Workflow tutorial: using SIRIL 1.4 including GraXpert, Cosmic Clarity Suite Pro and Veralux python scripts

  Blogger isn't always the most intuitive platform to navigate - but it is free and simple to use and manage. 

To help you find information quickly on this blog, you can

• use the search bar using key words e.g. Asiair mini
• use the blog menu list by date 
• use this page which will be regularly updated https://undersouthwestskies.blogspot.com/2025/12/want-to-find-something-quickly-on-my.html
• visit my home page https://undersouthwestskies.blogspot.com/p/welcome-to-my-astronomy-and.html

Updates March 2026

More updates to my workflow in SIRIL - find them down the bottom of this original blog post

• SynQon Prism
• SyQon star remover
• Adjustable autostretch preview

Updates January 2026

The rapid development of Veralux Python scripts has been breathtaking this month. As a result I am adding some updates to this page. These can be found at the bottom of this original post - as a postscript. Any future updates will appear in the same place. Current updates include:

• Veralux Revela
• Veralux Nox
• Veralux Curves
• Veralux Vectra
• Veralux Alchemy
• Veralux Star Composer

This post was published 13.12.25

Optimal workflow using SIRIL with COSMIC CLARITY SUITE PRO, GRAXPERT and AFFINITY PHOTO

I have written a previous post about my SIRIL workflow which you can find here  https://undersouthwestskies.blogspot.com/2025/01/a-beginners-guide-to-using-siril-some.html

This post was updated early December 2025, late December 2025. 

In this post I 

·       share my more simplified, reorganised workflow - which is based on SIRIL vs 1.4, and the python scripts for Cosmic Clarity Suite (by Seti Astro), Veralux and GraXpert. 

·       Try to give notes and tips which will help beginners

·       Share some useful, helpful YouTube tutorials

So, let’s get stuck straight in to my latest workflow: PLEASE NOTE - screenshots will be added when I process my next image - so please bear with me until then 

NOTE: I am assuming you have a little knowledge of how to organise your images – if you are going to be using SIRIL – if you are new to SIRIL the jump down to the bottom to watch one or two of the videos first.

Below is a simple graphic image which simplifies my workflow approach: 

and here is a simple infographic I tried to design based on SIRIL and not using the latest cosmic clarity and veralux python scripts 

A.      Organisation:

1.      Organise your folders into one folder called SIRIL and then sub folders for – lights, biases, darks and flats

2.      Set your home directory top menu bar left hand side

3.      Choose scripts – siril script files  - OSC pre-processing.ssf  to start the stacking process

 

B.      Crop and gradient removal:

1.      Be in autostretch mode on bottom task bar

2.      Load results.fits file produced from your stacking script – find in your home directory

3.      Crop edges to remove stacking artefacts

4.      Tools – astrometry  - image plate solver  on the pop up window:

a.      In pop up window - search catalogue number; (S box = if southern hemisphere image); click metadata from image; check – siril solver, solution order – cubic, flip image, auto-crop for wide field, star catalogue auto, catalogue limit – auto.

5.      Background extraction – image processing – python scripts - AutoBGe seti

a.      use default settings in the pop up window initially i.e. sample points 100, polynominal 2 RBF smoothness – 0.1.  (L-Enhance note - Use degree 2 to avoid flattening extended Ha regions).

b.      On the pop up window – can opt to click add exclusion area – (this is what you don’t want extracted) – free hand draw in around nebula area to be excluded – if make a mistake – click clear selection and start again – then when ready click process

c.      Use undo/redo arrows to compare before and after to see the changes

NOTES: background extraction

1.      Can use GraXpert for BGE  – GraXpert uses AI model - don’t do denoise now just BGE – severe gradients <0.5; mild gradients >0.5

6.      If using SIRIL BGE – grid tolerance 3, squares off nebula and bright stars; click dither to on; subtraction on; polynominal – increase for very bad gradients – RBF tab – smoothing default 0.5

 

C.     Colour calibration:

1.      NOTE – must have done image plate solver before doing colour calibration

2.      Autostretch mode on lower menu bar

3.      Remove chromatic aberration – python script - aberration remover – can do now or after colour calibration – either

4.      Plate solve image – if not already done above MUST DO BEFORE COLOUR CALLIBRATION WORK  - needs internet connection - astrometry - image plate solve

