Ethos and Paracorr

Those of you that have or have used an Ethos are aware that when using it in a 2" device whether a diagonal alone or Paracorr that it requires considerable refocus travel from most any other Nagler. (I have not tried them all). Because of this I have placed a 2" parfocalizing ring on it to get it in the neighborhood. My question is how is this likely to affect the recommended paracorr setting of Mark 5 that Televue recommends for the Ethos? :S

DanL

I would think you can just measure it with a ruler.
Set it up the way TeleVue wants, and then measure
from the bottom of the ParaCorr to the top
of the Ethos.

Then put your parfocalizing ring back on there,
and see what ParaCorr setting gets you back
to the correct original distance.

The recommended Paracorr setting of 5(minimum height of tuneable top) is for when you use the Ethos in 1 1/4" mode. For 2" mode the Paracorr setting of 1(maximum height) is recommended.

Note that you should not need to refocus hardly at all when switching between a nagler and the ethos in 2" mode in the paracorr. Lets say you have a nagler 26mm T5. With paracorr set to 3, and focuser adjusted for nice pinpoint stars, remove the 26T5, adjust the paracor setting to 1(max height) and insert the ethos in 2" mode. There should be very little readjustment of the focuser neccessary.

The reason for this is that the whole purpose of the paracorr tuneable top is to account for the different positions of the eyepiece focus planes and move them to the optimal 54mm above the paracorr lense. So, once you know the correct paracor setting for one eyepiece and have the focus adjust for it, you can lock the focuser in place and stick in any other eyepiece and "focus" by moving the tuneable top and you will arrive at the correct paracorr setting for that eyepiece.

In effect the tunable top makes all your non-parafocal eyepieced parafocal to the paracorr once the tunable top is adjusted correctly for each eyepiece.


OK. getting back to your question of a parafocalizing ring...
You didn't mention which nagler you were trying to get parafocal with, but as an example to make the ethos parafocal with say the 17T4 and 26T5 you would need to add a 1/4" thick ring. Then the paracorr setting would be 3, same as for the 17T4 and 26T5 naglers. Whatever nagler you make the ethos parafocal with, you can use the known paracorr setting for that nagler.

Hope this makes sense.