One
year since my last post in this blog. If I had to explain that, the main reason
(maybe not the only one) is that I have been too busy. And one of the reasons
why I have been too busy is that I have been studying an official Master of
Science (MSc) in Astronomy and Astrophysics. Let me say upfront that it was
much tougher than I thought at the beginning, but also much more rewarding. I
had the privilege to have, as professors, fantastic professional
astrophysicists who were able to transmit their enthusiasm and love for this
science. And in the case of my Master Thesis director, Dr Antonio García
Hernández (University of Porto, Portugal), also
the feel for science discipline, rigour and curiosity - apart from a lot
of his time, which I greatly appreciate. I guess that in the future I may post
from time to time articles related to what I learned in the MSc; for now, I'll
start with the Observational practice that we had.
In this
practice we had to carry out, as a group of five students, a real observation,
following profesional protocols. In our case it was done at the Observatory of
the Valencia University, located in Aras de los Olmos (Valencia), abbreviated
as OAO. The practice started with completing a proper observation proposal. In
this case I did that part, trying to take advantage of the Richey-Chretièn
telescope of 600mm aperture available in the OAO, with an Apogee camera of 4000
x 4000 pixels, and specially having the renowned astrophotographer Vicent Peris
as operator of the observatory (he is also one of the developers of PIXINSIGHT
software).
The chosen target was NGC 6820, an emission nebula in Cygnus, associated to an open
cluster, NGC 6823, which I have already photographed from my "Mar de la Frau" Observatory at home:
From
three nights at the OAO, we could use only two, due to weather conditions. This
was early July, so nights were very short. We could only take 6 hours with a
3.5 nm H-alpha filter, in 3 or 4 minutes subframes. Why so short? Because these
professional equipments, surprisingly or not, are not ideal for taking
"beautiful postcard" type of astrophotos. Typically, the photos taken
by them are of very short exposure, up to a few minutes, for photometry or
spectroscopy, so they do not need a highly precise long term guiding system as we
amateur postcard-photographers need. In this case, the telescope, a RC as I
mentioned with focal length of 4800mm on a fork mount, was not guided, so
despite the quality of the instrument the stars were not round after a few
minutes, specially near the zenit. Focusing was done by manually turning the
motor in and out. The filter wheel houses twelve filters for the most common
photometric systems. We used the RVB from Johnson plus the H-alpha. Each filter
gives a field of 33x 33 arcmin. MaximDL is used for capture.
For the
observation proposal I used a very useful and free piece of software, which
allows you to program your observation session by checking, for a given night,
the path along the sky of the object you want to observe. It was developed by
the team of the Isaac Newton telescope at the Roque de los Muchachos
Observatory in La Palma, Spain. This is the link:
So,
after taking all the calibration frames and the light frames, and processing
with Pixinsight, the result was:
Then,
with this photo, we did comparisons versus other photos of the same object
published years ago. In a 1974 paper we found a photo, quite poor for modern
standards, where we found a star with a significant position change.
Investigating the subject, we found that indeed this is a star well known for
its fast proper motion. Very interesting!
Preparing
the work on NGC6020/6823, I checked the photos available in Aladin at different wavelengths. I
found a series of frames taken with the GLIMPSE camera of the Spitzer
satellite, all in infrared. I downloaded them as raw fits, and when I processed
them a bit I was astonished to see the beautiful details in the 8 microns
photo. In the other frames at lower wavelength (closer to visible) the level of
detail was decreasing. Infrared, light of lower energy than visible, allows us
to see subjects that have lower temperature than visible objects, like dust
clouds and cold gas (hydrogen) clouds that have not been excited by surrounding
stars with enough energy to emit visible light. In fact, the landscape of the
NGC 6820/6823 area seen in infrared has nothing to do with the one that is
familiar to us from visible light. It took me a while to convince myself that I
was in fact looking at the same region.
This is
the 8 micron photo from GLIMPSE, processed by me with PIXINSIGHT, and a photo
in fralse color in which I have combined the photos at 3.6, 4.5, 5.8 and 8.0
microns.
One conclusion (not very scientific but someone
had to say it) is that, when we jokingly say that the Universe if in fact quite filthy
and full of dust, gas, residues of primitive clouds, supernova explosions and
who knows what… If you look in infrared it is even worse.
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