Chris Howard's Blog, page 63
June 2, 2018
The setup for tonight, William Optics ZenithStar 61 with the...
The setup for tonight, William Optics ZenithStar 61 with the Atik Cameras 414EX. I’m going to do some narrowband imaging because the moon is bright. My main target will be the Crescent Nebula (NGC 6888) to get some follow-up O3 frames. More here: http://SaltwaterWitch.com/astronomy
May 31, 2018
May 30, 2018
Narrowband imaging on the cheap?It’s tempting to say...
Narrowband imaging on the cheap?
It’s tempting to say “here’s what you can expect from a $129 Hydrogen-alpha filter”, but it’s never as simple as that, is it? Perspectives and opinions vary, but I consider this a pretty good narrowband shot of the Crescent Nebula (NGC 6888), with some great contrast–the Crescent structure itself stands out, and I still managed to bring in a lot of the surrounding dust and clouds of ionized hydrogen. I used an Astronomik 1.25" 12nm Ha filter, an Atik 414EX mono CCD, iOptron CEM25P EQ mount, and I took 4 x 1200 second subs + 15 dark frames, all stacked in DSS. I shot these frames from my backyard, on a clear night with good seeing (Bortle 4, SQM: 20.62 mag/arc sec² according to https://www.lightpollutionmap.info). I’ve never shot deep space objects with 6, 5, or 3nm bandpass filters, but a 2" Baader 7nm used to be my primary Hydrogen-alpha filter–and I loved it. When I started out in astrophotography I was thinking long-term and went with 2" filters for everything–and it cost me a bunch. A couple years ago I switched to 1.25" filters, both for cost and pairing with the smaller Atik 414EX sensor–2" wasn’t necessary. It also allowed me to get the Atik EFW2 with the 9-position filter wheel, so I can run with LRGB, Clear, Ha, OIII, SII, near-IR all in one neat motorized package. Because I was looking to save to money I went with a cheap Ha filter–the Astronomik 12nm H-alpha runs around $130 USD. Very inexpensive, when compared to the $300 2" Baader I used to use regularly, and nowhere near the $900+ Astrodon 3nm 2" filter. I’m sure the Astrodon kicks ass–they’re one of the premier filter manufacturers. But do you need a $900 filter to shoot narrowband? If you have fairly dark skies in your neighborhood (or within driving distance), I would say absolutely not. Will it make things easier when it comes to increasing SNR in light polluted skies? Absolutely. Will it make things easier when it comes to increasing contrast and pulling in those fainter wisps of dust and hydrogen? Probably. But I wouldn’t hold off on narrowband imaging just because you can’t afford the best. There are just too many cool targets in the night sky that you’re not going to pick up with RGB. And that’s one of the advantages of our hobby. You can shoot forty subs tonight, stack, process, and post them, and then come back tomorrow, next week, or next year and reshoot the same target with a different camera, scope, or better filters. Some targets never get old, and if they do there are mysterious absorption and integrated flux nebulae and even crazier things in the night to pursue. There are always interesting new wonders below the horizon–or above depending on which hemisphere you spend most of your time. http://SaltwaterWitch.com/astronomy
May 28, 2018
Today’s painting: a freighter heads into deep space, about...
Today’s painting: a freighter heads into deep space, about five hours in ArtRage5 and PSCC. More of my art: http://SaltwaterWitch.com
A few more shots from last Tuesday’s astro session: (top...
A few more shots from last Tuesday’s astro session: (top left) North America Nebula (NGC 7000) 50 stacked frames from the ZWO071MC camera. (top right) The Eagle Nebula, Messier 16, sometimes called Star Queen is a diffuse nebula in the constellation Serpens. M16 was only 22° above the horizon to the southeast when I was taking these subs, low enough to have the atmosphere and some light pollution from Hampton affect the result. Even so, I’m here in New Hampshire at 43° latitude, and I’ll take any chance I can get to shoot the Eagle Nebula. (bottom right) Swan Nebula (M17, Checkmark Nebula, Omega Nebula, NGC 6618) is another H II region in the constellation Sagittarius. Another one of the Globular Cluster in the constellation Hercules (M13).
May 27, 2018
Havelock Vetinari, the Patrician of Ankh-Morpork. Lord Vetinari...
