Photometry for Astronomers

Photometric results of VAO Observations on 11/21/2011

Astronomers interested in the variability of stars need a tool to understand how they vary in time.   This tool is called photometry and it is widely used by astronomers to study not only intrinsic star variability but the more familiar exoplanet transit searches.    It is also used to study galaxies and other extended objects.  So why study changes in "brightness"?

Changes in brightness can lead to the discovery of eclipsing binaries, transiting exoplanets, exotrojans and exomoons.   It can tell you about the morphology of Active Galactic Nuclei and about the properties of supernovae explosions.  You can infer from the data when you collect it over time about the physical properties of the object you are studying.

The plots to the right are examples of light curves or in other words many measurements of the intensity of stars over a period of time.  On the horizontal axis you have number of exposures. On this particular case each tick on the axis is roughly 80 seconds.  On the vertical we have the instrumental magnitude of the star.   As you can tell by the graphs there are stars on this ensemble that vary on time scales of hours.  These measurements were taken on VAO in Webster NY and the graphs are the results of the photometric pipeline I setup for this particular field.

The WIYN 0.9m Observatory @ Kitt Peak

Kitt Peak National Observatory

Today there are no pretty pictures of the wonders of the Universe from the VAO observatory in Webster, NY. Instead, I bring you images of where I will be for the next week,  Kitt Peak National Observatory.  Located 56 miles from Tucson, Arizona at an elevation of 6,875 feet above sea level.   KPNO has the largest collection of telescopes in the world. 24 optical telescopes and 2 radio observatories.  

So why KPNO?

On the left, the WIYN 0.9 m Observatory

KPNO houses the WIYN consortium 0.9 meter telescope of which Rochester Institute of Technology is a partner among other educational institutions.   As part of the partnership, faculty and students of RIT  have the opportunity to conduct research and educational projects.   

Why is this important to me, you say? Well to begin, the night sky at KPNO is one of the best in the nation and the opportunity to image with a telescope that is 3 times the aperture size of the one I have is compelling.  Not to mention this will advance 2 of the projects I am currently working on.  The first project is on AGN (Active Galactic Nuclei), galaxies where their central super massive blackhole is accreating mass.  The second project is on the characterization of transiting exoplanets and their apsidal precession due to the effects predicted by Albert Einstein's theory of General Relativity.

Stay tuned for the results of this trip!

M78, McNeil's Nebula, v1647Ori what do these things have in common?

M78, McNeil's Nebula and v1647Ori
©Billy Vazquez, 2011 @ VAO Webster, NY

They are all part of the Orion Molecular Cloud Complex.  They are also part of these image taken from VAO a few nights ago.  M78 on the upper left corner of these image is an HII region and it the brightest and most prominent object of this field but regardless there are several other nebula like objects, for example McNeil's Nebula.   

McNeil's Nebula has a very interesting story behind it.   Discovered by McNeil in 2003 after having done an exhaustive search on this field at different epochs.  But was it really a new object in the sky?  Apparently as close to the mid 1960s and by no other than an amateur astronomer(Evered Kramer).  There is clear evidence that the nebula was visible then.   So how come it disappeared just to reappear again for McNeil to find?  This is still the topic of active research.   The prevalent explanation is that the young star v1647Ori has episodic outburst whose light reflects and scatters by the dust in McNeil's Nebula.

These outbursts from young stars and their associated nebulosity are coined Herbig-Haro objects and they are like I said still the subject of astronomical research, so that we can understand the physics that powers this phenomena.

M103

M103 from VAO, Webster, NY
© Billy Vazquez 2011

A young open cluster in the constellation Cassiopeia. But how young is young, that is the question?  The age of this open cluster was estimated to be around 16 million years at a distance of 2900 parsec (Sanner et al., 1999).    The Solar System is roughly 4.5 billion years old.  If we use the age of our solar system and compare it to the stars in this cluster we come to the conclusion that the cluster is younger by 3 orders of magnitude.

M103 from VAO, Webster, NY
© Billy Vazquez 2011

How do we know which stars in the field of view are part of the cluster?    For that, we study the proper motion of the stars, which is the angular displacement over time with respect to the barycenter of the solar system.  All stars that belong to the cluster will have roughly the same proper motion. This indicates that the stars are gravitationally bound and traverse the Galaxy as a unit.

The images of M103 shown were taken using a Johnson V band filter with VAO's 12" SCT @ f/6.3.  They are 36x60 sec exposures co-added in Maxim DL for a total exposure time of 36 minutes.  The imgages were dark and flat subtracted but no further image processing performed other than the color inversion of the second image.

Horsehead Nebula

The Horsehead Nebula also known as Barnard 33 is a dark nebula in the constellation Orion and it is located just south of Alnitak.  This dark nebula is located about 1500 light years away from Earth. The red glow is imparted by ionized hydrogen from nearby star Sigma Orionis.

The image shown was taken at VAO with broadband Johnson BVR filters.  Total exposure time is 55 minutes ( 4x300s on B and V, 3x300s on R filters).   It was further processed in PixInsight for dark subtraction and flat field division.  A median noise reduction algorithm was used with a 3x3 kernel to eliminate most of the chrominance noise.   The telescope used was the 12" inch SCT at f/6.3.   Guiding was done with Metaguide with an 80mm APO refractor and Lumenera Skynix. 

