TheSkySearchers

I am awaiting delivery of a step-down adapter for my 2" eyepieces. It will allow me to use my 2" eyepieces in a 1.25" focuser. The 2" eyepieces I would like to use in my 8" f/7.5 Newt are my ES 20mm/100° and my ES 30mm/82°

My question is, will there be visible effects created by this adapter? If so, what might they be?

Thanks

PS. I have a 2" R&P focuser that I could install on my Newt, but I'm not ready to do major surgery on that scope, yet.

You can expect some vignetting for 2" eyepieces with field stops larger than the inner diameter of the adapter.

The adapter arrived today, but guess what... it's cloudy!

With 1.25" adaptor ES100 20mm will have FOV just under 80 deg and ES82 30mm around 50 deg.

Hi Andrey,

Did you use 1.25" as a new field stop of sorts to get those numbers?

JayTee wrote: ↑Fri Mar 25, 2022 7:42 pm Hi Andrey,

Did you use 1.25" as a new field stop of sorts to get those numbers?

I have used 27mm - max field stop for 1.25" EPs. I know it is not as simple as that since you will see the FOV gradually loosing brightness at the edge instead of sharp field stop.

Hi Jay Tee

You might also get some internal reflections from the eyepiece barrel and some UW eyepiece designs are negative eyepieces, the field stop is not in front of the front element. Use of an adaptor will force the eyepiece to sit high off the tube wall. You will need a high focal point above the focusser to be able to reach focus.

The only light loss IMO will be vignetting.
Joe

I suspect you won't be able to achieve focus because the eyepieces will be pulled out of the focuser too far.