The Iris Nebula, also NGC 7023 and Caldwell 4, is a bright reflection nebula and Caldwell object in the constellation Cepheus. NGC 7023 is actually the cluster within the nebula, LBN 487, and the nebula is lit by a magnitude +7 star, SAO 19158.[1] It shines at magnitude +6.8. It is located near the Mira-type variable star T Cephei, and near the bright magnitude +3.23 variable star Beta Cephei (Alphirk). It lies 1,300 light-years away and is six light-years across.[2]Credit : Wikipedia
no star version (only PS minimum filter ) :
| Optics: | Celestron C11 @ f6,3 Optec Lepus reducer ; wide data : C11 hyperstar @ f1,9 |
| Mount: | Avalon M1 Fast Reverse |
| Camera: | SX H694 unbinning |
| Dates/Times: | 2016 |
| Location: | Viterbo, W. Herschel obs./ Forca Canapine |
| Exposure: | Lum : 340 min ( f6 ) + 174 min (hyperstar mode) RGB : Alessandro Milani . |
| Cooling: | avg – 5° |
| Acquisition: | Astroart, Sequence Generator Pro, PHD2, Avalon Star Go |
| Processing: | Iris, PS, PixInsight, CCD sharp, |
| SQM-L: | 20.2 |
| Note | um: 78% |