Perfect alignment

I’ve been having a really troubling time with my new AZ-EQ6 equatorial mount.  I say new, but I bought it about a year ago – second hand – and it has puzzled and infuriated me ever since.

First up, the previous owner had snipped the power supply cable and wired it to a mains adapter.  No problem there, so I undid his modification and wired it back to a “cigar lighter” plug for use with a battery pack.  Despite all the care in the world, I somehow got it wired to the wrong polarity and promptly blew the mother board as soon as I switched it on.

Embarrassing.  Took it to the “repair and service division” of one of the UK’s best known retailers, who smiled sympathetically, wagged a finger, tut-tutted and said they would check it out.  Days turned into weeks, weeks turned into months, gentle reminders turned into an increasingly despairing string of phone calls and emails, and eventually they returned it, fixed.  Their apology for the shameful delay was not to charge me.  Fair enough.  We have since made up – you can’t stay angry all your life now, can you?

There’s no doubt that the AZ-EQ6 is a fabulous mount.  Some evolutionary changes and some revolutionary changes make it so much better than the standard EQ6, so my expectations were really high.  On my old EQ3 mount, I could polar align by eye and track with a 300mm telephoto lens for up to 8 minutes without star trails.  It took a lot of practice, but I could do it time after time.  Here’s Comet C/2011 L4 (PANSTARRS) from May 2013 at those settings:

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.

The AZ-EQ6 is a heavy beast, and I use it out of the back of the car.  Incidentally, it lives in my basement, so each astro-session starts with lugging the boxes up the stairs and out the front door to the car.  Practice makes perfect, however, and I can set it up in the dark in about five minutes, then run through the alignment routine and we’re good to go.

Except we weren’t good to go.  It just didn’t work very well.  The “advanced polar alignment” routine, using feedback from the star-aligned telescope to adjust the polar alignment of the mount, kept producing crazy results.  Crazy adjustments, endless frustrations.  I resorted to drift alignment, convinced that I must be getting something wrong but baffled as to what that might be.

Then we hit rock bottom.  Drift aligning produced near-perfect levels of polar alignment, but the stars still trailed for anything over 60 seconds of exposure, even at a relatively modest 300mm focal length telephoto lens.  After several sessions it occurred to me that the drift was entirely in RA, and the mount drive was therefore running slightly fast.  There was no drift at all in Dec.  I sent an email to SkyWatcher to ask them how to fix it.

The moment I sent that email, it came to my attention that there were a couple of “firmware updates” on the Skywatcher website: one firmware update for the motor drives, one for the handset.  The list of “fixes” for these updates read like a copy of my list of queries.  Maybe, just maybe, I wasn’t doing anything wrong at all.  Could it really be that the mount was inherently faulty?

I downloaded the updates and reflashed the motor drive and handset according to the instructions.  The polar alignment feedback routine is now slightly different, so I took the first opportunity to test it out last night.  After dodging clouds to complete two iterations of the alignment routine, I watched the sky cloud over leaving just one star visible: Vega on the western horizon.  Nothing else to do but take photos of Vega.  Here’s the result – first a couple of frames through the 300mm telephoto lens, spaced 7 minutes apart:

Vega at 20:19 300mm telephoto.

Vega at 20:19
300mm telephoto.  Field of view 4.5º x 3.0º

Vega at 20:26 300mm telephoto.

Vega at 20:26
300mm telephoto.  Field of view 4.5º x 3.0º

That looks good, but it’s not the position of Vega that caught my eye, as that’s impossible to tell without layering the frames together.  It’s the stars at the edge of the frame.  I had become so accustomed to seeing them drift off between frames.

Next, a single five-minute frame:

Vega for 5 minutes. 300mm telephoto.

Vega for 5 minutes.
300mm telephoto. Field of view 4.5º x 3.0º

The image is poor quality because the clouds kept coming and going, but the important thing is that it appears not to be drifting.  On the other hand, I could do that with the old EQ3:  the AZ-EQ6 was supposed to do better than this.

Okay, last test before the clouds completely finish the evening.  Prime focus through the Altair Wave 115/805.  That’s a focal length of 805mm.  I leave the shutter open for six minutes while I start to pack stuff away:

Vega for 6 minutes. 805mm prime focus.  Field of view 1.7º x 1.1º 1.4 arc seconds per pixel

Vega for 6 minutes.
805mm prime focus. Field of view 1.7º x 1.1º
1.4 arc seconds per pixel

A bit fuzzy from the cloud, but it looks pretty solid to me.

That’s six minutes, unguided.  Happy days.  That’s what I believed I had bought in the AZ-EQ6, but had begun to think I’d made a mistake.  Next clear sky, I’ll see how far it can go!

