Herschel's Garnet Star

 The constellation Cepheus is a north circumpolar constellation that never sets when viewed from the latitude of Creede (37.8° N), although it may be partially obscured by mountains when low in the night sky of spring and early summer.  It is best viewed in the evening hours of October through December.

Cepheus contains (among other things) one remarkable star known by the nickname "Herschel's Garnet Star".  The nickname comes from a description of the star by the German-English astronomer William Herschel (1738-1822).  It's official name is Mu Cephei.

An outline of the constellation Cepheus high in the evening sky of 05 December.

Mu Cephei is the reddish star at the center left edge of the outlined constellation.  Here is a closer look:

E-M1iii + 75mm f/1.8 + softon filter.  ISO 1600, 60 s.

 Mu Cephei is only a magnitude-4.1 star as seen from Earth, but we now know it to be one of the largest and brightest stars in our galaxy, with a luminosity about 270,000 times that of our sun.  It is a red supergiant similar to Betelgeuse, but larger.

The distance to Mu Cephei is very poorly known, with estimates lying between 1300 and 3100 ly.  The star is so large, however, that its angular diameter has been measured by interferometry as 20.5 mas (milliarcsecond).  The nearest distance estimate of 1300 ly then yields a diameter of 8.2 au (astronomical units).  This would extend well beyond the orbit of Mars (r = 1.52 au) in our solar system.  The larger distance estimate yields a diameter of 19.5 au, which would reach out to the orbit of Saturn (r = 9.6 au) . Compared to our sun these values correspond to a diameter that is from 880 - 2100 times larger.

Our sun's mass divided by its volume gives an average density of 1.4 g/cm³. Mu Cephei has a mass of about 19 suns in a diameter 1000 (roughly) times larger.  This yields an average density of 19 × 10^-9 × 1.4 g/cm³ = 2.7 × 10^-8 g/cm³. This is similar to the density of Earth's atmosphere at an altitude above 100 km, i.e., in space.  Mu Cephei is essentially a red-hot vacuum!

Cepheus without the constellation lines.  E-M5iii + Sigma 30mm f/1.4 + softon filter.  ISO 1600, 30 s.

 

Boxing Day Moon

 The last full moon of 2023 is today, Boxing Day, 26 December.  It is the 13th full moon of the year and is traditionally known as the "Cold Moon".

E-M1iii + AT72EDII.  ISO 200, 1/1600 s.

Not a super moon, not a micro moon, not a blue moon, just a regular old full moon, pretty much indistinguishable from all the superlative-laden full moons.

Polaris on Christmas Eve

 Polaris (Alpha Ursae Minoris), or the North Star,  lies only 0.64° from the North Celestial Pole (NCP).  Unlike the biblical Christmas Star, it is a constant presence in the night sky of the Northern Hemisphere and serves as a convenient guide star for navigation.

Sony A7iii + Asahi SMC Takumar 120mm f/2.8 @ f/5.6.  ISO 1600, 30 s.

 In this 2°-wide image Polaris is the bright six-pointed star top center.  The NCP is marked with a white cross. 

The lens used here is an M42 screw-mount Asahi (Pentax) Super-Multi-Coated Takumar 120mm f/2.8 from the early 1970s, so about 50-ish years old.  I stopped it down two stops to produce the diffraction star effect.  This is the first astrophoto I've taken with a Pentax lens.

Polaris marks the end of the handle of the LIttle Dipper:

credit: SkySafariAstronomy.com

Solstice Sunspots

 Today is the Winter Solstice and the shortest day of the year in the Northern Hemisphere .  There are currently many sunspots and active regions on the sun:

These images were taken with an AT72EDII refractor, Lunt solar wedge + ND-0.9 filter, and E-M5iii camera, ISO 200, 1/800 s.  These are both the same image - the second one has false color added. Sometimes this results in a more interesting picture.

(PSA: Viewing the sun is dangerous.  It requires special filters.  Double-check everything. And then check again.)

Nothing to worry about when photographing the moon (other than dropping things in the dark). Here is the 9.9d-old Solstice moon:

E-M5iii + AT72EDII.  ISO 200, 1/800 s.

The Buck Moon 2023

 According to the Old Farmer's Almanac the full moon on July 3 is (or was, I'm writing this in December) called the "Buck Moon".  I had the idea that I should get a shot of the moon rising over the eastern ridgeline.  The sky was clear except for one solitary cloud that was positioned exactly over the spot where the moon would rise.  It made for a dramatic image:

E-M5iii + AT60ED. ISO 3200, 0.5 s.

