Perihelion

 Today was doubly eventful.  This morning the first full moon of 2026 occurred at 3:04 am MST.  Seven hours later at 10:15 am MST the Earth reached perihelion (closest distance) in its orbit around the Sun.  The two events are totally unrelated.   The angular size of the sun is currently 32.5 arcmin or 0.542 deg.  I photographed it in both white light and Hydrogen-Alpha light.

Equipment:  Astro-Tech AT72EDII f/6 refractor + Kendrick solar filter for a "white-light" photosphere image, and a Lunt LS50THa double-stacked solar scope + ASI178mm camera for a view of the Hydrogen-Alpha chromosphere.

 

"white light"

Hydrogen-Alpha

Hydrogen-Alpha: negative, false-color

The negative, false-color image makes it easier to see the prominences.

The Wolf Moon and more-distant moons

 The first full moon of 2026 occurs at 3:04 am MST on 3 January.  The picture below was taken at 8:25 pm MST on 2 January, a little more than 6-1/2 hr before maximum.  The full moon of January is traditionally known as the "Wolf Moon".

Equipment: Astro-Tech AT72EDII f/6 refractor and Olympus E-M5iii camera.

The Wolf Moon

 

The planet Uranus was the first planet discovered in modern times, by William Herschel in 1781.  It is currently located in the sky near the Pleiades star cluster, which makes it an easy object to locate and view with binoculars.   The image below is a 1-deg FOV centered on Uranus:

Uranus (center). 1-deg FOV.

 Much to my surprise, this 20-sec exposure also recorded the two largest moons of Uranus.  Here is a 1/4-deg FOV enlarged from this image:

Uranus (center) and two of its moons. 2x enlargement.

The two faint "stars" nearest to the overexposed image of Uranus are its moons Titania (left) and Oberon (right).  These moons were also discovered by William Herschel, in 1787.  They are both slightly less than half the size of our moon, but immensely farther away.  Our moon is 1.2 light-seconds distant, but Uranus and its moons is 2.6 light-hours away. 

Here is a chart showing the location of these moons:

credit: SkySafariAstronomy.com

 

According to SkySafari, Titania is currently magnitude 13.8 and Oberon is magnitude 14.0.

A 3x enlargement

Where to look for Uranus:

credit: SkySafariAstronomy.com

 

New Year's Moon

 The first full moon of 2026 occurs on Saturday, 3 January.  This is an image of the moon on New Year's evening, two days before full.

Equipment: AT72EDII refractor

Only short star exposures are possible because of the bright moon light.  These are 20-sec exposures of two well-known clusters:

M45, the Pleiades

 

The Double Cluster in Perseus

Year-end Sun, Moon, star clusters

The Sun today, 31 Dec, with an Astro-Tech AT72EDII refractor and Kendrick solar filter:

 

The Moon during twilight, same telescope:

 Last night (30 Dec) was another test of the AT72EDII with an Orion 1x field-flattener and a Metabones 0.71x Speedbooster.  This combination yields a 305mm f/4.3 optical train.  Tracking was a little bit off, but exposures were limited to 20 sec anyway because of the bright moon.  

M38, the "Starfish Cluster", in Auriga.  2-deg FOV.

M35 cluster in Gemini.  2-deg FOV.

 The open cluster M35 is a well-known show-piece object for small telescopes.  It apparently is also known as the "Shoe-Buckle Cluster".  I have been stargazing for over 60 years and was unaware of that nickname until just now, when I looked it up.

Happy New Year.

Christmas constellations, Boxing-Day Sun

 The sky last night was unexpectedly clear, so I grabbed the Olympus E-M1iii and Leica 9mm f/1.7 lens and set them up on a Vixen Polarie tracker.  

Orion and Sirius right of center, Jupiter and Gemini to the left

 The planet Jupiter is currently the brightest "star" in the evening sky, more than three times brighter than Sirius (bottom center), which is the brightest actual star.

Two Dippers.

