Category Archives: astronomy

Nov 2017 Lunar Mosaic

The 4th November 2017 gave me clear skies with a very bright moon in the sky – this gave me  good opportunity to use the rebuilt 14″ Newtonian scope for some imaging work, now that the scope truss tubes have been correctly milled down to the right length. 

Using the ASI120MM camera with a 742nm nr-IR filter, I imaged the moon at its native focal length (1582mm), using Firecapture to grab the video. The data totalled 56GB in all!

The finished mosaic consists of 18 frames: each of these was the result of stacking the best 12%  (quality-wise) of 3000 frames. Each of the frames were 0.18ms each (with gain set to 54), and were captured at around 31 frames per second.  To try to avoid issues with exposure mismatch, all the exposure details were kept identical throughout the 36 minutes  or so it took to complete the whole set of videos across the face of the moon.

99% Moon on 2017-11-04
Mosaic of 99% Moon on 2017-11-04 at 80% resolution (3MB image size)

The videos captured were aligned and stacked using Autostakkert2, and each of the stacked images were processed using identical wavelet settings in Registax6. 

To create the mosaic itself, I took all the images into Microsoft Image Composite Editor (ICE) and let it get on with the process of aligning and stitching the images together. It did a remarkably good job! I had also tried the Photomerge function in CS4, but ICE did a better job here: Photomerge was good but left a couple of slight merging artifacts – misalignments on the limb, mostly. 

Final processing took place in Photoshop (smart sharpening, levels, curves, etc) with the result being a 20Mpixel image weighing in at 7+ MB for a high quality jpg. Here, I’ve reduced the image to 80% of the original resolution to aid web viewing!

Images were taken starting at 2215UT from West Oxfordshire, UK. 

IC1396A – Elephant’s Trunk Nebula

Image centred at (nova.astrometry.net plate-solve):
RA: 21h 34m 17.296s
Dec: +57° 30′ 37.211″
Up is 2.19° E of N

IC1396 is a very large region of HII emission located in the Milky Way within Cepheus, which spans over 5 degrees of sky. Within IC1396, to the western side, is the Elephant’s Trunk Nebula, known as IC1396A, and VdB 142, which is a reflection nebula at the end of the “trunk”.

IC1396A - The Elephant's Trunk Nebula in Cepheus - LRGBIC1396A itself is a dense globule of gas and dust that appears to be lined by bright pink emission from atomic hydrogen. This emission is due to excitation by the giant triple star system HD 206267 (off field to the left). The globule appears to be an area of star formation, and contains two young stars in the head of the globule that have created a cavity by the action of their own stellar winds. 

These F-type stars provide the illumination for the rare yellow reflection nebula seen in the head of the globule, as well as the radiation causing the pink hydrogen emission within the cavity. The combined action of HD 206267 and the two young stars has resulted in areas of high compression in the nebula, triggering the formation of protostars.

Data was captured on the night of the 21st September 2017 from West Oxfordshire. Image details are as follows:

L:R:G:B = 130:45:35:35
(L:10m subs, RGB: 5m subs, 2x bin)

Taken using a WO FLT110 @ f5.6 with SBIG ST2000XM, on Losmandy Titan.

Processing was performed in Pixinsight – control over the star sizes is tricky here, and I may try and improve on this later. There’s also a (relatively) small amount of data used here – this is certainly a subject that would benefit from adding more exposure (which may also help with star control), as well as H-Alpha data to increase signal and contrast in the emission nebula areas.

Simeis 57 – Propeller Nebula in Cygnus

The Propeller Nebula (Simeis 57) in Cygnus - 7hrs ExposureI had opportunity on the 19th/20th September 2017 to add another 3h40m of exposure to my previous image of the Propeller Nebula (Simeis 57/ DWB111/119) – see “A Crescent and A Propeller” for the previous version. Here is the reprocessed version of the data, taken through an H Alpha filter, which is centered at RA: 20h 16m 08s, DEC: +43° 40′ 42″ (plate-solve from nova.astrometry.net).

