Thread: Achromat vs Mak
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Old 06-03-2020, 10:50 AM
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mental4astro (Alexander)

mental4astro is offline
Join Date: Jun 2008
Location: sydney, australia
Posts: 4,877
Sky', have a read of post No. 7. The OP explains his reasons.

As for the loss of contrast in a Mak, I'm not sure that really is all that applicable. The % contrast difference is questionable if we can actually see it, and not to mention sec obstruction difference is really being all that significant between Newts and Maks, and even SCT's. Different Maks and Newts will all have differences in % obstruction too.

I will say more significant is the optical quality of EACH instrument, regardless of design or even Brand. If all the photons go where they are supposed to, and the physical design of the OTA, (not the optics - two separate things. Here it relates to the quality of internal baffling), these will have a much greater impact on the final image quality & "contrast" than the size of the secondary obstruction. This is from my experience, not hearsay.

I know the optical quality of my 9" Santel Mak is outstanding (Strehl ratio 0.945). It rips strips off just about every SCT and mass production Newt I've looked through. But I've seen through Wavytone's 10" APM designed Mak (same Intes quality optics & same Strehl ratio (within 0.02 of each other)), which has a marginally smaller secondary obstruction, but the design of the internals are totally different, and OMG! What a Goddamn enormous difference in contrast between the two scopes!!! Same EP used in each scope so the EP cannot be called into question for any differences. Secondary obstruction means a lot less than is given credit for.

And this is not to mention comparisons done between high end large Apos with my Santel, Wavy's APM, and the 7" Intes I had, and there is no difference in planetary detail.

Have all the photons go where they are supposed to go (optical and collimation), and the detail will be there - goes for every scope design. As for contrast, I've only seen the same quality of contrast seen in that 10" APM Mak in other reflectors (Newt, Cass, Mak, SCT, whatever) was in two other 10" Japanese made Cassegrains, one a Dall Kirkham Cassergrain and the other a Klevtsov Cass - not to say other reflectors (Newt, Mak, etc) can also have the same quality of contrast.


Last edited by mental4astro; 06-03-2020 at 06:15 PM. Reason: Typo
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