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Celestron Focus Motor - A Brief Review (RASA 11)

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#26 th3r3ds0x

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Posted 01 July 2019 - 01:58 PM

I didn’t try that with the retro, let me know how that goes. My other focus motor comes today, I’ll update on the result.

#27 calvincarter

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Posted 01 July 2019 - 03:45 PM

One more thing, I’m using the Starizona filter slider, they make a 20mm adapter made specifically for the RASA 11.  So the 294 with the 11mm adapter, the drawer, and the starizona 20mm will get you right at 55mm from the Celestron camera adapter.  If you use a filter slider or something other than the celestron LP filter, the optical window should be removed.  Info is scarce.

Thank you for telling me this. This is my setup:

 

ASI294MC Pro 6.5mm

t2 extender 11mm

extender 21mm

extender 16.5mm

M54 camera adapter 2mm

Baader UFC Filter drawer 13mm

Baader RASA 11 adapter 3mm

Then the scope.

 

So that's a total of 73 from the viewing window. Right?

 

Is this the right amount?

 

Also, I have left the Removable Optical Window (the "clear filter") in. Am I supposed to take that out? I'm not using a screw on Celestron filter. I'm using a Nebulosity filter inside the Baader UFC filter drawer. Am I correct that I would leave the Removable Optical Window in?

 

And does this seem like the correct back focus?

 

Here are 2 photos of my setup and an illustration of the parts (use the link if the photo isn't showing up):

 

 

 

https://photos.app.g...EMEUDgciPGySE69

 

 

 

https://photos.app.g...moQjfrh6eF2JmE9



#28 calvincarter

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Posted 01 July 2019 - 03:57 PM

WELL, I'm not sure if I solved it, but I definitely made a lot of progress today.

 

So, here is what I did.

 

Using the motor, all attached with the retrofit kit etc, I was only able to get about 35000 when "moving out" using the Celestron Focus Utility app for Windows. So, I was essentially getting travel between 0 and 35000, which I think means 35 turns. 

 

I'm not sure how many turns a RASA 11 is supposed to have (does anyone have documented information on this?), But I've heard other people say in this thread that they were trying to get 40 turns.

 

So, Then I removed the motor. And Tried to turn the retrofit piece to see if maybe the motor was weak and not able to do the last 5 turns. It wouldn't budge. So, I slid a phillips screw driver into the hole at the end of the retrofit kit and loosened slightly the screw/washer that is shown in Step 10 of the Celestron Focuser Retrofit Kit installation instructions. 

 

To be honest, I don't know how the mechanics of a telescope focuser work, BUT GUESS WHAT, I was able too get another 2000 (2 turns). Then it stopped. So I loosened the screw just a little bit more. And got another 2000 (now I'm at 39000). 

 

I did it again, but this time the screw came completely loose and I wasn't able to tighten it down. I'm assuming that screw is important, so I didn't want to try it without the screw in there. So, I just worked it for a while to get it to turn as much as possible AND allow me two tighten the screw back. 

 

Eventually I got it to the full 40000. It's daylight here so I can't really do a full test. I did do a daytime long distance focus test, focusing on a house about 1/4 mile away and I was able to get the scope to focus on that (previously it wasn't able to focus on something that far away). In fact, it had more movement it could do. To focus on the house, I had to do 37000. Previously i could only go 35000 so I never got the house into focus. Now I can. Then I can also go to 40000 (beyond the proper focus for the house) before it stops... But I don't know if that's enough for stars if the house was at 37000. Again I don't really understand the mechanics of focusing...

 

I'm a little worried that screw doesn't have much grip though. What will happen if it falls out?

 

Can you try this technique to see if it works for you?

 

And how many turns does the RASA 11 support so I know I'm getting the full travel.

 

Thanks!!!!



#29 44maurer

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Posted 01 July 2019 - 04:08 PM

I have tried loosening the screw enough that it did not tighten up when focusing, the problem then was that eventually the screw fell out. With out the screw, the motor will just spin and spin (in one direction, the other will be fine).



#30 th3r3ds0x

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Posted 01 July 2019 - 08:30 PM

I’m about to start fiddling with mine, have a second focus motor to try. I counted revolutions with the black knob on the feather touch and I get 40 give or take in case I mis counted a turn. If I can’t make it work with the screw tightened properly then I’ll just return it. Don’t want to introduce a new problem.

