Where do I buy an occulting bar?

[michaelmorris]

I've read about the use of an occulting bar in many articles on double star observing. I realise that many people make their own devices to produce an occulting bar. However, to be frank most of the ones I've seen look like a lot of hassle and seem to involve either taking eyepieces apart or sticking things on to the eyepiece glass. I'm not keen on risking any of my eyepieces!

Does anyone make either:

eyepieces with a bulit in occulting bar?

or:

Something that just screws in to the filter thread at the end of the eyepiece?

[Merlin66]

I've never seen a commercial occulting bar eyepiece. Over the years I've made a few. Getting something to screw on the end like a filter really depends on making an internal reverse "nosepiece" which can position the bar, only needs to be 1-2mm wide, correctly in the focal plane of the eyepiece.

All you really need to do is Blu-tac a small length of 5 thou thick shim x 1-2mm wide across the middle of the aperture stop in the front of the eyepiece. This generally does the job.

[Andrew*]

An occulting bar needs to be at the focal point of the eyepiece, so it will be different for each eyepiece, therefore a screw-on bar won't work. And any eyepieces where the focal point is between the elements will involve taking it apart and working out where it goes. Hmm... rather not! :?

I think orthos work well because they have a field stop ring at the focal point so you know where to put teh bar. Then you just "focus" it by looking through the eypiece and prodding it with a pencil till it's sharp. No taking apart and no glass contact!

Andrew

[jabeoo1]

You can also use a violet filter.  Remove it from its cell,  score it with a glass cutter & straight edge, break it in half.  Rub the edges with an emery board to eliminate burrs.  Epoxy the 2 semicircles segments to the inside of the field stop of your carefully chosen eyepiece.  You need to make sure the EP you use does not have its focal plane between the internal glass surfaces (so plossl, ortho kellner are the ones to use).  Although I could not see myself doing this to my 26mm Nag in a hurry ! 

[jabeoo1]

Does anyone use an occulting EP hunting minor moons or tricky glared out doubles like Sirius B ? 

[John]

I added a DIY occulting bar to a 6mm orthoscopic eyepiece with the aim of helping to see Sirius B. It was an interesting experiment bit it did not work for me with the scope I had at the time - a 6" F/6 refractor. The split has now widened a little and I've been able to spot Sirus B with my 12" dob without the need of the bar.

I can see that the occulting bar approach could work but adding the occulting bar also adds a little further diffraction to the view I feel, which does not help with these "on the edge" type targets.

This is a positively vintage thread !

[jabeoo1]

This is a positively vintage thread !

Thanks for sharing your personal experience of using this technique John.  

I noticed the age of this thread & was a bit surprised to be honest ! 

Will be interesting to see if any other forum users try this method.  I am really glad you managed Sirius B.  I may have to try it in the 10 inch now.  

[John]

I would definitely try for it. I find a 6mm orthoscopic eyepiece works the best for it.

[FenlandPaul]

Not really my field, but I did notice a link to this on p33 of this month's Sky & Telescope; the article was about observing some of the minor moons in the solar system:

http://www.skyandtelescope.com/observing/the-martian-moons-in-200708/

Paul

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[michael8554]

I once had a drink in an Occulting Bar in Haiti.....

[ghostdance]

I once had a drink in an Occulting Bar in Haiti.....

I once had a seance in one...

Think it was Bal-ham tho, 'Gateway to the South'. Happy days.