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Apex 127 vs. Skymax 127 with MHTC

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#1 Nicole Sharp

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Posted 25 November 2021 - 04:54 AM

What difference does the Sky-Watcher Metallic High-Transmission Coatings (MHTC) make in light transmission on the Sky-Watcher Skymax 1540/127 MCT versus the Orion Apex 1540/127 MCT with standard optical coatings?

 

I can't find much information about MHTC online.  Since Sky-Watcher and Celestron are the same company, I would speculate that the Sky-Watcher MHTC might be on a par with Celestron StarBright (XLT)?

 

Is it worth paying extra for the Skymax 127 instead of the Apex 127?  When bundled with the Orion StarSeeker, the Skymax 127 is an extra $100.

 

My issue is that the 2-inch visual back on the Skymax 127 isn't removable or threaded (according to Sky-Watcher) so I can't thread on a T-adapter or any other accessories.


Edited by Nicole Sharp, 25 November 2021 - 04:55 AM.

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#2 luxo II

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Posted 25 November 2021 - 07:26 PM

It's marketting-speak. Could mean anything and I would not agonise over it.



#3 sevenofnine

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Posted 25 November 2021 - 07:43 PM

Years ago, when I was researching 5" Maks to buy, the Apex 127 was the clear leader. That doesn't mean the SkyWatcher isn't just as good but more users took the time to recommend the Apex. Sharpness and apo-like views were frequent comments. What clinched it for me was the durability. One nature photographer used it for his long lens on shoots in Africa. He said it was remarkably good considering all the scratches and dents shocked.gif  I put my order in the next day. waytogo.gif


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#4 maroubra_boy

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Posted 25 November 2021 - 07:43 PM

It's marketting-speak.

Of course it is marketing spin!

 

Coatings are typically made from Magnesium Fluoride, or other metal compounds, hence the "Metallic".  Adding the bleeding obvious IF you don't know what coatings are made from makes it sound SOOOOO much more exotic and exciting, doesn't it!  I mean it's got you going, hasn't it?  But now, knowing that it is nothing new or exotic, what do you think about your "metallic high-transmission coatings"????  You really thought that there was something special or voodoo going on here?


Edited by maroubra_boy, 25 November 2021 - 07:44 PM.

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#5 luxo II

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Posted 25 November 2021 - 08:09 PM

Nicole,

 

They all come from the same factory and I very much doubt the factory would apply different coatings for different brands; far simpler to use one manufacturing process for all, as it is complex and expensive. The giveaway is the physical appearance of the coating in reflected light - if they look much the same you can bet your bippy the same techology was used.

 

For correctors... MgF - the deep blue-purple-violet coatings - was last-century stuff. The downside being (1) MgF is quite soft, easily scratched when cleaned and (2) it's adhesion to the glass substrate was not great and it tended to peel off when coating met water (dew, or over-zealous cleaning).

 

These days the pale greenish coatings are multi-layer dielectric, zinc-cryolite, which is hard and has much better adhesion to the glass. These modern coatings are tougher than glass - far, far tougher than MgF - and will survive careful cleaning - I can vouch for that as my specs have this coating and I clean them about 3 times a week; after 2 years the coating is intact no scratches.

 

... except for one thing - DEET (in insect repellants) will destroy them. This applies to coatings on eyepieces too.

 

Hence make sure anyone applying insect repellant is well downwind of your scope.


Edited by luxo II, 25 November 2021 - 08:27 PM.

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#6 Nicole Sharp

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Posted 25 November 2021 - 08:19 PM

Of course it is marketing spin!

 

Coatings are typically made from Magnesium Fluoride, or other metal compounds, hence the "Metallic".  Adding the bleeding obvious IF you don't know what coatings are made from makes it sound SOOOOO much more exotic and exciting, doesn't it!  I mean it's got you going, hasn't it?  But now, knowing that it is nothing new or exotic, what do you think about your "metallic high-transmission coatings"????  You really thought that there was something special or voodoo going on here?

 

I would like to think that Sky-Watcher MHTC uses the same or similar technology as for Celestron StarBright XLT, since Celestron and Sky-Watcher are the same company.

 

https://www.celestro...tical-coatings/

 

StarBright XLT uses "[h]afnium—a rare element that costs nearly $1,500 per kilogram—gives us a wider band pass than the titanium used in competing coatings."

