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Auto focus choice


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Having used both EAF and Sesto senso (and Moonlite) on multiple scopes.

ZWO EAF works well, as long as one of the ZWO choice of mounting plates fits your scope, or you adapt a ZWO supplied one. Backlash seems good, accuracy seems good, undecided about load handling.

Sesto senso 'can' be fine but suffers from it's mounting method. The attachment point being the outside of the focuser train which is not necessarily concentric with the focuser shaft. If the focuser shaft and focuser 'outer' are not concentric the Sesto senso will 'wobble'. Backlash seems to appear if 'wobble' is present, otherwise accuracy seems good, load handling seems good.

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34 minutes ago, VectorQuantity said:

Having used both EAF and Sesto senso (and Moonlite) on multiple scopes.

ZWO EAF works well, as long as one of the ZWO choice of mounting plates fits your scope, or you adapt a ZWO supplied one. Backlash seems good, accuracy seems good, undecided about load handling.

Sesto senso 'can' be fine but suffers from it's mounting method. The attachment point being the outside of the focuser train which is not necessarily concentric with the focuser shaft. If the focuser shaft and focuser 'outer' are not concentric the Sesto senso will 'wobble'. Backlash seems to appear if 'wobble' is present, otherwise accuracy seems good, load handling seems good.

Thanks, been looking through the reviews and noticed people complain about the backlash on the zwo, but wondering how much of that is the focuser itself and not the auto focuser, unless the new 5v version is better than the old 12v one. Just seems a waste spending nearly £100 more on the Sesto or Pegasus for little benefit. 

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I have the Eaf on both my WO ZS73 and my Altair 150edf.  They are very accurate when focussing in APT either manually (with a bhatinov mask) or using the APT Auto focus tool.  Even imaging near the Zenith I've never seen any slipping which is quite impressive on the 150edf as there's a lot of weight in the 3 inch focusser with extension tubes , focal reducer and camera fitted.  very easy to install too. 

Graeme

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2 hours ago, VectorQuantity said:

Having used both EAF and Sesto senso (and Moonlite) on multiple scopes.

ZWO EAF works well, as long as one of the ZWO choice of mounting plates fits your scope, or you adapt a ZWO supplied one. Backlash seems good, accuracy seems good, undecided about load handling.

Sesto senso 'can' be fine but suffers from it's mounting method. The attachment point being the outside of the focuser train which is not necessarily concentric with the focuser shaft. If the focuser shaft and focuser 'outer' are not concentric the Sesto senso will 'wobble'. Backlash seems to appear if 'wobble' is present, otherwise accuracy seems good, load handling seems good.

I have two Sesto Senso focusers for my two rigs and very happy with them (hence why I bought the 2nd one.

The first one was the version 1 and that came with a solid coupling (well several couplings to fit various focusers) and yes that does have to be aligned pretty accurately but I really did not find that difficult.
The second one I got is the V2 (so I guess the version you would get if buying new) and that has flexible couplings to allow for some mis-alignment. So they are flexible to allow for this mis-alignment but in a rotary direction have no flex and so are very accurate.

Personally I like the way they fit to the collar of the focusser where you removed the focusser knob and find it a real neat solution with no flex at all between the stepper motor and the focusser fine tune spindle so super accurate.

I think focusers that are on a right angle bracket can suffer from some flex and those using a timing belt can suffer backlash and flex. BUT, after saying that my thoughts are that so long as you attach the motor to the fine tuning knob or spindle then a few lost pulses of the stepper due to flex or backlash should really have no noticeable affect of the final focus as seen in the resulting images. If the motor is driving the rough focuser knob then it might be more prevalent.
So it you are doing the first scenario I guess any of these auto focusers would be just as good as the other.

Steve

 

Edited by teoria_del_big_bang
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6 minutes ago, teoria_del_big_bang said:

I have two Sesto Senso focusers for my two rigs and very happy with them (hence why I bought the 2nd one.

