Harvest Time

September 30, 2015 by grahamrob in Imaging, Solar system and tagged Lunar Eclipse, Moon, Photography | 2 Comments

Thanks to Copernicus and Kepler et al, astronomical events are highly predictable; unfortunately the same cannot be said about the weather. Since taking up astronomy and despite favourable predictions of clear skies, I have frequently been thwarted by incoming cloud or worse. When communicating with each other astronomer’s often use the closing of “Clear Skies”, no wonder given the continuous battle we have just to see the sky at night, let alone image it!

Such was my experience in 1982. At the time I lived and worked in northern South Africa, close to the border with Botswana and the Kalahari Desert. A lunar eclipse was forecast and in this part of the world there was usually a good chance of a clear sky. Unfortunately, it was not to be this time either. We saw glimpses of the eclipse through brief gaps in the otherwise thick cloud that was blowing across the sky. I’ve missed other eclipses for the same reason, lunar and solar, and as a result have developed a somewhat resigned mindset towards such events, with the probability that the sky would most likely not be clear. And so despite encouraging forecasts, my expectation for this week’s lunar eclipse was more of the same.

The lunar eclipse of 28^th September was very unusual. At mid-eclipse the Moon was just one hour past its closest approach to Earth in 2015, creating an effect now popularly termed a ‘Supermoon’. Moreover, the rare combination of this and a full eclipse at the same time results in a distinctive red moon at totality.

I have learnt the hard way that in astronomy Rule-1 is perseverance. I therefore carried out all the necessary research on the eclipse, undertook a dry run the previous evening and set-up all the equipment in the early evening before heading for forty winks – it was after all hopefully going to be a long night. The weather had been clear and sunny earlier in the day but was forecast to cloud over shortly after midnight, just before umbral contact! The sky was clear when I went out later but ominously there were clouds in the west. Notwithstanding, the sky remained clear all night and the eclipse was nothing less than spectacular.

Total Lunar Eclipse 18th September 2015

The precision with which astronomical events are plotted is incredible and, guided by various articles and charts all was in place well before the end of the penumbral stage at 2.07am. Shortly before darkness started to show on the top, eastern edge of the Moon and then exactly at 2.07am the eclipse shadow touched and then crept inexorably across the Moon’s surface. This was the main phase of the eclipse when the Moon enters the central, dark part of the shadow called the umbra, eventually reaching totality at 3.11am.

Totality lasted 1 hour 12 minutes, during which I just watched through a pair of 10 x 50 binoculars, which probably was the best way of actually viewing the Moon throughout the eclipse. Of course, with the brightness of the full Moon obscured by the eclipse during this time, the rest of the night sky was plunged into blackness, thus bringing the stars, nebulae and galaxies back to life. As the Moon was passing through the lower part of the Earth’s umbral shadow, the southerly edge appeared relatively bright during much of totality. Totality finished promptly at 4.23am as the light started to move across the Moon’s surface once again like an unstoppable wave. The Moon finally exited the umbra at 5.27am and the show was over until October 2033, on which occasion the Supermoon eclipse will unfortunately not be visible from the UK – I did say it was rare. However, there will be another total lunar eclipse in July 2018, so it’s not all bad news.

Given my history, this was naturally my first time imaging a lunar or any other eclipse and I am very pleased with the results. Other than requiring a clear sky, as usual preparation was the key: understanding the timing and dynamics of the event and considering the imaging possibilities. The most obvious problems to overcome were the Moon’s tracking and movement of the eclipse itself, with its associated impact on changing brightness and contrast for imaging.

The previous evening had also been clear, so I tested a basic DSLR + tripod set-up using an intervalometer to trigger the shots at 5-minute intervals. With the 200mm telephoto lens 8 pictures were successfully recorded as the Moon tracked across the image frame, at 100mm this increased to 12 pictures; however, the track tended to move out of the side of the frame early as the Moon follows an inclined rather than horizontal track. Altogether it was a successful and useful experiment for the next evening.

On the night I used the William Optics GT81, with a Canon 550D camera and field flattener, which continuously tracked the Moon and eclipse, imaging at 1-minute intervals throughout the period inward and outward of the umbra and manually during totality. Using a fixed ISO 100, it was necessary to continually change the exposure time every five or so minutes in order to compensate for the aforesaid changing light conditions. In addition, I again used the intervalometer with the Canon 700D and the 55- 250 mm telephoto lens on a camera tripod.

