## Sky Background Calculator and Quantum Efficiency

A place to post guides, instructions and HOWTO documents on the use of SharpCap and Astrophotography in general
Forum rules
Please only post content that you have created in this form.
Tutorials should be either in PDF format as an attachment or written in the first post of the topic. Links to video tutorials you created are also acceptable.
Topographic
Posts: 11
Joined: Fri Nov 15, 2019 4:23 pm
Location: Pays de Serres en Quercy

### Sky Background Calculator and Quantum Efficiency

Hi

I am using the ZWO ASI 183MC Pro, the only figure I have for QE is 84% (mono sensor). Do I enter this and then select the colour button?

Thanks

David
Posts: 6621
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

### Re: Sky Background Calculator and Quantum Efficiency

Hi,

Yes, by selecting the colour option you're effectively allowing for the fact that each colour filter lets through a bit less than one third of the light available. The underlying QE is unchanged, although you do have to remember that the 84% value as a peak value at a particular wavelength and the average across the whole of the visible spectrum will be smaller.

Cheers, Robin
Topographic
Posts: 11
Joined: Fri Nov 15, 2019 4:23 pm
Location: Pays de Serres en Quercy

### Re: Sky Background Calculator and Quantum Efficiency

Robin

I assumed a lower than 'peak' efficiency (-10%).

thanks

Daid
stephen2615
Posts: 17
Joined: Sat Mar 09, 2019 11:10 pm

### Re: Sky Background Calculator and Quantum Efficiency

Hi Robin,

I was wondering about what impact the moon has on the sky background calculator. Surely a full moon would have a significant impact on the calculations. I have a cousin who lives in a the darkest skies area I know and I try to take advantage of this location compared to my Bortle 5 skies. The full moon completely changes what I can see so this suggest the calculator should be adjusted for the moon.

regards

Stephen
Posts: 6621
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

### Re: Sky Background Calculator and Quantum Efficiency

Hi,

Yes, definitely. The full moon in the sky near to the target that you are trying to image is equivalent to some pretty significant light pollution. The online calculator really only give some guidance – to do this properly it's best to use the smart histogram functionality in SharpCap to actually measure the background brightness level.

Cheers, Robin
stephen2615
Posts: 17
Joined: Sat Mar 09, 2019 11:10 pm

### Re: Sky Background Calculator and Quantum Efficiency

Hi Robin

Thanks for the response.

I will have a look at the smart histogram functionality. I have so much going on in setting up the process I almost need a checklist. I am trying to get a good spreadsheet together to give me ideal exposure times.

Regards

Stephen