What way to put focal reducer optics

[rogerg]

This may sound like a stupid question, but here goes nothing.

I have recently taken my focal reducer's optics out of their casing several times, in the process of having my back neighbour engineer up a fitting allowing me to slide the optics inside a 2" draw tube, hence reducing the imaging train & focal length.

I didn't think to note when I took the optics out, which end was at which end of the casing. The sequence of optics and spacers I do know (hasn't changed).

How can I tell if I am putting the optics in the right way around?

I suspected I'd be able to do it by looking at which way around results in magnification vs reduction. However placing the optics a fixed distance from a metal ruler results in undistinguishable difference in magnification (odd?).

I might end up having to install the optics, take photo's, and then try them reversed. But that's all a bit of a pain really and would take a little while.

Roger.

[avandonk]

If your focal reducer is a doublet the more curved surface should face the objective lens.

Bert

[rogerg]

Hmm... it's a Meade F/6.3. I'm guessing a doublet would have 2 lense elements? I think this has 3 from memory. I'll pull it appart again and see if one side is more curved than the other.

Thanks

[mick pinner]

the end with the female thread screws directly onto the visual back.

[Dennis]

I've just had a look at my Celestron F6.3 Reducer/Corrector and all I can say is that the lens surface that would sit adjacent the sensor looks quite flat. The surface that sits adjacent the objective is deeply recessed in the metal cell, so it is difficult to make out its profile.

Cheers

Dennis

[rogerg]

Thanks guy's.

There is a flatter and more curved side. And I had it the right way around, with the flatter side at the male thread end (camera end).

Roger.