Reddit mentions of STEPPERONLINE 0.9deg Nema 17 Stepper Motor Bipolar 0.9A 36Ncm/50oz.in 42x42x39mm 4-wires DIY

Yes, electronics can cost a lot, and many of the telescope manufacturers make things, that when I look at them belong in the 1990s or 2000s, in terms of the way they work, and honestly could have been $400. It's basically the TI calcuator system: https://xkcd.com/768/

People have replaced those control systems, using technology (especially things like improved stepper control) which has come about for various reasons, like 3D printers, and simply faster microcontrollers.

Here's one: https://www.youtube.com/watch?v=tCBgmgc8qiA conversion (I suspect based on that it was using one of the faster controllers, but mine can do fine with an Arduino Mega + Ramps (the cheap controller))

• SVP $300 New
  
• RAMPS kit: (https://www.amazon.com/Eiechip-CNC-3D-Printer-Kit/dp/B07BKVPZ71) $27 (Not the best drivers, but this can be upgraded if you want later probably also want a PPS source, but it can be dealt without. As can the board.)
  
• Motors (Honestly cheaper, but at 0.9 degrees these are a bit better than the normal 1.8 degrees) https://www.amazon.com/0-9deg-Stepper-Bipolar-42x42x39mm-4-wires/dp/B00W98OYE4 2x$20
  
• Pulley for mount (60 tooth) https://www.amazon.com/Timing-Pulleys-Aluminum-Printer-Wrench/dp/B07QH1ZJ9L $8 (2x)
  
• Pulley for motor (16 tooth) https://www.amazon.com/Anet-Timing-Pulley-Aluminum-Printer/dp/B07D294B2T/ $8
  
• Belts https://www.amazon.com/132-2GT-6-Timing-Belt-Closed-Loop/dp/B014QI4PU2/ $12 (I think those are what are needed, I'd have to look again to make sure. I use 110s, but have 20 tooth 1:1, as I use geared steppers, with upsides and downsides.)
  
• Bracket (3D printed) or something made: https://www.thingiverse.com/thing:2278288
  
• M6 screws and 2 nuts (<$5 at local store)
  
• Onstep https://groups.io/g/onstep/wiki/home
  
  So At 408 + a bracket (Easy and simple 3D print or easy to DIY, look at the OnStep Showcase for a number of them.)
  
  Along with a 1/4-20 screw and a dovetail (Oh look: https://www.thingiverse.com/thing:2039785) , and you've got all of the functionality of a one of the Star Adventurers, along with the ability to mount pretty much any telescope up to 8" with a vixen dovetail.
  
  Plus, unlike from what I can tell of almost all commercial ones, they don't seem to compensate for misalignment when tracking. (Ie, they only move RA, not DEC, unless guiding.) Here are some examples of unguided long exposures with dual axis compensation. (Also, He doesn't usually process them, these are per other discussions straight off the camera) https://www.flickr.com/photos/11381732@N08/albums/72157683118306836
  
  Though that uses PEC (Periodic error correction, because worm gears often have high/low spots, so it can be corrected by basically guiding a few times and storing the corrections, which are then replayed). If you want that stored, which isn't included on what I mentioned above, but can be added for the cost of a magnet or two and a hall sensor ( https://www.amazon.com/WINGONEER-Effect-KY-003-Magnetic-Arduino/dp/B06XHG9CYN/ $8 and magnet https://www.amazon.com/Personalized-Multi-Use-Whiteboard-Magnetic-Refrigerators/dp/B075PMV2BC/ $8 ) Otherwise you'd have to retrain it each time.
  
  One thing is that the microcontroller and drivers aren't the most advanced, but you can upgrade them if you want. (STM32 about 3x as fast, but it's rarely needed, except for better alignment is about $60, but add two drivers, so call it a net of +$40 extra but that the kit adds wifi ($6 and a bit of wiring to the original) and a hand controller to it. the faster processors ESP32 and Teensy cost more but are something like 14x as fast allowing better alignment. Mind if you use Howard's Sky Planetarium, it won't matter too much, and it'll be able to process on the computer.)
  
  All new, and unless you have space taken up as your main concern the above setup is in pretty much all respects better than that suggested by dan.

I also HATE the wheels and upgrading to linear rails has been great for me. I didn't really like any of the designs it there, so I ended up making my own designed to use high quality used linear rails readily available on eBay. My Z axis linear rail conversion will allow you to easily and quickly level your X gantry, so that might kill a couple birds right there. The used rails cost about $45 each and work a lot better than the cheap Chinese rails.

https://www.thingiverse.com/Bad_Mechanic/designs

You don't need extra torque, but upgrading to a 32bit board with TMC drivers is still recommended because out gives you all the memory you'd ever want, is very quiet so you can remove the dampers (which are problematic in several ways), and can do good curves at speed.

Strapping the printer down won't gain you anything and might actually degrade your print quality.

While I after a dial Z mod is a better engineering solution...it's been shown you don't gain anything in print quality from it.

Corner brackets won't gain you much.

Unless you go direct drive with a Titan or Bondtech extruder, the $15 upgraded aluminum extruder is as good as any.

You could add Z braces to support the uprights for tall prints, but at those heights the print wobbling is more of an issue and will limit your speed a lot more than the Z uprights wobbling.

One thing you should do is upgrade to 0.9 steppers on X and Y as they're not that expensive and mostly eliminate vertical fine artifacts (VFA).

https://www.amazon.com/dp/B00W98OYE4/

If you don't have a PEI bed yet, those are also an EXCELLENT upgrade.

TL;DR Do the linear rails, do a 32 bit control board with TMC drivers, 0.9 steppers, and a PEI bed.

PS - If you haven't done a BLTouch yet, DO IT!!!