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Well that escalated quickly…

 
01 Feb

The barn door project, still at it but hitting lots of limitations… What’s the solution?

Well, in short, money… Throwing money at it, which at the moment with all the overtime I’ve had in doesn’t seem as fear provoking as it would have done this time last year; and as I’m wanting to push further on the journey it seems a bit more a logical step.

With the barn door tracker, it’s been very nice to learn things on, not just basic DSO capturing, but also other software things as well as working with ESP type chips instead of the Atmel, however because it’s not built with anything like precision, it can get a bit frustrating. For one, the run time is only about 80 – 90 minutes before the weight on top is greater than the reactive force on the bottom of the drive shaft, so it starts binding in the drive nut, then also with loose tolerances of stuff that can be bought in just the local hardware shop, it throws periodic on each turn of the drive motor where the drive shaft is throwing a slight eccentric wobble. Also with it being wood it’s a bit prone to splitting and the damp of a winter evening on the back.

All of these, whilst small niggles, can be easily addressed. First off would be to create a longer drive shaft and shaft guide with an anti-backlash system so it stays centred longer as well as upping it to a thicker rod which would be more resistant to weight pressure from above and reduce a bit of the flexibility there. The periodic, again nothing too serious to resolve, perhaps a spacer inside the coupler to centre the rod better or perhaps not having the motor connected directly to the drive rod and use some form of clutch or gearbox to turn the shaft; and then on the other end using a round bar for the nut instead of using a very small point of contact on a dome. Then the rigidity, again nothing too serious, just build the thing out of different materials, perhaps stainless steel as whilst aluminium may be lighter, to get the rigidity of stainless it’d need a fair bit more.

Easily manageable, not too hard to build or design and throw to third party; but there is one little problem… Building that would throw the cost of the materials form a few Euros like now up in to the region of 200 – 250, including fabrication costs.

That’s quite a bit of money for what started as a little, fun project and for imprecise engineering it stops making sense when something like an EQ3 or an similar mount (albeit non-motorised) can be bought new for not much more, or when something like the Star Adventurer Mini or the little wind up Omegon (very nice, would like one just to keep in the car) are in the same price range.

With this in mind, after calculating the machine and looking with what I’d learned from it, and how much time it took to get to a useable state for doing DSO work with, I decided that the best route to go would be to get a star tracker; as one that can hold my kit in the post Christmas sales, though it’s back ordered at the moment, would cost me only 100€ more than building another barn door. So if I calculate my time as well, it would cost me less to buy a star tracker and about the same to buy a star tracker and put in autoguiding.

From what I’ve learned with the barn door, it’s definitely not been a wasted project as I’m going to put a better one together when I get time as it’s fun, it’s good to teach people the basics with, and after using one of them anything else will be a lot easier to manage.

At the moment, I’ve a SkyWatcher StarAdventurer 2i on order, not that I wanted the WiFi, but the price of it was reasonable; but with this confinement at night, I’m starting to get a bit itchy as during March and April, according to the Stellarium, the little patch of sky I have will relate to some dog-days before it gets to milky way and summer nebula season… Hopefully by then we’ll be let out, but I’m hoping the back order isn’t long enough so I don’t miss the chance to hit the Seagull Nebula and Sirius.

Time will tell.

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