#1  
Old 15-10-2017, 02:01 PM
sungrazer's Avatar
sungrazer (Karen)
Registered User

sungrazer is offline
 
Join Date: Jan 2007
Location: Sydney
Posts: 154
focus motor

Hi All

Has anyone else had this problem and how did you solve it.

I have a new electric motor focus running with FCUSB. Works just fine (ish)
Connects fine - moves fine so while I monitor the focus between filters it's no problem.

BUT

I want to use it with SGP without monitoring it - the way SGP works is that it counts the MS between each filter and uses that to adjust (it doesn't adjust based on fwhm for example). You calibrate it - it remembers, then it runs it on each filter - so it is important that the travel distance is correct). My problem is that the distance it travels to do 20000 ms in forward is different to the distance it travels in reverse.


When the camera (qsi683)is attached to the ED80 it doesn't return to the original point with the same MS used. It comes out 20000 and goes back in 20000 but needs another 3000 ms to reach the same starting point.

I suspect it doesn't like the weight of the camera, because it looks like it runs correctly when the camera is not attached.

One thing I did already try was to grind the focus sleeve on the telescope flat to be sure it was running straight. Unfortunately, that made no difference.

You can see the gap in the photo attached.

Any ideas. Is this likely to happen on all telescopes? What do others do to get SGP to work with en electric focusser?

Thanks
Karen
Attached Thumbnails
Click for full-size image (ed80 electric focus problem.jpg)
198.5 KB32 views
Reply With Quote
  #2  
Old 15-10-2017, 04:58 PM
peter_4059's Avatar
peter_4059 (Peter)
Big Scopes are Cool

peter_4059 is offline
 
Join Date: Jun 2007
Location: Brisbane
Posts: 3,981
I think the problem is you have a DC motor/FCUSB rather than a stepper motor. The DC motor positioning is not as reliable as a stepper.

Also I don;t think the FCUSB has a driver that you can adjust settings? If it does is there a backlash setting you can change?
Reply With Quote
  #3  
Old 15-10-2017, 06:04 PM
sungrazer's Avatar
sungrazer (Karen)
Registered User

sungrazer is offline
 
Join Date: Jan 2007
Location: Sydney
Posts: 154
Quote:
Originally Posted by peter_4059 View Post
I think the problem is you have a DC motor/FCUSB rather than a stepper motor. The DC motor positioning is not as reliable as a stepper.

Also I don;t think the FCUSB has a driver that you can adjust settings? If it does is there a backlash setting you can change?
Hi

Yes you're right it's dc and not stepper. No it doesn't have any function to adjust it

what stepper motor would fit an ED80?

cheers
Karen
Reply With Quote
  #4  
Old 15-10-2017, 06:19 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is online now
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 6,660
Is controlling the focuser with SGP mandatory??
What issues are you currently having with good focus??
Reply With Quote
  #5  
Old 15-10-2017, 06:20 PM
peter_4059's Avatar
peter_4059 (Peter)
Big Scopes are Cool

peter_4059 is offline
 
Join Date: Jun 2007
Location: Brisbane
Posts: 3,981
Hi Karen, there is another link on IIS with a lot of stepper options. The only catch is you will also need a controller. There is a bit of cost in buying a commercial unit and there are cheaper arduino options if you are up for DIY. I have moonlite stepper motors and sharpsky controllers. I personally think the sharpsky option is quite good value as it comes with the controller which also has dew heater functionality.

Peter
Reply With Quote
  #6  
Old 15-10-2017, 06:33 PM
peter_4059's Avatar
peter_4059 (Peter)
Big Scopes are Cool

peter_4059 is offline
 
Join Date: Jun 2007
Location: Brisbane
Posts: 3,981
Here is a link the the thread:

http://www.iceinspace.com.au/forum/s...d.php?t=161926
Reply With Quote
  #7  
Old 15-10-2017, 06:44 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is online now
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 6,660
Peter,
Do you think these options will work with SGP??
Reply With Quote
  #8  
Old 15-10-2017, 06:51 PM
peter_4059's Avatar
peter_4059 (Peter)
Big Scopes are Cool

peter_4059 is offline
 
Join Date: Jun 2007
Location: Brisbane
Posts: 3,981
yes - I use SGP with Moonlite focusers/steppers and the Sharpsky controller. The key for SGP is that the stepper controller is ascom compliant. The catch with the ardunio options is whether the driver is ascom compliant, hence my recommendation to consider the sharpsky option. Dave (the developer of the sharpsky focuser) is an IIS member:

http://www.iceinspace.com.au/forum/s...light=sharpsky

The original version was a kit you built however Dave now offers a finished product that includes a dew heater. It is ascom compliant and fully computer controlled and it comes with the stepper motor housed in a metal box you can attach to the shaft of the focuser.
Reply With Quote
  #9  
Old 15-10-2017, 11:10 PM
sungrazer's Avatar
sungrazer (Karen)
Registered User

sungrazer is offline
 
Join Date: Jan 2007
Location: Sydney
Posts: 154
Quote:
Originally Posted by Merlin66 View Post
Is controlling the focuser with SGP mandatory??
What issues are you currently having with good focus??
the big issue is that i want to be asleep when it occurs
:-)
Reply With Quote
  #10  
Old 15-10-2017, 11:11 PM
sungrazer's Avatar
sungrazer (Karen)
Registered User

sungrazer is offline
 
Join Date: Jan 2007
Location: Sydney
Posts: 154
Quote:
Originally Posted by peter_4059 View Post
Hi Karen, there is another link on IIS with a lot of stepper options. The only catch is you will also need a controller. There is a bit of cost in buying a commercial unit and there are cheaper arduino options if you are up for DIY. I have moonlite stepper motors and sharpsky controllers. I personally think the sharpsky option is quite good value as it comes with the controller which also has dew heater functionality.

Peter
thanks
Ill check it out
Karen
Reply With Quote
  #11  
Old 17-10-2017, 05:49 AM
AstroApprentice (Jason)
Registered User

AstroApprentice is offline
 
Join Date: Dec 2015
Location: Melbourne, Australia
Posts: 200
USB focus

Not cheapest option, but includes temperature probe:
http://www.usb-foc.us/shop/product/u...d-set-6?page=2
Reply With Quote
  #12  
Old 17-10-2017, 11:31 PM
sungrazer's Avatar
sungrazer (Karen)
Registered User

sungrazer is offline
 
Join Date: Jan 2007
Location: Sydney
Posts: 154
Quote:
Originally Posted by AstroApprentice View Post
Not cheapest option, but includes temperature probe:
http://www.usb-foc.us/shop/product/u...d-set-6?page=2
thanks
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 11:38 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Interest Free Finance
Advertisement
Lunatico Astronomical
Advertisement
OzScopes Authorised Dealer
Advertisement
NexDome Observatories
Advertisement
SkyWatcher WiFi Adaptor
Advertisement
Bintel
Advertisement
SkyWatcher 2018 Catalogue
Advertisement
Astronomy and Electronics Centre
Advertisement