Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_solar_25_winners.thumb.jpg.fe4e711c64054f3c9486c752d0bcd6f2.jpg

Recommended Posts

Posted (edited)

I've been imaging with a SW ED80 for nearly a couple of years now, using a DSLR with the stock focusser with no issues.  I've heard stories of the stock focuser slipping for some people with heavier imaging equipment (mono camera + filter wheel) which is something I want to upgrade to in the not too distant future. 

Something I am also looking at getting soon is the Sesto Senso Autofocuser, and I was wondering, do these help with the prevention of focuser slippage at all? I want to avoid focuser upgrade if at all possible because I would rather invest the money into an Esprit which is a scope I want to buy at some point.

Edited by scitmon
  • Like 2

Share this post


Link to post
Share on other sites

I use a Sesto Senso on an Esprit 120ED, and previously on a Quattro reflector.  It works well.

However, I think you'll find that Crayford focus slip is not anything to do with how firmly you can hold the focus control, but all about the focuser tube slipping on the control shaft.  So a motor, per se, may not help.

The ultimate should be a quality rask and pinion, but that costs!  Also, I recently noticed that Primaluce Labs now do an integrated motor/focuser, the Essato...

https://www.primalucelab.com/astronomy/focusers/esatto-2-robotic-microfocuser.html

Tony

 

  • Thanks 1

Share this post


Link to post
Share on other sites
Posted (edited)

I have just taken delivery of one of these to fit to my new Esprit 100 but not yet fitted (maybe tonight I will find time) so cannot give any definite answer but my other auto focuser is very good at holding focuser position and that is with a timing belt.

However, even the best auto focuser will not really help with slop in the focuser so if the issue is just slippage then I would say it would help but if there is play or slop then it would not help.

Also @AKB makes a very good point about the slippage being due to the tube slipping due to overcomming the friction in the mechanism and really requiring a rack and pinion.

What I do like about the sesto is the lack of timing belt and the fact it fits a host of populat scopes right out of the box so when upgrading you can probably still use same auto focuser without buying any extra bits.

Steve

Edited by teoria_del_big_bang

Share this post


Link to post
Share on other sites
1 minute ago, teoria_del_big_bang said:

What I do like about the sesto is the lack of timing belt

Yes, but be very, very careful how you install it, taking great care to line up the rigid motor coupling with the fine focuser shaft.  It can be tricky.  This is the downside of a non-flexible connection.

 

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites
4 minutes ago, AKB said:

I think you'll find that Crayford focus slip is not anything to do with how firmly you can hold the focus control, but all about the focuser tube slipping on the control shaft.  So a motor, per se, may not help.

 

3 minutes ago, teoria_del_big_bang said:

However, even the best auto focuser will not really help with slop in the focuser so if the issue is just slippage then I would say it would help but if there is play or slop then it would not help.

 

 

I suspected this was the case,  I think my plans to get a mono camera with filters will have to wait til I can also buy an Esprit along with it.

  • Like 1

Share this post


Link to post
Share on other sites
Posted (edited)
48 minutes ago, AKB said:

Yes, but be very, very careful how you install it, taking great care to line up the rigid motor coupling with the fine focuser shaft.  It can be tricky.  This is the downside of a non-flexible connection.

 

Yes as an Engineer I was wondering how the alignments would be. Some sort of semi flexible coupling would be better, the type that has no radial movement but does allow for some slight misalignment of the two shafts. Maybe a bit much to ask for something so small.

Steve

Edited by teoria_del_big_bang

Share this post


Link to post
Share on other sites
Posted (edited)

I used my Sesto Senso on the stock focusser on my 200PDS and had problems with slippage. As mentioned it's slipping in the shaft. It could not take my 1600mm pro and filterwheel but I've heard other people's will take the weight without slippage. I switched it to a baader diamond steeltrack which is totally rock solid and solved all the issues.  

