Saturn Opposition @ Tiong Bahru Park with Giant Dobs

[cataclysm]

Tonight was a great privilege to view through 2 great instruments while witnessing Saturn's opposition. With such finely crafted instruments and above average seeing, we were looking at the planets at insane magnification!

Here among the proud owners: Richard Low (left) with his 15" Zambuto Mirror and Gavin (right) with his 12.5" Obsession.

[Gary]

Beautiful dobs, beautiful photos! Looking forward to the visual reports!

[antares2063]

Nice pics...can only imagine the views..:/

[rlow]

Thanks to Gavin's suggestion, we had an observation for Saturn Opposition on Sunday 11 May 2014 at Tiong Bahru Park, from 7:30pm to 10:30pm. Although only seven people turned up for this session, we had one of the best observation session for a long while.

Firstly, we have two of the biggest dobs in Singapore side-by-side targeting at Jupiter, Mars, Moon and Saturn. Gavin's 12.5" f/5 Obsession dob is definitely one of the most sophisticated dob in Singapore. It got all the bells and whistles: 12.5" OMI mirror, heated secondary mirror, the Servocat, Argo Navis, front and rear primary mirror fans, the whole works... dial and press buttons and the dob will automatically slew and locate an object for you. "All that is missing is a built-in coffee machine..." And to cap it all, the optical performance is nothing short of excellent. And then we also have the standard "no-frills" home-built dob with the 15" f/4.5 ZOC mirror, this time it was on the Roundtable equatorial platform.

Secondly the seeing was certainly exceptional that night. The 12.5" dob was cruising at 480x with the 10mm Delos and 3x barlow, while the 15" dob was doing 576x with the Leica ASPH Zoom and Zeiss Abbe Barlow operating at 2.6x. All those present had a great experience viewing the planets Mars, Saturn and the Moon as sharp and relatively steady images at these high magnifications.

On Mars at 576x, I could faintly see, next to the bright-white North Polar Cap (NPC), the detached ice region of Olympia Mensae at the following limb, while the NPC cleft mark of Chasma Boreale is just visible too. On the opposite side, Hellas Planitia was a faint frosty white like a false South Polar Cap. North of that, Syrtis Major was receding near the following limb. West of Syrtis Major, the crater of Schiaparelli was a prominent and distinct concave indent (Edom) at the joint of Sinus Sabaeus and Sinus Meridiani, it looks like a chicken drumstick that someone had bitten off a semi-circular chunk of meat.

Next to Mars, the Moon at 576x was a stunning sight. In particular, near the terminator, the view of the trio objects of craters Aristarchus and Herodotus, and the sinuous curve of Vallis Schroteri were nicely framed at 576x in the 80 deg. AFOV. We observed fine high-contrast details that are beautifully resolved juxtaposed against a subtle graduated greytone background and it was certainly a fantastic sight! Someone who took a look at this view said "Wow! I feel like I'm up there..." or words to that effect.

We also viewed Saturn at 576x sharp and steady, although it was only at an altitude of 45 degrees. Jupiter was viewed at lower magnification as seeing was not so good; it was located in the western sky which had turbulent atmosphere after the rain in the western part of Singapore. Overall I enjoyed the great observation session. And thanks to Kelvin for the lovely photos.

[bornfree]

awesome report! would love to have a chance to enjoy the view obsession has to offer for once.

[starfinder]

Thanks for uploading the group photos, Kelvin! Your superfast Canon (f1.2) prime lens is fantastic. To think that those photos were taken without flash in quite a dark setting. Very sharp too, with excellent colour.

Yes, it was a very enjoyable planetary session, with 2 dobs and a Tak apo.

I don't think I can add much to Richard's descriptions of what we saw, since it's so comprehensive. His knowledge and memory of the names of the Martian and Lunar features is amazing!

IMHO, the excellent OMI mirror perhaps held up against the Zambuto quality-wise, but the comparison showed that once again aperture wins as I could readily see more details in the features of Mars through the 15" dob. And the colour saturation was better too. I had my best views ever of Mars through that scope!

Let me explain the two fans for the primary mirror in my Dob: apart from the manufacturer-installed fan under the mirror (which is used to cool the mirror down, though that's not usually required in our hot climate), I recently installed another fan beside the top surface of the mirror, affixed to the mirror box. Its purpose is to produce a flow of air over the mirror, so that water moisture from our humid tropical air would not condense on the optical surface. Hopefully, that way it would prevent fungus from forming. This is a tip which I recently got from a mold expert. The fan runs throughout the day when the Dob is not in use, 30 mins on, then 30 mins off, then on again etc 24 hrs. I've also added another tiny fan for the secondary mirror, that's attached into the focuser when the Dob is stored. Both are computer fans that run on 12V DC via an AC/DC adapter.

Jupiter, Mars, Saturn and the Moon in one go.... a great astro session! Was also glad to show the planets to the passer-by Adrian and my friend Ethan, who saw them through scopes for the first time.

[Gary]

Rlow & Starfinder, thanks for the report! Saturn Moon close conjuction tomorrow night - less than 2 arc degrees apart. Go for it!

[Airconvent]

Goodness! The moon is so bright and round tonight and then I am reminded today is Vesak day, so its the 15th day of the Lunar month! No wonder its so round..its a full moon tonight!
Am glad to see the enthusiasm of the Singapore "double cluster"...2 Dobs surrounded my alots of people! Looks like it must have been perfect sight if even rlow can accept that it is the best seeing in a while.
And thanks to Gavin for clarifying its an f/1.2 lens for the group photo! Was wondering on the bokeh at that distant!
Keep up the obs guys!

[rlow]

IMHO, the excellent OMI mirror perhaps held up against the Zambuto quality-wise, but the comparison showed that once again aperture wins as I could readily see more details in the features of Mars through the 15" dob. And the colour saturation was better too. I had my best views ever of Mars through that scope!

We had compared the 12.5" Portaball with my 15" dob at dark skies of Sedili before. Some people had suggested before that there is not much difference between 12.5" and 15" but we are able to see quite noticeable differences between these two apertures in terms of brightness, colour saturation, and resolution in favour of bigger aperture. All other factors being equal, bigger aperture will always win. But bigger also equates to a heavier and bulkier scope. So actually I prefer the size, weight and convenience of the 12.5" dob.

[antares2063]

We had compared the 12.5" Portaball

Chee Chien's ?