Sunday, 24th Mar 2019

Jun 14 2017

NGC 4216 And Friends

NGC 4216

I haven’t posted any updates to my website in a while. Over the last few months I have been very busy with a host of different things: nevertheless, I have managed to do some imaging out in the field, and what I’m really short on is time to process raw data and publish results.

So, here I am catching up (well, sort of :mrgreen: ) with this image of the field around NGC 4216, an almost edge-on spiral galaxy. A member of the Virgo Cluster, this galaxy is located in the northernmost part of constellation Virgo, close to the border with constellation Coma Berenicis and is the brightest of a rather well-known spiral galaxy triplet: NGC 4216, NGC 4206 and NGC 4222.

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Jan 13 2017

The Integrated Flux Nebula (IFN) near M81 and M82

The Integrated Flux Nebula(e) is a complex of galactic dust nebulae that are illuminated not by a single star or a group of stars, as is the case with most nebulae, but by the energy from the integrated flux of all the stars in our galaxy, the Milky Way. The strongest color component is blue, but some reddish patches can also be found.

Since these nebulae are extremely faint and elusive, they are not visible to the naked eye, but can be detected only in long-exposure photos of areas of the sky located far away from the galactic plane. The brightest portions of these nebulae can be found at very northerly declinations, namely in the Little Dipper and the Big Dipper. The most photographed portion is probably the one close to the M81 and M82 galaxies, both thanks to its (relative) intensity and the proximity to the two galaxies, which makes for a very nice field of view.

Because of its very low brightness, the IFN calls for very long exposures, dark skies and very careful processing: for these reasons, it’s very hard to shoot. I already tried to image this part of the sky a few years ago, but didn’t manage. A second attempt made in late December 2016 was finally successful.

Since I’m no expert in processing this kind of objects, I had a very hard time trying to bring out the faint tendrils of the nebula. Moreover, the large field of view (about 4.1 x 2.8 degrees with a full-frame DSLR and a 500-mm refractor) produced some nasty gradients very difficult to tame during post processing.

Anyway, here you go (I strongly recommend clicking the image below to bring up a higher resolution version):

  Integrated Flux Nebula

Below is an annotated version of the image. Note Holmberg 1 (aka PGC 27605 or UGC 5139), an irregular galaxy shining at about 13th mag.

The IFN (annotated version)Main acquisition details: unmodified Canon DSLR at the prime focus of a Pentax 75 refractor (500 mm FL), 69 x 5 min. + 31 x 10 min. exposure time (totaling almost 11 h) at 1600 ISO. Processing in PixInsight and Photoshop.

My photo has some flaws, namely: the framing could be better (M81 is almost cropped out), the stars show some trailing and are a bit “splotchy” from heavy noise reduction. On the other hand, there is a whole lot of detail, so all in all I can be quite happy with the result.

Enjoy! :mrgreen:

Dec 14 2016

December’s Cloudy Moonrise

Wide-field moonrise

Moonrise on December 13th, 2016. Click the picture for a bigger version with all the relevant technical details.

Shooting wide-field is for sure not my specialty, but the view I was treated to on December 13th was just too beautiful to miss out on. Upon leaving the office, I saw a wonderful a rising Full Moon piercing through the clouds, low above the eastern horizon. The Moon was surrounded by a beautiful halo caused by thin cirrus clouds. Furthermore, all this was nicely framed between some barren trees which gave it a sort of an evanescent and mysterious look.

Just by chance, I happened to have my mirrorless camera along. Therefore, I pulled up to the side of a country road and started shooting, both short exposures to preserve details on the lunar disk and long exposures to capture the faint halo. Some technical details:

  • Sony A6000 mirrorless camera, 200 ISO, 1/2 s + 1/25 s exposures.
  • Sony 55-210 mm zoom lens @210 mm, f/6.3
  • My car’s hood served as a nice makeshift tripod :-)

This view reminded me of one of my favorite poems, “Canto Notturno di un Pastore Errante nell’Asia” (“Night Song of a Wandering Shepherd in Asia” by Italian poet Giacomo Leopardi:

“Che fai tu, luna, in ciel? dimmi, che fai,
Silenziosa luna?
Sorgi la sera, e vai,
Contemplando i deserti; indi ti posi.
Ancor non sei tu paga
Di riandare i sempiterni calli?
Ancor non prendi a schivo, ancor sei vaga
Di mirar queste valli?”

