Bresser Messier 8" Secondary Adjustment Knobs

[Pixies]

Hi,

My recently purchased 8" Dob has 3 small philips-type screws to adjust the secondary mirror. I am aware that some similar models (like the 10") have knurled knobs instead. In fact, the diagram on the cover of the manual for the 8" Dobsonian has them too. (See below)

FLO have confirmed that they cannot source these as spares. I have spoken to Bresser who say they do not supply them either. Bresser UK (Telescope House) confirmed this but say they are M4 screws.

Before I take one out to measure and try and find an alternative, has anyone here done this and can they suggest a suitable alternative? 

[johninderby]

The 10” uses M5x30mm screws. Just remove one and measure it.

I replaced the chrome knobs with these. All the UK places seem to be out of stock of the 30mm lengrh.

https://www.ebay.co.uk/itm/High-Thumbscrew-M5x30mm-Steel-Browned/274297199995?hash=item3fdd631d7b:g:WOcAAOSwOfxeYOam

Edited May 19, 2020 by johninderby

[Pixies]

M4, M5 - going to have to take one out and double-check. Thanks John

[Ricochet]

If I've found the right screws in my astro drawer, the 1st generation run of the Bresser 8" dob used M4x25mm round head screws for the secondary collimation bolts. I made my own thumbscrews from something like M4x40mm screws and some spare tyre valve caps. However, I've since had the secondary/spider replaced and I've not bothered changing them on that. You can do the screws up quite tightly with a screwdriver so that once it's in the right place the secondary doesn't move and recollimation isn't necessary. 

Edited May 19, 2020 by Ricochet