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  #41  
Old 01-10-2020, 12:44 PM
Hemi
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Gents, maybe not a purists scope, but do any of you have an opinion of the ioptron 150 RuMak? Iíve been seriously considering it but not much out there about it that I could reliably find.

The current SW 150 in the classifieds is also tempting.

....it would be my first foray into Maks.

Cheers

Hemi
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  #42  
Old 01-10-2020, 02:41 PM
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mental4astro (Alexander)
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Hemi,

A Rumak Maksutov has a secondary that is separate from the corrector plate and has its own collimation screws. If the secondary is a silvered spot on tbe corrector it is not a Rumak but a Gregorian Maksutov, just like the Skywatcher maks, and the secondary is not individually collimateable.

The advantage the Rumak has over the Gregorian is the separate secondary offers the scope maker great flexibility in the design parameters and correction of the primary too.

Last edited by mental4astro; 02-10-2020 at 12:35 AM.
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  #43  
Old 01-10-2020, 03:42 PM
Hemi
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Thanks Alex,

They have certainly advertised it as a RuMak, hence my interest. In fact sidereal trading have as well. I read the manual after your post, and youíre correct in that collimating is via the rear cell only, no mention of the secondary.

It is puzzling though as it clearly states a RuMak type secondary mirror, not a silvered spot on the corrector as in Gregorians.

Cheers

Hemi
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  #44  
Old 01-10-2020, 04:14 PM
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GUS.K (Ivan)
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I remember a thread on CN regarding the ioptron Maks, they had an issue regarding the secondary mirror sliding out of position they are apparently glued on.
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  #45  
Old 01-10-2020, 09:38 PM
Buck
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These iOptrons are definitely a Rumak design. They were reviewed by Dennis di Cicco in the Nov 2011 Aust Sky & Telescope, and to quote the reviewer "The scope is a Rumak design, meaning that the secondary mirror is a separate optical element glued to the inside of the strongly curved Maksutov corrector ...."
They have three sets of collimation push-pull screws sealed under dust plugs at the rear of the primary mirror and come with a dual speed focuser that has an internal pre-load that prevents any "mirror shift" that can occur with the SW versions.
They are very rugged - I accidently dropped mine (onto soft lawn) and there was no damage or change in collimation.
Haven't heard of or experienced any secondary mirror "slippage". They do get a good report/review in Aust S&T and also in Astronomy Now back in 2010.
Under-rated in my opinion......
Buck (Paul)
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  #46  
Old 01-10-2020, 09:45 PM
Hemi
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Thanks Buck, for the clarification. My reading had certainly pointed me to that conclusion...

As I said earlier, I’m very tempted.

Hemi
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  #47  
Old 07-10-2020, 02:32 PM
Steve Pattie (Steve Pattie)
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I have had in storage for a few decades now a Mak (just under 7.5") made by the Australian optician Bill James of Melbourne. As far as I know it is a one of a kind.
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Click for full-size image (Mak by Bill James.jpg)
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  #48  
Old 07-10-2020, 02:49 PM
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Quote:
Originally Posted by Steve Pattie View Post
I have had in storage for a few decades now a Mak (just under 7.5") made by the Australian optician Bill James of Melbourne. As far as I know it is a one of a kind.
OMG! A rogue Unicorn!

Steve, WOW! That's all I can say!

Do you have any other specs about it, such as focal length? What size focuser does it have, 1.25", 2"? How much does it weigh? Any coatings on the optics?

I haven't heard of Bill James. Any details you can share about the man? Not his phone number... , but his work.

Any chance of a few more pics? Down the OTA, the rear, mounting plate, etc, would all be great to have a squizz at!

And of course, how does it perform???

Damn I'd love to get a look through it! But it's too far away...

Alex.
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  #49  
Old 07-10-2020, 06:46 PM
Saturnine (Jeff)
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That is an interesting scope to come out of the closet, after being in storage for so long is there any thought of putting the scope on the market. An Aussie made Mak , like Mental, I would love to know the specs on the scope and any test results.
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  #50  
Old 07-10-2020, 08:05 PM
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Quote:
Originally Posted by Steve Pattie View Post
I have had in storage for a few decades now a Mak (just under 7.5") made by the Australian optician Bill James of Melbourne. As far as I know it is a one of a kind.
Back in the early 90s I purchased what I believe to be the last two 8" borosilicate meniscus blanks from the batch that was used by Bill James to produce this scope. I have turned one of the blanks into a 7.5" Gregory (not Gregorian as there is no such thing) Mak, in the mid 90s. That scope is somewhere in Europe these days, but I still have the second meniscus blank and would be very happy to part with it if someone wants to swap it for a 10" Pyrex blank.
Bill James was the most prominent optician in Australia until his death in 1995. He is mostly known for making the large Wynne corrector for the AAT and the laser reflectors for the Optus B satelites.
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  #51  
Old 08-10-2020, 11:55 AM
Saturnine (Jeff)
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Stephan

Thanks for the background info on the Bill James Mak, sounds like it should be a good performer , going by the opticians credentials you mention.

Steve Pattie
Please tell us more about the scope and how it performed on the planets etc.
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  #52  
Old 08-10-2020, 07:56 PM
Steve Pattie (Steve Pattie)
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Hi Alex,

The Mak is for memory f/15 and comes with an older style 1 1/4" focuser. There are no coatings on the optics and its weight is 7kg.
Stefan gave some stats for Bill James, Australia's best optician who emigrated to Australia from the UK with his young family. He had a workshop in Camberwell and he has made up to a 40" mirror for someone in Tasmania (my memory is a little hazy on that one) - it was still on his work table when I visited him. He also remade the optics of the Govt 8" refractor at the Old Melbourne Observatory making exact test plates of the original glass to reproduce the exact figures they had even though he said that the design wasn't optimal. On my last visit there, he showed me the Mak and gave me a price for it, which I snapped at - $1000 some 20+ years ago.
Unfortunately due to the tube design, I didn't have a mount to put the thing on and still don't, so I have never looked through it in all this time.
I'll take some snaps of it over the next few days to show you.
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  #53  
Old 08-10-2020, 09:57 PM
Saturnine (Jeff)
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I am looking forward to seeing more photos of the Mak and possibly more dimensions of the tube if it is not too much to ask.
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  #54  
Old 09-10-2020, 10:15 AM
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blindman (Neville)
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One near you
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  #55  
Old 09-10-2020, 11:46 AM
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It would certainly be very interesting to compare the Bill James made 7.5" Mak with a current Skywatcher made 7". Of course there will be difference due to the lack of anti-reflection coatings on the 7.5", and the image will be a little dimmer because of the age of the scope, but the relative optical quality of each instrument will most certainly be on show.
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  #56  
Old 09-10-2020, 11:58 AM
Steve Pattie (Steve Pattie)
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Here are some more pics of the Mak Bill James made. It appears that the focuser has either been modified of custom built.
The overall length of the optical tube is 494mm and the OD of the front cell is 213mm.
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Click for full-size image (Mak by Bill James Orig2 small.jpg)
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  #57  
Old 09-10-2020, 06:24 PM
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mental4astro (Alexander)
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Thanks for the pics and specs, Steve.

I'd jump at the chance to have a look through it. Looks a treat for sure.

Alex.
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  #58  
Old 09-10-2020, 11:08 PM
Steve Pattie (Steve Pattie)
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Heh Alex, that may one day be possible. Let me work on something first.
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