![]() ![]() CelestronĪlso use a better, more transmissive glass for the corrector than in previous XLT employs multi-layer mirror coatings and multiple layers of magnesium and Celestron call this premium coating technology ‘ StarBright XLT’, as distinguished from the earlier ‘ StarBright’ coatings. Length is that you can get high powers without using complex, expensiveĮyepiece designs – Plossls and Orthoscopicsīut this one has proper multi-coatings (as you can see in the photos). The C8 is never going to give you much more than a 1° field of view. Theoretically you could get about 1.1°,īut again off-axis aberrations will limit the usable field to less than 1°. ![]() Off-axis aberrations, will be more like 0.6°.Īperture, so fitting a 2” visual back wouldn’t allow maximum benefit from 2”Įyepieces with the widest field stops. That means it has a ~2000mm focal length, which is relatively longĪnd means the maximum field of view with a 1.25” eyepiece like a 32mm Plossl is 0.77°, but in fact the usable field, due to The corrector, like all SCTs’, is float-glass.į10 design. The almost-transparent XLT-coated corrector.Ĭentral obstruction. That means the potentialįor striae and inhomogeneities varying from sample to Made of float glass – same stuff as your window panes. Obstruction does reduce contrast, but the main effect in my experience is toĬommercial SCTs (yes, even Takahashi’s, apparently) is that the corrector is Obstruction is at the upper end of what is acceptable for visual use. Housing and baffle, but it’s the overall 35% obstruction that counts. ![]() Note: CelestronĬlaim 31%, which reflects the diameter of the secondary mirror without its In this case the secondary mirror and housingĪre 80mm across, equating to 35% of the width. which can be hard to make well and close tolerances are required if However, thatĬompactness requires steeply curved optical surfaces – the primary mirror is F2 Terms of compactness and light weight (the corrector is thinner and lighter The secondary mirror and corrects aberrations in the primary optics. Turn reflects the light back through a hole in the primary, so it is indeedĪ variant on the Cassegrain a corrector plate at the front supports In this case, the main mirror focuses onto a secondary which in Telescopes that uses both refractive and reflective elements in combination – aĬatadioptric. Schmidt-Cassegrain Telescope (SCT), a type that belongs to a class of Original C8 must have been a dud, that a typical modern C8 is a much moreįor the tenth anniversary of that first review in order to re-visit the C8 with Streets ahead of the C8 in almost every way. I spent a lot of timeĬarefully comparing both scopes, but the upshot was that the refractor was As part of that process, I wrote my first ever review – aĬomparison between the C8 and a TMB 100/8 refractor. When I got back into astronomy fifteen yearsīack, I dusted off the C8, used it for a while, then ‘upgraded’ to various Unfortunately, the C8 didn’t get much use either,īecause compared to that Newtonian it frankly wasn’t much good. Massive equatorial mount, but I rarely used it because it was so time consuming I had previously owned an excellent Astro Systems 8” Newtonian on a An original orange-tube Celestron C8 was my second ‘serious’ scope, bought new inġ980. ![]()
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