SH2-155_Bi-Colour_16-8-2018

**Note**

I've reprocessed the Ha luminance to tone down the stars and soften the image while keeping the detail around the cave.

 

Well I managed to image this over one night between 22:45 and 3:45. I was going to add more Ha/Oiii to reduce the noise but by the time I got a another clear night the moon was back. The Oiii was very faint and I had to stretch it to destruction which made it very noise. As there was no detail in the Oiii (all detail comes from the Ha) I used a Gaussian Blur of 20 which solved the problem.

 

Object Description:-

SH2-155 (Sharpless 155) the Cave Nebula is made up of a combination of areas of emission/reflection/dark Nebula. It lies in the constellation of Cepheus at a distance of approximate 2,400 ly with a visual mag of 7.7. The Cave refers to the area of ionized Ha where star formation is actively ongoing.

 

Notes:-

1. This is not very strong in Oiii so I used a gain of 200 to obtain the Oiii subs.

2. To get the colour neutral stars without halos I used a "Starless" Oiii and Ha images but used an Ha Luminance which include the Stars.

 

EQUIPMENT:-

Telescope Meade 6000 115mm and AZ-EQ6 GT

ZWO ASI1600mm-Cool cmos camera

Orion Mini Auto Guide

Astronomik 12nm Ha Filter

Astronomik 6nm Oiii Filter

Chip Temp Cooled to -20 degC

 

IMAGING DETAILS:-

SH2-155 Cave Nebula (Cepheus)

Ha Gain 139 (Unit Gain)

Oiii Gain 200

32 Ha subs@300sec (2h 40min)

22 Oiii subs@300sec (1h 50min)

Total imaging Time 4h 30min

Dithering

20 Darks

20 Flats

 

PROCESSING/GUIDING SOFTWARE:-

APT "Astro Photograph Tools"

DSS

PS CS2

Done