Andromeda's core
Something to think about on a Friday night: the Andromeda Galaxy (M31) is moving toward our galaxy, the Milky Way, at a little over 400,000 kilometers per hour, and the supermassive black hole at the center of Andromeda is 100 million times the mass of our sun. Note: at that speed Andromeda will still take 4 billion years to get here. I figure we'll be beyond Kardashev 3 in the next 3 - 4 million years, and we'll simply move our galaxy out of the way.
Posted July 17, 2020
Early moon rise with Venus and Aldebaran
Up early this morning and out in the backyard to get some shots of the moon and Venus--and Aldebaran! This is one shot with the Nikon D750 and the 70-300mm - focal length 95mm, 1.6 second exp at f/10, ISO 1600
Posted July 17, 2020
Gulf of Mexico in NGC 7000
Here's another crop from the stacked 41 x 240 second subs of the North America Nebula (NGC 7000) in Ha, this time the "Gulf of Mexico" region, with some fantastic dark nebulae. This is a slightly narrower field of view than the Cygnus Wall, and so we're only looking at about 100 trillion miles from one side to the other. When you read that atomic hydrogen, the lightest element, makes up 75% of the baryonic mass of the universe, this is what they're talking about. Almost everything you see in this frame, dark and light clouds--even the stars, is hydrogen in various forms.
Posted July 12, 2020
Cygnus Wall in NGC 7000
I'm going to retake the last set of hydrogen-alpha frames for NGC7000 because the stars are a bit wonky, but the clouds of ionized hydrogen and massive structures of dark interstellar dust still look beautiful in this stacked set of 41 exposures. Here's a crop of the "Cygnus Wall" in NGC 7000. In this field of view, you're looking at about 118 trillion miles of dense clouds of interstellar ionized hydrogen. NGC 7000 is about 1600 lightyears aways, and the "Cygnus Wall" is about 20 light years long--about 118 trillion miles.
Posted July 12, 2020
IC 1396 in Narrowband
The IC 1396 region: IC 1396A is the Elephant's Trunk Nebula (center) surrounded by knots and bands of dark interstellar dust. Barnard 163 (B163) is the dark nebula center top. When it comes to narrowband imaging (Ha, OIII, SII) the constellation Cepheus is one of my favorites. I could spend a month just on IC 1396, the whole region, capturing the dozens of dark nebulae and the Elephant's Trunk at different focal lengths, but Cepheus also has the Iris Nebula and a bunch of other cool nebulae, including Barnard Catalogue objects like B169, as well as LDN 1272 and the wisps of hydrogen clouds that make up Sh2-134. All worthy targets for your telescope and camera. Notes: 48 x 240 second subs of Ha and OIII, William Optics GT81 Apo refractor, ZWO ASI1600MM-Pro mono camera, Astronomik filters, iOptron CEM25P mount.
Posted July 10, 2020
Pacman Nebula (NGC 281)
Pacman Nebula (NGC 281) in the Constellation Cassiopeia is an emission nebula about 9200 lightyears away from us, part of an HII region in the Perseus Arm of our galaxy. Notes: Shot from my backyard with the William Optics GT81 Apo refractor, iOptron CEM25P mount, Astronomik narrowband filters.
Posted July 3, 2020
Narrowband imaging run with the GT81 and Sky-Watcher EQ6-R Pro
Have you ever been framing in SGP or browsing Telescopius for Messier 16, the Eagle Nebula or M17, the Swan Nebula, and looked over and saw that totally creepy arrow-shaped dark nebula--and thought, I want to take pics of that? Well, that's B312. Let's get started!
Okay, I'm back with the fully operational* William Optics GT81 and Moonlite focuser setup, with the flat field and focal reducer spacing much closer to spectacular than it was yesterday, and my first astro-imaging target for the night is B312 in the Constellation Scutum. That's Barnard 312 from the classic Barnard Catalogue of Dark Markings in the Sky. Yes, that is the actual full title, although it's usually shortened to "The Barnard Catalogue". I have had my eye on B312 for a while. It's this beautiful arrow shape of interstellar dust twisting through the dense starfield where Scutum edges up against Serpens and Sagittarius, just out from the Milky Way core. B312 is thought to be made up of rapidly condensing clouds of molecular hydrogen (H2) that will in the near future become a star-forming region. Cool. I'm not holding my breath. How near into the future is relative, but you'll be on the right track if you think in terms of galactic time scales. Here in New Hampshire time moves a little slower and B312 is very low in the south, never rising above 32 degrees or so. I can only capture it east of the meridian, so I don't have a lot of time before the earth rotates it behind trees and transmission lines. And guiding that far south, just above the horizon, is always trouble, doesn't matter which mount I use. Right now in PHD2, I'm happy with a 1.25 arcsecond total RMS. I will just have to enjoy the far south nebula time while I can, and deal with it in post, as they say. Notes: 36 x 240-second Ha sub-exposures stacked in DeepSkyStacker, processed in PSCC2020.
