Mods To My Dob

[Space Beagle]

Here's the latest little mods i've made to my modest little 200P based dob

This is the scope as it is now and with Basil looking mildly interested!

An attemp at a friction brake, kind of works, as long as not too much strain is put on it!

Magnetic counterweight, made out of a jewelers steel block with 3 neodymium magnets taped onto it. I've covered it with an old cleaning cloth to stop it marking the ota!

Nudge Knob, from b&q, held on with double sided sticky stuff. This really works well and makes moving the scope much easier!

Basil had lost interest by this time!

Rotating ring, as per Astro Baby's design. This ring is actually the one she used in her 'How To Guide'. Mel kindly sold it to me recently

[callisto]

I have just done the "Knob" mod myself

LOL, see you're dog turns its back on you like mine do

[Astro_Baby]

Ummm - I'm not sure why you need a ring rotater on a Dob - I assumed you were EQ mounting.

Thats a killer looking scope though

[simon84]

That rotating ring idea is fantastic. I agree not really needed on a dob but I happen to have a second set of rings for my 300P and if I ever EQ mount it again I will deffinitley be adding the third ring. Cheers Mel, absolute genius.

Nice scope though Doc, looks the business.

[Space Beagle]

Ah! But I do use the scope on a EQ5 too, well, sometimes!

I just liked the idea and it does seem to work on the dob mount too if you want to shift the position of the focuser / eyepiece a little with out upsetting the balance of the scope too much by twisting the ota in the rings and it sliping a little bit - especially if it's pointing at a high angle!

Doc

[Astro_Baby]

I;d think with a 300 it would be essential on an EQ - even shifting my 8" round in its rings was a nightmare before I bashed out the ring rotater/retainer. Now its a breeze. I cant imagine ho0w much huffing and puffing it would need to shift a 12" scope. Its not the weight really its trying to move a heavy weight so it doesnt force the mount out of alignment so its always like shifting lead weights that have to be treated like cut glass.

[simon84]

To be totally honest it was a nightmare. The only way to do it was to loosen the rings and then go to the primary mirror and turn the scope like a steering wheel. Complete PITA but it worked, the next goto target would always be a bit off though but with that third ring it would be an absolute breeze like you say. I'm not sure I'll ever EQ mount it again unless I get an EQ7 for my birthday next year.......

[Space Beagle]

Simon, I think you're getting slightly carried away! your 300P on an EQ7, it would be like being in the land of the giants!!

Think you'd have to mind your back too, eek!

I know I don't really need the ring when i'm using my 200P as a dob:o, I think I just like tweaking, he he!

Doc

[simon84]

It just got me thinking that the 300P on an EQ7 with a long enough losmandy dovetail would possibly make a viable imaging setup

[JohnR]

I'll be copying the nudge knob too

I have been using the rim of the opening of the tube to move it,but i've now had to put a dew shield on,so the knob will be a nice simple (and cheap) solution ,thank you

[Astro_Baby]

Simon - thats what I had to do with the 8" - go round the back of the scope and twist it but it always led sooner or later to either;

1/Mount shifts and alignment is wrecked

2/SCope shifts backwards and ruins the balance

3/ Both of the above

4/ On a couple of occasions the seam on the scope ripped the felt off the rings and jammed the whol thing up.

Adding the rotater meant the bottom two rings could be quite loose making rotating the scope easier. I just grabe the scope by its thrid ring and drag it round now. I was going to put a handle on the third ring but it wasnt necessary in use with an 8" that might be different with a bigger scope.

Large refelectors on EQs are a pain and in truth if the GoTO Dobs had been around when I bought I would have had one of those instead. My experiences of a 5-6" scope on an EQ led me to believe it would be easy but an 8" can be a handful, a 10" I suspect would be a mare and a 12" (for me at least) forget it.

[Moonshane]

I am loving the V design on the rocker box for the alt bearings. this had not occurred to me at all. I'll be nicking this design for a quick fix on an 8.5" f8 newt I bought recently.

It will allow me to create an adapter for my 12" OO UK dob base so I can star test the mirrors etc. and see what they can achieve.

I also use a 'locking ring' on my dob (actually three on my larger dob as they provide ballast at the tail end).