Astrophotography from city centres, is it possible?
Yes, but with some tricks.
I live in a heavly light polluted area, in the middle of Naples, Italy, as you can see from the satellite images below it’s one ugly lightpolluted place, but this never stopped me from doing astrophotography.







 

                                               
                                                          
                                                                                            Naples, Bortle 8-9 SQM 17.5-18.00
One hell of place to do astrophotography uh? I started 3 years ago with just an entry level reflex modded Baader and a bicolor L enhance filter.
Take a look at this Pacman Nebula , only 5 hours of exposure with 180” subs:








 

                                   
                                      



                                                       
                                                        Celestron C8 XLT at F 6.3 with Canon 1100d Baader and L enhance filter

Looks cool right? If you are new into this hobby you might find this picture great, well for being taken under this conditions ( and on a balcony that i will show later in this review)  it is promising , but with just a reflex
I was stuck to 180” exposure due to light pollution and I couldn’t capture more signal.

                                           HOW EVERYTHING CHANGED
On August 2021 i got my first monocrhome camera the QHY294M PRO and from that point, the light pollution was not scary anymore.
That’s the main trick! A good sensor capable of taking long exposure pics without saturating the histogram , with a good full well capacity and a good quantum efficiency and good readout noise as you can see from the graph below:










In my opinion it’s one fo the most affordable monocrhome camera to get.
Why monocrhome instead of color OSC camera?
Well altough you can still have great results with an OSC camera, the monocrhome camera will use all of its sensor, without a Bayer filter that will split your signal in on part of Red ( R ) two of Green ( G ) and one of Blue ( B ) to give your color image, so if you are using and H-alpha filter (wich activates de “R” ) you will be using only 25% of your sensor, if it was monocrhome it would have been 100% , with way more signl than a color camera.
I know, It is expensive but from another point of view they cost less than a professional DSLR.
This the location where i shoot:












 

Very awful right? Some people says that I’m crazy to shoot from there, traffic noise, lights everywhere, only 3 hours at night of sky available and only pointed to North… but this is the result of IC1396 that you see on my laptop screen:






















and this image could be way better with better postprocessing skills.
Ok the sensor helped me out a lot but for “shooting stars” in city center it’s not the only thing you need.

Choosing the right object and NarrowBand filters:

The monocrhome camera is great, but it will not help while shooting galaxies, reflection nebulas or dark nebulas. These kind of objects will suffer too much the light pollution since they emit on all the lightspectrum and we cannot filter the signal whitout cutting it a lot ,since filters like L-pro or similar are kinda useless in cities. I have tried using CLS filters to shoot some galaxies, but the signal was too weak and the filter cutted some wavelenghts too much.
So if we cannot these objects what can we do? Emission Nebulas , the ones full of HII, OIII and SII will do the work then.
So in my opinion is important to have a SHO set, or at least HII and OIII narrowbands filters.
They will cut out the most of the lightpollution, and the H-alpha will be stunning, trust me:











 

   
                         
                         600” (autostretch) sub shot with H-alpha Baader 7nm filter , QHY294M Pro and 70ED refractor , on the same balcony


as you can see the SNR is great on this image, buti t will not be that great with the OIII filter, because the OIII is located on a wavelenght that suffers the light pollution a lot, buti f you combine it with the SII filter you can combine everything into a Hubble Palette (SHO) like this:




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                                                                             IC1805 Hubble Palette, 10h HII, 4h OIII, 3.5h SII

The Hubble Palette really helps on having really good and clean images. I had a few troubles while shooting only a bicolor image (HII&OIII) because as I said the Oxygen suffers a lot the light pollution, so i had to spend much more exposing time focusing on OIII (like 2 or 3 times more) to have a good image with low noise





















                                                                         
                                                                   Celestron C8, HII 7nm & OIII 8.5nm Baader, QHY294M Pro



Of course you can do that but in this picture the I spent 9.5 hours on the OIII and only 3,5 hours on the HII, so you ahve to take extra time on the Oxygen.
I raccomend going for the Hubble Palette because it's easier to have a clean image since the OIII doesn't have to cover 2 channels ( G&B ) so the SII can help it giving a nice and clean with low noise image.

So hope this helped some of you, some concepts may be of common knowledge but since I'm living in this hell of a place for astrophotography I hope that anyone who is worried on their results and lives in place like mine can have a little help on how to approach the lightpollution!

Clear Skies! 

                                                                                                                     
          
                                                                                                                     Giuseppe Mauriello