Great Balls Of Ice

iceball

The next couple of months can be frustrating for astronomers in the Northern Hemisphere.  We have just entered the period of summer during which there is no astronomical darkness and for those of us who enjoy the spectacle of a DSO there are also few around to image, especially of the larger Ha-type that my equipment is currently best suited to.  However, there are compensations and with some imagination and a change of tack, it can be a useful time in which to do some housekeeping and return to objects not usually viewed.

I recently noticed that dust and the odd stray fingerprint had appeared on the object lens of my William Optics GT81! Opinion on how to clean this critical element is varied but all advice says: (i) be very careful, and (ii) do nothing unless you absolutely have to; in particular opinion is divided on whether to use alcohol-free cleaner.  I therefore purchased some Baader Optical Wonder Fluid which comes recommended by many but for now confined cleaning to the use of a brush and compressed air to remove the dust and a Lenspen to gently polish the glass surface – the Wonder Fluid will have to wait until another day.

Warm temperatures that accompany summer are also a more comfortable time in which to undertake important tasks outside, such as re-setting equipment alignment, balancing, cable routing etc.  I am therefore also replacing the mount power cable and EQDIRECT adapter cable, both of which look the worse for wear.  Truth is the original cables were poor quality and, mindful of my disastrous camera cable problems this time last year, if possible I now intend to upgrade both these critical items.  The experience of last year’s meltdown showed how prone cables are to low winter temperatures and I now see there are alternative silicon cables on the market – obviously I’m not the only one who’s suffered!

Of course we all want to be outside imaging and observing and a recent spell of very fine, clear, warm nights provided just such an opportunity – but what to do?  There are some popular objects within the Solar System that are worthy of attention at this time of year, which for a change I therefore once again tried my hand at imaging, on this occasion a comet.

There have recently been no less than three notable comets in the night sky:

  • 41P/Tuttle–GiacobiniKresák:  first discovered in 1858, the comet orbits the Sun every 5.4 years and this year was seen from Ursa Minor – Draco – Lyra between March and May.
  • C/2017 E4 (Lovejoy):  only discovered earlier this year by the inimitable Australian comet hunter Terry Lovejoy, the comet rises in the east-northeast above the star Enif in the early morning sky.
  • C/2015 V2 (Johnson): probably this year’s most popular comet, was at full magnitude in Hercules during April but is still clearly evident to the east of Bootes from about 11pm – see below.

V2 CdC

I have only once before imaged a comet, that being C 2014 Q2 Comet Lovejoy (him again) in January 2015, on this occasion I set out to image the aforementioned C/2015 V2 (Johnson).  The comet will soon reach perihelion on 12th June and thereafter leave the Solar System.  Travelling at a speed of 74,000 mph, imaging this small body of ice as it passes Earth is difficult and required going back to basics.  It was also the first time since January that I had used the DSLR camera, which despite longstanding experience required some brushing up.  At first I intended to follow the comet using the Custom Tracker facility in EQMOD but in the end this seemed unnecessary once I had the object centred in the camera and instead I resorted to a number short exposures at high ISO.

v2 orbit

V2 Track I am pleased with the results, though they are a little noisy due to some stupid mishaps on my part along the way which left less imaging time than I would have wished.  Though each comet is different, experimentation suggests that with good framing and guiding, exposures of about 2 minutes and ISO 3,200 produced the best results.  Given this exciting experience, which was also good fun,  I will hopefully not leave my return to comets so long as last time.

Lovejoy Part-2

I first became acquainted with C/2014 Q2 Comet Lovejoy just before Christmas and have since been keen to obtain my own image of the object from Fairvale Observatory; at the time I was fortunate to obtain a photograph of the comet from a fellow astronomer in La Palma.  Despite the comet reaching its best positon on January 7th, some 44 million miles from Earth and with the apparent magnitude (brightness) improving throughout January to less than +4.0, unfortunately nature and life prohibited me from attempting this task: Christmas, New Year, travel, bad weather, full Moon etc.  A couple of clear skies did present a good visual sighting through binoculars but no image.

Last week, on Thursday evening, I eventually got my first opportunity but due to very strong winds (hence the clear sky) was unable to even set-up the equipment.  The following evening a cold but clear sky again occurred and this time I took my chance.

