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  #1  
Old 31-03-2014, 09:09 PM
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mental4astro (Alexander)
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Gondwana Telescopes - a new choice in dobsonian telescopes

“… I discovered in the heavens many things that had not been seen before our own age.”
Galileo Galili, 1615.

The legacy left by the late John Dobson has given amateur astronomers access to telescope apertures once limited to professional astronomers.

Gondwana Telescopes was born out of using and travelling with telescopes for over 30 years in Australia, the last twenty also creating them. Rutted roads, humid coasts, dry interiors, dust, and close encounters with wildlife on the road spawned an evolution in designs to couple portability to function, balance and robustness. “Stuff happens”, and the heart of our precious instruments needs to be protected. Now “built like a tank” does not need to mean looking like one too.

Introducing “Marana” – a new take on the ultralight dobsonian, totally designed and built in Australia.

Marana, an Australian Aboriginal word meaning “stars”, is an individually handcrafted dobsonian that follows the very principles espoused by John Dobson – large bearing diameters, a balanced optical tube assembly, appropriate material selection and a rigid mount.

Balanced to a wide range of eyepiece weights, ready to plug and play with Argo Navis, sporting a new helical focuser co-designed with Kineoptics, removable secondary mirror with integrated dew heater system, a specially sourced Vixen red dot finder, and a host of optional accessories, Marana is robust and compact enough to pack onto the passenger seat of a coupé, yet packs a considerable 12” aperture.

Launching a new choice in dobsonian telescopes at the 2014 Ice In Space Astro Camp

Gondwana Telescopes – touching the ancient past.
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  #2  
Old 31-03-2014, 09:23 PM
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barx1963 (Malcolm)
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Congratulations on a lovely looking product there Alex. Wish I was going to IISAC to have a look!
Or maybe you can pop down to Snake Valley in Nov to give it a run amongst us Victorian types!

Malcolm
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Old 31-03-2014, 09:33 PM
mercedes_sl1970
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Alex - it looks terrific and beautifully made. Congratulations!

Andrew
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Old 31-03-2014, 09:51 PM
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Octane (Humayun)
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Wow. That's beautiful.

Congratulations.

H
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Old 31-03-2014, 10:01 PM
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Wow, outstanding craftsmanship and design. Top stuff
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Old 31-03-2014, 10:12 PM
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FlashDrive (Poppy)
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Very Nice Indeed......

Col.....
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Old 31-03-2014, 11:06 PM
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AG Hybrid (Adrian)
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Hurrayyyyyyyyy its finished! Doesn't it look great with the lacquer treatment.

Are those the same carbon fiber truss poles before Alex or are they the newer thicker ones you mentioned?

The handle you selected looks good. I like the logo too. That turned out very well.
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Old 31-03-2014, 11:15 PM
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This looks pretty awesome. Can't wait for more details.

Cheers
Steffen.
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Old 31-03-2014, 11:23 PM
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Do you have a total weight for the system , Alex.

It looks like a fairly substantial baffle plate needed opposite the focuser or are you planning to make it standard with a shroud ?
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Old 01-04-2014, 09:46 AM
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mental4astro (Alexander)
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Thank you all for your comments. I take great heart in them.

Adrian, the poles being used now are a totally new set of carbon fibre poles. These new poles are custom made for me, and are significantly more rigid.

Mark, to show EVERYTHING in the very first post would leave room for further surprises!

A light baffle or shroud is not mandatory, particularly when it comes to ultralights. However, I will be offering not one, but two different 'shroud' solutions. To make any one item 'standard' would be presumptuous and shows a lack of understanding of the different priorities one person has to the next, and of the product. Having one solution is fine. Having two gives more choice and flexibility.

Marana comes in at a tick over 21kg. The single heaviest component, the mirror box, is just over 10.5kg - this can be very significant for those people where carrying heavy weights is a concern, as it is not necessary to carry the whole stowed configuration all at once. More cut-outs could have been made to the mount, and even the mirror box, but this would have left the primary mirror unacceptably over exposed. Like mentioned earlier, "stuff happens". When it does, it's those little thoughts that can make the difference.

Last edited by mental4astro; 01-04-2014 at 10:05 AM.
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  #11  
Old 01-04-2014, 09:50 AM
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graham.hobart (Graham stevens)
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Gondwana

Looks Brilliant Alex!
Graham
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  #12  
Old 01-04-2014, 10:24 AM
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AG Hybrid (Adrian)
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Quote:
Originally Posted by Satchmo View Post
Do you have a total weight for the system , Alex.

It looks like a fairly substantial baffle plate needed opposite the focuser or are you planning to make it standard with a shroud ?
When I held it - pre-paint job I think it was 20KG. It didn't have handles then. Its probably even easier to carry now.
Naturally Alex is/has designed a secondary baffle. I believe Alex was going to include a shroud with these scopes as well.

Oddly enough when I was testing it. The secondary baffle wasn't attached(Tested in suburban Sydney, not a dark sky site). It still performed well. Little stray light gets into the focuser. It probably only requires a small baffle.

