Get a Better View of Jupiter
Subscriber E.D. writes, “I wonder if you can help me get a better view of Jupiter. I have a 10” reflector and with a 5mm eyepiece, so I get 240 X magnification of Jupiter and very good resolution. What I lack is contrast. I can see the planet quite large and see the cloud bands, but the red spot is very difficult to see. I’ve tried a blue filter but it’s just very difficult to discern. Do you have any advice for making the red spot really pop out?”
To be honest, E.D. is on the right track. He’s using a large aperture scope to increase resolution of fine detail. He’s using high magnification to increase the image size, yet he’s not using a too-high magnification to dim the image. And he’s using a filter of the opposite color from the object he’s trying to find… in this case, the Great Red Spot.
What else can one do to get a better view of Jupiter, its colorful cloud bands, and Great Red Spot?
Here are a few more tips, some of which come right out of Basic Astronomy With a Telescope, an online astronomy course recommended by none other than Sir Patrick Moore, the grand patriarch of amateur astronomy.
* For us northern observers, Jupiter has been at a low altitude these last few years, which means we have to look through a lot of atmospheric murk. Next year will be better, but for now do most of your observing when Jupiter is highest in the sky so you look through the least amount of atmosphere.
* Try not to observe Jupiter when its over a rooftop or a driveway, or anything else that’s slowly radiating daytime heat. The turbulence and shimmering caused by the rising warm air will make the image into an ugly boiling blob.
* Use a simple eyepiece design to enhance contrast and color fidelity. Plossls and Orthoscopics work well, as does the slightly more expensive Radian design by Televue.
* Refractors tend to have better contrast than reflectors. But bigger telescope have better resolutions. While it’s easy to find an 8-10″ or larger reflector, good luck getting your hands on an 8-10 refractor! But when using a reflector like E. D., make sure the instrument is well collimated (see your user’s manual for how to do this). Sometimes, just a slight turn of an alignment screw makes all the difference (of course, you have to know which screw to turn and which way to turn it).
* Look carefully… even at 240x, the Great Red Spot appears tiny. It takes a little practice seeing such fine detail.
* Above all, be patient. Sometimes you just have to wait for a patch of steady air to let you glimpse the maximum detail. Some nights, you get just 10 seconds of good seeing at a time. But it’s often worth the wait.
And here’s an advanced tip…
* If you have an 8-inch or larger scope, try an apodizing mask. This is a type of filter or screen than fits over the top of the telescope. It gradually decreases the amount of light reaching the edge of the objective lens or mirror. This has the effect of improving contrast by reducing the amount of light from one feature that diffracts into another.
(Trust me, you do NOT want to see the mathematics required to prove this).
On planets and double stars, apodizing masks can work remarkably well. I’ve not seen such masks for sale. But here’s a link to help you make your own.
http://www.bpccs.com/lcas/Articles/apodizing_masks.htm
Do you have a question about observing the heavens, whether with your eye, binoculars, or telescope? Send us an email at info@oneminuteastronomer.com. And remember, there are no dumb questions, only dumb mistakes.
