Thursday, July 16, 2009

Ob report on AstrOrdinary Camp'09 @ Pulau Ubin 20th June

Hello everyone!

I'm writing this ob report not only as practice for future ob reports in future but also to give other first timers a general idea of the observation site etc.

Met up with JY(Jun Ying) and 3 of his friends who wanted to go for the ob at around 5pm (20th June) at Changi village. Unfortunately, while we were unable to attend the afternoon activities, JY is a confident Bin trekker so we were confident of making our way to any campsite in Bin. Changi village has a ferry terminal where ferries cater not only to Pulau Bin, but also places such as Desaru. I didn't bring anything except for my laser pointer and some water, which turned out to be a mistake. The rest brought snacks like Top biscuits, Ritz biscuits, ice cold beer, and other random stuff like a DSLR and macbook. Thereafter to get to Bin you wait for a ferry bumboat where the captain waits until there are 12 people before setting off. The fee is $2.50 for a single trip, therefore a trip to and fro will cost one $5.00.

Upon reaching there we had dinner at one of the numerous eateries available. There are numerous eateries to choose from, generally at affordable prices. There were also many bike rental shops available for bike rental. As our original plan was to rent bikes, we asked around various shops for the rates and the general rate for rental of bike overnight was $6.00, per bike. After discussion however, we decided not to rent the bikes for 2 main reasons: a) to save money and b) there were some off-road gravel tracks with rough terrain and rocks that we were unsure the bikes could traverse. We also considered renting a van but we were not sure of the cost and we needed to know our route(via walking) to find our way back. Thus the decision to walk to the observation site was made.

The observation site is actually based on the northern site of Bin near Bubut hut near Kekak Quarry and Ketam Quarry (see map). Basically, it’s the OBS campsite beside Kekek Quarry. The site is around 4-5km away from the Pulau Bin Jetty start point and by foot, takes slightly less than an hour to traverse. The roads leading to the observation site have no signboards nor significant landmarks pointing to its direction for someone new to the island, therefore it is recommended that someone experienced lead the way should it be the first time the group is travelling to the ob site. (For us, it was JY in this case) The roads leading to the ob site also do not have any street lamps along the way, it is easy to get lost along the path once the sun sets especially nearer the end of the trail, when there are dirt trails(off road gravel tracks with rough terrain and rocks) and not paved streets. It is thus advisable to bring a torchlight in case one is unable to reach the ob site before nightfall. Also, there are no sources of potable water along the way, and also only 1 restroom stop. We managed to find the ob site even after nightfall due not only to the experience of JY but also due to the fact that a MP astro member managed to identify us. I will talk more about the observation site and the logistics involved later.

The observation site is actually a small clearing located in the middle of dense vegetation(trees). The clearing no longer has any grass due to previous campers clearing the error, making it a suitable place for placing groundsheets etc. as the insect count from vegetation is reduced. The vegetation provides a "perfect" cover from ambient city lights, such that the only light visible provided light discipline on the ground is the skyglow(light pollution) from Johor in the north and Singapore in the south. However the skyglow is prevalent enough such that the limiting apparent magnitude is around 4+, so Milky Way is not visible, even without cloud cover. The vegetation only rises about 30 degrees altitude above the horizon so it is acceptable.

Logistically wise, there is no food or potable water available nearby so one would need to bring their own. There is also no restroom nearby (the nearest one is over 2km away). There is also no shelter from the elements available nearby so a tent would be required in case of rain(debatable issue though, thankfully it didn’t rain).

When we reached the ob site there was actually major cloud cover. However, these were generally cumulonimbus or low-altitude clouds so I was personally confident that the wind would blow them over. We reached the campsite around 715pm, and while it was still dusk despite the major cloud cover several bright stars and objects could be easily identified, such as Arcturus, Saturn, Regulus, Castor and Pollux setting etc. However, at this point constellations could not be easily identified. The "weather" was hot and humid. The reception for handphone signals was also very poor, depending on the provider communication with the mainland was close to impossible. We also heard from the MP astro members that there was a fallen log blocking the dirt path to the camp site. Apparently the van carrying the scopes and other supplies had to stop at the fallen log (because it was impossible to pass through) and they carried all the scopes and supplies via hand to the ob site : / It is unsure at the point of writing whether NParks or OBS personnel have removed the fallen log.

Photo courtesy of Lim Jun Ying

MP Astro had brought 2 scopes, a 4.7 inch double element wide-field achromat(600mm f/l) and a 90mm(I think) triple element apo. While waiting for the clouds to blow over the the wide field achromat was set up and trained on Saturn. The seeing was really bad at the time so there was not much point in pushing magnification, at ~50X the rings could be seen, however Cassini division could not be resolved at the magnification. Detail was also not visible in the tiny disk at that magnification. Titan was visible on the far left of the planet.

The few of us engaged in casual banter and before long it was around 11pm. As expected the low-altitude clouds blew over and there was a improvement in the condition of the night sky (namely the transparency). For the first time in many years I was able to, with the help of Stellarium software in the macbook identify whole shapes of constellations in the night sky which would never be possible in the mainland. We managed to trace out, via the laser pointer, the kite shape of Bootes, square of Hercules and its arms and bow, the U shape of Corona Borealis, the "Pentagon" of Ophiuchus and even some stars of Draco. Corvus, Libra and the big dipper of Ursa Major were also identifiable. On towards the southern/eastern sky, Antares was rising fast in the sky and the shape of scorpius was readily visible to all, together with the teapot of Sagittarius. So were the southern stars of Centaurus, Crux, and Lupus. Faint constellations such as Norma, Hydra and Corona Borealis were sadly out of our reach. Still, I was very impressed by the increase in limiting apparent magnitude compared to any part of the mainland.

The wide field refractor was used by our human "goto" Siu Yung and I absolutely fell in love with the beauty of wide field views. A 40mm ep with 600mm f/l gave a magnification of 15X with a comparatively huge 4.7 inch unobstructed aperture. The Jewel box, or NGC4755 could be framed well within the eyepiece together with the blue-white view of Mimosa, which I had not seen with any other scope. The attention was then turned to M13, which was readily visible as a fuzzy white ball, but sadly unresolved. Moving on to M57, the ring nebula it was seen as a faint white small "ring" that contrasted against the background of pin-point stars. Unlike the mainland sky where I had to use averted vision, M57 was visible even with direct vision, an impressive feat. Thereafter we moved to M4, which was not as well defined as M13 (as it was also a globular cluster) but readily visible nonetheless. In the Takakhashi apo with smaller aperture it was noted that the image was dimmer, but that it had much higher contrast. I still have a long way to go as a visual connoisseur I guess! My guess is it would probably need a larger aperture to resolve. The open clusters in scorpius M6 and M7 were a sight to behold. M6, in the wide field refractor had a distinct butterfly shape. M7 was defined by a multitude of stars across the whole FOV. Indeed, clusters are best viewed via wide field refractors. :) Moving on to M22 the globular cluster again could again be seen as a fuzzy patch, like M4 and M13. The most impressive, however, was M20, where I could clearly see nebulosity in the trifid emission nebula.

As the hours passed the summer triangle of Vega, Altair and Deneb was clearly seen and the complete constellations of Aquila(which I never observed in mainland before) and Cygnus together with Lyra(also never seen the rhombus in sg before) were clearly visible. Sadly I didn't think of some objects in mind such as Albireo, the double double Epsilon Lyrae and M11 in scutum. It was 3 am and the sleep monster was getting to some people. In order to stay awake I thought of the ingenious idea to maintain constant conversation with the 4 of JY's group so that we would not fall asleep. Although one of them fell asleep, the rest of the 4 of us remained salient and were able to keep ourselves awake. Most of the rest of the people eventually fell to the temptation of the Z monster. In the night sky though, strange patterns which I had never seen before were rising in the east and due to the lack of the Macbook (asleep), I had trouble identifying them. Meanwhile, Jupiter rising from the East was extremely bright compared to mainland standards and seemed like a beacon in the sky. I managed to identify the great square of Pegasus but Capricornus and Aquarius around Jupiter was too hard for me to decode. The only other constellation I could decode was far north, the constellation of Cassiopeia, a wide M shape. With the scope trained on Jupiter, I was amazed at the level of detail seen, it even surpassed the C8 at NJC which I used to observe Jupiter with. Details in the bands were clearly visible, though apparently the GRS was not in view. All four of Jupiter's Galilean moons were visible.

If Jupiter was bright, then Venus would be a UFO. It was so bright that I felt it could almost cast a shadow. Under the scope false colour of the wide field refractor was finally very apparent, with the edges bleeding violet. Interestingly it showed a half phase of the moon, but no other surface features as expected. Soon, the crescent moon started to be visible above the treetops at dawn. For the first time, I could see the "earthshine" effect of the crescent moon(reflected light from the earth illuminating the night side of the moon) with the naked eye, which I rarely observed in mainland. In the scope, details such as Maria and craters were apparent in the night side of the moon, even though false colour was visible around the lit edges.

Brief overview of deep sky objects:

NGC4755: "A-shape" pattern of coloured stars (bright-blue and reddish-orange) clearly visible beside mimosa in wide field view

M13: distinct "fuzzy" patch, however unable to resolve cluster

M57: faint white "smoky" ring, able to be seen with direct vision

M4: faint "fuzzy" patch, also unable to resolve cluster

M6: distinct "butterfly" shape of bright-blue stars with orange giant BM Scorpii clearly visible, open cluster easily framed in wide field view

M7: Ptolemy cluster able to be framed in wide field FOV, entire field of densely packed stars (stardust effect)

M22: faint "fuzzy" patch, unable to resolve cluster

M20: nebulosity clearly seen in HII region (seriously wonders what one would see in a 12 inch scope under Mersing sky ^_^)

And thus, the observation ended. Really have to thank MP Astro for organizing this event and for lending us the groundsheet, allowing us to observe via their equipment etc, even though I felt very “paiseh” we didn’t help much in the logistical part. (for e.g carrying scopes to ob site and back, sorry JP!)

Ok several views(advantages/disad) on this ob, firstly I felt that this observation site is an excellent site for ob in SG territory. As mentioned above, the vegetation blocks all ambient light from the cities and only skyglow is visible should light discipline on the ground be maintained. Thus, should be used as an ob site as much as possible.

Furthermore, the views far surpass that of the main land. The clear naked eye visibility of the rhombus of Lyra and the visibility of nebulosity in M20 in a 5 inch scope have far surpassed that of my mainland experiences. Mainland locations are not only closer to the sources of skyglow(light pollution) but also have too much ambient light, which is a major cause of limiting apparent magnitude.

Last but not least, being part of Singapore territory, it is easier to plan such an event for students compared to overseas trips like Mersing or Desaru.

Disadvantages wise, I think a major problem is the issue of moving equipment from the paved roads to the beaten off-track graveled, rocky tracks, since both cycling and renting a van could have some problems travelling these roads. Also, the fallen log problem showed that they had to carry equipment quite a long distance from the van to the ob site.

Another disadvantage is the cost problem. The transport to and fro Bin costs 5 dollars per person, excluding food. Furthermore, as I mentioned earlier, it was a mistake not to bring insect repellent (I only brought water), as I suffered numerous insect bites(probably sand fly bites) all over my arms.

In summary though, this site has still the darkest northern sky in Singapore. Maybe NJ astro and other schs can organize a trip someday after exams!


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