Focal reducer flattener for 80ED

[avandonk]

Here are some pictures taken with 80ED and 5D with and without a 42mm dia FL 325mm binocular objective as as focal reducer flattener. The lens was 75 mm in front of the focal plane of the camera. Curved side towards 80ED objective. The reduction works out to be a factor of 0.78 and the field was also much flatter although some vignetting was present due to the lens only having a usable aperture of 40mm. It looks like it is well worthwhile using focal reducers flatteners with the 80ED.
pic1 80ED ie 600mm @ F7.5 FOV 3.44X2.29 deg
pic2 80ED with FRed. 468mm @ F5.85 FOV 4.41X2.94 deg
pic3 Both pics stacked with Registar
A 50mm dia lens of 325mm FL should show no vignetting.
I have a reducer on order from Hutech which should have no vignetting.
For 20D etc sized sensors a 40mm diameter lens works very well.

Bert

[avandonk]

I received a 2'' barrel to Canon EOS adapter from ScopeStuff. Here are a few pics of a 320mm FL lens mounted inside. The clear aperture is 42mm.
Makes a very convenient focal reducer/field flattener for the 80ED.

Bert

[Striker]

Nice bert.....how much ??????

My calcualtions make it a F4 at that focal length...very nice

Can you supply them for the group.

[avandonk]

Hi Striker
I have only got two 320mm FL 42mm diam lenses at the moment so I can make two for the cost of the ScopeStuff adapter for anyone who is interested. I will see if if I can obtain more lenses that would be suitable.
With the lens placed where it is the focal reduction is about 0.8.
So the 80ED would behave as a 468mm @ F5.85 . The main thing is the field is flat.
I do have some 42mm diam with shorter focal lengths (150mm) but they would result in more focal reduction (about 0.66) which could lead to aberrations.
I have yet to test them with the SS adapter. I also have more adapters on the way.
I can post you one to try it out.

Bert

[Striker]

I'm interested...let me know how much at mates rates....lol

[avandonk]

I will send you the unit and all I ask is either replace the SS adapter or send equivalent money. The trial is free as I am not in business just a slightly crazy keen amateur who likes to dabble. If not happy just return it. I think that all the focal reducers on the market are just achromatic doublets. It is only when you pay big dollars for the triplet and in the case of Hutech two variable air spaced doublets that they really shine for field flattening.

Bert

[h0ughy]

Bert how much did yours cost to make for say a 300D?

[Striker]

Hey back off Houghy.....I'm first inline....keep your hands of my FR....lol

[Roger Davis]

Old binocular objectives? Easy pickin's for those of us with drawers of 40 and 50mm binocular objectives. Glad they came in handy Bert.
Nice to see that it works so well.

[h0ughy]

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