The first one was the version 1 and that came with a solid coupling (well several couplings to fit various focusers) and yes that does have to be aligned pretty accurately but I really did not find that difficult.
The second one I got is the V2 (so I guess the version you would get if buying new) and that has flexible couplings to allow for some mis-alignment. So they are flexible to allow for this mis-alignment but in a rotary direction have no flex and so are very accurate.

Personally I like the way they fit to the collar of the focusser where you removed the focusser knob and find it a real neat solution with no flex at all between the stepper motor and the focusser fine tune spindle so super accurate.

I think focusers that are on a right angle bracket can suffer from some flex and those using a timing belt can suffer backlash and flex. BUT, after saying that my thoughts are that so long as you attach the motor to the fine tuning know or spindle then a few lost pulses of the stepper due to flex or backlash should really have no noticeable affect of the final focus as seen in the resulting images. If the motor is driving the rough focuser knob then it might be more prevalent.
So it you are doing the first scenario I guess any of these auto focusers would be just as good as the other.

Steve

 

I've had a Sesto senso (V1) with flexible couplings fitted to three different WO scopes. The connection method to the outside of the focuser collar is a nice idea but assumes the focuser collar is concentric with the focuser shaft. On two of my WO's it was not concentrice and despite all attempts at alignment you could actually see the Sesto senso 'wobble' as it's stepper rotated. Luckily these scopes had relatively long focal lengths and a non-critical focus zone.

To just compare the EAF/Senso/WhateverFocuser by itself is difficult maybe impossible, leaving out the attachment method and step size other significant variables are the focus software and scope focal length (focus criticality) both of which have large effects on the focus outcome.

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19 minutes ago, VectorQuantity said:

I've had a Sesto senso (V1) with flexible couplings fitted to three different WO scopes. The connection method to the outside of the focuser collar is a nice idea but assumes the focuser collar is concentric with the focuser shaft. On two of my WO's it was not concentrice and despite all attempts at alignment you could actually see the Sesto senso 'wobble' as it's stepper rotated. Luckily these scopes had relatively long focal lengths and a non-critical focus zone.

To just compare the EAF/Senso/WhateverFocuser by itself is difficult maybe impossible, leaving out the attachment method and step size other significant variables are the focus software and scope focal length (focus criticality) both of which have large effects on the focus outcome.

Okay as I have only had the Sesto Sensos (well also I had a belt driven DSD very early on) then I have to accept what you say.
To be honest I never thought of the collar of the focusser not being concentric, I only thought the issue would be is if the fine focusser spindle was bent, which is easily done, I think I just assumed that within a few tens of microns they must be concentric, but yes if not then I guess it could be an issue with that type of attachment.
I guess I have been lucky then as mine must have been pretty much concentric (stock focusser on Esprit 100ED, Baader steeltrack on my RC6 and a stock focusser on my WO72) as I certainly have not had any wobble.

Also same really regarding the number of pulses you can afford to loose without seeing any visual determinable difference in focus of the image. Now hands up I have not yet used the RC6 in anger as this is still very new to me, but the 100ED you can achieve good focus in NINA , or EKOS, and then go 10 or 20 steps either side of that before you could see any real change to the actual focus, but as you say the focal length of the scope would affect this.

So I accept there could be issues with this mounting method.

Steve

Edited by teoria_del_big_bang
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43 minutes ago, teoria_del_big_bang said:

Okay as I have only had the Sesto Sensos (well also I had a belt driven DSD very early on) then I have to accept what you say.
To be honest I never thought of the collar of the focusser not being concentric, I only thought the issue would be is if the fine focusser spindle was bent, which is easily done, I think I just assumed that within a few tens of microns they must be concentric, but yes if not then I guess it could be an issue with that type of attachment.
I guess I have been lucky then as mine must have been pretty much concentric (stock focusser on Esprit 100ED, Baader steeltrack on my RC6 and a stock focusser on my WO72) as I certainly have not had any wobble.

