M81 and M82

I have become a bit of a comet addict in my astrophotography, and with so few opportunities to take advantage of clear skies in Cumbria, have neglected my other targets in favour of these elusive and challenging subjects.  Yesterday evening I determined to spend time away from comets and catch myself a couple of galaxies.

M81 and M82, 12 million light years away in Ursa Major, were at good altitude mid-evening, rotating toward the zenith.   The birthday fairy brought me a QHY5L-II CCD camera last month, which I can use for guiding my Altair Wave 115/805 on the Skywatcher AZ-EQ6 mount.  Ten-minute subframes was my choice of exposure for the session.  I suspect these might be achievable unguided, now that the mount is sorted, but I wanted to test the setup and familiarise myself with all that it requires.  Humidity was high and the sky was lighter than I remembered at Old Hutton church carpark, so I kept the Nikon D90 at a low ISO of 400 for the long exposures.

Focusing was manual using a Bahtinov mask.  Five frames came out well, one jumped during the guiding and was discarded.   The full PixInsight processing sequence from Nikon RAW files was:

Convert to FITS

Calibrate (not this time though, I took neither dark nor flat frames!)

Debayer

Register (align)

Stack to average, using percentile rejection

Dynamic Background Extraction (eliminate the skyglow)

Colour Calibration (no more green-tinted pictures!)

Histogram Stretch

Saturation and background darkening using Curves

Noise Reduction

High Dynamic Range Multiscale Transformation (detail in the spiral arms)

Crop and convert to JPEG.

 

This is the full size JPEG after processing.  I should get out more!

M82 and M81
Nikon D90 on Altair Wave 115/805 (f/7), ISO 400
50 minutes: 5 frames of 10 minutes each.

Here’s another version with some sharpening applied too.  I separated the luminance data from the colour data, sharpened the luminance and blurred the colour before recombining.  It’s a mixed result, definitely bringing out more detail but also I think it gives a slightly artificial edge to the galaxy.  More practice needed…

M82 and M81
Nikon D90 on Altair Wave 115/805 (f/7), ISO 400
50 minutes: 5 frames of 10 minutes each.

 

The wait is over…

2014 has been the year of the kit upgrade.  It has been in my mind for some time, and I’ve finally taken the plunge.

My basic setup is now an Altair Wave 115mm ED triplet refractor, mounted on a Skywatcher AZ EQ6-GT.  The telescope adapter means I can still attach my Nikon D90, so I’ll be sticking to that for the time being.  I will write up my experiences of the kit once I’ve got the hang of it – there’s so much to learn about using a telescope as an 805mm f/7 telephoto lens, and the computerised mount is really something special.  The whole lot weighs a ton, so it’s most definitely an out-of-the-back-of-the-car activity.

First night, 17 April, in a brief opportunity in my moderately light polluted back yard, I could put the kit through its paces.  M81 and M82 had been a recent target for the supernova, so I pointed there for comparison and took just four frames of a minute each.  Stacked and processed in PixInsight, this uncropped photo shows exactly what’s in the viewfinder.

17 April 2014: Galaxies M81 and M82
Altair Wave 115/805, ISO 800, 4 minutes.
4 frames of 1 minute.

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):

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):

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!