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QHY294MM and Samyang 135mm/F2

ZWO ASI294MM Pro CMOS Acquisition Deep Sky Help Needed
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Pablo Petit avatar
Pablo Petit avatar
Hello everyone !

I am looking for a way to connect my QHY294MM, my ZWO 8*1.25 filter wheel and my Samyang 135mm/F2.

The lens has a Nikon mount and needs 46.5mm of backfocus.
I've bought, without thinking about the backfocus issue, a ZWO lens adapter, but it is simply too big at a width of 20mm. 
Adding that to the 20mm of the wheel, a 3mm male-male M42 and the 17.5mm backfocus of the 294MM my final backfocus is 60.5mm … way to much.

Has anyone encountered the same problem ? Is there a set of adapters that could allow such a setup to be put together ? 
It seems that the M42 adapter of the camera can be unscrewed, but I can't find anything to replace it. A male M42 would be perfect…

A way to connect the camera directly without the filter wheel but with the possibilty of having a filter beetwen them could also work, but again, I could not make it work ..


Thanks for any advice and clear skies !
Engaging
Carastro avatar
Carastro avatar
What country are you in? 

One of the UK Astrophophotographers designed an adapter that you attach to the lens in place of the bayonet.  It's available from First Light Optics.  

Of course you can't then use a DSLR on the back without reversing the process, but maybe this might help.  

I have the same lens but have an Atik Camera and Atik EFW, and bought a ZWO adapter as I didn't want to remove the bayonet in case I wanted to use the DSLR, but can only just get focus.  

Not even sure this will help, but this is the link:
https://www.firstlightoptics.com/adapters/astro-essentials-samyang-lens-to-m48-adapter.html

Carole
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Minh Lết avatar
Minh Lết avatar
If you can buy from taobao then buy this. (It's on aliexpress too. Make sure to require the seller to send exactly like pictured. https://item.taobao.com/item.htm?spm=a230r.1.14.36.10007b7cI82XJw&id=526022788215&ns=1&abbucket=6#detail
it has a 2inch filter thread inside the adapter so you do not need the filter drawee. The backfocus also variable by thread lock so you can adjust it accordingly for various lens. Some of my lens are ultrawide with razor narrow focus travel (0.8mm) for the whole range which required sub milimeter backfocus accuracy otherwise it wont focus. I cannot reach focus by anything else but this.
Michel Makhlouta avatar
Michel Makhlouta avatar
ZWO already have an adapter for this:
https://astronomy-imaging-camera.com/product/nikon-t2-adapter-for-efw-asi1600

It will give you exactly what you need, the 294MM should be connected to the EFW without the 11mm ring, so it is 6.5mm, not 17.5:
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Pablo Petit avatar
Pablo Petit avatar
Thank you for all of your responses ! I didn't expected that much.

I realise that everything seems simpler with ZWO cameras, but I happen to have the QHY. And with a Nikon lens, because otherwise its too easy …

Thank you minhlead ! I'm going to buy the adapter, I think it will just do it ! (For some reason I can only see the link on my phone and not on my deskop pc, if someone has the same problem and is looking for the adapter, I could find it on aliexpress, just search for "S8037" )

Thank you all !