Posted: Sat Oct 28, 2006 6:33 pm
Upz...still looking for an astro cum birding owner... 
Is this the ZS66 Petzval ED? Just realised that we both are horses.Airconvent wrote:upz..
Price adjusted to $600. Final.
Thanks for reading.
SingAstro
Singapore Astronomy Forum
http://www.singastro.org/forum2/
FS: William Optics Zenithstar 66SD Doublet APO - SOLD
Page 2 of 4
Posted: Sat Oct 28, 2006 7:06 pm
Posted: Sat Oct 28, 2006 9:28 pm
No.The Petzval is a 66mm "semi-apo" scope.Kim Miau wrote:Is this the ZS66 Petzval ED? Just realised that we both are horses.Airconvent wrote:upz..
Price adjusted to $600. Final.
Thanks for reading.
William Optics uses this term to describe their achromats that have better colour correction than normal.
The one I am selling is true APO scope. Price difference is substantial.
You can check out the difference on the WO website.
We may be horses but I think you should be at least one cycle younger than me! cheers
Posted: Sat Oct 28, 2006 9:33 pm
Do you mean that the Petzval has better optics than the APO? Yeah, I am younger than you by 2 cycles.
Posted: Sat Oct 28, 2006 9:38 pm
Actually the other way round. The Petzval is not an APO scope, that is why it is so much cheaper. I think the design was primarily optimised for astrophotography, not visual.Kim Miau wrote:Do you mean that the Petzval has better optics than the APO? Yeah, I am younger than you by 2 cycles.
APO scopes uses a mix of quality optics and design to achieve as little chromatic aberration as possible. Inspite of this , though, WO has amongst the cheapest APO scopes around.
Posted: Sat Oct 28, 2006 9:39 pm
If Petzval is optimised for astrophotography and visual use, it should be better than a APO, I am confused...
Posted: Sat Oct 28, 2006 9:43 pm
sorry, I just edited my earlier post due to error.Kim Miau wrote:If Petzval is optimised for astrophotography and visual use, it should be better than a APO, I am confused...
Posted: Sun Oct 29, 2006 1:51 pm
I got it. Is APO designed for both astrophotography and visual?
Posted: Sun Oct 29, 2006 3:02 pm
Hi,
A scope design for Astrophotography will have "fast" focal ratio, flat field and produce a large image circle... it may not need to be an APO.
A scope design for visual use can also be use for Astrophotography, but it'll not as convenient as a scope design for Astrophotography... you may need a separate field flattener, a focal reducer and the may have some vignetting if use on large CCD sensor.
Anyway, please create a new thread if you have more question on this in the "Equipment Discussions" section. This section is for "Buy and Sell", so is limited to enquiry only.
Thanks and have a nice day.
The Petzval design is use to reduce the effective focal length and to reduce or eliminate curvature of field of a telescope. Since it produce a flat field (CCD sensor surface is flat) and short focal length ("fast" focal ratio), it is very suitable for Astrophotography. Also, it can be an APO scope if design to do so (eg. Televue NP-101, NP-127 & Takahashi FSQ-106).If Petzval is optimised for astrophotography and visual use, it should be better than a APO, I am confused...
IMHO, any scope can be for Astrophotography... the only question is it more convenient to do so??I got it. Is APO designed for both astrophotography and visual?
A scope design for Astrophotography will have "fast" focal ratio, flat field and produce a large image circle... it may not need to be an APO.
A scope design for visual use can also be use for Astrophotography, but it'll not as convenient as a scope design for Astrophotography... you may need a separate field flattener, a focal reducer and the may have some vignetting if use on large CCD sensor.
Anyway, please create a new thread if you have more question on this in the "Equipment Discussions" section. This section is for "Buy and Sell", so is limited to enquiry only.
Thanks and have a nice day.
Posted: Sun Oct 29, 2006 3:10 pm
Oh ok, thanks for your information. Sorry for disturbing your thread.