To read about the Sossusvlei Desert Lodge, activities available as well as the astronomy equipment available and the first three nights of observing, please click here for Part 1 of Stargazing in the NamibRand Nature Reserve.
The early wake-up call for the trip to the giant sand dunes of Sossusvlei, which is about a 6 hour round-trip, meant I caught up on some much needed rest for a couple of hours just after lunch. After a few successful nights of observing with the LX200 I decided to enjoy some wide field stargazing so set up the Takahashi FS-60Q in front of the villa in the afternoon and waited for darkness to fall. The list of targets included several that had already been observed in the previous couple of nights but many of them would take on a very different appearance with masses of sky visible around them thanks to the 2.6o field of my 24mm Panoptic.
I started in the west in the Carina region and worked my way across the sky, following the delicate light of the Milky Way like a road leading me to Saturn and Mars in the east. The highlight among the numerous DSOs was certainly the Carina Nebula. The ability to view the full 2-degree extent of the emission nebula was a transformative one. Even in the 2.6o field of the 24mm, there was very little sky left that was not glowing, with the distinctive dark lanes that criss-cross the nebula very apparent as were several of the small open clusters that are wrapped in the glowing hydrogen of the nebula.
Mars in particular was a target I wanted to take advantage of. The recent opposition was not well placed in the UK with Mars struggling to reach an altitude of 20 degrees above the horizon and hence fine detail almost always being washed out by the turbulent atmosphere. Fortunately, Namibia did not suffer such problems. Mars was still presenting a disc of more than 18” when we arrived and during the course of the night would reach an altitude of 86o. The red planet often teases with low contrast albedo features and can prove challenging for a fast focal ratio doublet. Previous attempts to view Mars with the Tak FS-60 had always proved to be bit underwhelming. However, this time I came prepared. I had also brought along the 1.7x CQ module which screws in behind the objective and converts the 60mm f/5.9 doublet into an f/10 quadruplet. The performance of the scope was transformed. Previously a slightly woolly, soft image had presented itself to me, but now, combined with high altitude, Mars showed plenty of features which I had never seen in such a small scope before. The view left me feeling that the CQ module was a wise investment, correcting the one glaring weakness that had previously manifested itself.
Rather pleased with the views I had enjoyed in the early evening, I turned my attention to the most important event of the holiday, and arguably my life. The first vacation away with my girlfriend in 2011 was to Namibia and we had concluded that amazing trip with a wonderful four night stay at the Sossusvlei Desert Lodge. Almost five years later, it seemed like it would be the perfect opportunity to ask a question. I called Charlotte outside suggesting that it was an exceptional night and she should have a look through the telescope. I led her on the same path I had just followed from the west to east with Saturn the final target. Once Saturn was centred in the eyepiece (showing a remarkable amount of detail for a 60mm telescope), I stepped aside. In all previous viewings of Saturn, I have always tried to encourage her to spot a moon or two whereas her attention is understandably, focused on the rings. This time when I wanted that attention on the rings, the excited statement of “I can see a moon” was being uttered. Attempting to direct the focus back to rings, while down on one knee behind her, by stating how beautiful they looked, I heard a brief mumble of agreement before her head began to rise up from the eyepiece. Now was the moment. Perhaps a bit cheesy, as she turned to face me I said (possibly paraphrasing myself) “I have just shown you the most beautiful ring in the universe, perhaps now I can show you the second?” The answer was an immediate yes, but it really is so dark in the NamibRand Nature Reserve that she could not actually see the ring! So we headed back inside where I slipped the ring on and luckily it was a perfect fit.
After dinner I made my way up to the observatory again (yes she really is that understanding – I am very lucky!) with a new hit list of targets for the next few hours.
First up was a rather spectacular globular cluster in Ara. NGC 6397 (Caldwell 86) is the fourth brightest GC found anywhere in the night sky (only Omega Cen, 47 Tuc and M22 are brighter) and it is the second closest to the Sun. Perhaps its biggest claim to fame is holding the top spot among Milky Way globular clusters for brightest individual stars at around magnitude 10, something I confirmed later that week with a look through the 60mm refractor. The cluster subtended about 15 arcminutes visually with a fairly dense core of approximately 3’ across, which is unsurprising given C86 is core-collapse globular. As well as the dense core, I found my eye was drawn towards several streamers of stars that seemed to peel away from the core, almost like cometary tails.
