View Full Version here: : Siebert Barlow

18-03-2007, 11:51 PM
Hi All,

Looking for some information here on these Barlows.

1. Are there any local suppliers? In Sydney or elsewhere in Australia.
2. What is the difference between Telecentric and the usual Barlow listed?
3. I am considering one of these two any one have any experience with these
a. 1.5x, 2.0, 2.5x, 3.0x Barlow: $149 (BAR1530)
b. 1.5x-2.0x- 2.5x 1.25" $199 Modular Telecentric (BAR125-1525X)

The reason for the modular is they seem to be a good buy when you consider you pay a lot more to buy these same powers individually.

A. seems to offer more powers, but b is Telecentric, not sure what this is and if this offers much advantage over the other.

Offtopic a bit.
Lastly I have a 5x Powermate and I noticed I can remove the lower part of the 5x. What is this for? There appears to be a lens or lens's in both the upper tube and in the lower tubes. I ask as I wonder if this separation can be used to reduce the power of the 5x down to a lower mag.


19-03-2007, 07:48 AM
John (astronut) has recently been looking into these, and bought one of their barlows recently - direct from Siebert in the USA. Maybe he'll see this and respond to your questions.

19-03-2007, 10:32 AM
Hi Fahim,
I recently bought the telecentric 2X barlow and the 17mm Ultra e/p direct from Sieberts in the the U.S.
The reason for the telecentric is firstly and simply a better product than the cheaper one offered.
The more technical reasons are this, If you have a "fast" scope, F5 or faster the light cone is a lot "fatter" than a slower scope of the same aperture.
A barlow that is configured for anything slower than F6 will still work on a fast scope, but because of its design a lot of the light cone is wasted.
The telecentic and other high end barlows are configured for the fast light cone, subsequently giving you as bright an image as possible.
Harry Siebert is always available to help you pre & post purchase.
Del is about 10 ten days.
I hope this helps.
Cheers, John.:D

19-03-2007, 10:53 AM
Thanks John, looks like the Telecentric from reading there website is on the same par as the TV Powermate. But would I need it for a 8" F10 SCT? Or would the Barlow be sufficient? As you suggested the advantage of the Telecentric is in fast scopes.


19-03-2007, 11:16 AM
Even though the telecentric is designed for the fast scopes, it works just as effectively on the slower scopes, and because of its design it's superior to the other barlows.
This doesn't mean though, that the other barlows won't work well on your scope.:D

20-03-2007, 11:34 AM
Just noticed T&A seem to be listed as the Australian dealer on there website. I will give Matt a call and see what he can get in and for how much.