Pleiades overnight

A clear, cold night with excellent seeing was the forecast for Monday, 28th November, so I set up in the back yard for an overnight session. Messier 45 “The Pleiades” would clear the tree line at 21.33 (south-east, elevation 53°) and disappear behind the roof line at 02.29 (south-west, elevation 45°) the following morning. Perfect conditions for leaving the system running on its own.

The initial polar alignment of the mount was accurate to 7 arcmin, reducing to 3 arcmin after one iteration of the handset’s feedback routine. Something wasn’t right, as the feedback routine wouldn’t display all the required information to make the proper adjustment, so I had to resort to twiddling the knobs “about the right amount” from an earlier manual calibration session.

3 arcmin of alignment error (with the focal reducer at 636mm focal length) means one pixel of trailing in about 135 seconds, so I set the timer for 90-second exposures with 30-second pauses for the sensor to cool down between frames. 30 frames per hour over 5 hours would net me 150 frames.

My alarm clock went off at 2.30, when I switched off the mount, screwed the end cap on the telescope, set the camera timer to take another 65 “dark” frames and went back to bed. The battery-operated dew heater kept the telescope objective above freezing, but the camera was frosted over the next morning.

150 frames take some processing, and the cooling fan on the Mac was up to full speed by the time I’d finished. Some of the nebulosity has been sacrificed in the processing, as there was a most unwelcome flare in the centre of the photo – probably an urban light source? This target never climbs more than 60° above my local horizon: at its highest elevation, it is due south right across town, and something was the right wavelength to get through my IDAS D1 light pollution filter.

Still a pleasing result for a session devoted to one of the classic targets.

M45 "The Pleiades" Nikon D90 on Altair Wave 115/636 ISO800, 150 x 90 sec.

M45 “The Pleiades”
Nikon D90 on Altair Wave 115/636
ISO800, 150 x 90 sec.

Messier 33

For some reason I never thought I would be able to photograph this galaxy.  Wasn’t it supposed to be too faint, wasn’t the surface brightness too low, wasn’t it a target for much better systems than mine?  I’ve no idea why, but that barrier had stuck in my mind.

Looking for targets on my Sky Safari App, I noticed that the declination (the celestial version of latitude) of M33 gave it a very long track across the otherwise restricted view of the sky from my back yard.  It would rise above the trees to the east and then move quite high across the open space to fall below the roofline to the west some five and a half hours later.

Time for an experiment.  On a night when cloud-free skies cannot be guaranteed, set the system running and leave it to its own devices: choose an exposure length that is short enough to run unguided but take as many frames as can be captured in five and a half hours (that’s a longer session than I’ve ever attempted).

Why unguided?  Well, a guided system has to be attended all the time.  If a cloud passes across the field of view of the guide scope, the system loses the guide star and stops guiding.  All subsequent frames probably have to be thrown away, so a guided session needs a greater guarantee of clear skies if it is to be left running while the operator sleeps.

On the 2nd of October I set up the AZ-EQ6 mount and polar aligned to one arc minute.  All other things being equal,that should allow my system’s resolution of 1.41 arcseconds per pixel to take unguided exposures of 300 seconds without star trailing.  I set the timer to 150 seconds, giving a plentiful margin to absorb other imperfections in the tracking system.  With a 30-second pause between frames, allowing the sensor time to cool down, I’d be taking 20 frames per hour.

Next morning, all had gone as planned.  That doesn’t always happen!  Clouds had interfered as expected, so I took the best 58 frames from the session to stack and process.  Despite the relative humidity of 80-90% throughout the night, the result is a most pleasing rendition of Messier 33 “The Triangulum Galaxy”.  It is about 3 million light years away and is the third largest of the “Local Group” of galaxies which includes the Milky Way and the Andromeda Galaxy.

M33 The Triangulum Galaxy 58 frames of 150 sec, ISO 800, Nikon D90 through 805mm focal length telescope, f/7

M33 The Triangulum Galaxy
58 frames of 150 sec, ISO 800, Nikon D90 through 805mm focal length telescope, f/7

Mercury transit

Mercury_sequenceOn 9 May 2016, shortly after 12 noon, the planet Mercury passed across the face of the Sun and the whole transit, lasting over seven hours, was visible from the UK.  Resistance is futile, and the prospect of the transit screamed “TIME LAPSE VIDEO!” even though Mercury would be only 9 pixels in diameter on the 12MP sensor of my Nikon D90.

I reckoned that about 15 seconds of video would balance the attraction of seeing Mercury crossing the edge of the Sun against the potential tedium of watching a black dot crawl across a white disc, so I settled on 400 frames at 10 per minute – 40 minutes of transit – rendered at 30 frames per second for a smooth video of a tolerable 13 seconds.

