Tuesday, May 24, 2016

Rain and Sun

Rainbow and Sunspots

Sunlight is rare these wet days in Williamsburg. My lawn has never been greener. Although clouds and rain make solar observing impossible, occasionally, the Sun does break through. Late in the day on May 14th an amazing intense rainbow appeared behind my house. Unfortunately, the 6-panel mosaic below failed to capture the very top of the secondary rainbow. I wish I had raised the camera a bit higher! (Click on the image for a larger view.)
The primary rainbow is very bright and shows up nicely against dark background clouds. The higher secondary rainbow is dimmer with colors arrayed in opposite order compared to the primary rainbow. Inside the primary rainbow supernumerary bands are seen, particularly near the top of the arch. View the enlarged image to see the supernumerary bands more clearly. This is the best rainbow I've ever seen!

Two days after the rainbow's appearance the sky finally cleared for several hours. Viewing conditions were nearly ideal with gentle puffs of wind and temperatures in the mid to upper 60's. Seeing was good as I began solar imaging at about 2:00 pm EDT.

The Sun finally showed a few significant features which are displayed in the following 40-panel mosaic made with a 5X Barlow lens. On the left, large sunspot 2546 is located near an accompanying white active area. On the right is smaller sunspot 2544 with its own active area. The large prominence on the upper left limb was particularly bright in the eyepiece. (Click on the image for a larger view.)
The previous image has been reduced to one third of its original size. The full-sized image is a 13.4 MB monster measuring an amazing 6849 by 6411 pixels! This is nearly the best full disc mosaic I've ever made. It took many hours to construct and enhance the picture.

The next picture shows a closer view of large sunspot 2546. Good seeing allowed resolution of fine details around the sunspot and on the limb.
Smaller sunspot 2544 had an interesting umbra structure.
Finally, here's a closer view of the brightest prominence on the northeastern limb.
Soon after the nice clear sky on May 16th clouds and rain returned. I'm glad I made the most of such a pleasant observing day. 

Monday, May 16, 2016

Mercury Transit

Battling Clouds

Mercury lines up in front of the Sun every 115.9 days as seen from Earth. During these alignments Mercury is usually above or below the Sun, but, sometimes, Mercury transits directly across the face of the Sun as it did on May 9th. There are 13 or 14 Mercury transits per century compared to only two for Venus. I've been lucky enough to see both Venus transits in 2004 and 2012, but I'm running out of time for transit observing. There will be no Venus transits for the remainder of my life. Although another Mercury transit will happen in 2019, I could be taking a dirt nap before the next transit occurs in 2032! So I was motivated to make extra effort to observe the May 9th transit.

One day before, on May 8th, I checked my equipment to see if everything was working properly. After confirming all was well, in spite of many clouds, I hastily captured one image of sunspot 2542 with nearby filaments. There was no time to take a flat field, so there are subtle vertical bands in this image. The Sun was finally showing remarkable surface features after many bland months. It would have been nice to take more images, but increasing clouds prevented this.
I was excited about transit day because, for once, my observing site was a favored location. The entire transit would be visible for 7.5 hours from 7:12 am to 2:42 pm EDT. All I needed was a clear day! Unfortunately, Williamsburg was in the midst of a long stretch of cloudy rainy weather, and May 9th was destined to be mostly cloudy. Nevertheless, I rose at 5:00 am, set up my equipment at dawn, and was ready to take advantage of any small bit of clear sky by 7:00 am. Temperature near dawn was a chilly 53 degrees, but rose rapidly in the next few hours.

The Sun broke through a cloud gap as the transit began. I hoped to capture Mercury's black disc crossing either a prominence or spicules on the Sun's eastern limb. Hopes were dashed because seeing was absolutely horrible with the Sun close to the horizon barely an hour after sunrise. I could clearly see Mercury crossing spicules very near a small prominence, but the solar limb was swimming around in a blurry mess. The first image below shows Mercury just crossing the limb at 7:15 am. The dreadful lack of detail in this image is caused by extremely unsteady air.
More than an hour later the Sun had risen higher and seeing improved. I patiently waited for an opening in the clouds and captured the next image through haze at 8:41 am. The small prominence in the upper left is where Mercury earlier entered the solar limb. It would have been great to capture Mercury's black disc silhouetted against this prominence, but, as I mentioned before, roiling air made this impossible.
The angular diameter of Mercury's disc was only 12 arc seconds, about one fifth the size of Venus' disc when Venus transits. Twelve arc seconds is 1/300th of a degree! Thirty minutes later I captured one last transit image at 9:21 am showing another prominence lower down on the rim.
Seeing conditions improved as time went on, but clouds thickened. I managed to capture two more images through thin clouds to make the following 2-panel mosaic of sunspot 2542 near the transit action.
Soon the temperature had risen to 77 degrees. By 10:00 am the sky was 90 percent cloudy and getting worse. Satellite images showed no prospect of future clearing, so I decided to quit at 11:45 am. Maybe conditions will be better for the next transit in 2019.    

Sunday, May 8, 2016

New ZWO ASI120MC-S Camera

Jupiter In Color

On the evening of April 16th, after a full morning and afternoon of solar imaging, the sky remained completely clear. I returned to my telescope in twilight as the temperature dropped rapidly. Moonlight was bright, but Jupiter was high in the sky and well positioned for imaging. I was anxious to try a new ZWO ASI120MC-S USB 3.0 color camera on Jupiter.

I began capturing Jupiter with a 5X Barlow lens on my 130mm Stellarvue refractor. Seeing was not bad, so I expected better results than I got in the first image below. This image was made by stacking the best 100 frames from a 3,000-frame video. Jupiter's moon, Io, is in the lower right. The image is disappointing because it doesn't show fine detail like swirls in the Jovian cloud bands. Maybe I haven't yet mastered the processing skills to reveal small details. Or, maybe the inherent resolution of my telescope-camera combination isn't sufficient to capture the missing detail. I'll investigate these possibilities in the future.
Next, I tried less magnification. Jupiter is smaller in the next image made with a 3X Barlow lens. In this wider field of view the Jovian moon, Europa, is now visible to the upper left. Fine detail seems better in this image produced by stacking the best 100 frames of a 2,000-frame video.
My final capture of Jupiter was made with a 2X Barlow lens. Now the field of view widens even more to include a third moon, Ganymede, in the far upper left. (The fourth Galilean moon, Callisto, was far out of the field of view to the lower right.)
The image made with the 3X Barlow seems the most pleasing. Maybe it's the closest fit to the imaging system's inherent resolving power. I've ordered a 4X Barlow to see if it better hits the imaging sweet spot.

After completing trial and error experiments with Jupiter, I installed the 5X Barlow with my monochrome ZWO ASI174MM camera and constructed a 30-panel mosaic of the waxing gibbous Moon three days past first quarter. The area near the terminator showed lots of good detail as you can see in the following half-sized image. (Click on the image for a larger view.)
Just a bit of color has been added to the previous image to enhance the view. I'm looking forward to more planetary imaging with the new color camera. 

People say I'm crazy doing what I'm doing
Well they give me all kinds of warnings to save me from ruin
When I say that I'm o.k. well they look at me kind of strange
Surely you're not happy now you no longer play the game

People say I'm lazy dreaming my life away
Well they give me all kinds of advice designed to enlighten me
When I tell them that I'm doing fine watching shadows on the wall
Don't you miss the big time boy you're no longer on the ball

I'm just sitting here watching the wheels go round and round
I really love to watch them roll
No longer riding on the merry-go-round
I just had to let it go

John Lennon