* the scope was fine, but I had dismantled everything and returned it to it's default position--original focuser, with the 90mm tube rings and vixen dovetail bar. By "fully operational" I mean I went back to the config with the Moonlite focuser.
Much better guiding and clearer skies heading toward the zenith with the North America Nebula. Here's a processed stack of 41 x 4-minute hydrogen-alpha subs of the "Cygnus Wall" in NGC7000. A lot of signal, not a lot of noise, and those gradients of ionized interstellar hydrogen are "like buttah" they're so smooth. Still not happy with the stars, but have to wait for the next clear night to correct--could be the OAG. Check out the full image: https://SaltwaterWitch.com/img/NGC7000_Ha_ChrisHoward_20200619_04.jpg That's the full downscaled JPG at 1600 x 1213, not the full sized version of this image, which has a resolution of 14000 x 10618 px. Imaging notes: William Optics GT81 Apochromatic refractor--an amazing piece of hardware, Astronomik 6-nanometer hydrogen-alpha filter, ZWO ASI1600MM-Pro monochrome camera, QHY 5iii178 guide camera, Sky-Watcher EQ6-R Pro Mount.
These two images of B312 and NGC7000 are uncropped, and you can see the darker edges where I dithered every three frames. I almost always use drizzle when processing--"drizzle" doubles or triples the resolution of an image using variable-pixel linear reconstruction that preserves photometry and detail, and especially works well if you're undersampling. I'm a bit under with 2.05 arcseconds/pixel with the ASI1600 camera and William Optics GT81, but I still use drizzle in DeepSkyStacker. The drizzle algorithm was originally developed for the Hubble Deep Field observation data, but it's now pretty common in astro-imaging applications.
A couple shots from the NGC7000 sequence. I'm really happy with the tracking and guiding on the Sky-Watcher. These are pretty decent numbers for the mount's location--on the shifting timbers of our back deck.
And the video that goes along with this post--check out my Youtube channel for more videos:
Posted June 19, 2020
Playing with field flatteners and sensor distance
I'm still running some tests with the new mount as well as clearing up distance issues I had with my narrowband imaging train and the William Optics Flat 6AII field flattener/focal reducer. Everything has to be precisely positioned in order to produce a distortion-free field, round stars, all that stuff. I ended up going back to the stock focuser for the GT81 just to simplify things. And I think it was fairly successful. And the Sky-Watcher EQ6-R Pro continues to make the job easy!
I really like the Framing & Mosaic Wizard in Sequence Generator Pro, and still think this is one of SGP's best features--if only it could function without a net (offline). For one of my test runs I called up IC 1318, the Sadr Region in Cygnus, which contains the Butterfly Nebula, Crescent Nebula (NGC 6888, Caldwell 27), and many beautiful dark nebulae. Using the framing wizard at 6 degrees I centered the sequence on these twists of hydrogen clouds out at the edge--just for something different. My intent was to shoot 50 x 240-second subs, about 3.3 hours of hydrogen-alpha data, but I discovered--too late--that I had a power problem with the dew control gear and the objective on the GT81 started clouding over about an hour and a half into things. I still managed to process something out of the stack, but a better shot will have to wait for another night.
I also took 30 subs of Sh2-54, GUM 84 and 85, LBN 72, that bright emission nebula in the Constellation Serpens. The star cluster NGC 6604 is to the right of it.
And last, just on whim because I had another hour of darkness left in the night, I moved up to IC1396 again, centering on the Elephant Trunk Nebula. I didn't get enough Ha data for a cleaner image, and I had lost some focus by that point too, HFR numbers were climbing over 3 pixels from about 2.25.
We have another fairly clear night tonight, and I'll be returning the William Optics GT 81 to it's modified state, Moonlite Focuser. I may also test things out with NINA again.