“What doest thou in heaven, O moon?
Say, silent moon, what doest thou?
Thou risest in the evening; thoughtfully
Thou wanderest o’er the plain,
Then sinkest to thy rest again.
And art thou never satisfied
With going o’er and o’er the selfsame ways?
Art never wearied? Dost thou still
Upon these valleys love to gaze?”

I really enjoyed this unexpected opportunity, and hope you’ll enjoy it just as much.

The takeaway from this experience? Always bring your camera along, ’cause you never know! :mrgreen:

Aug 17 2016

2016 Perseid Meteor Shower

The Perseid meteor shower in 2016 was expected to peak in the wee hours of August 12 with reasonably good observing conditions (Moon expected to set before the peak). As I was on vacation in the Greek island of Lipsi (Λειψοί), I could not bring along my full setup: instead, I had to make do with my Sony A6000 mirrorless camera (fitted with its ubiquitous 16-50 mm zoom), a small Cullmann tripod and a shutter release remote control.

Therefore, I headed out to a dark site, where I set up my rig and shot multiple 30 s exposures for about an hour, between 2:00 and 3:00 local time (23:00 – 00:00 UT) with the camera set at 6400 ISO and the zoom at the shortest focal length possible (16 mm @ f/3.5).

Out of about 140 exposures, one or more shooting stars were detected in 25 exposures, totaling 27 meteors, i.e. about half of what I managed to observe with the naked eye. These figures are not impressive, the problem being essentially the relatively narrow field of view. For such applications a wider field of view, e.g. such as the one offered by my Canon 6D DSLR + my 14 mm Samyang lens combo, is strongly advisable. Unfortunately, I could not bring a more advanced (but heavier) rig because of restrictions on baggage weight.

When back home, I picked out the shots where at least one meteor was visible, then I put them together in a composite in PixInsight and Photoshop. Here is the final result:

Perseid meteors

The meteors are visible in the image above as multicolor streaks (akin to a rainbow), which appear to be originating from a single spot in the sky, called the “radiant”, located in constellation Perseus. All in all I think the result is not so bad, given the less-than-ideal equipment used.

The most prominent meteors recorded are in the upper right quadrant (the one ending out of the field of view, most likely a fireball) and the one in the bottom right quadrant, closer to M45, the Pleiades star cluster.

Below is an annotated version of the above composite:

Perseid meteor shower 2016 annotated composite

Perseid meteor shower 2016 annotated composite

However, there is indeed much room for improvement. Lessons learned for next time:

  • The A6000 has rather low noise. However, 30 s at 6400 ISO sensitivity is too much even for the low light pollution levels of the most secluded Greek islands. 3200 ISO is more than adequate for this purpose, or shoot shorter exposures (e.g. 15-20 s).
  • Use a wider-field lens.
  • Get a better quality lens. The Sony 16-50 mm zoom is a handy all-round daylight photography lens, but is not suitable for astrophotography because of the many optical flaws (namely, vignetting and coma).

Anyway, enjoy! :mrgreen:

May 27 2016

The Transit of Mercury of 9th May 2016

Transit of Mercury

On 9th May 2016, a transit of Mercury across the Sun was expected to take place. It had been quite a while (thirteen years) since the previous one, which took place back in May 2003. Therefore, it was one neat chance to observe this event which, though less spectacular than other types of phenomena, is anyway quite interesting. Furthermore, the observing conditions were quite favorable for Italy and the whole of Europe (first contact at 1:12 pm local time, last contact around sunset, at 8:40 pm local time).

The transit of 2003 had been perfectly visible, since it had taken place in the beginning of a summer season which later went on to be one of the hottest and longest ones in decades. Unfortunately, the situation was completely different for this year, since the month of May started with very changeable and unreliable weather. The forecast for the 9th of May left no hope for Northern Italy and for most of Central and Southern Europe.

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Mar 27 2016

Deep down the Great Orion Nebula

It doesn’t happen so often to amateur astronomers to get their hands on a professional-class telescope. But it does happen every once in a while :mrgreen: .

