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Low Profile EOS-T adaptor with focus confirmation...


Psychobilly
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I'm not 100% happy with the Field flatness from the Megrez72 and FFIII combo and possibly needed to reduce the Sensor to flattener distance...

Well comercially available T adaptors for a given Lens mount are all the same thickness and in the case of the EOS one this is 10.7mm...

So I decide to tackle the problem and make my own out of a few "off the shelf" components that I had in the "adaptors box" and a few minutes on the trusty Myford...

The two components used were A EOS-M42 (Standard M42x1.0) Focus Confirmation Adaptor (The ones with the chip and contacts fitted) and a 7mm T extension...

The Male M42x0.75 Thread on the back of the 7mm T adaptor was reduced so that only 2 complete turns of thread remained...

The front of the EOS-M42 adaptor was counter-bored to the OD of the 7mm T adaptor leaving only 2 turns of the M42x1.0 thread in the adaptor...

Although not ideal, over this shortened thread the two mismatched threads could be gently pesuaded to work together until the shoulders of the adaptors were mated together...

The result as it stands is an adaptor thats 4.2mm shorter than a standard one... and can be reduced further by machining back the front face....

Or if it is to short I can add spacers whilst checking the flatness and star shapes using the 30 day trial version of CCDInspector...

Peter...

Edited by Psychobilly
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Just machined a pair 1.50mm and 2.00mm thick T threaded spacers as well out of the insert of an old T adaptor I had lying around...

All I need now is the clouds to co-operate :)

Might have to get the Milling machine running tomorrow as I want to make an adjustable focuser draw tube support that mounts of the guide rail to dail out any "droop" ...

Peter...

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Looks like another night when I wont get to try it ... milky skies again can just about make out the disc of the sun through them at the moment i bet my 30 day trial of CCDInspector runs out before I get the spacing dialled in :)

Edited by Psychobilly
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I got some daylight testing done on white dot targets and was able to get the Corner distortion to go from Sagittal to Tangential by working up from the Low-profile to standard adaptor spacing...

The dots were round in the corners with the LP adaptor +0.2mm which is 4.0mm shorter than the standard T adaptor...I am hoping to get a star test done tonight... either that or I need to print a load more dot targets to fill the whole FOV...although this time I will use black dots and invert the camera image in CS before analysis...

Peter...

Edited by Psychobilly
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