2018-09-26, 08:47 PM
(2018-09-26, 08:37 PM)theskyhound Wrote: In your Imaging Project is says "0 sec" for the Clear filter. I am updating the text here in the update, but what that means is that an SNR of 60 is not attainable for this object, likely because it doesn't get very high in the sky and the bright sky background. So by going ahead and scheduling, you are setting it up to fail, so to speak. So that's the first thing I see.
Got it ... I assume that you're referring to the Exposure Calculator dialog "Calculate required exposure time", but I had assumed it was reporting that as the requested SNR there was 100 ... since the main dialog is giving me a schedule of 62x1, should I always be checking the Exposure Calculator to make sure it's in agreement?
There are going to be (usllay small) differences between the Scheduler and the Exposure Calculator because their are subtle difference in how they waork, dur to their roles being defined in slightly different ways.
The "ideal" exposure time is often not the same as the exposure time that delivers the most SNR. The ideal exposure time is computed via a fairly well known formula. But this formula is limited by real world considerations that I does not include. What SkyTools does is to look at a fixed period of time. It tries different sub exposure times and takes the one that delivers the highest SNR, and this is often not the same as the ideal time. Also, you may have set up your Imaging System with a minimum exposure time of one minute. In that case, SkyTools will use 1 minute subs even if something less would increase the SNR.
There is a section in the Technical Reference of the Help about ideal sub exposure times, how they are calculated, and what the limitations are in real world applications.
Yep, I read the technical note and that makes sense ... but here my misunderstanding is, if I have different exposure times as reported in the main Scheduling dialog lower list box and then reported in the Exposure Calculator, assuming that I rejigger the values in the Exposure Calculator (SNR, total time, etc.) to match the project values, if they are different which one should I "trust" for the values to use?
Did I miss anything? If you have more questions, fire away.
Thx!