Two close double stars

 Last night was calm and the air was steady, so it was a  good opportunity to look at a couple close double stars: Izar (Epsilon Boötis) and Porrima (Gamma VIrginis).  I was briefly joined by the neighborhood raccoon, which paused to watch while on its nightly patrol.  

Izar is a challenge for small telescopes, with a separation of 2.9 arcsec.  The pair consists of a magnitude-2.6 primary (spectral type K0, orange) and a magnitude-4.8 secondary (spectral type A2, blue).  Using the Celestron C6 (FL ≅ 1600mm) and a Criterion A.R. 7-mm eyepiece (magnification = 228x) I had no trouble visually separating this golden and blue pair. 

 

Izar.  C6 + 2.5x Powermate + E-M5iii.  ISO 400, 1/5 s, stack of six images.

Porrima consists of two nearly identical F0 (blue) stars with individual magnitudes of 3.6. They orbit each other with an eccentric orbit with a period of 169 y.  At their closest approach, which occurred in 2006, the separation was about 0.4 arcsec.  They are currently separated by 3.5 arcsec.  This separation will more than double when they are at maximum separation in 2107.

Porrima.  C6 + 2.5x Powermate + E-M5iii.  ISO 400, 1/5 s, stack of seven images.

 

finder chart for Izar. credit SkySafariAstronomy.com

 

finder chart for Porrima. credit: SkySafariAstronomy.com

Reprocessing some older images from the Seestar S50

 Sometime in late 2024, either November or December, ZWO released version 2.2.0 of their Seestar app, which included a new feature: "AI Denoise" or "intelligent Denoisingfeature" as they called it in the release notes.  I did not try it out until just last week.  It seems to work remarkably well.  I have tried to replicate the results with my previous post-processing methods, but so far have not succeeded.  

Here are some previous images, newly processed with this new denoising algorithm:

 

M1, the Crab Nebula inTaurus. 5 min, 21 Jan 25.

M8, the Lagoon Nebula in Sagittarius, 4 min. 29 Aug 24.

M16, the Eagle Nebula in Serpens. 5 min, 29 Aug 24.

M20, the Trifid Nebula in Sagittarius. 3 min, 29 Aug 24.

M27, the Dumbbell Nebula in Vulpecula. 3 min, 29 Aug 24.

M42, the Orion Nebula. 5 min, 21 Jan 25.

M81 (right) and M82 (left) in Ursa Major. 20 min, 23 January 2025.

The Double Cluster in Perseus. 21 min, 23 Jan 2025.

NGC 7789, Caroline's Rose cluster, in Cassiopeia. 5 min, 21 Jan 2025.

Three northern spiral galaxies

 There are three spiral galaxies in the northern constellations of Canes Venatici and Ursa Major that are spaced almost equidistantly along a line in the sky: M63 (the Sunflower Galaxy), M51 (the Whirlpool Galaxy), and M101 (the Pinwheel Galaxy).  Here is a finder chart:

right of center, top to bottom:  M63, M51, M101.  credit: SkySafariAstronomy.com

 The upside-down Big Dipper is the prominent asterism in this chart, which makes locating these galaxies relatively easy.  At this time of year they are high in the sky in the late evening.

I used the Seestar S50 to obtain images of each galaxy.

M63, the Sunflower Galaxy.  Seestar S50, 16 min.

 M63, the Sunflower Galaxy, is in the constellation Canes Venatici.  It is a spiral galaxy about 29 million ly distant.  The spiral arms are too thin and tightly wound to be resolved by the Seestar telescope.

 

M51, the Whirlpool Galaxy.  Seestar S50, 18 min.

M51, the Whirlpool Galaxy, is also in the constellation Canes Venatici, at a distance of 28 million ly.  It is a "showpiece" galaxy, featured in many publications.  It is one of the first spiral galaxies observed and sketched by Lord Rosse in the 1850s.  The 72-inch-aperture reflecting telescope used by Lord Rosse (William Parsons, 3rd Earl of Rosse) was the largest in the world until 1917.  At that time these galaxies were called "Spiral Nebulae".  It wasn't until the 20th century that it was determined that these nebulae are galaxies of stars similar to our Milky Way, but at immense distances.

M101, the Pinwheel Galaxy.  Seestar S50, 16 min.

 M101, the Pinwheel Galaxy, is a nearly face-on spiral galaxy in the constellation Ursa Major.  It is 23 million ly distant, and its spiral nature was first recognized by Lord Rosse.

