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Exposure calculator
i think i might need some help. i am trying to learn how to use exposure calculator with a system made by a borg 107F3.9 and a QHY163M. What i am trying to pull out is the "general plan". Let's say, i wish to do a LRGB image with a global snr value of 90. how many subs (and how long) i have to do for each filter, given gain settings and sky quality?

i am always retriving 5000+subs of 1 sec or similar from exposure opportunities..

I think you're trying to evaluate the exposure requirements for each filter, correct? In the 'calculate Required Exposure Time' section:

Select the desired SNR, turn off 'Auto' mode by clicking the 'Auto' button, enter a max sub-exposure time (try something in the 1-5 min range for starters, see what the calculated exposure time is. Adjust the max exposure time if needed.

Repeat the process for each of your filters.

Remember to adjust the Binning for the color filters to an appropriate setting.

The brightness of the target object will affect the results.

Does this do what you want or have I misunderstood your question?

Phil S.

It is very important that every aspect of your imaging system and location be set up properly. So if you are not getting the results that you expect, it is likely because something isn't set up correctly. A one-second sub exposure is very short under most conditions, but if you have a bright sky (location sky brightness setting) or moonlight, fast optical system, and certain cameras, this might be the correct result. But as I said, such short exposure times are unusual. So make sure to check your settings and that the moon isn't up.

More importantly, you didn't say anything about your target object. Is it a bright star? Bright objects may require a short exposure in order to avoid saturation or clipping of the detector.

Where are you seeing these short exposure times? Note that the ideal exposure time listed in the table has limited value. Let the calculator part automatically compute the best sub exposure time.

Lastly, the Exposure Calculator is there for you to experiment with or to make decisions for special cases. In practice, you should use the other tools. When making an imaging project, the Exposure Goals tab has a table that summarizes how long you will need to expose to reach your target SNR under ideal conditions.

Ultimately it is the Scheduler or Real Time tools that are used to calculate the sub exposure times when you are ready to start observing.
Clear skies,

SkyTools Developer
Sorry for being late, internet was down here yesterday.

i will do some more test this eveneeng, i think i have to adapt to a different workflow, becouse ST is choose and forget-made, that it is not bad at all, but i have to export sequences on other software.

i have tested the manual settings and gives back different numbers. i will be more detailed in some hours. i think it is me that has to adapt, my current thinking is:

"given the ideal condition of no moon and perma-night, how many time does a project takes?"


M78 (example) project requires "X"hours, with shots of "Y" min/secs gain "Z", divided in ABCDE for Lrgb to reach a snr of "H" and a skyflux of "I". So i can plan to go to mountains one day and do L & R only and another travel for the rest..
67940 (random number) poses of 1 sec is not an option  Big Grin

The software does what i say up here, i think it is just a matter of time to learn from me.. if i would have an observatory i would just set and forget.. (it would split automatically between hours, moon and nights)

More to come... with screens. i had attempted M78 and M42 since they're on the good part of my sky here in venice Smile

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