Jonk

Funny you should say that...

Absolutely, that was exactly what I thought!

Ooooh guess what's ready to take to the powder coaters?!

I received this photo just now...WIP - should be complete tomorrow, ready for powder coating. I hope they can read angles and dimensions!

Nah, I did think of that but there's much more to do on top. Once I'd shown them what I wanted and why, they were happy to get on with it. I want it to look vaguely professional!

They know full well they only have 1 chance to get it right! It's a boat yard down at Hamble Marina so they primarily do boat and yacht repairs, so should be good at cutting and welding.

Well, the pier is finally somewhere where it can be modified! This is the machine that will make the cuts - up to 300mm diameter tube with high accuracy apparently! The only thing I don't like about this is the cost - but it's the best I could do and sometimes you just have to bite the bullet. Looking forwards to getting it back so I can start to dig for gold!

Yes, the same method also applies to a newtonian mirror which I have done countless times - I was more interested in seeing drift aligment using 3 bolts, as that is likely to be what I end up having. I don't plan on using a polemaster and have tried a lot of software PA routines, but for me, nothing beats pure analogue drift aligment without software errors to worry about. Vlaiv is right, the backlash reading seams odd (1/4 of a second?), so unless you have slippage, that could be software not telling the truth, or maybe the motors aren't responding quick enough to the command? Good luck with your dual rig tests, I'll be watching for the report!

Although your PA is already set well enough for your needs, would you be able to do a video of the PS setting please? I'm interested to see how it's done with the 3 bolts, especially the drift alignment method rather than with a polemaster.

Unfortunately I am a long way off being in a position to buy one at the moment, but thanks anyway.

Did you buy direct / import or through Astrograph or whoever was the distributor at the time?

That's ok, I need time to convince the bank at home to go for it anyway!

You know I did think about it, and would find a way to afford it but I doubt we have the skies to warrant the extra resolution it offers over the 140. Don't tempt me!

Some of us have to go to work....! I aim to have the pier done in the next month or so, then I'll be looking at ordering the mount and 'might' be able to get one from this current batch, else it will be early in the new year. Whilst I wait for delivery, the dome can go up and I can start the internal work.

What I found works well is pick a star in the guidescope on the E horizon at 0 degrees dec, then watch it track across the sky using PHD's closeup of the star. As the star drifts up or down, adjust E-W, if it drifts left or right, adjust N-S to keep it in the middle of the crosshairs. This assumes you have the camera orthogonal to the mount of course. This is drift alignment without using any software to tell you what to do. I found that once the star didn't move in 1 hour, then field rotation wouldn't be visible in most people's subs (assuming most max at 30 minutes). I learnt not to rely on software at all for PA as none of it appears to be close enough / accurate enough. Or if you really want to do it old school, use the same method using an eyepiece with a reticle. Just be prepared to sit there for an hour plus to adjust when necessary. I would ignore errors flagged up by software, they're never going to be accurate, there are too many variables, some of which have been mentioned above.

True, this plate hasn't been chosen yet, it's all in my head at the moment. The method of scope alignment hasn't been decided on yet either... all future stuff, I have to get the pier done first!

Aha that's one good thing about a bent knee pier, no flip! I know it will be tough, but if it was easy it probably wouldn't be as interesting. No one does astronomy because it's easy.... do they?!

What I'll try to do is mount all 3 on a flat plate, bolted directly to the mount - no dovetails required. Something like this I can get for £0: As the large scope will be central, and a Star 71 will be on each side, the balance L-R should be straightforwards, or at least I hope it will be! The cameras and focusers will be the same and the guide scope will probably be central, so if anything is out of balance that way, I'll have to add a moveable weight. Forwards / backwards should be achievable by sliding the central scope. Worst case, I'll have to add small weights, but this may be the lesser of 2 evils.

Possibly, but for this purpose I have the worst case from 2 others (the maximum length mainly). I would ask to see where the scope sits in the rings for balance without any additional counterweights, but it would depend on your camera etc. to be accurate. No, I've used Autodesk Fusion, as I already use it at work for modelling things for 3D printing. The idea behind this was not to design a product, it was to come up with an easy / affordable way to modify what I already had. If the Mesu 200 MK2 wasn't ready, or I didn't know about it, I would've probably already ordered a MK1 (if still available) and left it at that. As it is, I want to take the opportunity to make the best of what I have, hence the modifications. I can run analysis in Fusion, mass loads, vibrations, temperature, bending etc but for the small parts we make as one offs, these analyses are not often needed, so I haven't learnt how to use these tools properly. From my limited design experience, I can see that the upper weld would be the most potential weak spot, but 1 properly welded 10mm thick pipe should be more than enough for say 150kg (max) on top, even at an angle. It is unlikely that I'll ever get near to 100kg so I should be ok - I have asked others for advice on this and whether any additional support is needed there, which won't affect the scope rotating around the RA axis. The mass of the pier once complete, assuming the analysis is correct and I have done it correctly will not be far off 200kg! The current pier is around 100kg. It's a big heavy beast but I want to do this once and once only. There are a few machine shops around me and people at work have offered to help, so I should be able to get this done within a reasonable price.

Now I have watched that it is very clear that my observatory also needs a bed! Seriously though, thanks for the vid and good luck with it, I'm sure I'm not alone in waiting for positive reports.

Some quick adjustments and I think I'm probably about there. I'll get the drawings to the local metal shops and hopefully a favourable price and quick turnaround will happen. Thanks for the help all, wish me luck!

1 cut at 22.5 degrees and one at 2.965 (to be close to exact) degrees! Then rotate and weld, yes.

Latest from Modern Astronomy is that pricing will be added to the website, maybe as early as next week.

Yes, that's it! I haven't looked at alignment yet, but I suspect I will come calling for your ideas if i choose to make something, or I'll just buy the commercially made ones. Thanks, I do enjoy CAD and am constantly tinkering and adjusting drawings like this. Very valuable information you've provided, so thanks. I only hope my efforts reward me in the coming years with some good results! Again, very valuable information - thanks very much. I'll have to adjust the pier to suit, as I'm probably too close for comfort, but there's not a lot in it, a couple of inches at most.

Ah I see - yes that is something I need to know to ensure I have enough clearance. I'd rather not have to add weights due to lack of 'reach'.