Edited by AbsolutelyN
  • Like 1

Share this post


Link to post
Share on other sites
2 hours ago, teoria_del_big_bang said:

Yes as an Engineer I was wondering how the alignments would be. Some sort of semi flexible coupling would be better, the type that has no radial movement but does allow for some slight misalignment of the two shafts. Maybe a bit much to ask for something so small.

Steve

Well, ZWO can do it.

  • Like 1

Share this post


Link to post
Share on other sites
1 minute ago, DaveS said:

Well, ZWO can do it.

Nice one.

Those are just the job. They are stock items from many places, used similar on a lot of things in the past. Its very easy to buy one with bores slightly smaller than required and open them out if the correct sizes not available off the shelf.

I would think the diameter is just too big for the Sesto, unfortunately.

 

Steve

Share this post


Link to post
Share on other sites

I actually had some of these from an old 3D printer, one of the bores was the wrong size but good enough to see if it would fit.

The diameter is actually okay, the small issue is that the grub screws are further apart than the slot that is there to gain access to them. But I think I could tighten the grub screws onto the focuser and the grub screw for the Sesto could still be tightened through the slot.

So I will order one with the right bores and try it.

Steve

Share this post


Link to post
Share on other sites
10 hours ago, scitmon said:

I've been imaging with a SW ED80 for nearly a couple of years now, using a DSLR with the stock focusser with no issues.  I've heard stories of the stock focuser slipping for some people with heavier imaging equipment (mono camera + filter wheel) which is something I want to upgrade to in the not too distant future. 

Something I am also looking at getting soon is the Sesto Senso Autofocuser, and I was wondering, do these help with the prevention of focuser slippage at all? I want to avoid focuser upgrade if at all possible because I would rather invest the money into an Esprit which is a scope I want to buy at some point.

Worth a watch.

 

  • Thanks 1

Share this post


Link to post
Share on other sites

I've had a Sesto Senso on my SW ED80 for a while and it's a great focus motor.  But as others have already highlighted:

  • No, it won't improve focuser slip, although there are a few things you can try to improve this
  • If you get one, be prepared for the very accurate alignment needed to install it properly.  It took me several attempts before I got it right, and every time it *looked* absolutely spot on.

Share this post


Link to post
Share on other sites

Regarding the flexible coupling talked about in earlier posts.

Regarding the diameter it will fit as these are between 19 and 20 mm diameter but they are a tad long. I nearly ordered one with the intention of shortening it slightly but actually I fit mine with the stock solid coupling very easily (well the 2nd attempt).

The first failure was my error as normal I blundered in without reading any instructions and fit it because it looked obvious how to do it.  The idea is simple as supplied are about 6 couplings all with one bore to fit the motor shaft and the other bores various diameters designed to fit popular focusers. Also provided with the couplers were around 8 small grub screws. You need 2 to tighten the coupling to the shaft, the others some of the others I assumed were to fit into tapped holes around the collar (there are 3 tapped holes that fit the grub screws and I assumed this was to aid alignment and that they were to be used as jacking holes together with the bigger screw to tighten the collar on the boss of the focuser.

image.png.c611953f8ee225d61a1ed382018a21e0.png

But using these grub screws caused the two shafts to be offset. Any slight offset and you can tell as when you manually use the focuser you can feel it go tight once per rev.  When I removed the grub screws and just tightened the main screw it all seemed to align perfectly.When I actually read the instructions the three extra grub screws are only required for certain focusers where the focuser collar size is smaller than the inner diameter of the sesto-senso and are used to retain an adapter bush (a bush not required for the 100ED so not sure what they look like but assume some sort of split ring). 

Now whether not all collars even on focussers that supposedly do not require this bush are exactly the same diameter for differing manufacturers or not but I guess they would only need to me fractions of a millimeter different to start causing some issues as the split collar on the sesto-senso will not clamp in same radial position for differing diameters.

I think maybe I was lucky and the collar on the 100ED is band on size. I think the omission in providing flexible couplings instead of solid ones is a big shame and probably lets down what looks otherwise to be a very neat auto focuser. Even if you had to buy the flexible couplings seperate or just state which size you require to fit your focuser.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.