#41  
Old 08-09-2016, 12:24 PM
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troypiggo (Troy)
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Originally Posted by OneCosmos View Post
I am sorely tempted to exchange my APM 152 for the new f7 180mm from APM. Markus has agreed but we're talking another $17k-more than $500 per mm😫
Recollecting our chat about this up at Astrofest.
Understand that aperture is king, but is the cost/benefit ratio there?
Other question is do you find the 152mm is limiting you in any way?
Keep the 152 I reckon, and just get out and enjoy/use it more
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  #42  
Old 08-09-2016, 03:04 PM
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Originally Posted by MattT View Post
Lots of time to work it out. Zane sold a 180 f8 recently. The only Istar lens that I have heard of that wasn't perfect.
They are bargain basement price achromats priced to compete with USA made D and G lenses - it would be not unreasonable to assume that less than perfect glass gets through occasionally and the lack of experience of the owners will often give them a bit of lattitude . If not they simply couldn't sell them so cheaply ( I am making assumptions there as I haven't had any direct experience with them )

Last edited by Satchmo; 08-09-2016 at 03:15 PM.
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  #43  
Old 08-09-2016, 06:55 PM
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strongmanmike (Michael)
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Well I only have two things to say in this thread

1) I spent many nights observing through the 9" Oddie refractor at Mt Stromlo over several years, before it was tragically lost in the 2003 Canberra bushfire , including having my 12" LX200GPS setup outside for direct comparison one night... and the views were definitely grander with better separation of close stars and planetary features, globular cores and kinda more meaty through the Oddie.. overall image brightness and visibilty of galaxies and faint nebs etc was fairly comparible.

2) See 6" of Astrophyiscs genius HERE

Mike
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  #44  
Old 09-09-2016, 09:25 AM
Hodur (David)
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Originally Posted by anj026 View Post
For professional achromats 100-150 years ago it is traditional for them to be f15 or thereabouts. I think there is a benefit in the long focal ratios in terms of depth of focus. For a more detailed analysis please have a look at this link to Neil English's article.

http://www.cloudynights.com/page/art...-fiction-r2452
The Neil English article resolves many questions re: Classic Achro's. Great thread, great article. Cheers
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  #45  
Old 10-09-2016, 07:14 AM
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OneCosmos (Chris)
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Quote:
Originally Posted by troypiggo View Post
Recollecting our chat about this up at Astrofest.
Understand that aperture is king, but is the cost/benefit ratio there?
Other question is do you find the 152mm is limiting you in any way?
Keep the 152 I reckon, and just get out and enjoy/use it more
Yeah Troy that sounds sensible enough and anyway, right now my outgoings vs income preclude such indulgence. The thread was mainly started to find out how many refractors larger than 152mm are extant in Australia. I'd still love to look through something larger.
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  #46  
Old 13-09-2016, 11:50 AM
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I looked through the Oddie II yesterday......
albeit only at a wall at Mt Stromlo, this is a 220mm F15 achromatic doublet refractor built by Tim Wetherell. It is housed at the new Mt Stromlo Visitor Centre and may eventually be moved into the Oddie Dome for public outreach. The objective was made my iStar Optics.

It is a big and beautiful recreation of the original which now is also displayed at Mt Stromlo.
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  #47  
Old 13-09-2016, 05:48 PM
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dannat (Daniel)
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Melb obs 8" f13 is obstructed by inner city light pollution, it would be good to get it out to dk skies. has quite small amounts of colour on the gas planets but a fir bit around bright stars, venus & the moon depending on ep & axis
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  #48  
Old 14-09-2016, 06:17 AM
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220mm F15 iStar lensed Oddie II awaiting its mount to be restored..... one day...
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  #49  
Old 14-09-2016, 03:11 PM
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Looks very `steam-punk' with all those riveted steel panels !
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  #50  
Old 15-09-2016, 06:55 AM
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Looks very `steam-punk' with all those riveted steel panels !
I am very tempted to make a 1:3 scale version of this scope, I have the right objective in heavy brass cell. Might need to quiz Mr Mitchell to see if he can roll tapered tubes..........
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