Peter Oshkai photography

The Wizard Nebula (NGC 7380) is considered a challenging photo target, because it is very dim. It’s impossible to see visually, and even photographically it typically requires hours of exposure time to bring out the details. I was lucky to have about 3.5 hours of cloudless skies to take this shot a couple of nights ago. The dual-narrowband (Ha + OIII) filter is tremendously helpful in cutting through light pollution. 

NGC 7380 is actually an open cluster of very young stars in the constellation Cepheus that formed about 5 million years ago – practically a moment ago in cosmic terms.  The nebula itself (S 142) is a cloud of ionized gas approximately 110 light-years long. It took 7000 years for its light to reach my yard in Victoria, BC.

The North America Nebula (NGC 7000) and the Pelican Nebula (IC 5070) in the Swan (Cygnus) constellation barely fit together in the field of view of my full-frame camera on a 478mm-long telescope. The North America nebula, named because it resembles the shape of the continent, is more than four time the size of the full moon! Its most famous feature, the Cygnus Wall lies where the Mexican West Coast would be on the map.

The Pelican Nebula sits just off the “East Coast” of the North America and is separated from it by the dark cloud of dust.

Despite the large size, these emission nebulae are very faint, so I was glad to have about 3.5 hours last night without clouds or moonlight to collect their light, which travelled for 2,600 years before reaching Victoria, BC.

This globular cluster is located in the torso of the Hercules constellation, about third of the way between Vega and Arcturus. It is close to my heart too, because it was the first Messier object that I saw in a telescope, and it’s beauty attracted me to astrophotography many years ago.

M13 is 145 light-years in diameter and contains over 500,000 stars. It is more than a hundred times more densely packed with stars than the neighbourhood of our Sun. The stars are so close that their collisions occasionally produce new stars.

Fun fact: In 1974, a coded Arecibo message about the human race was transmitted towards M13 to potentially contact extraterrestrial civilizations. Ironically, when the radio waves arrive there, in about 22,000 light-years, the cluster will likely have moved to a different position.

In the meantime, I was able to catch some of its photons flying the other way in my yard in Victoria.

Even though it’s a galaxy-viewing season, I wanted to shoot a nebula for a change. This is my take on the Rosette Nebula (Caldwell 49) – a giant star-forming complex in the Monoceros constellation of our home Milky Way Galaxy. It is 130 light-years in diameter and located 5,200 light-years away from us. In the centre is an open star cluster NGC 2244, the young stars of which create massive shock-heated winds that blow the ionized bubble in the centre and excite the nebula’s gas to emit the red light.

The Rosette sets early this time of the year, so I shot it over three evenings to collect enough photons. The image nearly fills the frame of my camera, so there is plenty of resolution. Zoom in – it’s mesmerizing!

For my second photoshoot after deciding to give a serious effort to come back to astrophotography I chose another famous target – The Leo Triplet. I caught it during a short break in the clouds. The members of this group of galaxies are M65 (right top in the image above), M66 (right bottom) and NGC 3628 (the Hamburger Galaxy, bottom left). They are about 35 million light years away from us.

This shoot was done on a tracking mount, but without guiding, so I used 41 sub-exposures of 25 seconds each (so-called light frames). The relatively short exposure times were needed to avoid the trailing of the stars. My polar alignment was pretty good, though, so the tracking worked well. I used a stock (unmodified) Sony a7r mark IV camera on an 81-mm (478 mm focal length) refractor telescope with the aperture of f/5.6. The ISO was set to 800, following an example I saw online. For calibration, I took 25 dark frames (same exposure length as the light frames, with the lens cap on) and 25 flat frames (2-sec exposures with the same ISO and focus as the light frames, uniformly illuminated by a tracing LED light panel through a couple of T-shirts).

The image below is a wide field, which I cropped in to get the top image. 

Generally, I think not much would be possible in this area of amateur astrophotography if people would not share they experiences in online forums and in their blogs. So here is a bit of what I learned in this photoshoot: for shooting the flat calibration frames, while it is common knowledge to select the exposure in such a way that the histogram peak of the resulting images is roughly in the middle or slightly towards the left (dark) side of the light intensity range, it is also crucial to make sure that the shutter speed is long enough to average out the banding caused by the LED light source. Since the ISO is fixed (it needs to match the light frames)

I was quite pleased with this image after stacking the images in the Pixinsight software. I did make a few beginner mistakes, though. The main one is that I decided to go for a second target during the same night instead of collecting more photons of these galaxies. Since then, I have aquired some new tools and techniques, both for the image acquisition and the processing, so I am looking forward to revisiting the Leo Triplet when the skies clear up. Waiting for a cloudless, moonless night is an exercise in forced patience – a benefit of the astrophotography hobby, I suppose.

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