Field Flattener Question

[Boggy]

Could anyone recommend a field flattener that might work with a William Optics Zenithstar 110mm F7.0 refractor (the old black and gold model). I've just started trying to do some astrophotography and am getting some curvature, otherwise the results are very good!
The telescope is about 14 years old and uses a standard 2 in focuser.
Thanks for your advice.

[Drac0]

I'm using an Astro-Tech 2" Field Flattener on my 102mm F7 triplet. Designed for F/6 to F/8 refractors so should suit yours.


Cheers,
Mark.

[Boggy]

Thanks for that Mark.
I wasn't sure if it had to be matched to the scope as I've never used one. The Astrotech doesn't change the focal length as well, so will be perfect.

Thanks
Barry

[Drac0]

Just be sure to get the back focus correct or you get some weird effects. They say from the flattener shoulder where the t-ring threads are it's 57mm +/- 4mm but heard people saying they have gone as far as 70mm so you might need a small spacer or two.

[Boggy]

Thanks for the info. I'm using a ZWO 1600MM so curvature isn't as bad as a DSLR would be, but I was impressed at my first try at NGC253, being only a 3 minute exposure. I can see that the photos can be better.