[phpBB Debug] PHP Notice: in file /viewtopic.php on line 988: date(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone.
[phpBB Debug] PHP Notice: in file /viewtopic.php on line 988: getdate(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone.
[phpBB Debug] PHP Notice: in file /includes/functions.php on line 4284: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3493)
[phpBB Debug] PHP Notice: in file /includes/functions.php on line 4286: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3493)
[phpBB Debug] PHP Notice: in file /includes/functions.php on line 4287: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3493)
[phpBB Debug] PHP Notice: in file /includes/functions.php on line 4288: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3493)
Webster Telescopes Forum :: View topic - New C-24 f/3
Webster Telescopes Forum
http://webstertelescopes.com/forum/

New C-24 f/3
http://webstertelescopes.com/forum/viewtopic.php?f=8&t=634
Page 1 of 1

Author:  jimwebster [ Mon May 06, 2013 2:24 am ]
Post subject:  New C-24 f/3

We just completed a new C-24.

This 24" scope has a f/3 Kennedy mirror giving an eyepiece height at zenith of only 67" !

Amazing performance using high power on Saturn last night.

Kennedy has just completed a 36" auto-collimator for his optical shop and this mirror is his first creation using the new system.

Attachments:
C24_f_3.jpg
C24_f_3.jpg [ 54.9 KiB | Viewed 15979 times ]

Author:  jimwebster [ Mon May 06, 2013 2:26 am ]
Post subject:  Re: New C-24 f/3

Here is another picture to give you an idea of how tiny this scope really is.

Yes, you are welcome to use these pictures on other web forums, no need to ask.

Attachments:
C24-f3.jpg
C24-f3.jpg [ 52.6 KiB | Viewed 15978 times ]

Author:  lightyear [ Mon May 27, 2013 7:46 pm ]
Post subject:  Re: New C-24 f/3

Awesome.
Looks rock-solid.
Thanks Jim.

Wanting more info on Mr. Kennedy's new auto-collimator.
What is that?
I have no experience in mirror-making.
-David.

Author:  jimwebster [ Thu Jun 06, 2013 5:51 pm ]
Post subject:  Re: New C-24 f/3

lightyear wrote:

Wanting more info on Mr. Kennedy's new auto-collimator.
What is that?
I have no experience in mirror-making.
-David.



The autocollimation or double pass null test is well regarded and widely used in professional optical shops for testing parabolic mirrors.

Like the Ross and Dall tests it is a null test so the ideal parabolic mirror shows straight bands when use with a Ronchi ruling or is seen to darken uniformly when viewed with the knife edge.

However, the test is twice as sensitive as the other null tests as light is reflected off the test optic twice, this makes it a very powerful test. The price to pay for this sensitivity is that the test set up requires a high quality optical flat at least as big as the mirror under test, such an item is difficult to make and very expensive to buy.

With the autocollimation test the mirror is tested at it’s focus unlike the Ross and Dall tests which are at the centre of curvature.

You can read more info at:

http://www.nicholoptical.co.uk/The%20Testing%20of%20Astronomical%20Telescope%20Optics.pdf

Page 1 of 1 All times are UTC - 5 hours [ DST ]
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
http://www.phpbb.com/