Mindful of the seasickness-inducing bounces of the Sun in the viewfinder during my solar eclipse time lapse, and the hours I spent realigning some 800 frames by hand, I set up the mount the previous night and aligned it as well as possible using the limited view of the stars from my back yard.  After the third iteration, the handset reported polar alignment to below one arcminute of error.

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Focusing on the Sun would be the next challenge, so I decided to pre-focus and leave the camera in place overnight.

This is the focusing frame through the Bahtinov mask and…

 

 

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…a quick five-minute unguided frame of Arcturus.  I went to bed happy.

 

 

 

 

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Next morning, the sun rose in a cloudless sky and the kit was waiting exactly as I left it.  Restarting the mount from the “Park” setting was faultless, and the GOTO put Mercury (and therefore the Sun) right in the frame first time.  The temperature change from night to day meant that the focus was awry, so I spent time refocusing using a sequence of trial-and-error photos and a felt tip pen on the focusing knob.

 

 

The reminder alarm went off at 12:10 and I started the sequence on the timer.  This device will take up to 399 frames, which suited me perfectly.  With the mount and the camera running on mains adapters rather than batteries, there was little to do but relax and enjoy the sunshine.  I watched the black dot creep onto the white disc through the viewfinder, so I can say absolutely that I observed the Mercury transit as it happened.

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After 400 frames, conditions were so good and the quality of the images was so strong that I swapped the memory card in the camera and reset the timer for a second batch.  40 minutes later, same again.  And again.  And again.  By the time the Sun moved behind the house, I had accumulated 1,887 frames, so the resulting video covers over three hours of the transit and lasts 63 seconds.

There are two versions of the video – the first is sharpened using Adobe Camera RAW then the frames are cropped and the Sun is centered in each frame using an excellent piece of software called PIPP.  The second version includes a digital zoom created with further cropping.  There’s still quite a shimmy on the Sun, but I can’t process that out – much of it is down to atmospheric conditions.  It is tempting to try and align all the subframes by reference to the sunspots, but the Sun can be seen to be rotating over the course of the video so that wouldn’t work.

 

 

What can be achieved with relatively modest off-the-shelf kit and a little planning never ceases to amaze and delight me.

New Year’s Day Comet While Changing A Wheel

Sometimes it’s really hard to motivate yourself to get up at 3am for astronomy.  I’m more of a late night person myself, and early mornings are not my style.  One way to make it happen, to get that motivation going, is to share your intention with a friend – preferably one who is relying on you for a lift.  So it was that I set my alarm for 02:50 on New Year’s Day.  Clear skies and the knowledge that a fellow enthusiast was doing the same, meant that I was up and out in about ten minutes, including making a flask of coffee.

When I picked Stuart up in the centre of Kendal, he’d already bagged the Aurora Borealis – the Northern Lights, if you prefer – at around midnight that same night.  His dedication to the cause is beyond all understanding, and puts my meagre efforts to shame!

We had two options: a site at the top of Shap Road – dark, clear, cold and very exposed (ideal for stargazing) – or the church car park at Old Hutton – not quite so dark, low lying (so prone to localised humidity), still cold but nowhere near as exposed.  Stuart reported very strong winds across Shap Fell at midnight, as had been forecast, so we set off on the short drive to Old Hutton.

About a mile before we arrived, we found the road closed at a barrier, so turned off to the left on a tiny side road and navigated round a big loop to rejoin the main road on the other side of the diversion.  The side roads were a real mess, and somewhere in the darkness I hit a massive pothole.  By the time we arrived in the church car park, the front tyre was completely flat.

Keeping to the right priorities, we both set up our systems and started taking photos.  There followed some stargazing, some musing on the recent awful weather, some discussion of my much-anticipated observing evenings for the Eddington Astronomical Society, a review of Stuart’s aurora photos from earlier that night, some coffee drinking, and of course much delight in the images now coming off the backs of the cameras.  Eventually, though, we just had to attend to the wheel change.

Everything went smoothly until the nearside front wheel was jacked up in the air and the wheel nuts were off.  The wheel itself just wouldn’t budge, and our efforts to dislodge it by repeated and ever-more-vigorous kicking came close to waking the neighbours and/or sending the car toppling off the jack.  5am, New Year’s Day, remote village in Cumbria, no signal.  Hmmmm….  Only a joint effort, one pulling the wheel while the other aimed kicks at the opposite side, eventually freed it.  Phew!  Suffice to say that the rest of the session went very well indeed.  The conditions looked good – but they can be quite deceptive at Old Hutton as the local shape of the land collects moisture in the air – so the photo sets were as good as we could have expected.  Some hazy cloud lingered high in some frames, but nothing to stop us until about 6.30 when mid-level clouds started to spoil the view.

