NGC 884 and NGC 869: The Double Cluster...

Objects: NGC 884 and NGC 869 (The "Double Cluster", Caldwell 14)
Type: Open Clusters
Constellation: Perseus
Distance: 7500 light years

Date: February 14th. 2019
Equipment: ATIK 460EX, Vixen 114mm f5.3 ED114 refractor, NEQ6 mount, guiding with Lodestar X2/PHD

Subframes: 20 x 300s luminance, 12 x 200s each for RGB (2x2 binned), no flats, hot pixel removal in Astroart (no main frame darks).

Known since antiquity, the “Double Cluster” was catalogued in 130 BC by Greek astronomer Hipparchus, who referred to it as a “nebula” or “cloudy spot”, one of the half a dozen then recognized.  The starry nature of the clusters remained a mystery until the invention of the telescope in the early 1600’s.

Now known respectively as h and chi Persei, or NGC 884 (to the east, or left, of the image) and NGC 869 (the cluster to the west, or right, of the image), the clusters themselves are separated by only a few hundred light-years and contain stars much younger and hotter than the Sun. 

In addition to being physically close together, the clusters' ages based on their individual stars are similar - evidence that both clusters were likely a product of the same star-forming region.  NGC 869 has a mass of 3700 solar masses and NGC 884 weighs in at 2800 solar masses; however, later research has shown both clusters are surrounded with a very extensive halo of stars, with a total mass for the complex of at least 20,000 solar masses. 

Based on their individual stars, the clusters are relatively young, both 12.8 million years old.  There are more than 300 blue-white super-giant stars in each of the clusters.

Discernible with the naked eye under dark skies, NGC 869 and NGC 884 occupy an area of sky approximately one degree across, each cluster being physically around 35 light years across. Binoculars are required to see the two clusters as separate entities from suburban skies. Telescopically, this is one of the most popular of objects for visual astronomers. It forms the “sword handle” of Perseus, as shown in the Stellarium star chart below:

This particular evening was clear but a bright gibbous moon was parked high in the sky, thus ruling out any attempt at faint nebulous objects. Processing was straightforward, with the RGB stacks combined in Astroart to give a colour image with pleasing and contrasting star colours. Some of the brighter stars have haloes, possibly caused by reflections from the RGB filters: Pixinsight acolytes would no doubt sneer at such things, but I quite like the effect.

Addition of the stacked luminance data as a luminance layer in PaintShop gave the final image above.  I used a star mask to just slightly drop the luminance and sharpen the stars surrounding the two clusters, just to get the clusters to stand out from the starry background a bit more.

IC 443: The Jellyfish Nebula...

Object: IC 443
Type: Supernova remnant
Constellation: Gemini
Distance: 5000 light years

Date: February 10th. 2019
Equipment: ATIK 460EX, Vixen 114mm f5.3 ED114 refractor, NEQ6 mount, guiding with Lodestar X2/PHD

Subframes: 16 x 600s H-alpha, 6 x 150s each for RGB (2x2 binned), no flats, hot pixel removal in Astroart (no main frame darks).

Discovered on September 25th, 1892 by German astrophotographer Max Wolf, IC 443 is a supernova remnant in the constellation Gemini, produced by a supernova explosion thought to have occurred between 3,000 and 30,000 years ago.  Physically, the nebula is about 70 light years across. Visually it appears to be approximately 50 arc-minutes across, an area of sky just under twice the apparent size of the full moon.  It is not readily seen in backyard telescopes.

The location of IC 443 is shown in the Stellarium sky chart below, just to the east of the third magnitude star Eta Geminorium (named Propus, the bright orange star to the right of the image).

Observations from the Chandra X-ray observatory show that the explosion that created the Jellyfish Nebula may have also formed a peculiar object located on the southern edge of the remnant, called CXOU J061705.3+222127, or J0617 for short. The object is likely a rapidly spinning neutron star, or pulsar, representing the end stage of a star with between 1.4 and 3 solar masses  

When a massive star runs out of thermonuclear fuel, it implodes, forming a dense stellar core called a neutron star.  The outer layers of the star collapse toward the neutron star then bounce outward in a supernova explosion.  

A spinning neutron star that produces a beam of radiation is called a pulsar.  The radiation sweeps by like a beacon of light from a lighthouse and can be detected as pulses of radio waves and other types of radiation.