On December 27th, 2015, I happened to perform some tests on the Telescope of the “Osservatorio di Fascia” (more info in Italian here and here), located in the Ligurian Apennines (Italy) at 1400 m elevation.

The main scope is an 800 mm f/8 (6400 mm focal length) ASTELCO Ritchey-Chretien, built in 2010-2011. It sits on an alt-az mount and has two Nasmyth foci for visual observation and digital imaging. After my testing session, I took the chance to point this big scope right at the core of M42, the Great Orion Nebula. A few tens of seconds’ worth of exposure was more than enough to capture the faint wisps of one of the most beautiful objects in the entire sky. Imaging camera was a SBIG STL-11000, more details available in the caption. Click on the image below to bring up a full-res version.


Before cosmetic cleanup, the original image had some strange patterns in the image, such as the ones shown in the close-up below. Of course they are not part of the nebula, but are most likely due to some internal ghost reflection.

Ghost reflections?

Ghost reflections?

Anyway, enjoy… and thanks for visiting! :mrgreen:


Feb 25 2016

M106 & Friends

M106 & Friends

Winter is coming to an end, so it’s galaxy season again! :mrgreen:

Constellation Canes Venatici (The “Hunting Dogs”) is home to a number of spring season gems, the most notable of which is M51, the Whirlpool Galaxy. However, there’s more to this small constellation than one can imagine, as it contains a number of other notable galaxies: M63, M94, M106, etc.

This time I pointed my telescope at M106, a SAB spiral galaxy lying in the northeastern part of the constellation. Shining at 9.1 apparent magnitude, M106 is known for its anomalous arms and is thought to have a massive black hole with a MASER in its core.

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Feb 15 2016

Comet Catalina’s “flyby”

CatalinaHeaderComet C/2013 US10 was discovered on 31 October 2013 by the Catalina Sky Survey, an automated system aimed at searching for asteroids and comets. As perihelion was expected on 15th November 2015 and the closest approach to Earth on 17th January 2016, the best “observing window” would be between late 2015 and early 2016.

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Dec 15 2015

Comet C/2013 US10 (Catalina)

Comet C/2013 US10 (Catalina)

This past weekend (December 12-13) I headed out with some friends to a dark sky location in the Alps at almost 2000 m elevation. We spent two nights imaging/observing, which were partly ruined by thin cirrus clouds rolling over Northern Italy for most of the time.

Needless to say, Comet C/2013 US10 (Catalina) was one of my planned targets, but it turned out to be harder than expected to image, because of the cirrus clouds and the comet being quite low (~ 20°) above the eastern horizon. That’s why even a 50-minute exposure (guided on the comet’s head) barely shows the two tails: the ion tail (pointing at about 11 o’ clock) and the dust tail, pointing at about 4 o’ clock.

The image is B/W only because I concentrated on the luminance given the poor observing conditions: BTW, the raw frames are plagued by quite strong gradients. Some data: 5 x 10 min = 50 min. total acquired with a Moravian G2 8300 FW CCD through a Pentax 105 SDHF refractor; more data available in the caption (click on the image to bring up a slightly bigger version and the caption).

Nov 12 2015

Avalon M-Zero Mount and StarGo Motor Drive

mzero-15 German Equatorial mounts are probably the most popular type of mount, available in a wide range of builds, load capacities and price. This wide variety is somehow “reflected” in performance, but the basic features and principles are pretty much the same.

Not many alternatives to the German model are available, mainly in the form of the traditional double-arm fork mount. A few years ago, Avalon Instruments, an Italian-based astronomical equipment maker, came up with a sturdy single-arm fork mount, the Avalon M-Uno, which has had good success. The concept of a single-arm fork per se is certainly not new, but is nevertheless not so common in the mid-range market sector.

In early 2014, a more compact version of the M-Uno came out, called M-Zero. While Avalon mounts were previously based on the Skywatcher Synscan system, the M-Zero was the first model to be natively equipped with Avalon’s own motor drive, the “StarGo”. This new drive and mount combo caught my curiosity, so it was not long before I came up with the idea of doing an in-depth test. My proposal was keenly accepted by Avalon’s owner, Luciano dal Sasso, who provided me with a sample.

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