AO parfocal camera tubes, formerly on ebay.

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AO parfocal camera tubes, formerly on ebay.

#1 Post by apochronaut » Tue Nov 12, 2019 1:24 pm

Some of you may have contemplated purchasing or have purchased one of the AO parfocal tubes that have been selling on ebay for many years. They have been made and sold for/by first one seller, then a different one. It is the same seller. He just thought a name change was due. I purchased several of these some time ago, so I would have an extra for a camera set up when needed but just received them and put them into storage. The concept seems simple enough ; an aluminum tube of precise measurements turned in a lathe. How could that be screwed up? Well, despite the knockoff tubes being made very well , the designer did not follow the original pattern exactly. Everything works as intended but the interior diameter is too narrow. It doesn't cause vignetting but it does allow incoming rays to strike the interior walls at an oblique enough angle that they reflect up the tube inducing flare into the system. The maker has blackened the interior walls with flat black paint in an effort to reduce flare but the reflection still takes place. In a side by side comparison using the same set up only switching the knockoff tube with an original AO tube, there is a significant loss of contrast with the knockoff tube and a hotspot too boot.

I discussed this with the seller and there was a considerable amount of resistance to my assessment of his product. ....hundreds sold, no other complaints, return customers etc. etc. but after sending the comparison pictures, I notice the listing has been pulled. My guess is that he has decided to effect a modification to the design.

Since I had purchased my examples some time ago I was not asking for any compensation and I set about rectifying the problem with the tubes I had. My solution was to install flocking at a critical point in the tube. It doesn't need to be all the way up, just covering about a cm. of the entrance. In fact, if the flocking is farther up the tube, it better be very thin because it will cause vignetting, the tube is that on the edge for diameter.

Another better solution is to access a lathe and turn the hole in the middle about 1/4" larger. Putting flocking at the entrance and blackening the interior is always a good thing too.

The C-Mount tubes are still being listed. My assessment doesn't cover these because I have never had one in my hands. Presumably, they have been sussed and are good to go.

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Re: AO parfocal camera tubes, formerly on ebay.

#2 Post by mnmyco » Tue Nov 12, 2019 6:59 pm

Good to know. I was going to buy one soon.

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