SW Coma Corrector

[lensman57]

Hi,

I have read that the SW coma corrector has a reduction ratio of 0.9X but having looked at the OVL advertising at the back of the Sky at Night magazine it states that there would be  no change in the focal length of the scope while using the SW CC, which one is correct?

Regards,

A.G

[oldpink]

AFAIK it is a 0.9 reducer, I need to get one as well

[Phil Creed]

Dumb question, maybe, but...if you use the 0.9X SW Coma Corrector with a low-power ultrawide like a 30ES-82 or a 31T5 Nagler at f/5, will it vignette, or will it be a gloriously-wide, coma corrected field o' stars?

I've got an 8" f/4.9 Orion OTA that I got in part to have more wide-field capability than the ubiquitous 8" f/6 dobsonians.  The 30ES-82, with its 43mm field stop, produces just shy of a 2.5-deg TFOV.

I'd be curious to see if the 0.9X Skwyatcher coma corrector could yield a 2.7-deg TFOV with this same eyepiece and scope combo w/o vignetting.  As is, I just sent funds in for a used Paracorr-Type 1, which I was planning on using on all my eyepieces, but I'm sorely, sorely tempted to get a coma corrector that doesn't barlow (or slightly reduces) just for the 30ES-82.

Clear Skies,
Phil  

[Uranium235]

I can confirm that the SWCC is also a 0.9x reducer - and will reduce further (if given a longer spacing), but at the expense of the size of the corrected field. If using a camera with a large chip, its better to aim for the correct distance if you want good corners.