The comet-like shape of the diffuse X-ray emission suggests motion towards the lower right of the image.  The structure is also evidenced at visible wavelengths, as highlighted in the hydrogen alpha image below:

The orientation of the “line” is about 50 degrees away from the direction expected if the pulsar was moving away from the centre of the supernova remnant in a straight line.

This misalignment has cast some doubt on the association of the pulsar with the supernova remnant. 

However, it is thought that this misalignment could also be explained by movement towards the left of material in the supernova remnant pushing J0617's cometary tail aside.



Seeing conditions and atmospheric clarity were excellent on this particular evening. I was able to grab 16 hydrogen alpha frames before the dreaded "meridian flip" (where the object crosses the east/west line, requiring the telescope to be spun round to prevent it hitting its own pier).  This is a pain and requires the telescope to be re-targetted, although fortunately my set-up usually gets the object back on the CCD chip after the flip, requiring only minor adjustments to re-frame the object on the CCD chip.

Given that the weather forecast was threatening clouds, I decided to grab the RGB frames rather than get more H-alpha data, although 16 subs isn't really enough to beat the background noise down.  My luck held, and I got the last of the blue subs just as a few clouds started to roll in at around midnight.

Colour processing was conducted using the same methods as I used for the Cave Nebula.

IC 410: The "Tadpoles" Nebula...

IC 410 and NGC 1893... 

Object: IC 410 (nebula), with NGC 1893 (star cluster)
Type: Emission nebula with open cluster
Constellation: Auriga
Distance: 12000 light years

Date: January 29th. 2019
Equipment: ATIK 460EX, Vixen 114mm f5.3 ED114 refractor, NEQ6 mount, guiding with Lodestar X2/PHD

Subframes: 16 x 600s H-alpha, 10 x 600s OIII, 6 x 150s each for RGB (2x2 binned), no flats, hot pixel removal in Astroart (no main frame darks).

IC 410 is an emission nebula partly obscured by dark, dense molecular clouds, and forms part of a larger star forming region that also contains the Flaming Star Nebula (IC 405, which lies approximately 1.5 degrees to the west of IC 410).  The cluster within, NGC 1893, was discovered in 1827 by John Herschel, but the surrounding nebula IC 410 was not detected until 1892, by German astronomer and astrophotographer Max Wolf.

The nebula occupies an area in the sky approximately 40 arc-minutes in diameter (a bit larger than the full moon). In reality, the nebula is approximately 100 light years across. Visually,I was once lucky enough to just about make out the brightest areas of IC 410 in an 9.25-inch SCT on a night of excellent transparency from a suburban sky. The cluster NGC 1893 appeared to be enmeshed in a faint haze of nebulosity, with fainter lobes to the west and south of the cluster that required a low power (40mm) eyepiece and an OIII filter to provide the necessary contrast. It is not surprising that John Herschel missed it visually.  

IC410 is illuminated by fluorescence caused by the excitation of its gaseous atoms by radiation from the hot stars of the open star cluster (NGC1893) that lies in the centre of the nebula that gave birth to it.  This star cluster is about 4 million years old, but in astronomical terms it is still very young. 

The "tadpoles" of IC 410 (detail from main image)

At the top-left of the star cluster in the image, two columns of dust and gas left over from the formation of the star cluster can be seen.  These objects are designated as Simeis 130 – the lower of the two – and Simeis 129 (the rather obscure Simeis catalogue of nebulae arises from the Crimean Astrophysical Observatory, which has a facility in the town of Simeis in the Ukraine) and are popularly referred to as “the tadpoles”. These structures are thought to contain embryonic stars hidden in the dust and gas that enshrouds them.  As can be seen in the image, the heads of the “tadpoles” are outlined by bright ridges of ionised gas, while their tails trail away from the cluster's central region, evidence of the stellar winds and intense radiation pressure from the stars of NGC 1893.

IC 410 can be found high in the Orion Milky Way in the constellation Auriga, as indicated in the Stellarium sky chart below:

The striking green/blue colour visible in the main image arises from the fluorescence of triply-ionised oxygen atoms (OIII) which seems to be unusually strong in this particular nebula (the orange/red is from ionised hydrogen – Hydrogen alpha emission – which is the principle light given off by most emission nebulae).