Simeis 57 - Annotated with Simbad query resultsThe extra time on this subject has brought out some of the fainter background nebulosity and enhanced dark nebulae in the field. The image at left is an annotated image (using the Image Solver and Annotate Image scripts in Pixinsight). As shown, the Propeller itself is catalogued as DWB111 (south) and DWB 119 (north), with DWB118 representing the surrounding nebulosity, with DWB 108 further to the south below the southern “prop”. There are a few catalogued dark nebulae in the field – Dobashi 2501; Dobashi 2511/TGU H469 P16 which sits between DWB118 and DWB 107 (off field to lower left); and TGU H469 P18 to the west of the main nebula. 

For more information about this region, and pretty much the only bit of published research I can find on it(!), see the paper “Israel, F.P. , Kloppenburg, M., Dewdney, P.E., Bally, J. (2003), The peculiar nebula Simeis 57, Astronomy and Astrophysics, 398, 1063 – 1071“.

All data was taken from West Oxfordshire on 9th/10th and 19th/20th September. William Optics FLT110 @f5.6 on a Losmandy Titan, SBIG ST2000XM CCD and an Astrodon 5nm HA filter.

A Crescent and A Propeller

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 Crescent Nebula (NGC6888) in CygnusThe 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 Propeller Nebula (Simeis 57) in CygnusThe 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. 

 

Widefield Imaging from France

Summer is traditionally a poor time for astronomy in the UK – it doesn’t really get dark in my location between late May and late July, and so I’ve not done a lot of astrophotography recently, though I have done a little bit of equipment work, cleaning, etc.

However, on a recent holiday to France (staying near St. Nathelène, near Sarlat-La-Caneda), I managed to do a little bit of widefield imaging work. I used a 350d and a couple of newly acquired lenses – a Canon 85mm f1.8 USM, and a Samyang 14mm. The 350d was modded when I bought it last year, though I have since added a Baader BCF filter to restore the focal point to allow me to use normal camera lenses with this camera body. One negative about this camera is that there are no 64bit drivers available, so I’m forced to run everything from inside a Virtualbox VM…(*)

Before the holiday, I built myself a camera mount for my GM8, based upon a spare dovetail I had. This has a Arduino driven stepper motor with a simple belt drive to focus the lenses – the system is based around the MyFocuserPro code using an Easydriver board. This has an ASCOM driver and can be nicely controlled from software like APT – this makes focusing relatively easy, though having liveview like on the 450d would be much easier!

Northern Summer Milky Way from Lacerta to ScutumFirst up is a widefield image of the summer Milky Way, stretching from Lacerta to Scutum – this is a stack of 12x5min exposures, taken through the 14mm Samyang at f2.8. Reduction and processing was done using Pixinsight, with slight tweaking in Photoshop.

This was the first image I’ve taken through this lens, and the first widefield work I’ve done in about 20 years (!). The lens is not perfect (in fact I’ve replaced it with another example that is better and doesn’t show the coma on axis here which I think it’s due to element decentering), but it has still given me probably the best widefield shot of the Milky Way that I’ve produced: digital photography makes such shots much easier than slide film in some ways, but not others…! Clearly visible are the dark dust lanes (the Cygnus rift) as well as emission nebula such as IC1396, the North America Nebula, the Pelican Nebula, and the Gamma Cygni complex. From nova.astrometry.net here is an annotated version showing the major constellation outlines – interesting here is that even astrometry.net can’t handle the lens distortions from such a wide angle lens.

Scutum Star Cloud, M11, M26 - 85mm USM CanonSecond image is actually the first image I have taken with this camera – this using the 85mm f1,8USM Canon lens (at f3.5). This is a shot of the area around the Scutum star cloud, M11, The Wild Duck Cluster and M26. It was “only” 4×180 seconds – clouds rolled through after this point, but it was a good learning experience (I’d close the aperture slightly more, and go for longer exposure). Nevertheless, I think I’ve managed to tease out some detail here, though gradients were tricky to handle using DBE in Pixinsight, along with some corrections in Photoshop. More exposure would have helped enormously here, and I think I can improve the capturing of calibration frames in future.

Similar to above, shown here is an annotated image (from nova.astrometry.net) to show exactly what is in the image, and which highlights some of the various deepsky objects around the field of view.

(*) – More recently, I’ve been looking at kstars and ekos for camera control – this looks promising and should allow control of the camera, mount and focuser using a Raspberry Pi.