3 replies to this topic

[Philler]

I recently replaced my old helical focuser on my 10 in. Dob. with a new JMI Event Horizon 3 Newtonian single speed focuser.  I have always liked the JMI DX3 that came with my 12.5" Dob as it is really smooth operating.  But this new JMI EV 3 on my 10 in. Dob  seems kind of stiff turning the focus knobs and doesn't really move smooth.  Is there anything I can do, short of taking it apart, like putting some lithium lube on it?  Or is there just a break-in time on it like a new pair of shoes?

Edited by Philler, 04 July 2020 - 08:44 PM.

[macdonjh]

I don't know if you have this exact focuser:

https://optcorp.com/...-for-newtonians

 

But I'll bet there is a thumb screw like the black one near the dual speed knob on the right-hand side of the reduction gear housing in the attached link.  I think that is a "tension adjustment" screw.  If you loosen that ****'re focuser should move more easily, but carry less weight without slipping.  If you tighten the screw it will be harder to move but will carry more weight without slipping.  The trick is to get just the right balance.

 

I don't recommend lithium grease for any astronomy application.  It separates too easily and makes a mess.  SuperLube is the default recommendation on CloudyNights.  Personally, I've had good luck with Mobile1 synthetic (likely too heavy for a focuser) and a synthetic grease I bought for my bicycle.  I have no idea what that one is called, though.

[Philler]

Thanks Mac.  Your pic. is actually not the model I have.  I have contacted a JMI rep for his advise on this matter to get their advise on a solution to this.

[Philler]

The JMI rep said to loosen each of the four set screws/bolts at each corner of the focuser shaft a little each one until the focuser turns smoothly. This worked and my JMI EV 3 focuser turns smoothly. Thanks.