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Baader Steeltrack + C9.25 advice sought

Celestron EdgeHD 9.25" ZWO EAF Equipment Focuser Auto-Focusing
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Sean van Drogen avatar
Sean van Drogen avatar
Managed to get a nice 2nd hand Baader Steeltrack to put on my 2nd hand C9.25 that I got a while ago. My challenge is now the following.
Am using this setup with the 0.63 reducer and have calculated that I have a Critical Focus zone of 113 Micron. Now I had a ZWO EAF laying about that I connected to the setup but each step size for this 3.75 Micron giving me just 30 steps to get optimal focus.

Looking for thoughts on how to upgrade this setup so that I can get something that is better for automation.

Thanks in advance for any thoughts.
andrea tasselli avatar
andrea tasselli avatar
I'd modify it to add a 2:1 or 3:1 reduction ratio via pulley and belt. But that's just me.
Andy Wray avatar
Andy Wray avatar
Have you tried the EAF yet, because I would guess that it would actually work quite well.
Sean van Drogen avatar
Sean van Drogen avatar
Andy Wray:
Have you tried the EAF yet, because I would guess that it would actually work quite well.

Mechanically it works and I might be overthinking this (strong possibility). The only real world reference I have is my refractor and the stepsize for that setup is 0.13 micron. The fact that the difference is so big makes me take pause.
Andy Wray avatar
Andy Wray avatar
I'm pretty sure that your setup will be fine.  With the coma corrector you only have an F6.3 equivalent scope.  I'm using the EAF 5V on an F4.5 equivalent Newtonian and have no problems achieving accurate focus.  Given that the critical focus zone is directly related to the square of the F number (I believe), my CFZ should be about half the size of yours.

To put the EAF in perspective:  It has 7.5 degree stepper motors that are geared down by a factor of 120.  That means they are accurate to within 0.06 degrees.  They are usually connected to the coarse focusing knob rather than fine.  Even when connected like this, they are accurate to within the equivalent of 0.6 degrees on the fine knob.  If you think about how small a focus change that is if you were to be manually focussing you can see that the EAF is better than any focussing you could do manually.
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Sean van Drogen avatar
Sean van Drogen avatar
as an FYI: found a solution worth trying out (and calming my brain) and nothing that will break the bank
https://shop.deepskydad.com/product/baader-diamond-steeltrack-adapter-for-zwo-eaf/
Somehow it just feels better to have finer steps and control

Thanks @Andy Wray & @andrea tasselli for your helpfull thoughts
andrea tasselli avatar
andrea tasselli avatar
Sean van Drogen:
as an FYI: found a solution worth trying out (and calming my brain) and nothing that will break the bank
https://shop.deepskydad.com/product/baader-diamond-steeltrack-adapter-for-zwo-eaf/
Somehow it just feels better to have finer steps and control

Thanks @Andy Wray & @andrea tasselli for your helpfull thoughts

I might be because I'm slow in the uptake but that on deepskydad is a bracket. How does it help you achieving finer resolution?
Sean van Drogen avatar
Sean van Drogen avatar
andrea tasselli:
Sean van Drogen:
as an FYI: found a solution worth trying out (and calming my brain) and nothing that will break the bank
https://shop.deepskydad.com/product/baader-diamond-steeltrack-adapter-for-zwo-eaf/
Somehow it just feels better to have finer steps and control

Thanks @Andy Wray & @andrea tasselli for your helpfull thoughts

I might be because I'm slow in the uptake but that on deepskydad is a bracket. How does it help you achieving finer resolution?

It runs the fine focus knob instead of the course when installed so immediately 10:1 improvement as I understand it
andrea tasselli avatar
andrea tasselli avatar
Ah, all right. Got it now. I was told not to use the fine focus knob because of the risk of wreaking it. I think I read it somewhere abut adapting Moonlight focusers to autofocusing, possibly on their site?
Andy Wray avatar
Andy Wray avatar
andrea tasselli:
Ah, all right. Got it now. I was told not to use the fine focus knob because of the risk of wreaking it. I think I read it somewhere abut adapting Moonlight focusers to autofocusing, possibly on their site?

I don't believe that the ZWO EAF was really designed to be used on the fine focus shaft.  It will end up doing ten times as much movement as it really needs to to achieve the same result and presumably those movements could take ten times as long.
Sean van Drogen avatar
Sean van Drogen avatar
andrea tasselli:
Ah, all right. Got it now. I was told not to use the fine focus knob because of the risk of wreaking it. I think I read it somewhere abut adapting Moonlight focusers to autofocusing, possibly on their site?

Think it should be fine baaders own motor also runs the fine focus knob
Sean van Drogen avatar
Sean van Drogen avatar
Andy Wray:
andrea tasselli:
Ah, all right. Got it now. I was told not to use the fine focus knob because of the risk of wreaking it. I think I read it somewhere abut adapting Moonlight focusers to autofocusing, possibly on their site?

I don't believe that the ZWO EAF was really designed to be used on the fine focus shaft.  It will end up doing ten times as much movement as it really needs to to achieve the same result and presumably those movements could take ten times as long.

The EAF now runs the entire length of the focuser in less than 8000 steps. The max setting is 60,000 steps for the EAF. Assuming it really goes to 1:10 I will need just below 80,000 steps to run the full length. Perhaps to clarify it does not attach directly to the fine focus shaft but will be belt driven.

Will let you know once I have the bracket what the difference is vs the regular EAF to course knob. They are prediciting clear skies this saturday will test the regular EAF setup then to see what it brings

CS
Sean
Sean van Drogen avatar
Sean van Drogen avatar
Sean van Drogen:
Andy Wray:
andrea tasselli:
Ah, all right. Got it now. I was told not to use the fine focus knob because of the risk of wreaking it. I think I read it somewhere abut adapting Moonlight focusers to autofocusing, possibly on their site?

I don't believe that the ZWO EAF was really designed to be used on the fine focus shaft.  It will end up doing ten times as much movement as it really needs to to achieve the same result and presumably those movements could take ten times as long.

The EAF now runs the entire length of the focuser in less than 8000 steps. The max setting is 60,000 steps for the EAF. Assuming it really goes to 1:10 I will need just below 80,000 steps to run the full length. Perhaps to clarify it does not attach directly to the fine focus shaft but will be belt driven.

Will let you know once I have the bracket what the difference is vs the regular EAF to course knob. They are prediciting clear skies this saturday will test the regular EAF setup then to see what it brings

CS
Sean

Finally had a good chance to test this and I will remove it again. The timing it takes to get from one focus point to another is quite long. When working with offsets it takes 2 minutes to get from one filter set point to get to the other. This adding quite a bit of overhead to my runs as on 3 filters i do 5x60s exposure I add about 5 minutes overhead to 15 minute of captures. So over the whole night I have 25% overhead at least.
I also don't notice any appreciable improvement vs running focus on the course knob like I did before.
Its that the standard EAF bracket just does not attach very well so I will spend another bit of money on the following adapter.
https://www.teleskop-express.de/shop/product_info.php/language/en/info/p14511_TS-Optics-Adapter-Kit-for-ZWO-EAF-Motor-Focus-to-Baader-Diamond-Steeltrack-Focusers.html

CS Sean