I was going to pack up and head back in but then decided to wait and see what happened.  My patience was rewarded.  The cloud dissipated and drifted away.

E-M5iii + AT60mmED. ISO 200, 1/500 s.

The Collinder 65 star cluster

 Collinder 65 (Cr 65) is a wide (about 3.7°) star cluster in Taurus midway between the constellations Orion and Auriga.  It was catalogued by the Swedish astronomer Per Collinder in 1931.  It is not very well known but is easily recognized with binoculars.

The location of Collinder 65 is marked by the red circle. Chart credit: IAU (Creative Commons Attribution 4.0 International license)

Collinder 65 is marked with the white circle.  Sony A7iii + Rokinon 35mm f/1.8 + softon filter.  ISO 1600, 30 s.

A closer look.  E-M1iii + 75mm f/1.8 + softon filter.  ISO 1600, 60 s.

The yellowish star near the center in this image is 119 Tauri, a red supergiant.  The brighter star to the left of center is magnitude-3 Zeta Tauri, and just above that is the Crab Nebula, M1.  Here is a zoomed-in view:

The Crab Nebula, Messier 1, is the small blob in the center of this 3°-wide image.

Here is a closer view of Collinder 65:

E-P5 + Rokinon 135mm f/2 + Kase AstroBlast filter.  ISO 1600, 30s.

In this image 119 Tauri has a cyan or teal hue.  This is a consequence of the photographic color-balance processing used to mitigate red airglow.  There are no green-hued stars in nature.   A similar color-shift is evident in this image of the Hyades cluster:

E-M1iii + Olympus 75mm f/1.8 + softon filter.  ISO 1600, 30 s.

The brightest star in this image is Aldebaran, a magnitude-0.9 orange giant.  Aldebaran is not a physical member of the Hyades cluster - it is a foreground object at roughly half the distance (67 ly).

Mirfak and the Melotte 20 star cluster

Mirfak (Alpha Persei) is the brightest (mag 1.8) star in the constellation Perseus and the brightest member of the Alpha Persei Moving Group, a loose cluster of stars also known as Melotte 20.  This cluster comprises about a dozen bright stars and perhaps several hundred stars total depending on how the boundary is defined. It is about 600 ly distant.  It is an easy sight with binoculars.

credit: IAU (Creative Commons Attribution 4.0 International license)

Mirfak and its associated cluster is on the left.  The Pleiades (M45) is on the right. E-M5iii + Sigma 30mm f/1.4 + softon filter. ISO 1600, 30s.

Mirfak and Melotte 20.  E-M1iii + Olympus 75mm f/1.8 + softon filter.  ISO 1600, 30 s.

Mirfak (left) and Algol (right). E-M1iii + 75mm f/1.8 + softon filter.  ISO 1600, 30 s.

MIrfak and Melotte 20.  Olympus E-P5 + Rokinon 135mm f/2 + Kase starblast filter.  ISO 1600, 30 s.

A 2-deg close-up of Mirfak and surroundings without the softening filter. E-P5 + Rokinon 135mm f/2.  ISO 1600, 30 s.

Mirfak is a yellow-white supergiant with an estimated mass of about 8.5 solar masses.  This is very near the mass threshold that separates future supernovas from future white dwarfs.  Stars more massive than this will eventually collapse and then explode as a supernova.  Less massive stars will shed their outer layers as a planetary nebula and then fade away as a white dwarf.

Winter circles

 Polaris (Alpha Ursae Minoris) is known as the "Pole Star" or "North Star" because it is the nearest naked-eye star to the North Celestial Pole (NCP).  Under casual observation it appears to be motionless while the night sky rotates counter-clockwise around it.

E-M5iii + Leica 15mm f/1.7, live composite mode.

Close examination reveals that it is not quite at the center of rotation.  Polaris is currently 0.63° from the NCP. This is about 1.25 times the width of the full moon.  This distance is slowly changing because of precession of the earth's axis of rotation.  One hundred years ago the separation was 1.1°, and in 1776 it was 1.9°.  According to Belgian astronomer Jean Meeus the closest approach will occur on 24 March 2100, when the NCP will pass within 0.45° of Polaris, just slightly smaller than the width of the full moon.  Mark your calendars!