Changing tack from one of the oldest objects to be found in the night sky to something much younger, we moved onto the emission nebula M17 in Sagittarius. One of the brightest nebulae visible to northern observers, it is also rather large at around 40 arcminutes on the long axis, so we used the 27mm Panoptic which just about took in the entire nebula in a single field. The bright, long bar immediately draws the eye before it wonders towards the hook of glowing gas that gives the nebula its name of the Swan. Under such dark skies, closer inspection the “neck and head” actually revealed that it is an entire loop of gas which connects to the main bar though its glow is far fainter than the distinctive neck feature. Above the body of the swan, more rarefied glowing gas seems to form a partially extended wing as though the swan has just come into land on the celestial river of stars in this crowded region of the sky. One other noteworthy feature was the apparent absence of stars inside the loop of material that forms the neck, suggesting the presence of a dark nebula. The Swan is an object I wish I was more familiar with, but sadly its declination means it is never that well placed from the UK.
Leaving the Milky Way completely we moved onto the Grus Quartet. Located in the Crane, about 1.5o from Phi Gruis, the four components are NGC 7582 / 7590 / 7599 / 7552, though for us and the fields we had available, it would actually be the Grus Triplet. Using the 17mm Nagler, three galaxies (7582, 7590 and 7599 are contained in area only 10 arcminutes across. The four galaxies lie around 60 million light years away and are physically very close together and strongly interacting. Two of the members, (7552 and 7582) exhibit strong starburst activity, likely due to gravitational tidal interactions. NGC 7582 is the brightest of our “triplet” extending about 3’ on the long axis in a thin spindle with a fairly obvious core and what appeared to me at least, as some mottling and structure in the disc which may reflect that aforementioned star burst activity. Both 7590 and 7599 were less interesting with a delicate increase in intensity in 7590 near the centre for a stellar looking core whereas 7599 was a rather featureless, amorphous needle of light. However, to see three edge on spiral galaxies in such a small field of view was a wonderful sight and in our haste we forgot to slew 30 arcminutes to observe the fourth member of this famous quartet.
Returning to the Milky Way, our next quarry is arguably the most famous planetary nebula in the night sky, the Ring Nebula located in Lyra, the celestial harp. The last hurrah of a dying solar mass star, the rapidly expanding envelope of gas is ionised by the ultra-violet radiation emitted by the central white dwarf, causing it to glow. Beautiful in only 3-inch scope, showing the distinctive smoke ring shape that gives the PN its name, M57 is truly spectacular in a 12” scope under a dark sky. The torus of nebulous material starts to exhibit plenty of structure at this aperture which is revealed so spectacularly in long exposure photographs. While looking for the central 15th magnitude star (which we bagged) the hole in the ring was obviously glowing gently, something I have not really noticed previously. I suspect my attention is normally focused on the beautiful ring itself while ignoring the centre. Inserting an OIII filter made the central condensation inside ring very obvious and obscured the central white dwarf from view.
The final target of the night was a transient interloper to the inner solar system, C/2013 X1 Panstarrs. Anticipating that the comet would be well placed for viewing in Aquarius in the hours after midnight, I printed a star chart before we left showing its position each night for the week of our stay. Rather excitingly, the comet passed only about 30 arcminutes from the Helix Nebula on the night of Saturday 4th / Sunday 5th, sadly the day before we arrived. However, a quick internet search shows many astro-photographers took advantage of this chance alignment. Using the star chart, David hunted down the comet in his small binoculars by hoping from one distinctive grouping of stars to another before we slewed the scope to the same position. That actually proved to be slightly harder than expected, and took a few attempts before we managed to centre the comet in the eyepiece. Showing a defuse, grey-green hued coma with a slight condensation at the core, we also detected a faint, fairly stubby tail at the one o’clock position.
Another early start for the rescheduled hot air balloon ride meant once again observing wrapped up around 1am allowing me just under four hours sleep. The limited amount of rest over the last few days certainly seemed worth the sacrifice as we quietly soared over the giant, twisting dunes below that morning.
Thursday turned into a bit of a galaxy marathon, mostly in the Virgo and Coma Berenices region of the sky. During the course night we observed dozens of galaxies, with many of the highlights glimpsing multiple galaxies in the same field of view.
During galaxy hunting season, many amateur astronomers will spend a great deal of time cruising among the Virgo Cluster which lies 55 million light years away, but our first destination was almost six times further in the Coma Cluster. Just being able to glimpse light that started its long journey to my retina 300 million years ago is remarkable, but actually detecting hints of structure just elevates the experience to whole different level. Hopping 2.5o from Beta Comae Berenices, C35 (NGC 4889) is one of two enormous elliptical galaxies that dominate the centre of the cluster. C35 is truly a giant and maybe the most massive galaxy (estimates of 8-15 trillion solar-masses) within 100 mega-parsecs of the Milky Way. Visually, the galaxy is slightly oval, extending about 3 arcminutes on the long axis which implies a diameter of around 240,000 light years, though a defuse halo, seen in photographs, extends to half the diameter of the full moon, translating to 1.3 million light years! Like most elliptical galaxies, the defuse light is mostly uniform across the galaxy, though it gradually brightens towards the centre as a sharp point. While attempting to tease a little more detail with averted vision, numerous other tiny smudges of light would appear in the periphery of my vision, immediately drawing my gaze, only to vanish as others would appear in another part of the field. With more than 1,000 members in the Coma Cluster, it is almost inevitable that every field will contain many ethereal smudges of light.