Also same really regarding the number of pulses you can afford to loose without seeing any visual determinable difference in focus of the image. Now hands up I have not yet used the RC6 in anger as this is still very new to me, but the 100ED you can achieve good focus in NINA , or EKOS, and then go 10 or 20 steps either side of that before you could see any real change to the actual focus, but as you say the focal length of the scope would affect this.

So I accept there could be issues with this mounting method.

Steve

If it's of any help to anyone the approximate cricial focus zone (depth) for different F numbers for blue (470nm) which is the most sensitive is along the lines of: (the ratios should be correct even if absolute values don't tie up with your calcs)

F2, 4, 6, 8, 10 ,12

9, 36 ,82, 146, 229, 330 microns

This is just to give an idea of sensitivity to F number, in practice you'd want to place focus within the CFZ up to 10 times better than these figures.

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6 hours ago, VectorQuantity said:

The connection method to the outside of the focuser collar is a nice idea but assumes the focuser collar is concentric with the focuser shaft.

I might be mis-understanding something, but isn't the collar of the focuser also the outer for the bearings? I'm not quite sure how it cannot be concentric. I can understand 'wobble' if the focuser is slightly misaligned to the shaft - I have had to adjust mine once because of this - but the fault was entirely mine.

FWIW I have used 2 Sesto units on half a dozen scopes and they have been faultless. If I was buying another focuser I would get the same again.

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2 hours ago, Clarkey said:

I might be mis-understanding something, but isn't the collar of the focuser also the outer for the bearings? I'm not quite sure how it cannot be concentric. I can understand 'wobble' if the focuser is slightly misaligned to the shaft - I have had to adjust mine once because of this - but the fault was entirely mine.

FWIW I have used 2 Sesto units on half a dozen scopes and they have been faultless. If I was buying another focuser I would get the same again.

It's probably my poor description. The ID of the collar is the bearing surface. The OD isn't a bearing surface it just fits into the x1 section of the x1x10 focus knobs, although it should be concentric with the ID depending on the focuser it doesn't have to be. Yes on two of my scopes the 'wobble' means there must be a misalignment and I couldn't fix it, or at least I gave up trying to. On the third scope the same Sesto senso is perfect and has worked well for several years.

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2 hours ago, Anthonyexmouth said:

I guess what I really want to know is whats the extra £££ getting me on the Sesto/Pegasus over the zwo. 

Sesto senso Wifi, 12V so potentially better load handling (not 5V powered)

ZWO EAF 5V via USB lead, no 12V lead, integration with ASIAir. Adapters for SCT's. Add-on hand controller for standalone use without PC.

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23 hours ago, Anthonyexmouth said:

I guess what I really want to know is whats the extra £££ getting me on the Sesto/Pegasus over the zwo

Not a lot. Unless you are looking for something specific as stated above - both will work on most scopes.

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Some ZWO EAF focusers may have a flexible coupling fault.  You can attach the coupling but it's impossible to remove it. I bought one of these units and thought I had messed up somehow. Had to cut the coupling off. However, when changing my scope I took the EAF in to the supplier and asked them to install the focuser for me. They couldn't remove the coupler either and explained that the unit can have this fault, that they had encountered others and returned them for customers. It was returned to ZWO who said that the problem was due to a burr that was going around the shaft and suggested the cause was not tightening the screw sufficiently to hold it in place when the counterpart rotated. They repaired it without charge so there was no dispute over warranty.

Can't speak for Sesto or Pegasus.  Have a ZWO camera and it's great. The EAF I am not so sure about. 

 

Edited by woldsman
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3 hours ago, woldsman said:

Some ZWO EAF focusers have a flexible coupling fault.  You can attach the coupling but it's impossible to remove it. I bought one of these units and thought I had messed up somehow. Had to cut the coupling off. However, when changing my scope I took the EAF in to the supplier and asked them to install the focuser for me. They couldn't remove the coupler either and explained that the unit can have this fault, that they had encountered others and returned them for customers. They kindly offered to return mine but ZWO insisted on proof of purchase so I am now going back to the different supplier from whom I bought the EAF to get an exchange that way. So -3 for the EAF I'm afraid (-1 for letting faulty units leave the factory, -1 for not issuing a recall, and another -1 for not accepting the return which would have saved time and further cost). 

