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Samyang 135mm f2.0 + ASI1600mm-Pro + ZWO EFW

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#1 elginroad87


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Posted 30 November 2020 - 10:00 AM



I am considering buying a Samyang 135mm f/2.0 lens for my new ASI1600mm-Pro Mono camera with a 8-slot ZWO EFW. I have several questions regarding this setup and hoping to get some guidance on:


1. Samyang 135mm is available for all major camera brands, including Cannon, Nikon, Sony, Fuji, Pentax, etc. Is there a "preferred" Samyang model that I should consider for my new ASI setup? 


2. I am also looking for accessories to connect the Samyang lens with the ASI1600+EFW and was wondering if the spacers and connectors that ship with the ASI1600+EFW would suffice to get the spacing right or do I need any additional connector/adaptors? 


3. What is the best way to mount Samyang+ASI1600+EFW on a Star Adventurer 2i? Would a ZWO Holder Ring for ASI Cooled Cameras be sufficient or would I need something else?






#2 Gipht



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Posted 30 November 2020 - 10:14 AM

Since the Samyang lens is set up to focus at the  camera sensor, there is not a lot of room to work with.   With my canon lens adapter, there is not enough room for any filter wheel.   I do have room to install a single filter in line.  To give yourself more room,  buy as thin a lens adapter as possible.  Even then, I suspect you will need a thin slide filter.

#3 troske


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Posted 30 November 2020 - 08:15 PM

I am using the Rokinon brand 135mm f/2 with the Nikon mount on a ZWO1600MM-Pro and the 8-Position EFW. 


Lens is attached to the ZWO T-Ring adapter for Nikon. There is a newer version of this ring. I am using the previous version. That adapter screws into the filter wheel and the filter wheel is screwed together with the camera.


The assembly is mounted on a generic dovetail from Amazon with the ZWO camera holder and a Samyang lens collar. I had to put a small shim under the ZWO camera holder to level everything.


The ZWO camera holder has an Arca-Swiss plate that I use to attach my guidescope. 


This all rides on a Star Adventurer, but I had to add a second counterweight to the SA.


I just added a stepper motor and belt drive which is going to cause balancing problems for me, more counterweight will be required.


Hope this helps.



Attached Thumbnails

  • Rokinon to ZWO.jpg

#4 Cometeer



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Posted 03 December 2020 - 05:40 AM

I probably have the exact solution that you are looking for. I bought the Canon version of the lens and replaced the rear bayonet with a Astrojolo M48 threaded bayonet. An alternative is the Astro Essentials adapter sold by FLO. These threaded connections are less susceptible to tilt than the traditional camera bayonet adapters.


The backfocus requirement for the Canon lens is 44mm. Add another 1mm for filters in the EFW. The sensor distance for the 1600mm eats up 6.5mm. The EFW takes up another 20mm. Most likely, the adapters that comes supplied with the 1600mm will not work (likely too long). 

Here’s my imaging train:

Samyang 135mm f/2 with requirement of 45mm (the extra 1mm due to my 3mm thick Astrodons)

M48 bayonet adapter - 4mm

M48 to M42 adapter - 4mm

spacer - 10mm

thin spacer - 0.5mm

ZWO EFW - 20mm (the 2mm M42 male to male adapter is not used)

1600mm - 6.5mm


I recommend the William Optics Redcat mounting ring.  Fits perfectly on this lens and is close to the center of gravity. See my pic here: https://www.cloudyni.../#entry10329210

Edited by Cometeer, 03 December 2020 - 06:02 AM.

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