The Problem with Loose Ends

The danger with loose ends is that sometimes you can pull one and things unravel.

So there I was early last week, happily finishing things and marking them off my list when the next thing you know I'm off on one of my parenthetical random walks. I was adding new columns to the observing lists portion of the main planning tool: one for status (observed, not yet observed, re-observe) one for setting observing priorities, and a third for 5-star object ratings. With the ratings column came a small problem. The ratings (and notes) that are displayed depend on the selection of a note group, and I hadn't placed a group selection on the dialog yet.

I dislike designing the layout of dialogs, particularly when space is at a premium, and I really hate having to do the same one more than once. So naturally I started thinking ahead to what other items might need to be worked in. This lead me to thinking about the new imaging features. I knew I'd need a toggle of some kind to switch between visual and imaging modes. What else would I need? It was an innocent thought: perhaps I should look into imaging a little bit more so I'd have a better idea what I wanted to accomplish on this dialog.

Before I knew it I was knee deep in readout noise, exposure times, and signal to noise ratios. My desk was covered with pages of algebra. And even my dreams had CCDs in them.

The point of all this was to find imaging analogs to the optimum times and detection difficulty that SkyTools uses as the basis for planning visual observation.

Visual observation is all about contrast. For the best contrast the observer requires the darkest sky possible. So the important questions for the visual observer revolve around how dark the sky is.

Imaging is all about signal to noise ratio. Imagers can cheat a bright sky with a longer exposure or by stacking many exposures. Many of the important questions for the imager still depend on how dark the sky is, but they are more subtle. The visual observer may ask, "Should I observe Sh 2-1 tonight, or wait for a better night or darker location?" while the imager asks, "If I observe Sh 2-1 tonight, how much more time and effort would it take compared to a darker night or location?" Therefore my job to support imaging is to quantify "time and effort" in the observing list. Optimum times also mean less: more important is the observing window and its duration.

I also realized along the way that my new ability to model the sky brightness can be folded into a useful tool for calculating exposure times.

Anyhow, it's back to loose ends again. But I'm really happy about my diversion into imaging this past week: the new imaging features were very hazy and unclear, and now they are beginning to come more sharply into focus. I can't wait to make it become a reality!