Polaris has significance beyond just being a navigational aid.  It is also the closest (430 ly) and brightest (mag 2.0) Cepheid variable star.  The brightness variations are too small (about 0.1 mag) to be noticed visually.  Polaris is close enough that its distance has been measured by parallax. This provides an important calibration point for the luminosity versus period relationship of Cepheid variables, which are used to determine the distance scale of the local universe (< 20 Million ly).

In addition to being a variable star, Polaris is also a multiple star, part of a three-star system: Aa, Ab, and B.  One of the companion stars (B) can be seen in small telescopes.  It is a magnitude 9.1 star at a separation of 18".  I have spotted it in a 60mm telescope, but have been unsuccessful with a 50mm scope.  The other companion (Ab) orbits too closely to be resolved easily and was first detected spectroscopically.  It was resolved photographically by the Hubble Space Telescope in 2006.

E-M5iii + Leica 15mm f/1.7 + softon filter.  ISO 1600, 60s.

There are several ways to find Polaris if you are unfamiliar with the night sky.  A magnetic compass will point toward the magnetic north pole, which is currently 8.4° east of true north when measured from Creede.  This is illustrated in the next picture, where I have added an outline of the Little Dipper and two white circles. The circle that intersects Polaris marks the location of the North Celestial Pole.  The circle to the right is the direction that will be indicated by a magnetic compass: 8.4° to the right (east) of the NCP.

Most people are familiar with the asterism known as the Big Dipper, which is part of the larger constellation Ursa Major.  The extension of a line between the two bright stars at the end of the "dipper" will point very close to Polaris.  I have added a line between these two stars (Alpha and Beta Ursae Majoris, aka Dubhe and Merak) in the above image.  Unfortunately, at this time of year (early December) the Big Dipper is skimming the northern horizon in the early evening and is largely obscured by mountain ridges.

 The above images show a yellowish glow along  the northern horizon.  This is what remains after color balancing the night sky.  The original daylight balanced image looks like this:

 I do not know if this pinkish glow is airglow or auroral glow.  It may be a combination of both.  It is not perceivable by eye, but is easily revealed in a long exposure (30-60 s) photograph.  The sky brightness at this time was sqml=21.09, which is considerably brighter than a "normal" dark sky in Creede.  The sun has been very active recently, and reports of auroral activity farther north are very common.  A Hydrogen-alpha image of the sun earlier the same day shows many spectacular prominences along the sun's limb.

Lunt LS50THa double stacked + ZWO ASI178mm camera.  Processed from a stack of 66 video frames.

As usual, click on any image to get access to the full-size version.

A tale of two stars

 Two stars of historical and cosmological significance are currently well situated in the northern evening sky: Beta Persei (Algol) and Delta Cephei.  These stars share two things in common: they are both first-of-kind variable stars and they were both subjects of study by the young English astronomer John Goodricke, FRS.

Algol, aka the "Demon Star", is an eclipsing binary whose variability was likely known as far back as the ancient Egyptians.  Goodricke was the first to determine its regular period of 2.86 days and in 1783 (at age 19)  proposed an eclipsing mechanism as the cause.  For this work he was awarded the Copely Medal by the Royal Society.  The next year he discovered the variability of the the star Delta Cephei. Delta Cephei is the prototype of the class of variable stars known as "Cepheids", which are used to determine the distance scale of the local universe.  Goodricke was elected as a Fellow of the Royal Society in 1786 at age 21, but died of pneumonia only four days later and never learned of the honor.

Algol is marked by the white circle.  The Pleiades star cluster is on the right edge and the star Mirfak (Alpha Persei) is on the left. E-M1iii + Sigma 30mm f/1.4  + softon filter. ISO 1600, 30 s.

 Algol (Beta Persei) varies in magnitude from 2.1 to 3.4, a factor of 3.3 in brightness.  It is easily visible to the unaided eye.

The constellation Cepheus.  Delta Cephei is marked by the white circle.  E-M1iii + Sigma 30mm f/1.4 + softon filter.  ISO 1600, 30 s.

Delta Cephei varies in magnitude from 3.5 to 4.4 over a period of 5.4 days.  The brightness changes are caused by radial pulsations of the star's atmosphere. In 1908 Henrietta Swan Leavitt discovered a relationship between the pulsation period and absolute brightness for this type of star.  Her findings were published in 1912.  This relationship is a crucial tool used to establish the distance scale of the local universe (within 20 million ly).

