Can I put 8" focuser on 150p (6") Newtonian?

[MichaelBibby]

I have a (Bintel) dual speed focuser for my 8" and want to know if it can easily be transfered over to a Skywatcher 150p (6") Newtonian (which has the non dual speed focuser).

Here is my existing focuser (designed for a 230mm, 8" tube):



And here is a picture of the 150p non dual speed focuser:



It seems like Skywatcher is using an an 8" focuser on their 6" Newt's with a kind of adaptor plate. Is that correct?



If so it should be a simple matter of swapping them out. I don't have the 150p and would like to know if I can use my existing focuser before buying it. Any help appreciated.

[Robindonne]

The tubes radius will probably give a problem. But not impossible. You just need to 3d print a piece or fill the gap with other material. When there is an adapter plate already present it might work without printing or filling gaps.  Lets pray the mounting holes are the same 🙏🏼 

 

edit: the 8” focuser doesnt have an adapter plate. You have to get creative.

Edited November 7, 2022 by Robindonne

[MichaelBibby]

12 minutes ago, Robindonne said:

The tubes radius will probably give a problem. But not impossible. You just need to 3d print a piece or fill the gap with other material. When there is an adapter plate already present it might work without printing or filling gaps.  Lets pray the mounting holes are the same 🙏🏼 

 

edit: the 8” focuser doesnt have an adapter plate. You have to get creative.

So far as I can see, you can't actually get a 6" focuser. I have only seen 8 inch and 10 and 12 inch focusers. So this is probably how they are all done: use an 8" focuser with an adaptor plate to make it conform to the 6" tube. I just want to make sure before I pull the trigger on a purchase.

Yes, the mounting holes appear to be the same distance apart.

[Zermelo]

This is a U.S. site, but shows various backing plates, including 6", for a common (GSO) focuser:

https://agenaastro.com/replacement-base-reflector-crayford-focuser.html

[MichaelBibby]

I think I can answer my own question here: If you look at the skytwatcher's 200p (8") it does look like it uses the same focuser without the adaptor plate as the 6" has. So I should be able to use my 8" dual speed focuser on the 150p.

 

 

 

 

[MichaelBibby]

27 minutes ago, Zermelo said:

This is a U.S. site, but shows various backing plates, including 6", for a common (GSO) focuser:

https://agenaastro.com/replacement-base-reflector-crayford-focuser.html

Yeah, it just seems that if skywatcher were going to use different backing plates on their focuser then they wouldn't have another piece of metal between the focuser and the tube (what I'm calling here the 'adapter plate').

[MichaelBibby]

Just an update for anyone following this thread, or for future reference. Annoyingly, the screws holding the focuser to the tube on the skywatcher 150/750 are about 76mm apart, whereas my Dual speed focuser (and my other non Dual speed focuser on my other 8") the spacing is 70mm apart. Gah!


 

[Robindonne]

Is it possible to drill 2 new holes and move the secondary mirror a bit? Or make the old 4 a bit oval?

Edited November 8, 2022 by Robindonne

[MichaelBibby]

On 09/11/2022 at 04:13, Robindonne said:

Is it possible to drill 2 new holes and move the secondary mirror a bit? Or make the old 4 a bit oval?

Yes, I'll explore these options. It will all depend on just how usable the single speed focuser ends up being for astro. There is a simple mod for this focuser on Youtbe where you 'square off' the part of the tube where the focuser adjustment makes contact, which should make the focusing action smoother and more precise. Haven't received the OTA yet, but I'm hoping its not as bad as I assumed...

[NGC 1502]

It should be possible to sort this one way or another.  As the focuser mounting holes don’t match drill new ones but keeping the focuser lined up with the secondary mirror.  Fit appropriate washers to the bolts on the inside.  

Or you could enlarge the existing holes in the appropriate direction.  Instead of regular washers on the inside make shaped washers from thin sheet metal.  Use matt black paint. A bit fiddly but quite doable to leave a secure and neat job.

Edit-  Make sure debris or tools don’t fall on the optics by keeping the tube horizontal. Or you could remove them completely while working.  My own option would be to leave them in place, keep the tube horizontal on a bench and be careful.

If the focuser base is a different radius to the tube make appropriate spacer(s). Again fiddly but doable, take your time, think it through, don’t rush you will get there😊

Ed.

Edited November 10, 2022 by NGC 1502

[MichaelBibby]

Update:


Its actually possible to get a dual-speed upgrade kit for the Skywatcher single speed Crayford focuser. It looks like its only available from one UK seller though: https://www.365astronomy.com/lacerta-dual-speed-1-10-microfocus-upgrade-kit-for-skywatcher-crayford-focusers?search=Lacerta Dual Speed 1%3A10 Microfocus Upgrade Kit

Another option is to add a helical focuser. See here: https://www.cloudynights.com/topic/607401-35-alternative-to-a-2-speed-focuser/

[Spile]

9 hours ago, MichaelBibby said:

Update:


Its actually possible to get a dual-speed upgrade kit for the Skywatcher single speed Crayford focuser. It looks like its only available from one UK seller though: https://www.365astronomy.com/lacerta-dual-speed-1-10-microfocus-upgrade-kit-for-skywatcher-crayford-focusers?search=Lacerta Dual Speed 1%3A10 Microfocus Upgrade Kit

Another option is to add a helical focuser. See here: https://www.cloudynights.com/topic/607401-35-alternative-to-a-2-speed-focuser/

The Lacerta kit is a quality upgrade and it’s straightforward to install. It’s not cheap but I find it much easier to tweak focus than before. https://astro.catshill.com/lacerta/

[MichaelBibby]

1 hour ago, Spile said:

The Lacerta kit is a quality upgrade and it’s straightforward to install. It’s not cheap but I find it much easier to tweak focus than before. https://astro.catshill.com/lacerta/

 I just wish there was someone selling them here in Australia...

[Spile]

22 hours ago, MichaelBibby said:

 I just wish there was someone selling them here in Australia...

Is shipping from the Uk a possibility? I would have a word with Zoltan at 365.

[Geoff Barnes]

1 hour ago, Spile said:

Is shipping from the Uk a possibility? I would have a word with Zoltan at 365.

That was exactly what I did, ordered it from Zoltan at 365 with no problem at all, very good service and an excellent bit of kit.

[MichaelBibby]

Yes, I know, I was just complaining about the inconvenience of having to order it from an international seller, but really I'm grateful that I such a thing is even possible! I placed an order, glade this solution exists, surprised it took me so long to discover and that its not more widely known.