Problem with skywatcher 150/750 and cyck focuser. I can´t get focus

Sky-Watcher Black Diamond 150/750 Optolong L-Pro Focuser Filters
7 replies•294 views
Jandro.rm avatar
Jandro.rm avatar
Hello. I would like to know if anyone who has changed the focuser on this Newton has had focusing problems. In my case, when changing from an SV200 filter to an Lpro filter, I cannot focus for 150 focuser steps. The focusing shaft is fully inserted and stops. Am I doing something wrong?
Iosif Bodnariu avatar
Iosif Bodnariu avatar
Try to reduce at 30 steps.
Jandro.rm avatar
Jandro.rm avatar

 
Iosif Bodnariu:
Try to reduce at 30 steps.

Hi
the problem is not the steps, because when it´s stop the star is unfocused. So i need a couple of milimeters to get focus
Tony Gondola avatar
Tony Gondola avatar
If you are hitting the bottom of the focuser's range the only thig you can do is move the focal plane out by moving the primary closer to the secondary by a small amount or remove or change something in your imaging train so you can reduce the distance from the top of the focuser body to the sensor. If you are really close can also try moving the primary closer just by adjusting the collimation bolts the same amount inward. Newts are very flexible this way so don't be afraid to make changes if you need to.
Helpful
Jandro.rm avatar
Jandro.rm avatar
Tony Gondola:
If you are hitting the bottom of the focuser's range the only thig you can do is move the focal plane out by moving the primary closer to the secondary by a small amount or remove or change something in your imaging train so you can reduce the distance from the top of the focuser body to the sensor. If you are really close can also try moving the primary closer just by adjusting the collimation bolts the same amount inward. Newts are very flexible this way so don't be afraid to make changes if you need to.

Thanks. Great idea
andrea tasselli avatar
andrea tasselli avatar
If you are going to use a coma correct as you probably would the said corrector would push the focus out, sometimes considerably, depending on the specific of the coma corrector. The widely regarded SW 4-elements one will push it out by 20mm.
Peter Graf avatar
Peter Graf avatar
I'm also looking for a replacement for the stock Crayford focuser for my 150PDS, but all I found was for 8" and up. Even the customer support of a shop here in Germany was not 100% sure which focuser would fit the Skywatcher 6" to be able to get into focus. That's why I had given up the search again.
At least in this case, cyck says it would fit. And they also took a picture of it as a product image. ;-)
I keep my fingers crossed that you find a solution. For the price it looks quite sturdy and promising.
Supportive
Alex Nicholas avatar
Alex Nicholas avatar
I would be pushing the primary mirror further up the tube using the push screws on the back… That's your easiest option to get a 'few millimeters'… If it turns out that a few millimeteres is not enough, you may have to consider something like what I had to do to my 8" F/6 newt back in the day, and cut 1" (~25mm) off the bottom of the OTA, re-drill holes for the primary mirror cell, then re-mounting the cell, re-collimate, then your focus point will be 25mm further out than it was before. Problem solved…

As Andrea mentioned though - if you do not yet have a coma corrector in the light path, I would not resort to any drastic action yet, as they can significantly alter the focus point of the telescope.

Alex.
Helpful
Related discussions
Help Needed - RedCat 51 Gen III Focuser Issue
Hello all, Just bought my first scope - RedCat 51 Gen III. Unfortunately right out of the box, the focuser hits a hard stop right before the 10mm mark. I’ve read and understand that the advertised 30mm of travel is really only either 23mm or even 26m...
Focuser hard stop issue similar to author's focusing problem with Newton.
Jan 20, 2026
Focuser and planetary camera recommendations for Skywatcher 150p Virtuoso GTI?
Hello and welcome id like to ask everyone who have this telescope. Im originally a Seastar user but ever since its being told that the seastar itself cannot do planetary imaging or observing i purshued this big boy. Its also an ALT AZ telescope but i...
Asks about focuser recommendations for Skywatcher 150p, directly relevant Newton telescope.
Aug 26, 2025
Collimation Problems
Hello guys. I just acquired a Sky-Watcher 150/750 PDS Newtonian and I am new to the whole Newtonian thing, I watched videos and read articles about how to collimate and I follow through all the techniques (Cheshire eyepiece, collimation cap, laser co...
Same telescope model; focusing problems may relate to your corner distortion issue.
Sep 21, 2023
Focuser trouble when NINA starts
Hello, I’m new to NINA (was using ASIAIR before), I was able to connect and set everything and to perform two nights of imaging. Here is my issue, the last two times I turned all my equipment on, my focus was lost (I mean stars wereway out of focus, ...
Focuser trouble when starting imaging software, relates to focusing problems.
Sep 3, 2025