Tracking comet C/2022 E3 ZTF

On 5 Feb 2023 I tested the tracker on the "green comet" aka C/2022 E3 ZTF. 

5 x 60 sec exposures, "fog-reduced" using GIMP levels adjust tool. Because the comet itself is largely fog, this does have the downside of diminishing the comet a bit. Swings and roundabouts I guess.

I'd not realized just how much the comet would move in the 22 minutes I was capturing the images, so I though it illustrative to combine them into a animated gif. I had to align the star field manually, so it jumps slightly between frames, but overall I was reasonably pleased with the result.

My notes from the night:

Green comet C/2022 E3 (ZTF) travelling through the constellation of Auriga for 22 minutes on 5 Feb 2023 between 22:07 and 22:30. A sequence of 10 x 60sec images. Camera Canon 5D3 with 200mm lens on home-made astro-tracker.

Bright star in the upper left is Capella, 1 deg 38 min distant. Vertically above the comet and 0 deg 14 min distant is HIP 24109, a mag 5.65 star. The comet is travelling through a triangle of mag 11 stars and moved approx. 7 arc mins during the 22 minute sequence.

The moving "blur" to the upper right of Capella is either a UFO or dirt on the camera lens/mirror. Subsequently checked the lens/mirror and no marks detected. (... cue Twilight Zone music!)

Tracker testing (2)

It's almost a year to the day since I posted the last update on testing. That's not because I've not being making progress, I've just not got around to writing about it. My bad.

The "horseshoe" star shapes I was getting suggested to me that the rod gimbals needed improving. These were the supporting pieces that held the threaded rod and allow it to remain perpendicular to the axis of the tracker itself. They were crudely pivoted on the points of screws that projected through from the sides of the block that held it to the main tracker arms. It's possible that if the axis of the pivots was not truly parallel to the tracker boards and perpendicular to the tracker axis then the turning of the rod could introduce some overall oscillation to the mechanism.

Eventually I decided to replace the pivots with hinges, that would create a more precise mechanism and hopefully fix the problem. Because the supporting pieces for the rod had been made separately and just screwed on to the tracker boards, it meant I could replace them with new ones made to accommodate the new setup. The images show how this was done. The centre of the rod aligns with the axis of the hinges, thus maintaining the correct geometry. The whole thing now moves much more precisely.

It's gratifying that now I've made these improvements to the construction, the tracker tracks properly with little or no correction needed to the geometric calculations built into the software i.e. I don't need to tweak the speedfactor through the DIP switches.

Here's a 60 sec tracked exposure of the Pleiades, as captured and after adjusting the input levels with the Gimp to remove the background fogging as much as possible.

I'm pleased with this, and I'm not sure that such a simply constructed tracker could deliver any better results.

As I mentioned previously, my suburban sky is horrible with light pollution, anything much longer than a 60 sec exposure is so fogged as to be a waste of time. However, my brother lives in one of the darkest skies spots in the country, so my next plan is to invite myself for an overnight stay. Roll on the clear weather!