Eclipse: Inward sequence from umbral contact to totality WO GT81 + Canon 700D + FF | 1/500 to 1/3 sec @ ISO 100 | 18th September 2015

Eclipse: Inward sequence from umbral contact to totality
WO GT81 + Canon 550D + FF | 1/500 to 1/3 sec @ ISO 100 | 28th September 2015

Eclipse: Exit sequence to full Moon Canon 550D + tripod | >=1/160 sec @ ISO 400

Eclipse: Exit sequence to full Moon
Canon 700D + tripod | >=1/160 sec @ ISO 400

Eclipse animation

The results from both methods turned out well. With superior optics and tracking, the WO telescope images were naturally better in quality and magnification. However, the alternative simple camera set-up also produced a pleasing record of the eclipse, perhaps in some way capturing the mood better?

The entire event lasted just over 3-hours, during which found it necessary to look away from the imaging process at times just to enjoy this unusual and exciting spectacle. The name Harvest Moon is given to the full moon closest to the Autumn Equinox, recognising the time of year at which the crops have been gathered and can itself be an attractive sight. The coincidence with an eclipse makes for a rare and dramatic occasion, which this time I was able to enjoy completely cloud free from beginning to end – well that’s a first.

Harvest Moon at Totality WO + Canon 700D + FF | 1/3rd Sec @ ISO 400 | 28th September 2015

Harvest Moon at Totality
WO + Canon 550D + FF | 1/3rd Sec @ ISO 400 | 28th September 2015

The Pelican & The Phoenix

September 22, 2015 by grahamrob in Deep Sky Objects, Equipment, Imaging and tagged Cygnus, DSO Imaging, Nebulae | 2 Comments

As we pass the Autumn Equinox the promise of long and exciting Winter skies is not far off but there are still some wonderful late Summer features around worth imaging before they move away from the Meridian and out of view from Fairvale Observatory. Following a major operation earlier in the year I’ve been unable to move the heavy equipment outdoors until very recently and have therefore almost completely missed the Summer skies; even as I’ve been getting better in recent weeks, poor skies and other circumstances have stopped my return to astronomy – until now.

Up until shortly before midnight the Cygnus constellation is favourably located close to the Meridian at the moment and at a very high, southerly altitude – perfect for my location – it was therefore here that I chose to make my long awaited resumption to astroimaging last Saturday. The weather forecast in the morning showed clear skies for that night but by early evening had changed to cloud and looked like being another lost opportunity; on this basis the Flamsteed Astronomy Society had already cancelled their planned evening astronomy session. However, unlike previous attempts in recent weeks when clear skies were forecast and the cloud rolled in unannounced, this time the outcome was very different, with a clear moonless sky throughout the night – I sometime wonder if the weather forecasters have windows and bother to look outside!

Located northeast of the first magnitude star Deneb and some 1,600 ly from Earth is NGC 7000 or the North America Nebula, an enormous H II region that in outline resembles the North American continent. I first encountered this emission nebula at a similar time last year, which was my first experience of such a feature and I was therefore thrilled to capture part of it in my picture; my blog title at the time captures my feelings – WOW! However, taking the image using the longer focal length Skywatcher 150PL with a smaller field-of-view (FOV), the picture only captured part of the ‘USA’ and the ‘Gulf of Mexico’. Furthermore, using an unmodded camera much of the red H-alpha light that is characteristic of these nebulae was not recorded.

Since then my equipment has changed in a number of important ways, so that the William Optics GT81 with a wider FOV would now enable me to image more of the nebula, whilst using a modded DSLR camera would also record much more of the H-alpha light; an additional year’s experience also helped. This time my target was the related IC 5070 and IC 5067 H II regions otherwise known as the Pelican Nebula, situated just west of NGC 7000 and close to Deneb.

The Pelican Nebula, IC5070 & IC 5067. WO GT81 & modded Canon 550D + FF | 30 x 120 secs @ ISO 1,600 + calibration | 19th September 2015

The Pelican Nebula, IC5070 & IC 5067
WO GT81 & modded Canon 550D + FF cropped | 30 x 120 secs @ ISO 1,600 + calibration | 19th September 2015

With an apparent magnitude of +8 the Pelican is generally less bright than its larger +4 neighbour but is no less exciting. The bright double star Cygnus 57 and binary Cygnus 56 shine conspicuously just in front of the ‘bird’ and within the ‘body’ respectively. In addition a bright area at the northern top of the ‘bird’s head’ is an active area of star formation, which ionizes the gases creating the glowing red area.

