ZWO 485MC Backfocus

[mikemabel]

Sorry it's another Backfocus question but just for my sanity can someone confirm the length of spacers I require to achieve a flat field with this setup

WO S73 scope with matching 0.8x reducer flattener and this camera.

The Backfocus of the flattener is 56.8mm and the 485mc requires 17.5mm of Backfocus. The flattener is adjustable. On the website WO state a DSLR requires 1.8mm dialled in to bring it to the optimum distance

Thank you 😊

 

 

 

[fozzybear]

15 minutes ago, mikemabel said:

Sorry it's another Backfocus question but just for my sanity can someone confirm the length of spacers I require to achieve a flat field with this setup

WO S73 scope with matching 0.8x reducer flattener and this camera.

The Backfocus of the flattener is 56.8mm and the 485mc requires 17.5mm of Backfocus. The flattener is adjustable. On the website WO state a DSLR requires 1.8mm dialled in to bring it to the optimum distance

Thank you 😊

 

 

 

So to achieve the optimum of 56.8mm you camera has 17.5mm off "back focus length" thus 56.8-17.5=39.3mm to add to the back of the flattener less filter wheel or any other items after the flattener

or remove the 2" adaptor on the camera then the "back focus length" would be 6.5mm to the flange on camera body M42x0.75 so again 56.8-6.5=50.3mm of spacing to add between the flattener and camera 

hope this makes sense  

[mikemabel]

29 minutes ago, fozzybear said:

So to achieve the optimum of 56.8mm you camera has 17.5mm off "back focus length" thus 56.8-17.5=39.3mm to add to the back of the flattener less filter wheel or any other items after the flattener

or remove the 2" adaptor on the camera then the "back focus length" would be 6.5mm to the flange on camera body M42x0.75 so again 56.8-6.5=50.3mm of spacing to add between the flattener and camera 

hope this makes sense  

Thank you Fozzybear for that explanation. To get that 39.3 I will add spacers up to 39 or 38 then screw out the flattener to add the rest. As far as I can see the 2" nosepiece does not come off.

Clear skies 

Mike

[fozzybear]

Mike,

I do not own that camera but as per the photo it does suggest that the 2" adaptor is removeable if needed hope you get it sorted out. then you would only need a 50mm barrel extension M42x0.75 as opposed to multiple ones screwed together.

I do have a ZWO camera not the same as you and mine had a nose piece but this also took off the front flange from camera in red as well but a pair of marigolds took care of that 

Regards

Andy 

[mikemabel]

Cheers Andy 

I did try to take the nosepiece off but the whole cover tried to come off so I quickly put it back and forgot about it !

Unfortunately the WO flattener has a M48 thread so I still need an M48 to M42 somewhere in the setup.

I've set it up as best I can and will take some test exposures to fine tune it.

Cheers

Mike

 

 

[fozzybear]

3 minutes ago, mikemabel said:

I did try to take the nosepiece off but the whole cover tried to come off so I quickly put it back and forgot about it !

Same happened to me nearly cried but if you need the space i.e. MM then it has to come off. Let's hope you don't need to but all is safe if you have to just do it in a clean area no wind to get dust on the sensor... And as i said a pair of marigolds works a treat it not remove with the camera bit in red and put in some warm water for a couple of minutes to free up the threads then unscrew (not the camera assy as would be bad) 

[Ags]

The 2" part comes off the 485MC exposung male T2 thread, at least it does on mine.

Edited December 28, 2021 by Ags

[mikemabel]

Cheers ags.

I'm a bit ham fisted when it comes to taking things apart so I'll just leave it .

It will only end in tears.

Thanks 

Mike