Atmospheric stability and clarity were rather poor when I acquired data for the image, but this was the first clear spell that I had been able to make use of in the last six weeks, so beggars can’t be choosers.  The guiding wasn’t brilliant (about 1.2 arc-seconds RMS) and the resultant sub-frames were also very “noisy” due to a high haze of moisture that cut my gathering of OIII subframes short.

Fortunately, the signal was pretty strong in both Ha and OIII and the image stacks, although few in number, did not require much of a stretch.  

The narrowband colour data was RGB combined in Astroart (red = Ha, green =70/30 OIII/Ha, blue = OIII).  The RGB frames were also RGB combined and the result blended with the narrowband stack in PSP to give star colours. 

Lunar eclipse...

Total lunar eclipse @ 05.00h, 21-01-2019

Object: Moon

Constellation: Cancer
Distance: 357730 km (222282 miles)

Date: January 21st. 2019
Equipment: Canon 450D, Vixen 114mm f5.3 ED114 refractor, NEQ6 mount

Subframes: 20 x 1/2s @ ISO800, stacked and sharpened in Registax 2.1.14

The excitable UK press had billed this celestial event as a “Super-Blood-Wolf-Moon” or some such gibberish. 

During this lunar eclipse, the moon was close to perigee, the closest point to Earth in its orbit, making the moon appear slightly larger than usual. This phenomenon has been dubbed a “supermoon” by the popular press, and is not an official astronomical term.  Of the possible 12 or 13 full (or new) moons each year, usually three or four may be classified as supermoons, so they are not particularly rare. Even then, a full moon at perigee appears only about 14% larger in diameter than at apogee, a difference that is barely discernible to the visual observer.

The popular press now also seems to call lunar eclipses “blood moons” because of the way the Moon can turn a deep coppery red colour during its eclipse. The effect is caused by atmospheric dust scattering higher frequency blue light waves, but allowing the longer wavelength of red light to come comes through.  A similar effect is in evidence just as the moon rises above the horizon, where the moon’s light has to travel through a deeper layer of dust-laden air. 

Until recently I hadn’t heard of the term “blood moon”, but I guess the popular media like it because it sounds dramatic. They also threw the term “wolf moon” in there, enabling them to depict Earth’s natural satellite as undergoing some B-movie werewolf transition.

Native American Indians have traditional names for all of the full moons throughout the year: January’s full moon is called the “Wolf Moon”. If the eclipse had occurred in March, the press would have been disappointed: “NotSoSuperBloodWormMoon” doesn’t sound quite as dramatic.

The colour of the Moon during totality depends on the global state of dust in the Earth’s atmosphere; sometimes it is so dark a red as to render the moon virtually invisible.

This particular eclipse was not as dark as the one of September 2015 and was clearly visible despite the misty, damp and freezing (-4°C) conditions of the Medway valley adding to a high cloud haze.  This seems to have added its own palette to the few images I was able to get between clouds, which cleared just enough at 5 a.m. to show an unusual blue tint to the brighter edge of the fully eclipsed moon.

The next total lunar eclipse that will be completely visible in the UK is not until 20th/21st of December 2029.  Approximate timings for the south-east of England are as below:

Moon enters penumbra:             19:40

Moon enters umbra:                  20:55

Start of totality:                        22:15

Maximum eclipse:                     22:40

End of totality:                          23:10

Moon leaves umbra:                  00:30

Moon leaves penumbra:             01:40

The eclipse will be well-placed for observing (conditions permitting!), being high up on the Orion/Gemini/Taurus border. 

Comet 46P/Wirtanen

Comet 46P/Wirtanen

Object: 46P/Wirtanen

Type: Comet
Constellation: Taurus
Distance: 0.0806 AU (7.5 million km)

Date: December 12th. 2018
Equipment: ATIK 460EX, Vixen 114mm f5.3 ED114 refractor, NEQ6 mount, guiding with Lodestar X2/PHD

Subframes: 30 x 120s luminance, 20 x 30s each for RGB (for comet, same again for stars).  Additional 60s (30 taken) and 30s luminance frames (70 taken) were also obtained (see below) in this session.

Comet 46P/Wirtanen was discovered by Carl A. Wirtanen in 1948 at the Lick Observatory, California on a photographic plate.  The plate was exposed on 17 January 1948 during a stellar proper motion survey at the observatory.  It took over a year before the object was recognised as a short-period comet due to a lack of observations.