#31 th3r3ds0x

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Posted 01 July 2019 - 09:49 PM

According to the rasa white paper the optical path is designed for one filter. Having more than one or a filter and the optical window will throw off the focus. So if you are using another filter regardless where in your train then you should remove the optical window.

#32 th3r3ds0x

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Posted 01 July 2019 - 09:52 PM

2nd focus motor did like the first. My retro focuser is quite snug and I’m sure that’s the issue. No telling if it’s the retro kit or my RASA but it ticks me off. 3600$ scope you would think a first party made part would fit like a glove and work perfectly. I’ll probably keep one for my 8SE and return the other. Maybe one day they will get their stuff together but right now I haven’t even heard from them regarding the ticket I opened. Oh well.

#33 calvincarter

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Posted 01 July 2019 - 10:20 PM

2nd focus motor did like the first. My retro focuser is quite snug and I’m sure that’s the issue. No telling if it’s the retro kit or my RASA but it ticks me off. 3600$ scope you would think a first party made part would fit like a glove and work perfectly. I’ll probably keep one for my 8SE and return the other. Maybe one day they will get their stuff together but right now I haven’t even heard from them regarding the ticket I opened. Oh well.

Do you think you'll get a replacement retro fit part? Maybe the one you have is a dud? 



#34 calvincarter

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Posted 01 July 2019 - 10:25 PM

I’m about to start fiddling with mine, have a second focus motor to try. I counted revolutions with the black knob on the feather touch and I get 40 give or take in case I mis counted a turn. If I can’t make it work with the screw tightened properly then I’ll just return it. Don’t want to introduce a new problem.

Did you try what I did and loosen the screw and turn the focuser manually counter clockwise a little more, repeating this process over and over, until the screw won't tighten back, then backing off the focus clockwise a turn or so to the point that you can get the screw to tighten again. 

 

When I did this I was able to nudge it up to 40000 little by little.

 

I have NO idea why this happened to me and not everyone else. Others say it installed fine. I don't know what I could have done wrong. But it's good to know I'm not alone. I just hope we can both figure it out. ;-)



#35 th3r3ds0x

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Posted 01 July 2019 - 10:34 PM

One more thing, I don’t think it’s the screw that holds the retro focuser to the shaft it’s perhaps a design flaw. Mine rotated free right up until I snug up the 3 screws that hold the anodized aluminum plate. So there is a tolerance either with the retro or the plate that is pinching it. Motor struggles to rotate it. Poor design or perhaps manufacturing of either the focuser, or even the scope that’s out just out of spec enough to cause the issue. Guess I’ll just have to deal with the feather touch and look for something after market. I’m betting if I tried enough retro focusers I’d get a good one but I’m not quality testing Celestron products. Real shame.

#36 th3r3ds0x

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Posted 01 July 2019 - 10:47 PM

Did you try what I did and loosen the screw and turn the focuser manually counter clockwise a little more, repeating this process over and over, until the screw won't tighten back, then backing off the focus clockwise a turn or so to the point that you can get the screw to tighten again. 

 

When I did this I was able to nudge it up to 40000 little by little.

 

I have NO idea why this happened to me and not everyone else. Others say it installed fine. I don't know what I could have done wrong. But it's good to know I'm not alone. I just hope we can both figure it out. ;-)

I didn’t want to try that.  This seems to be an issue of poor QA and these parts being slight out of spec.  Once the orange plate holding the retro focuser is attached with the 3 screws the focuser is noticeably harder to turn.  Maybe even removing the rubber O-ring behind the retro focuser would free things up.  The motor just struggles to turn it once it’s installed per instructions.  



#37 calvincarter

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Posted 01 July 2019 - 10:50 PM

I didn’t want to try that.  This seems to be an issue of poor QA and these parts being slight out of spec.  Once the orange plate holding the retro focuser is attached with the 3 screws the focuser is noticeably harder to turn.  Maybe even removing the rubber O-ring behind the retro focuser would free things up.  The motor just struggles to turn it once it’s installed per instructions.  

Now I'm thinking maybe if the orange cover plate wasn't tightened down fully. Maybe that will give the retrofit piece a little wiggle room. Or maybe even flip the orange plate around so that the depressed side is facing inwards towards OTA?



#38 th3r3ds0x

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Posted 01 July 2019 - 11:50 PM

Oh I have no doubt that if you loosen the plate a little it will rotate free.  Only problem is the focus motor attaches to that as well so that motor would be able to move if the plate is not held securely to the ota, you would not want that.  Hopefully Celestron will address this issue and put out a revision.  Time to start looking at other options.  Disappointing.



