Adding Weight to the Primary End of a Newt.

[Moonshane]

Hi all

I am struggling to retain balance when using the dob at low angles.

This was slightly the case last night with the comet but it will be even worse now I have a 35mm Panoptic.

My proposed solution (in my mind!) was that I could remove the primary, add a bolt through the hole in the back of the outer cell section (where you would normally put a fan) and then bolt a 1KG dumbbell weight I have to the back end of this. A pic of my primary cell is show below.

My concern is that this may stress the cell (although it's very thick gauge metal) and create problems with the primary.

Does anyone have any suggestions as to how I can add a little weight at the primary end without any major mods or confirm whether my suggested approach would create any problems - or be likely to? I am thinking of an exchange for a 9 point cell in the future. Is this likely to be heavier and worth doing? This may well solve my problem.....

Thanks

Shane

[John]

I think your fears about stressing the mirror cell are well founded - while it won't break the cell it could cause collimation issues as you move the scope about.

I had the same problem with my 12" Meade Lightbridge and solved it by adding a sliding weight assembly to the outside of the lower tube section that was actually intended for SCT's. With that I could use even my Nagler 31mm and keep things in good balance.

Others have adopted simpler methods such as stapping jogging weights or even a bottle filled with sand to the lower part of the scope tube.

The Orion Optics 10" that I have now has the opposite problem ironically - it's really tail heavy !.

Here is a pic of my 12" LB - you can just see the counterbalance setup on top of the lower tube assembly:

[haitch]

Ikea sell magnetic kitchen knife holders with really powerful magnets pretty cheap.

I managed to hang a 1.8kg weight off the back of my dob on one (2 would have been more stable though)

[Moonshane]

brilliant guys! Thanks for this. with a combination of John's sliding weight system and Haith's IKEA magnetic knife holder - I have a couple of these coincidentally - waiting to be fitted to my kitchen units I reckon I'll have a better and adjustable system - cheers!

[Moonshane]

I've done some more thinking about this. The balance is not massively out and I reckon I will do one of the following, all of which avoid drilling the tube (which surprisingly I think is aluminium on the basis it's not magnetic).

- Buy another tube ring to add to the bottom end. That way I'll have two extras and can sell then as a pair if needed, it will spread the weight more evenly, it will look 'neater'.

- Add some of the sticky lead weights they balance wheels with to the inside of the tube. I bet I could scrounge a few when I next buy a tyre. I could adopt the same principle with some rolled up lead flashings (I bet I have some in the shed) with a hole drilled through and then a longer version of the end trim bolts to hold in place. This will be the cheapest option and if I use an even amount on each of the three bolts it would probably work.

This is an advantage of the OO UK dobsonian base as you can slide the tube back and forth to balance too, giving a few more options.

On the 9 point mirror cells, does anyone know if they are worth the £90 to exchange please?

Cheers!

Shane