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A tip for using Zooms in Binoviewers

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#1 Eddgie

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Posted 02 August 2019 - 12:47 PM

This is "old" news, but as I have noticed that there have been a lot of people join the forum in the last few years, I thought I would refresh the knowledge base on this.

 

The resistance of the zoom mechanism can put enough torque on the diopter adjustments of many binoviewrer that the diopter will turn.   To prevent that, the natural inclination is to use one hand to zoom, and use the other to hold the diopter against rotation. 

Here is the method I use when the zooms will be in the holders for a planetary session or other duration that you would consider more than a quick use.

 

The first step is to put the eyepieces in, make sure they are fully bottomed, then clamp them.

Next, bottom both diopters and tighten them hand tight against their bases.  You do not need a lot of torque.  You only need a little more than the torque required to turn the zoom.

 

Next, focus the telescope for each eye to determine the eyepiece that requires the most inward movement of the telescope focuser.  Once you have determined the eye that takes the most inward travel, lock the telescope focuser so that it won't move.

 

Now, loosen the opposite eyepiece and while viewing though it, extract it slowly until you find the place where this eyepiece is in perfect focus.  Usually this will only be a millimeter or two. Once you have it in focus, tighten the retaining screws or collar so that the eyepiece is locked into this adjusted focus position. 

There you go, you are all set.   When you need to zoom, you no longer have to worry about the diopter changing and you can use one hand on each eyepiece and zoom them together.   

 

If the zooms are not parfocal, you will need to release the telescope focuser.  It was only necessary to tighten it when doing the second eyepiece to ensure that the effort did not move the focuser for the first eyepiece.

 

Hope this helps someone today, or someday.

 

 

 


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#2 Eddgie

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Posted 02 August 2019 - 12:53 PM

And a refinement.  

 

If you find this useful, but you do go back and forth to other eyepieces, you can parfocalize the two zooms.  

Parfocalizing means that once you put the rings in the right place, to use the zooms, you only need tighten down the diopters and put in the zooms.  Once you have them set for the difference in focus distance, the side they go in does not matter, and the procedure to adjust for the difference is eliminated.

 

For this though, you will want space the zooms a couple of millimeters down from the top on each eyepiece.  Most of the time, the difference in focus potion is going going to be a millimeter or two, and the rings will be two wide to let you get the tiny difference between the left and right eyepiece. If you put one on each eyepiece a couple of millimeters from the top, this should get you the ability to make very small and precise differences of the 1mm or 2mm that is typical of the difference you would likely find between our diopter settings. 

 

This does consume a few millimeters of light path though but that is usually available and a small price to pay to eliminate the adjustment procedure in the future.

 

I really only use zooms in my binoviewer, so once I set the focus difference, I have not had to touch it again, and if you use only zooms, this would be the case for you as well. 


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