M42 Astro Pixel Processor 5 session stack

[turfpit]

I recently collected 5 sets of M42 data, in one session at 5 different exposures, with a view to experimenting with HDR images. I have just tried using the multi session capability in Astro Pixel Processor to create a single stack from the 5 sets. The data (collected in December 2019 using SharpCap 3.2, an Altair 183C camera and Altair 66ED refractor on a Celestron CG5 mount) was:

• lights: 15x120s, 30x60s, 30x30s, 50x10s, 50x4s

• darks: 20 for each of the above exposures

• flats & bias: 100 of each

Using the APP multi-session capability (sessions designated session_1, 2 … etc), darks were assigned to the appropriate lights; flats and bias were assigned to all sessions. The usual steps in APP were then followed. Here is the outcome:

M42_5-sets-of-exposures-combined.jpg (288.38 KiB) Viewed 2793 times

The resulting default file name can be quite long!

APP-result.JPG (15.71 KiB) Viewed 2793 times

Post processing in APP included:

• remove light pollution

• calibrate background

• calibrate star colours

• stretch from pre-defined list

• saturation

• contrast

• highlights

• crop

I did use GIMP for final black level adjustment.

Once the frames were all correctly assigned to their respective sessions, APP was used in the same way as for a single set of exposures.

In summary, 86 minutes total integration time of M42 with some exposures being 120s and the resulting image not having a blown out core gives some interesting possibilities for future projects.

This seems to be a productive way to deal with objects with a large range of brightness - for example M31 and globular clusters. It might also save me having to learn about processing using layers.

Dave

[umasscrew39]

Dave,

This is fantastic!! I've never tried APP but hearing good things about it. In SC, do you collect individual darks and flats and then make masters of each in APP?

Bruce

[turfpit]

Bruce

Thanks. What surprised me is how easy it was to do (or maybe the 3 years of struggle are paying off at last).

Data capture steps:
15x120s lights
20x120s darks
30x60s lights
20x60s darks
30x30s lights
20x30s darks
50x10s lights
20x10s darks
50x4s lights
20x4s darks
100 bias
100 flats

Took around 2 hours and produced ~27.5Gb of data. Altair 183C is 5440 x 3648, each frame 38Mb.

APP load data steps:
load 120s lights and select multi-session, assign these lights to session_1
load 120s darks, assign these darks to session_1
load 60s lights and assign to session_2
load 60s darks and assign to session_2
repeat for 30s, 10s, 4s lights and session_3, session_4, session_5
load flats and assign to all sessions
load bias and assign to all sessions

APP processing steps:
calibrate
analyse stars
register
normalize
integrate

Then APP 'Tools' for post-processing.

The PC was at it for a while on a 16Gb, quad core Xeon workstation. All the settings in processing can be set at once, then choosing integrate will carry out all the processing steps in the list above.

Features in APP that have helped me improve my results are:

• Remove light pollution, calibrate background, calibrate star colour

• Predefined stretches to select from

The calibrate star colour has resulted in images which have retained star colours. The best example I have is on my Astrobin - the recent M27 was captured back at the end of August 2019. Look at the difference in the 2 images - same data, different post processing.

The APP site has some good video tutorials including downloadable data. I have spent a good few hours grinding through these. The idea of the sessions and assigning frames in APP extends also to narrow band where there is the additional capability to assign an RGB colour to a set of data.

As always, any new piece of software needs time spent in order to get the best out of it.

Dave

[umasscrew39]

Thanks for the info. I am using/learning PixInsight with good success. Some folks seem to like APP better as they say it is easier to understand and get better results with it. They might be right as PI is very complicated with a plethora of options and could easily take me a few years to fully understand, especially given the good nights to actually use it (of course, I can use practice data and keep watching the tutorials which are very good). I might take a look at it but to keep software hoping just adds to the frustration and/or delay of enjoying the capture and viewing of nice DSOs.

[turfpit]

I know what you mean about changing software. Word processing is the hardest change I ever made - WordPerfect (DOS) to Word (Windows)

The first time I saw a demonstration of PixInsight it was introduced as 'powerful' which to me translated as 'expect a steep learning curve here'. I might look at it one day if I have a specific requirement.

APP has given me a good return on a relatively small investment in learning effort. I am only just scratching the surface of the application - I still have to get into LRGB, narrowband and mosaics. I reckon I could show someone how to process the image above, which is from a one shot colour camera in half a day.

[BlackWikkett]

Very nice results, APP is definitely on my short list of imaging apps to try. Thanks for the info!
-Chris

[turfpit]

Cheers Chris. The video tutorials are a good place to start. It would be possible to take the results of a Live Stack and refine it with the APP tools (which are designed to process an Astro image).

As for the M42 image, I will only be satisfied (possibly) when there is nebulosity between M43 and Running Man.

Dave

[mAnKiNd]

Wonderful image Dave!

[turfpit]

Thanks Minos.

I wonder if it is a technique that would work with your mono/OSC camera projects?
https://www.astrobin.com/306255/0/

Dave

[mAnKiNd]

Cheers Dave, I'm constantly evolving my thinking of how to optimize dual-shot astrophotography with mono/osc cameras and have some exciting new ideas I'll be sharing results with hopefully soon. The above work of yours is very intriguing indeed and I'll surely be taking a closer look.

Thanks
Minos