In addition I present to you the unedited out of the telescope combined image of 55 minutes on a single grey channel.  You can see the vignetting of the smaller filters over the larger CCD chip area.  As you would imagine this nebula would look much better over narrowband filters to expose more of the filamentary structure at the edges of the dark nebula.

Double Cluster - NGC 869

NGC 869 in Perseus
©Billy Vazquez @ VAO Webster, NY  9/18/2011

NGC 869 in BW
©Billy Vazquez @ VAO Webster, NY  9/18/2011

The Double Cluster are two open clusters in the constellation Perseus.  The one in the images is NGC 869 at a distance of 7600 light years.   It is believed it is about 13 million years old and it is also known as Cadwell 14.

The images were taken with the 12" SCT at f/6.3 with Astrodon Johnson VBR filters.   Total exposure time was 2.5 hours.  I am still using the Orion Parsec camera.  In this instance I binned the image 2x2.

The mass of NGC 869 is estimated at 3700 solar masses with a color excess B-V of 0.56.  Both clusters are near identical in age, distance and  redenning.  Whether the double cluster is the core of the Per OB1 association is still in debate according to Slesnick et al. 2002.

M36 - An Open Cluster in Auriga

©Billy Vazquez @ VAO Webster, NY  9/11/2011

The open cluster M36 was discovered by Giovanni Batista Hodierna, an Italian astronomer of the 17th century. Rediscovered by Charles Messier as entry number 36 in his catalog.

©Billy Vazquez @ VAO Webster, NY  9/11/2011

The cluster is rather young with an approximate age of 25 million years and it is roughly at a distance at 4,000 light years.  The brightest stars on the image are of spectral type B.




This means these stars have temperatures that reach up to 33,000 K.  These stars are also very fast spinners.   You might ask how do we know they are fast rotators?   The key is on a technique called spectroscopy which breaks the light of the stars into its different emission and absorption lines and from the width of these lines we can tell the rotation speed.  

The image was taken from my observatory and it is a LRGB color combined image.  3 x 5 minutes exposures over each Johnson filter and 15 minutes exposure over a luminance (IR Blocking) filter. 

Orion's Nebula - M42

M42 - Orion's Nebula
©Billy Vazquez @ VAO (Webster, NY) 9/4/2011

I remember when I did my first "Big Upgrade" to a Dobsonian 10" reflector and I took the "Little Monster", that is how I playfully called it, outside for a first light.  It was a cold winter night but that is no deter for an avid astronomer.   Orion's Belt was clearly visible to the naked eye and I remember the beautiful images of Orion Nebula's  from my old dusty books.  Not to mention all the beautiful Hubble images on the Internet.

Well, some years have gone by since that day  outside where Orion's Nebula was a fuzzy blob on the eye piece. Both technology and my equipment have advanced quite a bit since then. I present to you last night's Orion's Nebula.  An RGB composite of 7x20 sec exposures over each filter (Bessel V, Bessel B and H-Alpha).  Post processed with MaximDL.   The scope is my 12" LX200 ACF SCT at  f/6.3.

Orion's Nebula is a stellar nursery 1,344 light years away.  It is the closest star formation region to our Sun. And its span is about 24 light years across. The 4 stars at the center that are barely resolved are part of the Trapezium open cluster.  M42 is an astrophotogpaher challenging target as its stars are much brighter than the surrounding nebulosity. 

SN 2011fe at M101 aka PTF11kly

SN 2011fe in M101
08/26/2011 2 10:26 PM EST
©Billy Vazquez from Webster,NY @ VAO

Supernova 2011fe in M101 on August 26th, 2011 from Webster, NY at the Vazquez Astronomical Observatory.  Using the 12" SCT at f/10.   10 stacked exposures of 150 seconds, dark subtracted and flat fielded. No other processing done on the image other than the big black arrow pointing to the Supernova Type 1a, 2011fe.  From Webster, NY M101 starts at around 40 degrees of elevation from the horizon on the West at this time of the year.  Unlucky for me my West view of the sky is limited to about 37 degrees of altitude and above so I had a small window of opportunity to image the galaxy.

Nevertheless, it is a rare opportunity for an astronomer to be able to image a supernova event with his own observatory.  So this is a first for me and I feel pretty good about the results.  Next to do some photo metric analysis of the data and confirm its apparent magnitude.

Dragonfly Cluster - NGC 457

NGC 487 - 2 minute exposure over RGB filters
12" SCT, Orion Parsec, f/6.3
©Billy Vazquez

The Dragonfly Cluster also known as the Owl Cluster is about 1,790 light years away from the Sun in the constellation Cassiopeia.  The cluster is fairly young at an approximate age of 21 million years.  The image to your right is the RGB composition of images taken at the Vazquez Astronomical Observatory (VAO).  2x2 binned, 2 x 2 min exposures stacked on red, green, blue filters.  

2 minutes of exposure doesn't do justice to this beautiful star cluster.  So therefore, I should come back to it someday and extend my exposure time to get some of the faintest stars.  But for now enjoy the view.

