Two nights of H-Alpha deep-sky imaging recently and in both cases this had the advantage of allowing imaging despite a bright moon being present.
This was also the first time I got to use a new adaptor which connects the threaded drawtube of the FLT110 to the corrector/reducer. This appears to have reduced the amount of vignetting present and potentially dealt with a source of internal reflections, but more importantly it has eliminated a potential source of flexture by removing the 2″ nosepiece from the imaging train.
The first image is of the Crescent Nebula (NGC6888) in Cygnus (image centered at RA 20h 12m 08s, Dec +38° 19′ 44″). The Crescent is an example of a Wolf Rayet nebula – the bright star HD192163 (also WR136, centre) is a massive star nearing the end of its short life. When becoming a red supergiant several hundred thousand years ago, it blasted away a shell of material weighing about 5 times the mass of our sun. This shell of material is impacted by the fast stellar wind, and excited by X-rays from the star’s surface, causing the glowing shell of gas we see today.
The image above consists of 11 x 20min exposures taken on the night of the 8th/9th September 2017, using an ST2000XM, WO FLT110 at f5.6 and an Astrodon HA filter. These were all taken with the moon at ~85%, which shows that the H-Alpha filter did a great job of filtering out the unwanted moonlight, and letting the required wavelengths pass.
The second image is another region in Cygnus containing Simeis 57, the Propeller Nebula (image centred at RA 20h 16m 05s,
Dec +43° 41′ 05″). This is often mislabelled as DWB111, whereas that is only the southern (lower) half of the “propeller” (the other half is DWB119). Not a lot is known about the nebula – there isn’t a definitive distance, though it’s suspected that it is reasonably nearby, and it’s somewhat odd that given it’s distinctive shape and the fact it is reasonably bright in comparison to the surroundings, that it wasn’t included on other catalogues such as Sharpless-2.
This image was 3h20min total (10x20min subexposures) with the same equipment as above taken on 10th/11th September 2017. These again were taken with the moon at ~75% full. This could probably do with more exposure to help reduce the noise in the fainter regions (which are a bit marginal here), but cloud stopped play in the early morning for this one.
Field centred at (platesolve by nova.astrometry.net):
RA: 12h 26m 15s
Dec: +12° 52′ 36″
Up is -177 degrees E of N
The 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). Also 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.
Field centred at (plate solve by nova.astrometry.com):
RA: 08h 13m 48s
Dec: -05° 44′ 32″
Up is 3.32 degrees E of N
Faintly visible to the naked eye, M48 is a large open cluster in the sprawling constellation of Hydra, the Water Snake. This was originally one of the “missing” Messier objects – Charles Messier catalogued this object some 5 degrees off in declination, but this cluster was independently observed by Caroline Herschel in 1783 – the connection between the two only being made some 150 years later than Messier’s original observation.
Interestingly, in this image, there is a hint of a nebular structure just to the right (west) of the cluster (about 75% of the way across the frame as shown). It’s hard to see if this is real, or an artefact due to inaccurate flat reduction/reflection – the only way to prove this is by taking deeper exposures, and moving the scope around to ensure no systematic errors. Given the poor weather prior to taking this image, it seems unlikely to happen in the near future!
Images were acquired on 24th March 2017 from West Oxfordshire, using an ST-2000XM through a WO FLT110 on a Losmandy Titan. Exposures were R:G:B = 90:70:70 in 5 min subs, with reduction and processing in Pixinsight and Photoshop.
Field Centred at (plate solve from nova.astrometry.net):
RA: 08h 51m 29s
Dec: +11° 49′ 26″
Up is 90.7 degrees E of N
M67 is an open cluster located in Cancer – it is much smaller than it’s larger neighbour M44 (The Beehive Cluster/Praesepe), and while not the oldest open cluster (with an age estimated to be 4 billion years), it is close at about 800-900ly distance.
None of the stars are bluer than F spectral class (with the exception of the 30 or so blue stragglers found in the cluster), and there is limited extinction from dust/soot, which makes it an excellent target for study, along with a similarly useful target in NGC188.
The set of images taken here was also a first test for a new setup in being able to guide using a newly acquired TS OAG9 – this is a very low profile off axis guider and allows me to guide in front of the filters – while this isn’t always required, it makes holding a guide star much easier, especially for narrowband work where guiding with the guide chip in the camera can be nigh-on impossible! This setup allows me to guide using PHD2 and image using APT (with the advantage of having it’s own focus control and platesolving capabilities, as well as Astrotortilla being able to take images to make platesolving/mount alignment much easier).
Images were taken on 15th and 20th March 2017 from West Oxfordshire, using the SBIG ST2000XM on a William Optics FLT110 working at |f5.7 with the FLAT4 reducer. Guiding was performed off-axis by my ASI120MM, controlled by PHD2.
R:G:B = 90:75:65 (all in 300sec subs).
Reduction/Processing in Pixinsight and Photoshop CS4.
Presented 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.
This 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!
ST2000XM, William Optics FLT110 + FLAT4 reducer
14x5min, L filter
Reduced and processed in Pixinsight
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)