Photographing and processing a comet is not straightforward.  Since my last post, Comet Lovejoy has tracked west (to the right) of the Orion constellation and at the time of imaging was located just above the western end of Taurus, before it passes west of Pleiades on 19th January.  The first problem is therefore obvious – it’s travelling very fast, about 82,000 mph.  Fortunately Livecometdata.com provides real time information on the comet’s journey, which is both impressive (how does it do this?) and very useful.  Inputting the real time RA and DEC location data into the SynScan handset, the mount slewed straight to the comet, which was just off-centre of the field of view.  And thus I had my first, proper live view of a comet – fantastic! Now for the tricky part: how to get an image?

I had already posed this question on Stargazers Lounge and had a number of useful suggestions. Of course, whilst the mount tracks the celestial sphere, the comet is making its own way through the sky, which is not the same path as the stars seen from Earth; I believe it is possible to track the actual comet but that’s too difficult for me. Therefore, it is necessary to err towards lots of shorter exposures to avoid blurring; the longer the exposure the more likely it is the comet’s tail can also be captured in the image but it is a fine line between achieving this and blurring.  In the end I took two sets of images at 20 seconds and 60 seconds – probably too cautious but I was happy with the result and will be better prepared for my next comet, whenever that is.

Then came the next obstacle – stacking and processing.  I had not thought about this before but in the world of stacking, the software is unable to distinguish the comet from stars.  As a result it is necessary to identify the comet in each light frame by manually tagging it; at this point I regretted taking x40 exposures! Deep Sky Stacker will then stack using one of three procedures which basically prioritises either the comet or the stars or a combination of both – I chose the latter.  As usual post processing in Photoshop is then used to improve the final image.

C/2014 Q2 Comet Lovejoy WO GT81 + Canon 550D (modded) & FF | 40 x 20secs @ ISO1,600 + darks | 16th January 2014

C/2014 Q2 Comet Lovejoy
WO GT81 + Canon 550D (modded) & FF | 40 x 20secs @ ISO1,600 + darks | Fairvale Observatory 16th January 2015

Whilst I am very excited to have successfully photographed Comet Lovejoy, I was less than impressed by the stacked image and actually prefer the original.  Processing comet images takes the dark art of processing to a new level and I feel I’ve only reached the learning foothills so far.

Lovejoy will be in the sky for some weeks to come as it tracks across Andromeda and Perseus during February and into Cassiopeia in March.  Whilst the best may be almost past, I certainly hope to follow its progress and, subject to conditions, might even attempt to image it once again before it continues its 8,000 year orbit into deep space.  However, for now I’ve got my comet and am well satisfied – I will spend the intervening winter days practicing my comet stacking.

Comet Lovejoy WO GT81 + Canon 550D & FF | 15 x 60 secs @ ISO1,600 + darks| 16th January 2015

Comet Lovejoy
WO GT81 + Canon 550D (modded) & FF | 15 x 60 secs @ ISO1,600 + darks| Fairvale Observatory 16th January 2015

Christmas Comet

C/2014 Q2 Comet Lovejoy is a long-period comet, only recently discovered by Terry Lovejoy in August; it is the fifth comet discovered by Terry. By December 2014 the comet had brightened to a magnitude of +7.4 and by mid-December had become visible to the naked eye with dark skies.  This weekend on 28th and 29th December,  the comet will pass 1/3° from the globular cluster M79, subsequently brightening in January  to a magnitude of +4.0 to +5.0, as it moves west of Orion and onwards towards Aries and Triangulum, thereby becoming one of the brightest comets for years. On 7th January 2015 the comet will be at its closest to Earth at a distance of 43,600,000 miles.

C/2014 Q2 Comet Lovejoy Transit

C/2014 Q2 Comet Lovejoy Projected Track

Before entering the planetary region in the 1950s epoch, C/2014 Q2 had an orbital period of 11,500 years, after leaving the planetary region in the 2050 epoch it will have an orbital period of about 8,000 years. Thus, unbeknownst to me, it has been with me since I was born and will remain with me for the rest of my life!

I have not seen the comet yet but have just been sent an excellent picture just taken from Joan’s Tacande Observatory in La Palma , which I visited earlier this year.  Of course, I’ll be looking out for C/2014 Q2 at the weekend and hope to follow its journey during the next few weeks and beyond.  Well done Terry and thanks again Joan.

C/2014 Q2 Comet Lovejoy  R120 Canon 350D |  180 secs @ ISO 400 | taken by Joan Genebriera at Tacande Observatory, La Palma, 23rd December 2014

C/2014 Q2 Comet Lovejoy
R120 + Canon 350D | 180 secs @ ISO 400 | Taken by Joan Genebriera at Tacande Observatory in La Palma, 23rd December 2014