NGC 281 - Pacman Nebula

NGC 281 - The Pacman Nebula
© Billy Vazquez 2011
VAO @ Webster, NY

As I was growing up, I remember my first refractor telescope that my grandmother bought for me at the Hayden Planetarium in NYC. I was 8 years old and I felt like a million bucks.   I remember the first light of my 2 inch refractor as I attempted to look at the night sky from my parents suburban residence in Puerto Rico.  I could see the stars but it made me wonder where were all those galaxies and nebulas I have seen in books?  Why can't I find them?

It took me some years but finally, I found them.   The image shown here its the PacMan Nebula, NGC 281.  I took this image from VAO using the 30cm LX200 ACF, 5 minute exposure in LRGB filters, post processed by MaximDL and Photoshop.    The nebula is a HII region, where you can see dark patches where no light is coming from.  These dark patches are called Bok Globules and it is where the magic happens.  Stars are born within the Bok Globules but the material around this new born stars is so dense that we cannot see them in optical light.

M11 - NGC 6705 - The Wild Duck Cluster

M11, also known as the Wild Duck Cluster is an open cluster in our own Milky Way that contains about 2900 stars.   It has an estimated age of 220 million years.

A few nights ago, just before the clouds rolled in Webster NY.  I decided to capture this magnificent cluster and see, how does it look like in color.   To my surprise this cluster has many stars of different colors.  

I used 4 x 60 second exposures stacked on each channel, LRGB.   The top image its a powered up Photoshop enhanced version of M11.  I like to call this stars in steroids.  I felt a bit compelled to play the artist and see what I could do with it.

The middle image is just the LRGB color combine.  This image only has flat and dark subtraction processing.  So it should give you a clear indication of the colors of the stars.

The image at the bottom is just the stacked images on the luminance filter.  The only processing done on that image is dark substraction.  So it should give you an idea of how the cluster look like before any additional processing.

I can't help but to think what if we lived inside an open cluster like M11.   How would the night sky look like?  I can imagine hundreds of magnitude 1 stars all over the night sky.  It would be awesome!

M15 - NGC 7078

M15 is a Globular Cluster in the constellation Pegasus.  It is is one of the oldest globular clusters known.   It is about 33,600 light years away and its total luminosity makes it 360,000 times more luminous than our Sun.  It is believed that at the center of M15 there is a blackhole that has pulled together a large concentration of stars orbiting it.

For the amateur astronomer this globular cluster looks like the image to your right.  The image was taken last night form VAO and it is a RGB color composite.   The exposure time was 20 seconds on each filter.   I post process the final image in photo shop for the artistic spikes on the foreground stars.

Now, I prefer grey scale  images myself so here is a rendition of  M15 in just the V band filter same exposure length and no processing.  You can see how cleaning up the image and stacking the 3 color filter images make for a more pleasant look.  But sometimes you really just want to see what comes right out of the telescope.  So I will give you both so you can enjoy the view.

M27 - NGC 6853 - The Dumbbell Nebula



M27 - Dumbbell Nebula

It started all with a cloudy night, where I was taken glimpses of stars between cloud and cloud, to determine the quality of my new optical setup.  I was not planning on an observing night but sometime after 12:30 AM, the clouds stopped going by and the night sky opened up.   Like a good astronomer, I decided to work on some imaging for a science project, I am currently working on.    As the morning hours went by and I was about done with my imaging for the night, I looked at my planetarium software and see the label, M27 not far from my current position.  

M27 in false colors

Well it happens that M27, also known as the Dumbbell Nebula is a beautiful planetary nebula in the constellation Vulpelcula. It signals the end of the life of a star. In its center there is a star remnant called a white dwarf. The expanding material that we see spans about 3 ligth years across. The nebula itself is 1,360 light years away.

The images were taken last night from VAO, 3x60 second exposures on the luminance filter, binned 2x2 with an Orion Parsec Monochromatic camera with my LX200 ACF 12" telescope at aprrox. f/6.3

Distances in Astronomy

© Billy Vazquez 2011

We look at the night sky and everything seems equally distant from our point of view.   The reality is quite different.  Astronomers study celestial objects and can determine their distance from Earth.   To the right an image taken from VAO(Vazquez Astronomical Observatory). The first one to the right is of a distant galaxy named Mark876.  But where is the galaxy in that image?  Well is very small and point like.  Just like any other star in that image. That is because this galaxy is so far away from us that it looks as just another star in the sky.  What we see, is its bright nucleus at a distance of  476.5 Mpc.  A parsec is 30,857 billion kilometers.

© Billy Vazquez 2011

The second image reveals M101 also known as the Pinwheel galaxy.   It is a spiral galaxy and there is no mistake, we can tell by the look of it that it is indeed a galaxy.  How far is it?  It is merely 3.4 Mpc away.  That is just 104,739,957,746,478,873,239 km away from Earth.  Definitely closer than Mrk 876.  How do we know the galaxy is so far away?  Lucky for us there are stars in the universe called Cepheids, which change brightness periodically.  Using their change of brightness we can determine their distance to Earth.  Galaxies like M101 are beautiful sights for astrophotographers.

