaxies in the image above are M86 (centre), M84 (right) and the interacting pair NGC 4435/4438 (left – otherwise known as “The Eyes”). These galaxies make up part of the famous “Markarian’s Chain” which is a series of bright galaxies extending off frame to the top left (north-east). Virgo Cluster - M86/M84 Region, Reverse AnnotatedAlso present in the image above are NGCs 4387, 4388, 4402, 4407, 4425, as well as several IC objects (including the odd blue irregular galaxy IC3355 at the top of the frame) and countless faint objects – some of which are highlighted in the annotated reversed image with galaxies highlighted from the SDSSR8 catalogue down to magnitude 20. 

“The Eyes” make an interesting pair – the smaller (NGC4435) is a barred lenticular galaxy (an intermediate between an elliptical and spiral). The larger NGC4438 is the most distorted of all galaxies in the cluster – with much of the disruption apparently caused by a past interaction with NGC4435. The detection of gas linking NGC4438 and M86 suggests that at some point all three galaxies have had past interactions. Additionally, there is some question as to whether the core of NGC4438 is powered by starburst (which may be as a result of the previous interactions), or whether it is home to an Active Galactic Nucleus, powered by a black hole. 

Data was taken over several nights during March and April 2017 from West Oxfordshire, UK using a WO FLT110, FLAT4 reducer, ST-200XM and Losmandy Titan. LRGB exposures were 240 (24x10min) : 75: 70 :70 (RGB in 5 min subs, 2×2 bin). Unfortunately, the flats didn’t reduce well here, so there was quite a bit of work in trying to eliminate gradients across the image – this may have restricted a little what I was able to pull out of the image data.

M31, NGC206 and the Bologna Catalogue

NGC206 Region in M31 - Lum ChannelPresented here is a bit of a “nonsense image” of the Andromeda Galaxy, M31, that I grabbed early in the evening of the 22nd Jan 2017. This was a quick run, mainly while I was waiting for another target to clear the tree near my observatory…!

However, even in an image like this, which only consists of 14x5min exposures through a luminance filter, there is lots to be explored – first it gives me a good idea about future plans for a mosaic (though this will have to wait until the autumn now, and may be a major undertaking…). It also gives a good view of NGC 206, which is a bright star cloud in M31, and I plan to image this alone at longer focal lengths later on. Also, it allows me to explore objects in the Bologna Catalogue 1.

NGC206 Region in M31, with Bologna Catalogue Globular Clusters AnnotatedThis catalogue  is not one that comes immediately to mind when talking about deep-sky objects – but it is a very specialised list describing globular clusters (GCs), candidate GCs and previous candidate GCs in M31. The up to date version of the catalogue is freely available on the Bologna Catalogue website and can be downloaded, manipulated and used as a source of information for the Annotate script in Pixinsight. Presented here in negative format is the south west region of M31, with overlaid markers for the confirmed GCs in the Bologna Catalogue v.5 (with associated V magnitudes) in red, as well as a few small PGC galaxies that loiter in the field marked in light blue. There are 181 marked objects alone in this field – most of which have been successfully captured using just a small 4 1/2″ refractor!

Image details:

ST2000XM, William Optics FLT110 + FLAT4 reducer
14x5min, L filter
Reduced and processed in Pixinsight

References

1. Galleti S., Federici L., Bellazzini M., Fusi Pecci F., Macrina S.: “2MASS NIR photometry for 693 candidate globular clusters in M31 and the Revised Bologna Catalogue (V.1.0)”, Astron.&Astrophys., 2004, 416, 917 (G04)

M33 – The Triangulum Galaxy

RA: 01h 33m 54.0s
Dec: +30° 40′ 15.8″
Up is -89.8°E of N
(Plate solve by nova.astrometry.net)
M33 - Triangulum GalaxyMessier 33 is a spiral galaxy in the constellation of Triangulum, and is sometimes called the Pinwheel  Galaxy, a name it shares with M101, It is the third largest member of the Local Group of galaxies with a diameter of about 60,000 light years; the two larger members being our Milky Way and the Andromeda Galaxy (M31). There is suggestion that M33 and Andromeda have experienced an encounter at some point in the past (and will do again in the future!).

