Hi Ronald, No need to apologize nothing in your post seemed wrong to me.
I agree that the calculator can produce exposure times that are beyond reasonable given limitations in equipment and conditions. With extreme inputs, in very dark sky , a fast optic, and narrow band filters the calculation might be so long that it would only be viable within the arctic circle in Winter,
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To reduce exposure time, my first recommendation is to consider a reduction in gain on the camera. Raising the camera gain, will typically reduce the read-noise, and result in a lower exposure time, (but usually at the cost of losing some dynamic range). However, some cameras have an electronic switch that changes the read mode. In these cameras, you will notice a pronounced step in the exposure time graph. At the bottom of this step, read-noise is low, but dynamic-range would typically jump back up, (because dynamic range is effected by read-noise). So if you have camera that shows a step in the exposure time graph, you might want to push the gain up just slightly to the right of that step.
There is another way to force the calculation to go outside the range recommended by Dr Glover, His calculation uses an input called "Noise Increase %". This input controls the factor that is used to compute the balance between the noise from light pollution and the read noise in the camera (this factor is sometimes referred to as the "swamp factor"). Dr Glover recommended using 5% (or lowering to 2% if the exposure time is very short). But I chose to leave this input relatively unlimited so that users could get results for exposure times that meet their needs. You can think of the "noise increase %" as governing the relative amount of read-noise, so an increase in this input will lower the exposure time, (which results in a relative increase in read-noise in the image). Read noise is constant, so a shorter image will have higher amount of read-noise relative to noise from light pollution). So to reduce an exposure time you just need to raise the input value of the "noise increase %".
As you adjust the noise increase upward the exposure time will drop, but you will also notice that sub-exposure count will climb disproportionately, this is because shorter exposures are relatively more noisy, and so more stacking is required to achieve a similar final result.
As for the filter input for an OSC. With no filter, you would use a value of 300 nm. If you end up using a filter, then some analysis of the filter is required. For example, with my OSC on nebulae I use an Optolong L-enHance two-band filter, for this filter I input a value of 34 nm, (this value is arrived at by adding the widths of the two bands passed by this filter).