© Billy Vazquez 2011

Last but not least, I present M13 the globular cluster in our own Mily Way Galaxy.   How far is it?  It is just shy of 236,513,210,000,000 km from Earth.   The light from the stars of M13 as seen today is about 25,000 years old.  Therefore as we look into the night sky we look into the distant past of the Universe.  It makes you wonder how so many stars got all clumped together and they still navigate through our Galaxy as a single unit.

Green Bank Radio Astronomy at NRAO

Credits: 2011 Billy Vazquez, GBT @ West Virginia , NRAO

Radio Astronomy refers to the study of the electromagnetic spectrum between wavelengths of 0.3 mm to 30 m.  This covers frequencies between 1 THz to 10 MHz.    The largest Single Dish Radio Telescope on the continental US is the Green Bank Telescope in West Virginia.  It is only surpassed in dish area by the Arecibo Radio Telescope in Arecibo, Puerto Rico.  Arecibo has greater sensitivity, but operates only between 50 Mhz to 10 Ghz.  It is also restricted to plus/minus 20 degrees from its current latitude of 18 degrees, as the dish is non-steerable.  Green Bank can operate at higher frequencies above 100 Ghz and it can fully track any object in the sky above 5 degrees above the horizon.

Credits: 2006  M. Blanton , D.  Hogg and the SDSS

To the right two images of the same galaxy, NGC 5668.  It is a spiral galaxy as you can see from the optical image to the right with a clear bright core.   Also to the right the radio spectral image of the same galaxy at 1.4 Ghz.   This particular frequency is very useful for astronomers as it gives us lots of information about the observed celestial object.  This line, also known as the 21 cm line, tells us the radial velocity at which this galaxy is receding away from us.   In this case roughly about 1575 km/s away from us.  The graph also tells us that there is rotation of hydrogen gas as can be shown from the double horn feature.   Some of the gas is blue-shifted towards us , while some is red-shifted towards us at about a rate of 50 km/s.

The power of radio astronomy lets us determine many properties of celestial objects and it will only get more interesting in the future as new and improved facilities like the EVLA  and ALMA start producing new science.

M33 - The Triangulum Galaxy

M33- The Triangulum GalaxyLRGB composition
2600 second total exposure time, false colors
300mm, f/6.3, Orion Parsec 5.4 micron, 2x2 bin

At an estimated distance of about 900 kpc (give or take some kpc), this galaxy is part of the Local Group.  The Local Group is a collection of galaxies which also contains the MilkyWay and Andromeda among other small dwarf spheroidal galaxies. M33 as it is also known in the Messier Catalog is a spiral galaxy with an approximate mass of 50 billion solar masses and roughly 40 billion stars!  Its apparent magnitude is 5.72 which makes it an ideal extended object to test the darkness level of your observing site.   If you can see M33 with averted vision then you know you are in a pretty good site for astronomical observations.

The image to your right was taken on July 4th, 2011 from VAO in Webster, NY.   It is rendered in false colors to enhance the contrast areas.   I took 3x300 seconds exposures through a luminance filter with IR blocking. 3x200 second exposures through RGB filters, then reduced and combined.

M33- The Triangulum GalaxyLRGB composition
2600 second total exposure time, monochromatic
300mm, f/6.3, Orion Parsec 5.4 micron, 2x2 bin

For those of us who like monochromatic images, here is the combined image before processing with false colors. VAO is now ready for some science runs.  That includes transiting exoplanet exploration and AGN(active galactic nuclei) imaging.  Stay tuned for some more science!

Clear Skies!

NGC 7635 - The Bubble Nebula

NGC 7635 - The Bubble Nebula
3x1000sec exposures/each - Ha/R/G/B filters
© Billy Vazquez @ VAO Webster, NY 6/1/2011

The image to your right is NGC 7635, also known as the Bubble Nebula.  It is a combined image through the Ha, R, G and B filters.  Each filter frame is the combination of three 1000 seconds exposures for a total exposed time per filter frame of 50 minutes and a grand total of 3.33 hours of exposure time to create the beautiful image you see to your right.  The image was processed as per the usual data reduction pipeline of dark and flat fields. 

The Bubble Nebula is found in the Cassiopeia constellation, relatively close in the night sky to another interesting object, open cluster Messier 52.   The bubble is created by the stellar winds of a massive hot star SAO 20575.  SAO 20575 is an O type star, which is about 10-20 more massive than the sun  and about 4 times bigger.  It is located 11,000 light years away from us and the bubble spans about 10 light years across. 

NGC 7635 - The Bubble Nebula
50  minute Ha exposure
© Billy Vazquez @ VAO Webster, NY 6/1/2011

Although the color image is evocative, I like to present to you what the Ha channel frame looks like without any editing and spanning the whole view of the CCD.   The monochromatic image gives the observer a new perspective of the celestial object.  You can see also how the nebulosity spans many light years away from the hot O star.

I am glad to report that the efforts to get the telescope to provide the best image possible have paid off.   This image is testament of the capabilities of my observatory.  Stay tuned for more exciting imagery and science.

The Moon

© Billy Vazquez @ VAO, Webster, NY

The Moon, now through an 80mm apochromatic refractor in the early morning hours of June 21st, 2011 from VAO in Webster , NY.   I used the Lumenera Skynyx 2.0M camera to image a sequence lasting 90.32 seconds.   I generated 444 FITS images from this sequence and used RegiStax to stack the best 70% of the images and combined them.  Then use the Wavelet Filter from RegiStax to come up with the image you see on the right.   Not bad for a cloudy night.   Not bad for a minute and a half of Moon time.

