Sunday, April 15, 2018

Cosmic Ray Strikes are Real!




Single image of M57 with Unusual Object at 5:00 Position

Earlier this year, I set up my scope for planetary imaging. Sadly, the only planet in our winter skies was faint Uranus.  Undaunted, I slewed the scope to a bright “planetary” nebula. Recently, I revisited this imaging set to find a surprise.

2018 promises to be a banner year for those of us who love to observe The Solar System. Soon, a planet parade will begin as Jupiter, Mars and Saturn appear in the east while Venus pushes herself away from solar glare in the west. Wishing to hone my planetary imaging skills, I set up my scope and ZWO ASI224MC planetary camera on a clear albeit cold evening. The icy weather and lackluster skies had kept me indoors throughout the winter. Over my shoulder, I felt Orion mocking me as I fumbled in the icy semi-darkness to get my observing session started.

As I slewed the scope to Uranus, the sole planet above the horizon, I found it obscured by my house. My scope weighs 300lbs. There was no way that I was going to move this massive behemoth on such a cold night just to image Uranus' tiny featureless disk. Looking up, I realized that M57, The Ring Nebula, stood high in the western sky.  If the planets refused to cooperate, perhaps a bright planetary nebula would be a suitable alternative.

I used the famous “Double-Double Star” (Epsilon Lyra) to tweak my focus. As these four stars danced around the field, I realized the inferiority of the night’s seeing. With the Jet Stream and its 140 mile-per-hour winds locked above Maryland throughout the winter, turbulence has destroyed our seeing. This night was no exception, and I quickly lost my enthusiasm for imaging.

Nevertheless, I dutifully centered The Ring Nebula on the chip and snapped 25 15-second images of the famous planetary nebula. The muted spectrum of color of The Ring looked like a rainbow reflected in a choppy swimming pool. Disappointed, I packed up my telescope's freezing metallic surfaces and forgot about the images. Why does the weather always seem colder when breaking down your equipment?


 


Weeks later, while organizing my images, I chanced upon the M57 data set. Upon closer inspections, the images seemed decent enough to process. Now, I would never send these images to Sky and Telescope for publishing. However, I hoped something could be salvageable. I might even get a column for the newly-born blog.


While manually inspecting each image, I noticed a surprising linear feature on the 24th image of the set. All astrophotogrphers are accustom to the bright lines of artificial satellites bisecting our best images. Consequently, I assumed some wayward piece of space junk invaded my photography session, marked the image as unusable and moved on to the next image.


M57 - Single 15 sec. Exposure - Meade LX-850
Surprisingly, the next image in the set did not contain the trail of the satellite. I shuttered these images simultaneously with no time between successive images. The slow-moving satellite should be apparent on the next frame, A quick estimate placed the length of the track as eight arcsecs and approximately 10th magnitude. Our moon travels through the sky at .5 arcsecs per second, so this object moved through the sky at approximately the same speed as the moon and must be approximately the same distance. Moreover, geostationary satellites at 1/10th the distance of the moon rarely achieve 10th magnitude. Therefore, this object must be huge – like alien space station huge.

M57 - Single 15 sec. Exposure - Meade LX-850


Perhaps I should have contacted Fox News to tell them that I had just discovered a giant alien mothership in an inclined orbit a quarter of a million miles away from the earth. I am sure they would be interested. After all, I had photographic proof.

Instead, I looked for alternative answers.

Cosmic rays are highly energetic particles originating from high energy events mostly outside of the solar system. They wreak havoc on spacecraft by literally changing the contents of computer memory or marring imaging. When they collide with the earth’s atmosphere, they cause a cascade of secondary charged particles that rain down upon the surface.

Cosmic Ray Strikes observed from the surface of Mars by The Opportunity Rover. The parallel lines are star trails while other linear features are cosmic ray strikes. - Credit NASA/JPL.

The most probably cause of my rogue satellite trail is a cosmic ray. That night, a cosmic ray entered our atmosphere. Its fast speed and high energy knocked electrons off the atoms in several pixels of my detector as it skipped across my CCD. The software assumed that everyday photons were affecting the electrons in the CCD and dutifully reported a bright object in that part of the sky.

Ironically, I began the evening in hopes of photographing a nearby planet. Having acquiesced to imaging a dying star system 2,000 light years away, I ended up capturing what possibly is a piece of galaxy that existed long ago and very far away.

By the way, here is the processed result of the imaging session:


Keep Looking up to Clear Skies.

