Flattener for WO 66 Petzval?

[daz]

I have the above scope and want to give it a go this season with my CCD camera.

Can someone recommend a flattener for it? It needs to have a decent amount of back-focus to account for my OAG, so the DSLR standard of 55mm will not be enough

Any suggestions?

[ollypenrice]

The whole point of a Petzval is that it doesn't need a flattener. With two front and two rear elements it has a naturally flat field. You can focally reduce a Petzval and, if you do so, you'll need to respect a certain chip distance. If you run the scope at native FL you'll get a flat field and simply have to focus. (How big a flat field, in this case, I don't know. The information will be out there in netland.)

So that's good news. Not so good is that the 66 Petzval, from what I've seen on the forums (some time ago) is that it isn't terribly well colour corrected and gives purple haloes on bright stars. Hey, perfect optics don't exist. See what you get. 

Olly

[daz]

Thanks Ollie - I didn't realise the Petzval didn't need flattening!

As you say, I'll give it a go and see what happens