10" Dob Won't Focus ☹️

[adictd2dalite]

Hi everyone, I was hoping perhaps that somebody could help with this problem that I have. I bought a Bresser Messier 10" Dobsonian Reflector used but literally taken out once. It was too heavy for the old guy to lift. Anyway, I took it out for a blast and put in the 40mm 2" but it wouldn't focus although it felt like it might if the focuser would continue rising. I tried a few more eyepieces but still the same. I collimated it and tried again but no joy. Is it the case that I might need to purchase an extension piece for the focuser? Could it be that because it's the biggest telescope I've owned that the collimation needs to be more accurate than normal? I spent hours on this then eventually gave up. Thanks in advance if anyone can help I'd be grateful.

[John]

I've read about issues like this before with Bresser dobs. There should be an extension tube in between the focuser drawtube and the eyepiece I think. Does your scope have this ?

 

 

 

 

 

 

 

[Paul M]

My 10" Skywatcher Newtonian is optimised for imaging (to ensure adequate inward focuser travel) So to use it with eyepieces I need to use adapters that were supplied with the scope as standard. There is a 2" long adapter for 2" eyepieces and an adapter for 1.25" eyepieces that also provides 2" of extension.

So it sounds like you'll need something similar. I also bought one of these because 2" extension is too much usually:

https://www.firstlightoptics.com/adapters/astro-essentials-2-35mm-focus-extension-tube.html

 

[johninderby]

Bresser puts the focuser extension piece for visual use in the box with the base. Many don’t realise that the extenstion is hidden in the foam packing in the base box not with the OTA.

 

Edited March 6, 2021 by johninderby

[Pixies]

4 minutes ago, johninderby said:

Bresser puts the focuser extension piece for visual use in the box with the base. Many don’t realise that the extenstion is hidden in the foam packing in the base box not with the OTA.

Yep - they even had to make a comment on the website warning about this. I've spoken with someone who actually threw it out with the packing! They managed to get it out of the skip, though.

It's in the middle of the polystyrene packing that separated the circular parts of the dob base. 

 

[adictd2dalite]

Hi John thanks for your answer. Yeah that's exactly what it looks like. Should I buy an extension piece to fit in there somewhere?

[adictd2dalite]

Ah wait no, in my haste I lied. I don't have the extension bit. That piece I wasn't given. This should solve my problem if I can get hold of it perhaps? 

[johninderby]

1 minute ago, adictd2dalite said:

Hi John thanks for your answer. Yeah that's exactly what it looks like. Should I buy an extension piece to fit in there somewhere?

No you don’t need to buy anything else. Just fot the extenstion piece thst comes with the scope.

 

[johninderby]

5 minutes ago, adictd2dalite said:

Ah wait no, in my haste I lied. I don't have the extension bit. That piece I wasn't given. This should solve my problem if I can get hold of it perhaps? 

The extenstion tube is packed in the box that contains the base. Have a look through the styrafoam and you should find it inside one of the sheets of foam.
 

Of course if you bought it used then you might not have the boxes.

Bresser does sell the extension tubes though.

Edited March 7, 2021 by johninderby

[johninderby]

https://www.telescopehouse.com/BRESSER-Extension-Tube-37-5-mm-for-2-5-HEXAFOC.html

Edited March 7, 2021 by johninderby

[adictd2dalite]

I didn't get the box but I'll be on to the old boy tomorrow! He said there was some other bits and pieces in his lift so I'm guessing that's where it's at. Many thanks to everyone who helped with this especially John 🔭👍🏽☺️

[adictd2dalite]

Loft

[Pixies]

If the chap has lost it, you have options to get a replacement. John's link is for the 25mm version - but my 8" dob has a 35mm one. Perhaps the 10" is different?

In any case, it looks like a long waiting list for these. In the meantime, you could use a more standard 2" extender, like this one:

https://www.harrisontelescopes.co.uk/acatalog/bresser-35mm-extension.html#SID=627

 

[johninderby]

I updated my link to the 37mm version.

[adictd2dalite]

Thanks. Neil 

[adictd2dalite]

Got it 🙂 

[Ricochet]

48 minutes ago, adictd2dalite said:

Got it 🙂 

Great news. Just be aware that the 2" eyepiece clamp has a small hex grub screw in the side that you need to loosen before the clamp will unscrew. From memory it's either 2 or 2.5mm.