Saturday, March 10, 2018

Looking for one Satellite - Finding Many



One of the great things about astrophotography is the ability to revisit old datasets. As we acquire new skills and new processing software, we sometimes discover thing in images we discarded months or even years ago. Not a fan of imaging in sub-zero (Celsius) temperatures, I have used the past few weeks to look for interesting discoveries in last year’s images. Astrophotography is, in many ways, the gift that keeps on giving.

Nearly a year ago, Jupiter’s faint inner moon, Thebe was going to pass its greatest elongation from Jupiter between its brighter moons Europa and Callisto. Moreover, Jupiter ‘s impending opposition promised to brighten Thebe to maximum detectability. Always a fan of a Solar System challenge, I planned accordingly.

As on many early spring evenings, the wind blew furiously on the night of March 29. Undaunted, I set up in my driveway and began imaging Jupiter. My plan was to capture 30 subs in each of four different exposures later stacking them to hopefully bring out the faint moonlet from the glare of Jupiter.

Almost immediately, a streak of light crossing the computer screen caught my attention. Clearly, an Earth-orbiting satellite strayed into the telescope’s field of view. I noted the curiosity and begin my imaging sequence.

As I images, Jupiter and its moons wiggled all over the screen.  Not only was the night windy, the seeing could not have been worse. 

Soon, another satellite crossed the field of view. Happily, I captured this apparition as I was actively imaging at the time. 


During my imaging routine, seven satellites crossed the field. I captured two of them. Each crossed at the same speed with the same angle. While the cluster of artificial satellites and space debris occupy random orbits and inclinations, these seven satellites seem to follow the same routine, What could they be?

Jupiter’s declination at the time of this observation was -06°01'30".  Not surprisingly, the belt of geostationary satellites appears at approximately -6° from our location 39.5° above the equator. Serendipitously, I happened to image Jupiter during the two hours it crossed this belt. Things never work out that well for me.

Recently, I used Photoshop to create a little animated .GIF of the sequence. I was forced to overexpose Jupiter in order to make the much fainter artificial satellites more visible.


If you want to try to image geostationary satellites, Sky and Telescope published a great article detailing “How to See and Photograph Geosynchronous Satellites."

If you wish to duplicate my observations, Jupiter should re-cross the band on March  14, 2022.

Keep Looking Up to Clear Skies.

Ken

Monday, February 12, 2018

Trials and Tribulations of Near-Earth Asteroid Hunting



Last Sunday Evening, while most Americans settled back to watch the 52nd Super Bowl, the earth entertained a celestial visitor. A 2,000-feet wide asteroid named “276033 (2002 AJ129)” silently passed within 2.6 million miles of the earth briefly becoming the second nearest knows celestial body and, brightening to 12th magnitude, shone as one of the brighter asteroids in our sky. 


I had awaited this event for months. The website Spaceweather routinely lists upcoming Earth-asteroid encounters. Whenever a relatively large object is mentioned, I take note.  

Recent list of Near Earth Objects from Spaceweather.com

Clicking on the object name takes the user to one of my favorite tools, the “JPL Small-Body Database Browser.”  There, a few clicks get the user a very accurate ephemeris. The asteroid was going to be conveniently placed in our evening sky. Moreover, the predicted maximum brightness was a glaring 12.3 magnitude. Surely, this would be an easy catch.

JPL Horizons Ephemeris for Asteroid 2002 AJ129

Sadly, I was scheduled to work on the evening of the 4th. However, 276033 (2002 AJ129) follows a highly-eccentric orbit. It approached the earth from the direction of the sun. Consequently, at closest approach, its tiny crescent disk shone a full magnitude fainter than the next evening when its full disk receded from our neighborhood. Therefore, I planned my observations for the night of February 5th.
 
Astronomy Now view of 2002 AJ129's Orbit
Catching these objects is like a skeet shoot. They move quickly through our skies. So, I use the wonderful JPL Small-Body Database Browser to predict the position of the asteroid at various times and plan to point my telescope at the predicted star fields at those times and wait for the asteroid to pass.


The night is brutally cold. But it is February, and I have only observed once this year. Other club members actually draw their observations through mittened fingers. I certainly can get out there and create material for a new blog posting. So, I wrap myself in layers of Kevlar and Gore Tex, fill my Thermos with hot tea (Earl Grey) and set up my scope.  At least the heavy lifting momentarily warms my muscles. 


Tonight, the asteroid travels among the stars of southern Leo. At 9:30pm, the starfield finally rises above my neighbor’s’ home. I type the coordinates into the keypad of the mount and the telescope dutifully slews to a position on the Leo-Sextants border.
 

Surprisingly, the first images do not show the predicted starfield. In fact, the first images show no stars at all. I can see the familiar “Backwards Question Mark” of Leo and the nondescript stars of Sextants so, clouds aren’t obstructing my view. Reluctantly, I leave the warm perch of my seat to look through the finder scope. Just where is the scope pointing?  Stars look good through the finder. It takes my frozen mind a few minutes to determine the issue. Although the finder points above my neighbor’s roof, the main scope’s physical position is well below the finder. While the finder and optical tube are perfectly aligned on distant stars, they point in radically different directions in the near-field. The scope still points toward my neighbor’s house. My first image isn’t of the asteroid or anything farther than 100 feet. It is of a highly out of focus three-inch-by-five-inch portion of someone’s roofing!

First Attempt at Imaging Asteroid 2002 AJ129 - a 3X5-inch Portion of my Neighbor's Roof.

The 9:45pm attempt fails as well. I image with a solid-state laptop. This means the computer has no hard-drive-- no moving parts. Hard drives do not work well in colder weather. The lubricant needed to whirl their disk drives thickens at colder temperatures creating all kinds of disk read errors and other scary messages. Solid state computers do not suffer these issues.


Tonight, I discover that my laptop fails below 15°F. I still do not understand why the computer struggles in these cold temperatures. I thought that electricity flowed better in colder temperatures. Although the solution is simple, I burn through another 30 minutes of observing time getting a heating pad to place beneath the laptop. At least I now get a nice place to warm my numb fingers.


By 10:30PM, the starfield hangs well above the neighbor’s roof and the laptop computer, warmed by the heating pad, runs well. The telescope slews to the predicted starfield, and I watch the preview images display on the screen. The starfield appears as predicted, but no asteroid. I wait as each 20-seconds a new exposure appears on the screen. Eventually, I notice that one of the stars near the leftmost portion of the field does not appear as a point. Instead, it presents itself as a small line. Moreover, like and inchworm, it moves slowly toward the top of the screen.  I found it! Although it is not exactly where I predicted it to be, Asteroid 276033 (2002 AJ129) is in my camera’s field of view and images are being captured every 20-seconds.

Animation of Six 20- Second Exposures of Asteroid 2002 AJ129

Predicted Path of Asteroid 2002 AJ129


Predicting the progression of the asteroid, I immediately reposition the scope.  I want a series of images with the asteroid passing through the center of the field. When I see the asteroid appear in the bottom of the new star field, I begin capturing a new set of 20-second exposures. Figuring that it would take seven minutes for the asteroid to disappear from the camera’s field, I scurry indoors to warm myself by the fire.

Animation of Eleven 20-Second Exposure of Asteroid 2002 AJ129

Afterwards, I capture a few longer exposures and shiver as I break down my setup. Hastily, I adjourn to the warm of my home to download the images forgetting to acquire dark or flat frames. 


So, what can I do with this data set? I first create a little movie. I use Photoshop Elements 10 to create a stack of 15 layers. Each layer represents one 20-second exposure. Afterwards, I “Save For Web.,” I select “animate.”  This creates a “.gif” animations that may be uploaded to things like Facebook or Astrophotography Blogs. My lack of flat fields leaves the animation heavily vignetted. 

Enhanced Animation of Asteroid 2002 AJ129



I can also use Deep Sky Stacker, to stack the images.  This makes 2002 AJ129 appear to be a series of streaks running through the frame. The horrible vignetting and doughnut-like dust circles embarrassingly emphasize my lack of flat field images. 

Stack of Fifteen 20-Second Exposures of Asteroid 2002 AJ129

If you regret missing 2002 AJ129’s passage, there are other events in the near future. On 7 March 2018, a smaller asteroid 2017 VR12 passes less that one-million miles from the earth. At a predicted magnitude 11.8, it will be a fast-moving late-night object quickly threading its way between the galaxies in Virgo. I will be out there, and I promise, I will not forget to take my dark and flat frames.


Keep Looking up to Clear Skies


Ken

Cosmic Ray Strikes are Real!

Single image of M57 with Unusual Object at 5:00 Position Earlier this year, I set up my scope for planetary imaging. Sadly, ...