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Help installing Pegasus FocusCube 2 on Esprit 100

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#26 F-Astro

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Posted 04 August 2020 - 06:24 PM

Andrew,

 

I found the instructions for the Esprit on the Pegasus site confusing to put it nicely. After trying to follow them, it dawned on me that there is only one way for this thing to attach. First, remove the finder show, will make your life easier. Next I attached the bushing to the shaft with the two grub screws as the instructions dictate.  I then loosely attached the focuser to the bracket with the 4 short screws they sent so the focuser could mate with the Esprit shaft. I then removed the Esprit focus screws they said to remove and used the longest bolts Pegasus sent and attached it as shown in photo. Then tightened the grub screws onto the shaft. It appears that the bushing could have been longer, but there was enough of the shaft to attach to. I then tightened the 4 screws that hold the focuser onto the bracket and then connected to computer to test. It seems to work fine.

 

Hope this helps. If you have any more questions, let me know.

 

Fran

 

 

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#27 Lead_Weight

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Posted 04 August 2020 - 06:39 PM

Good to know, I'm going to redo this later tonight or tomorrow with a new determination. I did try exactly this, but I swear it seemed like the grub screws would not attach to the motor shaft. It looked too short to me, and I had it bolted down in the corners, so things should have been in the right position. I had also put the coupler on the Esprit focuser as far over as I could and still access the hex key grub screw on it. 

 

Anyhow, I'll give it another try and see if I can't get some success this time.



#28 njrusty

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Posted 27 August 2020 - 10:20 AM

Soooo...it appears in Sputnik photo of 8/4/20 he is bolting to the outer holes of the Esprit 120ED focuser holes (?) ...correct?



#29 F-Astro

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Posted 27 August 2020 - 06:46 PM

I have the Esprit 100, but yes to the outer holes. Pretty sure that was what Pagasus said to do and for the 100 was correct. Doesn’t really matter which ones you bolt to; whichever ones line up and allow you to reach the focus shaft. 



#30 SimonMiller

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Posted 24 November 2020 - 01:46 PM

I have the Esprit 100, but yes to the outer holes. Pretty sure that was what Pegasus said to do and for the 100 was correct. Doesn’t really matter which ones you bolt to; whichever ones line up and allow you to reach the focus shaft. 

The instructions from SkyWatcher:

 

The only screws that should be removed are the large mounting screws but they need to be replaced in order to keep the block mounted correctly.

 

I think it does matter. You have to follow the Pegasus instructions and replace only the outer bolts. This will clamp the assembly down and also hold the bracket.

 

The inner bolts hold the assembly away from the rack and pinion, whilst the outer bolts pull the assembly towards the main body.

 

One pair acts in tension against the other (Yin and Yang), so the registration is kept if you only remove and replace one set at a time.

 

NB the two screws do NOT clamp the assembly, rather they provide separation. If you replace them with bolts, then you will not tension the rack and pinion and it will only be tensioned on the other side when using bolts to clamp the bracket.

 

Grub screws and ordinary screws work differently!

 

Simon


Edited by SimonMiller, 25 November 2020 - 08:29 AM.


#31 AdamJ

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Posted 24 November 2020 - 03:38 PM

The correct way and how I do it is to use the outer two holes. The inner two control the mesh and are needed.

#32 AdamJ

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Posted 24 November 2020 - 03:39 PM

The correct way and how I do it is to use the outer two holes. The inner two control the mesh and are needed.

#33 CrookedEyes

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Posted 28 November 2020 - 06:06 PM

I just installed the Pegasus Astro V2 onto my Esprit 100. I also had issues when following the instructions to use the outermost holes. It seemed as though the grub screws within the coupler were having a very hard being able to grip onto both the motor shaft and the focuser shaft. At one time during my installation, I had the coupler on the shafts and tightened the grub screws down and it must have been very close to the end of the focuser shaft because it ended up slipping off of the tip and marring the shaft a little. This made me quite angry and frustrated. This could be simply solved by shipping a little longer coupler with the PA FCv2. I have been looking to having one made at work to add a little length to the coupler and reposition the grub screw holes to grip more of each shaft. At any rate, eventually, I got it to work, utilizing the outer holes per the installation instructions. I can't imagine that much of either the focuser or motor shaft is being gripped though. Now I am having a hard time getting the auto focus routine to run correctly and completely in NINA. Hopefully I get it figured out tonight when I get back out there to image. 


Edited by CrookedEyes, 28 November 2020 - 06:06 PM.


#34 SimonMiller

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Posted 29 November 2020 - 12:59 PM

I just installed the Pegasus Astro V2 onto my Esprit 100. I also had issues when following the instructions to use the outermost holes. It seemed as though the grub screws within the coupler were having a very hard being able to grip onto both the motor shaft and the focuser shaft. At one time during my installation, I had the coupler on the shafts and tightened the grub screws down and it must have been very close to the end of the focuser shaft because it ended up slipping off of the tip and marring the shaft a little. This made me quite angry and frustrated. This could be simply solved by shipping a little longer coupler with the PA FCv2. I have been looking to having one made at work to add a little length to the coupler and reposition the grub screw holes to grip more of each shaft. At any rate, eventually, I got it to work, utilizing the outer holes per the installation instructions. I can't imagine that much of either the focuser or motor shaft is being gripped though. Now I am having a hard time getting the auto focus routine to run correctly and completely in NINA. Hopefully I get it figured out tonight when I get back out there to image. 

