Last updated: 19 January 2001

Observations of Jupiter with the ETX-125EC

From: sherrodc@ipa.net (Clay Sherrod)

There was a recent post on the site about disappointing views of Jupiter. The user was getting good images of Cassini's division on Saturn, so that tells me there is nothing wrong with the telescope.

As a retired astronomer and educator, I have spent countless sessions dismissing the myth that Jupiter - because it is so big and there are "festoons, and spots, and lots of activity (there, indeed are all those things!). On the other hand, Jupiter is A LOW CONTRAST OBJECT. No matter how good your seeing, nor how large a telescope (even the bigguns), contrast is your enemy on the gas giants.

Here's how to get around it, because - in the ETX 125 (I know because I use one religiously and love it) - you CAN see all those things; as for the Red Spot, Sky & Telescope magazine publishes monthly transits of the GRS in its calendar pages. Depend on this for the proper local times for viewing; it is clearly visible now.

My best tip for observing the "stuff" on Jupiter that you want to see? Go to Meade, or some other supplier, and get a Wratten #58 Green filter (do not get some aftermarket off brand) that screws onto the base of your eyepiece. This provides striking contrast of the Great Red Spot, white spot storms, the fainter belts and - yes - festoons (since they are white-ish).

Using the -125, DO NOT attempt to use more than about 250x for the planets, except when the seeing is remarkable. I routinely use the Meade SP 15mm + the "shorty" barlow for a total power of 260x, which is absolutely perfect on a good night. You will, indeed, see what you are looking for if you use the filter. By the way....try the way, for SATURN, use both the Wratten #11 (yellow) and #82A (pale blue); for MARS, by all means the best is Wratten #21 orange (some recommend "red" but this is way too eliminating of necessary wavelengths); VENUS is approaching its peak, so try a Wratten #47 (violet) to see all that it offers - and its does!) An additional note: the Wratten #58 green makes a WONDERFUL MOON FILTER, much better than those advertised specifically for that purpose!

Although filters might seem like "bells and whistles" to some, I have had (too) many years using them with great success on bright planets. Try out at least one for now and you will be convinced.

Best of luck....and good seeing!

P. Clay Sherrod, Conway, Arkansas

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Copyright ©2001 Michael L. Weasner / etx@me.com
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