June 2015 - Silios.gr

NGC6910 Gamma Cygni and nebulosity

HaRGB version of the beautiful Gamma Cygni and surrounding nebulosity region.

NGC 6910 is a Y-shaped cluster oriented northwest southeast. The two brightest stars are of magnitude 7.NGC 6910 is a small cluster, only 10′ in diameter

The southernmost star is SAO 49563 (or V2118 Cygni), a variable star of spectral type B1.5Ia. Gamma Cygni, not far off the galactic plane is subject to a great deal of interstellar extinction and reddening from interstellar dust. The dust selectively absorbs and scatters blue light (roughly 1/wavelength), so when you look at a star through dust it will appear redder than it really is (basically the same reason the sun is reddened at sunset). The intrinsic B-V color of a B1.5Ia super giant is -0.2. The observed color is 0.83, about the color of a K0 dwarf or a G5 giant, so the star appears yellowish to the eye. Notice the yellow stars in the cluster, caused by interstellar dust, and the bluish-white stars in the vincinity of NGC 6910.

Technical details
Sky-Watcher 80ED Pro Black Diamond
SBIG 8300M
HEQ5 Pro
QHY5
Skywatcher .85x Focal Reducer & Corrector
PixInsight, Main Sequence Software SequenceGeneratorPro
Accessories: Starlight Xpress Starlight Xpress FW 5*2”
Resolution: 1676×1266
Dates: June 13, 2015

Frames:
Baader 7nm Ha 2”: 10×300″ -5C bin 2×2
Baader Blue 2″: 10×120″ -5C bin 2×2
Baader Green 2″: 10×120″ -5C bin 2×2
Baader Red 2″: 10×120″ -5C bin 2×2

Integration: 1.8 hours
Darks: ~50
Flats: ~10
Bias: ~300
Avg. Moon age: 25.75 days
Avg. Moon phase: 15.29%
Bortle Dark-Sky Scale: 2.00
Temperature: 17.50

Annotated version :

M106 Spiral galaxy and neighbors

Messier 106 (also known as NGC 4258) is a spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781. M106 is at a distance of about 22 to 25 million light-years away from Earth. It is also a Seyfert II galaxy. Due to x-rays and unusual emission lines detected, it is suspected that part of the galaxy is falling into a supermassive black hole in the center. NGC 4217 is a possible companion galaxy of Messier 106.

Contains: NGC 4346, M 106, NGC 4258, NGC 4248, NGC 4220, NGC 4217

Characteristics
M106 has a water vapor megamaser (the equivalent of a laser operating in microwave instead of visible light and on a galactic scale) that is seen by the 22-GHz line of ortho-H2O that evidences dense and warm molecular gas.
These water vapors give M106 its characteristic purple color. Water masers are useful to observe nuclear accretion disks in active galaxies.
The water masers in M106 enabled the first case of a direct measurement of the distance to a galaxy and thereby providing an independent anchor for the cosmic distance ladder.M106 has a slightly warped, thin, almost edge-on Keplerian disc which is on a subparsec scale.

It is one of the largest and brightest nearby galaxies, similar in size and luminosity to the Andromeda Galaxy.
M106 has also played an important role in calibrating the cosmic distance ladder.
Before, Cepheid variables from other galaxies cannot be used to measure distances since they cover ranges of metallicities different from the Milky Way’s.
M106 contains Cepheid variables similar to both of the metallicities of the Milky Way and other galaxies’ Cepheids.
By measuring the distance of the Cepheids with metallicities similar to our galaxy, astronomers are able to recalibrate the other Cepheids with different metallicities, a key fundamental step in improving the distances to other galaxies in the universe.

Technical details
Sky-Watcher 80ED Pro Black Diamond
SBIG 8300M
HEQ5 Pro
Guiding : QHY5
Skywatcher .85x Focal Reducer & Corrector
Software: PixInsight, Main Sequence Software SequenceGeneratorPro
Accessories: Starlight Xpress Starlight Xpress FW 5*2”
Resolution: 1676×1266

Dates: June 13, 2015

Frames:
Baader Blue 2″: 15×240″ -5C bin 2×2
Baader Green 2″: 15×240″ -5C bin 2×2
Baader Red 2″: 15×240″ -5C bin 2×2

Integration: 3.0 hours
Darks: ~50
Flats: ~10
Bias: ~300
Avg. Moon age: 25.75 days
Avg. Moon phase: 15.29%
Bortle Dark-Sky Scale: 2.00
Temperature: 17.50
RA center: 184.451 degrees
DEC center: 47.451 degrees
Pixel scale: 4.272 arcsec/pixel
Orientation: 176.036 degrees
Field radius: 1.246 degrees

Annotated version :

Nikon D90 in astrophotography – sensor specifications

The Nikon D90 was a very popular DSLR back in 2008 when it was released and still is a substantial camera.
Using any camera in astrophotography gets you to a point where you need various details about the sensor, in order to calculate the Field Of View with a particular lens or telescope, be able to plate solve your astro images and a lot of other things.

Interestingly there was very little in-depth information about Nikon D90 Cmos sensor and its internals in general, so here is a list of all the info i have gathered over time for the particular model.

Brand	Nikon
Model	D90
Effective MegaPixels	12.30
Sensor dimensions	23.6 x 15.8 mm
Sensor type	CMOS
Sensor resolution	4281 x 2873
Crop factor	1.52
Diagonal	28.40 mm
Surface area	372.9 mm²
Pixel pitch (size)	5.51 µm
Pixel area	30.36 µm²
Pixel density	3.29 MP/cm²
ISO	Auto, 200 - 3200 (plus 6400 with boost)
Exposure Compensation	±5 EV (at 1/3 EV, 1/2 EV steps)

The sensor has a surface area of 372.9 mm². There are approx. 12,300,000 photosites (pixels) on a NIKON D90 sensor.
Pixel pitch, which is a measure of the distance between pixels. Pixel pitch tells you the distance from the center of one pixel to the center of the next. Pixel size (pitch) is essential in astrophotography.
Pixel or photosite area is 30.36 µm². The larger the photosite, the more light it can capture and the more information can be recorded.
Pixel density tells you how many million pixels fit or would fit in one square cm of the sensor. Nikon D90 has a pixel density of 3.29 MP/cm².

One shot color camera sensors are usually arranged in a specific order, one of the most well known being the Bayer pattern.

The Bayer pattern in Nikon D90 in case you have raw files that you need to manually de-bayer them is GBRG (Green, Blue, Red, Green)

DIY Telescope mount pier HEQ5 PRO

The bane of astrophotographers is, in my opinion, the routine of setting up and dismantling the gear on every session. As time accumulates this becomes a rather tiresome process, hindering the excitement of astrophotography where the need for really accurate polar alignment is paramount.

That is where a permanent installation, a.k.a pier comes into play (provided you are ok, to just securely cover up your gear for protection of the elements).

My mount is a skywatcher HEQ5 PRO Synscan, though the pier can host any type of mount by changing the top adapter.

The design had to comply with the following goals :
a) The leveling of the pier would be on the bottom and it would have to be massive for two reasons:
— Contrary to popular belief, the top does not have to be level. It is better to have a really stiff top since you will be doing drift alignment anyway with a permanent setup.
— There is no point, mechanically speaking, to mount a 40kg steel tube on M13 rods (there alot of tops in the internet with M13 bolts for adjustments which just scream flexure with anything heavier than an ED80 and even more so the same goes for the bottom design
b) There would be no holes in the rooftop in order to protect the water seal in the construction.

So here is the photo story of the building!

Taking the approppritate mesurements for the fitting the HEQ5 PRO head adapter to pier’s top plate.

Uber lathe work on aluminium by my brother in law (Thanks Tom!)

Finished product, top plate ready to be welded on the tube.

Testing the fit 🙂

Welding the M30 threaded bars to the base plate. By Tom of course!

The pier is ready

Another view of the finished pier.

The pier and the base plate ended up weighing some 75kg, which we had to haul in the 5th floor (rooftop) by the stairs since there is no elevator yet 😀

Oil paints, 2 part epoxy glue, white spirit solvents and in general chemicals require some kind of protection. Thus the mask for the fumes and the glass (i am nearsighted(myopia) but they work as protection from splinters, most of the time at least..)

Various assortments for gluing, sanding and painting of the pier

2 part epoxy cement. Yes, this stuff is from hell so do wear gloves, berathing mask and general protection.

The base plate orientation was tagged with white spray the previous night after a rough polar alignment.

Finally ready after two hands of oil painting, sanding in between and gluing the base plate to the floor. By the way the 2 part epoxy resin turned out to be massively better than its description. After allowing the 24 hour requirement for it to be properly cured i would need some kind of demolishing device to remove the base from the floor!

Super design skills at work here in order to make the blueprint for the holes and cuts needed on the plexiglass accessory tray.

Future upgrade plans include building a proper astronomy shed – observatory around it but that will have to wait for a while 😀

Kudos to Tommy, for the help!