Comet 46P/Wirtanen has an orbital period of approximately 5.4 years and belongs to the “Jupiter Family” of comets. Jupiter-family comets will occasionally have their orbits perturbed when they make a close approach to Jupiter because its strong gravitational field can alter (sometimes quite significantly) a comet's path through space.

In the case of 46P/Wirtanen, it underwent two such interactions with Jupiter (in April 1972 and February 1984) that pushed its orbit about 50 million miles closer to the sun as well as very near to the orbit of Earth.

Perihelion passage of comet Wirtanen will be on 16 December 2018 when it will pass 0.078 AU (7,220,000 miles) from Earth.  Close though this encounter is, the comet is relatively small in size with an estimated nuclear diameter of just 1.2 kilometers (unlike the Great Comet of 1997, Hale-Bopp, with its 60 km nucleus) and so will not appear to be particularly bright.  

46P is expected to reach magnitude 3, but this light is spread out a bit across the comet’s visual area which, unlike a star, is not a point source. It is therefore right at the limit of naked eye visibility. I could not see it without binoculars, even though I knew exactly where to look. This is the brightest prediction of known and future passes of this comet. This is also currently the brightest prediction for all comet passes in 2018, although even by the usual UK tabloid’s moronic standards, it can hardly be described as a “head-scorcher”….

Sensible information about 46P Wirtanen can be found here.

The "seeing" on the evening of December 12th. was horrendous.  Focussing was a challenge as star shapes fluctuated wildly between focus frames. I initially gathered 70 x 30 second luminance frames and 20 x 30 second frames in RGB, (plus a further 20 x 30 second RGB frames for star colour once the comet had drifted out of the field of view). No evidence of a tail could be seen. Setting PHD to guide on the comet nucleus seemed to work fairly well, although the longer subs at 60 seconds and 120s seem to be plagued with noise and gradients - I think some high cloud had set in.  This made processing a bit difficult and it took a few iterations to get the noise reduction and background brightness into a presentable image.  The 120s subs did show a hint of a tail and the final result is shown above.  The shorter sub stacks did not show much in the way of cometary detail but are shown below.

A map of the comet's perihelion passage through the constellation of Taurus is shown below:

Track of 46P through Taurus, 11-16 December (position marked every 12h)

Using the sigma stacking function in Astroart, and "one star" alignment gave an image of the comet with star trails virtually eliminated.  The LRGB stack showed the bright green colouration of the comet itself.  I layered the RGB star stack over it to give coloured stars in the final images.

46P - Larson Sekanina filtered image

The striking green fuzzball (see an explanation of the colour here) rather dominates the image and it was a bit tricky to stop it being spoiled by an "onion ring" brightness gradient, which I still haven't completely eliminated.  The core does show a tiny bit of detail and a hint of a tail.

The AstroArt image processing programme offers something called a Larson-Sekanina filter, which uses a lot of complex math to allegedly pull out cometary detail from raw comet images. Applying this to the luminance data stack gives a result (left) does seem to show a tail and other additional details that correspond to faint features in the colour image above.


Below is a GIF animation using the 70 x 30 second luminance frames from above, showing the comet moving against the sky background.

This 3 second sequence shows the movement of the comet between 19.07 and 20.01 on December 12th, 2018, over a span of about 9 arc-minutes (or about a third of a full moon diameter).  The comet appears to graze the 9.7 magnitude Hipparcos catalogue star HIP 16342.

Comet 46P Wirtanen - (stack of 30s subframes)

Comet 46P Wirtanen - (stack of 60s exposures)

IC 1396A (vdB 142) & IC1396B - The Elephant's Trunk...

IC 1396A (vdB 142, left) and IC 1396B (centre); The "Elephant's Trunk"...

Object: IC1396A (vdB 142) + IC1396B

Type: Reflection/emission/dark nebula
Constellation: Cepheus
Distance: 2400 light years

Date: November 18th. and December 7th. 2018
Equipment: ATIK 460EX, Vixen 114mm f5.3 ED114 refractor, NEQ6 mount, guiding with Lodestar X2/PHD

Subframes: 24 x 600s H-alpha, 20 x 600s OIII, 20 x 150s blue (2x2 binned), 30 flats/dark flats per channel, hot pixel removal in Astroart (no main frame darks).

