07 January 2019

DSP Mobile: Sky Conditions

Deep-Sky Planner Mobile Edition (DSPME) allows you to record the sky conditions when you observe. These conditions - darkness, transparency and seeing - play a role in calculating visibility models for different kinds of objects. The first two metrics are used to determine whether you can see extended object like galaxies, globular clusters and nebulae. The latter is used to predict whether you can split a pair of double stars. Note that these predictions pertain to visual observing, not imaging.

[Note: Screenshot for this post was made on a 7" Android tablet with the Diamond app style.]

Conditions: Darkness, Transparency and Seeing

The various Sky Conditions should be set for each observing session because these metrics change over time. In fact, they change constantly so you may want to change these several times while you observe.

Darkness is entered in magnitudes per square arcsecond  (MPSAS). This value is readily available from Unihedron's Sky Quality Meter. Naked-eye limiting magnitude (NELM) is also shown, and you can use it to estimate MPSAS. Lastly, the Light Pollution Atlas Zone color[1] is displayed for the MPSAS and NELM values These 3 values can be used together to provide an objective assessment of sky darkness to DSPME.

Transparency can be determined objectively from the aerosol optical depth (AOD) at your observing time and place, or you can use the subjective scale. AOD information is available from various services online, including IDEA[2].

Seeing is a well-known metric to double star observers. A value can be entered in a subjective scale which links a description to the Antoniadi and Pickering scales.

These sky conditions are required for some of the visibility models. Once you have entered all the required components (equipment, observer, conditions), you can use the visibility models in DSPME to help predict your observing results.

[1] The New World Atlas of Artificial Sky Brightness, https://cires.colorado.edu/Artificial-light

[2] IDEA (Infusing satellite Data into Environmental air quality Applications) is a NASA - EPA - NOAA partnership, https://www.star.nesdis.noaa.gov/smcd/spb/aq/ 

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