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Rubinar 5.6/500 Mirror Astigmatism? RESOLVED
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PostPosted: Tue May 22, 2018 2:28 am    Post subject: Rubinar 5.6/500 Mirror Astigmatism? RESOLVED Reply with quote
I have also posted this in the care and repair forum. Maybe similar to what cooltouch is experiencing with his 600mm Sigma mirror, I am having difficulty with my Rubinar.

I've finally received my much anticipated Rubinar mirror only to be disappointed by a focus issue. I can see while focusing that there is a double image and even when focused as perfectly as possible, an apparent astigmatism problem causes unsharp images. The picture I'm including shows this especially with the birds' eyes, which appear double.

Does anyone have experience correcting these type problems? From what I have been able to find, there is an element near the rear that is supposed to do astigmatism correction.



Last edited by woodrim on Wed May 23, 2018 11:37 pm; edited 1 time in total


PostPosted: Tue May 22, 2018 5:51 am    Post subject: Reply with quote
Sad to hear that. Most likely some deadjustment..

PS: no double posting please - have removed the 2nd one


PostPosted: Wed May 23, 2018 11:24 pm    Post subject: Reply with quote
Hopefully, this will help someone else in the future. I have resolved the problem. After reading some things I found in searches, I loosened the four screws that hold the M42 thread to the lens. I didn't tighten them again, just turned until snug. I also loosened the tripod collar and the tripod mount I had secured to the bottom. However, I think it was the M42 mount that was too tightly screwed and somehow caused distortion to an element.


PostPosted: Thu May 24, 2018 2:32 am    Post subject: Reply with quote
Like 1 Congrats


PostPosted: Thu May 24, 2018 5:35 am    Post subject: Reply with quote
woodrim wrote:
Hopefully, this will help someone else in the future. I have resolved the problem. After reading some things I found in searches, I loosened the four screws that hold the M42 thread to the lens. I didn't tighten them again, just turned until snug. I also loosened the tripod collar and the tripod mount I had secured to the bottom. However, I think it was the M42 mount that was too tightly screwed and somehow caused distortion to an element.


A well know problem... Like 1 Like 1 Like 1


PostPosted: Thu May 24, 2018 10:58 am    Post subject: Reply with quote
kds315* wrote:
woodrim wrote:
Hopefully, this will help someone else in the future. I have resolved the problem. After reading some things I found in searches, I loosened the four screws that hold the M42 thread to the lens. I didn't tighten them again, just turned until snug. I also loosened the tripod collar and the tripod mount I had secured to the bottom. However, I think it was the M42 mount that was too tightly screwed and somehow caused distortion to an element.


A well know problem... Like 1 Like 1 Like 1


Not so well known solution for the problem... Smile


PostPosted: Thu May 24, 2018 1:12 pm    Post subject: Reply with quote
kds315* wrote:

A well know problem... Like 1 Like 1 Like 1


Where were you on the 22nd? :-/ Confused


PostPosted: Thu May 24, 2018 1:38 pm    Post subject: Reply with quote
woodrim wrote:
kds315* wrote:

A well know problem... Like 1 Like 1 Like 1


Where were you on the 22nd? :-/ Confused


Busy working... Wink


PostPosted: Thu May 24, 2018 7:58 pm    Post subject: Reply with quote
No element distortion or anything like that, the lens simply wasn't hitting infinity, adjusting the M42 mount fixed that.

It was just out of focus....


PostPosted: Thu May 24, 2018 8:21 pm    Post subject: Reply with quote
Glad to read you found your problem, Woodrim. My Sigma 600 has a Canon EOS mount and a tripod mount that has a lock screw, which spins freely when the screw is loosened. So I don't think that's the problem, although to be honest, I don't think I've ever used this lens when that screw wasn't tight. Might at least be something to try.

You've inspired me to do something about my Sigma 600 and I've started to dismantle it. Rather than clogging up your thread with the details, however, I'll go and dig out my thread on the Sigma and update it. Wish me luck!


PostPosted: Thu May 24, 2018 11:22 pm    Post subject: Reply with quote
cooltouch wrote:
Glad to read you found your problem, Woodrim. My Sigma 600 has a Canon EOS mount and a tripod mount that has a lock screw, which spins freely when the screw is loosened. So I don't think that's the problem, although to be honest, I don't think I've ever used this lens when that screw wasn't tight. Might at least be something to try.

You've inspired me to do something about my Sigma 600 and I've started to dismantle it. Rather than clogging up your thread with the details, however, I'll go and dig out my thread on the Sigma and update it. Wish me luck!


I was thinking of you the whole time. Good luck with yours, Michael.


PostPosted: Thu May 24, 2018 11:25 pm    Post subject: Reply with quote
iangreenhalgh1 wrote:
No element distortion or anything like that, the lens simply wasn't hitting infinity, adjusting the M42 mount fixed that.

It was just out of focus....


Wrong again. First of all, the subject was well short of infinity. Out of focus does not cause double images. It is and was as I said.
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