AkastroidHow it works
How astrophotography processing works
The processing workflow from raw frames to a finished image, in the order it happens, and what each step takes to learn by hand. Akastroid measures your frames, runs the eight processing steps, and leaves the final adjustments to you.
Free to try with every feature: three processing runs and one export. No account needed.
The usual workflow, and this one
A common free-and-paid workflow uses six programs. Each is good at its job; each also has to be learned. Akastroid does the same stages in one application, with fewer manual choices.
A typical workflow
- Capturea few hundred light frames, plus darks, flats and bias
- DeepSkyStacker or Sirilcalibration and stacking, with a rejection method and its parameters to choose
- GraXpertbackground extraction for light-pollution gradients
- StarNet or StarXTerminatorstar removal, so the nebula can be stretched separately
- PixInsightstretching, deconvolution, masks and recombination
- BlurXTerminatorAI deconvolution, a separate purchase
- Photoshopfinal curves, colour and crop
With Akastroid
- Open the folderlights, with darks/, flats/ and bias/ beside them if you have them
- Processcalibration, stacking, gradient, colour and sharpening, chosen from your data
- Resultthe finished image, the linear stack if you want it, and a log of each decision
One application, with no export between the steps.
The longer workflow gives more control: masks and selective editing have no automatic equivalent. See the comparisons with PixInsight and Siril, which is free and very capable.
Step 1 of 3
Put the frames in one folder
Lights in a folder, and if you shot them, darks and flats in folders called darks/ and flats/ beside them. Nothing is renamed, converted or exported first.
What this normally costs you: Most tools want each set loaded separately, in a particular order, sometimes in a particular format.
Step 2 of 3
Drop it in and press the button
Akastroid reads the folder, works out whether it is looking at deep-sky frames or a planetary video, measures every frame and runs the whole pipeline.
What this normally costs you: Eight operations, each with parameters, in the right order, across three or four programs, with an export between each.
Step 3 of 3
Keep it, or change your mind
Every decision is listed with the number behind it, and each one can be overruled: frames put back in, the stretch pulled back, sharpening turned down. Then export to JPEG, PNG or 16-bit TIFF, or save the integration unprocessed and finish it somewhere else.
What this normally costs you: This part is the same in any program, and it is the part that should be yours.
What happens in between
Eight operations run between pressing the button and seeing the picture. You do not need to do anything during them.
Calibrate away what the camera added
Master darks and flats are built and matched to the lights by exposure and dimensions, then subtracted and divided out. Bias is used where it belongs. A missing set is reported once and the session carries on.
Throw out the frames that are ruined
Every frame is measured for star shape, sharpness, sky and trails, and graded against the rest of your session rather than a fixed standard. Each rejection names the fault. It will never drop more than 40% of a night, or all of it.
Align them on the stars
Asterism matching recovers both shift and rotation, so frames from an alt-az mount, which most smart telescopes use, line up.
Combine them into one image
Average, median, sigma or Winsorized clipping, chosen from how deep the stack is and how much the frames drifted, with the reason printed in the log.
Take the sky back out
Light pollution, moon glow and vignetting are modelled and removed while the sky keeps a real level, because a background subtracted to black looks wrong.
Set the color from the stars
The field is plate-solved and matched against 1.48 million cataloged stars with measured colors, and the white balance is fitted to what those stars are.
Stretch it so the faint parts are visible
The curve is solved from your own histogram, with bright cores protected so a nebula core stays a core rather than a white blob.
Sharpen and denoise by measurement
Deconvolution with a point spread function measured from your own stars, and denoising scaled to the measured noise of the stack. Both decline to run when they would do harm, and say which guard stopped them.
Why measuring beats asking
None of the decisions above are matters of taste. Which rejection method suits a stack is a function of how many frames there are and how much they vary, both of which are countable. How hard to deconvolve is a function of measured star width and signal-to-noise. Whether drizzle helps depends on whether the frames were dithered, which can be read from the frames. Where the black point belongs depends on what fraction of the image is sky: about 98% on a wide field, where the generic default is roughly three times too high.
Those are measurements people usually make by eye, after months of practice. Akastroid makes them from the data and leaves the look of the final image to you.
Nothing is invented
Statistical and learned methods are used to measure your data and choose parameters. No generative model runs, and no detail is painted in. Everything in the output comes from light your telescope collected.
Where to go next
- Deep sky: nebulae, galaxies and clusters from FITS, XISF or camera RAW.
- Planets: lucky imaging from SER and AVI captures.
- The Moon.
- Image Doctor: the twelve measurements behind frame grading.
- A first image, start to finish: the same workflow on real data.
Questions about the workflow
Do I need to understand any of this to get an image?
No. Every step above is measured from your frames and carried out without being configured, and every automatic control afterwards shows the value it chose, with the reason beside it. You can learn the workflow by watching it run on your own data.
How long does the whole workflow take?
A hundred-frame deep sky session takes under a minute on an M-series Mac. A 206-frame Seestar session measured 22 seconds, and 111 DSLR raws 70 seconds. A planetary capture of twenty-six thousand frames measured 82 seconds. Changing how the result is finished afterwards is instant, because the stack is not rebuilt.
Is this the same workflow for planets and the Moon?
The shape is the same and two steps differ. Planetary and lunar captures are graded frame by frame for sharpness, aligned in pieces to remove the atmosphere's local warping, corrected for atmospheric dispersion and sharpened with wavelet layers rather than deconvolution. There is no calibration step, because a video capture does not use darks and flats the way a deep sky session does.
What if I already know how to do this?
Then use it as the front half. Akastroid calibrates, grades, registers and integrates in a few minutes, and Save the stacked image, unprocessed writes the integration before any finishing is applied, so you can take it to PixInsight or Photoshop and do the part you want to do.
Does any of it happen in the cloud?
None of it. Your frames are read, processed and written on your own machine and nothing about them is ever uploaded. It works with the wifi off.