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Samyang 135 type lens with electronic focus?

Samyang 135mm F2.0 ED UMC Equipment Buying Advice
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Alien_Enthusiast avatar
Alien_Enthusiast avatar
Dear AstroBinners,

I recently tested my new setup consisting of Samyang 135 f2 lens and ZWO ASI 585 MC camera.

Camera is great, but the lens doesnt seem to be so good.



I have 2 main problems with it:

1. Manual focus (its pure suffering to get it to perfection, even with bahktinov mask, it can take a lot of time)

2. Lens is too fast, and as Im imaging from the city, its f2 ratio is an overkill, so I either have to do 5sec exposures, or lower the f-ratio, which defeats the whole purpose of having such a fast lens



My question is simple - are there any similar lenses that have electronic focus? (preferably with Sony E adapter)



I dont care as much about the f ratio and the exeptional optical quality, as I mostly image from polluted areas. What I do care about, however, would be the speed at which I can setup my rig and get it to work. Most of the time I have ~2 hour sessions, so setting up the manual focus for 40min is a problem.

I do know that there are manual autofocusers designed for for Samyang type lenses, but they not only add bulk but price. My goal is to simplify operations. Electronic focuser would be the ideal solution in this case.
Engaging
Brian Puhl avatar
Brian Puhl avatar
There are a few options to add an EAF to your Roki/Sammy 135.   This is the one I have, it's well built.     I haven't added my EAF yet as it's out on loan, but I have no concerns that it wont work.

If your concerned, I'd just stop down the lens and use this setup.   With a computer/mini pc and NINA behind it, you'll be up and running in minutes.

https://agenaastro.com/astrodymium-ring-system-with-zwo-eaf-asiair-mount-for-rokinon-samyang-135mm-f-2-lens-rs-135-eaf-s.html
Steve de Lisle avatar
Steve de Lisle avatar
I have added an EAF using the Astrodymium system that Brian Puhl  mentioned. When used in conjunction with a Skywatcher GTI mount, guide scope and ASIAIR, i can easily get 5 minute subs with my Samyang 135mm lens and ASI294MC pro camera. I do stop it down to F4, but it works well and is very portable.
Helpful
Jan Erik Vallestad avatar
Jan Erik Vallestad avatar
I use the Astrodymium system with the EAF. Recently did my first run with the 2600MM to check for backfocus adjustments. I stopped down to about F/2.8 with step down rings.

stars after correct only in bxt vs before:


Example from outside the centre (only STF):



I think there is about 13 subs at 10 minutes in there, backfocus can be a problem to adjust. I'm going to use 0.1mm shims. The EAF works wonders though
D. Jung avatar
D. Jung avatar
Get the Bajonett replacement from flo

https://www.firstlightoptics.com/adapters/astro-essentials-samyang-lens-to-m48-adapter.html

​​​​If you have a 3d printer you can print the holders yourself. I can upload my diy design.


The diy solution is a lot cheaper, about 50€ with the motor and Arduino making the bulk of the cost.
Alien_Enthusiast avatar
Alien_Enthusiast avatar
The EAF seems like a promising upgrade, but there is one major problem that makes it unusable for my purposes.

It need its own source of power.

The whole idea is to have a setup which fully runs off my laptop.

For this exact reason Im using 585 instead of 533 cooled one. Cooling is nice, so is EAF, but I cannot afford to carry the weight of additional power supply. I need it to be as light as it gets.

Running ASI 585 from my laptop feels truly amazing. No bulk. No batteries like in DSLR. My laptop has enough battery to support it for multiple hours. Great.

Star Adventurer runs of AA battaries. Even better.



So Id need something like this but for lens. Like with some of those DSLRs where you just plug the thing into your laptop and you can adjust focus from your PC.

Idk if thats even possible - but thats my dream 

So if you know any lenses that work that way let me know!
D. Jung avatar
D. Jung avatar
You can run the focuser with 5v. Even if it required 12v you could use a 5v to 12v DC converter.
Bob Lockwood avatar
Bob Lockwood avatar
If your worried about power, they don't get much smaller than this, and cheap.
Set it behind your laptop, you'd never know it's there.
Alien_Enthusiast avatar
Alien_Enthusiast avatar
Bob Lockwood:
If your worried about power, they don't get much smaller than this, and cheap.
Set it behind your laptop, you'd never know it's there.

