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QHY 268 Back Focus?


DaveS
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Been reading about the 268m on CN. There does not appear to be any solid information on the camera connector, and that it wont come with the dovetail like the 268c. Does anyone have any confirmed info and how it could connect to a ZWO EFW 7x 36mm filter? ta!

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I think they took that away to reduce the cameras back-focus requirements and to allow for easier use of an OAG and EFW. Principle is still the same though, you'd use the included spacers, and the M48 adapter which both get bolted to the camera, then you can fit the EFW. Or bolt the M48 adapter straight to the camera and use M48 spacers. 

 

 

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  • 1 month later...
On 24/01/2021 at 09:25, Deeko said:

Been reading about the 268m on CN. There does not appear to be any solid information on the camera connector, and that it wont come with the dovetail like the 268c. Does anyone have any confirmed info and how it could connect to a ZWO EFW 7x 36mm filter? ta!

HI @Deeko - Just wondering if you went ahead with that arrangement and what your results were like. I have a ZWO 7x36mm as well and considering getting a QHY268m. But i am worried about vignetting. Also may i ask how you arranged it all.

 

I may be simpler to just get a new QHY EFW, but if its possible than i rather not.

 

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On 04/03/2021 at 12:08, rsarwar said:

HI @Deeko - Just wondering if you went ahead with that arrangement and what your results were like. I have a ZWO 7x36mm as well and considering getting a QHY268m. But i am worried about vignetting. Also may i ask how you arranged it all.

 

I may be simpler to just get a new QHY EFW, but if its possible than i rather not.

 

Hey, I have posted up some images in this thread: 

However, they were all done under a full moon so not a great test yet! I had some vignetting but I think this may have been caused by the full moonlight and possibly over compensated flats. I need to wait on a clear night with no moon to do some more testing.

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On 05/03/2021 at 20:01, Deeko said:

Hey, I have posted up some images in this thread: 

However, they were all done under a full moon so not a great test yet! I had some vignetting but I think this may have been caused by the full moonlight and possibly over compensated flats. I need to wait on a clear night with no moon to do some more testing.

Brilliant pitctures indeed. 

weather has been really bad lately, but did you manage to take any pictures last night (was moonless) - it was clear between 2300 and 0300 hr for a while where i am, in oxfordshire?

may i ask how you did your spacings with ZWO EFW and how you connected it all?

Thanks

 

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18 hours ago, rsarwar said:

Brilliant pitctures indeed. 

weather has been really bad lately, but did you manage to take any pictures last night (was moonless) - it was clear between 2300 and 0300 hr for a while where i am, in oxfordshire?

may i ask how you did your spacings with ZWO EFW and how you connected it all?

Thanks

 

Hello, unfortunately I didn't get a chance to go out, not sure when that will be next. There are a few photos below on how I connected the camera to the ZWO EFW with 55mm back focus. 

For connecting the 268m to the EFW I used the T2-T2 male adapter that came with the EFW and bought a ZWO M48-M42 ring adaptor (https://www.firstlightoptics.com/zwo-accessories/zwo-m48-to-m42-adapter-ring.html) to screw onto it. This gives one side of the T2-T2 adaptor an m48 thread that I could screw directly onto the camera plate with the  other side screwing onto the EFW.

Before screwing the T2 adaptor with M48 ring onto the camera plate:

 

IMG_20210307_163119.thumb.jpg.b60a267a03d8e0e9119d3c6944728f41.jpg

After screwing in the T2 adaptor with M48 ring, which can then screw into the EFW:

post-317051-0-45804700-1613048029_thumb.jpg.484d0262fa41a1cf8f1f2143c84d520c.jpg

For the Telescope side you will need to source adaptors that work for your setup and the reducer/flattener. For my setup I used a T2 extension and rotator to make up the remaining back focus, the EFW takes up 20mm:

IMG_20210307_163011.thumb.jpg.502edef312b2d542a2c874e5cfad6b49.jpg

 

HTH

Edited by Deeko
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3 hours ago, Deeko said:

Hello, unfortunately I didn't get a chance to go out, not sure when that will be next. There are a few photos below on how I connected the camera to the ZWO EFW with 55mm back focus. 

