Expert: Jesse Martinez - 9/16/2009

Question
I read in your profile that you "rediscovered" the moons of Jupiter. with a small telescope. It sounds like an experiment I would like to try. I have a small telescope I got for Christmas, a Meade refractor, 70mm, with 27x and 78x eyepieces and a 2x barlow lens. First of all, could I do it with my telescope and second, how did you do it? If it is not too much trouble could you explain how you went about this. I would like a 5 level maximum detail.

Answer
Thanks for the question. I always like talking about this subject. First, your telescope is adequate. Some advice. You should probably forget about using that Barlow lens. The lower quality ones lower the contrast and definition of your view, which is not good for this exercise. I did 90 % of my observations with a 12.5 mm orthoscopic eyepiece, 72X on my scope, with no Barlow.

You would be starting at a good time for this study since Jupiter just passed its closest point to us in July. It is still a bright object and is visible starting at sunset, so you can get your observations in early. Oops, I’m saying too much. The greatest fun is finding the planet without charts or any other information. It does help if you know what it looks like through your telescope though. If you don't, this is what it should look like. At 78X, it is about the size of a quarter at five feet away. It has a peach or pinkish color and you should be able to distinguish about four belts at least, two in the north and two I the south. Every ten hours, its period of rotation, the Great Red Spot will drift across the view.  Now if you have seen Jupiter before, you know it is more like the “Faint White Spot”. If not, be prepared. The colors are vastly subdued compared to photos you have seen of the planet.

If I explained this in too much detail, you would lose out on the excitement of this exercise, so I will only tell you some basics and a little more. Get out every night you can and draw, or photograph the area. I think drawing is more fun, and that’s how the discoverer did it and that’s how I did it. Save your daily drawings and start making a master drawing. Record the dates and Universal Times of your observations on the drawings. This is VERY important. Every time you plot something, note the time on the paper. There are usually not very many objects in the same field of view with Jupiter at 78X except moons and an occasional star. After a few days you will start noticing that there are three or four objects in the area. They will all be in the same field of view with Jupiter. A few more days and you will notice the four objects have a specific brightness and maybe even color. If you are lucky you will sometimes see one disappear or reappear as they go in and out of Jupiter’s shadow. Make sure you note any such occurrences. You may even see one crossing in front of Jupiter, though with a small scope you might only see the shadow.

The key is keeping meticulous and detailed notes. Record all transits, occultations and possible eclipses of one moon by another. Make sure your drawings are to scale. After a couple of months or so, you should have enough data to “announce” your findings. Have fun. Write me again with the results.