Popularly called the Elephant's Trunk Nebula, IC1396A and IC1396B are parts of a much-larger region of faint nebulosity (IC 1396) that lies 2,450 light-years away in the constellation of Cepheus and which spans an area of over 5 degrees as seen in the sky.

Location of IC 1396A in the sky...

IC 1396A is a bright-rimmed cloud (BRC) on the periphery of the associated giant H II region IC 1396 produced by the Trumpler 37 star cluster. Over 250 young stars in and around IC 1396A have been identified, with a spatio-temporal gradient of stars from the IC 1396A cloud towards the primary ionizing star HD 206267 being found.

The entire IC 1396 H II region (Sh 2-131) is excited mainly by the star HD 206267 located at the centre of the region (and just out of shot to the left in the above image) in the 4 million year-old cluster Trumpler 37. IC 1396 has a rich population of >20 bright-rimmed and cometary globules seen in silhouette against the emission nebula.

Many of the clouds reside on the large molecular shell surrounding the H II region, and sites of possible star formation have been identified in/around at least several globules, including sites of substantial star formation in IC 1396A. 

Lying 15′ west of HD 206267, IC 1396A is the BRC closest in the sky to HD 206267.  Its optical rim is the brightest of all rims and the cloud is thus likely to be the physically closest to HD 206267. IC1396B lies slightly to the west of its brighter sister.

A cavity in the molecular cloud is present in the head of the A globule and contains a pair of young stars (LkHa 349 and LkHa 349c) that formed from the dense gas in the globule, and which have cleared the spherical opening within the head of the globule. They provide the glint in the eye of the elephant, as seen in a crop of the above image (below).

These stars can be seen in both optical and Spitzer infrared images. While one of these stars is much fainter than the other in optical images, they show a similar brightness in the infrared Spitzer image. This indicates the presence of a thick and dusty disk around LkHa 349c. These disks, called circumstellar disks, are the places where planets and moons will likely form in the future. They are much thicker in the early stages of star formation and glow brightly in infrared. 

IC1346A is also designated as vdB 142. The vdB (van den Burgh) catalogue was originally published in 1966 by Sidney van den Bergh, and referenced 158 reflection nebulae:A study of reflection nebulae, van den Bergh, S., 1966.  Later it was expanded to 159 objects by René Racine:Stars in reflection nebulae, Racine, 1968. The catalogue contains information for all stars with a spectral classification of BD and CD lying north of -33 deg and which are surrounded by reflection nebulosity visible on both the blue and red prints of the Palomar Sky Survey.  The nearer reflection nebulae lie predominantly along Gould's Belt, whereas the more distant ones are concentrated in the galactic plane.

Gould's Belt itself was first described by Benjamin Gould in 1879 as a collection of bright and massive stars that form a ring in a projection on the sky.  This rings traces out several molecular clouds in the local part of the galaxy where star formation is prominent.  Gould's Belt is estimated to have a diameter of 3000 light years.

The hydrogen alpha image (below) shows a detailed mixture of bright and dark nebulosity.

IC1396A/B in hydrogen alpha..

The OIII and blue channel data show very little data by comparison.  The Ha, OIII and blue channels were RGB combined in AstroArt (Ha = red, OIII = green, blue=blue).  The RGB image was then exported to PaintShop Pro and curve adjusted, with the Ha channel then added back as a luminance overlay. Blue haloes on the brighter stars were manually removed with the colour replacer tool, with final contrast and curves adjustment to give the final image shown at the top of this post.

I also tried a HOO version, using the H-alpha data as the red channel, and the OIII data for green and blue...

IC 1396A/B as HOO

This rendition has the fashionable orientation of north to the right and is fashionably darker. My preference is to try and present deep-sky images in their correct aspect, but in this case the columnal nature of the dust clouds is nicely emphasised.  I always think that in this view, the nebula resembles a woman walking away from the field of view...