Using our visual warp drive that the USS Enterprise would be envious of, a quick slew of the telescope brought us 250 million light years closer to home in the middle of the Virgo Cluster. Using the 17mm Nagler, we centred on M84 and M86. This whole area is packed with Messier galaxies. I imagine all these faint light sources would have proved rather frustrating to the comet hunters of the day. While the field was dominated by the two Messier galaxies, two other smaller galaxies were immediately obvious with direct vision. A quick check with a star chart identified these island universes as spiral NGC 4402 and elliptical NGC 4387. We the followed the remainder of the Markarian’s Chain of galaxies through to NGC 4477, a small, slightly oval galaxy with a stellar nucleus at the centre.
We spent quite a bit of time in Virgo, just manually moving the scope around with no particular target in mind just to see what we might stumble across. With such dark skies and a good sized aperture, almost every random field had numerous little ghostly apparitions to study and enjoy. We did of course run into some famous, old familiar friends, including one of the most photogenic galaxies, M104, the Sombrero. The initial view was stunning. My eyes were immediately drawn to the fairly bright, large halo of light, yet very quickly switched the thin, dark needle that bisects the long axis of the bulge. Spending a bit more time with this beautiful galaxy, the dark lane of material started to offer the perception of detail with mottling and structure which is revealed so well in the long-exposure photos.
Changing tack, we heading back into the Milky Way to take in a variety of open clusters, nebulae and globular clusters. A real highlight of the remainder of the night was the emission and reflection nebula, Caldwell 68 (NGC 6729), located in Corona Australis. NGC 6729 is a small 1 arcminute long reflection nebula which appears as detached piece of nebulosity from the larger emission nebula NGC 6726-7. That in itself does not sound like a spectacular sight, but as is often the case, for me at least, the view can take on extra significance with some knowledge of the object. Photographic time sequences of this little reflection nebula shows it changing shape and structure over time scales measured in days, which is physically impossible given the actual size of the nebula. While brightness variations can be attributed the variable nature of the star that illuminates this clump of dust and gas, it has been concluded that shadowing effects from moving clouds that lie within 1 a.u. of the star cause the observed changes in structure. A similar process occurs with Hubble’s Variable Nebula which I very tiredly confused with a comet (not the first, won’t be the last) during my stay here in 2013. The view itself was perhaps what a child would draw if you asked them to sketch a comet. At high power, a delicate fan of material seemed to extend away from a bight nucleus, which seemed to have tiny streamers which merge with the blackness of space. An interesting project would have been to sketch C68 on the night we arrived and again on the final night to see if we could visually identify any change in the apparent structure. Perhaps next time…
Our first object of the night was a rather elusive one. In fact, so difficult is it to spot that it was not even identified until the 1970s, and as such has the catalogue number PGC 19441. Located 3 degrees from Canopus, the Carina Dwarf Galaxy is an 11th magnitude galaxy with measured dimensions of 30×20 arcminutes and is so diffuse that long exposure images of the region actually reveal background galaxies that shine straight through it. At a measured distance of some 326,000 light years, the actual long axis of the galaxy is 9,200 light years wide. I rated our chances as slim to none (I have looked at ESO observatory photos previously and am not convinced I could see anything) but we used the 27mm Panoptic to take in as much sky as possible. What we saw was perhaps a slight increase in the concentration of the unresolved light of the uncountable background stars that make up our home galaxy, but this very well could have been a case of averted imagination.
Reviewing my observing notes, the rest of final night turned into a bit of Caldwell marathon, taking in several objects I have not observed before, starting with C100 (IC 2944), the Lambda Centauri Cluster. Located between the Carina Nebula and the star Acrux in the Southern Cross, the cluster has an interesting past of being mislabelled/misidentified, including by Sir Patrick Moore himself who incorrectly referred to it as the Gamma Centauri Cluster in the original 1995 published Caldwell Catalogue. The cluster itself is quite pretty, with a loose spread of stars sprinkled over the blanket of an associated emission nebula (IC 2948) which is known as the “Running Chicken Nebula.” While revealed in stunning detail in long exposure photos, the nebula itself is quite faint visually and the cluster was not as bright as I expected based on the integrated visual magnitude of +4.5. Lambda Centuari itself skews that value considerably.
