This negative image of the double star Zeta Boötis shows the effects of atmospheric vision. The currents of the tube can distort the star images just as badly. Credit: Nordic optical telescope
One of the most important factors for amateur astronomers is Seewhich is defined as the stability of the atmosphere on your observation site. You can say how good (or bad) the visa is viewing a reasonably bright star (2nd magnitude) near Zenit. If he is sparkling wildly, seeing is bad. But if the image is relatively constant, your seeing is good. And while the general seeing could be good or even exceptional, you may still see its effects when you look through your telescope. Could it be tube currents?
How to say it
The degradation of seeing due to the currents of the tube (also thermal calls) is a widely recognized problem. But how do you know if it is your problem? Bocch your telescope on a fairly bright star and use your focuster for Defocus its image. This will allow you to actually see if there are air currents. If the image is reasonably constant, your problem is not the tube currents.
If, however, you see many circular movements that move inside the image, you have serious currents of the tube. My late observation companion, Jeff Medkeff, once said to me: “If your star image out of Focus has” hair “or a” fire ring “around the external edges, and these reasons change thinly for a period from 30 seconds to five minutes, then you have the currents of harmful pipes-even if no vorteous air is visible in the star itself.”
The solution
This problem is easy to solve, but you must have the right equipment. The solution is to use a small low flow fan to detonate the hottest air from the tube. Your goal is to bring the mirror to the same temperature as the external air. Once this is done, check the image out of focus and you should see a considerable improvement.
