![]() With reflectors, the light must go down the tube, then bounce back up. Refractors tend to suffer from this less, as the light is immediately bent away from the tube after passing through the lens. Just as the turbulence in the atmosphere can affect what you see, so can the thermals inside your telescope tube. Some people swear by refractors, but the fact is, a 10” reflector can still out-resolve a 6” refractor.but only up to a pointĪnd this is where the “all things being equal” argument comes into play. ![]() Also, a larger instrument can provide greater resolution than a smaller one – that is, it can allow you to see finer details that a smaller instrument simply cannot, all things being equal. Superior optics matter in this regard parabolic mirrors polished to 1/10 wave accuracy or better will provide better views than those at ¼ wave. The larger aperture you use, the more magnification you can achieve. Larger doesn't mean better clarity is what matters here. But if the image “breaks down,” reduce the magnification back down to the clearest image you can get. But on truly steady night, you can sometimes push it higher, to 75x or 100x per inch. So for a 4.5” scope, the most you'd want to magnify is 270x or so. Ideally, the limit SHOULD be about 50x - 60x per inch of aperture. On the other hand, if it is hazy and the stars are steady, you may be able to push the magnification more. If the stars are twinkly furiously, it's probably not a good night for planetery viewing. On most nights, the maximum magnification that ANY telescope can really achieve on the planets is about 150x, due to something called “atmospheric seeing.” This is a term that relates to the “steadiness” of the atmosphere above us, and importantly, BETWEEN us and the planet we are viewing. Crank up the power!īut not TOO much! Claims of "575x magnification!" for small telescopes is unrealistic. Use good eyepieces for planetary viewing (and it won't hurt to use them for deep sky observing either!). Top that off with poor baffling, and “ghosting” can occur, leading to multiple and more smearing of images. Less expensive eyepieces can do the same thing as poor telescopes scatter light, and with low quality anti-reflection coatings, can actually reflect light inside the eyepiece. Fortunately, even small, inexpensive telescopes tend to have at least decent optics - however, the rest of the instrument may need some work. With their small size, every photon counts, so using better quality scopes matters. Poor telescope optics will scatter the incoming light, which can smear fine, subtle details. So how do we make the most of observing them? A good telescope Given that Mercury, Venus, Uranus and Neptune don't offer much of any detail for even moderate ground based telescopes, that really leaves us with just three planets to view for something more than phases. Here are the maximum and minimum angular diameters of the planets, as seen from Earth: ![]() And some planets just don't show much detail – Mercury and Venus, for example, will display phases like the Moon does, but there's not much to see beyond that (unless you are one of the lucky ones to see the “ashen light” on Venus?). Jupiter, by contrast, is at most about 50 arc seconds across, less than 3 percent that size! Saturn is slightly smaller, Venus can vary greatly in size, but offers little detail, while Mars and Mercury are both comparatively tiny, with Mars – at ideal oppositions once or twice every 15 years – is just 25 arc seconds across (half of Jupiter's size), despite Mars being closer to us. ![]() Let's talk angular size: The Moon is a half a degree across, or about 1800 arc seconds. However, since the planets are small in angular size – even Jupiter, at largest, is still smaller than 1 arc minute across – this means that more magnification is required to see that detail that the planets offer. Also, the planets are closer to us than deep sky objects, contributing to their increased magnitude. This may make it seem like a larger telescope is not required, but more on that later. Most obvious is that the brightness of the naked eye planets far exceeds that of even the most prominent deep sky objects. Planetary observing differs from deep sky objects observing in a few key ways. Beginner astronomy: Planets Tips for observing the planets ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |