[mswhin63 (Malcolm)]

Fairly busy at the moment, so I am going through as I write so sorry for repeats.

Originally Posted by Calibos

Hi Malcolm,

Though this kind of wedge has been on my mind in the last fortnight, your new postings inspired me get up of my arse to do some preliminary testing

I noticed the post has been fairly quiet so I thought there was a bit of hanging on to see if it was going to develop into something

Originally Posted by Calibos

Taking off the UTA and Mirror cell meant I didn't need to build something and could just 'Wedge' the rockerbox on a stool

This is one of the few instances in astronomy where far northern or Southern latitudes are actually a bonus. 53ºN means my rockerbox is tilted 37º.

Seeing as I already have a Servocat Drive system (yet to be fitted) I would have no need for this for visual use but if I can find out whether a scope this weight on a side braced baltic birch rockerbox replacement can be made stiff enough for Astrophotography/Long integration Mallincam use then I would definately be interested in attempting this in the future. Preliminary enquiries with Gary at Servocat indicate that the servocat drive and Sky Commander combo can be operated in Equatorial mode and in fact the drive method for the Meade Lightbridge servocat kit arguably lends its self to this kind of use better than the regular direct drive/Alt cable versions used on premium dobs.

Well having a drive already is one up on me, The motor drive is going to be the biggest challenge financially for me and so I am starting with a very basic configuration. This will really test the system. Definitely higher latitude will make it easier, I suppose I was just purely lucky to get a good COG. Maybe this is the scope that I am using. I was thinking a bit more and noticed that the best COG for my scope is when the DEC/ALT bearing is directly over the pivot point. This which I am going to test more over time is the key to the ease of making these, so the base board could be created to allow the ALT bearing to be directly over the pivot.

Originally Posted by Calibos

The lightbridge alt forks and bearings lend themselves to equatorial use in my case though if I was further south they wouldn't. The rims are helping to hold the OTA on the forks. Small versions of some of those socket ball bearings used on conveyors mounted in the fork against the rims of the alt bearings would keep the OTA from sliding laterally when pointed east and west while preventing binding of the 'higher' rim as it rubs against the 'higher' side fork.

Mentioned before if the baseboard is altered to allow the ALT bearing to be over the pivot then it could be possible to make it for different latitudes easily. Still more testing to confirm. The concept is that the scopes COG will prevent issue with binding etc. But one thing I need to test is any other factors that may occur. I found the COG for the wedge requires the telescope to be completely set-up as the mirror adds the necessary weight to balance the scope.

Originally Posted by Calibos

Like yourself, I would be raiding the parts bin of other unsuccessful projects. Specifically I have motors and threaded rods and various other bits and bobs from a JMI TNT Lightbridge drive system that never worked right on this dob. I'd been thinking about fast accurate polar alignment and remembered Tom Olpowski EQ platforms with his GLP polar alignment stalk. Seeing as I have to make my optical and tube axis coincident for a Rotating UTA mod anyway (which is even more of an imperative if I went ahead with this), I would set a stop for the OTA to perpendicularise it with the rockerbox at set up. So set up would be as follows:

Set up wedge and broadly align it with sprit level and compass and Alt scale. Affix rockerbox to wedge. Place OTA on rockerbox. Align GLP with high power Eyepiece on a bright star. Push OTA against stop. Now the GLP and Eyepiece are aligned with the axis of the wedge. This is where the JMI bits and bobs come in. While at the eyepiece use the JMI hand controller to make fine alignments adjustments to the wedge via the stepper motors till I am accurately poar aligned. No half hour of drift alignment On a sidenot, the JMI handcontroller performs dual use as a motorised primary collimation controller with the other two spare JMI TNT motors I have

I mainly raid the parts bin because I need to clean the garage. My wife is getting insistent to clean up and make more space. It is working. I agree that polar alignment will be theoretically a lot easier with this set-up mostly before DOB is the equatorial axis. I think this will need to be tested but in thought look good.

Originally Posted by Calibos

I'll be using a 500mm VXB bearings lazy susan ring for my rotating UTA and funnily enough for my Rockerbox too. ie. replacing the MEade needle roller bearing lazy susan system. I needed to do this to be able to implement a powered groundboard system to get the heavy batteries out of the rockerbox which would unbalance the rockerbox in equatorial mode. The side benefit or maybe infact the main necessary benefit is that the Rockerbox would be kept orthagonal with the groundboard mounted to the wedge by this kind of lazy susan (400kg capacity) and the ring would take the strain off the central pivot too.

Really solid, I am still using the original bearing and will continue so until I decide to head for a more accurate a strong bearing/drive system. That is my ultimate intention but a long way off.

Originally Posted by Calibos

Having thought about this, there is not much about this plan that necessitates drastic changes to my particular scope or to other modding plans for it and in fact some of the required changes are beneficial to the scope even in Alt/Az mode anyway. So I guess I have nothing to lose except time and/or patience by trying this out regardless. If its good enough for Astrophotography, Great, if not I just wasted some time building the wedge but sure it kept me out of trouble for a while so it wasn't a complete waste of time

Funnily enough I am also doing a conversion from Truss to 3 strut like your flextube, I have a thread on CN about it) Those changes are going to give the scope the benefits of very quick setup at home like the Flextube while maintaining the ease of transport of a fully breakdownable OTA and smaller rockerbox of the Lightbridge compared to the flextubes. The shorter Lower OTA and longer poles however and greater propensity for pole flexure mean I will be implementing a string virtual truss system.

If I can pull this all off it will be pretty cool to have a big driven 400mm F 4.5 scope capable of private AP or public outreach mallincam video astronomy by simply attaching to my wedge or used in Alt AZ mode for private visual or public outreach visual use.

Good luck with your end, I do not propose this to be a super duper EQ system but as I have managed decent photos with the past EQ platform I have no doubt this will provide an equivalent but easy build. I mainly considering planetary work for this set-up and with reasonable Frame Rate accuracy is not a major problem. But if it works better then happy days