 

StarBright XLT claims up to an 16% improvement in light transmission as compared to StarBright (without XLT).  That reduces the t-stop by 0.93X, so if the Apex 127 is f/12.1, the Skymax 127 might act more like f/11.3, so that exposure times could have to be 1.2 times longer on the Apex 127 as compared to the Skymax 127.

 

However, Sky-Watcher doesn't seem to have any technical information published about MHTC, so if it offered an advantage over competitors (like for StarBright XLT), I would think they would be advertising it more.

 

But without more data or tests, any comparisons seem to be speculative, unless anyone has both of these telescopes to compare side by side.  I ordered the Apex 127, since it is cheaper and the 1.25-inch visual back will be smaller and lighter on the OTA as compared to the 2-inch visual back on the Skymax 127.  Sky-Watcher said that you can't replace the visual back on the Skymax 127, so the Apex 127 should be easier to work with I think.


Edited by Nicole Sharp, 25 November 2021 - 08:20 PM.

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#7 Nicole Sharp

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Posted 25 November 2021 - 08:22 PM

Nicole,

 

They all come from the same factory and I very much doubt the factory would apply different coatings for different brands; far simpler to use one that works for all as it is a complex and expensive process.

 

For correctors... MgF - the deep blue-purple coatings - was last-century stuff. The downside being its adhesion to the glass substrate was not great and it tended to come off when coating met water (dew, or over-zealous cleaning).

 

These days the pale greenish coatings are multi-layer dielectric, zinc-cryolite, which is tougher than glass with better adhesion to the glass. These modern coatings are tougher than MgF and will survive careful cleaning - except for one thing - DEET (in insect repellants) will destroy them. This applies to coatings on eyepieces too.

 

Hence make sure anyone applying insect repellant is well downwind of your scope.

 

I did ask Orion about their optical coatings, and they said they use standard optical coatings without any "exotic" elements like with Meade UHTC or StarBright XLT.  If Sky-Watcher MHTC is the same as what Orion has, then MHTC is just a fancy name for their version of a standard optical coating.

 

The Celestron C127/127SLT (1500/127) also uses standard coatings without StarBright XLT, but is a little bit faster at 1500/127 instead of 1540/127.


Edited by Nicole Sharp, 25 November 2021 - 08:32 PM.

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#8 maroubra_boy

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Posted 25 November 2021 - 08:26 PM

You might like to think that there are differences, but I ask you how?  There may be some spec differences in the coatings and this can happen with specific contracts (some will have a more purple hue to coatings others green), but at the same time much of this is spin as well.  How are you or me going to prove anything about what is claimed.  Each brand puts its own spin on things to distinguish itself from everyone else, but again, how are you going to prove anything is different?  None of these brands are making any outrageous or bogus claims about their coatings, it is all their own spin.  None of it is misleading in claims, just phrasing and what appeals more to you.  "Metallic High-Transmission Coatings"...  Multi coatings for everyone else.

 

The world of optics is a very small and even incestuous one.  The number of manufacturers is actually very small.  An OEM can provide some latitude with design of EP casings for example, but the glass and coatings may be exactly the same for a dozen different contracts that it fulfils.  And the different brands can charge xxx dollar more because they can and people think they are getting something more special.  Not always the case...


Edited by maroubra_boy, 25 November 2021 - 08:31 PM.

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#9 luxo II

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Posted 25 November 2021 - 08:30 PM

Add green letters and a certain brand-name and you can quadruple the price of eyepieces, for example.

 

Gotta love the ability of marketing spin to inflate prices. 


Edited by luxo II, 25 November 2021 - 08:52 PM.


#10 fcathell

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Posted 25 November 2021 - 09:27 PM

I have compared the Orion 102 Apex Mak with a Celestron 4SE Mak with XLT coatings and there was a noticeable difference in the brightness of extended objects (namely Jupiter) and the background sky under partial twilight conditions. It was not dramatic, but definitely noticeable.  Although I didn't measure the primary mirror in the 4SE, the aperture at the corrector retaining ring is exactly 102 mm for both scopes and I know from previous repairs on an Apex 102 Mak that the primary is slightly larger than 102 mm. The secondary mirror obstruction appears identical. Optically both were excellent with very sharp planetary images and excellent airy disc patterns.  My only complaints were the image shift with focus of the 4SE (but not a show stopper by any means), and the stiff focus of the Apex, but no image shift.

