OTA differences in skywatcher 127 Mak

[DrMike]

Hello everyone, I hope some of you can advise me here. I am thinking of getting the “Sky-Watcher 127 mm Skymax Maksutov-Cassegrain OTA with AZ-GTi Multi-Purpose Mount & Tripod”, but when I see the Sky-Watcher 127 mm Skymax Maksutov-Cassegrain OTA sold separately, not with a tripod, the OTA’s have different specs. 

The former is f/12.1, the latter f/12, along with different focal lengths, tube lengths and weight. 

Is this due to different material in the construction, and is the optical quality better in one than the other?

And the big question...why?

By the way, it is to be used as a visual grab-and-go telescope only.

Any advice welcomed.

 

 

[Carbon Brush]

I have found Skywatcher are often not that good when it comes to the details of specification.

Errors and omissions don't surprise me any more.

I think in this case, it is the same scope. Have you asked the retailer?
I'm assuming it is being offered a specialist astro retailer. Not Wal Mart or amazon or someone like that🤨. 

HTH, David. 

 

[Stu1smartcookie]

The 127Mak from Skywatcher (synta) comes in various forms but its the same telescope .The mirror is considered to be 119mm , not 127 , i am not sure why Skywatcher do not market it correctly  another  difference i know is that if you buy one with the AZ-Gti , the dovetail bar is in a different position than if you buy it seperately from the mount .  Grab and GO is just about right but please bear in mind the scope will need about 30mins to "cool" down ... oh , and you need to buy a Dew shield as both SCTs and Maksutovs are dew magnets 

Edited September 23, 2022 by Stu1smartcookie

[RT65CB-SWL]

Not only are Sky-Watcher known for inaccuracies/discrepancies in their Mak-specs, Meade
too have done it with their ETX series. They have changed the outer tube diameter a few times.

I found that out when I was 'searching' for a replacement ABS back when mine got damaged
on my ETX105 when I phoned them many years ago.

Edited September 23, 2022 by Philip R

[DrMike]

Thanks for the information. I appreciate it, but, they are definitely two different scopes, with,  albeit small, differences.

For instance:

OTA.                                 OTA & Tripod 

f/12                                       f/12.1

OTA weight 9.7 lb      OTA weight 9.37 lb

focal length 1500       focal length 1540

 

I wonder if it's the material used, or that they just upped or lowered specs to fit/work on GTi drive?

 

Of course, they could all be mistakes and are exactly as suggested, the same scope.

 

I shall dig deeper....

[Zermelo]

As for the F/12 vs F/12.1, well:

- as pointed out above, the actual diameter is moot
- with Maks, since the mirror moves when you focus, it's hard to be precise about the focal ratio in use
- and that's without any changes at the back end

So I've only ever assumed that mine is closer to F/12 than F/11 or F/13

 

[bosun21]

They are the same telescope, with the difference being the dovetail and finder scope positioned differently. They are obviously painted differently as well. What I have been told regarding the aperture discrepancy is that the mirror is indeed 127mm in diameter, but due to the optical design and light path tracing only 119mm is utilized. 
     HTH  

          Ian 

[Stu]

49 minutes ago, bosun21 said:

They are the same telescope, with the difference being the dovetail and finder scope positioned differently. They are obviously painted differently as well. What I have been told regarding the aperture discrepancy is that the mirror is indeed 127mm in diameter, but due to the optical design and light path tracing only 119mm is utilized. 
     HTH  

          Ian 

Actually the whole mirror is used, but the front corrector diverges the light a little bit, so it effectively spills over the edge of the primary. Once you work out how much light is lost, it comes back to about 119mm aperture equivalent. To avoid this the primary would need to have been larger, and likely the OTA too, plus higher weight, so they made the compromise they made.