William Optics Flat6A III Focus issues.

[peonic]

HELP!

I have a William Optics FLT91 which I've been using with both a 533 mono and 533 OSC for a few months now with no issue.

Last night I tried to add the adjustable Flat6A III flattener/reducer into the mix, and I just can't get focus.  With the focuser racked FULLY in, I can see out of focus stars, but there's no more inward travel to acheive focus.

On my ED80 with the matched SkyWatcher flattener, the focus position is pretty close to the non-reduced focal point.

With the WO scope, "normal" focus position is with the focuser racked out half way. I only start to see out of focus stars with it very close to fully racked in (using a ZWO EAF, un-reduced I achieve focus around 17500 steps, to see out of focus stars start to appear at all I have to wind the focuser right in to 3000 steps).

 

This feels terminal to me? Mismatch between the 533's tiny sensor, maybe?

 

Chris

[Gary Clayton]

Is this the version you have?, it does not mention your scope https://www.firstlightoptics.com/reducersflatteners/william-optics-adjustable-flat6a-iii-08x-reducer-flattener.html

[peonic]

Hey Gary,

 

Yes and no - there's a version with an optional adapter for the FLT-91 - https://www.firstlightoptics.com/reducersflatteners/william-optics-adjustable-flat6a-iii-08x-reducer-flattener-for-flt91.html - but other than the adapter it's the same reducer.

 

Chris

[StevieDvd]

Per the ASI533 specs at ZWO  it needs a 55mm spacing (that's 17.5mm for the camera and the 2 spacers 16.5mm & 21mm)  for narmal usage. Just like a dslr.

If you look at the widescreen page for the dedicated Flat6A III for FLT91 the second diagram (right-click on it to view in new tab to see it larger) it shows the spacing needed with the extension tube removed.

HTH

Steve

 

 

 

 

[Gary Clayton]

30 minutes ago, peonic said:

Hey Gary,

 

Yes and no - there's a version with an optional adapter for the FLT-91 - https://www.firstlightoptics.com/reducersflatteners/william-optics-adjustable-flat6a-iii-08x-reducer-flattener-for-flt91.html - but other than the adapter it's the same reducer.

 

Chris

I would hazard a guess then that it's just a backfocus issue

[david_taurus83]

A picture of how you have attached the flattener would help.

[peonic]

Not at home right now so a picture will have wait a couple of hours but....

Scope - M68 adapter - flattener - 16.5 extension - 11mm extension - 8 position 1.25mm filter wheel - 533mm pro.

The 11mm ring was removed from the nose of the camera as per the ZWO docs, at the flattener set for 5.4mm

 

Chris

 

 

 

 

 

 

 

[peonic]

3 hours ago, StevieDvd said:

Per the ASI533 specs at ZWO  it needs a 55mm spacing (that's 17.5mm for the camera and the 2 spacers 16.5mm & 21mm)  for narmal usage. Just like a dslr.

If you look at the widescreen page for the dedicated Flat6A III for FLT91 the second diagram (right-click on it to view in new tab to see it larger) it shows the spacing needed with the extension tube removed.

HTH

Steve

 

 

 

 

Steve you legend!

I was just removing the click lock adapter from the end of the extension tube, not the whole tube itself!

I didn't even realise it WAS removable to be honest.

 

Pretty much sure that this will fix it - thanks so much!

 

Chris

[Adam J]

On 22/01/2023 at 12:37, peonic said:

HELP!

I have a William Optics FLT91 which I've been using with both a 533 mono and 533 OSC for a few months now with no issue.

Last night I tried to add the adjustable Flat6A III flattener/reducer into the mix, and I just can't get focus.  With the focuser racked FULLY in, I can see out of focus stars, but there's no more inward travel to acheive focus.

On my ED80 with the matched SkyWatcher flattener, the focus position is pretty close to the non-reduced focal point.

With the WO scope, "normal" focus position is with the focuser racked out half way. I only start to see out of focus stars with it very close to fully racked in (using a ZWO EAF, un-reduced I achieve focus around 17500 steps, to see out of focus stars start to appear at all I have to wind the focuser right in to 3000 steps).

 

This feels terminal to me? Mismatch between the 533's tiny sensor, maybe?

 

Chris

and whats the Flat6A adjusted to?

Edit seems you fixed it.

Adam

Edited January 27, 2023 by Adam J