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Octopi Tilter Adjustment

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#1 belbakri

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Posted 30 May 2024 - 11:06 AM

I am hoping the experienced AP users can help me here.    I am wanting to make sure my understanding on how to best use the Octopi is accurate.  When I need to make adjustments should I :use Method A or Method B

 

Method A:

  • loosen all 4 100 TPI screws (o-ring) screws
  • then make the appropriate changes to the 200 TPI screws at the appropriate locations
  • then tighten all 4  100 TPI screws

 

Method B:

  • loosen 2 100 TPI (o-ring) screws at the locations that need to be adjusted
  • then make the appropriate changes to the 200 TPI screws at the appropriate locations
  • then tighten all 2  100 TPI screws

 

I was playing with the Octopi last night, using Method B and the tilt just kept bouncing around and then it dawned on me that I should probably use Method A.    So I just want to make sure is Method A the best approach?

 

thanks in advance for any response!!!



#2 drmikevt

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Posted 30 May 2024 - 11:33 AM

I use an Octopi.  This doesn't really answer your question but what I've found is that it is best used by only 'pushing' the camera away from the scope and not trying to both pull and push.  

 

I think it is easiest to start with all of the screws 'zeroed' where the Octopi is in its absolute shortest configuration.  Then, push the corners (or sides) away from the scope as needed until you are flat and at the right distance.  When doing this, you should really only need to loosen the screws you are working on.  Using a program like Hocus Focus Aberration inspector, it should go quickly and predictably.  

 

Trying to shorten the distance is more difficult since you need to use all 4 screws.  But, and this is on the website, generally you want to avoid loosening all 4 screws at the same time since that will completely disengage the two plates from each other and is likely to throw off whatever previous tilt you had dialed in.  

 

Also, don't forget to loosen the screws on the sides of the device, which are to lock down the centering, but will prevent the device from pushing and pulling freely.  


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#3 belbakri

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Posted 30 May 2024 - 12:47 PM

Mike,  

 thanks for the info.  I never did loose the centering screws on the side  or even check to see if they were loose.  I  will makes sure they are loose.   I like your idea of just moving the camera in one direction.

thanks

Brent



#4 Fegato

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Posted 31 May 2024 - 09:22 AM

I use an Octopi with a RASA 11 and ASi2400MC Pro.  Keith has the following on his website "tips and tricks"

 

The standard screw set comes with a 200 tpi push screw and a 100 tpi pull screw(red o-ring). The red o-rings are just dust seals as the holes they pass through are oversized so the screw can pivot when at a slight angle. When you adjust the screw set, always release the thinner pull screw(red o-ring) and then adjust the larger push screw and then snug the pull screw (red o-ring) lightly. The reason for doing this is that with precision screws, the threads are smaller and they will strip out easier. When turning a screw, it has only about 1/6th of the ability to resist stripping as it has while static so by adjusting the screw sets in this order will lessen the chance that thing will go wrong. Here are the torque ratings, divide the in lb by 12 for foot pounds.
100 tpi 650 in lbs static 110 in lbs dynamic
200 tpi 339 in lbs static 56 in lbs dynamic

The 100 tpi screws on the sides are lateral adjusters and locks so that once you get the interface adjusted how you want, then you can slowly snug these up to help hold everything solid. While adjusting the interface keep the lateral screws a bit loose so the clamp ring can move by them easily. If you need to use the lateral screws to center the light cone then tighten the screw or 2 screws to nudge the camera over where you need it to be before snugging up the other 2 screws.

 

I tried to follow this method, but I find it difficult to know when the screws are "snug". Some of mine are stiffer than others even when loose, so it's quite tricky to know where they are.  So what I tend to to do now is loosen the one that needs loosening, and then tighten the other of the pair (pushing or pulling depending which way I'm going), and I always turn the 200tpi screw double the other one. I'm sure I over or under tighten some of them sometimes, but I do get the right result in the end!  I also always forget about the lateral screws, but should try and remember... 

 

 Mike - I would have thought your method would end up stripping the screws? As you push out, the pull screws are acting against the push? (and / or like I've seen on mine - you'll see some nice gouges in the plate underneath where the push screws are forcing their way into the metal!)



