Aug 282011
 

The supernova in the Pinwheel Galaxy (M101) has now been designated “SN2011FE” (formerly “PTF11kly” which was even more difficult to remember). It continues to brighten. Comparing my measurements over the past two nights, it has brightened half a magnitude, from 12.9 to 12.4 in the past 24 hours. This is consistent with observations submitted by others to the AAVSO:

SN2011FE light curveThe total exposure time for the image below was 50 minutes. It shows a bit more detail of the Pinwheel Galaxy than the image taken the previous night (5 minutes).

SN2011FE V combined

Aug 272011
 

Last Tuesday, August 23rd, a new supernova was discovered by researchers connected to the University of California, Berkeley. Designated SN2011FE, the supernova was observed exceptionally early in its process of explosion. Scientists predict that SN2011FE will grow in brightness over the next couple of weeks, possibly becoming bright enough to observe with binoculars. Located in the Pinwheel Galaxy (M101) near the handle of the Big Dipper, the “new star” is 21 million light years away, meaning that it actually exploded 21 million years before last Tuesday! Supernovas of this type (Ia) result from binary star systems that eventually evolve into a white dwarf and another star that feeds matter into the white dwarf. Suddenly, a substantial fraction of the matter undergoes nuclear fusion, causing material to be expelled at about 3% the speed of light. For a few days or weeks, the brightness of the supernova can exceed the total brightness of the galaxy in which it resides.

Last night, I captured some images of the Pinwheel Galaxy. By comparing my images with an archival DSS (Digital Sky Survey) image, I could easily see the supernova. Here is the archival image, with two comparison stars, 138 and 140 labeled:

Pinwheel Galaxy, M101

 

 

 

 

 

 

 

 

 

 

 

Below is the photo I took last night, with the same two comparison stars identified:

M101 with SN2011FE

 

 

 

 

 

 

 

 

 

 

 

The two comparison stars, 138 and 140 are in our own Milky Way Galaxy, probably no more that 5,000 light years away. Supernova, by contrast lies in the Pinwheel Galaxy, 21 million light years away. So even though it looks roughly comparable in brightness to 138 and 140, it is actually many millions of times brighter.

I submitted my measurements to the American Association of Variable Star observers (AAVSO), which are shared with others to produce the light curve:

SN2011FE supernova light curve

 

 

 

 

 

 

 

 

 

 

 

 

 

 

If we continue to have clear skies for a few days, I plan on checking on the supernova each night as it grows in brightness.

Jul 282011
 

Vesta is one of the brightest asteroids, easily visible in a pair of binoculars. On July 16, NASA’s Dawn spacecraft went into orbit around Vesta and began sending close-up images.

Last night, I searched for Vesta, which was low in the south, at an altitude of about 20 deg, between some Douglas fir trees. If it hadn’t been for the tree cutting of some red alders for firewood last year, I wouldn’t have been able to catch Vesta at all. It was predicted to reach its highest point in the sky at 2:10 am this morning, so I decided to start imaging then.

Using the planetarium program, TheSky6 to find it, I thought I knew where to look. But alas, it wasn’t where the program said it would be! Then it dawned on me that maybe I needed to update the orbital parameters for the asteroid, as there must be better numbers available now than there were when I first installed the program. I then found the personal website of Marc A. Murison which includes a calculator of asteroid orbital parameters.

Just what I needed! Putting the new numbers into Vesta asteroid data of TheSky did the trick. The telescope went directly to the target. But it was still behind the trees, so I had to wait about half an hour. Fortunately I had Mr. Murison’s blog to read, which has some great political commentary and kept me awake.

I then started a sequence of images (10s exposure, clear filter, ST-8 camera, Takahashi FSQ-106 telescope) and went to bed for a couple of hours.

When I got up to check my images and close down the observatory, I discovered that there were about 40 minutes of good images, unblocked by trees. So I put together the following animation, in which successive frames were about a minute apart.

 Asteroid Vesta on July 28, 2011

In just 40 minutes, you can clearly see the asteroid moving relative to the background of stars.

Jul 062011
 

South Whidbey teacher, Heather Dubendorf has brought her students up to the observatory on several occasions. Tonight she brought her husband, son and daughter. We were joined by our friend Josephine and her two grandchildren. We had a good view of the waxing crescent moon at a magnification of 136x, where the disk of the moon just about filled the field of view. With the moon only about 12 degrees above the horizon, we were looking through over 4 ½ times as much air as we would if it were directly overhead. That resulted in quite a bit of wavy shimmering of the image.  We could see Saturn with its rings. Its largest moon Titan was easily visible but other moons were lost in the atmospheric turbulence. We aimed the telescope at Albireo, the head of the swan in constellation Cygnus and could clearly see the different colors of the two stars making up this binary system.

Observatory at sunset

Observatory at sunset

Visitors to the observatory

Visitors to the observatory

Jun 082011
 

I had never seen Pluto before, so in the back of my mind, I have had the inclination to try it sometime. Then I saw an article in the July issue of Sky & Telescope magazine, where Tony Flanders writes,

Every year like clockwork, editors of Sky & Telescope debate whether to print a finder chart for Pluto. For the last few years the decision has always been “Okay, but this is the last time. We won’t run it next year — no way!”

When the forecast called for clear skies for the next two days, I thought, Here’s my chance!

After the discovery of many other small and distant objects in our solar system, a new classification system was presented by the International Astronomical Union. According to the new system, Pluto was re-classified as a “dwarf planet,” along with Ceres, Haumea, Makemake and Eris. The number of “planets” in the solar system was reduced to eight.

Pluto is currently passing through a dense field of stars in Sagittarius– an area of the sky near the plane of the Milky Way galaxy. This means that Pluto, currently at magnitude 14 is difficult to distinguish from the thousands of nearby stars of equal or greater brightness. From day to day, Pluto appears to move against the background of stars, so the best way to be sure one is looking at Pluto is to compare where it is on at least two successive days.

My plan was to take two images of the star field where I expected Pluto to be on June 4-5. Using my planetarium program, TheSky, I determined that shortly after 3:00 am Pluto would be positioned at an altitude of 23° and in between trees to the south of the observatory. I planned to use my ST-8XME camera attached to my Takahashi FSQ-106 telescope at f/8. The star field generated by TheSky for this arrangement is shown here, with my field of view outlined by the red rectangle.

Field of view for Pluto, generated by TheSky planetarium program

Here is first image taken through the telescope in the early morning of June 4, 2011 at 3:44 am.

Pluto June 4, 2011

Now the trick was to relate stars in the image with “stars” displayed by the planetarium program, in order to locate Pluto. My best guess is shown below, indicated by red tick marks:

Is this Pluto?

Is this Pluto? The only way to find out for sure is to wait a day and take another image of the same star field.

On the morning of June 5 at 3:10 am, I took a second image of the same region of sky.

Pluto June 5, 2011

Comparing images for June 4 and June 5, can you identify which speck has moved??

Neither could I.

However, using the Blink Comparator feature of CCDSoft, it is possible to see the difference between the two images. Here is the result, shown as an animation of the two frames:Animation of Pluto in star field June 4 and June 5, 2011

Now can you spot Pluto? It’s the dot that moves a bit near the center of the frame.

So my first guess was wrong as to which dot was Pluto– it actually was the smaller, dimmer one of the pair.

The other tiny specks that appear in one frame but not another are probably due to random cosmic rays hitting the imaging chip during the exposure.

May 022011
 

On April 29, 2011, a star of magnitude 10.3 in the constellation Cancer was predicted to be occulted by 253 km (157 mi) diameter asteroid known as “(7) Iris”. The eclipse path did not include the Tinyblue Observatory, but due to the uncertainty in the orbit of the asteroid, there was a possibility that the eclipse would be observed here. the sky was cloudy throughout the day, but the clouds started breaking up around 8:00 pm.

Upon Cynthia’s advice, I hastily set up the telescope and turned on the CCD camera, then opened the observatory dome and began to calculate exactly when I needed to start the exposure, when I needed to stop the mount tracking (so that the stars, including the target star, would leave trails on the image frame during the predicted eclipse event, and how long the exposure should be, to take into account the uncertainty of the event but without over-exposing the frame.

Due to some residual moisture inside my CCD camera, soon after the cooling mechanism was turned on, a layer of ice formed on the CCD image chip. This would have made imaging impossible. However, if one waits long enough, frost gradually clears from the chip on its own. Unfortunately, I only had about 20 minutes before the forecast eclipse and I still had to focus the telescope.

At 9:05, I was able to focus the scope using a mag 1.93 star nearby, then slewed the scope to the target star, TYC 0808-00566-1.

At 9:28:00 pm (according to my GPS timing device), I began a 130s exposure. Then at 9:28:30 pm. I stopped the mount tracking. The exposure ended at 9:30:10 pm.

The image below shows the star trails, with the target star indicated with tick marks. Note that there is no gap in the trail of the target star, indicating that the our location was not within the eclipse path. While not as critical as a “positive” observation in which a short blockage of starlight is observed, my observation, a “negative” observation also has some value as it narrows the range of uncertainty in the path of the eclipse. Compare this with an example of a positive observation.

In the image below, note that the large oval region is the area that has become frost free in the short time since the frame was completely covered with frost.

Jun 122010
 

In an attempt to find out whether it was possible at the Tinyblue Observatory to detect extra-solar planets (exoplanets), I started with one of the easiest ones, a star in the constellation of Vulpecula designated HD189733. In 2005, French astronomers discovered a planet the size of Jupiter “transiting,” or passing across the face of this star. The star, nearly 63 light-years away is just slightly smaller than our sun. The orbital period of the planet, designated HD189733b is 2.2 days.

The star is relatively bright at magnitude 7.67 and its apparent brightness drops by 0.028 mag, or about 0.4% during the transit of the planet. The duration of the transit, from when the planet first starts to move across the face of the star, to when it leaves is 109.6 minutes.

These characteristics suggested that I would have a good chance of observing the dip in brightness during a single night of observation if I happened to have a clear night on which a transit would begin in the evening after dark. Fortunately, the Exoplanet Transit Database website provided the necessary forecast:

 

It was in a good position in the sky for viewing from midnight until 4:00am on Saturday. I set up the telescope to track the star and had the camera take 30-second exposures continuously through the night. The exoplanet is about 13% larger than Jupiter, but much closer to its parent star. It revolves around the star in only 52.8 hours!

The fact that is about 62.9 light-years from Earth means that the light I was recording had been emitted from the star right around the day I was born in 1947. Auspicious, perhaps?

Details of the observation program are described in the Tinyblue Observing Plan 2010-06-11. In a reference frame of the surrounding star field, the program star is identified as V and several comparison stars C1, C2, etc are indicated. Accurate magnitudes of the comparison stars have been published and can be used as reference to determine the magnitude of the program star.

A light curve for the transit event clearly demonstrates the dimming of star HD 189733 as light is blocked by exoplanet HD 189733b.

Light curve for transit of HD189733b

During the night, we acquired 328 images of the star. The images were “reduced” (cleaned up using special reference frames) and the star magnitudes measured using photometric software. Results were compiled in an Excel spreadsheet, HD189733b_Multi-Image Photometry_ExtraDecimals and a graph of magnitude vs. time was generated.

Click for a full-size version of the Light Curve of HD189733

In the graph of our results, the rapid fluctuations are due to random effects in the atmosphere and in the measurement equipment. But ignoring this “noise” in the signal, it is still clear that there is a definite drop in brightness of about 0.03 magnitude or 0.4%.

More information about the exoplanet is at http://en.wikipedia.org/wiki/HD_189733_b

Oct 282008
 

Around midnight on October 26, 2008, a 51km asteroid known as (270) Anahita occulted a 10.5 magnitude star in the constellation Gemini for observers along a path across western Canada and Northwest USA, blocking starlight for a little over 10 seconds. This image, taken using a “drift scan” technique shows a gap in the star trail of the target star (indicated by tick marks). The star’s identification is TYC 1880-01064-1.

Drift scan image of star occultation by asteroid Anahita

Oct 252008
 
Andromeda Galaxy, M31

Andromeda Galaxy, M31

Light from the Andromeda Galaxy reaches us after traveling for 2.5 million years. This Galaxy is a spiral galaxy like our own Milky Way, but larger. It contains roughly a trillion stars or about three times as many as in the Milky Way. Almost all of the stars you see in this photograph as pinpoints of light are stars in the Milky Way, a few tens of thousands of light years away. The stars in the Andromeda Galaxy are so far away that their light appears to merge as fuzzy regions of brightness in this photo. Other telescopes can make out individual stars in the Andromeda Galaxy.

This image was created as a mosaic of three overlapping images. Exposures were taken through four filters: Clear, Red, Green and Blue using an SBIG ST-8XME camera attached to a Takahashi FSQ-106 refractor telescope at f/5 over the course of two nights: October 18 and 25, 2008. Total accumulated exposure times were: Clear (3.75 min), Red (4.2 min), Green (4.2 min), Blue (6.7 min).