Thursday, January 27, 2005

The short Jupiter observing project

Date: 8-Nov-98 to ...
Time: 0:10-0:30a

This short project is defined based on the fact that Jupiter will pass into my observing window at my home every night approximately during the above time period. So, it is so convenient for my to observe it without going out. Apart from this motivation, I can obtain more experience on observation and this is possibly a good step to begin
with some more serious observation. At the same time, I could get more knowledge on my Ranger to see what is the best way to upgrade it with more accessories. Lastly, planets may be the only possible targets for city observations.


Today, the air looked steady, however, when going up to 152X, I could notice that it's not the case. I should say, I could detect every bits of the observable detail at 76X and by going to 152X, I just get a bigger image.

This time, I could make out the three major belts and a hint of some minor belts at 76X. By going up to 152X in the hope of getting a better image, I still couldn't sure the existance of the minor belts. I suspected that I have seen the Great Red Spot as well, but I was not sure about it. At least it must be some kind of storms in the
Jovian atmosphere.

At 152X, the image sharpness varies over time due to unsteady atmosphere. At 76X, the detail seems a bit too small for my eyes. I guess I need something around 120X (20mm + 5X Powermate), and something like 180X for an even larger image.

Tonight, I understand that stable and good breathing is one of the key to observe more detail. People tends to hold the breath when the view is fantastic.


I planned to use my C90 for observing tonight, but thing goes wrong.

Nothing goes wrong with the sky and my scope, but it's just that I've missed the view since I've got a phone call at that time. Anyway, I got the 50X view before the Jupiter disappears. Maybe tomorrow.

Before the Jupiter appears, I've tried to test the C90 again with various eyepieces, with or without the barlows. I've conducted the test with the brightest star available in my observing windows, but I can't identify the star and I guess it's not important.

At up to 100X, the star image is still okay. However, by going up to 159X with the 6.3mm Plossl, the image becomes very dim and slightly blurred; and by inserting the barlows, the 317X image seems couldn't be focused and it remains as a fuzzy light patch.


Tonight, I've setup my C90 to wait for the Jupiter to come in. As expected, it appeared 3 or 4 minutes earlier when compared to that of the first day I observed it. The sky was not as clear as before and it looked pink.

With the C90, I could see the belts on the planet surface at 50X, with a little bit difficulty. I guess I couldn't see them when I still haven't got my Ranger, maybe experience has been improved.

(March 1999 insert: I guess that's more because of the fact that that time I was observing at home, and the C90 could have been rearch thermal equilibrium, while I didn't notice this problem before, when I was observing outside. Still remember that the cloud belts were obvious, and it should not be a problem of experience, of being able to see it or not, at least it is possible to detect them by any untrained eyes)

At 100X with the 20mm Plossl with barlows, the cloud belts were clearer, but still not as contrasty as the Ranger at any magnifications which were enough for making out the belts. Pushing it up to 159X with the 6.3mm makes a bigger and more fuzzier ball, further trying it at 317X, I could not get a clear image at all. I've also tried
to observe at 62.5X, with the 32mm barlowed, not bad.

I switched to the Ranger before the Jupiter went out of view, the views are more constrasty and the cloud belts appeared to be more clearly. I conclude that the Ranger is by all means better than the C90, and the image remains bright up to 152X, even the light gathering ability is not as good as the C90. And with the same seeing conditions, the Ranger outperforms the C90, however, at the about 2.5 times the cost.


The Jupiter appeared two minutes earlier than today, and it fit nicely with my prediction. There was nothing planned except trying to remove the lens from the barlows to thread them directly into the eyepiece barrels. As expected, the magnification factor was reduced, which is not bad. I guess I have to check the magnification of that configuration to allow a more flexible range.

Tonight, the seeing condition was not as good as it looked because I could see the "boiling effect" in the image of Jupiter at 48X. Occasionally I could see the belts. Increasing to 76X, the image didn't improve but it's as expected; and 152X was totally useless.

I remained at 76X for most of the time, and soon I discovered some glares along an axis, and I tried to rotate the eyepiece in the focusser and I conclude that it's not due to the defects of the eyepiece; I switched to the TV Plossl and the problem remained;
and I didn't know why.

Until this morning, I guess that it must be due to the straying light outside my viewing windows. Let me check if I could make a glare shield to improve the situation.


I rushed back home today for the Jupiter, and it's already there when I arrived home. I setup the scope quickly within one minute and begin to look around. At 76X, I could already notice that the air were moving like a stream in the river. I raised
the power up to 152X and wait when the turbulence to stop for a while. Yes, it stopped occasionally and I could see more.

Anyway, I tried to train my averted vision. I found that I could see better when I look at the right of the target. And I found that the glare can be eliminated and rotated by wrapping the hand around the lens cell.


Either the weather or my time didn't allow, and I've paused for quite a while. Tonight, the satellites of the Jupiter are aligned at one side of the planet and I counted four of them. The air is not that steady, boiling water effect can be noticed at 76X but I could still get some steady views at 152X occassionally.

Some ideas about observing: I've tried to shrink a picture of the Jupiter (from HST) in the computer to model the view in a telescope. However, I found that I could hardly detect three cloud belts with an image of similar size to my telescopic view at 152X. Maybe the resolution of the monitor is not as good as the Ranger. Originally, I would like to try out the optimal power (or minimum power for more detail) by this method,
but obviously, it sucks.

No comments: