Framed Rainbow

Rural Scene

While visiting my niece on May 25th in rural Orange, Virginia a late afternoon rainbow appeared attractively framed by backyard trees.

The background clouds are not very dark, so rainbow colors are not as dramatic as they could be.

A few moments before the previous picture was taken colors were slightly more intense.
The rainbow added extra beauty to the pleasant countryside visible from my niece's house.

Sunspots, Old and New

Unexpected Activity

Thin early morning clouds cleared on May 7th leaving nearly clear skies, a light breeze, and temperature in the mid-60's. In a welcome change from the recent sunspot drought two spots and some prominences were on display this morning. The following 17-panel mosaic shows the unexpected features on the Sun's eastern hemisphere. (Click on the image for a larger, more detailed view.)

Sunspot 2740, on the right, is actually the same as old sunspot 2738. Sunspot 2738 remained intact long enough to travel across the Earth-facing solar disc a couple weeks ago, disappear around the western limb, travel across the solar far side, reappear on the eastern limb with a new number, and travel about one third across the solar disc again when this image was made on May 7th. A few days later it disintegrated leaving behind only its newer companion, sunspot 2741, seen near the eastern limb.

A nice array of prominences were scattered along the eastern limb as shown in the next 5-panel mosaic. Longer exposure time was used to capture relatively dim prominences. The overexposed solar disc has been blacked out, dim light levels enhanced, and yellow color added. It takes some work to make the prominences stand out above the background. I used both dark and flat field frames for this mosaic.

Both sunspots and a few prominences are captured in the next two single frame views. The first image was processed to bring out limb details. Notice the extended dark filament rising from the right side of sunspot 2740 in the first image. This was a transient eruption, as you can see by comparing the first image with the second image below taken 40 minutes before the first image.

It's difficult to preserve light and dark features in a sunspot umbra without decreasing the contrast of dark spicules. The next two images show this for sunspot 2740. The first image was processed to preserve umbra details. The second image was processed to show greater spicule contrast. (Click on the images to better see the umbral details.).

Solar minimum grinds on. Who knows when the Sun will display this number of features again. 

Globular Clusters

Beautiful Evening

Evening, May 6th, a lovely night with no moon and temperature falling from the 70's to the 60's. I decided to try a ZWO 174 monochrome camera for night sky imaging. The camera was initially attached at prime focus on a Stellarvue 130mm refractor seen below waiting for darkness to fall.

The telescope is not permanently mounted, so its polar alignment is only approximate after each initial setup. Consequently, the mount alone will not track accurately enough for long exposure imaging. At present I have no way to make automatically guided images with a guiding camera. Although the mount tracks well enough for visual observing, stars slowly drift in the field of view as time goes on. This limits camera exposure times to values where star trails don't show up. I spent time trying different exposure times to see when star trails became visible. For example, at prime focus, I discovered exposure times less than 15 seconds were required to keep stars nearly round.

I then pointed the telescope at globular cluster M3 in the constellation Canes Venatici and stacked 40 individual 15-second exposures to make a single image equivalent to a 10-minute exposure. The next picture shows the result.

Notice the diagonal streaks above. These are caused by "hot pixels" in the camera chip. Actual stars don't trail in the image because software aligns all star images before adding them together in a stack. Unlike stars, however, hot pixels were not aligned, so the diagonal streaks show how stars would trail during a single equivalent 10-minute exposure if stars were not aligned before stacking. The hot pixels appear because I didn't take a dark frame for this image. A dark frame, or image obtained when no light falls on the camera chip, records the hot pixels and can remove them by subtraction. I manually removed the diagonal streaks in the next image, but a slight glow protruding on the right edge still remains.

As you can see above, the image scale is too small at prime focus. Stars look blocky instead of round. Star images look better with a 2X Barlow lens which produced the following image of globular custer M13 in the constellation Hercules. This is a stack of 40 individual 5-second exposures made with a gain setting of 350. I used a dark frame this time, so no diagonal hot pixels streaks are visible.

I don't know why I limited myself to 40 frames. In the future I will surely try for more. Next, I tried globular cluster M92 in the constellation Hercules. The following image is a stack of 40 individual 7-second exposures for a total exposure time of 280 seconds.

Finally, I had the best luck with globular cluster M5 in the constellation Serpens. There was a download malfunction while capturing images, so only 27 individual 7-second frames were stacked with gain setting at 320.

I moved the telescope to globular cluster M4 in Scorpius, but it was too near the horizon for good results. In the future I'll need larger stacks for longer equivalent exposure times. More magnification would also help. Although the grayscale images here are nowhere near as good as those produced by experienced dark sky imaging experts, I'm amazed at these first time results.  

Beaver Dam & Birthday

Bike Ride With Sophie

A nice warm spring afternoon on April 25th was the perfect day to cash in a Christmas gift "coupon" from my granddaughter. This coupon treated me to a bike ride with Sophie, so off we went on the wonderful local bike trail. 

Our destination was a beaver dam near a wooden bridge along the trail. I have passed over this bridge many times, but never noticed the beaver pond until my daughter recently told me about it. Here Sophie stands on the east side of the bridge beside part of the dam.

The dam stretches the entire length of the bridge and beyond. Here's the view along the dam from its eastern edge.

Walking to the other end of the bridge gives the view looking from the west.

On the bridge's western end the dam begins to curve out to the right and continues in a semicircular arc seen in the next panoramic view.

Where are the industrious beavers who built the dam? We didn't see any. They are probably inactive during daylight. Their lodge is visible from the midpoint of the bridge.

This downed tree shows evidence of chewy beaver woodwork.

Apparently, some traps have been set in the area. Are these designed to control the beaver population, or to trap beaver predators? I don't know.

After our nice bike ride, Sophie and I joined her sister, Annabelle, and her Mom for an informal picnic celebration of Annabelle's 6th birthday. Annabelle really enjoyed listening to squeaky sounds on this swing with her Mom.

Sophie and Annabelle had a pleasant evening of fun after the picnic at the local playground.