 The "LIttle Dipper" (left, above) and "Big Dipper" (right) are both asterisms associated with the constellations Ursa Minor and Ursa Major, respectively.

credit: SkySafariAstronomy.com

 There was some hope on the interweb for another display of Northern Lights last night, but I didn't see any hint of anything near midnight.  Of course, my field of view in the back yard is very limited. The picture below shows the current sunspots that may cause geomagnetic storms.  This image was taken with an AT72EDII refractor with a front-mounted Kendrick Astro Instruments solar filter.

 

 

Testing focal reducers on the Sun and some familiar star clusters

 After two nights with the Canon FD 300mm f/4 L lens, it seemed worthwhile to look at some optical alternatives.  I used the Astro-Tech AT72EDII f/6 refractor with four different back-end configurations:

• Orion 1x field flattener
• Astro-Tech 0.8x flattener-reducer
• Metabones 0.71x Speed Booster (Nikon F-mount)
• AT 0.8x + Metabones 0.71x combined (0.568x reduction)

 All four configurations were tested on the sun over the past two days with a Kendrick solar filter on the front of the telescope.  Effective focal lengths were derived from each image based on the sun's current angular diameter of 1951 arcsec.   The most extreme combination (0.8x + 0.71x) was also star tested with some familiar clusters currently high in the sky.

Here is a montage of solar images from the four configurations:

 The two images on the left were obtained yesterday, the two on the right were obtained today.

The four derived focal lengths are:

1.  430 mm
2.  346 mm
3.  308 mm
4.  242 mm

 All of these values are within 1% of nominal.  

The Metabones Speedbooster was attached using a Nikon-F T-thread adapter.  The backspacing between the end of the flattener/reducer and the camera focal plane was set to a nominal value of 55 mm for all combinations.  

When the Speedbooster is combined with the 0.8x reducer the telescope is converted to a 242 mm f/3.4 lens.  This combination reduces the size of the image circle so that it barely covers the micro-four-thirds sensor on the E-M5iii camera.  The following images were variously cropped to discard the dark corners.  At the outer edges of the image circle star images were distorted by coma.  There was approximately a 2-deg field of acceptable quality.  At this focal length the sensor covers a 3-deg x 4-deg field of view.

The measured sky brightness during the star tests on Monday night was a typical 19.68 mpsas.  All of these images were 30 or 40 sec single exposures at ISO 1600.

M45, the Pleiades.

 

The Pinwheel Cluster (M36) lower left.  Starfish Cluster (M38) upper right.

 

The Double Cluster in Perseus

Caroline's Rose in Cassiopeia

M31, the Great Andromeda Galaxy

Conclusions:

I was feeling a bit disappointed by the previous Canon 300mm results, but comparison of these 242-mm images to the Canon images has changed my mind.  The Canon images seem a bit better.  Next test: the 0.8x and 0.71x reducers by themselves.  That should be interesting.

The telescope:

 

Some more pre-solstice star clusters

 The sky brightness last night was a disappointing sqml=19.6 mpsas, which is normal for urban Santa Fe.  Wide-field starscapes are a futile effort under such skies, so long-focal-length photographhy is the solution.  I used the Canon FD 300mm f/4 L lens to photograph some more star clusters that were high in the sky (with an Olympus E-M5iii camera).

NGC 7789, "Caroline's Rose" in Cassiopeia

 The open cluster NGC 7789 in the constellation Cassiopeia was discovered by Caroline Herschel in 1783.

 

NGC 457

The open cluster NGC 457 in Cassiopeia is also known as the "Owl Cluster".  It was discovered by William Herschel (Caroline's older brother) in 1787.

Mirfak

 The star at the center of this image is Alpha Persei, Mirfak, the brightest star in the constellation Perseus.  It is the brightest member of the Alpha Persei Cluster, or Melotte 20, which extends beyond the field-of-view of this image.

The Double Cluster

 The "Double Cluster" in Perseus consists of NGC884 (left) and NGC 869 (right).  These star clusters are a very impressive sight in small telescopes.

M36 in Auriga.

 

M34 in Perseus