5.      Colour calibration – image processing tab – colour calibration - Spectrophotometric colour calibration

a.      SPCC – needs internet – tick the following: average spiral galaxy, one shot colour, osc sensor – closest, osc filter – optolong L pro OR if narrow band – check narrow band box and enter your filter details ( L enhance details for table – see below; tick background reference to auto detection.

b.      Settings if using L-enHance filter - – wavelength : blue OIII – 500; Green HB – 486; red H-alpha 656.3 and BW – OIII green 24; red 10; Blue 24

 

D.     Cosmic clarity sharpening  before denoise

a.       DO BEFORE STRETCHING I.E. LINEAR DATA

                                                  i.      stellar = stars only; non stellar = background and other objects - do both stellar and non stellar on pop up window OR experiment using undo/redo arrows – use GPU, clear input directory, (stellar sharpening  - 0.5 default and play with slider; or move first slider to 0.20 to 0.25; non stellar slider to 0.80; non stellar strength to 3. Zoom in a check – use undo and redo buttons to see differences made

b.      OPTIONAL – could do DENOISE now – scripts – python scripts - CC denoise – use RGB channel; check GPU and Clear input directory.     ** New veralux silentium python script is also a denoise option - must be done on linear images i.e. before image is stretched. To get this new script - go to scripts tab and get scripts and then go down the list - select the veralux script bar and check the box at the end. NOTE: as of late december 2025 - note that under scriupts tab - veralux now has its onw heading

c.      Now find output folder in Cosmic Clarity home folder on C drive and delete files as you go.

** If you use the new veralux silentium denoise script - I tend to use the default settings. when the preview box appears - it shows the settings in effect. To see the original image just press and hold down the space bar. the red box on the preview screen can also be moved about and acts as a zoom in function - so drag and drop it to the area you want to focus on. 

E   OPTIONAL stretching now – using Veralux hypermetric Stretching  NOTE – SEE F BELOW BEFORE DECIDING

a.      MUST DO PLATE SOLVING AND SPCC COLOUR BEFORE HAND

b.      Linear view – then Scripts – python scripts – processing – Veralux hypermetric stretching

c.      Settings for pop-up window:

a.      Processing – ready to use

b.      Sensor calibration – top one or canon 600d or 709re recommended.

c.      Click live view – use mouse scroll wheel to zoom in and out

d.      Target background – start 0.10 (0.2 is default) (lower the number the more contrast and darker the image – higher the number the less contrast and brighter the image)

e.      Log D – strength of stretch – leave at default 2.00

f.        Click auto calculate

g.       Protect B – how protected stars are during stretch – leave on default

h.      Star core recovery – leave default 3.5

i.        Process

j.        Make adjustments and experiment with setting inputs until happy

k.       If over saturated use the slider – but RECOMMENDATION IS DON’T TOUCH THE SLIDER – chromatic preservation colour one  - after alteration click auto calculate again

l.        Can also now apply curves transformation if image looking too washed out etc – or wait until starnet

d.      If choose scientific – then after do series of transform curve stretches in siril to bring up contrast and colour – s curves to raise darks, MT and HL’s

F. Star removal: I always DO BEFORE STRETCHING so I'd do section E above AFTER doing the starnet separation

1.      Optional first step: Image processing – star  processing desaturate stars

2.      Image processing – star processing - Starnet – tick prestretch in pop up window

3.      Stretching starless nebula – keep linear below in bottom menu

a.      OPTIONS: either Veralux hypermetric stretch as above OR Cosmic Clarity statistical stretch – see below

                                                  i.      Statistical stretch – in linear mode - target median 0.11 for anything not filling entire frame; normalise- no curves adjustment; if fully fills frame target median at 0.25 starter.

