NGC7023 - Iris Nebula


Hi All

This is my first image with my new Skywatcher F4 Quattro 8-CF, the image consists of the following

19x300S - Luminance
13x300S - Red
13x300S - Green
13x300S - Blue

All frames have 25 darks and 25 flats applied also

Gear Used
Mount: Skywatcher EQ8 Pro
Imaging Scope: Skywatcher Quattro 8-CF F4 Newtonian
Guide Scope: Celestron C80ED
Imaging Camera: Atik 383L+ Mono CCD Cooled to -20C
Filter Wheel: StarlightXpress 7x36mm USB Filterwheel
Guide Camera: QHYCCD 5L-II

Software Used
Image Acquisition: Sequence Generator Pro
Guiding: PHD2
Telescope Control: EQMOD

Image Processing:
Pre-Processing: Nebulosity 3
Stacking: Maxim-DL
Post Processing: Photoshop, HLVG and GradientXterminator



Nicely done all around, capture and processing.



Thanks @AjayNarayanan, not an easy target to process!


Really nice. Good job! We should have a ‘user submitted’ images page. SGP does such good work.


@mads0100 I honestly can’t remember imaging life without SGPro…well I did not have a CCD camera then


Agreed. When I first started I ran the gambit on software and after a fit of rage over guiding not working in some ‘other’ program, I decided to try SGP. I managed to get SGP running all night long after an hour… I was almost in tears! :smiley:

I’d recommend SGP for just about every install these days. If you read the manual, you will get it running.

Take care,


An excellent image well done, and a plus for the EQ8 which takes quite a bit of bad press in some quarters…



A couple of observations on your exposures. You didn’t give the binning so I will assume 1x1. Most cameras are more sensitive to green so you may be able to cut back on green exposures. On my camera, I find that if I do green at 80% of the other colors, it is almost color balanced. Since filters reduce the amount of light, it is often desirable to have longer exposures for colors than for luminance. A rule of thumb is to have the color exposures twice the luminance. So depending on the camera saturation your exposures might look like this
L300; R600; G480; B600 or perhaps L150; R300; G240; B300

Lastly, consider using PixInsight for processing.


@DesertSky I am using a Mono Camera, so it is not more sensitive to green light, only cameras with the Bayer Matrix are more sensitive to green light because for every R+B Pixel there is 2x Green

Why should I consider Pixinsight for processing?


Mono cameras do not have a uniform sensitivity across the color spectrum. See if you can find a spectral sensitivity curve for your camera and you will see the difference.

For bayer matrix cameras the extra green pixels translates into better green resolution not increased sensitivity. The sensitivity is a function of each pixel and does not increase with more pixels. However, like mono cameras the pixels may be more sensitive to green.

PixInsight is specifically designed for astrophotography processing and does a great job. With PixInsight you can do all your processing with one tool, and the price is quite reasonable. The only downsides are that it takes some effort to learn and it does not have painting tools like Photoshop.


When I stack the images using Maxim-DL, there is a factor screen where you specify the strength of the Red and Blue stack, so I see what you say about the 80% green exposures, but Maxim-DL does this already

As you said, Pixinsight may be good, but I have a workflow for processing which is not broke, so if it is not broke, why fix it :slight_smile: