Lunar eclipse 28 September 2015

Torn between astrophotography and sleep for this one!  Our walking holiday on the Amalfi coast had finished on Saturday with a beautifully long slow lunch among friends on the terrace at Leonardo’s in San Lazzaro, and our late flight out of Naples finally put us down at Gatwick at about 11.30pm.  Overnight hotel at the airport, train journey to have lunch with my mother-in-law (where we had left the car) then a five-hour drive home to Cumbria.  We arrived home in the early evening on Sunday, ready to drop.

The Moon was set to move into the Earth’s full shadow at about 2.15 Monday morning, so I set the alarm for 1.30, as you do.  The forecast was good, it had been improving steadily over the last couple of days, and I guessed that if I woke up and looked out just before the start of the action I would be able to decide whether it was worth setting up a session.

1.30 brought glorious clear sky and an added bonus: the Moon’s position meant that I could catch at least a couple of hours from my own back yard.  That was the deciding factor – just the trusty DSLR on a tripod with the 300mm telephoto lens.  This was the view at the start, reproduced actual size in the viewfinder:

2.06am. The shadow is just visible. Nikon D90 through Nikkor Nikon 300mm f/4 AF. 1/1250 sec f/8, ISO 800.

2.06am. The shadow is just visible.
Nikon D90 through Nikkor Nikon 300mm f/4 AF.
1/1250 sec f/8, ISO 800.

I decided to take one shot every 30 seconds, with the intention of stitching them together as a time-lapse video.  Of course the Moon drifted fairly quickly across the frame so the tripod had to be adjusted every few shots.

2.45am: 40 minutes into shadow.

2.45am: 40 minutes into shadow.

By the time the Moon was about to disappear behind the house, it was in full eclipse.

3.12am: increased exposure to see the illumination in full eclipse. 1 sec @f/5.6, ISO 1000.

3.12am: exposure increased to see the illumination in full eclipse.
1 sec @f/5.6, ISO 1000.

Noticeably very red to the naked eye – and the camera – it was somewhat of a disappointment in binoculars as the brightness dropped so significantly.  This could be because the Moon was almost at perigee (the so-called “supermoon”), closer to the Earth than normal and therefore deeper into the cone of the Earth’s shadow.  The air went a little murky too, so the final shots lost some definition.

Each frame had to be cropped and realigned to make the video run smoothly.  Stitched together and reduced from 4288 x 2848 to 1000 x 1000 pixels, these make a reasonable time-lapse.

Stitching!

I now write a regular piece for the Eddington Astronomical Society, setting out what’s going to be on view in the night sky each month. In all honesty, it will probably lean towards astrophotography!  You can see the March 2014 version here.

One of the opportunities identified as coming up in March was the view of Jupiter reaching its highest point in the sky, elevated 59° in the early evening of the 13th. This looked like a challenging photo project, with bright Moon, bright Jupiter, bright and faint stars and the inevitable Morecambe Bay glow. It would also be at its best during twilight.

Sadly the Cumbrian rain was forecast for that evening, but we enjoyed a few days of high pressure just before then, with a couple of clear nights.

On Tuesday, 11th March, I strolled up to the Mushroom on Scout Scar with no more than camera and tripod. The 18-200mm zoom is pretty wide at 18mm, but I wanted a field of view of about 150°, so I set it to 24° and took nearly forty frames in a grid pattern looking south.

Photoshop can stitch shots together to make panoramas, but it needs clear points of reference in the shots and can only run on automatic. So, if it can’t identify the overlapping shots itself, there is no option for user-intervention. It simply doesn’t work on night sky mosaics.

That’s when I found PTGui, a programme that does exactly the same, but with a much wider range of projection options and, most importantly, the facility for the user to identify the overlap points (ie the stars) manually.

Here is the result, the view south from Scout Scar, Tuesday evening13th March. The sky isn’t flat, of course, and stitching frames requires distortion according to various rules depending on the projection settings. Circular projection seems to give the best compromise on distortion, then I cropped the result to a nice tidy rectangle.

All frames ISO 1600, 10 seconds 24mm f/5.6.

Big sky!  Nearly 40 frames stitched in PTGui, each 10 sec ISO 1600, 24mm f/5.6

Big sky! Nearly 40 frames each 10 sec ISO 1600, 24mm f/5.6, stitched in PTGui

PANSTARRS through floodlights in the sky

Inspired by several astrophotographers around the world posting images of the amazing tail developing on PANSTARRS, I decided to have another go at this comet.  There is a minor road / very long layby running parallel to the A591 on the hill between Kendal and Staveley, with unimpeded views to the north.  I reckoned it would be almost as good as driving into the Kentmere valley.

En route, I dropped by Helsington Church again, to see how the planetary alignment was changing over the Langdales.  Jupiter, Venus and Mercury were now in a straight line and all clearly visible.  I met a delightful family who had come to look at the sunset after spending the day in Kendal, and we passed such an enjoyable half hour with my binoculars spotting planets that I forgot to take photos.

On to the layby, and quite easy to set up with Polaris visible in almost enough twilight to see the mount dials.  Hold on though, that northern sky is getting brighter, not darker!

18mm f/3.5, ISO 1600 1 sec.

18mm f/3.5, ISO 1600 1 sec.

Yes the noctilucent cloud season is under way.  I can’t make up my mind about these clouds that are only visible at night – is this astronomy or meteorology?  Yes, they are really pretty to look at, with amazing variation and complexity in their structure, but that’s Cassiopeia up there, and my dark sky location is ruined.

18mm f/3.5, ISO 1600 1 sec. Two High Pass filters: 40 pixels and 4 pixels.

18mm f/3.5, ISO 1600 1 sec.
Two High Pass filters: 40 pixels and 4 pixels.

Sharpened in Photoshop, the structure resembles waves on a beach.

Prompted by a comment on Noctilucent Clouds 2013, I have experimented with sharpening these images using two Photoshop techniques: Unsharp Mask and High Pass Filter.

NLC plain

50mm f/8, ISO 1600, 3 sec.

The unsharpened image.

NLC USM 200% 4P

50mm f/8, ISO 1600, 3 sec.
Unsharp mask 200%, 4 pixels.

Unsharp mask – Photoshop’s main choice of sharpening tool, but the effect can be seen across the whole image.

NLC HP40SL HP4HL

50mm f/8, ISO 1600, 3 sec.
High pass filter 1: 40 pixels, soft light blend.
High pass filter 2: 4 pixels, hard light blend.

High pass filter – this sharpens only regions of higher contrast ie edges, that benefit from sharpening but leaves the rest of the image untouched.  I picked up this tip from Nik Szymanek in a workshop at the International Astronomy Show in Leamington.  Nik was using it to enhance detail in galaxy images, but the principle applies just as well to noctilucent clouds.  I prefer this sharpening effect which doesn’t introduce the “sharpened feel” artefact to the whole canvas.

Anyway, eventually the light fades and I catch seven reasonable frames of PANSTARRS.

PANSTARRS passing Mag 4.3 Yildun and its Mag 5.8 partner "24 Ursa Minor". Yildun is the next star to Polaris in the tail of Ursa Minor. 200mm f/5.6, ISO 3200 7x3min.

PANSTARRS passing Mag 4.3 Yildun and its Mag 5.8 partner “24 Ursa Minor”.
200mm f/5.6, ISO 3200 7x3min.

Yildun is the next star to Polaris in the tail of Ursa Minor.

North is to the lower left of the shot, and the glow from the pesky noctilucent clouds can be seen in the comet’s tail – which is pointing pretty much towards the Sun.  I shouldn’t really moan about the cloud, as the Sun is only 13 degrees below the horizon so it’s not exactly dark anyway (from an astronomical point of view).

