Maksutov-Cassegrain Vs Schmidt-Cassegrain
Maksutov-Cassegrain Vs Schmidt-Cassegrain
Hello all,
What are the differnces in optical performance between these two types of telescope? For the same aperature, say 5", which one is better? Or they are good in different aspects? Thanks for telling!
Willis
What are the differnces in optical performance between these two types of telescope? For the same aperature, say 5", which one is better? Or they are good in different aspects? Thanks for telling!
Willis
Re: Maksutov-Cassegrain Vs Schmidt-Cassegrain
Mak:
- 修正鏡較厚, 需較長時間達到熱平衡
- 比較難修正光軸
- 一般較長焦 f/12 或以上
SCT:
- 很多不同配件可用
- 容易修正光軸
- 修正鏡較厚, 需較長時間達到熱平衡
- 比較難修正光軸
- 一般較長焦 f/12 或以上
SCT:
- 很多不同配件可用
- 容易修正光軸
This one is SCT, not MCT...Wah!! 寫:當你試過支 6" Maksutov-Cassegrain 的重量級, 你就會知道點選擇呢~
http://www.hkastroforum.net/viewtopic.php?p=142416
http://www.skiesunlimited.net/index.php?CategoryID=44
http://www.bpccs.com/lcas/Articles/schm ... egrain.htm
Maksutov-Cassegrain telescopes are similar to Schmidt-Cassegrains, using both mirrors and a lens (meniscus lens) to focus light into a smaller area. Maksutov-Cassegrains offer superior contrast to a Schmidt-Cassegrain due to the smaller central obstruction of the secondary mirror. They are an excellent choice for planetary and double star observing. The only noteworthy disadvantage to a Maksutov-Cassegrain is the relatively slow focal ratio that results in a narrow field of view in comparison to other optical designs with similar aperture.
Since all the optics in an MCT are spherical (the primary, the secondary, and both sides of the corrector), and since making and testing spherical optics is easier, it takes less work to shape and polish MCT optics to a higher precision. In comparison, SCT corrector plates, with their weird curve, are difficult to shape correctly and next to impossible to polish to maximum smoothness. So it’s not really that the MCT design gives superior images, it’s just that MCT optics tend to be of higher overall quality than an SCT of the same size.
Most MCT’s have a proportionally longer tube than a comparable SCT owing to the longer focal ratio of the primary mirror. Thus in the larger sizes, an MCT will end up being bulkier, and it will be more expensive (due to the cost of the corrector). Also, due largely to the thickness of the meniscus corrector, the time required for an MCT to acclimate to the outdoor temperature will be greater than for an SCT. In the plus column is the fact that the image sharpness in a well-made MCT is generally better than in any SCT.
http://www.bpccs.com/lcas/Articles/schm ... egrain.htm
Maksutov-Cassegrain telescopes are similar to Schmidt-Cassegrains, using both mirrors and a lens (meniscus lens) to focus light into a smaller area. Maksutov-Cassegrains offer superior contrast to a Schmidt-Cassegrain due to the smaller central obstruction of the secondary mirror. They are an excellent choice for planetary and double star observing. The only noteworthy disadvantage to a Maksutov-Cassegrain is the relatively slow focal ratio that results in a narrow field of view in comparison to other optical designs with similar aperture.
Since all the optics in an MCT are spherical (the primary, the secondary, and both sides of the corrector), and since making and testing spherical optics is easier, it takes less work to shape and polish MCT optics to a higher precision. In comparison, SCT corrector plates, with their weird curve, are difficult to shape correctly and next to impossible to polish to maximum smoothness. So it’s not really that the MCT design gives superior images, it’s just that MCT optics tend to be of higher overall quality than an SCT of the same size.
Most MCT’s have a proportionally longer tube than a comparable SCT owing to the longer focal ratio of the primary mirror. Thus in the larger sizes, an MCT will end up being bulkier, and it will be more expensive (due to the cost of the corrector). Also, due largely to the thickness of the meniscus corrector, the time required for an MCT to acclimate to the outdoor temperature will be greater than for an SCT. In the plus column is the fact that the image sharpness in a well-made MCT is generally better than in any SCT.
最後由 Steve 於 週四 21 5月, 2009 13:40 編輯,總共編輯了 1 次。
6英吋 (150 mm) 以上的馬卡重過施卡好多,主要由於前面的彎月型透鏡好厚,最好放在天文台內用。
6英吋 以下馬卡與施卡長度及重量差不多,馬卡重過施卡些小,馬卡的焦比由 f/12至 f/20,施卡一般是 f/10,馬卡現時最細口徑大約是 65 mm,90 mm/100mm馬卡只售港幣壹仟多元,又輕便又矩身,最適合初學者。
但施卡現時最細口徑只係 127 mm (C5),沒有再細。
一般來說,馬卡的成像較施卡的銳利,尤其是高級的馬卡,可以比美高級ED折射鏡,馬牛 (Maksutov Newtonian )的成像就更加銳利同高級ED折射無差別。不過馬牛鏡筒好長,不易攜帶。
6英吋 以下馬卡與施卡長度及重量差不多,馬卡重過施卡些小,馬卡的焦比由 f/12至 f/20,施卡一般是 f/10,馬卡現時最細口徑大約是 65 mm,90 mm/100mm馬卡只售港幣壹仟多元,又輕便又矩身,最適合初學者。
但施卡現時最細口徑只係 127 mm (C5),沒有再細。
一般來說,馬卡的成像較施卡的銳利,尤其是高級的馬卡,可以比美高級ED折射鏡,馬牛 (Maksutov Newtonian )的成像就更加銳利同高級ED折射無差別。不過馬牛鏡筒好長,不易攜帶。
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