Next, I present you 30 seconds of raw unedited video for your viewing pleasure.  Keep an eye for the clouds rolling in.   Enjoy!

Saturn

Saturn, 6/14/2011, 11:58 PM EST
300mm, SCT, f/25, unbinned, unguided
Lumenera Skynyx 2.0M, 1533 frames, 13.1ms exposure
Stacked with Registax 6, total exposure 189.9 sec
©Billy Vazquez VAO, Webster, NY

People hear the word Saturn and the first thing it comes to their minds is... Rings! Well either that or you are a history buff and know that it is named after the Greek god of harvest, Saturnus. But if you are reading this, you are probably thinking about the gas planet in our solar system with the magnificient rings around it. Since I was a kid, I always wanted to look at Saturn through a telescope. What could be better than to see those magnificent rings, I heard so much about in books(back then there was no Internet as we know it today, books was all I had!). Well years have passed, and to the right is my first imaging attempt at Saturn from VAO. As you can see it is not the best image of Saturn. Either by my lack of experience imaging or because it was only about 10 degrees above the horizon. The closer a celestial object is to the horizon the worse the image gets. The reason for this is the Earth atmosphere. It protects us from solar radiation but its a nuissance for observational astronomers and astrophotographers.

Saturn, 6/14/2011, 11:58 PM EST
Sobel Edge Detection, Image processed with GIMP
©Billy Vazquez VAO, Webster, NY

Now back to Saturn, with a little bit of image processing we can obtain outstanding results even with poor quality images. I used a technique called Sobel Edge Detection. This technique is implemented in GIMP 2.6 an imaging processing software. As you can see on the image, it brings out the edge details of a picture and brings out the details of Saturn rings. Also, you can see details of Saturn bands.  So it is not a Hubble Space Telescope image but even under the worst conditions, this image makes you wonder what can be done under better "seeing".  Stay tuned there would be more Saturn(and hopefully better) in the future.

The Moon, Earth Atmosphere and Collimation

Bad Collimation
The Moon,  Mare Imbrium, Plato's Crater and the Montes Alpes
300 mm aperture, f/10, SCT, no filter, no guiding, no AO,
Lumenera Skynyx 2.0, Registax 6, 6/14/2011, 9:33 PM EST
©Billy Vazquez @ VAO, Webster, NY

The Moon is full on the night sky and last night from my observatory (VAO), I was put to the task to give the finishing touches to the collimation process.  If you recall, from the M24 blog, my SCT is in dire need of collimation.   With the help of Pempro Collimation, the Advanced CT Collimator from HOTECH and MetaGuide I can say that the telescope is nearly perfect collimated and ready for science runs.   To the right we see an image of the Moon taken before I finish the collimation process.   I capture 50 seconds of uncompressed AVI video with my Lumenera Skynyx 2.0 camera and processed it with Registax 6 to get the single stacked image you see.   As you can tell from the image it looks all blurry, but you can see where the crater is and where Monte Alpes strech.

Next, I finish the collimation of my telescope with MetaGuide using Vega as a my reference star. The results of my collimation are seen now to the right on the second image of the same area of the Moon. It is quite obvious, that there is an increase on the amount of detailed capture on the second image. The reason, is that the optics are now nearly perfect aligned. Which is what I have been working to achieve all along.

Good Collimation
The Moon, Mare Imbrium, Plato's Crater and the Montes Alpes
300 mm aperture, f/10, SCT, no filter, no guiding, no AO,
Lumenera Skynyx 2.0, Registax 6, 6/14/2011, 11:05 PM EST
©Billy Vazquez @ VAO, Webster, NY

So my next question was, how good or bad was the "seeing" last night? The Earth atmosphere is an important factor for ground based observations, specially at low altitudes. Webster, NY is approx 465 feet above sea level. Not Manua Kea, Hawaii or La Palma, Canary Islands by a long shot. Still the question remains, how was the seeing? Can we do some type of test? Yes we can! I took another image of the moon this time, by using a TeleVue Powermate 2.5x. It increases the magnification of the image at the cost of flux (light intensity). For the technically savvy, it increases the f ratio of my telescope to f/25.
So why didn't I do this from the very beginning?

The Moon, J. Herschel, Anaximander and Pythagoras Craters
300 mm aperture, f/25, SCT, no filter, no guiding, no AO,
Lumenera Skynyx 2.0, Registax 6, false color,
6/14/2011 12:09 PM EST ©Billy Vazquez @ VAO, Webster, NY

The devil is in the details.  Magnification of a signal comes at a cost of 2 things(mainly): decreased intensity and noise magnification.  What noise?  Ah yes, that is what we call all the undesired information in our image.  In this case the worst offender is our planet's atmosphere.  Still you see to your right an image of the Pythagoras crater and its surrounding neighborhood.  You can see the shadow cast by the sun on the craters and the peculiar mountain like structure right smacked in the middle of the crater.

So what was I "fussing" about noise and atmosphere?  The fuss is just that... lots of fuzzy and blurry details. The cause, the Earth atmosphere. The ideal location to image a celestial object is right above us, what astronomers call, the zenith. Unfortunately, I lack the technology to reposition the Moon to where I want to.  Therefore, I image the Moon at its current location in the sky which is just above 20 degrees above the horizon, hardly the place you want to image.  That is because a telescope has to go through a lot more atmosphere at lower altitudes than straight up at 90 degrees. Above there should be a video to demonstrate the effect of atmosphere last night.  

Asteroids!

Today we have Vesta on approach! Ehh... What is Vesta? Well, it is an asteroid! A big chunk of rock in the asteroid belt. Where is this asteroid belt, you may ask?  It is roughly between the orbits of Mars and Jupiter.  But where did they come from?   The answer is... From the same stuff the planets were made of, the primordial solar nebula.   But if that is the case,  why are they not planets?  Excellent question!  The asteroid belt destiny was to become a planet.  All those rocks were supposed to stick together but big Jupiter and Mars continously "tug" on these rocks adding gravitational energy to the mix and preventing the "planetesimal" (another funny word for big chunk of rock in space) to become planets.

So why is this asteroid named Vesta?  Well, I say... why not?  Ok, ok, like the planets, the first asteroids were believed to be planets and so they follow suit and named them after Greek Mythological Gods.  The first asteroid discovered was named Ceres in 1801, then Pallas followed in 1802 and Juno on 1804.   The fourth asteroid discovered in 1807 was named then Vesta by astronomer Heinrich Wilhelm Olbers.  The asteroid is 330 km in diameter and it is big enough to be considered a protoplanet (just shy of a planet).  The video above was provided by NASA's Dawn Spacecraft.

NASA's Dawn Spacecraft Artistic Concept

Supernova SN1987

2011 Hubble Space Telescope - SN1987

Supernova SN1987 is making the news again! Talk about fun that keeps up giving. This time the outer ring has gotten brighter as seen on this Hubble Space Telescope image to the right. The interesting question is why? But before we can answer that, it is important to define what we are talking about. A supernova is the explosion of a massive star, much more massive than our Sun. The physics that explain this explosion are complicated to say the least. But the important fact is that there was a star, it blew itself to smithereens when its core could not sustain the gravitational forces that were holding the star together. What remains is a remnant, either a blackhole or a neutron star.  

Wide Field View of the LMC, with Rolf Wahl Olsen inset.
This is an amateur image and inset, to put things into perspective.
Image from Bert (avadonk) IceInSpace

What does SN1987 stands for? The first 2 letters are supernova, the remaining 4 digits are the year it was discovered. Now to answer the previous question, why now? Well, scientists like to revisit interesting targets from the past and using the Hubble Space Telescope, they have found that the outer ring of this supernova is brighter. Why would this be? The simple explanation is that 20,000 years ago the host star was "shedding" material into space.  This star material began its expansion into space as seen by the ring around the SN.   The shock of the SN has finally caught up to this material and it is glowing in all wavelengths for us to see.

153 x 15s taken on 27/11/2010 with 10" Newtonian
f/5 and ToUCam Pro SC1, no filter, no guiding
Image Rolf Wahl Olsen, 2010

To the right an amateur image of SN1987 from Australia, using a 12" Newtonian telescope and a webcam at focal ratio f/5. Notice the difference in spatial resolution between HST and this image from an amateur. Rolf has done an outstanding job considering this image is done from the ground, with a telescope that has an aperture 8 times smaller than Hubble and with an off the shelf webcam. You can see the pink nebulosity clearly on his image.   You might ask well how come we can't image something from the ground like the Hubble does?   The answer is all around us...  Earth atmosphere.   It limits the spatial resolution we can obtain with telescopes.   That is, around a few arc seconds on a perfect dark night for amateurs and for professionals at the top of a mountains it is shy below an arc second.

M24 and Collimation Gone Wrong

M24, Orion Parsec 8300M, 4x10 sec, f/6.3, fl 3048,

12" aperture, luminance filter, 1x1 bin, no auto guide,

no AO, 6/5/2011 1:08 AM EST, Webster, NY
© Billy Vazquez VAO(Vazquez Astronomical Observatory)

Messier 24 is not really a stellar object but a bunch of stars along the spiral arms of the Milky Way that happen to be all bunched up along the line of sight nicely without stuff to block the light coming from them (aka. extinction).  Last night I chose this nice field of stars to test how bad the collimation of my Meade LX200 12" telescope is. And boy is it bad!  

First, you might ask, what is collimation? Well if you click the link you can get all the cool details about it, but in a nutshell it is the proper alignment of all the optics in a telescope.  How do I know my telescope is not correctly collimated?  Well click on the image to the right and see for yourself.  The stars are supposed to be nice round dots.  Instead, M24 stars look like bloated egg shaped, non uniform blobs of light!   That is just not right!

So you may ask, what can I do about it?  I need to collimate (align) the optics of my telescope.  For SCT's there are typically  3 screws in the center of the corrector plate that holds the secondary mirror in place.  These screws need to be adjusted to obtain a nice round star shape when in focus.  So what causes the misalignment?  Vibrations, bumping against the telescope, transporting the telescope, basically any movement of the telescope eventually can throw off the alignment.  Stay tuned to the blog and I will bring you the results of my collimation and hopefully a better image of M24, with more information about how I will fix this issue.

