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Camera lens and rotator.

Equipment Rotator
15 replies•540 views
Eric Gagne avatar
Eric Gagne avatar
Hello,

Is there such a thing as a rotator for cooled cameras used with a camera lens ?

I use the astrodymium mount with my samyang 135 and the strap for the eaf makes it impossible to rotate the lens and camera together but I would like to be able to change the framing sometimes.

So I am wondering if some or all the adapters I use for the back focus could be replaced by a rotator.

I couldn't find any on google.
andrea tasselli avatar
andrea tasselli avatar
Well, why I don't understand why you just can't rotate the lens here is one. Just add the right lens flange:
https://shop.deepskydad.com/product/field-rotator-1/
Eric Gagne avatar
Eric Gagne avatar
I should have explained in more details.

My lens is "trapped" in the mount and tied to the EAF with a belt.  To rotate it I would have to open the mount, remove the belt from from the EAF, turn the lens (and the camera along), and put everything back together.    It would not only be cumbersome to do it every time I want to rotate, there's a good chance I would throw away my polar alignment.





I shopped on the internet for a manual rotator but there's hardly any specs.  Most manual rotators descriptions talk about flatteners or reducers so I am not quite sure how one fits them on the optical train.

I am hoping there is some rotators that would replace the spacer and/or the EF Mount adapter in this setup
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andrea tasselli avatar
andrea tasselli avatar
There are a number of manual ones too. They might work but induced till might be a consideration.
Eric Gagne avatar
Eric Gagne avatar
I think this will probably do the job.  I am aware that it may induce tilt but I guess the only way to know is to try it.   There are other makes that seem to be of higher quality but they are too thick.  I need something less than 14mm which is the thickness of the spacer I have  between the camera and the T2 adapter.

This one is 12.55mm so with a few spacer I will be able to achieve back focus.   It feels like it might be a little bit flimsy though, I'll see.  But it will have to do until I save up enough money to buy a proper kit.

M42/M48/M54/M68 CAA 360 ° Rotator Camera Angle Adjuster (telescopescanada.ca)
Lynn K avatar
Lynn K avatar
At present I am setting up the same Rokinon 135mm plus the Astrodymium Ring system. I hadn't thought about the restriction of the focus belt on rotating the lens.  Any compositional rotation would take place at the very beginning of a session before rotation. My system is not completely set up. I don't have the ZWO EFM yet. Ihave always used Optec/Starlight focus systems. But, I assume if5he rings were loosened and 5he lens rotated, that the belt would rotate the lens helical focus ring as the lens rotates.  I'm not sure of the travel of the helical focuser would bottom out.  The lens doesn't need to be rotated pass 90 degrees to reach any possible composition..



I am aware of the focuser rotater mentioned in the above thread. I have all 3 versions (42mm, 48mm & 54mm). They are well made and have near 0 flecture. If you can work out the required backfocus. I got mine through AliExpress. But Agena carries them. Mine is an older design an meassered 14mm. I couldn't  fine any backfocuse measurements for the ZWO thinner 42mm adapter. But the 54mm version is 11.5mm. With the 533 should have plenty of backfocuse room.



Lynn K.
Eric Gagne avatar
Eric Gagne avatar
There is a few issues with rotating the lens while the EAF is attached.  

1. It's not that easy to turn.  The eaf will offer resistance and I don't think it's a good thing to manually force it to turn.

2. You would be very limited in how much you can rotate.  Think how far your focus ring would get if you rotate 45 degrees. 

3. Then you would have to reconfigure the limits in the asiair to make sur you haven't turned it up to a point where it would "bottom out" when autofocusing.

It would be best to just remove the belt but it's not that easy, it's quite tight and you don't want to stretch it because it could become loose and create backlash.
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Lynn K avatar
Lynn K avatar
You may be right. As I mentioned, I have never used the ZWO EFM and how ASIair keeps track of the focuser steps. If you use the EFM hand controller, not attacked to to the ASIair, and return the helical focuser to the previous location, would then the motor and ASIair be in sink? I use the Optec and Starlight system. They have clutches to release the motor drive. Also, I'm very new to ASIair. I'm only beginning to use it for the eclipse and this wide field system. I mostly image with a Tak FSQ106ED  and AP130GTX  using MaxmDL and SGP.