PANSTARRS time-lapse video – processed

The unprocessed version of this video was rather disappointing. See PANSTARRS time-lapse video for details.

I took a fresh look at Fred Espinak’s videos of PANSTARRS, and compared our exposure settings. Fred’s videos used the same camera and lens as mine, but he chose f/5.6, ISO 800, 2 sec and ISO 1600, f/5.6, 4 sec. My settings of ISO 400, f/8, 2 sec are two stops and four stops respectively darker than Fred’s, and it shows.

This version of my same video has been reprocessed in Photoshop to boost the exposure by two stops. It’s crude, but shows how much better that choice of setting would have been. I have also taken the opportunity to sharpen the frames a little, and crop too. The cropping accentuates the judder of the movement caused by taking a two-second exposure every five seconds – and processing to play at 15 frames per second.

Fred Espinak’s video of PANSTARRS with the Moon is just stunning.  Arizona does have wonderful skies.  Cloudy skies in the North-West of England are very frustrating, but I live here by choice, so shouldn’t grumble.  On the other hand, it would be nice to have another go at this comet before it fades away.

Prizewinner!

The Eddington Astronomical Society runs a photography competition for members, and the 2012 submissions were judged by astronomy journalist, author and lecturer Dr Stuart Clark.

Prime focus through Evostar 102: 1000mm f/9.8, ISO 800, 1/40 sec.

Prime focus through Evostar 102: 1000mm f/9.8, ISO 800, 1/40 sec.

Dr Clark judged this one of mine to be best in the “Through the telescope” category.  I’ll thank him in person after his lectures at the International Astronomy Show on 17th/18th May 2013.

M31 Andromeda first attempt: fixed tripod

The moment of revelation that turned me on to the possibilities of amateur astrophotography occurred on the evening of 5th March 2012, when Jeremy Hunt (not that one) came from Cockermouth Astronomical Society to present some examples of his work in Kendal.  All his slides included a note in the corner, giving details of the focal length of the lens used.  In the Q&A, I commented that there must be something amiss – if only with my understanding of the process.  If he had taken that photo with, say, the 300mm lens as noted, then he must have enlarged or cropped it because I knew the object in the sky simply wasn’t that big.  Jeremy’s answer turned my understanding on its head: “It is that big, it just isn’t that bright”.

Some of the night sky objects are visually enormous.  The reason that we cannot see them is not that they are small, but that they are faint.  Next time you look at the full Moon, imagine 12 of them arranged six by two like eggs in a dozen box.  That’s the visual size of M31, the “Andromeda” galaxy.

The key to photographing faint objects in the night sky is not magnification, but exposure.  You don’t need a long lens, but you do need to hold the shutter open for a long time.  Unfortunately for the astrophotographer, the sky moves (the Earth rotates) so long exposures of stars appear as lines rather than dots.  Holding the camera stationary for long exposure against the rotating Earth requires technology which I didn’t have for my first attempt at M31.  However, using a 50mm lens and 5-second exposures meant I could get satisfactory results from a fixed tripod.

50mm f/1.8, ISO 3200 5 sec.

50mm f/1.8, ISO 3200 5 sec.

This is a 5-second frame using a standard 50mm manual lens at full aperture.  There is nowhere for lens defects to hide in astrophotography, and the distorted shape of the stars towards the edge of the frame is a fine example of coma.  Coma is most noticeable at wide apertures, and can be fixed by stopping the lens down.  I took 40 frames of 5 seconds and stacked them using the free software “Deep Sky Stacker“.

50mm f/1.8, ISO 3200 5-sec40 frames stacked in DSS

50mm f/1.8, ISO 3200 5-sec
40 frames stacked in DSS

This is the stacked result, cropped to pick out the galaxy.  It’s not brilliant, but it is:

  • an object that is almost invisible to the naked eye
  • photographed with a standard lens from a fixed tripod
  • stacked using free software

From here, as the song says, the only way is up.