Whilst missing the impact of being my first H II nebula last time, the larger image of the North America Nebula now captures most of the ‘continent’ and encompasses ‘Central America’. As a result the picture clearly shows the Cygnus Wall, another bright area of star formation that runs along ‘Baja California’ / ‘northern Mexico’ area.

NGC 7000 The North America & Pelican Nebulae
WO GT81 + modded Canon EOS 550D + FF | 30 x 120 secs @ ISO 1,600 + calibration | 19th September 2015

The combined Pelican and North America Nebulae span some 50 ly across, which when imaged together makes a wonderful picture of these spectacular features. I would be happy with this image at any time but after nearly six months away from astroimaging it’s a very pleasing result. I feel re-invigorated, like the phoenix has risen again.

Fly me to the dark side of the Moon

September 15, 2015 by grahamrob in Earth, Solar system, Widefield Imaging and tagged Moon | 3 Comments

I am still struggling to return to astronomy – no longer hampered since July recovering from my knee operation, which though stiff and painful is slowly improving, but now by the weather, a one-eyed cat, my own incompetence and inevitably the Moon.

Taking care of my daughter’s cat in early August, ruled out astronomy as the unfortunate one-eyed cat is not allowed outdoors, thus making the movement of equipment freely in and out the house very difficult. The weather then turned bad before it was time for the full Moon at month end, itself an imaging opportunity, except once more for the presence of thick cloud cover. Shortly afterwards clear nights were forecast but twice after setting-up the equipment under a clear sky the clouds rolled in again. Finally a week ago under a moonless clear sky, I completed the equipment set-up and turned on the mount in order to start the alignment and camera set-up sequences.

I’ve owned the current equipment since last July and after months of busy use felt I was now familiar with all the basic procedures – wrong. Because of my operation it’s been five months since using the equipment and after going through the initial SynScan sequence I started the alignment routine, only to find that each time the scope slewed to exactly 90⁰ east of the target star. I diligently repeated the start-up routine a number of times but with the same result – bizarrely on switching to EQMOD linked with Carte de Ciel, the scope moved correctly to the chosen star. It seemed there was an obvious answer to the problem but I could not work it out and in the end had to give up, missing a great opportunity as the sky continued clear all night – talk about frustrating!

The next morning I went through the complete mount set-up and SynScan start-up routine again, with a clear head and some guidance from SGL members, it took me about 10-seconds to find the problem – I had input the date as day-month-year instead of month-day-year; in this case 06/09/15 was exactly three months or one quarter earlier than the correct date input of 09/06/15, the sky equivalent of 90^o. Why is it in the 21^st Century that an advanced technologically advanced country such as the USA, uses an uncommon date format and imperial units, they even mix-up themselves and as a result lost the Mars Climate Orbiter in 1999! Notwithstanding, from frequent use I already knew the correct format but after 5-months absence couldn’t see the problem right in front of me, obvious though it was.

In the absence of ‘real’ astronomy I’ve been playing with simple camera-tripod imaging, with some rewarding results; it’s got me thinking about purchasing a smaller, simpler Vixen Polarie or equivalent tracking mount head – watch this space! The same morning after sorting out the aforementioned date format problem, I took the opportunity to take a look at the sun in the east before turning round to see a beautiful waning crescent Moon in the western sky – who needs the night sky?

Fly me to the Moon

Too good to miss and after the previous evening’s disaster, I managed to get a pleasing sequence of images tracking an aircraft flying past the Moon – this being a case of making the best of what you have: daytime, the Moon and frequent overflying planes from nearby Gatwick airport and further afield. Being approximately 42,000 further away from Earth the Moon only looks about 4-times larger than the aircraft.

Flight animation

Changing the perspective completely, I was fascinated by last month’s image of the Moon passing in front of Earth, thus also presenting a fabulous view of what we call the dark side of the Moon. The transit was taken from the Deep Space Climate Observatory orbiting at 930,000 miles from Earth, or nearly four times greater than the Moon.

16th July 2015: The so-called dark side of the Moon, seen from the Deep Space Sky Observatory, as it passes across Earth. From our perspective that day it was a New Moon.

16th July 2015: The so-called dark side of the Moon, seen from the Deep Space Climate Observatory, as it passes across Earth. From our perspective that day it was a New Moon.

Pink Floyd take note – surely this image needs to replace the iconic cover from their 1973 album – it’s all about changing perspective; apart from being a spectacular photograph the image demonstrates the other side of the Moon is anything but dark!