More galaxies with the Seestar S50

Regulus (Alpha Leonis) is the brightest star in the constellation Leo and the 21st brightest star.  Here is a 10-sec exposure obtained with the Seestar S50 and a cross-star filter:

Regulus.  10-sec exposure with cross-star filter.

 The cross-star filter interferes with tracking and stacking when the Seestar S50 is used in alt-azimuth mode (the physical default).  The diffraction spikes have a fixed orientation with respect to the image sensor, but the star field rotates while the telescope tracks (this is a well-known effect with alt-az telescopes, called "field rotation").  This seems to interfere with the stacking algorithm, so the software rejects subsequent exposures and won't stack beyond the initial image.  This happens mostly when there are bright stars with prominent diffraction spikes.

There is a dim galaxy in the field of view close to Regulus, so the cross-star filter was omitted in order to obtain a long exposure.  Here is an 15-min image obtained without the filter:

Regulus and dwarf galaxy Leo I. 15 min.

 The dwarf galaxy Leo I is a satellite galaxy of our Milky Way galaxy, about 1/50th the size of the Milky way.

 After successfully capturing an image of this dim galaxy, the Seestar was turned to some easier subjects:

M60 (left) and M59 (right). 15 min.

This field shows the galaxies M60  and M59 in the constellation Virgo.   There are multiple additional galaxies visible in this image.

 

M86 (left center) and M84 (right). 21 min.

M86 and M84 are galaxies in the constellation Virgo.  Multiple additional galaxies are visible, too many to specify.

 With previous Seestar images, postprocessing was done by first using the ZWO FitsView app to convert the raw FITS file to PNG format, then importing into Affinity Photo for final (or near final) processing.  This time however, the files were processed in the Seestar app using the AI Denoise feature.  The results are so good that it I will use this method going forward.  

Here are a couple files from the previous post processed with the AI Denoise feature:

NGC 3628, M66, and M65 (the Leo Triplet)

 

M87 (Virgo A)

Sampling some galaxies with the Seestar S50

 Spring is known as "Galaxy Season" because the galaxy-rich constellations Leo, Virgo, and Coma Berenices are high in the sky during late evening.  Last night was a good opportunity to try out the Seestar S50 for galaxy viewing.

The Seestar was operating in "Station Mode", connected to the home wifi, so it was possible to sit comfortably inside while controlling the scope and watching the data accumulate.  One disadvantage of such comfort is that is easy to lose track of local weather.  Some passing clouds  ruined a couple exposures.

The Leo Triplet.  16 min exposure.

 The Leo triplet consists of NGC 3628 (upper left corner), M65 (middle right edge), and M66 (middle bottom).

 

M87. 12 min exposure.

 M87, also known as VIrgo A, is a giant elliptical galaxy in the constellation Virgo.  It is the location of the supermassive black hole that was first imaged with the Event  Horizon Telescope array in 2017.  In addition to the obvious bright blob of M87, there are many other galaxies in this image.  Some of them are circled in the version below:

 

Polaris. 2 min exposure.

 The cross-star filter provides an interesting aesthetic effect in the images with bright stars.  Unfortunately, it seems to interfere with the tracking and stacking algorithm of the Seestar.  Polaris does not move much during short exposures, so there was no problem acquiring this image.

Easter star trails over Santa Fe

 Olympus E-M1iii + Laowa 7.5mm f/2 lens.  Exposure time about 83 min in live composite mode.  It looks like the focus was a bit off, but that just makes the star colors more obvious, so not a bad effect.

 

Three or four double stars in the constellation Leo

 The constellation Leo currently stands high in the sky during the late evening.  This constellation has several attractive double stars that are good targets for small telescopes.  

Three of the stars shown here are gravitationally-bound binary systems.  They are Algieba (Gamma Leonis), 54 Leonis, and 83 Leonis.  A fourth star, Tau Leonis, is classified as an optical double, but it forms a close pair with 83 Leonis, thus forming one half of a "double double".

 

Some double stars in Leo.  E-M1iii + Lumix 20mm f/1.7 + sparkle-6 filter.

credit: SkySafariAstronomy.com

Algieba, Gamma Leonis, is in the "shoulder" of the lion.  The two components have magnitudes of 2.4 and 3.6 and are separated by 4.6 arcsec.  They are easily seen with magnifications of 100x or 150x and form a golden pair of K and G-type stars.

Algieba.  Celestron C6 + E-M5iii.  ISO 200, 1/10 s. stack of three images.