The Cave Nebula (Sharpless 2-155)

The Cave Nebula (Sh2-155)

Object: Sharpless 2-155 (Caldwell 9)

Type: Emission nebula
Constellation: Cepheus
Distance: 2400 light years

Date: November 2nd. 2018 (Ha), 17th (RGB)
Equipment: ATIK 460EX, Vixen 114mm f5.3 ED114 refractor, NEQ6 mount, guiding with Lodestar X2/PHD

Subframes: 40 x 250s H-alpha (2x2 binned), 20 flats, hot pixel removal in Astroart (no darks). 10 x 250s (2x2 binned) each for RGB

The Cave Nebula is part of an extensive region of ionised hydrogen gas associated with the Cepheus B giant molecular cloud.  The ionisation is caused by radiation from a group of young, hot stars hidden within the dust cloud, which knocks hydrogen electrons into "excited" states that re-emit radiation and cause the surrounding low-pressure hydrogen gas to glow.  Sh2-155 is just a small part of an extensive area of nebulosity in the Cepheus/Cassiopeia region that includes several notable emission nebulae.  It lies about 3.5 degrees south of iota Cephei...

The evening of November 2nd. was clear but the atmosphere was very unsteady. I decided to run the Atik camera in 2 x 2 "binned" mode, partly to make autoguiding accuracy less critical and also because the Cave Nebula is extremely faint and I didn't fancy spending hours getting enough 20 or 30 minute subs to beat down the background noise.

However, this loses a bit of resolution, but the poor seeing would have done that anyway. The seeing did make focussing a bit hit and miss however, and I should really have looked at the first couple of subs a bit more closely.  When I finished the session and downloaded the images next day, I was frustrated to find that the stars were out of focus, with some showing a "doughnut appearance".  At this point I would normally delete them and wait for another imaging opportunity, but clear, moon-free nights at reasonably civilised hours are an extremely rare occurence in my part of the world, so I decided to see if the situation was redeemable.

The Cave Nebula in H-alpha

Fortunately, a couple of software routines in Astroart (Digital Development followed by a few iterations of Lucy-Richardson deconvolution using a mild Gaussian point spread function, for the record) were able to pull the star and nebulosity details back into a reasonably decent shape.  A bit brightness and contrast adjustment (using "curves") and noise removal (mild edge-preserving smooth), both in PaintShop Pro, gave the Hydrogen alpha image above.

I did try and get some hydrogen beta data, but 300 second exposures at 2x2 binning revealed not a jot of nebulosity in the area, so I guess this object just doesn't emit in this part of the spectrum.

It was a couple of weeks before I was able to get some RGB data to make up a colour image.  250 second subs (2x2 binned) through Baader red, green and blue filters were stacked, aligned and RGB combined in Astroart to give this rather disappointing RGB image...

RGB - Cave Nebula area

Whilst the star colours were fine, there was hardly any trace of nebulosity visible. I guess a 60% waxing moon and shortish subs washed out the contrast.  Clearly, I would not be able to directly use the H-alpha frame as a luminance layer, as the lack of any nebula colour in RGB would just result in coloured stars on a grey nebula.

I decided to colourise the existing H-alpha frame by pasting it on to a red background in "Hard Light" mode in PSP.  This gave a bright red nebula image with white stars...

The brighter H-alpha regions tend to remain washed out and so I prepared a second mask as above, but combining in "multiply" mode. This gave a completely red nebula with red stars...

"Colourised" H-alpha frame...

Selecting the bright area (with a feather of about 20 pixels), I pasted and aligned the area over the "Hard Light" image.  With careful use of the eraser tool in PSP and a partial blending (around 50%) it was possible to greatly reduce the remaining washed-out H-alpha regions...











Pasting this over the RGB stars in "lighten" mode at around a 70% blend gave a reasonable mix of star and nebula colour,  A few tweaks to the final colour and contrast using curves gave the final result you can see at the top of this post.

OK, never a NASA APOD, but given the poor quality of data I don't think it turned out too bad.

The Crescent Nebula - NGC 6888

The Crescent Nebula: NGC6888

Object: NGC 6888

Type: Emission nebula
Constellation: Cygnus
Distance: 5000 light years

Date: September 3rd. and October 9th. 2018
Equipment: ATIK 460EX, Vixen 114mm f5.3 ED114 refractor, NEQ6 mount, guiding with Lodestar X2/PHD

Subframes: 20 x 300s H-alpha, 16 x 450s OIII, 20 flats for each channel, hot pixel removal in Astroart (no darks).

