Salvatore Iovene / Mostly astrophotography and code

Here are seven an a half hours, split in fifteen 30-minute subs, on the Wizard Nebula, aka NGC7380, aka Sh2-142.

NGC 7380 is a typical starforming region in the direction of an outer spiral arm of our galaxy (around 7,000 light years distant). This field contains many young energetic stars that make the natal gas that surround them glow an intense pink/red. The majority of stars for this newly formed group are out of the field to the upper left (right, in my image). Their winds and radiation sculpt clouds of gas and dust into the mountainous ridges seen here. The darkest parts of this image are foreground clouds of dust thick enough to extinct the light beyond them

(Quoted from http://www.noao.edu/outreach/aop/observers/n7380.html)

Only 100 minutes went into the capturing of this NGC7000, split into five 20-minute subs. Obviously this is an area extremely rich of hydrogen, as the amount of signal is incredible for my tiny 80mm refractor.

NGC7000, aka The North America nebula (obvious nickname), is a very large nebula, actually covering an area four times as large as the full moon. The area I imaged is called “Cygnus’s Wall”.

Very interesting, the shape you see is not the result of a particularly shaped cloud of gas, but it’s determined by the fact that between us and NGC7000 lie some bands of interstellar dark dust.

The distance of the nebula is not known, nor is the star that lights it. Some sources indicate that the star might be Daneb; in that case, NGC7000 might be 1800 light-years away, and it’s absolute size would be about 100 light-year across.

This image is the result of a cooperation between me, a Dutch astrophotographer named Gustaaf Prins and an Irish astrophotographer named (waiting for clearance to disclose name.)

I acquired the OIII and SII data, $NAME acquired the Ha, and Gustaaf Prins acquired the RGB (for the stars.)

Data

• SII: 13x900” 12nm
• Ha: coming soon
• OIII: 7x1800” 12nm
• R: 9x300” bin2
• G: 9x300” bin2
• B: 9x300” bin2

Equipment used

• SII and OIII: Skywatcher ED80, Moravian G2-1600
• Ha: coming soon
• RGB: TS APO Triplet 90/600mm, Atik 383L+

About NGC6888

The Crescent Nebula (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light years away. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures.

Processing

The image was entirely processed in PixInsight 1.7.

Finally I had a chance to do the Iris nebula again, this time properly. The first time I tried, the Moon was full and the sky was still slightly glowing of sunlight, because the Sun wasn’t 18 degrees below yet.

This time I managed 13 subs of 600 seconds, plus one sub of 420 seconds.

The blue part of the nebula is now clearly visible, and it extends well beyond the core that I managed to image previously.

Even some of the dark nebulae around it hint their existence, although very subtly.

They’d need more aperture, longer exposure times, and, of course darker skies.

Speaking of which, the sky was particularly dark last night, and I estimated a visual limiting magnitude of 5. The absence of the snow helps!

Thanks to my friend Milosz, my M27 has been gifted with some twelve and a half hours of pretty good old h-alpha signal. I have here merged that data to my Red channel, and composed the image above with PixInsight.

Here’s thirty-five five-minute shots at the M92 globular cluster in Hercules.

Messier 92 is about 26,700 light-years away and one of the brightest globular clusters of the northern hemisphere. It’s often overlooked, though, because of its proximity to the more prominent M13.

This is the first image flatted with my new light box. You can’t tell because this is a crop, but the box worked well.

Right after imaging the Gallardd C/2009 P1 comet, I managed seven subs of five minutes each on the Dumbbell nebula, aka M27, a planetary nebula in Vulpecula. To be fair, M27 needs no introduction, being one of the most prominent planetary nebulae we can enjoy.

As usual, my image lacks a lot of signal in the red channel, because regular DSLR are, by default, pretty much blind in the red part of the spectrum.

M27 has the notable characteristic of featuring a central star that is the largest known white dwarf.

There it is. I have wanted to immortalize this comet since July, but it was too low for me. It finally arrived in Sagitta, but I missed the conjunction with M71 because it was overcast (no wonder), but luckily the two objects were still close enough the next day when it cleared up.

What you see above is the stack of fourteen frames, three minutes each. Of course the comet is moving and not the star, but I have aligned these images keeping the comet stationary.

In the next picture you can see the comet leaving a trail. It’s a larger field including the open cluster M71:

The Garradd C/2009 P1 comet was discovered, as the name implies, by Garradd in 2009 when its magnitude was 17.5.

This page contains a lot of information about the comet.