Crescent Moonset

On Tuesday evening 1 April the forecast looked pretty good.  As I packed the car in an optimistic mood for another go at the constellation of Leo, I glanced towards the west and saw the thin crescent Moon about 90 minutes from the horizon.  All plans changed, and I headed out to Helsington church, south-west of Kendal, with good views to the hills of the Lake District on the western horizon.

The Moon looked okay through the new combination of Nikon D90 and Altair Wave 115/805 ED Triplet (hereafter “my telescope”), but only okay.  The humidity was higher than expected, as was the wind speed, and the atmosphere low to the horizon was not going to cooperate.

This was about the best on offer:

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805mm f/7, ISO 800 1/30 sec

Of course this location and composition are one of my favourite combinations, so I switched to the 300mm lens as the Moon approached the horizon.  ISO 800 with the lens wide open at f/4, this is the series of 30-second exposures as the Moon set behind the skyline of the National Park:

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I stopped the mount motor to take one frame with the horizon stationary, which shows how much the Moon was moving over the 30 seconds:

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Clipping that horizon in Photoshop, I can use it to take the blur out of the earlier shots. I’ll leave it to you to decide whether this is an improvement.

Moonset2

Moon and Saturn

The chart said these would be due south at 3.30am on 21 March, elevated 18° above the horizon.  A quick check the previous evening showed that the gap between the tree and the neighbour’s house, viewed across the top of my shed, would just give me an unobstructed view.

I was still awake at 1am, kept getting up to see whether the clouds had cleared, and was surprised when the alarm woke me at 3.00.  I opened the west-facing bedroom window to stick my head out, and saw clear sky to the south – with the Moon exactly as predicted.

Set up the tripod, mount the new Altair Wave 115 – with the Nikon attached as if to an 805mm f/7 lens.  After years of SLR photography, I still think in terms of focal length rather than objective lens diameter.  The field of view with this combination is 1.68° x 1.12°, perfect for this shot as Saturn was just 1.2° from the Moon.

Focusing was very easy with the Bahtinov mask and the dual speed focuser, especially with the Nikon’s LiveView screen zoomed right in on Saturn.  Even though Saturn is a ringed disk rather than a point of light, the changing shape of the view through the mask was obvious.

At ISO 400, trial and error gave 1/250th of a second exposure for the Moon, and 1/30th for Saturn.  By 4am I was quickly layering these together in Photoshop…

Moon&Saturn1440Q100S42

The Moon and Saturn separated by one degree
805mm f/7 ISO 400 1/250 sec (Moon) 1/30 sec (Saturn)

…and back in bed at 4.15, just as the clouds returned.

Supernova SN 2014J in M82

This is one of those quite gratifying occasions when a major discovery in the sky falls within the relatively easy reach of the amateur astrophotographer.

On 21 January, astronomy news feeds were reporting a supernova becoming visible in galaxy M82, close to the constellation of Ursa Major. Here in Kendal, we hadn’t seen much of the night sky since November, but on the night of 22 January, I looked out of the back door just before bedtime and saw clear skies with only the occasional cloud blowing over. An hour invested here would probably bring rich rewards.

In about five minutes I had managed to set up the mount, polar align, balance and focus the 300mm AF-Nikkor (on a conveniently placed Jupiter – that autofocus is a gem!). The next 20 minutes were spent in all sorts of contortions trying to find M82 in the viewfinder. I had set the tripod very low, to minimise vibration, and M82 was very high in the sky. That’s easy with a right-angle viewer on a telescope, less easy in a camera viewfinder. M82 is invisible to the naked eye, so each reframe needed a fresh exposure of about a minute to confirm, but the more frustrating problem was that M82 is so close to the celestial pole that minor adjustments of the mount go off in unexpected directions.

Once found and centered, I managed four reasonable frames of two minutes each before the clouds closed back in. Rather than stack using the usual software, I combined these as simple layers in Photoshop, boosted the contrast a little and tuned out the worst of the background glow of Kendal’s street lights.

About a year ago, I had shot M82 and its more circular companion M81 as a short experiment to mark a galaxy pair that I’d like to image later in more detail. Here is last year’s image, without the supernova (using the old manual 300mm lens):

M82 no nova

M81 and M82, 1 March 2013
300mm f/5.6, ISO 400 30 minutes.
10 frames of 3 minutes.

Then the current image with the brand new dot in M82 (new lens, same focal length, better glass):

M82 nova

M81 and M82, 22 January 2014
300mm f/5.6, ISO 400 8minutes.
4 frames of 2 minutes.