NGC 6888, the “Crescent Nebula”, is a cosmic bubble of rarefied gas about 25 light-years across, formed by stellar winds from its central Wolf-Rayet star (WR 136).  Wolf–Rayet stars are massive stars that have completely lost their outer hydrogen shell and are fusing helium or heavier elements in its core. This star is shedding its outer material in a strong stellar wind, ejecting the equivalent of the Sun's mass every 10,000 years.  The nebula's complex structures are the result of this strong wind interacting with material ejected in an earlier out-gassing phase.  Burning its helium fuel at a prodigious rate and nearing the end of its stellar life, this star will ultimately end in a supernova.

The above image uses narrowband image data obtained by passing the light collected by the telescope through interference filters that isolate light from hydrogen and oxygen atoms in the nebula.  The "forbidden" ionised oxygen atoms produce the blue-green hue enshrouding the detailed folds and filaments of the main nebula.

NGC 6888 is located near Sadr, the central star in the Northern Cross of Cygnus, within the "Summer Triangle" of the bright stars Deneb, Vega and Altair.  The whole area is suffused with wisps of emission nebulae, that show up well in monochrome H-alpha images (below)

Wide field - H-alpha only

A crop of the area shows up the filamentary structure of the nebula...

Crop

These images are the first I have obtained from my new Atik 460EX CCD camera.

Needless to say, any investment in shiny new toys results in conditions that prevent you from playing with them.  Nearly a month elapsed between the collection of the H-alpha data and the OIII frames, due to a combination of moonlight, high haze and horrendous local dew and mist problems.  The night I finally managed to collect the OIII frames was cut short as the humid conditions led to veritable waterfalls of dew running down the outside of the 'scope and the insides of the observatory walls, to the extent that I was worried about shorting out the electrics!

Processing consisted of sigma stacking in AstroArt (which eliminated the aircraft light trails in several of the subs - another challenge associated with imaging from the Medway valley region, which often lies under the Heathrow/Gatwick/London City airport flight paths), with hot pixel removal set at 70%, followed by noise removal and curve adjustment in Paintshop Pro.  The Ha and OIII stacks were taken back into Astroart for registration, and a false green channel then generated in PSP by layering the two narrowband stacks and "multiplying".  The three channels were then RGB combined in Astroart, with a bit of tweaking in PSP to give the final colour image above.

I still feel that the final colour image is a bit flat, and would benefit from some RGB data to give some colour to the field stars.

It's still an improvement upon my first attempt at imaging this nebula, from some 13 years ago...

Lightning over my observatory...

A single frame grabbed with PaintShop Pro Animation Shop from a 30 second video shot with my old Sony Cybershot...

Lightning, 07 August 2018

Mars and Saturn...

Mars has just passed opposition but is low down in the constellation Capricorn, rising to no more than about 12 degrees above my southern horizon. As a result of this, the combination of unsteady, hot summer air and atmospheric refraction makes conditions rather difficult for planetary imaging. Added to that, surface features on Mars have recently been obscured by a planet-wide dust storm, which is only just subsiding.

Nevertheless, I thought it might be worth trying to record a closer view of the baleful, dull red coal that is currently rising in my south-eastern sky at around 21.00.  Other than the moon, Mars is, at the moment, the brightest object in the night sky, with an unmistakable fiery hue that fully justifies its name of "the Red Planet".  Its magnitude is -2.7, but this will fade over the next few months as the planetary orbits open up the distance between us.

Mars, August 2nd. @ 23.15

This was taken using an old Phillips TouCam and a x2 barlow lens fitted to a Celestron C9.25.  The planet is too low down to be seen from my observatory so I set the scope up on my balcony, which offers unrestricted views to the east and south.  A one minute AVI file was taken at 25 fps and the output processed in Registax.

The southern polar ice-cap is just discernible as a lighter smudge at the bottom of the disc but other than that, surface details are just blurry blobs.

Similarly, I thought I'd have a go at Saturn, which passed opposition in June and is also low down in southern sky in the constellation of Sagittarius,  Although at a slightly greater elevation than Mars, (16 degrees at best at the moment), seeing conditions are just as poor.

Saturn, August 2nd. 22.45.

Set-up and exposures were as for the Mars shot above. Some planetary banding and the Cassini division in the rings are clearly visible, although again the image is blurred.