 

Frank

 

Tucson 


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#11 maroubra_boy

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Posted 25 November 2021 - 10:21 PM

Frank, which was the brighter one?  I'm not going to assume anything.  Same EP and diagonal used in each scope?  Might sound pedantic but vital for a comparison.

 

In the Mak design the primary IS slightly larger than the aperture opening because of the way the meniscus corrector alters the light entering it.  It is not any form or advantage that the Orion has - this is what the design calls for.

 

Alex.



#12 fcathell

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Posted 25 November 2021 - 10:55 PM

I'm sorry I wasn't specific, but the 4SE Mak had the brighter images.  Again, many people would not notice it but after 50 years of observing and some variable star work in the past, I surmised that the 4SE was brighter. I used the same diagonal in both scopes and used a Celestron visual back on the SE's rear port with an adapter. There may have been a slight difference in focal lengths, however, this would have favored the Apex Mak with a slightly shorter effective FL, and hence slightly lower power. This same test was performed on a couple of C-8s about a year of so ago and one of the C-8s had XLT coatings while the other was a little older with standard coatings. A slight increase in brightness was also noticeable in this case also.  It was most apparent while observing globular cluster M22. Both C-8s had Celestron prism diagonals and the eyepieces were identical. 

 

Frank



#13 fcathell

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Posted 25 November 2021 - 11:00 PM

By the way, did Synta ever change the 127 Mak's primary mirror to the proper oversized diameter as it should be?  I remember this particular Mak had about a 120 mm or so primary mirror, definitely smaller than the corrector diameter.

 

Frank



#14 Nicole Sharp

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Posted 25 November 2021 - 11:52 PM

I'm sorry I wasn't specific, but the 4SE Mak had the brighter images.  Again, many people would not notice it but after 50 years of observing and some variable star work in the past, I surmised that the 4SE was brighter. I used the same diagonal in both scopes and used a Celestron visual back on the SE's rear port with an adapter. There may have been a slight difference in focal lengths, however, this would have favored the Apex Mak with a slightly shorter effective FL, and hence slightly lower power. This same test was performed on a couple of C-8s about a year of so ago and one of the C-8s had XLT coatings while the other was a little older with standard coatings. A slight increase in brightness was also noticeable in this case also.  It was most apparent while observing globular cluster M22. Both C-8s had Celestron prism diagonals and the eyepieces were identical. 

 

Frank

 

The 4SE has one of the largest relative central obstructions for any Synta MCT.  That plus the slower focal ratio should give it a much slower t-stop compared to an Apex 102 or Skymax 102, other than the difference in coatings.  So that StarBright XLT is really making a significant impact then, if the 1325/102 with a 35-mm central obstruction appears brighter than the 1300/102 with a 31-mm central obstruction.

 

The question then is if Sky-Watcher MHTC can compare to StarBright XLT.

 

Orion has an excellent return policy, so I have 30 days to return the Apex 127 if I change my mind.  However, the Skymax 127 is sold out until next year.

 

If someone in Maryland, West Virginia, or Pennsylvania owns a Skymax 127, then could do a side by side test.  If there is up to a 16% increase in light transmission like with StarBright XLT, that should be easy to notice even visually.


Edited by Nicole Sharp, 25 November 2021 - 11:59 PM.

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#15 alnitak22

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Posted 26 November 2021 - 01:51 PM

Add green letters and a certain brand-name and you can quadruple the price of eyepieces, for example.

 

Gotta love the ability of marketing spin to inflate prices. 

I have 3 brands of eyepieces with green lettering. TeleVue, Takahashi and University Optics. I find each of them to be well worth the price  I paid, and in most cases, I was able to try before purchase so marketing had nothing to do with my decisions. And I really couldn’t care less how much or how little someone else spends ...on anything. From Scotch to wine to optical gear. I’m the one using the items, not anyone else.


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#16 fcathell

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Posted 26 November 2021 - 10:36 PM

Nicole - I think you may be confusing the 127 Mak with the 102 Maks.  The C-4SE 102 Mak's CE appears no larger than the Apex 102 Mak's CE when looking down the eyepiece tube. In the event there is the difference that you state, it's highly unlikely that this difference in masked primary area will make any noticeable difference since it is in the center of the mirror.  In any case the brightness was noticeable to me and there certainly appears to be no coating or other issues associated with the Apex Mak which is not that old.

 

Frank




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