28 replies to this topic

[vtornado]

Jupiter can be very bright and dazzle the eye, making the faint bands difficult to see.   I would try around 150x.  Try observing with a white light shining on your head.   You can leave an outside house light on.  I have a small LED camping lantern that I let shine on my profile.

[KBHornblower]

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Ah, but experience.  That's something that beginners tend to overlook.  Three true stories:

 

1) One night I was observing Jupiter with a 250mm telescope (yes, larger than your telescope, but keep reading).  A shadow transit of one of Jupiter's moons was in progress.  My son (inexperienced in using telescopes) came for a look.  He was unable to see the small, dark shadow of the moon on Jupiter's bright clouds.  I described precisely where to look for the shadow.  My son looked again, but still could not see it.  I made a quick sketch for him to use as a reference.  But still, he was unable to see that shadow -- which by the way was glaringly obvious to me.  Experience vs. Inexperience.

 

2) One night I took a 102mm telescope (smaller than your telescope) to a school to show the students some celestial sights.  Jupiter was one of our targets.  Upon pointing the telescope at Jupiter I immediately noticed that once again, a shadow transit was in progress (They occur frequently with Jupiter and its Galilean moons).  But this time, after that experience noted in #2 above, I didn't inform anyone of the transit.  Instead, I requested each person to carefully describe all that they noticed on Jupiter.  No one mentioned seeing a tiny black dot on the planet.  Experience vs. Inexperience.

 

3) One evening a young guest (who eventually became and adult and gained employment with a major planetarium company) was with me when I was working on an observation and sketch of Mercury.  I was working on the shadings of albedo (lighter and darker) features that I could see on the planet.  When asked if he could see those features, I was somewhat surprised by his response.  He stated that he couldn't even see the planet's phase -- again, something that was obvious to me.  In fairness, the seeing conditions were not very good, but an experienced enough observer develops a kind of brain "software" that can filter out much of the effects from poor seeing conditions -- much like some of the digital software "magic" that imagers use.  Anyway, this is another example of the difference between experience and inexperience in using an astronomical telescope.

 

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That reminds me of an old Sky and Telescope article about great visual double star observers (van Biesbroeck, van den Bos, etc.) who could make good observations of close pairs in less than perfect seeing.  Apparently they could tease out fleeting binary details in the larger seeing pattern and measure it with a filar micrometer, when most of us would only see mush.

[star acres]

Don't forget that that Celestron .....DX 130 AZ is the True Parabola mirror and you have more photons to vacuum up than my 114 MM. I enjoy what I can see so get used to upside down views and spin that telescope during the day and twilight, too. Terrestrial views.

[Asbytec]

In addition to the above, especially seeing conditions and experience, Jupiter can be pretty bright around 100x to 130x in a 5" scope. But you should see the equatorial belts, several bright zones, and the polar regions, at least. At 180x in my 6", this is what Jupiter looked like. For me, 30x per inch wasn't enough. 

 

A good magnification could be 160x or better closer to 200x. Jupiter dims a little, but the image is larger. Around those magnifications you begin to see additional detail in the temperate belts, more detail in the zones, and festoons become easier to see. In my 6" at 240x or 40x/inch, this is what Jupiter looked like. 

 

Once your scope is well collimated and thermally stable, seeing and experience are everything at the right magnification. Not too small and bright or too large and dim for your eye. Find the right magnification for you and your location. I am using 300x in my 8" and 50x/inch when I can. Then, don't just look. Observe.

 

Observing Jupiter is all about discerning color and soft hues. At lower magnification, Jupiter's bright high contrast colors are visible. The equatorial belts, a few bright zones, etc. At higher magnification when Jupiter is larger and dimmer, the plethora of its bright low contrast soft hues become visible. Festoons, ovals, etc. 

 

If you magnify Jupiter too much, say 320x with your 10mm and 5x Barlow, Jupiter becomes too dim to see well. It becomes washed out and all that remains are faint traces of its bright high contrast detail. Bright low contrast detail is lost on our eye. Jupiter looks like that in my 6" well over 50x/inch. Even in good seeing. 

Edited by Asbytec, 27 March 2025 - 07:05 AM.