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Legend M 10x42 - quick test (1 Viewer)

Henry,

I recall the post. I should have asked at the time if the scope had a dedicated SLR mount or some other coupling mechanism?

David

I use a simple prime focus adapter. It's just a 2" tube that slides into the scope focuser with male T threads at the back end to accept the camera.

Sounds like your camera would be much better for this. I don't know how to do anything about my camera's output or internal settings. All I can do is shoot RAW images and compare them to the what I see at the examination scope's eyepiece.

Henry
 
Tanks Henry,

I hadn't thought of a draw tube type arrangement. I do have extension tubes for the industrial camera that might be made to work with one scope objective, and a second one that could work as the collimator. I really like to get the components rail mounted if I can. It would make life so much easier.

It's not unusual for cameras to have an options for remote control and viewing. Might be worth looking into?

David
 
Thanks David,

I couldn't persuade Google to take me beyond page 90, but I have seen illustrations like that before. I've tried using one of my astronomical refractors as a collimating lens with a backlit USAF glass slide placed at the end of the focusing tube. It works fine with the binocular under test (focused at infinity) easily reaching focus on the chart at less than a meter from the telescope objective. Of course, it's still necessary to use an examination scope behind the binocular eyepiece to see the full resolution. Problem is I don't know how to derive arc second resolution from the resolvable LPs/mm on the chart when it's used that way, so I haven't pursued it. I'm sure you are right that they must be using a set-up with a collimating lens and presumably an auxiliary scope.

Henry

Hi Henry, been awhile.

The math for the distance for using a collimating lens is the same as for regular distance to a paper target but using the focal length of the collimating lens. The atan (reciprocal of the lines per mm divided by the distance in meters).

I have attached the ISO page for a resolution collimator and a picture of the one I built that has a 400 mm objective.

I have used a five inch +/- 450 mm lens but it is in the open and not lighted per spec and does not yield good results. You might try a good backlight with a frosted glass diffuser in a dark room and see how close you get.

Lighting is very critical. My home built collimator has a frosted glass diffuser and I use a collimated light source as the ISO diagram shows and get very good results but I can take the glass diffuser out and use an integrating sphere, which gives an almost perfect diffuse light source (also expensive) and get a measurable improvement in my readings. Don’t recommend spending the money for the sphere, all you really want is reproducible results.

Setting the USAF target at the focal point of the collimating lens is critical to accuracy, in your case I would recommend using the K&E double collimator since, unless way out of adjustment, both sides are infinity focus, you can verify that by looking at distant objects outside and comparing one side to the other. Also the grid at the focal point has a 5 minute apparent angle, a rough check against your USAF target.

I have attached a spreadsheet for simple conversion for you. Change the focal length or distance to target in column B, change the resolved group in column C. As a check column G should be the same lines per mm as your standard USAF target.

Let me know of any other questions.

Ron
 

Attachments

  • Collimator.jpg
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  • DSCN0617.jpg
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  • ISO Collimator.jpg
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  • P2010009.jpg
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  • USAF Group Resolution Collimator.xls
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Hi Ron,

Thanks for the tips. I've downloaded the spreadsheet and the ISO page. What can we do to coax you into bringing your trove of knowledge here more often?

Henry
 
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