I say brand new, but this galaxy is about 11 million light years away, so this event happened a long time ago and the news has taken a while to reach us.

Before, and after. Not bad for an hour in the back yard between the clouds.

…and for those who couldn’t spot the difference, here it is!

PS layered.jpg

 

Chasing ISON through the clouds – the full story of early morning 15 November 2013

To say that astrophotography in Cumbria is “hit and miss” would be an understatement.  It is mostly miss.  Cumbria, home to The English Lake District, is probably the wettest county in the UK.  When we are not catching the wet weather fronts coming in every few days from the Atlantic, the terrain tends to generate its own weather system, which is likewise cloudy and wet.  This forecast is not untypical:

0010 forecast

Against this backdrop, my astrophotography is based on a simple (EQ3-2) equatorial mount, an RA motor with rechargeable batteries, and my trusty Nikon D90 with a small collection of reasonably good lenses.  My favourite piece of kit at the moment is the WiFi SD card, which means I can review shots immediately on the iPad rather than on the back screen of the camera.  The temptation of further investment in hi-tech astrophotography kit is a constant companion, but yielding would only serve to heighten the frustration (by increasing the sunk cost) of all those cloudy nights.

0020 mysetup

I guess it follows that every outing is tempered with fairly low expectations, as conditions can appear good, then change at a moment’s notice.  On this particular night, my expectations were on the low side – the forecast of “clear intervals” and humidity around 90%, were not very encouraging for a target low on the horizon.  However, my good friend Stuart Atkinson from the Eddington Astronomical Society had texted the previous evening and persuaded me to set my alarm for 3.30am, so I set about planning for our excursion.

My plan for all sessions follows the same rules: (i) examine the star chart to plan the frame and check the timetable, (ii) go to the chosen location and set up whatever the prospects, (iii) don’t be disappointed if the forecast is wrong.

Get the idea?  How I envy those with reliable clear skies!

Rule number one, check the star chart.  On the morning of 15 November, ISON would rise at 04:05 and astronomical twilight would begin at 05:34.  That meant a window of 89 minutes, but for the first 40 of those ISON would be below 5 degrees.  Okay, set up and be ready by half past four, leaving an hour for capture.

At 03:30 the alarm goes off and a quick glance through the curtains suggests a “reasonable” sky.  Load the car, drive past Stuart’s to collect him, then off we go to the east of town where there is a good view to the eastern horizon across open countryside.  There is a small hill which, viewed from my observing spot, is perfectly shaped and positioned so that the ecliptic glides up above the left-hand slope.  I have used this location several times over the last month or so.

When we arrive and take a look, I realise to my embarrassment that the ecliptic has moved south since my last excursion, and is now behind the hill.  Oops!  Stuart politely mutters something about “a mistake anyone could make” as we jump back in the car and head for the next best situation, a small car park about a mile further north.  Unfortunately this car park is on the western side of the main road, so by looking east we will have to put up with the headlights from any pre-dawn traffic.

There is a bank of cloud on the eastern horizon, but it looks to be quite mobile.  Rule number two kicks in – always set up the mount and point the camera in the right direction.  If conditions improve, there might not be time to set up later.  My routine is sufficiently well practised that I can unload the mount from the back of the car and be polar aligned well enough for five-minute exposures at 300mm focal length in just a few minutes.  As always, I use the tripod unextended for stability, which means kneeling down to squint up through the polarscope while holding a small red torch to illuminate the reticle.  In a couple of minutes, Polaris is sitting nicely in the hole and I can clamp the camera to the mount.

So where’s ISON then?  I have memorised this grab from the star chart:

0030 star chart

That’s my camera frame on Porrima, in the constellation of Virgo, set at 4.5 x 3.0 degrees for the 300mm lens.  If I place Porrima in the top right corner of the frame, then slide exactly one frame down the declination axis, ISON will be in the bottom left corner.  So where’s Porrima?  Here’s the first test shot:

0040 Porrima

Porrima top right, then slide one frame down and…

0050 Where?

Cloud.  My eye is drawn to the smudge dead centre.  I now know this to be elliptical galaxy NGC 4697, but in my mind ISON will look like a smudge, and there’s a smudge dead centre.  I start to doubt my calculation and my preparation to such an extent that I miss the comet lurking behind the cloud at bottom left – exactly where it should be.

