We started zooming in on that object, only to find out that our final picture looked blurry. Aperture at least 200mm (8 inches high resolution)Īt one point in our lives, we all tried to image an object that was far away with our phones. In refractors and Newtonian telescopes, the focal length is the actual distance from the lens or mirror to the focal point. Focal length refers to the effective distance from the lens or mirror to the focal point, where an eyepiece or camera would go. As a rule of thumb, you could say that a good planetary telescope requires at least a focal length of about 2000mm in order to magnify the planets to such a point where these surface details are visible. So if you want to see some details on the surfaces of those planets, like the cloud bands on Jupiter and the red spot, or the Cassini division in the rings of Saturn, you would need a telescope that is able to magnify the planets to the point that those features are visible. This means that the planets, even at the best of times, are 60 times smaller as compared to the moon. ![]() Similar to how you calculate time, you can derive that 2×30 arcs seconds = one arc minute, and 30 arc minutes = the size of the moon (give or take an arc minute). The moon has an angular size of about 30 arc minutes. If you are unfamiliar with angular size, picture this. again, the closest distance from earth), the planets – with the exception of Jupiter – will not be larger than 30 arcseconds in angular size. the closest distance from earth) or the inner planets are at their closest western or eastern elongation (i.e. Even at the best of times, when the outer planets are ‘in opposition’ (i.e. The most important thing is that a planetary telescope has a sufficient focal length. Five important criteria (must-haves) to look for in a planetary telescope Focal length at least 2000mm (high magnification) I’ll first start with the five must-haves, after which I’ll mention five nice-to-haves. Also, if you have any thoughts or experiences with the telescopes that I’m going to mention, I highly encourage you to leave a message in the comments section so that others who read this blog can benefit from your experience as well. ![]() My priorities may be different than yours so I would always encourage you to do your own research. It is important to state at this point that I’m an amateur astrophotographer myself, performing my astrophotography in Utrecht, The Netherlands. Also, I considered a number of nice-to-haves that I would personally prefer to see in a planetary scope. PART 1: WHAT IS A GOOD TELESCOPE FOR PLANETARY IMAGING?īased on my own research, I came to the conclusion that five criteria are especially important for a good planetary telescope. ![]() Next, I’ll compare five telescopes to each of the criteria I’ve mentioned in the first part. ![]() In this blog, I’ll first explain some must-haves and nice-to-haves that I would deem important for a planetary telescope. A big advantage of the C8 is that it is the shortest (425mm) and lightest (5,8 kg) telescope in this overview, with a decent aperture (203mm) and focal length (2036mm). The Celestron XLT C8 Schmidt Cassegrain finished third. This telescope has the longest focal length in this price range as a Maksutov telescope which gives you a high magnification needed for planetary imaging, it has a small secondary mirror, and users report that the telescope requires almost no maintenance. A decent second was the SkyWatcher Skymax Pro 180mm. It has a decent 8″ aperture, a long focal length of 2436mm, it doesn’t have a corrector plate that would attract dew and require a longer cooldown time, and it comes with a 1/10th fine focuser. The outcome is that the Classical Cassegrain 203/2436mm (F/12) ticked most of the criteria I was looking for. I’ve compared five planetary telescopes from $500 to $1250 on a number of criteria. Are you looking for a reasonably affordable telescope for planetary imaging? I had the same question and decided to do some research.
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