Part 1: introduction of the Mosaic Tutorial – Milky Way to Rho Ophiuchi by Mabula

Data is courtesy of Stefan Lenz, Germany, and was captured in Namibia at the Kiripotib astrofarm.

Nikon D810a
Nikon VR 400mm F/2.8G
Sigma Art 135 F/1.8

This is a very extensive tutorial consisting of several parts.

  • Part 1: introduction
  • Part 2: calibrate, register, normalize & integrate the individual mosaic panels
  • Part 3: register, normalize, integrate the mosaic
  • Part 4: perform gradient/light pollution correction and
    background calibration to make a gray sky background
  • Part 5: star color calibration
  • Part 6: HSL selective color
  • Part 7: final stretching with the preview-filter

Part 1-3 deal mostly with how to create the mosaic from the individual exposures.

Overview of the mosaic composition. 5 panels were shot with the 135mm objective and 6 panels were shot with the 400mm objective.

Part 4-7 are about post-processing the mosaic integration to a final image

From Top Left to Bottom Right: Mosaic after integration without Multi-Band Blending (MBB) and without Local Normalization Correction (LNC). Mosaic after integration with MBB and LNC. Mosaic after integration with MBB, LNC and Light Pollution Correction, Mosaic after integration with MBB, LNC, Light Pollution Correction and Star Color Calibration, Mosaic after integration with MBB, LNC, Light Pollution Correction, Star Color Calibration and HSL Selective Color.
Milky Way to Rho Ophiuchi by Stefan Lenz & Mabula Haverkamp. This is the final mosaic of Stefan Lenz’s data as processed by Mabula in this tutorial.
Show at the top, we see M20, the Trifid Nebula in blue and Red/Pink. The large and bright Red/Pink/Magenta nebula below it, is M8, the Lagoon Nebula.
This is the spectacular Antares, Rho Ophiuchi cloud complex. Rho Ophiuchi is the bright star system located in the top blue reflection nebula, while Antares is the very bright yellow star in the yellow to orange nebulosity. And just to the right of Antares, you find M4, the Crab Globular Cluster.
M17, the Omega Nebula can be found on the top left. M24 the Sagittarius Star Cloud is to the left of the center.
IC 4592, the Blue Horsehead Nebula
Shown is the Pipe Nebula, which is the huge dark nebula in the shape of a Pipe

Part 1: Introduction

The dataset is a multi-focal length mosaic, using 2 Nikon objectives of 400mm and 135mm focal length. The 400mm objective was used to captured more detail in interesting areas of the total Field Of View. Imaged is a widefield area that contains part of the Milkyway and the spectacular Rho Ophiuchi, Antares nebulosity complex.

Most data was shot with ISO 800, some frames were shot with ISO 400.

The different mosaic panels:

135mm:

Panel 1: 7x100s, 3x500s
Panel 2: 5x500s
Panel 3: 6x500s
Panel 4: 5x500s
Panel 5: 1x300s, 5x500s

All 135mm data was calibrated with a Bad Pixel Map and a MasterBias

400mm:

Panel 6 : 10x100s
5x300s
5x600s
Panel 7 : 10x300s
8x600s
Panel 8 : 4x600s
Panel 9 : 12x600s
Panel 10: 7x600s
Panel 11: 3x600s

All 400mm data was calibrated with a Bad Pixel Map, MasterBias, and a MasterFlat

Some remarks, tips:
  • The most efficient and most robust way to register any data set as a mosaic is to first integrate the individual mosaic panels. Then register the mosaic using only the individual integrated panels.
  • This holds for other mosaics as well. Don’t try to create a mosaic out of 100s of indivdual frames. First create the mosaic panels.
  • To prevent integration/stack artefacts at the borders of the mosaic panels, use both Multi-Band Blending (MBB) & Local Normalization Correction (LNC) to reduce the amount of integration artefacts considerably.
  • The actual Mosaic integration needs to be done, using MBB & LNC as well to correct illumination differences and to prevent the well-known mosaic seams.
  • Regarding: Dynamic Optical Distortion Correction.In most cases, you can leave this disabled for the individual mosaic panel integrations. Only enable it if registration RMS is higher than 0.5 pixels and registration is visibly not correct. In the mosaic registration, you really need to have this enabled always.