Messier 71, at the bottom of the picture, is a globular cluster in Sagitta. I’d like to quote an interesting parte from Wikipedia:

M71 was long thought (until the 1970s) to be a densely packed open cluster and was classified as such by leading astronomers in the field of star cluster research due to its lacking a dense central compression, and its stars having more “metals” than is usual for an ancient globular cluster; furthermore, it’s lacking the RR Lyrae “cluster” variable stars that are common in most globulars. However, modern photometric photometry has detected a short “horizontal branch” in the H-R diagram of M71, which is characteristic of a globular cluster. The shortness of the branch explains the lacking of the RR Lyrae variables and is due to the globular’s relatively young age of 9-10 billion years. The relative youth of this globular also explains the abundance of “metals” in its stars. Hence today, M71 is designated as a very loosely concentrated globular cluster, much like M68 in Hydra.

What is a flat field? It’s a picture of a uniformly lit surface, used to correct defects like vignetting, dust on the sensor, mirrors or lenses, and scratches anywhere in the optical train. Astrophotography is really about taking pictures of subjects that are so faint, you will need to stretch the histogram so much that even tiny defects will be able to ruin your image. Considering that you have spent between 4 and 10 hours, usually, just collecting data for the image, and then several hours post processing, taking the time to take good flat frames is the least you can do.

Considering that you usually adjust the focus between different sessions (different filters and/or different temperatures), and often rotate the CCD or DSLR camera to better frame your subject, flat fields must be acquired at every session. For this reason, it’s very important to have a comfortable way to absolve this task.

For a good part of last year, I have used an electro-luminescent foil. I regret to say that, even though the surface was lit in a very uniform fashion, just like advertised, the whole thing was pretty cheap looking. The electric connections were the bare minimum, the wires were thin, and the battery holder and switch looked and felt like a toy.

Needless to say, the thing eventually broke. Granted, it was mostly due to the extremely cold temperatures that made the plastic of the wires very rigid, and therefore prone to rupture. With perfect (dare I say maniacal) care, it wouldn’t have broken; but let’s not linger.

With the new season starting, I have decided to build my own flat field light box, grabbing bits and pieces of various designs I have found on the Internet.

My light box’s vital component is a set of two strips of white LEDs, with a color temperature of 6000K. They are connected serially to a 12v battery pack (made of eight 1.5v AA batteries) and a simple switch. Here you can see them lit:

And this is a section of the inside. You can’t really see the electronics, but there’s really not much to see:

The two foam core panels hide and protect the wiring and the connection, and only let the power connector and the switch out.

The two panels are connected with bolts and nuts, with some plastic separators to keep them at the right distance. On the other side, which would be the bottom of the box, you can see the switch and the power connector sticking out, and a small frame that prevents the switch from holding the weight of the box.

And here are all the components in a big family picture, before the assembly:

Notice how all the four sides have rails in place, that will allow me to slide in the plexiglass light diffusers. The two panels with the circles are the front panel (with the larger hole that lets the telescope dew shield in) and the stopper point, with the smaller hole that will prevent the telescope to slide in any farther.

Since taking the last picture, though, I have added a third rail for a third diffuser. I initially planned to use two, but, after some experimenting, it looked like I got a smoother surface with three. Here is the box, half assembled, showing the three diffusers and the panel that stops the telescope’s dew shield from sliding any farther (at the bottom):

I have used some super glue on the connecting parts, but that was far from enough, so I have used tape to hold the box together. It’s actually a lot more solid than it looks in the following picture:

Then, the box has gone through some rounds of aluminum foil, which will keep light infiltrations at bay:

Finally, the box has been completely wrapped into construction grade tape for structural support:

Here you can see the front of the box when it’s lit:

And at last, this is the multiplicative, scaled, non-normalized and non-calibrated, stretched winsorized sigma clipped average of ten flat frames produced by the light box on my ED80 refractor and Canon 450D:

I was waiting for the comet Garradd C/2009 P1 to rise behind my house, and the night hadn’t cast its darkness on my site yet. Well, by darkness I mean light pollution, but make what you want of it. Anyway, with the sky still blue I shot twenty images, three minutes each, to the most prominent globular cluster visible at my latitude.

The blob you see in the top left is nothing but three hundred thousands stars condensed in a mere 145 light years diameter.

Noticeably, the Arceibo message was directed to this cluster in 1974. I guess we won’t hear back for a while, given the estimated distance of twenty-five thousands light-years!

On the bottom-right of the image you can see the faint spiral galaxy NGC6207, in which a supernova was discovered in 2004. It’s forty-five million light-years away.