Flattener or not - 102mm triplet

[Drac0]

Using a Saxon 102mm F/7 triplet and an ASI294MM Pro. I've been using this setup with a 0.8 flattener/reducer and all is good. But I also want to use it at it's full focal length and was wondering if, with this combo, do I need to use a flattener? I have a plain flattener, but if I don't need it I would prefer to keep it out of the imaging train. Is it a necessity? Should I just test it with/without? Thoughts, tips, suggestions?

Cheers,
Mark

[Nikolas]

Yes you still need a flattener otherwise you will get that curvature/eggs at the edges, unfortunately it is a necessary evil

[Drac0]

Thanks Nik, was just wondering as I have read somewhere that depending on the setup you may not need a flattener as the camera FoV doesn't get to the edges of the lens.
Cheers

[glend]

Well how big is the f7 imaging circle? How big is the camera circle? You could just try it to see if it is acceptable. You can always crop out the edges if necessary. Most likely it would be fine for centred objects.

[xelasnave]

I was going to suggest the same, I have thought about doing similar with the 115mm and using it for galaxies...like you could crop fifty percent and still have your object and background for many galaxies.

I think it is worth testing and determine where the stars start going funny.

Alex

[Drac0]

Certainly do need the flattener after testing it. I do like to have the edges if I'm imaging something large without much cropping space.

[Nikolas]

The Orion field flattener works well with this scope
https://www.bintel.com.au/product/orion-field-flattener/
Pretty sure you can get it cheaper if you import it from OS this or its equivalent, first light optics also sell field flatteners for these types of scopes

[Drac0]

I've got an Astrotech one that works well, was just trying to avoid using it. :)