                                                 ii.      Stretch until: - Nebula structure is visible      Background is not clipped   Stars not blown out – NB if done colour correction already must check linked stretch box.
Now the image is nonlinear and ready for detail work.

b.      NOTE – CAN STILL DO OLD WAY IF DESIRE – SEE BELOW:

                                                  i.      OR – asinh stretch first followed by HTF stretch –  (HTF stretch using lhs and middle triangles or placing points on curve line to get shallow s curve  - watch clipping % - ensure no clipping of data –  ( can use ROI – draw box on part of nebula – right click select |ROI – select ‘set to selection’ and do adjustments; to remove – go back to menu and click ‘clear ROI’

                                                 ii.      OR Can also retry with curves adjustment ticked – try boost slider at 0.5 – the greater the boost the more contrast and fainter detail at expense of more noise and artefacts - 

                                               iii.      OR can do curves transformation – tiny iterative changes and repeat image processing – stretches – curves transformation – click on line and drag up or down – aim shallow s curve – don’t clip data – make very small adjustments – repeat gently LESS is MORE 

EXPERIMENT WITH EACH UNTIL HAPPY – use undo/redo arrows

4.      Complete denoise now – scripts – python scripts – processing – cosmic clarity denoise Denoise

a.      In pop up windopw - full strength – do zoom in and undo/redo to check difference

b.      alternative is denoise in siril  - if using GRaXpert – default stretch 0.5 so try 0.8

 

(NOTE – could try  SETI ENHANCER if you have it downloaded — Star Control, Detail Boost, Color Punch at this stage -
Load the denoised stretched image into SETI Enhancer.

·        Star Reduction - Use after stretch, not before.   Strength: 10–30%    Helps separate the nebula from crowded star fields      Avoid “donut-shaped” stars—dial back if seen

·        Nebula Detail Enhancement   Use:   Local contrast      Midtone sharpening    Texture boost
Moderate levels keep it natural.

·        Color Enhancement
Increase nebula saturation       Adjust hue sliders for Ha/OIII separation      Use vibrance before saturation
Avoid boosting star colours too strongly

·        Background Balancing
Use background equalizer if available     Ensure background is smooth and neutral
Remove remaining gradients)

G. Process starmask:

1.      Could Desaturate stars now – see above where outlined previously

2.      Can do Asinh stretch or  htf stretch – keep mild – use square and eyedropper Asinh Stretch:  Broadband: 5–15 L-Enhance: 3–8    Black point: 0.001–0.003   

3.      If doing GHS: Stretch: 0.8–1.2     Midtones:  Broadband: 0.3–0.5  L-Enhance: 0.2–0.35

Stop here.  Do not adjust saturation, HDR, clarity, sharpening. OR

4.      Could Reduce star size now – image processing - morphological transformation – selection – strength 5 – 20%

5.      Optional Slight saturation boost  - image processing – colour saturation: do globally

H. Star re-composition:

1.      Image processing – star processing – star re-composition

2.      On pop up histograms - RHS is starmask; LHS is starless

3.      Do black point adjustment to starmask to reduce number of stars

4.      Adjust blend to avoid halos and bright stars – inspect fine details – zoom to check edges

5.      Final noise reduction – optional light GraXpert or cc denoise – avoid over-smoothing background or killing faint dust

Final tweaks:

1.      Vibrance, colour balance

2.      Final cropping/rotation  to choice

3.      Green noise check – SCNR (Green Noise Removal) – BEST = SIRIL   Broadband: Strength: 0.60–0.75  L-Enhance:  Use none or mild (0.20–0.35)      OIII contains green, so don't destroy it.

4.      Export 16 bit TIFF

PS Videos that I found useful: 

Look for AstroIslander's part 2 and 3 as well 

Updates January 2026

The rapid development of Veralux Python scripts has been breathtaking this month. As a result I am adding some updates to this page: 

1. Here is a revised work flow that I have been using, based almost entirely on the Veralux suite in SIRIL. It is mainly 'narrowband imaging' orientated. (PS note additions to workflow below the flow diagram - Riccardo is producing new veralux scripts very rapidly and keeping Rich at Deep Space Astro very busy in video production) 

2. NARROWBAND WORKFLOW USING VERALUX SCRIPTS

This is a new work flow I am trying after using my Optolong L-enHance filter

BASIC WORK FLOW ORDER: start of January 2026

•      Crop
•      Plate solver 
•      Scripts - siril scripts - AutoBge 
•      scripts - siril scripts - CC sharpening 
•      Starnet removal - tick pre-stretch box
•      On starless image in linear mode - run Veralux Alchemy (see notes below) 
•      Complete Veralux Hypermetric Stretch and possible follow up > image processing - stretches - curves transformation to brings darks down slightly and brighten slightly highlights ) shallow 'S' curve) 
•       SAVE image
•       OPTIONAL: Image processing – filters – CLAHE (toggle preview on/off; play about with slides) SAVE
•       Veralux star recomposer – load RGBstars; load veralux alchemy linear fit file
•       Python scripts – processing – HDR multiscale
•       Veralux Vectra colour grading
•       Possible final image processing - stretches - curves transformation
•       Finishing in Affinity Photo 

3. Some notes about Veralux Alchemy

 Alchemy is for use when narrowband imaging. It leads to proper channel normalization, mixing without destroying colour integrity and structure.            

