William Optics Flat 61A Flattener

[Radders]

I have a William Optics Z61 with the Flat 61A adjustable Flattener. I took an image of the Horsehead Nebula and noticed there was a bit of coma in the corners. I have it set to 12.9mm as instructed on the WO website. I am using a Canon 6d with it. Would the 12.9mm be correct or will it be more or less? 

[teoria_del_big_bang]

I am a little confused because yes everywhere I look at the Flat61A is says adjust to 12.9 mm but there is a back-focus drawing that sort of says 18.10 mm.

I am assuming this is an old drawing and is for the original flattener that was not adjustable. You cannot be over 5 mm out otherwise there would be more than a bit of coma.

Have you got a filter in the flattener ?

If so then on the adjustable flattener the filter is the camera side and so needs to be accounted for by adding 1/3 thickness of the filter. Depends on your filter but they are normally around 3mm so you could be 1 mm out.

Steve

[Radders]

Hi yes, I have a Svbony CLS filter in. So adjust to 13.9mm? 

[david_taurus83]

It probably doesnt correct for a full frame sensor. Theres also this diagram on their website that shows 12.7mm (+55mm) from the back shoulder.

[Radders]

I thought it did. I'm sure I read that it does. 

[teoria_del_big_bang]

I think the canon T mount thickness should be 11mm which combined with the 44mm distance from sensor to camera mounting face makes up the 55 mm. But worth checking the t Mount you have is actually 11mm.

 

Steve

[Radders]

Them drawings make no sense to me. So if the Canon t mount is 11 mm, should the Flattener be set to 12.9mm or 13.9mm with the filter in? 

[david_taurus83]

You need to experiment. No other way around it. Though a corrected image circle of around 40mm is needed for the 6D so you might be trying to find results not possible with this scope and flattener.

[PEMS]

If the information I have is right the Canon 6D has a distance of 44mm to the sensor. So you need an additional 11mm, approximately. EF lens on a full frame Canon DSLR all I can see is 44mm. My information is not by camera but by lens type or fitting.

The Flat61A has an adjustment of 0 to 15mm according to the WO site. So if the T-mount adds 11mm as given previously the Flat 61A should it seems need to be set at 0mm. As you would have 55 from 44mm in the 6D and 11mm from the t-mount. So 55mm with the 2 items already so the Flat61A needs to add 0mm.

The glass filter may add 1mm, approximatelt 1/3 of the filter thickness. Which I presume from previous is 3mm thick.

You need the mechanical data of the 6D to come to a better or accurate answer.

Edited December 28, 2019 by PEMS

[KEJ]

Hi

I hope you don't mind me asking, but did you get to the bottom of this ?

Could I please ask for some technical assistance on a small issue I have with my William Optics Z61 scope + 61A Flattener.

 

Basically, I have now added Nikon M48 T adapter to my setup so that I can take some astrophotography pictures by attaching a camera.

So I have the following configuration:

                      Camera – M48 adapter – 61A Flattener – Z61 scope

 I believe I have correctly adjusted the flattener using the calculation for a Nikon :

69.2 - 54.8 = 14.40 setting for the WO flattener. based on M52

Or

67.7 - 54.8 = 12.9  setting for the WO flattener.  based on M48

 

So in the end looking at the diagram assumed I required to set it at 12.9 based on my adapter.

 

I am also assuming this is the same distance for both a DX(cropped sensor ) and FF(Full Frame sensor) Nikon cameras(DSLR).

 

The very odd thing is for my DX camera(cropped D3300) the picture seems fine, but for the FF camera (D800) the picture is very dark.

 

Ok so you assume it’s the ISO or shutter speed and I am on Manual, but I have adjusted the ISO up and down, same with the shutter speeds up and down etc.

 

I am starting to wonder is the Z61 + A61 really designed just for cropped(DX) cameras or do you think I have done something wrong, then of course I came across this and now as you suggested should I be closed setting it to Zero ?

 

I hope all that makes sense and I look forward to your reply.

Hopefully thanks in advance

 

[PEMS]

Which Nikon? The F mount has a flange distance of 46.5mm, the S mount has 34.85mm, the I mount has 17mm and the Z mount has 16mm. So 4 options and all different .

Going to assume that it is an F mount and is therefore 46.5. You need to supply the Nikon camera type or name or whatever, D5n00 usually,

To get to 55 you need another 8.5mm, which is not a lot. Need to know the thickness added by the M48 adaptor. If that is greater then 8.5mm then you cannot get the camera sensor at the correct position of 55mm from the appropriate face of the flattener., since camera body and M38 adaptor already exceed 55mm.

If the M48 adaptor adds less then 8.5mm then subtract the M48 thickness from 8.5mm and set the flattener to that value. So if it adds say 6mm you set the flattener to 8.5-6 = 2.5mm.

If the M48 adaptor is greater then 8.5mm and you are having problems that i likely the reason.

If you have one of the newer mirrorless cameras then  I would expect you need a selection of spacers to move the camera sensor back sufficently.

Really need the camera model and the M48 thickness that it adds.

Edited May 14, 2020 by PEMS

[KEJ]

Further play.

12.9 seems the best for me.

Comments welcome.

 

Cheers

[KEJ]

Pems hi

 

Thank you for replying.

Sorry, just took some test shots and added my last comment then saw your reply..............but dinner was on the table(Boss was calling).

I did mention above, but it was a drawn out question.............I have a Nikon D3300 (cropped DX) and a Nikon D800 (FF).

 

Adapter

Nikon M48 T-Adapter - say just over 1 cm,. However, I would say approx 6mm screws onto/over the Flattener, meaning there is possibly about a 4mm gap.

Without taking it to bits(all setup ready for tonight) it could be less or more.

I will try your suggestion tomorrow - thank you.

 

Dark Picture

Picture dimming was my fault(D800), school boy error, the  LCD/LED display not that bright on reviewing pictures(after), but very bright on preview(before), when viewed on Computer straight from SD card after all fine.

Just back to the settings.......I did try 14.40(M52), then 12.90(M48) and even 0.

12.9 appeared to give me the sharper corners, I haven't tried any other settings yet

Thanks

 

 

Edited May 14, 2020 by KEJ

[KEJ]

Tim at William Optics(Taiwan) replied to an email of mine.

For a Nikon DSLR the gap should be 12.9mm

 

If you use DSLR, the setting for your flattener should be 12.9mm.

Setup: ZS61 + Flat61a + t mount + DSLR (settings 12.9mm).

Edited May 19, 2020 by KEJ