question about William optics adjustable Flat 73A for WO Z73 - Forums

Topic starter

Aug 11, 2019

hi all, i am having a bit of trouble finding an answer to this question. i have the wo z73 as well as the adjustable flattener for it. it says in the specs that the back adjust for the flattener is 11.4mm. My question is that is that measurement for the scope, or for dslr?.. since i am using a zwo 183mm.. i am unsure where to place the adjustment on the flattener.. i know the camera requires 55mm and i can cover that i just cannot find any info for the flattener part. any help would be greatly appreciated.

Robert Q. Kimball

Nov 19, 2019

I don't have the a specific answer, but I do have experience with a W.O. FLT 110 and W.O. AFR IV flattener. On the flattener, there are numbers from 68 to 88 (i think, my scope is up at an observatory. The distance from the back if the flattener to the sensor + the value on the flattener needs to add up to 123.5 mm. I suggest you contact W.O. and see if there is an Iideal distance for your flattener.

Bob

Chris

Nov 24, 2019 · Edited: Nov 24, 2019

I have the z73 also but using it with a ZWO asi178mmcamera. This is the arrangement that I used:

ZWO ASI 178 Back Focus

The "filter" listed in the diagram is the zwo filter wheel, but a spacer replace it. I've had good results with this setup. I am not sure if the asi 183 sensor spacing to the body is the same.

Cheers,

Chris

Concise

Juan Pablo

Jul 4, 2020

Richard O:
hi all, i am having a bit of trouble finding an answer to this question. i have the wo z73 as well as the adjustable flattener for it. it says in the specs that the back adjust for the flattener is 11.4mm. My question is that is that measurement for the scope, or for dslr?.. since i am using a zwo 183mm.. i am unsure where to place the adjustment on the flattener.. i know the camera requires 55mm and i can cover that i just cannot find any info for the flattener part. any help would be greatly appreciated.

Hi Richard,
I have your same setup, but I can't find the correct configuration, can you help me?,

cheers.

J

matthew.maclean

Jul 5, 2020

Hi Richard,

if you go onto to the WO website for your flattener, they have a little BackFocus schematic under the “MoreInformation” tab. Looks like your camera plane needs to be (Dimension.A) 66.2mm from the back edge when it’s at zero. So the 11mm value they quote would be for a DSLR; with an Astro Camera, you just need to accumulate that total distance using the flattener, extension spacers, filter wheel, camera flange, etc.

if you are using filters, the glass affects the spacing slightly. Usually you have to add something around 0.7mm or so (depends on the manufacturer).

Helpful Respectful Concise Supportive

Richard O

Topic starter

Jul 5, 2020

hi all thanks for the replies… i am currently still looking for the best adjustment for this but since i have started a new job that requires me to travel every 3 months and finding clear days when i can, it has been rather difficult to get time under the sky. I will keep working on this though and see what i can come up with. but starting point of 11.4mm on the flattener was a good starting point.

Jonathan Aranow

Jul 13, 2020

I had to sort out a similar issue with my WO z103 and asi1600 and filter. I emailed WO and got a response in a few hours. You do need to go to zwo site and look up specs for your camera for its back focuslength.

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