Useful if you are using one shot colour camera and optolong L-enHance

DON’T DO COLOUR CALIBRATION BEFORE USING ALCHEMY SCRIPT

LINEAR ONLY – MUST BE USED BEFORE STRETCHING DATA

ALCHEMY

·          Select sensor or OSC preprocessing

·       Enable Quantum On Mixing box

·       Normalisation – enable BG neutralization; enable Auto signal Fit

·       OIII – boosts blue (double click slider returns to default)

Palette Mixer

·       Default grey box setting = HOO

·       Sliders do the blends – so note the %’s

·       Pseudo HOO – changes slider %’s (50% green)

·       HSO preset = 100% OIII

SELECT YOUR PRESET then play with normalization OIII  slider

4. Veralux Vectra notes 

Perceptual colour grading with LCH (Lightness, chroma, Hue) for final astrophotography polish

VECTRA is a final step tool  - smoother colour transitions, refined saturation, balanced tonal

MUST BE USED ON IMAGE THAT HAS BEEN STRETCHED

Use either at end of work flow OR before star recomposer

VECTRA

•       Two tabs – primary (RGB) and secondary (YCM)
•       Sliders for each – can shift hue and/or saturation
•       Enable vector scope box – watch vector scope when using slider as well as image change
•       Know which areas of image want to enhance in advance of use
•       Same for using saturation sliders
•       AIM: to do final colour work on image
•       Shadow authority slider – prevents background changes – most of time sits far LHS – can affect colour of image target – so use very tiny steps  - keep watching for background changes
•       Enable white star integrity on images with stars – disable on starless images 

5. Veralux Star Recomposer notes 

Adds stars back into starless image after Starnett++ removal – replaces star recomposition

1.       In pop-up window load starmask and load starless image

2.       Linear for most images except galaxies

3.       Sensor profile – canon EOS modern

4.       Use star intensity slider

5.       Profile hardness = stars pinpoint level – default = 6

6.       Colour physics = star colour intensity

7.       Advanced tab –

a.       Core – removes artifacts around stars

b.       Reduction – reduces star size

c.       Optical healing – reduces halos around stars to improve colour  

Update end of January 2026: 

New python scripts in SIRIL include - VERALUX - Nox, Revela, curves, 

Nox - is a new background extraction tool to go alongside graXpert AI, AutoBge and Sirils own background extraction script - use on linear data 

Curves - replaces the curves transformation image processing within SIRIL - a tonal mapping tool - use after your images have been stretched

Revela - is a contrast enhancement tool which brings out the finer details in major structures - use on stretched data and do before final star recomposition

The videos below explain more about each tool

Updates February 2026

This post looks at my progression journey in general post editing skills from when I first started astrophotography. 

https://undersouthwestskies.blogspot.com/2026/02/what-does-progress-look-like-in-your.html

 What does progress look like in my post editing skills using the new veralux suite of tools in SIRIL 1.4?  

My workflow continues to adapt and develop as new tools appear - here I have integrated Veralux Nox, Curves and Vectra into my workflow, summarised in the diagram below. 

I also used this workflow order to reprocess some old data from 2024 - M45 Plaiedes. Transformative, game changer is all I can say. Find out more here at: 

Update March 2026

Three new videos for new python scripts - find them below. Where do they go in my work flow above? Good question! Basically autoscrtech preview - I would use on my starless image as a potential first stretch. SyQon star remover replaces starnet ++ and SyQon Prism denoise I use on linear data of tghe starkless image BEFORE sharpening and/or deconvolution. 

Here are the Videos from Rich.....

And I have as a result also now updated my workflow - it has minor adaptations for narrowband vs broadband tagets but essentially its this below: 

imaging tutorial: Beginner’s Guide to Camera Setup & Technique for Meteor Photography

 Blogger isn't always the most intuitive platform to navigate - but it is free and simple to use and manage. 