Vignetting, Tracking, SNR, PEC, Polar Alignment and M15?

M15, f/6.3, 1x1 bin, 300mm aperture, 3048 focal length
4x20 sec exposure, Orion Parsec 8300M, 0.9"/pix plate scale
Webster, NY, 6/3/2011 4:00 AM EST, © Billy Vazquez

There is much to learn about operating a telescope for scientific purposes or astrophotography than your typical night under the stars for casual observing. To the right, you see an image taken from VAO (Vazquez Astronomical Observatory) in Webster, NY  on 6/3/2011 at 4:00 AM in the morning.  I used a Meade LX200 12" telescope and Orion Parsec 8300M camera through a luminance filter.  I used MaximDL as the imaging software, binned at 1x1, 4x20 sec exposures, dark substracted, no flats, no auto-guiding.  The images are the raw images stacked, registered and dark substracted with CCDStack. I used GIMP to modify the contrast and brightness of the resulting stacked image.

So what is so special about this image?  Well lots of things!  Lets enumerate some of the things I will talk about on this blog: Polar Alignment, Periodic Error Correction (PEC), Tracking, Signal To Noise Ratio and Vignetting.

First, in order to do accurate and precise imaging a telescope needs to be polar aligned.  You might have heard that this is as simple as to point your telescope at Polaris (North Star) while your telescope is at the polar position.  This is good enough for casual observing as it will give any GOTO mount the ability to point roughly to the area of the sky where your object of interest is.  Unfortunately, Polaris is not exactly at the celestial north pole.  What this means is that for imaging, you need to have your telescope precisely polar aligned.  There are many methods to do this, the most popular is the drift polar align method and the Kochab Clock Method.   I used the drift method, assisted by Pempro Polar Aligned Wizard.   This is by far, the most time/effort consuming task I have ever done for any astronomical endeavor.

Next, Periodic Error Correction (PEC), all mounts are imperfect mechanical machines.  Therefore, there are (in addition to drift from non-precise polar alignment) 2 sources of error while tracking a target.  The first is RA periodic error, or the error of tracking in right ascencion.   This error can be minimized (but never eliminated) by using PEC if your mount provides such a service.  I used Pempro to program my mount to reduce this error.   This is easier to do than polar alignment because of Pempro, but still requires considerable amount of time and patience.  For example, I have reduced my mount RA error from 75 arcsec to 25 arcsec and it took me over 7 hours to do this.   I still need to refine this error to bring it down to the single digits.  Next, DEC periodic error,  this one cannot be eliminated with Pempro.  It is mostly due to 2 things, imprecise polar alignment and mechanical fluctuations like dynamical flexure.  How do I deal with this?  Well I have not yet and it clearly shows in the image.   The image was taking without auto guiding, to see how good or bad the raw tracking of the mount is.  Auto-Guiding and Adaptive Optics should help reduce the error on the declination axis.

Tracking, most GOTO mounts provide Sidereal Tracking, a fancy phrase for tracking stars as they  move across the sky.   The tracking of the raw mount is affected by many things, balance, mechanical imperfections of the gears, flexure and polar alignment to mention a few.  The image above is an unguided exposure.   This means that only the mount was trying to keep up with the movement of the stars across the sky over 20 seconds.  That is why you see star trails and stars that look like ellipses instead of perfect circles.   I was expecting this result, which is why I took the images in the first place.  Considering the quality of the mount, the amount of RA error I still have and the exposure time of 20 seconds this is better than expected.

Signal to Noise ratio, is the ratio of the amount of light from celestial objects in your image vs. the amount of unwanted signal due to electronics of your CCD detector and other noise sources.   I want to increase that ratio and the easiest way to do it is to add up images of the same object.  For my image, I took 4 images of the same duration, 20 seconds.  Then add them up.   This should have incerased the SNR by approximately a factor of 2.  The more images you stack the better your SNR is until you hit diminishing returns.

A great feature of this image is what we call Vignetting.   Vignetting is caused by reducing the amount of light received by the CCD detector along the optical path.   Basically, it is a shadow.  You can see that the center of the image is brighter than the edges.  How should I deal with this?   Easy,  taking flat exposures.   Flats are images taken against an uniform light background.  These images are stacked, combined and dark reduced to create an image that shows the lighting imperfections of the optics in your telescope setup.  I did not do it for this image to see the effect. 

And last M15.  Why did I choose M15?  Well the honest truth is that it was 4:00 AM in the morning after a long night of trying to correct PEC and I wanted to see how good my polar alignment was, so I decided to do a few slews (moving the telescope from one point to another) to check my pointing accuracy.  M15 was about 50 degrees East of my last position on the PEC run so I said... "Hey why not?"   One slew later... I took a 5 second exposure and... BAM!  M15 was right there.  Not centered by any means, which means I will need to use TPoint at some point to start correcting the pointing precision. But nonetheless, within 14 arcmin from the center of my field of view.