I thought the Rokinon/Astrodymium system  using the ASIair Mini would be simple..  But as usual, nothing in astrophotography is simple
Because as uaual the manufacture failed to acount for certain applications. All the ASIair needs is  a software option to rack the focuser all the way in, and re-set to "0". That re-sinks the motor steps. Then type in a step number and the motor moves to best focus position. It may already have this option that I am not aware of.

Lynn K.
Eric Gagne avatar
Eric Gagne avatar
I ordered the one I posted above.  I will report next week when I get it.
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Chris "Roo" Page avatar
Chris "Roo" Page avatar
So I actually am dealing with this same issue currently. I have a filter drawer from ZWO (absolutely needed, L extreme f2) and need to be able to add the rotator as I will be going to a dark sky trip on June 10th. I ordered the aforementioned rotator from agena (blue fireball, m48 version) but unfortunately one side is male and the other is female. The 294mc pro I am using has male threads coming off it (as I presume all astro cameras do) so I cannot connect it on the optical path without using an adapter of sorts. Unfortunately, adding in an adapter puts me just past the critical back focus length and even though I have done Nicos infinity mod on the lens, it still bottoms out.

I'm wondering if maybe I could take the lens apart and mod it more. I'm also wondering if maybe I could find a female to female m48 adapter that would introduce no length, but I haven't yet. I'm kinda at a stuck point and I'm worried that I'm going to run out of time and not be able to frame up my most wanted target properly. Has anyone gotten any further with this issue? Anyone tried manually turning the lens yet? I'll add some photos of the image train along with caliper photos a little later… Imaging the Veil complex at F2 with the filter right now ;) it's a beautiful setup once you get it dialed in. Been working on getting it all just right for well over a year now!

Roo
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Ben Hayes avatar
Ben Hayes avatar
This is a very interesting thread - I've learned a lot already and look forward to future posts.  Thank you, Eric, for taking care to include photographs and carefully articulated notes about what this is all about.  There is a bunch of us out there struggling with the same issue.  I am having a blast connecting ZWO EAFs to my old Nikkor ED lens  for wide field imaging with a cooled camera (ASI294MC or ASI2600MC) at the back and 2" filter drawer in between.  The lens and EAF have to rigidly mounted to a dovetail plate and as such, rotating the camera to frame a new target is a frustrating and dreadful task.  I would love to find out how this camera angle adjuster from telescopescanada works out for you.  Thanks!
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andrea tasselli avatar
andrea tasselli avatar
I still don't get what all this fuss is about or more precisely why this obstinacy in using a (mediocre) electronic focuser when a single hand is all you need. And that would solve all these frame rotation problems. Go figure…
Chris "Roo" Page avatar
Chris "Roo" Page avatar
andrea tasselli:
I still don't get what all this fuss is about or more precisely why this obstinacy in using a (mediocre) electronic focuser when a single hand is all you need. And that would solve all these frame rotation problems. Go figure...

 focusing at F2 is not as easy as ya think. I have had this lens for a year without the focuser and it doesn't hold focus well, At all, and frankly the difference with and without the focuser is night and day in terms of overall image quality and ease of use. I finally just loosened everything up today and manually rotated the lens and that seemed to do the trick.
andrea tasselli avatar
andrea tasselli avatar
I do have the aforementioned lens (Nikon in my case) and holds focus extremely well @ f/2 and compared to my other fast lenses is rather easy to focus. The 300mm AFS OTOH is a bitch in that regard and you need to keep an eye in the night and any degree (C) in temperature drop means a refocus is needed.
Chris "Roo" Page avatar
Chris "Roo" Page avatar
andrea tasselli:
I do have the aforementioned lens (Nikon in my case) and holds focus extremely well @ f/2 and compared to my other fast lenses is rather easy to focus. The 300mm AFS OTOH is a bitch in that regard and you need to keep an eye in the night and any degree (C) in temperature drop means a refocus is needed.

 ive heard more than one person refer to the quality differences in different "copies" of this lens..
Perhaps you got a great example? In any case I would like to point out that what I did would ultimately be very doable in the field in a pinch. Is it as easy or elegant as using a rotator? Of course not. Will it work? Absolutely. If anyone would like a video showing exactly what I loosened/how I performed the manual rotation let me know and I'll be happy to upload one.
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Eric Gagne avatar
Eric Gagne avatar
I forgot I had posted this.  The rotator turned out to be unusable in my case because I forgot to take the thickness of the canon EF adapter into account so it's simple impossible to achieve back focus.

In the end I came up with a different solultion……………..I bought a scope that comes with a rotator smile
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