Aperture helps, but it is only one of several things to consider in viewing the Red Spot on Jupiter. I have seen it very well in an 8 inch, and not seen it in a 25 inch telescope. Still air is best. There should be no "twinkling" or blinking of star images, even near the horizon. Try to get to an area where there is little or no wind. Also any time around a change in temperature or storm conditions means the air is moving. Smog, little variation between day and night temp- erature, and hazy, dusty sky means the air is still. Try to be somewhere without streets, traffic, house roofs, or parking lots. These release heat at night. Forest are much cooler in the day. One of the finest solar observatories, Big Bear in California, is surrounded by a mountain lake in a high (2000m) forest. The cold water makes for heavy still air around the telescope. You should wait until Jupiter is high in the sky. Opposition was last fall, so now Jupiter is moving farther West every sunset. Soon it will be too low to see fine detail. This summer and fall will have it high in the night sky again. Sometimes Jupiter shows no Red Spot at all in the best observing conditions--it is on the back of the planet! Jupiter rotates in just over 10 hours, so you may have to wait from 1 to 6 hours to see the Red Spot clearly. The Red Spot is not always very red. Over the past 300 years that it has been observed, it has faded in color to almost a pale peach or yellow at times. And some color-blind people may not see it at all. A filter of deep green color makes the Red Spot very dark and with high contrast to the bands of gas on the planet. Bigger telescopes may be the solution to your quest of viewing the Red Spot. But they cost a lot, are a lot of work to set up and use, and under bad sky conditions, may not do much better than moderate sized telescopes. Keep trying with 6 to 12 inchers before you jump into a big one!