Shooting the Heart Nebula


Testing the Nikon D810a

Last night I shot into the autumn Milky Way at the Heart Nebula.

I’m currently just finishing off a month of testing the new Nikon D810a camera, a special high-end DSLR aimed specifically at astrophotographers.

I’ll post a more thorough set of test shots and comparisons in a future blog, but for now here are some shots from the last couple of nights.

Above is the setup I used to shoot the image below, shot in the act of taking the image below!

The Nikon is at the focus of my much-loved TMB 92mm refractor, riding on the Astro-Physics Mach One mount. The mount is being “auto-guided” by the wonderful “just-press-one-button” SG-4 auto-guider from Santa Barbara Instruments. The scope is working at a fast f/4.4 with the help of a field flattener/reducer from Borg/AstroHutech.

I shot a set of 15 five-minute exposures at ISO 1600 and stacked, aligned and averaged them (using mean stack mode) in Photoshop. I explain the process in my workshops, but there’s also a Ten Steps page at my website with my deep-sky workflow outlined.

IC 1805 Heart Nebula (92mm D810a)
The Heart Nebula, IC 1805, in Cassiopeia, with nebula NGC 896 at upper right and star cluster NGC 1027 at left of centre. This is a stack of 15 x 5-minute exposures with the Nikon D810a as part of testing, at ISO 1600, and with the TMB 92mm apo refractor at f/4.4 with the Borg 0.85x field flattener. Taken from home Nov 29, 2015.

The main advantage of Nikon’s special “a” version of the D810 is its extended red sensitivity for a capturing just such objects in the Milky Way, nebulas which shine primarily in the deep red “H-alpha” wavelength emitted by hydrogen.

It works very well! And the D810a’s 36 megapixels really do resolve better detail, something you appreciate in wide-angle shots like this one, below, of the autumn Milky Way.

It’s taken with the equally superb 14-24mm f/2.8 Nikkor zoom lens. Normally, you would never use a zoom lens for such a demanding subject as stars, but the 14-24mm is stunning, matching or beating the performance of many “prime” lenses.

The Autumn Milky Way (Perseus to Cygnus)
The Milky Way from Perseus, at left, to Cygnus, at right, with Cassiopeia (the “W”) and Cepheus at centre. Dotted along the Milky Way are various red H-alpha regions of glowing hydrogen. The Andromeda Galaxy, M31, is at botton. The Double Cluster star cluster is left of centre. Deneb is the bright star at far right, while Mirfak, the brightest star in Perseus, is at far left. The Funnel Nebula, aka LeGentil 3, is the darkest dark nebula left of Deneb. This is a stack of 4 x 1-minute exposures at f/2.8 with the Nikkor 14-24mm lens wide open, and at 24mm, and with the Nikon D810a red-sensitive DSLR, at ISO 1600. Shot from home, with the camera on the iOptron Sky-Tracker.

The D810a’s extended red end helps reveal the nebulas along the Milky Way. The Heart Nebula, captured in the close-up at top, is just left of centre here, left of the “W” forming Cassiopeia.

The Nikon D810a is a superb camera, with low noise, high-resolution, and features of value to astrophotographers. Kudos to Nikon for serving our market!

– Alan, November 30, 2015 / © 2015 Alan Dyer / www.amazingsky.com

 

Here Comes the Sun!


I can count on one hand how many shots of the Sun I’ve taken in the last decade that weren’t at an eclipse, or a sunrise/sunset. I just don’t do much solar shooting. But today I had to resurrect some old gear to get this shot. The Sun was putting on a fabulous show this afternoon (Sunday, June 5, 2011) with an army of huge prominences rimming the edge of the Sun. Very impressive. And looking very HOT!

After 2 to 3 years of record low activity, the Sun is picking up, returning to its normal self, with sunspots and prominences a daily occurrence. But these were especially dramatic. Each of these prominence “flames: towers tens of thousands of kilometre above the surface of the Sun. The Earth would be a dot next to one of them.

To get this shot, I created a masked composite in Photoshop of two exposures, a short 1/13s second shot to record the disk detail, and a long 1/2 second shot to record the fainter limb prominences. For a telescope I used my little Coronado PST H-alpha scope, a special scope just for solar viewing that filters out all but a narrow wavelength of red light, allowing the prominences to be seen.

Trouble is, my DSLR cameras won’t reach focus on the Coronado scope. So I dusted off the little 2003 vintage Sony DSC-V1 point and shoot camera and a Scopetronix 40mm eyepiece and “afocal” adapter, so the camera was screwed onto and looking into the eyepiece which was then inserted into the scope. I hadn’t used an afocal setup like that since the Venus transit in 2004.

It was tough to focus the stack, so focus was a bit of a guess — it was helped here with a liberal application of Photoshop’s Smart Sharpen filter! In all, it is a crude system but in a pinch it does work. Maybe I’ll have to get better gear just to take solar shots. With the Sun becoming more active, there certainly will be lots more to shoot.

— Alan, June 5, 2011 / Image © 2011 Alan Dyer