Istar best achromat for big refractor build ?
Posted 08 September 2013 - 06:03 PM
I wonder if there are any other brands of objectives that can match them for price/quality?
We don't have much choice here in Australia so hopefully some European or USA members can chime in here.
I am considering 8" F8 or larger.
Many thanks in advance.
Posted 08 September 2013 - 09:13 PM
Posted 08 September 2013 - 09:19 PM
There is the APM 203/1800 with TMB designed lens that would be wonderful but at a much greater cost.
My conclusion is to do the ATM thing with an 8" lens from Istar or else go for a high end ATM dob (Royce, Zambuto, Lockwood etc.) 10 or 12" for similar cost.
Before any of that I need to catch up on my current projects.
Posted 08 September 2013 - 09:21 PM
[note: post edited by FirstSight]
Posted 08 September 2013 - 09:35 PM
I have a decent 8" f6 mirror that needs a re-coat but it will cost over $300 so it is on hold for now. I can buy a new GSO mirror for that or a new Royce mirror for under a $1000 delivered.
Posted 09 September 2013 - 12:16 AM
It is more of a scope building exercise and an achromat is more than sufficient, I have no need for TECs or other APOs, my TAK TSA is fine for those purposes. Reflectors really aren't my thing (although I intend to build one at some stage).
Posted 09 September 2013 - 12:39 AM
[note: Post Edited by FirstSight]
Posted 09 September 2013 - 01:48 AM
An 8" would be have been my choice if I had a mount to take it. As you know I'm doing a 6" f12.
Locally available is 203mm 3mm thick drawn aluminium pipe that would hold an 8" beautifully.
I would go for as long an FL as you could and would get an Istar R 35 f12 objective would be the one I would choose.
Why oh why when you ask which refractor objective to get the reply from some is...get a dob....
Posted 09 September 2013 - 02:47 AM
I have the enormous Gaunt Mount c1865 that will easily carry anything I can build, I'll look into the 8" lens. Looks like Istar has no competition as I think the others only sell complete scopes.
I'm trying to finish the other refractors so I can start the big project.
Posted 09 September 2013 - 06:10 AM
You should go for the Istar 8" F12 R30 lens....
If your mount can take it........
Posted 09 September 2013 - 06:12 AM
You can buy the APM TMB lens in cell only however it is 2850 Euros.
There is D & G but only in f12 or longer.
Then there is Barride Optics from China. I would expect them to be less expensive than Istar and I have no direct experience.
Other than those you are left with waiting for a secondhand lens to pop up on the classifieds or Astromart.
Posted 09 September 2013 - 10:11 AM
Posted 09 September 2013 - 10:51 AM
The 'R' works.
Posted 09 September 2013 - 05:01 PM
Posted 09 September 2013 - 07:25 PM
The APM looks tempting but I think the $$$ might be vetoed by the Finance Minister.
Posted 09 September 2013 - 07:58 PM
I'd love the 8" f8.8 myself but have not the mount. I'm now looking at the 5" f12 r30
Great scope, rides very well on my G11. Works well with all the eyepieces I have. Depth of focus on the f12 is great for double star work.
Posted 09 September 2013 - 08:07 PM
Posted 10 September 2013 - 06:16 PM
Posted 10 September 2013 - 06:48 PM
Posted 10 September 2013 - 07:46 PM
Just a generic question, but why not an 8" F16 for super planetary type work? is the mounting issues of such a long tube the main problem? FL would be like 3200, so not too much in terms of magnification... Just wondering why nobody builds longer FL than F12 generally?
Think about the mount you'd need for that 8" lever. And think about where you'd house it. All big stuff.
Posted 10 September 2013 - 08:36 PM
If I had a mount like your beautiful 'Gaunt' I would definatly look at the 7.1 inch f8 or f12 slim , R35 by Istar and if these are as good as I hear you will be right by one of these .
One of these would keep the weight down as well .
By the way here is a shot of Venus taken last Saturday night in my Istar 127mm f8 achro , this is raw , no work except a small zoom and crop with sizing for CN's .
Great objectives .