The next object on our hit list was C98 (NGC 4609) an open cluster in Crux which actually sits in the Coal Sack Nebula. I would argue that the Coal Sack is the most interesting dark nebula seen with the naked eye. There is just a complete absence of light which sits in stark contrast to the surrounding ethereal glow of the rich Carina region of the Milky Way. There is only one naked eye visible star in the entire Coal Sack, which measures 7o x 5o, making that magnitude +5.2 naked eye star, BZ Crucis, rather conspicuous. That star proves to be useful marker as it sits on the edge of the 13’ wide open cluster. The view itself was pretty unremarkable, leading me to wonder why Sir Patrick would have selected it for such a visually impressive list of DSOs. We observed a few dozen stars, the brightest of which were around magnitude +9, loosely arranged with no obvious pattern that so many open clusters seem to elicit in the mind when observed. Arguably the most interesting fact about this small cluster is it is actually more distant than the Coal Sack itself, with its star light being considerably reddened by the cold dust of the sack.
One has to feel sorry for some DSOs. Spectacular they may be in their own right, but due to the unfortunate circumstance of their immediate location to something even grander, they become the neglected poor relation that no one wants to invite over for Christmas dinner. M92 certainly does not get as much attention as it might thanks to the presence of M13. How many beautiful open clusters in the Perseus / Cassiopeia region of the sky are routinely ignored thanks to the majestic Double Cluster? Caldwell 84 (NGC 5286) is another such victim. It is a large (11’), bright (mag +7.3) globular cluster. With such characteristics, it is brighter than about 50% of the Messier globular catalogue, yet it is located just 5 degrees from the biggest and brightest of them all, Omega Centauri. The view of the cluster itself was very pleasing. It resolved nicely to a fairly bright core approximately 2 arcminutes in diameter and had the appearance that several spiral arms of stars were radiating away from the denser central region. C86 is definitely worth a short detour if you spend some time observing its more famous, nearby cousin.
Every time I head south for an observing trip I find my attention constantly drawn towards the Scorpius / Sagittarius region of the sky. Not only are they two beautiful constellations, but they are jammed with wondrous deep sky objects which are always tantalising out of reach or unable to show their best from the UK. Once again I found myself suggesting another DSO in Scorpius and a quick input into the Autostar II control pad sent the scope off to the open cluster NGC 6124 (C75). The cluster measures 30 to 40’ across (depending on source) so we needed the 27mm Panoptic. It was rather unusual in appearance. All of the stars are rather dim with none exceeding magnitude +9 and relatively well dispersed with a tighter concentration near the centre. But what stood out was an arc of darkness that bisects the OC, where there virtually no cluster members at all, such that one could be convinced there were actually two clusters in the same field of view.
Pavo, the celestial peacock, contains a couple of DSOs that would certainly be worthy of inclusion on the beautiful tail of any peacock, and C93 (NGC 6752) was to be our next destination. At magnitude +5.4, this cluster can be seen naked eye as a slightly fuzzy star. This GC boasts some impressive stats in the ranking of globular clusters. It is the fifth brightest, and is second when they are ordered by the brightest stars contained within it. It is also among the easiest to resolve. C93 is also one of the best examples of a core collapse globular and that is the immediate impression that greets and observer. The central 3’ core is very intense but seems to brighten even more so, almost like a nearby, solitary field star sits right in front of the centre of the cluster. Moving away from granular halo that enrobes the bright core are multiple arms of stars that sweep in gentle arcs, something that is not seen in long exposure photographs. This perceived structure not captured in images is one of the key qualities than can make visual observing of globular clusters so rewarding.
Several late nights and early wake up calls finally caught up with me and I had to call time on the final nights observing earlier than I would have liked. We finished with a north versus south match up. How would the plucky contender from the north hold up against one of the heavyweight champs from the south? It was to be a very one-sided contest with a series of damaging blows landed by the champ. Impressive as M13 is, it just cannot compete with the splendour of 47 Tucanae. With his tail between his legs, the Hercules cluster was sent packing and told to leave the “Great” moniker behind. It was a reminder once again how lucky our southern hemisphere astronomer cousins are and left me thinking about when my next trip south would be.
Another week spent in the NamibRand Nature Reserve did not disappoint. Notwithstanding impressive thunderstorms during the course of Monday night, conditions were excellent and the amount of stargazing exceeded my expectations and the number of new DSOs viewed really made the trip worthwhile. As always, the hospitality, food and daytime activities at the Sossusvlei Desert Lodge were fantastic and made this a trip to remember.
Having visited the lodge so many times, we have grown to know management quite well and during one discussion it was mentioned that they are considering upgrading the telescope to something a little larger, though this will be dependent on budget considerations at their financial year end. Both David and I pitched the idea of an 18” plus Dobsonian telescope. Such an aperture upgrade would transform the already wonderful telescopic views on offer. If the upgrade does happen, I can promise I will immediately be planning my next trip to Namibia and the Sossusvlei Desert Lodge.