Friday, June 24, 2011

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!

video

Friday, June 17, 2011

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.

Wednesday, June 15, 2011

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.
video
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.  

Tuesday, June 14, 2011

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

Monday, June 13, 2011

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.


Tuesday, June 7, 2011

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.

Saturday, June 4, 2011

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.