Edit. Alex post beat me to it.
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Old 01-04-2014, 11:21 AM
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Brilliant Alex, simply brilliant. If I was a visual person, I would grab one in a heartbeat mate!

Your brand needs a slight improvement - I think it would look ridgy-didge if it was hot branded/laser burnt into the ply. THAT would be perfect
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Old 01-04-2014, 11:56 AM
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I think all the comments about lack of need of baffling opposite the secondary are somewhat optimistic.

I have trouble with my own house lighting and neighbors lighting at different viewing positions in the sky bouncing off the flat black area in my tube behind and around the secondary mirror - a problem which fitting a longer hood at the end of the tube fixes. Having said offensive lighting flooding full strength into the focuser from behind and around the secondary, if I had no tube, would completely ruin things .

The trouble with shrouds is that they can get pretty heavy when laden with dew and upset balance.

One way to reduce need for baffling behind the secondary is to mount a baffle stop away from the bottom of the focuser towards the secondary.

Anyway you will fine tune all these things in time when user feedback comes in from all the situations that they are used in.

Look forward to see what forms of baffling are on offer .
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Old 01-04-2014, 12:15 PM
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AG Hybrid (Adrian)
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Quote:
Originally Posted by Satchmo View Post
I think all the comments about lack of need of baffling opposite the secondary are somewhat optimistic.

I have trouble with my own house lighting and neighbors lighting at different viewing positions in the sky bouncing off the flat black area in my tube behind and around the secondary mirror - a problem which fitting a longer hood at the end of the tube fixes. Having said offensive lighting flooding full strength into the focuser from behind and around the secondary, if I had no tube, would completely ruin things .

The trouble with shrouds is that they can get pretty heavy when laden with dew and upset balance.

One way to reduce need for baffling behind the secondary is to mount a baffle stop away from the bottom of the focuser towards the secondary.

Anyway you will fine tune all these things in time when user feedback comes in from all the situations that they are used in.

Look forward to see what forms of baffling are on offer .
The draw tube baffle idea is good one. However, you can't attach it to the end of the draw tube because it is threaded for screw on filters in this case.

I believe this ultralight/ultra portable scope will be marketed primarily for very easy transport and setup to and at a darksky site. (Did that sentence make sense? Makes sense in my mind anyway?) If your observing location has extraneous light going straight into your focuser or washing out your secondary mirror. Perhaps this scope is not for you?

That being said. From these pictures alone your not getting the full picture of Alex's design capabilities. No doubt Alex wants to leave some of the extra features and innovations a surprise for the unveil at IIAC that overcomes problems you have mentioned.
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Old 01-04-2014, 12:21 PM
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mental4astro (Alexander)
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Quote:
Originally Posted by Satchmo View Post

One way to reduce need for baffling behind the secondary is to mount a baffle stop away from the bottom of the focuser towards the secondary.
Mark, this is a great suggestion! I'll look into something with this. Could prove a stroke of genius.

As you mentioned yourself, under urban skies all open truss scopes have a distinct disadvantage with stray light entering the focuser. Under dark sky conditions things can change more to a balance compared to a solid tube. No baffling is even possible.

If you are considering a highly portable dob, this type of thing is something that has already been considered, and are happy to deal with & the various solutions. Otherwise no open truss scope would be in the running for consideration. All scopes are a compromise somewhere. It then falls upon the individual to decide what properties are most important for them.

Thanks for the suggestion

Edit: Adrian, yep, I'm leaving a few things up my sleeve
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Old 01-04-2014, 12:34 PM
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Hi Alex

You can mount a baffle plate on two posts which can be screw into the focusser board and removed for transport or something similar

Here is Mel Bartels online baffle calculator.

http://www.bbastrodesigns.com/baffle.html

( Edit : this calculator seems to assume a baffle behind the diagonal mirror too )

Come to think about it , a single baffle could only be used to fully baffle the centre of the field at the expense of causing vignetting at the outer edges.

A rear baffle can be made of very thin aluminum and needn't add much weight .


I agree that for sake of portability end user must decide what is important for them . The more effectively it can be baffled the wider the market though .

Watching your project with interest.

Last edited by Satchmo; 01-04-2014 at 12:57 PM.
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Old 01-04-2014, 12:35 PM
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Quote:
Originally Posted by AG Hybrid View Post
From these pictures alone your not getting the full picture of Alex's design capabilities. No doubt Alex wants to leave some of the extra features and innovations a surprise for the unveil at IIAC that overcomes problems you have mentioned.
I appreciate that aspect Adrian , thanks.
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Old 01-04-2014, 01:12 PM
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acropolite (Phil)
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Looks very nice, the big question is how much and what if any other sizes will it be made in.

I assume that Plug and Play with ArgoNavis means encoders are either fitted or appropriate mounting points have been integrated.
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Old 01-04-2014, 01:16 PM
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Nice one Alex! Look forward to seeing it soon
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