For connecting the 268m to the EFW I used the T2-T2 male adapter that came with the EFW and bought a ZWO M48-M42 ring adaptor (https://www.firstlightoptics.com/zwo-accessories/zwo-m48-to-m42-adapter-ring.html) to screw onto it. This gives one side of the T2-T2 adaptor an m48 thread that I could screw directly onto the camera plate with the  other side screwing onto the EFW.

Before screwing the T2 adaptor with M48 ring onto the camera plate:

 

IMG_20210307_163119.thumb.jpg.b60a267a03d8e0e9119d3c6944728f41.jpg

After screwing in the T2 adaptor with M48 ring, which can then screw into the EFW:

post-317051-0-45804700-1613048029_thumb.jpg.484d0262fa41a1cf8f1f2143c84d520c.jpg

For the Telescope side you will need to source adaptors that work for your setup and the reducer/flattener. For my setup I used a T2 extension and rotator to make up the remaining back focus, the EFW takes up 20mm:

IMG_20210307_163011.thumb.jpg.502edef312b2d542a2c874e5cfad6b49.jpg

 

HTH

perfect thanks. this fives me confidence that it can be done

could you not have use the M42-M48 to connect the EFW directly onto the M54-M48 adaptor that gets bolted on to the 268M.

Which retailer did you get the camera from - i usually do FLO, but they done seem to do QHY268M. would be nice to get it from within the UK.

Best Regards

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12 hours ago, rsarwar said:

perfect thanks. this fives me confidence that it can be done

could you not have use the M42-M48 to connect the EFW directly onto the M54-M48 adaptor that gets bolted on to the 268M.

Which retailer did you get the camera from - i usually do FLO, but they done seem to do QHY268M. would be nice to get it from within the UK.

Best Regards

Hi Rsarwar, the photo shows exactly that. In the photo the M54-M48 adaptor is bolted onto the camera first, then the T2-T2 adaptor (with the M42-M48 ring) to make it T2-M48, so the M48 side screws into the cameras M54-M48 adaptor and the other T2 end straight into the EFW. I admit it is quite confusing and tool me some time to figure it out until I had the camera and adaptors in my hand.

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15 hours ago, rsarwar said:

perfect thanks. this fives me confidence that it can be done

could you not have use the M42-M48 to connect the EFW directly onto the M54-M48 adaptor that gets bolted on to the 268M.

Which retailer did you get the camera from - i usually do FLO, but they done seem to do QHY268M. would be nice to get it from within the UK.

Best Regards

I can recommend Astrograph, though their EShop is a bit flakey. Better to email Rupert directly.

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  • 1 month later...
On 08/03/2021 at 09:06, Deeko said:

Hi Rsarwar, the photo shows exactly that. In the photo the M54-M48 adaptor is bolted onto the camera first, then the T2-T2 adaptor (with the M42-M48 ring) to make it T2-M48, so the M48 side screws into the cameras M54-M48 adaptor and the other T2 end straight into the EFW. I admit it is quite confusing and tool me some time to figure it out until I had the camera and adaptors in my hand.

Hi @Deeko - Finally got my qhy268m yesterday. still waiting for some M48 extenders to use with FF/CC for 55mm. However I wanted to ask you about the BF. Looking at the engineering drawing of the device, did you take the backfocus to be 12.5 mm or  12.5 + 1.8mm. I am not sure if that 1.8 mm extrusion is absorbed within the QHY FIlterwheel or is accounted by some other way. The confusion arises because no one seemed to have mentioned it in all the writeup i have read - they all say backfocus is 12 .5mm, when it appears to be 14.3 mm

 

image.png.ade64f2ab95f8179e947b22900250813.png

Edited by rsarwar
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