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Observation 18 July 2017
Date: 18th July 2017 @ 18:50 – 22:20AEST
Equipment: 14” Skywatcher GOTO Dobsonian, Televue 11mm Nagler T6, Celestron 5mm, LV 7mm, Televue 2X Powermate, Televue 2.5X Powermate, Televue 3X Barlow, Baader Neodymium, Baader Contrast Booster.
Jupiter: At 19:08 there was a dark mark on the Northern equatorial belt, initially I thought that it was a darker area within the cloud belt but later using the “Gas Giants” app I found out that it was the shadow of Io. On the right side of the planet Io was rising, slowly moving away from Jupiter while observing for the next 30 minutes or so, not often does one experience a moon rise on a different planet. Europa was on the opposite side moving closer to the planet.
Ganymede and Callisto are further away from Jupiter on the right, same side where Io was rising and opposite side of Europa.
There was a substantial amount of detail visible within Jupiter’s atmosphere. There was cloud band shading and visible different coloring, lines and irregularities in the atmosphere. The most details visible was in and above the NEB, different colouring, from brown to yellow to even a blueish tint just above the NEB. The northern cap was slightly shaded but the southern cap was distinctly darker than the norther cap and easy to see with tiny spots on it, very subtle but definitely made the cap look slightly textured. Southern cloud belt was visibly irregular across the planet.
The GRS was not facing toward us until later at 21:27 but at this time Jupiter was low in the west, 20-30 degrees, not far from mountains so it was not as crisp as at 19:00 but still quite a bit of details are visible and a lot better than last observing session. The best magnification to use tonight is 300X initially than 150X to 235X when lower in the horizon to look at the GRS.
Saturn: At 22:02 Saturn was as high as it’ll be tonight and it looked crisp and detailed. The Cloud band on the globe was clearly visible, the Cassini division was visible nearly all the way around in the rings, the innermost ring to Saturn looked a bit darker then the others and there was a tiny visible shadow on the rings behind Saturn with 5 moons, Titan Enceledus, Tethys, Dione and Rhea orbiting it.
Magnified 300X and 330X the views were sharp and clean, whereas at 375X and 470X was a near crisp view as Saturn was overhead near zenith. 660X was softer with hints of Cassini division within the rings but its impressive with how big it is in the FOV.
To get Saturn to look so sharp, I was fine adjusting the collimation using the primary mirror while defocussing Saturn and adjusting until Saturn defocussed symmetrically in both focus travel directions.
Neptune: Neptune was the last object for tonight observation but it was just a blueish fuzzy dot, it was low in the eastern horizon, and I guess the lightning activity out to sea coupled with the picking up wind didn’t help. I Magnified it 300X, might have been bit much for it in the current position, but no matter what, I doubt that less power would show any more detail.
Mirrors might not be as perfectly collimated as I thought since when defocussing on Jupiter’s moons to fine tune collimation, were defocussing into a ring with the central obstruction in the middle but not defocussing “round” but more to what appeared to be oval, defocussed symmetrically but oval.
I think that the 14" SW still hasn't shown me the best it can do and I will need to play and practice with the collimation some more. Newtonian collimation is definitely a fair bit more involved than SCT collimation.
Thanks for reading,
Observation 11 July 2017
Date: 11th July 2017 @ 20:50 – 22:30AEST
Equipment: 14” Skywatcher GOTO Dobsonian, Televue 31mm Nagler T5 , Televue 17mm Ethos, Televue 11mm Nagler T6, Celestron 5mm, LV 7mm, Televue 2X Powermate, Baader Neodymium, Baader Contrast Booster, Circular polarizer.
Tonight is looking like it is a good night to do some observing and try out the new shroud for the Dobsonian.
The Seeing was quite stable, there were clouds flowing south to north direction but not so many as to ruin any observing.
The moon is just the second day past full moon phase and so still lights up the night sky, Saturn and Jupiter are in the sky along with the moon so knowing that I will not be looking at any DSO I decided to have a look at these three objects.
Jupiter: Jupiter was the first object on the agenda to view since it is already getting low in the western horizon, still 40 or so degrees but knowing that the best views are when the planets are highest in the sky, I didn’t want to leave it any later.
The view was a little hazy, the highest magnification where Jupiter looked OK was at max about 150X-235X. The GRS was visible just past the center of the SEB. To see it quite clearly I still had to wait for the fleeting moments of clarity, but it was constantly visible.