Another interesting star in the above image is the reddish star about a quarter-frame below Delta Cephei.  This is Mu Cephei, Herschel's "Garnet Star".  It s a red supergiant similar to Betelgeuse and is one of the largest and brightest stars in our galaxy.

As usual, click to get access to the full-size images.

Frosty moon and star trails

 The recent full moon of 27 November, the 11th of the year, has traditional nicknames that differ depending on the source, but the one that seems appropriate this year is "Frost Moon".  According to The Old Farmer's Almanac this name comes from the Cree and Assiniboine cultures.  In the popular press it has been more commonly hyped as the "Beaver Moon", which is the prevailing nickname.  

Full moons with snow on the ground present interesting photographic opportunities.

Olympus E-M1iii + Leica 9mm f/1.7, live composite mode, 1 hour.

 When I retrieved the camera after this exposure the lens was frosting over and the battery was dead.  The outside temperature was 5° F, dropping toward an eventual low of -12° F the next morning.  Frosty indeed.

The Frost Moon.  AT80EDT telescope.

The Frost (aka Beaver) Moon setting over Bristol Head

 

The setting-moon pictures were taken on the morning of the 28th. The temperature was -11° F at the time.  It kept dropping.

Some old telescopes brought back to life

 A neighbor recently brought over a large box of telescope parts, hoping that I could help make sense of what he had.  After some sorting, puzzling, and discarding of useless parts, it turned out that there were three potentially useful telescopes.  It took only a modest investment in new parts to create a working alt-azimuth mount.  I was also able to contribute some other accessories that have been sitting unused in my closet for many years.

The three scopes, which are now all in operating condition with interchangeable accessories, are:

1.  Celestron C90 f/11 (1000 mm focal length)
   
2.  Tasco 60mm f/15 (900 mm focal length)
3.  Celestron Firstscope 60Az f/12 (700m focal length)

The focal ratios are rounded to the nearest integer.  The stated focal lengths are the numbers printed on the scopes.  The C90 is a Gregory-Maksutov design with the old classical helical-focusing barrel. Based on the date printed on the manual (10/98) it is probably from the late 90s or early 00s.  The the 60mm scopes are air-spaced achromats of unknown age.

Last night the sky cleared unexpectedly after a snowy and rainy day.  I took two of the scopes out to test them on the Moon and Saturn.

Here is the Celestron Firstscope:

The mount consists of a Neewer 36mm low-profile ball head, a PrimaLuceLab 140mm PLUS dovetail plate, and two JJC TR-1II tripod mount rings supplemented with felt.  The dovetail plate is dual-sided: one side has an Arca-Swiss dovetail groove and the other side is a Vixen dovetail.  That makes it compatible with photo mounts or telescope mounts, depending on which side is facing out.  The tripod mount rings are made for Canon telephoto lenses but work quite well with this tube diameter (63mm) when padded out with felt strips.  

This mount configuration works much better than whatever came with the telescope originally.  It is possible to rotate and slide the tube for optimal balance and accessory position, and the long dovetail gives additional balance adjustment as well as being compatible with most standard photo and telescope mounts.  In the above photo both the dovetail plate and optical tube are pushed well forward of normal to balance the weight of the camera.

Here is a picture of the 5.8-day-old moon taken with this setup:

C60 + E-M5iii, ISO 800, 1/50 s.  Untracked.

These "beginner" telescopes can perform quite well when used with proper mounts and accessories.  The moon diameter in this image corresponds to a focal length of 704mm, very close to the number printed on the scope.  The actual focal ratio is then 704/60 = 11.7.

The C90 started out on the same ball-head mount:

 After a few exposures I decided to switch to a computer-driven mount and astro camera in order to get higher resolution.

Here the C90 is riding on an iOptron SmartEQ Pro+ computerized mount with a ZWO ASI178MC camera.  The iPad tablet controls the mount via wifi and the laptop computer is running the camera over a USB cable connection.

I took short videos of the Moon and then switched over to Saturn.  The files were processed with AutoStakkert and Registax. 

Looks like a great scope!

The measured diameter of the moon in the above shot with the C90 yields a focal length of 791 mm.   The focal length of moving-mirror scopes (like this one) will change to match the exact position of the focal plane (image sensor location), so this difference between the measured and labeled focal lengths might be completely normal.

I didn't night test the Tasco scope, but I did use it to snap a few daytime pics of the local mountains.

Bristol Head

Any photo taken at this distance with this focal length (900 mm) will be affected by atmospheric blurring and this one is no exception.  However, it performed quite well in spite of the turbulence.

