Lego Star Tracker V4 Test 5 - I Got Problems

Questions Answered

Alright, I'm determined to get my focus right tonight and my batteries are all charged and I'm ready to go.  I only made one very minor update to the tracker.  I stuck 4 little foam pads on bottom of the base to hopefully attenuate any noise due to vibrations and minimize any level issues with my table.

This turned out to be a great idea.  Not because it worked real well (although it did), it actually helped me figure out the problem I was struggling to understand all along.  How could I not track, then track, and then not track again?  Well, I figured it out.  And man, I got problems now...

 

Off to a Good Start

I started with the usual routine and started imaging.  I decided to give Andromeda a go tonight as it was in a nice position in the sky.  I knew I'd have a small issue with some trees in the corner of my yard and my neighbor left their porch light on, but hey, it'll be fine.  

Everything was rainbows and unicorns and I was tracking nails at 60 seconds.  Life was good.  But a funny thing happened about half way through my imaging plan.  Small trails started appearing in my shots and then the whole frame started to drift.  What was going on?

I double checked my polar alignment and weird, I need to make a small adjustment.  Fine.  Back to the screen.  Next photo looked good and then the trails started showing up again.  Check polar alignment again.  Hmmm, another small adjustment.  Perplexed.

Let's check that the table is level.  Ok, it's not.  The humidity and temperature have caused the ground to go wonky so I spent a couple of minutes getting that sorted and then polar aligned again.  No joy.  Still have star trails.  Arg, now I'm frustrated.

Think... Think... Think...  And then Clunk!

The whole rig went over on its side and the Legos did what Legos do, they scattered.  I'm at least thankful that they provided a bit of a cushion for the camera and I'm doubly thankful I had the lens hood firmly attached.  Camera is fine.  My tracker on the other hand is a pile of bricks (mostly it was just the base that blew up).

But in this tragedy, I had an "Ah Ha!" moment.  I know what's going on.  And if you've been reading along, you might have already figured it out, or supposed, or yelled it at your screen before I was able to piece it all together - yes, pun intended. 

I made the mistake of assuming if I kept everything tight and compact, I could either ignore or overcome balance issues around the axis of rotation.  I was already using that a bit to my advantage.  But I was wrong.  When I added the foam pads to the bottom of the base, it changed the balance of the system just enough to definitively expose this issue.

This is a big big big big problem.  I can't ignore this.  But more on this in a bit.

The Results

There are more important things to write about, but I was actually pleased with the photos where the tracking was good.  Before the disaster, I took a total of 40 pictures but after taking the wonky ones out and removing the snaps with satellites, I ended up with about 15 stackable photos.  I won't go into the processing details but here is the final, lightly processed result.

Canon 250D 50mm f/2.8 ISO 400 - 15 x 60 seconds

The colors are a bit off and trust me when I say I really didn't put any time into this.  But there's enough here to see that even 15 stacked 60 second photos captures a lot more signal and detail and also less noise than a couple hundred short exposure photos.  Yeah, very pleased with this result all things considered.

What's Next

I'm not really sure to be honest.  I have a couple of ideas on how to fix this issue.  What is clear is that I am going to have to find a way to counterbalance the camera around the axis of rotation.  As much as I think I hate to admit it, I might go all the way back to my "box" design.  So back to the beginning.

But with what I've learned along the way up to this point, I believe I've found solutions to many of the problems that caused me to move on from that first iteration.  And this is how things go sometimes so here's a peek at what I'm thinking.

I'm nervous about this though - especially on how I'm going to link the gear train into this.  And how I'm going to run the rod through the wooden block.  I'm also going to need to think about if there is a way I can engineer some kind of clutch into the design so I can easily set or reset to a home position, without simply running it in reverse which would take several minutes at this gear ratio.  

Yay - lots of new problems to solve.  But this is what makes it fun.  Try, fail, try again.  I've already seen what is possible, and that this is actually possible.  So I'm totally ready to keep going.