#39 44maurer

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Posted 02 July 2019 - 12:44 AM

One more thing, I don’t think it’s the screw that holds the retro focuser to the shaft it’s perhaps a design flaw. Mine rotated free right up until I snug up the 3 screws that hold the anodized aluminum plate. So there is a tolerance either with the retro or the plate that is pinching it. Motor struggles to rotate it. Poor design or perhaps manufacturing of either the focuser, or even the scope that’s out just out of spec enough to cause the issue. Guess I’ll just have to deal with the feather touch and look for something after market. I’m betting if I tried enough retro focusers I’d get a good one but I’m not quality testing Celestron products. Real shame.

On my second call to Celestron, they did warn to ensure the focuser remain centered as you tighten the 3 screws. they advised not to tighten 1 screw, but to gradually do all 3 making sure the focuser remains centered. This didn't work for me. I also found that if I left the plate loose, it worked better. But it has never worked correctly, always same end result, locked up and cant move the focuser until remove the center screw.



#40 calvincarter

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Posted 02 July 2019 - 12:58 PM

On my second call to Celestron, they did warn to ensure the focuser remain centered as you tighten the 3 screws. they advised not to tighten 1 screw, but to gradually do all 3 making sure the focuser remains centered. This didn't work for me. I also found that if I left the plate loose, it worked better. But it has never worked correctly, always same end result, locked up and cant move the focuser until remove the center screw.

Do you mean they were saying make sure it didn't get pinched or touched by the cover plate itself, which would produce drag on the turning motion?

 

Just trying to make sure I fully understand "centered". 

 

And, is there anything you could really do if it wasn't. Meaning, I don't see these screw holes as big enough to be adjustable. And unless the retrofit kit or the focus shaft on the OTA is bent, wouldn't it be straight and if it wasn't you couldn't do anything about it anyways?



#41 calvincarter

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Posted 02 July 2019 - 01:03 PM

Ok now I have a related but different question. I'd appreciate any answers ya'll can provide or even point me to other threads you think could help. I will also look at the threads.

 

Assuming one gets the Celestron focus motor to work - this is a big assumption ;-), are people using the Celestron Focus Utility, or are you using SharpCap's Focus Tool, or some other auto focus program?

 

My tech stack is primarily Sky Safari for telescope control, planning and pointing.  Then SharpCap Pro for live stacking and camera control.

 

And I don't think the SharpCap focus tool actually controls the motor directly or does auto focus. I think it just gives you feed back as you change the focus yourself.

 

But what piece of software will automagically control the focus motor directly and periodically change focus to prevent the OTA from going out of focus on a long night of captures? I prefer not to move away from SharpCap as I like the "beginner friendly features" like LiveStacking. So if there is a single purpose utility for auto focus, that may be best. But I'm open to anyone's opinion here. THANK YOU!



#42 th3r3ds0x

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Posted 02 July 2019 - 01:08 PM

Ok now I have a related but different question. I'd appreciate any answers ya'll can provide or even point me to other threads you think could help. I will also look at the threads.

 

Assuming one gets the Celestron focus motor to work - this is a big assumption ;-), are people using the Celestron Focus Utility, or are you using SharpCap's Focus Tool, or some other auto focus program?

 

My tech stack is primarily Sky Safari for telescope control, planning and pointing.  Then SharpCap Pro for live stacking and camera control.

 

And I don't think the SharpCap focus tool actually controls the motor directly or does auto focus. I think it just gives you feed back as you change the focus yourself.

 

But what piece of software will automagically control the focus motor directly and periodically change focus to prevent the OTA from going out of focus on a long night of captures? I prefer not to move away from SharpCap as I like the "beginner friendly features" like LiveStacking. So if there is a single purpose utility for auto focus, that may be best. But I'm open to anyone's opinion here. THANK YOU!

I intend to use the built auto-focus functionality in Sequence Generator Pro.



#43 th3r3ds0x

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Posted 02 July 2019 - 01:12 PM

Do you mean they were saying make sure it didn't get pinched or touched by the cover plate itself, which would produce drag on the turning motion?

 

Just trying to make sure I fully understand "centered". 

 

And, is there anything you could really do if it wasn't. Meaning, I don't see these screw holes as big enough to be adjustable. And unless the retrofit kit or the focus shaft on the OTA is bent, wouldn't it be straight and if it wasn't you couldn't do anything about it anyways?