I just finished installing a Pegasus Astro V2 on my Esprit 100.

 

I have installed it quickly yesterday, but this afternoon I did it again knowing a bit more about how things work. My first install was with OTA on the mount. Second was with OTA on a table and the focus rack removed. Otherwise access to connect, adjust and verify is very difficult.

 

You have to use the two outer holes on the base of the focuser. I found it easiest to remove all four outer screws so that the rack can be removed. The inner screws determine the setup, so I didn’t touch them. Some users have used the inner screws - the mounting screws will not work the same in these holes. The bracket I have has wide slots and thin gaps between the slots. This means there is freedom to insert the screws without needing them to be centred. I used this to get a secure grip on the two shafts.

 

The Pegasus instructions say to remove the coarse knob and use the outer access hole to tighten the grub screw onto the focuser shaft. I started like that but found there wasn’t enough shaft to grip onto. I used the inner access hole to get a better grip on the shaft, with one grub screw on the D and one on the back.

 

When the screws are tightened, I found it best to pull the coupler out slightly and to be sure that it is centred. It is worth checking this is centred so that it doesn’t wobble. Access to the grub screw is a bit tight because you want the grub screw to be as far out as possible.

 

The bolts for the motor can be kept loose so that the bracket can be held over the focuser. It is much easier to have the bottom of the focuser off the scope. The order I setup everything was:

  1. ​Connect the 6mm coupler to the scope shaft;
  2. Hold the bracket over the base of the focuser. You should have access for washer and 30mm screw;
  3. Attach the 5mm coupler to the motor, holding the bracket against the focuser base;
  4. Adjust until the coupling is inline and not wobbling;
  5. With the bracket on the base, slide the motor down and tighten the motor screws;
  6. Check the operation of the motor. It should be move smoothly and almost silently;
  7. Undo the 5mm coupling and separate the motor from the shaft;
  8. Attach the focuser base,  back on the focuser and hold the base whilst tightening the 2 SW bolts;
  9. Using 2x washer and the provided 2x 30mm screws, loosely attach the base/bracket to focuser;
  10. Remove one of the grub screws on the 5mm coupling and move the motor shaft into the coupling;
  11. The motor and coupling can be pushed together so that the 30mm screws are pressed against the bracket;
  12. There will be a gap between the base of the motor and the 5mm coupling (4mm);
  13. You will notice that the shaft of the motor through the grub screw hole;
  14. Check the operation of the motor. It should be move smoothly and almost silently;

The coupling seems like it is too short, the third slot in the bracket seems too close and there doesn’t seem enough shaft to grip onto but it does all work out.  For me the main thing was to not attach the coupling to the focus using the first grub screw access. The shaft was only half under the grub screw. Using the second access hole allows the coupling to be further onto the shaft. Access to do it up is difficult and. Could have done with a ball headed Allen key. When the coupling is attached, it should rotate freely and the back of the coupling should clear the bearing. The motor shaft does not need to push hard against the coupling because it only needs to allow the grub screw to be fully over the shaft and the grub screws are not right at the tip of the shaft. The four grub screws on the shaft have to be tight against the shaft and be over the brass shaft. Trying to grip right at the end simply doesn’t work and it works loose. There are two grub screws on the focus knobs. Undoing both allows the mechanism to be removed. They both need to be in place and tight. When it is all assembled (my second attempt) and back on the mount, the operation is nearly silent and the motor obviously transfers through the coupling without straining. The shafts don’t wobble and there is no vibration. The reason I assembled it a second time s because after I had calibrated and started to test it, the coupling became detached and there was 0.5cm of free play. When it is properly adjusted and moving between focus points the micro and mini knobs should rotate when the motor is driving them. When it is stationary, the mini knob should feel firm and there should be almost no play in the micro knob.

 

I set the start at 0.5cm and the end at 8cm. This is also exactly 0 and 30,000 steps. I have the focuser on the LHS looking onto the Esprit 100, so I have reverse selected for the motor.  I also have the limits enabled at 0 and 30,000.

 For now, I just have a start, middle and end points defined. I have not configured backlash. I did experiment with the temperature probe e.g. set the shift to a high figure and see it move Every 15 seconds. I also tried the ASCOM driver and focuser works as expected in APT and NINA.


Edited by SimonMiller, 29 November 2020 - 01:05 PM.