#5 belbakri

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Posted 31 May 2024 - 11:27 AM

Thanks Robin.... I did see this and one of my push screws are tight by nature so I do need to pay attention.


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#6 drmikevt

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Posted 31 May 2024 - 12:03 PM

 Mike - I would have thought your method would end up stripping the screws? As you push out, the pull screws are acting against the push? (and / or like I've seen on mine - you'll see some nice gouges in the plate underneath where the push screws are forcing their way into the metal!)

Yes, sorry if I wasn't clear enough.  Of course we need to loosen the pull screws in order to adjust the push screw, and then tighten back down.  I did not mean to only use the push screws by themselves, but I guess that's what I said.  ooops


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#7 ChrisWhite

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Posted 01 June 2024 - 09:39 AM

The best way to do this is to start with about 1mm of spacing.  Just zero it out, and turn all of the fine thread screws an equal amount.  They are very precise and distance is repeatable, so count how many rotations you do, and apply that equally to all corners.  Then lightly snug the locking screws.  Run your analysis (single frame or hyperbolic curve or NINA or visual... whatever) and determine which corner is the worst. 

 

I recommend that you only try to fix one corner at a time.  Always go for the worst one.  Once you have found the worst corner, loosen the lock screw as well as the lock screw for the corner diagonally from that one.  Leave the other two corners lock screws lightly snug.  You need to loosen the locks on the two opposite corners where you are working.  If you move one of those corners out, you are applying an inverse movement on the diagonally opposite corner... so it needs to be able to move in.

 

So if you turn one of the fine thread tilt screws clockwise 1/4 turn, you need to turn the diagonally opposite fine thread screw 1/4 turn counter clockwise.  You are basically pivoting the plate on the diagonal between the two locked corners.  Then lightly snug those two locking screws down and repeat your analysis.

 

If a fine thread screw is tight and does not easily turn.. dont force it.  you need to loosen the remaining locking screws slightly.  Sometimes only 1/8 of a turn is all you need.  There is something binding and you need to relax the force.  Dont loosen it enough so the plate begins to float.  The Axial design of the current Octopi version is less likely to bind than the original version with the radial arrangement of screws.   If you loosen the screws so much that the plate can float, you run the risk of it sagging into an undesirable position when you lock things down. If you do accidentally do this, point at the zenith so gravity pulls evenly on the device and gently snug the locks back down to pickup where you left off.  It might be better to do all of your adjusting while pointing up, however with a refractor its not convenient to reach the adjustments, so I generally aim north and have a camp chair behind the scope to sit in. 

 

The key with all of this is to move slowly and be gentle with the screws. 

 

EDIT-  And dont forget to loosen the screws on the sides of the Octopi, as mike mentioned above.

 

EDIT 2-  When you need to make a backspacing adjustment, which is an equal adjustment to all corners... point at the zenith like described above, let gravity be your friend while adding or removing spacing. 


Edited by ChrisWhite, 01 June 2024 - 09:42 AM.


#8 belbakri

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Posted 01 June 2024 - 12:30 PM

Chris, thanks for your explanation.   I think I have it figured out now with all the replies... appreciate all the feedback!!



#9 Fegato

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Posted 06 June 2024 - 10:47 AM

Just to add to (correct) my comment above...

 

I've had my whole rig apart, as I had to remove my RASA 11 corrector plate in order to tighten up the lens group which had come loose, and remove my camera adapter. As part of this I took my camera out of the Octopi and had a proper play with it. It made me realise that the screws aren't stiff at all, just one a little bit more so than the others, and that I had just overtightened everything. I have some nice divots in the metal underneath both sets! My camera was definitely off centre too, so I've got the lateral screws in a much better place for starting too.

 

Anyway, it's a solid thing, and has survived the abuse I've given it. I should find it somewhat easier to know where I am from now on. Moral is - don't be impatient (like I was). Take your time on a workbench to understand how this device works and feels, so it is nicely prepared and ready to go. Exactly as Chris says really!



#10 belbakri

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Posted 06 June 2024 - 11:35 AM

Hey Robin , after reading all the responses, I did tear the device apart and set things to zero and tried the other night. Got close then things got messed up.  It's hard to judge when one of the crews it tight. It's tight all the time even when the device is

loose so I just have to be patient and try again :) 




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