ZWO ASI1600MM Spacers Question !

[Astro Buer]

Hi all,

I'm looking at getting a ZWO ASI1600mm to couple with my William Optics ZS61 scope. I have done my research, on SGL, Cloudy Nights, I've even read the manual but have still yet to find an answer to my question; what spacers do I need to achieve the correct back focus distance for the WO ZS61 using the Flat 61 field flattener in conjunction with a filter wheel and the ZWO ASI1600mm?

Looking the manual, the spacers are thus: 

2" Filter (optional) - M42-1.25 Extender 18.45 - T2 Extender 11mm - T2-T2 adaptor - EFW Mini - ZWO ASI1600mm

So, do I need the Flat 61 for use with the ZWO camera?  

Or should this be:

WO ZS61 - Flat 61 - M42-1.25 Extender 18.45 - T2 Extender 11mm - T2-T2 adaptor - EFW Mini - ZWO ASI1600mm

Sorry if this is a stupid question... I'm sure the answer to this will either be 'yes' or 'no'... either way I'll sleep better tonight.

Thanks in advance SGL. 

 

[symmetal]

Hi Astro Buer. I've recently bought a ZS61, Flat-61 field flattener and ASI1600MM bundle which includes EFWMini and 31mm unmounted filters.

Using the above diagram you need 54.8mm from the rear of the flattener to the image sensor.

Using this diagram from the ASI1600 manual (all these spacers are included with the ASI1600 , (not the OAG & Canon/Nikon T2 adapters)) which is a little different from your diagram, behind the field flattener you need (12) M42-M48 16.5mm extender, (5) T2 extender 11mm, (15) M42-M42 male adapter, 2mm, (7) EFWMini Filter Wheel, 20mm.

This adds up to 49.5mm which added to the 6.5mm sensor distance in the camera comes to 56.0mm.

The 54.8mm from the top image doesn't include the filters so you need to add 1/3 the thickness of the 2mm thick filters to this value which gives 55.5mm.

The spacing from the bottom image seems to be 0.5mm too much but I went with this for the first test.

Unfortunately, I've had so much cloud here for the past month I've only had a few hours imaging time to check this among other things I was doing. There was slight star elongation pointing towards the centre in the extreme corners of the image. CCD Inspector confirmed this. I've just received a 10mm T2 spacer to try in place of the 11mm ZWO spacer along with some delrin spacers but haven't had the chance to try it out yet to confirm the exact spacing required.

I hope this helps you with your decision. 

Alan

[Astro Buer]

50 minutes ago, symmetal said:

Hi Astro Buer. I've recently bought a ZS61, Flat-61 field flattener and ASI1600MM bundle which includes EFWMini and 31mm unmounted filters.

Using the above diagram you need 54.8mm from the rear of the flattener to the image sensor.

Using this diagram from the ASI1600 manual (all these spacers are included with the ASI1600 , (not the OAG & Canon/Nikon T2 adapters)) which is a little different from your diagram, behind the field flattener you need (12) M42-M48 16.5mm extender, (5) T2 extender 11mm, (15) M42-M42 male adapter, 2mm, (7) EFWMini Filter Wheel, 20mm.

This adds up to 49.5mm which added to the 6.5mm sensor distance in the camera comes to 56.0mm.

The 54.8mm from the top image doesn't include the filters so you need to add 1/3 the thickness of the 2mm thick filters to this value which gives 55.5mm.

The spacing from the bottom image seems to be 0.5mm too much but I went with this for the first test.

Unfortunately, I've had so much cloud here for the past month I've only had a few hours imaging time to check this among other things I was doing. There was slight star elongation pointing towards the centre in the extreme corners of the image. CCD Inspector confirmed this. I've just received a 10mm T2 spacer to try in place of the 11mm ZWO spacer along with some delrin spacers but haven't had the chance to try it out yet to confirm the exact spacing required.

I hope this helps you with your decision. 

Alan

Thank you so much, Alan.

This makes perfect sense now. I struggle with the mathematical side of things now and then (I know, get a calculator!) yet your post just made the light bulb in my head go 'click!' 

Thank you so much for your simple explanation. I'd be keen to know how you get on (willing clear skies your way!!) but this gives me so much confidence to press the button on this little camera. The pixel size/focal length seems like a really good match for the WO ZS61  making it a very exciting prospect. 

Thanks again ! 

[symmetal]

Glad it helped Astro Buer. Yes, the wide FOV at 2.2"/pixel looks very promising. You can get all of the Andromeda galaxy nicely in the frame. I've mounted it next to my FLT-98 with my Mini PC and controllers in the box on the other side. I did have an ST80 guide scope but swapped it for the ZWO 60mm guider scope to keep the overall weight down.

I bought the gold ZS61 to match the FLT-98 but it's a different shade of gold.  

Alan

[Astro Buer]

9 hours ago, symmetal said:

Glad it helped Astro Buer. Yes, the wide FOV at 2.2"/pixel looks very promising. You can get all of the Andromeda galaxy nicely in the frame. I've mounted it next to my FLT-98 with my Mini PC and controllers in the box on the other side. I did have an ST80 guide scope but swapped it for the ZWO 60mm guider scope to keep the overall weight down.

I bought the gold ZS61 to match the FLT-98 but it's a different shade of gold.  

Alan

That's a thing of beauty, Alan!