Tuesday, September 16, 2014

The Tulip Nebula (Sharpless 101)

The Tulip Nebula is an emission nebula in a distance of 6,000 light years from earth in the constellation Cygnus.
(click on image for full resolution)

The image consists of 130min Ha, 300min OIII and 250min SII.

The nebula gets excited by the young, energetic star HDE 227018 at the center of the nebula near the arc. HDE 227018 moves very fast through the nebula (almost certainly it was not created within the nebula). The arc is probably bow shock, indicating in which way HDE 227018 moves.

Another interesting object in the nebula is a star to the right of the nebula: Cygnus X-1. In 1964 during a rocket flight, it was identified as a very strong x-ray emitter. After more analysis, researchers identified it as a binary system where the second star is invisible. From the movement of the visible star, the mass of the invisible partner was determined to be between 20 and 35 solar masses. Since the largest possible mass of a neutron star can not exceed three solar masses, the compact object was suspected to be a black hole. In 1974, Stephen Hawking and Kip Thorne had a wager - with Stephen Hawking betting it is not a black hole. He conceded the bet in 1990 after additional observational data strengthened that case. And if Stephen Hawking concedes, there aren't any doubts left. And with that, Cygnus X-1 became one of the first confirmed black holes.

Tuesday, September 9, 2014

Using PinPoint for plate solving

A question that comes up a lot on the SequenceGenerator mailing list is what plate solving software to use. And some folks keep raving about PinPoint. With my large 16070 chip the plate solves with my local astrometry.net server can take many seconds (sometimes over a minute). So, I thought I try it out. Luckily they have a 60 day trial license (it costs $150!!!) I downloaded that and then the necessary star catalog (http://gsc.dc3.com/GSCInstall.exe).
Installation of both was straight forward. As I only want to use PinPoint as a plate solve in the background, I didn't bother trying to figure out how it works. Integration in SGPro was straight forward (just pointing it to the star catalog installation directory).
My first plate solves (on images that I previously took) were WAY fast - they almost felt instantly. When I then used it for real imaging, I realized that this was actually the normal speed: maximum 1 second, most of the time faster then that.
... and now I'm hooked. Not sure if I will be able to go back to astrometry.net once the license expires...

Sunday, September 7, 2014

Pelican Nebula (IC 5070) - and a star too young to be seen

The Pelican Nebula is an H II (Hydrogen II) region in the constellation Cygnus. It is next to an even larger nebula - the North America Nebula. Both nebula are separated by a molecular cloud filled with dark dust. Young stars that formed in the nebula heat up the gas and cause an ionization front that slowly moves outwards from the nebula. Denser and regions of the gas remain colder and can be seen as pillars extruding from the front. At the tip of one of these pillars, two jets can be seen - emitting to both sides of the so called Herbig-Haro object 555. They indicate the presence of a protostar - a star in the very earliest stage of development, when interstellar gas is still undergoing gravitational collapse, and nuclear fusion at the core has just begun. These stars don't emit any light yet and can't be directly seen.

This is the Pelican Nebula (middle-right) with a small part of the North America Nebula (left). And between them the dark dust that separates them.
(click on the image to get full resolution picture)

This zoomed-out section shows the ionization front and two of the pillars:

And this is the pillar with the 2 jets at its tip:

This image was taken from our backyard in San Jose. It consists of 18x10min Ha, 25x10min OIII and 28x10min SII data. First real image with the Takahashi Super Reducer.

Trying out new things with PixInsight: Noise reduction, removing magenta from stars

One of my experiences with PixInsight has been that it is way too easy to overdue the noise reduction and give images a waxy look. When looking for some advice on noise reduction, I found a comparison of various noise reduction algorithms in PixInsight. It recommends to use TGVDenoise as the most effective tool. And luckily I found a tutorial on how to use TGVDenoise.

I found it surprisingly easy to use TGVDenoise (I love the PixInsight tools that don't have a gazillion parameters...). Here is a closeup of an image of the Pelican Nebula:

Before noise reduction:

After noise reduction:

The noise reduction is noticeable but quite subtle - and some noise is still there. Looking closer at some details:


You can see, that the fine details are still preserved!

Next, I stretched the image and got this:

As usual in narrowband images, the stars have a strong magenta tone. But I found a forum post for a PixelMath expression to remove these:

R: $T[0]
G: iif((CIEL($T)>MIN_BRIGHTNESS)||((min($T[0],$T[2])/(max($T[0],$T[2])>MAGENTA_DEFN))&&(mean($T[0],$T[2])>$T[1])),mean($T[0],$T[2]),$T[1])
B: $T[2]

Now, the stars don't have their magenta color anymore. But also the dark areas of the image on the right have less of a reddish hue. The only problem I saw is that it creates noise around really bright stars:



I asked on the Pixinsight forum if there is a way to avoid this.

Thursday, September 4, 2014

Using SGPro and CCD Autopilot simultaneously

One feature I am really missing from SGPro is to take dusk/dawn flats. Especially for narrowband filters, an LED panel doesn't work well. If I'm at my scope early enough, I usually run CCDAP at dusk to take the flats and then connect SGPro to start imaging.

But recently I kept the camera connected in TheSkyX and then connected the camera (and filter wheel) in SGPro. I noticed this mistake a few hours later ... but everything worked.

I then checked if I could also take images from TheSkyX - and it worked too.

So, as long as I don't try to image from both apps at the same time, they CAN CONNECT SIMULTANEOUSLY TO THE CAMERA AND FILTER WHEEL! So, now, I'm connecting both programs at the beginning of the night. Let SGPro run but set an end time 30 minutes before the sun reaches the altitude that I entered in CCDAP to start flats. And then click "Take Dawn Flats" in CCDAP. Now, SGPro happily runs the entire night. It stops in the morning and parks - or the imaging session gets cancelled and SGPro parks the scope. And then in the morning CCDAP kicks in, unparks the scope and starts taking flats. Voila!

Tuesday, September 2, 2014

The Soul Nebula (Sharpless 2-199)

The Soul Nebula is a large emission nebula in Cassiopeia. Inside the nebula some stars formed. The wind from the most massive stars carved out large cavities in the nebula. This process pushes the gas on the outside of the cavities together - and ignites new stars. You can see several such cavities in this image. Analysis has indeed shown that the stars in these cavities get younger with distance from the center of the cavities.

(click on the image for full resolution)

This image consists of 5.1 hour integration time. It was also acquired on my recent trip to Richard's ranch near Yosemite.