Can't speak for Sesto or Pegasus.  Have a ZWO camera and it's great. The EAF has not been great though. 

 

Not sure I understand this. The ZWO EAF couplers are tightened onto the shafts using grub screws, so do you mean the grub screws were tightened on too much that you couldn't get them off?

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I have two Sesto Senso 2 focusers, one on the 3.7" TS R&P of my TS 130mm photoline, the other on the 3" Feather Touch focuser on the ODK12. The only problem I had with either was down to a mismatch between firmware and software versions, they must both be the same, else calibration won't hold.

There have been no issues regarding out of square or misaligned shafts.

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On 12/06/2022 at 19:58, iantaylor2uk said:

Not sure I understand this. The ZWO EAF couplers are tightened onto the shafts using grub screws, so do you mean the grub screws were tightened on too much that you couldn't get them off?

No, it’s not grub screws. It’s the machining of the couplers - they slide on too tightly. Some batches may not have the correct tolerances but it is also possible that tightening the grub screws causes an issue with burrs.

Edited by woldsman
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On 12/06/2022 at 16:48, woldsman said:

Some ZWO EAF focusers have a flexible coupling fault.  You can attach the coupling but it's impossible to remove it. I bought one of these units and thought I had messed up somehow. Had to cut the coupling off.

 

I've go one of those as well - the 1st 12v version I bought. The pair of 5V EAFs both seem OK

Edited by iapa
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One less cable :) both support a ZWO cooled camera, filter wheel easily enough. 

Quick to optimise focus at start of session - of course needs a rough focus before first autofocus, after that, it just works - but I bring the OTA and accessories in when necessary, so no need to recalibrte

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17 hours ago, iapa said:

One less cable :) both support a ZWO cooled camera, filter wheel easily enough. 

Quick to optimise focus at start of session - of course needs a rough focus before first autofocus, after that, it just works - but I bring the OTA and accessories in when necessary, so no need to recalibrte

 

I really like the one cable solution but was worried it might be a huge compromise somewhere. I have a permanent setup so would hopefully need very little work after first setup. I think I'll give the zwo a go and save a few quid towards an optolong filter. 

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One setup I have is WO Redcat 51 + carry handle, DeepSkyDay EAF focus adapter, ASI Air Pro, ASI183MC-Pro, WO Slideguide, ASI174mm.

One power cable to the mount and one the the ASIAir.

Rough manual focus at first use, then just let the AAP manage everything.

If it need to come in, then grab the carry handle loosen bolts on mound ad carry it all in.

Redepoyment is reverse of a move plus balance check. 

Similar with an 8" SCT (I added a Losmandy dove tail), reducer, EAF, OAG. Hold by fixed dovetail and slide out.

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On 10/06/2022 at 22:21, VectorQuantity said:

Sesto senso Wifi, 12V so potentially better load handling (not 5V powered)

ZWO EAF 5V via USB lead, no 12V lead, integration with ASIAir. Adapters for SCT's. Add-on hand controller for standalone use without PC.

I had a Pegasus attached to my SCT, unfortunately the bracket bent which meant the belt was not tight to the pulley.

Suppose I'd not had the SCT sitting supported as well as I though, and the weight gradually bent the bracket.

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2 hours ago, Anthonyexmouth said:

I really like the one cable solution but was worried it might be a huge compromise somewhere. I have a permanent setup so would hopefully need very little work after first setup. I think I'll give the zwo a go and save a few quid towards an optolong filter. 

The one thing I would say I that you should use the recommended ZWO PSU for the ASI Air Pro, and separate power for the mount.

I have found that the power demand for imaging camera, guide camera, EAF, and dew strip (using Lynx Astro DC male to RCA adapter cable)  is easily met by the ZWO PSU.

Sometime ago I posed current draw for these, I'll try to find it.

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