Fitting New Focusser to Dobsonian

[teoria_del_big_bang]

Hi,

I have just fitted a new dual speed Crayford to my Skywatch 8" Dobsonian.

Dual-Speed Low Profile 1.25/2" Crayford

It was a straightforward swap without the need for drilling or slotting holes. Only reservation I have is that the sides of the focusser are not profiled to fit exactly to the outer tube of the scope and eaves some very small gaps at either side.

I assume this is not really an issue but should I try to fit some side plates or fill in the gaps with silicon ?

[CraigT82]

Shouldn't be much of an issue unless there's a lot of ambient light where you observe from. Won't harm to plug it up with sealant though! 

Have you used it with this focusser yet? You might need a fair bit of extension to reach focus with eyepieces? 

Edit: just realised there is a built in extension tube on that focusser! 

[teoria_del_big_bang]

No not much ambient light around me and I was worried at first about that till I noticed the extension tube.

I know there are better focussers on the market but for the price this seems really nice and I really wanted the dual focus.

Steve

[CraigT82]

Ah you should be fine then! But just in case you could do a test next time you'e out, just observe something like M42 with the focusse as it is, then stick some electrical tape over the gaps and have another look to see if it makes any difference. If there's light leaking in it'll look a bit more faint and washed out. 

I'e had a focused like that before, only it was the revelation version... nice bit of kit! 

[fozzybear]

Steve,

You could try foam or neoprene to fill the gap rather than silicone to block out the light if at all any is coming in,even a bit of gorilla tape crude but practical as a short term solution whilst you fabricate a base plate as I know you are well capable of doing....

BTW I am still waiting for my son to print the part you created for me

regards

Andy

[teoria_del_big_bang]

7 hours ago, fozzybear said:

Steve,

You could try foam or neoprene to fill the gap rather than silicone to block out the light if at all any is coming in,even a bit of gorilla tape crude but practical as a short term solution whilst you fabricate a base plate as I know you are well capable of doing....

BTW I am still waiting for my son to print the part you created for me

regards

Andy

Andy, Good idea. I also thought it was probably something I could easily 3D print.

Funnily I was just thinking to PM you to see if the 3D printed parts worked or not 

Steve

[teoria_del_big_bang]

Thanks for the thought Andy. Two of these printed in about 25 minutes each did the trick. Might not have been needed but they finish it off nicely anyway.

 

 

Steve

[Uranium235]

I had exactly the same issue with the Baader Diamond Steeltrack - who on earth thought it was a good idea to make flat(ish) bases for these?

I ended up 3d printing a custom designed curve adaptor. Cost me a few quid, but it sorted out the light leaks, and evenly distributed the stresses that the focuser puts on the tube.

[fozzybear]

10 hours ago, teoria_del_big_bang said:

Thanks for the thought Andy. Two of these printed in about 25 minutes each did the trick. Might not have been needed but they finish it off nicely anyway.

 

 

Steve

you are so good at what you can do.

[Uranium235]

This is what I made:

PS: I've just discovered a really cool feature of Windows 10, it can render 3d STL files without additional software... pretty awesome!

[teoria_del_big_bang]

Neat 

I guess you are talking about 3D builder in windows ?