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Old 16-05-2007, 03:11 AM
ausastronomer (John Bambury)
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Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
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Quote:
Originally Posted by Starkler View Post
Hi John I was with Dave observing one night when we did a bit of a comparison between his 12t4 vs his 22mm panoptic barlowed. This was in a 10" f5 dob.
The nagler didn't look bad until we compared with the barlowed panoptic, which was much much sharper.
Geoff,

I don't doubt this. The Panoptic is working at F10 with a 2.5 metre focal length, the Nagler is working at F5 with a 1.25 metre focal length. I believe 12mm Nagler T4 works progressively better in longer focal length scopes. It performs a lot better in my 18"/F4.5 which has a 2.1 metre focal length, than it does in the 10"/F5 with its 1.25 metre focal length. Combined with a paracorr it performs superbly in both scopes.

Quote:
Originally Posted by Starkler View Post
I have mentioned this over on CN and some others have noted that they didnt think the t4's were as sharp as some others. Others of course said there is nothing wrong with a t4. I guess its not wise to draw conclusions on a sample size of one, but I'd love to repeat that test with another 12t4.
Nothing new here. Blind Freddy can quickly figure out the T4 Nagler's (all of them) in fast and short focal length systems are far from perfect in their EOF performance. They are still good. They are designed with longer eye-relief and the softness at EOF is the trade-off for the longer eye-relief. When combined with a paracorr all of the T4 Naglers are superb, although IMO a touch behind the Pentax XW's, in most respects apart from AFOV.

CS-John B

PS: Read my post re the new Televue Ethos
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