Pluto a planet's discovery story

Courtesy of Astro Leo's planets

Pluto's discovery story is not only an important part of Astronomy's history, it is also part of American history. It all started with Uranus, the 7th planet. In the early 1840's French mathematician Urbain Le Verrier predicted that there should be another celestial body perturbing the orbit of planet Uranus. The story of the discovery of Neptune then confirmed this prediction from Le Verrier. Further observations of Uranus later in the 19th century led to the speculation of yet another celestial body still perturbing Uranus.  Therefore in 1906, Percival Lowell from Boston Massachusetts, started a project in search for the 9th planet from the Lowell Observatory in Flagstaff, Arizona.  Lowell died without knowing that the observatory had imaged Pluto but had failed to recognize it.

The search for Pluto was put into hiatus until 1929, when Clyde Tombaugh a natural from Kansas, working at the Lowell Observatory finally found a moving object in photographic plates between the nights of Januray 23rd and Janurary 29th, 1930.  The results were sent to the Harvard Observatory on March 13, 1930 after confirming with a third exposure made before in January 21st.  The name's that went up for vote were Minerva, Cronus and Pluto.   Pluto received every vote!



The Expanded Very Large Array



EVLA image of supernova G55.7+3.4
Bhatmagar et al.

The electromagnetic spectrum is the realm of astronomers. From high energetic X-Ray photons to the the long wavelength radio photons. So how do we detect these radio photons? The answer is: radio telescopes. Why are they called telescopes anyways? Well, they let us "see" into the universe at frequencies where our eyes can't see. But more impressive, we can take pictures of the night sky so that we can see what our eyes couldn't otherwise. Radio telescopes have been around for a long time now. The largest single dish Radio telescope in the world is in Arecibo, Puerto Rico. If you have ever seen the movie "Contact", then you have seen this excellent facility. Another entertaining sci-fi movie is "The Arrival". On this movie we see a telescope facility of 27 white dishes. These dishes are the famous Very Large Array telescope in New Mexico.

The Very Large Array has recently been beefed up and renamed the EVLA or Expanded Very Large Array.  The image above is supernova G55.7+3.4, the remnant of a star that blew up to smithereens. The filamentation seen on this radio image was not visible until the EVLA was upgraded to be 10 times more sensitive that in the past.   So what was changed in VLA?  Well it was pretty much gutted out of the 1970's electronics and added new 2000 tech to it.   This new and improved electronics makes the VLA so much more sensitive than before.  So why the image of a supernova remnant?  Can't we already see these objects in the sky?   Sure we can!  But not like this.   Imagine that you are watching your favorite movie on your old TV without high definition.   Now erase that memory and imagine your favorite movie in HD (high definition).   The difference is like night and day!  That is a good analogy to the new revamped EVLA.  We will be able to see fainter and deeper into our galaxy and detect until now unseen objects and reveal new details on existing ones.

SETI goes Kepler

Courtesy of NASA/Ames Research Center

The search for extraterrestrial intelligence (SETI) is one of the outstanding questions on the minds of many.   Needless, to say, this stems from a need to know if we are alone in the Universe.  SETI is focusing its search on the recent data release from the Kepler Space Telescope.   SETI has selected 86 planets from the the 1235 released by Kepler.   Why only 86?  Well, the main reason for this is that they want planets that can sustain water in liquid form.  Many of the planets detected by Kepler, so far, are giant gaseous roasters.

The search will be performed with the Green Bank Radio Telescope in West Virginia.   This facility can  record over 60 terabytes of data per day of observations in the range between the 21 cm hydrogen line and the 18 cm hydroxyl line.  Why between these 2 lines?  Well, to begin with this region on the radio is rather quite in the Universe and it is not absorbed by anything that we know of.  And second, SETI scientists believe that an intelligent civilization that depends on water will broadcast signals in this region dubbed, the "water hole" region.

The question remains, will we find intelligent life via radio waves?   Well, the answer is really out there, according with extrapolations from the Kepler observations, we could easily find about 50 billion planets in the Milky Way.  That is a huge number of planets.  Perhaps ET is in one of them!

Stars Delivered in 10 seconds a lesson in Magnitude

Welcome back to another astronomy blog after a long week.   On the right there is an image of the sky taken with my SCT 12" telescope and my main CCD camera. The exposure was 10 seconds long in the neighborhood of the North Star, Polaris.   The first feature I would like to point out on this image is the light bleeding out from Polaris into the image.   Even though Polaris itself is not on the image you can still see the light streaking out from the left side of the image.  This is because Polaris has an apparent magnitude of 1.97.  That means that it is a very bright star. For comparison, a full Moon has an apparent magnitude of -12.7.   The more negative the magnitude the brighter the object is.

The image is also inverted in color space.  What this means is that the black dots are the stars.  It is sometimes easier to see them this way.  Now lets talk about the stars on the image.  The brightest of them is the one that look the largest on the image, slightly right off center.  This is HR 286 a 6.47 apparent magnitude main sequence star.  Now, try this out, find the dimmest star on the image.  There are several very dim stars on this image.   Their apparent magnitude is around 14.

But what does this apparent magnitude means?  It means that a star of 0 magnitude is 100 times brighter than a star of 6th magnitude.   In our previous example HR 286 is approximately 1000 times brighter than the dimmest star in the image.   That is a LOT brighter!