WO Mk4 Flattener mini review

[philj]

After searching for reviews on the net re the WO Mk4 flattener I found next to none, so I am breaking new ground here

After using the Meade 127 ED Triplet for a few weeks imaging I found the coma at the extreme edges was evident but not bad, compared to some it aint bad at all but it is still there. I experimented with a Mk 11 flattener which I use on the ZS80 to good effect. However the MK11 was not really designed with a 950mm focal length in mind and coma was still evident.

So I decided to take a leap of faith and invest in a Mk4 Flattener. I understand this was originally intended to be a reducer / flattener but it has now been redesigned to be a flattener only. Because I use the 127 for the image scale, not wide field I wasnt bothered about the reducing side so this was be fine for my needs.

The Mk4 is a big beastie compared to the Mk11, see comparison photo. The lens is bigger and it has a helical focus type device for shifting the lens to get the correct back focus for different camera / scope combos. The helical adjuster is smooth, easy to operate and what’s more important it stays where you put it; this last point is very important as there is no way of locking the setting once you achieved your setting.

I used last nights clear skies to test the new acquisition on the 127 with my Canon 1000D.

The Mk4 comes with 2” nosepiece but does require a T mount for your camera at the other end. I fitted my EOS adapter and slotted the array into the scope.

Focus, phew, that was lucky, I could reach focus on the 127 with just 5mm focus left on the draw tube before it hit the focuser body. Shifting the back focus ring helped a little but only by a few mm.

I experimented with short exposures at different back focus settings using the camera preview screen to check the extremities and I could detect no coma to speak of. Finally I settled on 2 14 minute subs of M31 because I had a similar shot from a previous night at F7.5 that I could use as comparison.

The attached crops are from these images. The crops are from the extreme left hand top corner of the fov and clearly show that the MK4 is doing its job.

I hope to add a bit more to this review as and when I can get to try it on my 102ED and ZS80 FD but so far the flattener is doing exactly what it says on the tin, flattening and I am well pleased with it.

Philj

PS please ignore the plane and sat trails

[steppenwolf]

Thanks for the review, I have the Mk III which does a fair job but is by no means perfect! It looks like a huge chunk of optics!