Would they allow such thing on a plane?
Bob Lockwood avatar
Bob Lockwood avatar
You'd need to check with the airline. Being such a small battery, you may be able to carry-on, or it may need to be checked.
Well Written
D. Jung avatar
D. Jung avatar
I'd be very surprised if you were allowed to bring this on a plane. Lithium batteries can be very dangerous on a plane and airlines have strict limits on the max capacity, usually 100Wh or less. I can only imagine the discussion with the security personnel 😬
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Brian Puhl avatar
Brian Puhl avatar
Alien_Enthusiast:
The EAF seems like a promising upgrade, but there is one major problem that makes it unusable for my purposes.

It need its own source of power.




No it doesnt.  I think the old revisions might have required a barrel jack 12v, but I have 3 of them and all 3 run off USB power.

Please listen to what we're telling you.   We might know a few things    Stick with your Roki, get an EAF.

Edit:  Here's the blurb about 12v vs 5v


Found here:
https://agenaastro.com/zwo-eaf-electronic-automatic-focuser-standard-5v-eaf-std.html
Bob Lockwood avatar
Bob Lockwood avatar
D. Jung:
I'd be very surprised if you were allowed to bring this on a plane. Lithium batteries can be very dangerous on a plane and airlines have strict limits on the max capacity, usually 100Wh or less. I can only imagine the discussion with the security personnel 😬

 Yep, just looked into this. It's very unlikely you will get a 10Ah battery on an airplane.
Eric Gagne avatar
Eric Gagne avatar
Brian Puhl is right.  My zwo eaf works off usb 2
.0, there is no 12v plug on it.

I also have the samyang 135 with the astrodymium mount.  With the eaf and guiding I can easily do 5 minutes exposures, possibly more if there is no wind, at f/2.8

I stop down at 2.8 as all the youtubers who tested the rokinon/samyang for astro say it's not that good at 2.0
Guillaume Seigneuret avatar
Guillaume Seigneuret avatar
For those interested in having a full automated set with the 135mm Rokinon f/2.0, there's a great kit on Azure3Dprint

https://azur3dprintshop.com/92-support-samyang-pro.html

Here is my set with a ZWO EAF:



Works great: 

https://www.astrobin.com/ykh21r/
https://www.astrobin.com/i7hdch/
https://www.astrobin.com/q4n2wv/
https://www.astrobin.com/y87j0h/B/
Gael Gibert avatar
Gael Gibert avatar
Guillaume Seigneuret:
For those interested in having a full automated set with the 135mm Rokinon f/2.0, there's a great kit on Azure3Dprint

https://azur3dprintshop.com/92-support-samyang-pro.html

Here is my set with a ZWO EAF:



Works great: 

https://www.astrobin.com/ykh21r/
https://www.astrobin.com/i7hdch/
https://www.astrobin.com/q4n2wv/
https://www.astrobin.com/y87j0h/B/

I've got the same and I love it !
Fabian Butkovich avatar
Fabian Butkovich avatar
I have a similar struggle with my ASI183MC + Sigma 150-600mm lens and am currently working on a custom designed ZWO to EOS adapter that maintains the electronic interface between the lens and camera. I plan to eventually make it work with ASCOM so essentially it will just use the lens' already built in autofocusing capabilities. 

This could potentially be a game changer for many of us that use Canon EOS lens' for deep sky AP. 

The 3D printed EAF solution above is genius and simple however!
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Dan H. M. avatar
Dan H. M. avatar
I just got a Sigma Art 135 and I love it. If you can get an Astromechanics adapter for it it’s much much cleaner than any of those belt drive systems for the Rokinons. I’ve tried almost all of them and they just don’t feel right. There’s even a 3D-printed kit from Astrokraken for the Sigma which I’ve ordered.
Tarun Kottary avatar
Tarun Kottary avatar
+1 for Sigma art 135+ Astromechanics! Here's my dual rig 2400mc +135 arts powered by Astromechanic