The focus shaft has a little bit of wiggle so as you screw the plate down, tightening the screws down evenly at once instead of fully tightening down 1 screw before tightening the next, just make sure the retro focuser appears centered in the plate while you snug up the screws.  Mine was nice and center but just won’t spin without resistance.



#44 th3r3ds0x

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Posted 13 July 2019 - 12:01 PM

Celestron is sending me a replacement focus motor and retro kit. I will try the replacement retro focuser and see if it rotates free or with resistance like the old one. Will update when I have finished.

#45 Ron in Michigan

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Posted 15 August 2019 - 06:06 PM

I'm confused by what you're talking about here?  The RASA comes with a FT focuser - why not just add a FT motor?  I did, installed with no instructions in about 60 seconds. 
MY steps in NINA are 2000.  (wow that's a lot) but it takes a lot to change the focus a little.  Still working well, I have nina set to shoot 2 exposures and average them to find the HFR. This took out most all seeing issues from making focus unstable.  My focus line in nina.  (whats all the retro stuff I keep reading?)


 

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#46 Ron in Michigan

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Posted 15 August 2019 - 06:11 PM

Now I stumbled onto this because I'm remote and I've had some HORRIBLE unflat fields - or at least not fully in focus. I wondered if the VERY LOOSE locks were allowing the mirror to flop and not square up.  So today I locked them down then unlocked them almost a full turn instead.  I read above someone else did this. I'm hoping it levels out the mirror.  Else I will focus and go out and lock it just to confirm that this is the problem.

I have sharp focus center and left - and DONUTS (out of focus) on the far right side of the full frame sensor.   I think tilt or spacing issues would distort the stars (smear them) as is the result of too close or too far (spacing). Since the donuts look fairly circular - I'm thinking it has to be mirror flop or some other issue. (the center lens elements rotate when putting on a camera) I'm thinking these may be aligned at factory and should not move? 

I've had 5 months of problems with the RASA 11 and finally contacted Celestron and my dealer (highpoint Scientific) for a solution.

 

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#47 kingjamez

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Posted 15 August 2019 - 07:22 PM

The center elements rotate on the RASA 11? They don’t on the RASA 8.

That looks like tilt to me. With the left third probably being the true focus point such that the middle and left edge aren’t too bad where the right side is a few microns off.

Edited by kingjamez, 15 August 2019 - 07:25 PM.


#48 th3r3ds0x

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Posted 15 August 2019 - 08:25 PM

I'm confused by what you're talking about here? The RASA comes with a FT focuser - why not just add a FT motor? I did, installed with no instructions in about 60 seconds.
MY steps in NINA are 2000. (wow that's a lot) but it takes a lot to change the focus a little. Still working well, I have nina set to shoot 2 exposures and average them to find the HFR. This took out most all seeing issues from making focus unstable. My focus line in nina. (whats all the retro stuff I keep reading?)



In another thread I asked for recommendations on focus motors for the Rasa 11. No replies there but I ended up going with a MicroTouch focuser. Works fine. The celestron solution works for some, not for others. Hope you get your RASA issue sorted. I think some of these things get beaten up a little too much in delivery.

#49 calvincarter

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Posted 15 August 2019 - 08:45 PM

Ok. Everyone I am trying to decide between these 2 focuses:

Focus cube 2
$330
https://www.highpoin...edgehd-fcv2-c11

Micro touch
$500
https://starizona.co...tofocuser-wired

Or (and I can’t tell what the difference is other than different looking controller)

https://www.highpoin...-with-motor-mts

Does anyone have any ideas?

I would appreciate both opinions and experience. :-)

#50 th3r3ds0x

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Posted 15 August 2019 - 08:59 PM

I installed the MicroTouch last week.  Very easy to install and works fine wish SGP via ASCOM.  The control box is rather large but light.  I just Velcro’d it to my ota.  After dealing with the mess that is the Celestron focus motor, the MicroTouch just worked.  The temp sensor on the control box is off a bit but they do allow you to offset it via settings.  I’m using the environment sensor from my Pegasus pocket power-box though but I’m sure the sensor on the MicroTouch would do as well.  Overall I’m happy.  

 

Want to shout out to HighPoint Scientific for their wonderful support and taking the Celestron motor back after Celestron was unable to provide a part that worked with my ota.  Always top-notch service from those folks.




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