M33 is one of the most distant objects visible to the naked eye, but it is a relatively diffuse galaxy, and so it’s visibility with the naked eye and through binoculars is strongly affected by light pollution and sky transparency – in this respect, M31 is far more visible to the naked eye. 

There are lots of H-II star forming regions within M33 that are visible as pinkish areas of hydrogen emission in the spiral arms. The largest of these is NGC604 which was catalogued independently of the galaxy core by William Herschel. This area is probably very similar to the Orion Nebula in many ways, and can be found to the north-east (upper-right) of the core of the galaxy (north is to the right in the images).

The images were all taken across several nights in November 2016 (7th, 28th, 29th) from West Oxfordshire with an SBIG ST-2000XM though a William Optics FLT110, all mounted on the Losmandy Titan. Exposures were as follows:

L:R:G:B
310 (31x10m) : 95 : 90 : 80 (RGB in 5m subs, 2×2 binned)
All exposures taken at -20°C.

Reduction and processing performed in Pixinsight and Photoshop. The processing of this object proved tricky. The galaxy largely fills the field and leaves relatively little background to work with in running DBE processes. This left several colour casts and gradients that I needed to manually remove within Photoshop – not an easy task…  

M33 HDR EnhancedAlso included here is a luminance only channel using the L channel data, that has been processed using HDR Multiscale Transform, Local Histogram Equalization and TGV Denoise to reveal to a greater extent the structure of the galaxy – in many ways this might be regarded as “over-processed”, but an interesting take on the galaxy nevertheless. 

M101 – Pinwheel Galaxy

Field centered at: RA: 14h 03m 12.6s, Dec: +54° 21′ 16.7″
Up: 178 E of N.

(plate solve from nova.astrometry.net)

The Pinwheel Galaxy, M101 is located in Ursa Major, and I found this a surprisingly tricky object to image – it has low surface brightness, with a lot of faint outlying regions. I also appeared to have some small issues with the flat fielding process here – there are a couple of very large dust bunnies in the raw data that haven’t quite been subtracted away and there’s a touch of clipping to deal with this. Add to this some faint colour gradients (attempted to sort out gradients!) and a couple of bright stars in the field and it became something very tricky to try and get right (and I’m still not 100% convinced that it’s truly there yet…).

The fainter galaxy to the right (east) of M101 is NGC5477, which is a dwarf galaxy at about the same distance (~20MLy). There are lots of fainter objects in the image as well: the brighter galaxy to the upper left of M101 for example is MCG+09-23-25, and there are also loads of other faint galaxies, galaxy groups and QSOs lurking in there. Using a solved fits file in Aladin is very instructive here!

I used fairly long exposure lengths (I was using the FLT110 at f7 here, a shorter focal length would be a major bonus in truth – at f4-5 this would be a much deeper image!). Exposure details are as follows:

WO FLT110 @ f7 on Losmandy Titan, ST2000XM cooled to -20C (images on 18 & 19-Apr-2015)
L: 4.5hrs (1×1)
R: 70min (2×2 binned)
G: 48min (2×2 binned)
B: 48min (2×2 binned)

The Luminance for the image was processed using a Lucy-Richardson deconvolution (3 iterations) using CCDSharp.

M101 - Pinwheel Galaxy in UMa (Luminance)

 

M101 - Pinwheel Galaxy in UMa (LLRGB)

M65, M66, NGC3628 – The Leo Triplet

RA: 11h 19m, Dec: 13°15′ (approx. centre)m65_m66_ngc3628_20061221.jpg
The famous Leo Triplet is a small group of three spiral galaxies (namely, M65 (NGC3623 – bottom-left), M66 (NGC3627 – top-left) and NGC3628 (right)) that is located about 35 million light years away between Theta and Iota Leonis. All three galaxies are readily visible in a small telescope, though NGC3628 tends to be the hardest of the three to spot. Additionally, the smaller galaxy NGC 3593 (not shown) may also be a member of this group.

This image was taken from the dark skies of Mid-Wales on December 21st, 2006 as a “quickie” before sunrise after a run on imaging the Cone Nebula (to follow in a later post) – it’s only about an hour of total exposure. A much longer imaging run would allow the faint surrounds of M66 and the “tidal tail” of NGC3628 to be brought out, but unfortunately, as is so often the case with imaging in the UK, the clouds came in for the next 5 nights leaving the telescope ready to go, but unable to actually take an image…