SW 100ED Refractor reducer/Flattener?

[Chris M48]

Hi Guys,

Will my SW 100ED .85 Reducer/Flattener also be ok for Evostar 120ED?

Basically because £185 is a lot of money if not necessary.

Thanks,

Chris

[Adam J]

1 hour ago, Chris M48 said:

Hi Guys,

Will my SW 100ED .85 Reducer/Flattener also be ok for Evostar 120ED?

Basically because £185 is a lot of money if not necessary.

Thanks,

Chris

Do not 100% quote me on this one but I strongly suspect that its all the same flattner with the 0.85x. I know that the 72mm 0.85x flattener and the 80mm 0.85x flattner are no different at all, I assume that the 120ED one is also no different. 

[parallaxerr]

I'm not so sure, the 100 is F9 and the 120 is F7.5. I wonder if it's possible to check by part number?

Edit: they have different part numbers on FLOs website, though I don't suppose that's definitive proof of any differences. Maybe drop FLO a message?

Edited September 12, 2019 by parallaxerr

[Chris M48]

Thanks fellas, as I shall have both telescopes for a short while, I will hold off on purchase until I’ve tried it out, I’ll probably ask FLO guys anyway.

Clear skies.

[Louis D]

You could try adjusting the spacing between the flattener and sensor if it doesn't look good at the edges.  As long as it requires more distance you're okay.  If it requires less distance, you're probably out of luck.  Unfortunately for you, field curvature increases with decreasing focal length in refractors regardless of focal ratio (roughly 1/3 of focal length).  Thus, your 100ED will have more field curvature than your 120ED, so a 120ED flattener will be less aggressive with the same back focus, so it would require greater separation to work in the 100ED.  I'm pretty sure your 100ED flattener is more aggressive than a 120ED flattener would be and would require less separation to work in the 120ED.