I didn’t see any fine intricate details with in cloud bands as in the past, and honestly even the polar cap shading was a challenge. Definitely no shadows from any moons on the Globe.
There were all 4 Galilean moons visible.
It was nice to revisit Jupiter as it is moving further away from us, even if the view was not even close to the best views I have experienced while observing Jupiter in the past.
Saturn: Saturn was the next in the cue, as it was right above head, near zenith, I was expecting to see Saturn more clearly than Jupiter. Initially Saturn was more stable, and the Cassini division was visible on the edges but not the best I have seen to date, even with the 8” SCT.
As I was adjusting focus on Saturn, when defocussing it a bit further out, I noticed that Saturn was defocussing asymmetrically, only slightly but asymmetrically so I knew that my collimation must be slightly out. I adjusted the collimation using a glass combination to give me 660X magnification until Saturn was defocussing symmetrically. At 660X Saturn was better than before collimation but still soft, so I dropped the magnification to 300X and the view was crisp and detailed, collimation was a major improvement.
I stacked the Neodymium and contrast booster filters on to the eyepiece and the view was breath taking.
During the moments of best stability and clarity, the Cassini division in the rings was visible nearly all the way around, became hard to see behind and in front of the planet. The rings in front of the globe were easily visible/distinguishable, along with the darkening on the globe, shadow cast by the rings on to the atmosphere. The rings were visible poking above the globe from behind, this is a good time to see Saturn with it’s rings fully open facing toward us.
The globe showed darker but still quite pale cloud bands, one just above the ring and the second more subtle shading about ¾ of the way toward the pole.
There were 5 moons visible, Titan, just barely visible Enceladus, faint Dione and Thehys and Rhea.
The best view of Saturn was at 300X-300X (11mm Nagler with 2X PM and 5mm Celestron X-Cel) magnification, the scale of Saturn was quite big with clear detail easily visible. Magnifying 470X was ok but obviously softer. Sure the planet was visibly bigger but I still preferred the view at 300X.
Moon: The moon, being just past full moon, only showed craters at one of the edges, but using the 31mm Nagler T5 or the 17mm Ethos, with the polarizer still looked amazing. The full face of the moon was visible at one time, the 17mm Ethos magnifying it so much and with the 100 degrees AFOV, I had to look around to see the edge of the moon… it was like looking out of a space craft window, it was awesome.
The 31mm Nagler showed the whole face magnified a bit less and while using both of the eyepieces, having the Polarizer turned down to the dimmest level revealed the moon ejecta streams, flat craters and Maria on the surface as well as bright spots dotted throughout the landscape, looking almost looking like city lights.
The Polarizer has to be turned all the way to the darkest level with the 14” mirror since without it is so bright that looking at it is actually quite uncomfortable. Even with the Polarizer, I think I could have added a ND filter to bring the intensity a little bit more.
Sure the most contrasty views where you can see a lot of detail in the craters is during a phase, but looking at the full, or near full, moon looks beautiful when adding the extra constant using darkening filters, bringing out the dark shading.
Overall the night of viewing was very rewarding, especially with the great views of Saturn.
The shroud seems to have done the trick at keeping the light path clear of any stray light, but the best part I found was that with the 3 fans blowing from behind the primary mirror, there was a slight, very slight air flow out of the front of the Dobsonian.
I’m hoping that this air flow will keep any dew from settling onto the primary or more importantly the secondary. A couple of months ago I took the 14” SW to one of my favourite dark sites in the mountains, but my observing night was cut very shot, very quickly due to dew fogging out my secondary, even when cleaning it with lens cleaner, the dew was already building up as soon as I took my hand away.
I have some dichrome that I’m planning to add to the secondary as a spiral on the back to create a dew heating system, but whether I’ll do that will depend on if the secondary will get covered in dew in a future observing trip with the shroud on while the back fans are moving air out.
Another things I have noticed tonight is that the order in which the Neodymium and Contrast booster filters are stacked makes a difference to how the view looked. Initially while observing Saturn, when I added the two filter, the view was not any more stable than when not using any filters, only slightly dimmer. But when reversing the order of the filters, the view stabilised noticeably, literally the difference was between OK and WOW.
I would think that each filter cuts out a certain wavelength of light and passes on the rest, and so it shouldn’t matter what order they are stacked.
I repeated the experiment but flipping the filters and same result, one way was not better than with no filters, but the other way it was stable and razor sharp???!!!!
Does anyone have an explanation to this phenomenon?
Thanks for reading, Clear Skies.