Thursday, January 27, 2005

The Second time looking at Saturn at home

Last time (and it's the first time) when I tried to observe the Saturn at home, I've tried to use the 6.3mm Celestron Plossl with my Ranger on the Saturn and I found there's no improvement on the detail, when compared with the view with the 20mm Tele Vue Plossl with the Orion Shorty barlow (76X vs. 48X). I prefer the difference as a result of the seeing condition rather than the quality of the eyepiece.

This time, I have brought out a chair for the observation, setup everything in a more comfortable manner. The sky appear to be pink, which was a sign of severe light pollution with a thin layer of haze. Never mind, the Saturn is just ahead near the Zenith, which is the only observable location from my home. With naked eyes, nothing other than the Saturn was visible. Bad? However, it is the astronomy in Hong Kong.

Without hesistation, I tried to point my scope to it but it's a kind of difficult. I installed the Celestron Star Pointer and turn it on, align the red dot with the Saturn. Okay, it was inside the eyepiece. At 24X, the Saturn appears to be an elongated star, and with imaginations, I could make up the ring. By inserting the barlow, the ring stood out. A nice view to me, even after watching it through the scope for many
many time.

I tried to insert the 6.3mm Celestron Plossl to get 76X, this time, the view was good. It is certainly more contrasty than that with the C90 and 12mm Celestron SMA. This time, I clearly saw that the dark gap between the planet and its ring. I tried to see if there're some cloud belts observable on the planet surface. I was not quite sure this time, but I guess I could see two of them. By pushing it to 152X with the barlow, the view was a little bit better, but I wonder if it's just the result of a larger image or not. I still couldn't make sure if I could see two cloud belts or not.

A good finding in this observation is that, the Celestron Plossl is not that bad in terms of clarity of the image produced, but the eye relief is really terrible, it is essentially zero. To have good eye-relief, I guess the only way to go is to buy those really expensive ones like Pentax SMC XL or the new Tele Vue Radian, or to buy the Tele Vue 5X Powermate to couple with longer focal length eyepiece.

After this observing session, I found that focusing at 152X would make the telescope shaking but the Manfrotto (Bogen) setup can become steady within one or two seconds, so it is nice. Tracking is no problem as well. However, I discovered that the draw-tube design of the Ranger is not so good, since when using the Ranger for objects near the Zenith, it tends to move, I wonder if I could use those heavier eyepiece with it or not. I don't want to over-tighten the screw.

My present estimation is that, I should not push the Ranger to over 200X for the steadiness of the view and something around 120X to 160X should be the optimal high power range.

23:00-23:30, 6-Nov-98

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