I took a series of 2-minute frames and 3-minute frames (all unguided) of C/2013 US10 (Catalina) at its closest approach to Arcturus, the brightest star in the constellation of Bootes.  Given the moisture in the air, the close proximity of the bright star, the Moon just 38° from the comet and all that other stuff going on, I was pleased with the result.  Given also that the weather in Cumbria has spoiled all plans for astrophotography for the last eleven weeks, it just felt good to be out again.

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Comet C/2013 US10 (Catalina) passes half a degree from a very hazy Arcturus
Nikon D90 through Altair Wave 115/805 reduced to f/5.5
11 x 3 minutes, ISO 400

I hope we find the opportunity for  a few more of these Stuart!

Fireworks in the sky

NGC6946 is known as “The Fireworks Galaxy”, probably because of the distinct array of colours found within, from the deep yellows of the dying old stars at its centre to the hot blue clusters of younger stars in its outer arms.  It presented almost at zenith just after the onset of astronomical full darkness last week, so I set up in my reasonably dark lay-by on the A591 and spent the whole evening – until about midnight – imaging this one target.  Immediately next to the galaxy, from our point of view, is NGC6939, an open star cluster that lies within our own galaxy.

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Star cluster NGC6939 with galaxy NGC 6946.
Nikon D90 on Altair Wave 115/805
ISO 800, 10x600sec

The star cluster is about 5,000 light years away, and the Fireworks galaxy is about 22 million light years away.  That’s still difficult to grasp, looking at them together in the photo.  It’s like snapping Kendal Castle from my bedroom window and glimpsing the Taj Mahal in the background.  Crazy perspective.

Visually, the galaxy is very small, only about 10 arc minutes (one third of the Moon) in diameter.  At magnitude 9.6, it is well below naked eye visibility.  I guess I would have liked better quality from the image, but the local conditions were not helpful that night – light, humidity and an unfortunate number of cars driving by on full headlights.  There’s another obstruction, which is that this galaxy is in line with the plane of our galaxy, so the photo is taken through the permanent clouds of interstellar dust at the edge of the Milky Way.

The dilemma of self-interest -v- public outreach on eclipse day!

The solar eclipse of Friday 20th March 2015 presented a real dilemma: as an enthusiastic and committed member of the Eddington Astronomical Society, I wanted to be part of the event organised in Kendal, but as an individual amateur astronomer/astrophotographer, I wanted to see (and film) the eclipse.  Kendal was forecast to be under cloudy skies, but a couple of hours drive would take me away from all my EAS colleagues, two radio stations and 500 enthusiastic members of the public, beyond the edge of the cloud layer to full sunshine.

After much soul-searching the night before, I set the alarm for 4.30am.  The first job was to check the forecast again – yes Kendal was still going to be cloudy, but Oswestry (about half an hour south of Chester) would be clear.  Self interest won the battle, so after a quick coffee and a final kit check, I hit the road.

This was my intended destination, from Google Maps.  I liked the look of the car park at bottom right, with unimpeded views over the golf course.

Oswestry

Mile end

car park view

I arrived in good time to go and say Hi to the staff at Little Chef, use their facilities and buy a Cappuccino, then on with setting up the rig.  The AZ-EQ6 mount will take two scopes in Alt-Az mode, so I had rehearsed a configuration with the Altair Wave 115 carrying the Nikon D90 on one side, and the Skywatcher Evostar 102 with a 15mm eyepiece on the other.  A triple thickness of Zoltan Trenovski’s business card was needed as a shim to align the tubes just right.

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A couple of test frames to check the focus and the exposure:

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too bright…

sun out of focus

too blurred…

Focal length 636mm f/5.53 1/400 sec ISO 200

Focal length 636mm f/5.53 1/400 sec ISO 200   Just right!

At six frames per minute, within 10 minutes there’s a clear view of the eclipse starting.

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After 864 frames and a weekend of aligning and processing, we have half a minute of time-lapse video 🙂

There’s lots more to be said here – other people had had the same idea and we spent time comparing notes, the wonderful manager of Burger King / Little Chef kept bringing me free coffee and letting her staff come out to take a look through the telescope, everyone who used the carpark came to have a chat, and of course someone had brought a colander…

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The coffee supply!

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Doing optical experiments with kitchen equipment…

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Spotting scope and a beautiful Televue both with solar filters.

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I hope that some of the wonderful characters gathered in the carpark that morning will manage to get in touch and send their photos to simon.white@simoninthelakes.co.uk so that I can display them here.  I’ll update this post with anything they wish to add.