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).

Planetary alignment and faking it

On 26 May 2013, Jupiter, Venus and Mercury gathered close together in the sky and it looked as though they would set over the Langdales in a triangle that just begged to be caught on camera.

I went out to rehearse the previous evening and it looked spectacular.  Sunset over the Langdale skyline from the outskirts of Kendal can make for a stunning vista.  Here are the three planets in not-quite-perfect alignment, with a multiple exposure shot to give an idea of their setting trajectories:

Jupiter, Venus, Mercury over the Langdales

25th May 2013: Jupiter, Venus, Mercury over the Langdales.
That’s Jupiter on the left, Mercury at the top, Venus over Pavey Ark

Jupiter looks to be on a collision course with the edge of Harrison Stickle, and about an hour later it set exactly as  expected.  Multiple exposure again:

Jupiter setting behind Harrison Stickle

25th May: Jupiter setting behind Harrison Stickle

On the 26th, it was cloudy.  Oh well, that’s life in Cumbria.  Time to get creative, so here’s a fully stacked version of all the shots, so that we can see the exact configuration of the three planets:

Fifteen or so layers on a cloudy evening, catching planets through the moving gaps in the clouds.

26th May: Fifteen or so layers on a cloudy evening, catching planets through the moving gaps in the clouds.

So what would we have seen if not for the cloud?  Well, using the positions of the planets on the cloudy evening shots, I can move the dots from the rehearsal night and show what was happening behind the clouds:

26th May 2013: "What might have been" Jupiter (left), Venus (right) and Mercury (top) setting over the Langdales.

26th May 2013: “What might have been”
Jupiter (left), Venus (right) and Mercury (top) setting over the Langdales.

Had the clouds not moved in, this would surely have become one of my favourite photos.  In truth, however, it’s nothing but a fake.  Please don’t tell!

PANSTARRS one last time?

This is an awkward time of year for astrophotography. It only gets really dark after the end of “astronomical twilight”, when the Sun dips 18 degrees below the horizon. That didn’t happen until quarter past midnight last night, and by 2am it was back above that 18 degree line. The longest day / shortest night is still six weeks away, so for the next twelve weeks the night sky will be at least as testing as it is now.

These photos were taken in the hour around 1am last night, from the long layby set back from the A591 east of Staveley.

First, the constellation Cepheus:

PANSTARRS approaching Cepheus 50mm f/5.6, ISO 800, 15 min. Single frame of 15 minutes.

PANSTARRS approaching Cepheus
50mm f/5.6, ISO 800, 15 min.
Single frame of 15 minutes.

The 50mm lens gives a 27×18-degree field of view on the D90, so just enough space to accommodate the whole of Cepheus as PANSTARRS (mag 7.2) approaches from Casseopeia.

At ISO 800 all the numbered stars in Cepheus are fully illuminated on the screen, including Erakis (mag 4.1), the “Garnet Star” on the right.

On to PANSTARRS with the 300mm lens:

PANSTARRS approaching Cepheus 300mm f/5.6, ISO 800, 8 min. 2x4 min. frames stacked in Photoshop.

PANSTARRS approaching Cepheus
300mm f/5.6, ISO 800, 8 min.
2×4 min. frames stacked in Photoshop.

PANSTARRS approaching Cepheus 300mm f/5.6, ISO 800, 8 min. Single 8-minute frame.

PANSTARRS approaching Cepheus
300mm f/5.6, ISO 800, 8 min.
Single 8-minute frame.

Two questions are answered here. First, does a stack of two 4-minute frames deliver more than a single 8-minute frame (all other settings unchanged) or is it the other way round? Decide for yourself, but I think there’s more refinement in the layered 4-minute frames and more punch in the single 8-minute frame.

Second, can the EQ3-2 mount track accurately for 8 minutes loaded with the D90 and a 300mm lens? Looks good to me.

At 2am it’s getting light in the east (!!) so time to pack up. I’ve had great fun photographing PANSTARRS over the last few weeks and learned many lessons along the way, but this is probably the last session, given the combination of short, late nights and uncertain Cumbrian weather.

PANSTARRS success from Kentmere

Tuesday 30th April was sunny all day, the last patches of cloud drifting away to the north in late afternoon.  After my previous encounter with humidity and moonlight in Kentmere, it looked like a good opportunity to test this new dark site.

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This is how my setup looks.  Just me, a layby and the EQ3-2 equatorial mount.  At 9.30pm the Sun has already set, but I wanted to leave plenty of time in case it clouded over and I had to dash to another location.  It will be another couple of hours before the Sun is 18 degrees below the horizon, the offical end of astronomical twilight.

Elevation 25 degrees, Sun is 15.7 below horizon.

Elevation 25 degrees, Sun is 16.2 below horizon.

Elevation 25 degrees, Sun is 16.4 below horizon.

These unprocessed frames with the Sun only 15 degrees below the horizon show what a difference that makes to long exposures.

50mm f/2.8, ISO 800, 6 min. 2 X 240 sec. frames stacked in Photoshop.

50mm f/2.8, ISO 800, 8 min.
2 X 240 sec. frames stacked in Photoshop.

Two frames of 4 minutes each, stacked as layers in Photoshop.  PANSTARRS is in the centre, moving from Cassiopeia to Cephus.  The settings of ISO 800 and 240 seconds were inspired by Fred Espinak’s version, using pretty much the same kit.  I guess the difference in our results is an indication that, even on a good night in Kentmere, conditions in Arizona are better.  The thousands of stars in the bottom left corner (Cassiopeia is in the Milky Way) become so indistinct through our 80% humidity that they look like background glow, and any attempt to eliminate them damages the rest of the picture.  On the other hand, it could just be that Fred is much better at this than I am.

300mm f/5.6, ISO 3200, 12 min.
3 x 240 sec. frames stacked in Photoshop

With the 300mm lens, the optimum aperture is f/5.6 so I have wound the ISO up to 3200 to compensate.  Four minutes tracking with the 300mm lens is quite satisfying, with the stars showing no sign of trail.

PANSTARRS is passing close to two nebulae, Cederblad 214 and NGC 7822, between Cassiopeia and Cephus.  While neutralising the background, I notice that I have caught some nebulosity in Cederblad 214 – that’s the reddish glow to the right of PANSTARRS.

The comet itself still has two distinct tails.  The ion tail points away from the Sun (towards one o’clock in this photo) and the dust tail trails behind the comet (towards nine o’clock in this photo).

300mm f/5.6, ISO 3200, 5 min. Single frame of 300 sec.

300mm f/5.6, ISO 3200, 5 min.
Single frame of 300 sec.

Before packing up, I can’t resist an attempt at a five-minute frame.  The tracking seems to hold up well, which promises much for future sessions.