 The double star 54 Leonis is situated on the back of the lion.  This pair of bluish A-type stars has magnitudes of 4.5 and 6.3, separated by 6.3 arcsec.

 

54 Leonis.  Celestron C6 + E-M5iii.  ISO 400, 1/4 s.  Stack of four.

83 Leonis and Tau Leonis form a "double double" in the southern part of Leo.  The 83 Leonis pair consists of magnitudes 6.6 and 7.5, separated by 28.6 arcsec.  The primary is a K-type star slightly larger than our sun.

Tau Leonis is nominally classified as an optical double.  The G-type main star has magnitude 5.1 and is separated from its magnitude-7.5 companion by 88 arcsec.  If the companion is at the same distance (560 ly), then the stars are separated by about 0.24 ly.  The gravitational connection would be tenuous at this distance.

83 Leonis and Tau Leonis.  Orion 80mm ED f/7.5. ISO 1600, 15 s.

 The Santa Fe sky was a slightly darker than average, sqml=19.84, when this image was taken.

Ring around the moon

 I was trying to test a new telescope and eyepiece combination, but the weather wasn't the best.  There was, however, a prominent ring around the moon.  Rings like this are caused by moonlight (or sunlight in daytime) refracting through hexagonal ice crystals in the atmosphere.

Moon over Snowshoe Mtn.  Olympus 9-18mm @ 9mm. ISO 3200, 1/4 s.

 

iphone

Daylight progression on the moon. A triple-star spectrum.

 Monday's moon:

 Tuesday's moon:

 The progression of sunlight over three days, Clavius crater:

 

The progression of sunlight, Plato crater:

Mizar and Alcor in the handle of the "Big Dipper" form a naked-eye double star that resolves into three apparent stars in small telescopes.  A spectrum for each star can be obtained simultaneously with a diffraction grating:

 The rainbow spectrum for Mizar (top star) consists of two closely spaced spectra corresponding to each component (Mizar A and Mizar B).  All three stars, Mizar A,B and Alcor are classified as A-type main sequence stars.  All exhibit strong hydrogen absorption lines, which are evident in the picture above and more clearly seen in the intensity plot below:

The red-dash lines mark the wavelengths of the hydrogen-Balmer series.

 All images were obtained with an Orion 80mm ED f/7.5 refractor.

Quarter-plus moon

 There was finally a break in the weather last night.  At 9 pm MDT the 9.4-day moon was high in the sky, only 15 deg from the zenith.  About one-third to one-half of the sky was still covered with clouds, but the moon stood clear.

The days around quarter-moon are the best time for seeing crater detail because of the low sun-angle near the terminator.  

Orion 80mm ED f/7.5 + E-M5iii.  ISO 200, 1/160 s.

Another look at Regulus

 Regulus, or Alpha Leonis, is the brightest star in the constellation Leo.  At magnitude 1.35 it is the 21st brightest star in the sky.  Regulus  is a quadruple star system.  Regulus A, the bright star visible to the unaided eye, is a spectroscopic double.  A faint companion, Regulus B (HD 87884), is 176 arcsec distant and is also a double star resolvable in large telescopes.

The constellation Leo.  E-M1iii + 20mm f/1.7 + sparkle-6 filter.  ISO 1600, 20 s.

 Constellation photography in urban Santa Fe is difficult because of the large light gradients.  The lower right corner of the above image reveals the brighter sky to the south.  On this particular night (30 Mar) the measured sky brightness to the north was sqml=19.53, somewhat brighter than average for a moonless night.

The constellation Leo.  credit: SkySafariAstronomy.com

 Earlier in the evening I was experimenting with a 114mm GSO Cassegrain telescope and used it to image a few double stars.

Regulus A (center) and Regulus B.  GSO Cassegrain + Sony A7, ISO 400, 5 s.

 Regulus is one of the stars I recently photographed with a diffraction grating.

 I was reviewing these earlier data and suddenly realized that all seven Balmer-series hydrogen-absorption lines are visible in the spectrum of Regulus A, a detail that was previously missed.

 

A closer look at the short-wavelength end: 

Some more pictures from the same day, all with the GSO Cassegrain:

Mizar and Alcor. Sony A7, ISO 400, 1 sec.

Polaris A + B.  Sony A7, ISO 400, 1 sec.

The nearest star.  Sony A7, ISO 400, 1/800 sec. (Baader Astrosolar filter).

GSO Cassegrain solar photography