Tasco 60mm f/15 on a Stellarvue M002C alt-az mount.

The Tasco scope in this photo is using the same rings and dovetail bar as the Celestron 60mm, but the dovetail bar has been flipped over so that it will fit into the Vixen slot in the Stellarvue mount.

added 11/20:

It is 24° F with snow on the ground, but the sky is clear so I set up the Tasco on the porch and took a quick shot of the 8.1-d old moon:

Tasco 60mm f/15 + E-M5iii.  ISO 400, 1/160 s. Untracked.

The moon diameter in this image yields a calculated focal length of 909 mm, within 1% of the number printed on the scope.

As usual, click an image to get into gallery view, then download or open in a new tab to see the full-size images.

The Flying Star

 The star 61 Cygni in the constellation Cygnus (The Swan) has the largest proper motion of any naked eye star at 5.3"/yr, about half that of Barnard's Star.  The motion was first noted by Giuseppe Piazzi  in 1804 (three years after he discovered Ceres) and the star acquired the nickname "Piazzi's Flying Star".  It's distance was measured via parallax by Friedrich Bessel in 1836.  Bessel's result was the first direct distance measurement for any star other than our sun. At 11.4 ly it is the 14th closest star system and the 5th closest naked-eye star, after Procyon. 

61 Cygni is actually a double-star system with the two stars having a combined magnitude of 4.8.  Separated by about 31" they are an easy target for small telescopes.  Under fairly dark sqml=21.4 skies I was just barely able to make out this star with averted vision after a few minutes of letting my eyes adjust, so the "naked eye" designation is definitely a personal attribute.  It was dead easy with a 2x54 binocular.

Cygnus setting over Bristol Head. 61 Cyni is marked by the white circle. EM1iii + Leica 15mm f/1.7 + softon. ISO 1600, 60 s.

 

E-P5 + Rokinon 135mm f/2.  ISO 1600, 60 s. 2° field.

61 Cygni. E-M5iii + AT60mmED f/6 refractor. ISO 1600, 10 s. 0.5° field.

Imaging the Gas Giants

 The Gas Giant planets are Jupiter, Saturn, Uranus, and Neptune.  I recently decided to take a try at capturing images of Jupiter and Saturn.  How hard could it be?  Pretty hard, it turns out.

The problem with high-resolution imaging is that air currents are constantly shifting the image of the object under study.  When we view an object through an eyepiece our brain tends to filter out the small movements and we learn to perceive detail in spite of the motion.  A camera is not so forgiving.  A single exposure captures the image at one moment in time when things might be in rapid motion and therefore blurred.  The solution is to record video and then select the sharpest frames and add them together to get an integrated picture using only the best data obtained.  So that is what I did, after watching many online videos to benefit from the experience of others.

For these images I used a Celestron C8 SCT (Schmidt-Cassegrain Telescope).  The video camera was a ZWO ASI178MC astro camera, which has 0.0024 mm pixels.  With this pixel size and the 2032 mm (approximate) focal length of the telescope, the image scale was 0.24 arcsec per pixel.  An 8" scope has a resolution of about 0.6 arcsec, so this is probably an adequate amount of oversampling.

The video clips (each less than one minute long) were processed with a program called AutoStakkert.  The sorted and stacked images were then further processed with a program called RegiStax.  The results are shown below.

Saturn, 04 Nov 2023.  Celestron C8 + ASI178MC.

Jupiter, 04 Nov 2023.  Celestron C8 + ASI178MC.

As a first try (ignoring earlier non-video attempts) I am pleased with the results.  However, these images are not so great on an absolute scale.  On a quality scale of 1-10, where "1" represents a blurry image from a cellphone hand-held up to the eyepiece, and "10" represents Hubble-esque images from 11-14" scopes produced by skilled practitioners, these rank at about a "3" (maybe 4, but definitely no higher).  There is much room for improvement.  Will I continue?  I don't know - these kind of images require a lot of computer processing and storage and are really a lot of work.  I think I would rather spend my time fishing, biking, or skiing rather than sitting in front of a computer monitor.

As a counterpoint, I also captured a wide-angle image of Uranus which was a single 60 sec exposure at an image scale too large to see the planet's disc.  This one-and-done type of imaging is more to my liking.

Uranus, 04 Nov 23.  E-P5 + Rokinon 135mm f/2.  ISO 1600, 60 s. 2° field.