Astro Calculator

Has potential. Nice sky map feature. But I had problems with the interface - in the plan tab for a fix the available objects only lists sun or moon most of the time but navigating randomly between different views I can suddenly get the stars to appear as available objects. Entered three observations with the same times and tried to plot a fix and got an error that observations are more than 24hrs apart. Couldn't figure out how to make it work. Uninstalled.

Problematic interface that leads me not to be able to recommend using this as a substitute for alternative methods. Data entry flow is not intuitive. Main menu has separate categories for "Astro Navigation" and "Educational Tools" but the labels of the various buttons do not make it clear what each is meant to do or how they differ. In practice the steps are always the same: (1) predict phenomena, (2) take direct measurements, (3) reduce sights and (4) plot a fix. The main menu has no such sequence. The first option in the first menu is "Position Fix". Selecting that gets you to a tab-like interface with stages called Parameters, Plan, Reduce and Fix. Aside from the cryptic "Parameters" tab, this sounds something like the steps above and seems promising. Turns out "Parameters" are parameters the developer thinks will remain constant over the use of this app, which isn't really true nor especially helpful to have them on a separate page. But that is a minor issue (especially compared to what's coming up). The "Plan" stage gives you something like a prediction of what bodies will be where at a time of your choosing. It even has a "Choose best bodies" feature which helps fill in the table. Unfortunately its choice of "best bodies" seems to be based entirely on their distribution in the sky (I'm guessing -- I can't figure out what's best about them if not that) but, again, that is not how celnav works in practice; in practice you want some combination of distributed at good angles, and also visible. Visible *usually* means "bright" but in practice really means "not behind clouds" which is something you won't know in advance. So you really want a list of several stars, including ones near each other, in case you want fallbacks if one is behind a cloud. Moving on to the most important part, and a place where this app has multiple critical shortcomings: Observations. The next phase is "Reduce". In this phase you can enter sextant readings. This includes time. In practice you always enter Deck Watch Time in whatever local timezone it is in -- NOT UTC. You also should not perform the local-to-UTC conversion when entering data, because that is error-prone (e.g. if the date changes or if you forgot daylight savings or if you added instead of subtracted, or ... so many things can go wrong). You should transcribe Deck Watch Time from the watch to the record in its most direct form, which uses LOCAL time. When taking sights at o-dark-thirty in the morning on a pitching boat deck when you're groggy AF, you do the most robotic steps possible. You do nothing even remotely fancy -- not even simple arithmetic. So you record time in local deck watch time. Yet this app has you enter DWT in UTC. If you do not know this, the fix ends up however many timezones away from where your ship was. Minor aside: the app's default "time of fix" is November 22, 2008. Bizarre. Not today's date. Not the median date of all observations, but November 22, 2008. Is that an easter egg? Super not useful. Also the time to enter here is (once again) in UTC. But your clock is in local time. So the user has to perform this conversion -- on paper or outside the app, presumably. The app should at least have the option of entering in local time, i.e. in the time that the ship's deck watch is set to. Okay fine, you say, but these are all small-to-medium-sized problems compared to looking up numbers in the nautical almanac and sight reduction tables. So, just perform the time zone conversion and move on. Right? Enter another major issue: Once observations are entered, there is no (that I found, anyway) way to edit them. So you entered all this data, probably in DWT (because that is what makes sense and that is even what this app labels the field) but you realized too late the time is in UTC instead of local. Should be able to just edit the hours field, right? Nope. You have to enter the entire observation all over again. No, thanks. The hard part was done -- math, tabulation & plotting. With a dozen easy-to-change UI fixes, this program would be great.

DBG makes fantastic software. Astro Calculator does things I've been interested in for ages but had difficulty in finding apps to do the calculations. I love this app.