Heart Of Darkness

August 26, 2018 by grahamrob in Deep Sky Objects, Narrowband, Solar system and tagged Cassiopeia, Heart Nebula, Jupiter, Mars, Perseids, Saturn | 4 Comments

HHOO hlvg (Large)

Aside from all the paraphernalia required for astrophotography, two other critical items are essential to start imaging: clear skies and darkness. This year astronomical darkness ceased on 25^th May at Fairvale Observatory and remained absent for the next 8-weeks whilst Earth performed its annual summer gyration about the Sun, culminating on 21^st June with the solstice. As a result this period is typically quite a barren time for astronomers, especially for those in the higher latitudes where the sun does not set for the entire 24-hour day. Some options during this time are: give up, stop imaging and use the time to sort out equipment, if you have the right equipment change to solar astronomy or just enjoy what happens to be about in the less than dark sky. This year I chose the latter, during what has been a very hot summer, often with continuously clear skies for days-on-end.

Planets June 2018

From the early evening we’ve been treated to views of all the planets of the Solar System, as during the short nights one-by-one they transited along the ecliptic, though were relatively low in the sky seen from the UK. In order of appearance, the main show (see above) each night has been that of Jupiter, followed by Saturn and finally at about 2.00 a.m. (June) Mars – which this year was an unusually large, unusually bright red disc as it reached its closest orbit relative to Earth for almost 60,000 years – all of which could be clearly seen with the naked eye. Unable to sleep in the hot weather, night after night I was able to view and sometimes imaged the aforesaid planets with a DSLR camera as they moved across the night sky.

Shortly after darkness started to return on 20^th July came two further special events. First on 27^th July a lunar eclipse, that despite all the previous clear nights was ironically obscured by cloud cover over most of the UK! Fortunately, clear skies returned for 13^th August and the annual Perseids meteor shower, which on this occasion produced some of the best meteor trails I have personally experienced.

And so, with astronomical darkness back and the chance to return to the recently established Fairvale Observatory South AKA The Shed Observatory, it was time to resume my hitherto brief imaging experience of the northern sky again. As a newcomer to this part of the night sky there were considerable new imaging possibilities to explore but only one I now wanted to capture – the Heart Nebula or IC 1805 (also known as the Running Dog Nebula when viewed from a different angle).

Heart-and-Soul-location The Heart and nearby Soul Nebula are situated in a busy region of the sky (see above – from Wikisky), which also contains seven open clusters of young stars, as well as the Pacman Nebula and galaxies of Maffei 1 & 2 and M31 Andromeda. The discovery of a bright fish-shaped HII object – known as the Fishhead Nebula IC 1795 or NGC 896 at the edge of the main object – preceded that of the Heart Nebula itself in 1787 by William Herschel. The Heart Nebula has a red glow, a result of intense radiation emanating from a small cluster of large, hot, young (1.5 My) bright-blue stars at the centre known as Melotte-15. The stellar wind and stream of charged particles that flow out from these newborn stars then creates the characteristic heart-shape of the nebula from the stellar dust and hydrogen gas clouds.

Picture saved with settings embedded.

Located in the Perseus arm of the Milky Way in the Cassiopeia constellation, this large emission nebula is an excellent object for narrowband imaging at all wavelengths and is also well framed in the field-of-view of my telescope-camera combination; the images presented here are rotated 180 degrees to achieve the correct orientation to see the heart shape, with the Fishhead Nebula located in the bottom right corner. Not surprisingly this large HII object produces strong Ha subs, which make a pleasing stand-alone image (above section). But the OIII and especially SII wavelengths are also very good, resulting in very good HHOO bi-colour (top-of-the-page) and SHO (below) images too.

SHO end3Final (Large)

The limited time I’ve had to image the northern sky for the first time this year has already proved to be exciting and bodes well for the future. On this occasion I’ve been very pleased with my first imaging results of the Heart Nebula, which is a superb object for my equipment and am sure to return next year given suitably clear skies and, of course, darkness.

	IMAGING DETAILS
Object	Heart Nebula IC 1805 AKA Running Dog Nebula Sharpless 2-190
Constellation	Cassiopeia
Distance	7,500 light-years
Size	150’ x 150’ = 2.5^o or 200 light-years
Apparent Magnitude	+18.3

Scope	William Optics GT81 + Focal Reducer FL 382mm f4.72
Mount	SW AZ-EQ6 GT + EQASCOM computer control
Guiding	William Optics 50mm guide scope
	+ Starlight Xpress Lodestar X2 guide camera & PHD2 control
Camera	ZWO1600MM-Cool (mono) CMOS sensor
	FOV 2.65^o x 2.0^o Resolution 2.05”/pix Max. image size 4,656 x 3,520 pix
EFW	ZWOx8 + ZWO LRGB & Ha OIII SII 7nm filters
Capture & Processing	Astro Photography Tool + PS2, Deep Sky Stacker & Photoshop CS2, HLVG
Image Location & Orientation	Centre RA 02:33:09 DEC 61:24:23 Top = South Right = West Bottom = North Left = East
Exposures	20 x 300 sec Ha + 10×300 sec OIII & SII (Total time: 200 minutes)
	@ 139 Gain 21 Offset @ -20^oC
Calibration	5 x 300 sec Darks 20 x 1/4000 sec Bias 10 x Flats Ha-OIII-SII @ ADU 25,000
Location & Darkness	Fairvale Observatory – Redhill – Surrey – UK Typically Bortle 5
Date & Time	16^th & 17^th August 2018 @ +23.30h
Weather	Approx. 12^oC RH <=95%

Playing poker with the heavens

August 23, 2016 by grahamrob in Imaging, Solar system, Viewing and tagged Perseids, Perseus, Photography, Solar system | 1 Comment

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It’s that time of the year when Earth ploughs its way through the tail of comet Swift-Tuttle, resulting in a the Perseids meteor shower. The name is derived from the location of the radiant point within the constellation of Perseus and Greek mythology’s reference to the sons of Perseus. Such are the orbital paths that Earth’s encounter with the comet occurs around 11^th to 13^th of August each year and can provide an enjoyable spectacle as the meteor particles rain down through atmosphere.

perseids-e1312951836623

Travelling at some 37 miles-a-second, the sand-grain size particles literally burn up in the blink of an eye, with the energy created producing a bright path of the light path that very briefly shoots across the night sky, sometimes green or red coloured. Some 16-miles in size, from time-to-time the comet itself actually passes nearby to Earth during its orbit around the Sun, last time being in 1992 and the next in 2126.

