Maksutov-Cassegrain Vs Schmidt-Cassegrain

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willis
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Maksutov-Cassegrain Vs Schmidt-Cassegrain

文章 willis » 週二 19 5月, 2009 20:02

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

observer
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Re: Maksutov-Cassegrain Vs Schmidt-Cassegrain

文章 observer » 週二 19 5月, 2009 21:57

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

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willis
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文章 willis » 週二 19 5月, 2009 22:05

So it is better to buy SCT. Am I right?

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Wah!!
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文章 Wah!! » 週三 20 5月, 2009 16:10

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

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willis
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文章 willis » 週三 20 5月, 2009 17:49

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
This one is SCT, not MCT...

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Wah!!
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文章 Wah!! » 週三 20 5月, 2009 17:56

因為 SCT is my choice! :mrgreen:

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willis
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文章 willis » 週三 20 5月, 2009 18:09

Wah!! 寫:因為 SCT is my choice! :mrgreen:
ic ic. I also opt for SCT. I ordered an M8. But I just want to know the differences between SCT & MCT.

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Wah!!
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文章 Wah!! » 週三 20 5月, 2009 18:14

對於我來講, 重量就是影響我選哪種的最大因素

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alget
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文章 alget » 週三 20 5月, 2009 19:24

俄羅斯有生產8吋或以上的MAK, 不過重量足以打消大部分人的購買意欲.

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willis
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文章 willis » 週三 20 5月, 2009 19:26

So apart from the heavy weight of Mak, what is the advantage of Mak? There must be some good points of Mak. Or it has been faded out already.

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Steve
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文章 Steve » 週四 21 5月, 2009 10:22

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.
最後由 Steve 於 週四 21 5月, 2009 13:40 編輯,總共編輯了 1 次。

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willis
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文章 willis » 週四 21 5月, 2009 12:35

Thanks Steve! Very clear & informative!
Willis

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Wah!!
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文章 Wah!! » 週四 21 5月, 2009 12:37

Steve 寫:...... They are suitable for both astronomical and terrestrial observing due to the upright image they produce, ....
乜唔係倒像咩? :?

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文章 TONGKW » 週五 22 5月, 2009 21:43

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。
附加檔案
MK67 C5 C6 C8.jpg
Intes MK67 Mak, Celestron C5, C6 and C8 SCT (their relative sizes)
MK67 C5 C6 C8.jpg (75.87 KiB) 已瀏覽 9799 次

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A/45
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文章 A/45 » 週五 22 5月, 2009 22:27

TONGKW 寫:...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。
Agree. I miss the views through the MN56 which I think is even a bit sharper than the Takahashi MT-130 on planets.

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