whats your lrgb mosaic workflow

[iwols]

hi all just about to try mosaics just wondered what your workflow is for lrgb imaging thanks

[ollypenrice]

This is my method. It isn't a 'quick and easy' one but we do specialize in large mosaics here and are aiming for the best we can get.

 

Stack all panels in L and RGB and keep them separate.

Edge crop them all and run them through DBE in Pixinsight.

Partial stretch in Photoshop (maybe half way to full stretch.)  Set the background sky to the same level in all panels.

Is this a very large mosaic or just a 6 panel or less? What follows is done to the L panels and the RGB panels separately for combining later.

Very large mosaics need a template to get their geometry consistent. A widefield camera lens image of the target area, resized upwards to the size of the projected image, can be used. It may look terrible but it's only used to determine the geometry and does not appear in the final image. APP will also make a very good template.

Smaller mosaics can be left to Registar (more of which in a minute, but start with a central panel as your reference image.)

In Registar, ether register all panels to the template or to a central panel. Calibrate the panels (one click) and save the registered calibrated panels for patching any artifacts which appear later.

Combine panels in Registar. (In very large mosaics it isn't practical to do this in one go so make blocks of 4 or 6 panels to be combined later.)

Take the combined image(s) into Ps and inspect them for artifacts, notably for lines at joints. (The Equalize function in Image Adjustments will highlight any latent joint lines brilliantly.)

If you have a visible joint take the registered calibrated single panel which covers it and apply it over the joint in Ps Layers, feathering it out where it isn't needed using the eraser.

Once the full image is clean give it its final stretch and processing.

Combine L and RGB.

 

A lot of work? Yes! 🤣 Tom O'Donoghue worked for about six months on constructing our 36 panel Orion  https://www.astrophotography.ie/

and I spent about 40 hours processing the 32 panel recently shot by Yves Van den Broek. https://www.astrobin.com/g82xf7/B/?nc=user

Don't panic, 6 panel mosaics are much easier.

Olly