#35 CrookedEyes

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Posted 30 November 2020 - 03:38 PM

SimonMiller,

 

The way you tightened the grub screws onto the shafts is pretty much exactly how I did it as well...using the inner access hole to tighten the grub screws and utilizing the outer focuser holes for mounting the bracket per the instructions. It was a tight squeeze but it worked! It works as it should...quietly, no vibration, and no wobble. Your thorough installation explanation will definitely help others with FocusCube/Esprit installation. I do agree with you that the coupler is a bit too short. It is true that as long as the full surface of the tip of the grub screw is entirely on each shaft, with one on the flat and one on the back of each shaft, that it should be fine. I do think that it would be beneficial to have a little bit of length added to it. That or a bracket with slots shifted slightly to allow proper alignment and to give users the added comfort of knowing that the grub screws have a good chunk of each shaft, without bottoming the coupler out to the motor or focuser and without bottoming out the shaft within the coupler. I see a lot of people having difficulty with it. While some of us are able to figure it out, others may not...or they may not feel comfortable with the amount of each shaft that is captured by the grub screws. Some minor adjustments could be made to the bracket or coupler to assist in ease of installation. Thanks for the thorough explanation!



#36 SimonMiller

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Posted 01 December 2020 - 07:49 PM

Thanks for the thorough explanation!

Your welcome. I sent Pegasus an email. After studying their bracket, I reached the conclusion that they should enlarge the hole for the motor in the bracket to be slightly bigger than the diameter of the coupling. Since the bracket is thicker than the "bars" next to the slots, it provides the flexibility to adjust the coupler (into the bracket) so that there is always an open slot whilst still being able to use the grub screws. Providing two lengths of couplings (there are 6 of them) would also solve the problem but it comes at probably a greater cost than simply modifying the bracket to have a bigger hole.

 

The instructions for installing a Focus Cube on an ESPRIT 100 suggest using the outer grub screw hole but the shaft isn't 100% accessible. Their own 2nd photo suggests they thought the same and they used the inner hole. Pushing the Cube onto the bracket shows only a small gap in their photos and in practice there will be about 4-5mm of "exposed" shaft. That's OK, because it's only necessary to clamp on to the motor shaft 100% and that (is just about) possible. A grub screw needs to be screwed onto a shaft with 100% access to the shaft. It's only a problem if you are trying to clamp onto the tip of a shaft and where it has the potential to become loose.

 

In UK, RVO suggested leaving the micro/mini 10:1 focuser mechanism "off" as it is "fixed" and can no longer be manually rotated with the attached motor. With the rack and pinion there are bearings at each end anyway and the 10:1 operation doesn't affect the operation. There are two ways to look at it: the motor has to move the telescope and also "force" the micro knob to rotate which is an "extra load" on the motor. Equally the 10:1 reduction acts as a "brake" on the focuser and provides additional resistance to the focuser moving when pointed at the Zenith. The Pegasus instructions don't show it being necessary to remove it but they also don't say why it needs to be retained. I followed RVO's advice but replaced it with the Mini knob (that is removed to add the motor) so that there is no additional resistance but I can also see it moving.

 

So with a working Pegasus focuser... how do you determine how much backlash there is with the internal gears and/or your mount's focus mechanism? They suggest 30-40, but it may be dependent on the mount as well? There must be an established method to do this for any mechanical system? If you set it too high does it matter e.g. the motor, when reversing direction, moves the backlash amount and then forwards by the same backlash amount in the opposite direction to "load" the gears? 

 

Also, did I understand correctly that the temperature compensation and the backlash is programmed into the motor unit e.g. when they are set, they are stored in the motor "firmware" so that another application doesn't need to control this function? Doing this for temperature compensation seems a good idea unless applications like APT or NINA can easily do this (and so avoid movements during the taking of Subs)?


Edited by SimonMiller, 02 December 2020 - 08:17 AM.


#37 Duckman

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Posted 11 January 2021 - 11:21 PM

PTL! LOL. I'm glad I found these instructions. Only took me about 20 min or so. This thing s sweet! Works like a champ. Now I'll have to figure out the backlash settings. Anyone have a SW 120 Esprit? Should be fairly similar.

 

Only thing I can see that could be a problem is keeping an eye on those two set screws that hold the shaft.



#38 Domer

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Posted 13 January 2021 - 01:11 PM

Thanks to everyone who contributed to this thread - it was immensely helpful to me as I just received my Esprit 100 yesterday and was able to avoid a lot of headaches and cussing because if the information provided here.  That's not to say that I didn't encounter any problems - I did -  but knowing what the workarounds were in advance saved me a lot of time and trouble.

 

The Pegasus instructions say to remove the coarse knob and use the outer access hole to tighten the grub screw onto the focuser shaft. I started like that but found there wasn’t enough shaft to grip onto. I used the inner access hole to get a better grip on the shaft, with one grub screw on the D and one on the back.

 

I was actually able to use the outer hole to tighten the grub screw onto the focuser shaft.  I just aligned it such that the screw was as far inward as possible while still allowing an access for an Allen wrench to tighten it down.  I think that made the rest of the installation a bit easier as more of the coupler was available for mounting onto the motor shaft.

 

But I have another question for all of you who have this same configuration - how do you transport the telescope now?  With the Focus Cube attached, it no longer fits into the SkyWatcher case, right?  And I don't think anyone wants to go through the hassle of detaching and re-attaching the Focus Cube every time the telescope needs to be transported.  At least, there appears to be no easy way to do that.




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