Back to Porrima, slide down the Dec axis again, that didn’t feel right, do it again, nudge it a little bit further (why did I do that?), wait a moment for the clouds to move, and grab another test shot.  All this while chatting with Stuart about clouds, traffic, whether our luck will change, whether it was worth it anyway, and suddenly…

0060 First sight

What on Earth is THAT???  I stop chatting while my brain struggles to reorganise all my expectations in the light of this capture.  It takes several seconds for the realisation to hit home – on all previous occasions ISON has been invisible in the viewfinder, invisible in binoculars, invisible even in small telescopes.  The best so far has been a faint smear in the camera frame, gathered at high ISO and long exposure.  I let out a long whispering sigh of “Ooooooooohhhhhh Gotcha!” and walk the few steps in silent anticipation to show Stuart the iPad image.  What the …..? Take a look at that, my friend, we’ve got ourselves a comet.  Suddenly we are like excited schoolboys, chuckling, giggling, I even dance a little soft shoe shuffle in celebration.  Now we start shouting at the clouds, there must be a gap coming soon?  I hurry to realign the camera very slightly and catch ISON mid frame…

0070 C:2012_S1_20131115_0511

Dead centre.  Perfect.  Only the one frame, then the clouds fill the gap.  For a moment I rejoice in my good fortune to be in the right place, at the right time, camera mounted and pointing in the right direction, mount aligned well enough for this 30 second exposure (yes, this version has been calibrated with dark and flat frames in PixInsight, and histogram stretched to improve contrast and minimise the urban glow on the clouds, but it’s still a single frame).  Then I remind myself it’s not good fortune, is it?  It’s thinking, planning, preparing and practising.  It’s taking notes of every previous comet shot and thinking how the camera, lens and exposure settings influenced the final picture.  Let’s not forget all the nights of going out and coming home disappointed.  It’s setting that alarm clock again and actually getting up, loading up, going out, setting up, being ready, waiting for the moment, and pressing the shutter.  Yes, pressing the shutter!  I hadn’t even set up the remote trigger when this gap appeared in the cloud.  This one, I took by hand.

There must have been hundreds of photos taken of ISON around the world that night, and many more in the weeks surrounding perihelion.  Some of these have revealed exquisite detail in this visitor to our skies, not to mention the contribution they make to scientific data gathering.  Anyone stumbling upon this photo in that context, will probably give it no more than a few seconds then click on by.  It’s really not that good, but… it’s mine.  I took it with my trusty Nikon and an old 300mm lens.  I can even see some detail in the tail.  All those nights of practice and rehearsal chasing PANSTARRS paid off.  After ISON had its outburst on 14 November, we were mostly clouded over.  Then the full Moon filled the night sky with light, and a few days later, ISON had its fateful rendezvous with the Sun.  This particular photo opportunity will never come round again.  From where I live, this might have been the one gap in the clouds that allowed one good shot of ISON between outburst and perihelion.  One chance, one shot, and I got it.

PS. More practice with PixInsight and stacking the other frames I took that morning, has culminated in this version, which I don’t expect to improve.  The embedded credit was added, if I might be permitted a name-dropping little boast, at NASA’s request so that they could circulate it in their outreach work.  That’s the cherry on the icing on the cake.

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Lovejoy and ISON under clear sky

Only nine days from perihelion, ISON is lower and lower on the eastern horizon.  On Monday night (Tuesday morning, of course) I set the alarm for 3.30 and went out to chase it down at a new location, about a mile south of Killington Reservoir, east of Kendal.

It turned out to be a perfect location for looking east, with almost no urban glow on the photos.

Comet C/2012 S1 (ISON) 300mm f/5.6, ISO 400 150 seconds. 5 frames of 30 seconds.

Comet C/2012 S1 (ISON)
300mm f/5.6, ISO 400 150 seconds.
5 frames of 30 seconds.

It is almost impossible to process out the combination of moonlight and early twilight, while retaining the detail in ISON’s tail.  The angular separation of ISON from Spica (top right corner) is about 4 degrees, and others have photographed ISON with a tail in the region of 6 degrees.

Comet C/2012 S1 (ISON) 300mm f/5.6, ISO 400 420 seconds. 7 frames of 60 seconds.

Comet C/2012 S1 (ISON)
300mm f/5.6, ISO 400 420 seconds.
7 frames of 60 seconds.

A little more tail detail comes out from this stack of 60-second frames.  I am using ISO 400 to avoid completely burning out the centre of the comet.

Comet C/2013 R1 (Lovejoy) 300mm f/5.6, ISO 400 180 seconds. 12 frames of 15 seconds.

Comet C/2013 R1 (Lovejoy)
300mm f/5.6, ISO 400 180 seconds.
12 frames of 15 seconds.

Well above the horizon, and unaffected by the twilight, is Comet Lovejoy.  This was a particularly pleasing result, given the bright moonlight.