Keiths next scope modding plans

Way Hay! Welcome to the Bigs!!!! :laugh:

Sweet 16 is definitely the best - big enough to really punch where it counts, and not so big that it's a drag setting it up each evening (like my Big Bertha!)

Let me know if you need a hand mounting your old 12" finderscope on the new arrival!! :silly:

Congrats!

Phil.

Ah Philip, the very man;)

I'd like to take you on as a consultant early next year! You'd be paid of course or maybe you'd accept a donation to the Geodesic dome fund.

Need your expertise in optics and your toolbox and marine ply offcuts :laugh:

I want to add larger bearings ie. affix plywood rings around the existing bearings to increase the diametre in order to be able to lower base height, make a completely new smaller lighter stiffer base, (thats where your offcuts of marine ply and routers etc come in. Something I also want to get into is Binoviewing because I get bad eyestrain and can't really spend as long as I would like at the Eyepiece. Although there are Newt OCS's now which mean no need to cut truss poles, once the idea of shorter truss poles came into my head I imagined all the other benefits like solving inherent Lightbridge balance issues and an EP height that this short @rse wouldn't need a step stool for. Also means that in combo with a newt OCS the binoviewer OCS barrel would no longer protrude into the lightpath reducing contrast and introducing funky diffraction effects. Thats where your optical expertise would come in. You could use that boffin like brain to help me decide whether my already oversized secondary is large enough to accomodate the wider lightcone and if not what size new secondary I would need or indeed whether it was all moot with the amount I wanted to shorten the trusses maybe meaning the lightcone would vignetter at the bottom of the drawtube. Your tool box might come in handy here too for shortening the truss poles. We'd need to cut some off and flatten the new ends into spades and drill out holes for the end clamps.

I'd also love if you could evaluate my mirror before I do any mods. If its a lemon, meade ask for the whole scope back.

Can we talk further about this?

If you have too much on your plate as it is, no worries.

So you spent the money on the scope rather than the materials to do up the place?:laugh: Good man.

Can't wait to see the scope on the next observing session, I look forward to seeing you juggle the truss poles as you attempt to assemble it with an appreciative audience in attendance doing little to help.

Does this mean you won't be requiring the usual half an hour warning when it's time to pack up?

Seriously, congrats on the scope, it looks a beaut and let me be the first to accuse you of the recent lousy weather.

That poor old 12", what will become of it now?

Paul

Calibos wrote:

I want to add larger bearings ie. affix plywood rings around the existing bearings to increase the diametre in order to be able to lower base height

One very important thing to keep in mind. No matter how big you make the new bearings, the centre of gravity remains roughly the same. i.e. the pivot point will be constant. This means you will only be able to lower the height of the OTA by as much space as there is between the bottom of the existing OTA and the existing rockerbox. Even if you added weight to adjust the COG, you cant lower the eyepiece height because the bottom of the OTA still has to clear the base of the rockerbox.

Methinks a stepladder is going to be a much easier solution.

No problemo - once the mince pies have done their worst and the noodle has dried out again after the traditional festive hammering I usually give it!

For checking the size of your secondary / illuminated FOV, try playing with Newt over Christmas. www.dalekeller.net/ATM/newtonians/newtsoft/newtsoft.htm . You can fiddle with such things as primary-secondary spacing, focuser height, fully illuminated FOV size (for 1.25" and 2" eps.)

Probably easier to build a complete new lower rocker box than modify the existing LightBridge one - gives you more scope to muck about with the design. Ditto the side bearings - I have loads of offcuts for these.

Testing the optics shouldn't be a problem either, though I'll need to keep the mirror for a few days to ensure I get the right conditions for testing. I'm knocking up a Robo-Foucault tester at the mo, so watch this space! The quickest and simplest way to test the optics for yourself is to put a Ronci screen between your eye end the eyepiece while the scope is pointed at Polaris. A Ronci screen is a piece of glass covered in finely divided parallel lines, 50, 100 or 200 lines per inch. What you should see when looking at a slightly defocused star is a series of dead straight lines (for a paraboloid mirror like yours.) Any deviation from straight denotes deviation from a perfect surface. I have a few Ronci screens in my optics box!

Actually, this is a good excuse to pull the finger out and finish building my interferometer for testing optics!

Phil.

Sorry Dave, I wasn't very clear in my post there. I know larger bearings won't lower the Eyepiece height. The larger bearings are purely to make a less tall base/rockerbox possible.(Easier fit in the car and shorter sides less prone to flex) Its the shortened trusses that will help with inherent lightbridge balance issues and eyepiece height.

I was actually talking about a new rocker box from scratch Philip. I could probably make an attempt at the straight cuts myself but all I'd have is a handsaw and an electric saw I wouldn't have a hope of being able to cut circles, ie. the bearing rings and bearing cutouts in the rockerbox. The reason I was talking about bearing rings affixed to the current aluminium Lightbridge bearings rather than all new bearing discs is that those alloy wheel looking Lightbridge bearings are part of my 'Theme' for the scope. Yes the scope will have a car theme based on an eighties crime drama Tv show staring a lifeguard The scope will have a name too. :laugh: So I really want to keep the current bearings.

I'll actually be ordering a round powered groundboard along with the servocat and argo from stellarcat, with the diameter being the same as the width of the square rocker box.At Least I won't need to make that. The baseboard of the rocker box will be square. None of this OEM lightbridge over sized rocker box malarky with a round baseboard that overhangs the rockerbox as it were by 5 inches around. I wouldn't mind but this 'overhang' is totally superflous to even the OEM rockerbox. The feet are about 5 inches in from the circumferance under the rockerbox sides anyway. So the 32in diametre baseboard and groundboard add nothing to the stability of the scope anyway!!