Havelock Vetinari, the Patrician of Ankh-Morpork. Lord Vetinari is the definitive benevolent dictator. He’s an honored graduate of the Guild of Assassins, rebel fighter against Homicidal Lord Winder, killer of tyrants, and friend (possibly more) of the vampire Lady Margolotta of Überwald. Pratchett kept his cards close with Vetinari, and all of us–readers and Ankh-Morpork citizens alike–remain in the dark about most of the details of Vetinari’s life, habits, vulnerabilities. This may be one of the reasons Night Watch is one of my favorite Pratchett books–because we get to see Havelock when he’s a young man, at school, learning the guild craft of assassination and camouflage. We get to see a side of the future patrician that we’ll never see again, but after one read of Night Watch the character hints and pieces of his nature you pick up will follow you and fill in the shadows of every scene with Vetinari in every other book. He’s one my favorite characters, not just from Terry Pratchett’s Discworld, but from _any_ book.
More of my favorite Ankh-Morpork characters:
Angua
http://the0phrastus.tumblr.com/post/172602193231/sergeant-angua-of-the-ankh-morpork-city-watch
Detritus
http://the0phrastus.tumblr.com/post/172699455011/sergeant-detritus-of-the-ankh-morpork-city-watch
Cheery Littlebottom
http://the0phrastus.tumblr.com/post/173468117621/im-continuing-the-painting-series-of-my-favorite
Sam Vimes
http://the0phrastus.tumblr.com/post/173125339491/we-first-meet-sam-vimes-as-a-miserable-night-watch
Carrot Ironfoundersson
http://the0phrastus.tumblr.com/post/174287491141/im-still-painting-my-way-through-some-of-my-terry
May 26, 2018
I’m still painting my way through some of my Terry Pratchett...
I’m still painting my way through some of my Terry Pratchett character favorites: Carrot Ironfoundersson, also known as Kzad-bhat, which roughly translated, means “Head Banger”, is a human adopted by dwarves. He was raised in a mine near Copperhead, probably banging his head a lot, but ends up making the journey to the great city Ankh Morpork in order to join the Watch. Even though Commander Vimes and a few others in the Watch possess a pretty strict and streetwise morality, Carrot enters the city fully prepared, with a completely memorized ancient edition of The Laws and Ordinances of the Cities Ankh and Morpork. And he’s ready to use it to ensure the safety of his fellow citizens. What makes Carrot unique–and so different from anyone else wielding a book of laws–is his ability to interpret a law and balance that against an examination of his own perspective and the motives of others to resolve the problems they face. It’s this simple wisdom that usually carries him through the fray–that, and his joyful spirit. Carrot approaches his position in the Watch with such cheer, generosity, and honesty that everyone around him has no choice but to get swept up in the sheer force of his upbeat will. His genuineness and optimism–some might say _extreme_ optimism–balances out and sometimes runs roughshod over the cynicism and distrust that’s the baseline sentiment of the Ankh Morpoork City Watch. His fellow watchmen often stand back and just stare in awe as Carrot singlehandedly diffuses the tension between armed angry mobs of trolls and dwarves, as he cheerfully explains the criminal code–or the tax code–to hardened thieves, murderers, and tax-evaders. He’s not flawless and carries some of the prejudices of his upbringing with him, but he’s honest enough to see what’s right, and what he has to change in himself in order to make his adopted city a better place for everyone. We first meet Carrot in the book Guards! Guards!, where his idealism and hard work make such an impression on the Watch that he’s promoted quickly. In one of Terry Pratchett’s later books, Snuff, Carrot becomes Acting Commander of the Watch, while Vimes is forced to take a vacation.
More of my favorites in the Watch:
Angua
http://the0phrastus.tumblr.com/post/172602193231/sergeant-angua-of-the-ankh-morpork-city-watch
Detritus
http://the0phrastus.tumblr.com/post/172699455011/sergeant-detritus-of-the-ankh-morpork-city-watch
Cheery Littlebottom
http://the0phrastus.tumblr.com/post/173468117621/im-continuing-the-painting-series-of-my-favorite
Sam Vimes
http://the0phrastus.tumblr.com/post/173125339491/we-first-meet-sam-vimes-as-a-miserable-night-watch
May 25, 2018
The Great (and wonderful) Globular Cluster in the constellation...
The Great (and wonderful) Globular Cluster in the constellation Hercules (M13) with a hint of the spiral galaxy NGC 6207 at the top. Last night was my first night out with the William Optics ZenithStar 61, and as I expected, it’s just a brilliant little refractor. Paired with the ZWO ASI071MC cooled camera and the WO 0.8x Flat/Reducer F6-A, you get a spectacular 4.7° × 3.1° field of view–that’s a big chunk of the sky. If you’re looking for a pretty fast widefield apochromatic, this is it. It’s not the best choice for the Hercules cluster, but I was just slewing all over the sky, waiting for the North America Nebula to get above 30 degrees.