Perseid ZHR 2016

Whilst the timing of our annual encounter can be predicted with good accuracy, a sight of each individual meteoroid particle is entirely down to chance. Over a period of two or three days the frequency (Zenithal Hourly Rate or ZHR) may vary from a few tens to a few hundred, depending on which section of the comet’s tail Earth is passing through. Of course, observation requires a clear sky – something that’s been notably absent here at Fairvale Observatory for some time now. Notwithstanding, this year there were three consecutive clear, dark, warm nights, which occurred shortly after a new Moon that provided excellent Perseid observing opportunities.

Viewing is a matter of lying back in a suitable garden chair looking up towards the radiant position, which starts in the north east then moves to the south during the night and just waiting. This year peak Perseids were on the evening of 11^th/12^th August between about 11pm and 1am, during which time we probably saw between 20 to 40 hits an hour; the previous and subsequent evenings were also quite good, though with slightly less hits. Such is the randomness of each meteoroid hit that in practice Perseid trails occurred all over the sky and were easy to miss if outside the peripheral vision. However, overall it was a very good and enjoyable show but probably not as good as that from the ISS.

At first this looks great but look again, it’s an aircraft trace – living next to Gatwick airport doesn’t help. The giveaway is in the next shot which shows the track continuing i.e. too long and too far for a meteoroid.

At the same time using the Canon DSLR and an ultra-wide lens, I also attempted to image the Perseid shower. On the first night using Vixen Polarie tracking, set towards the radiant position and on the second night pointing east, without tracking. Control was via an intervalometer, with camera settings at ISO 800, 20 or 14 second exposures, and 5-second shot intervals. Even with such a high incidence of meteoroid hits, obtaining a photograph was still very difficult; mostly the strikes occurred outside the field-of-vision or sometimes in the 5-second pause. In total I shot over 300 images but obtained just two Perseid hits and more than a few plane tracks! Even with good preparation and clear skies it really is a case of chance but I was nonetheless pleased to have my share of luck this time and look forwards to another opportunity this time next year, weather permitting.

Gotcha – the real thing: ISO 800 @ 20 seconds with tracking.

Only just! This time the Perseid is just sneaking out of view at the bottom of the frame: ISO 800 @ 14 seconds, without tracking.

Earth’s Junkyard

August 19, 2015 by grahamrob in Earth, General Astronomy, Widefield Imaging and tagged Perseids, Satellites | Leave a comment

Only very recently the BBC Horizon programme covered the increasing problem of space junk that now orbits Earth forming a virtual cloud of debris posing a serious threat in general and, in particular, to future space activity: obsolete satellites, broken, damaged or even fragments from destroyed man-made objects. In addition to the ISS, communication and other satellites can often be seen passing overhead but in reality these only represent the tip of the iceberg.

Earth’s Junkyard
Computer-generated image of objects and debris currently being tracked orbiting Earth; it’s the stuff we can’t see or track that is most worrying!

Whilst visiting my daughter in Somerset at the weekend the night sky was clear and fantastically dark thanks to the New Moon and lack of light pollution when compared to Fairvale Observatory in Surrey. Having already tried to image the Perseids in the preceding week unsuccessfully, I thought I’d try again in these much better conditions using a basic DSLR on a tripod and an intervalometer.

Despite excellent seeing conditions, the air was cool’ish and therefore prone to quickly form dew on the camera lens after just 20 minutes or so. At the time it didn’t seem as though I had captured anything of interest, however, looking at the images subsequently on the computer, I was excited to find a bright flash appearing between two of the pictures pictures – what could this be, it seemed too short to be a Perseid? Whatever it is was had gone in the next image 5 seconds later. I discovered the anomaly whilst flicking from one picture to the next when suddenly a bright point stood out from the otherwise unchanging starry sky by blinking – a characteristic of something unusual taking place.

I posted a query on SGL and the overwhelming consensus has been that it is most likely to be a satellite or debris flare from the aforementioned space junk – either a spinning satellite or debris that briefly produced a reflection as it passed through the field of vision. Looking closely the bright spot does seem to be elongated from left to right, suggesting movement, though I am still perplexed why it has therefore not produced a more significant trace given the 30-second exposure being used – for a moment I even thought it might be a Super Nova!

Notwithstanding, it’s an interesting effect, though sadly seems to confirm the extent to which mankind has already made a mess of the space around our planet.

Image before the solar flare appears - red circle indicates the area of interest.

Image before the satellite flare appears – red circle indicates the area of interest.

Solar flare, indicated by the red arrow?

+ 5 seconds later a satellite / debris flare, indicated by the red arrow?

Notes: The pictures were taken at 10.37pm on 16^th August, looking north east, at about +70^o inclination using a Canon EOS 700D + 18-55 lens, at 18mm and f5.6. Both images are 30 secs exposure at ISO1,600 with an interval of 5-seconds. The area of interest is indicated with a red ring in the first image, with the white ‘object’ appearing in the following image shown by a red arrow.