paul Posted April 25, 2021 Share Posted April 25, 2021 My Orion Optics 250mm is an ongoing refurb project. I was disappointed that guiding wasn't as tight on my new mount as I had hoped and too many images lost their star shapes. I noticed that the rolled aluminium rings seem very stiff but once you mount the scope in them with a guider on top of that gives enough moment to cause ring wobble on the vixen plate. I decided that was a good candidate for improvement ( the rolled OTA tube is very stiff). I looked in to replacement rings but the kitty isn't bottomless. So I decided a bit of bracing might do the trick.... I've bolted a 350x300x6mm plate to the vixen plate as a sold inflexible base. I'm using extruded 2020 aluminium to make a structure to rise up from the base and attach to the clamp assembly of the rings. That's the plan anyway. This will add about 3.5kg to the mount but I have the capacity. I plan to try out the guide scope fitted to the side off the extruded verticals. That should be very rigid too. At the moment support on one side looks to be sufficient but I am allowing for support on both sides of the rings. Its looking a bit rough and ready but it is going in the right direction. I am allowing for a lot of adjustments as my cutting is not very precise. The jigsaw cuts through the plate like butter but its tricky keeping a straight line 🙂 its a big project me! Once all the parts are cut to size and fettling complete I'll clean it up and give it a good coat of paint. Some shots of the ongoing project ... An early stage with the rings in place checking for clearances: more to follow soon. 1 Quote Link to comment Share on other sites More sharing options...
MarkAR Posted April 25, 2021 Share Posted April 25, 2021 Good luck with this project, hope your plan works out. Quote Link to comment Share on other sites More sharing options...
paul Posted April 25, 2021 Author Share Posted April 25, 2021 (edited) 7 minutes ago, MarkAR said: Good luck with this project, hope your plan works out. Thanks, by the time I'm finished the only part of the OTA I've not modified will be the spider! Its done me proud over the years first on an eq5! unguided imaging with a modified webcam (2005). Edited April 25, 2021 by paul Quote Link to comment Share on other sites More sharing options...
paul Posted April 25, 2021 Author Share Posted April 25, 2021 Brace V1 coming together nicely.. And here it is in place and all balanced The one counter weight was still just enough to balance, but now everything is very rigid. I need to trim and find some endcaps but I'm looking forward to trying this out soon. I'll probably do the painting in Mid summer when the dark skies have gone. 2 Quote Link to comment Share on other sites More sharing options...
paul Posted April 27, 2021 Author Share Posted April 27, 2021 Conditions were no good for real imaging last night but I could at least try out the new focuser (I'd just a new CNC low profile one), bracing and position for the guider on the CEM70G. It wasn't windy but I am pleased to say without messing about (just rough balancing and running the PHD2 guiding assistant) I managed periods of tracking ranging from <> 0.6 to 1.1 steadying out at around 0.8 arc seconds. This is very similar to what I achieve with the light load of the Bresser 150 (same range but averaging 0.65) and its a significant improvement and closer to the resolving power of the scope than it was before (<> 1.5 arc seconds seemed to be a typical night). I'm pleased to say NiNA handled the new focuser well (APT struggled so more tuning of parameters is required there). The CC required the extension tube of the focuser to be used which added some slop affecting collimation. The CC is a snug fit and 100mm long so I'm going to stack a few parfocal rings on the CC to keep it consistently out of the draw tube by about 15mm. Then I can avoid using the extension and hopefully the slop will disappear. Quote Link to comment Share on other sites More sharing options...
AstronomyUkraine Posted April 28, 2021 Share Posted April 28, 2021 On 4/26/2021 at 1:23 AM, paul said: Brace V1 coming together nicely.. And here it is in place and all balanced The one counter weight was still just enough to balance, but now everything is very rigid. I need to trim and find some endcaps but I'm looking forward to trying this out soon. I'll probably do the painting in Mid summer when the dark skies have gone. You'll not be short of space for accessories now. I have the same rings on my scope, a 1200mm f4 Orion Newt. They are a joke, and the 175mm fovetail that comes with the rings is an even bigger joke. I need a dovetail at least 350/400mm for my scope. Quote Link to comment Share on other sites More sharing options...
paul Posted April 28, 2021 Author Share Posted April 28, 2021 (edited) On 4/28/2021 at 9:41 PM, AstronomyUkraine said: You'll not be short of space for accessories now. I have the same rings on my scope, a 1200mm f4 Orion Newt. They are a joke, and the 175mm fovetail that comes with the rings is an even bigger joke. I need a dovetail at least 350/400mm for my scope. For me the biggest issues is the rings which I seem to have sorted. On a larger OTA I can imagine the tube walls begin to flex more as well. Have you considered reinforcing rings of some sort? Yes, its certainly a platform to build on 😁. I'm happy with how little extra weight its added, the guider is on a very firm base so I'm hoping for fewer wild oscillations. I did consider using more 2020 to extend a cage down the length of the tube but to make a cage I need a good way to add triangles structures and my OTA does seem rigid enough at the moment... more testing will tell. Edited April 30, 2021 by paul 1 Quote Link to comment Share on other sites More sharing options...
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