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SkyWatcher Electric Focus on Celestron NexStar 127 SLt

Guest LilRob

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Guest LilRob



First Post 


I am wondering if it is possible to use a skywatcher electric focus on my celestron nexstar 127


I am new but basiclly want to be able to control everyhting from my laptop 

i just prefer that 


i will from time to time use my own eye but mainly want to use a ccd (which i have on order but i know need a more control way to change the focus 


If that does not work do you have any suggestions 


Many Thanks in advance 



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Hi Rob and a warm welcome to EMS :)


Which mount is your scope on? You can add electronic focusers to most scopes as well as a range of other gear like filter wheels, cameras, guide scopes, etc.


But it all depends on the mount as to whether you can control the whole lot from a computer (which is very easy with the correct, compatible equipment).


Have a look at the ASCOM website meantime, and also download Stellarium. These will both be useful if your gear is up to remote control. :)


(It would also help to know what exactly you intend to take pictures of)

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Thank you for replying 


i have a celestron 127 slt nexstar


so far it s just out of the box 

i want to take pictures of planets for now 

but mainly using as a display as i seem to have difficulty using an eye piece 

so maybe some galaxies

i just want to explore but as using my laptop as main display i need a motor focus which i could control on my laptop as well 

done abit of research and it seems take you can jerry rig a skywatcher on a celestron to use which can be controlled by ascom 


just wondering if anyone has done this or know if it actually works 


Many Thanks 



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I think your mount is an alt/az mount - I can only see the Celestron 127 slt nexstar Maksutov cassegraine scope advertised on a computerised goto alt/az mount, which will be fine for imaging planets. It has a long focal length and high focal ratio. You would use a webcam for this - a dslr can be used but results would be limited and it's not really suitable.


When you look at planets through an eyepiece, you will notice they appear to "shimmer" or "wobble" due to the effects of the atmosphere. It's the same in all scopes and can't be avoided. However, it does settle for a very brief second or two occasionally. These are the moments you are trying to capture. To do that you run a webcam taking around 30 frames per second for a minute or two.


I'm sure the image can be seen on a computer preview screen - but to build a picture you would need to stack and align the frames using Registax (free) software. The program allows you to throw away poor frames and keep good frames to produce an image which can then be finished off using Photoshop (or similar) image processing software.


The requirements for imaging galaxies are different - you would use a dslr or astro ccd camera to take long exposures of 5mins or more. An alt/az mount isn't incapable of accurate enough tracking for this - you would require an Equatorial mount with good tracking and accurate polar alignment. You would also use a "fast" scope with a low focal ratio at f-5 or less.


One alternative is to get something like a Mallincam CCD video camera. Note that ccd cameras generally cost from £500 upwards - and that's for a basic model - they typical go into several thousand pounds.


I would suggest a good read of this book "Making Every Photon Count" by Steve Richards who writes a column in Sky at Night magazine - it's regarded as the imagers bible for most amateur astronomers. There's a lot more to astro imaging than meets the eye, but I hope this is of some help to you. :)




P.S. Please do come along to our Stargazing Live event on the 18th Jan at Wymeswold - It's amazing what you'll pick up from our members - especially the imagers. :)

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Thank you for the advise and i will have to see if i have work in the morning for the event but will look into 


i have usb camera and a another on order a celestron but do you know if you can jerry rig the skywatcher motor focus to the celestron 


i have aligned my telescope using a far away lamp post and got great views using the 25mm and  9mm lens provided and tested by usb camera it works i can see the picture it is not great quallity n=my new should be but as control i would like to control the focus as well on the laptop 


Many Thanks 

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The electric focuser will fit - but you may have to make a bracket to fit the focuser tube to support it. One or two of our chaps have done this with other scopes - I'll get you a link to one of them.....


Here you go: http://www.eastmidlandsstargazers.org.uk/topic/5901-fitting-skywatcher-autofocuser-to-starwave-80-ed/ :)


Note the comments further down the thread - in particular this one:


"Hitec astro dc focuser unit to the mount and usb hub, now fully controlled by ascom on the computer, works very well with APT software also"



And... Here's another thread where it's been adapted to an Sct focuser:



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Thank you just ordered the motor now thanks 


I hopefuly come tot he star party and give it a good test hopefully all my parts should arrive by then 

so would need a good test


going to the moon tonight though 


Many Thanks 

And Clear Skies 

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Hi Rob, if you have the 127 Refractor then the Skywatcher Motor Focuser will fit nicely. Dead easy to fit.



If you have the 127 Maksutov then the focuser is a knob on the rear and you will need a different motor focuser completely.

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