To help you find information quickly on this blog, you can

• use the search bar using key words e.g. Asiair mini
• use the blog menu list by date 
• use this page which will be regularly updated https://undersouthwestskies.blogspot.com/2025/12/want-to-find-something-quickly-on-my.html
• visit my home page https://undersouthwestskies.blogspot.com/p/welcome-to-my-astronomy-and.html

Beginner’s Guide to Camera Setup & Technique for Meteor Photography

If you’re anything like me, you may be feeling a little frustrated recently. I headed out to capture the Leonids a few weeks ago and was completely defeated by thick cloud cover. Now I’ll be waiting impatiently for the next decent shower - the Geminids - in December. At least the nights will be longer and darker by then. And this year, 2025, the moon will be just past the last quarter - so, not so much of an issue. Controllable! 

But if you’ve never photographed a meteor shower before and want a solid, beginner-friendly guide, read on. This will walk you through everything from location scouting to camera setup and even how to composite multiple meteors into one stunning final image.

Geminids - copyright PhotoPills website 

 Lets start with some basics - what is a meteor? 

They are bright flashes of light that move quickly across the night sky, caused by pieces of dust and debris from space entering the atmosphere - where they slow down and burn up. Meteor showers are periods when there are a larger number of meteors, normally because the Earth is moving through a trail of debris left behind by a comet or asteroid. 

So, this December, where should you be looking to catch a glimpse of a Geminid meteor or two? 

The Geminids emanate from the constellation Gemini. Look for the two bright stars Castor and Pollux. Find Orion - locate Rigel and Betelgeuse - draw a line from Rigel to Betelgeuse and keep the line going for the same distance to find Castor and Pollux. This is where the Geminds will appear from. 

Location: Finding the right spot is half the battle in meteor photography. Look for:

·       A dark sky site ideally bortle 3 or darker – the darker, the more fainter meteors you’ll catch

·       Big open sky view, especially to the sides of the meteor shower’s radiant. The wider the unobstructed sky around you, the better.  

·       Aim your camera 50 – 60 degrees above the horizon – it avoids the murky lower atmosphere and keeps star trailing manageable.

·       Cover at least 40 – 60 degrees in all directions from the radiant – Meteors fan outward; they won't appear right on the radiant itself. On the other hand, if you do aim towards the radiant, you will get shorter trails but show clearly how those trails appear from a single area of the sky.

·       Best time - typically after midnight until dawn, when the radiant is higher and your side of Earth is hitting more debris.

I'll add a note of controversy here which I will pick up again later - but you need to decide whether or not to include a foreground. You maximise your chances of catching a trail if you don't. On the other hand, foregrounds provide a beautiful context to a meteor trail. 

 

Equipment: you don’t need high end gear but there is some basic kit that makes it easier:

·       DSLR or mirrorless camera with manual controls

·       Wide angle lens (14 – 24mm) – I use a Samyang 14mm f/2.0. Wider = more sky = higher chance of catching meteors.

·       Sturdy tripod – keep it at mid height for stability and easy access to your camera controls

·       A programmable Intervalometer with 2” gap between exposures – prevents buffering issues and reduces sensor heat. One that is ‘lockable’ is a bonus.

·       Dew band – to stop your lens fogging

·       Plenty of batteries + memory cards - Continuous long exposures drain batteries fast and eat storage. Every hour or so when you re-align your frame (see below) – check your SD card, batteries and dew bands – you don’t want them running out or ‘fogging’ building up on your lens.  I tend to use a dummy battery powered by a large power bank in my camera – eliminating the ‘battery’ worries.

 

Framing your shot: Composition matters—beautiful images come from more than just catching a meteor.

If shooting sky only:

• Some astrophotographers try to keep the radiant in one corner of the frame.
  Meteors streak outward across the sky, so you want surrounding space. I centre my camera at around 60 degrees above the horizon and then decide which cardinal direction I will focus on. I then orientate my camera – by ensuring the long axis of the frame points back towards the approximate radiant position.
• If you choose the ‘long-axis’ orientation method above, remember to realign your frame every hour or so, as it will have drifted off alignment.
• With an ultra-wide lens (14 mm), don’t zoom or crop—you want the maximum sky coverage.

If adding foreground: A well-chosen landscape element can add scale and visual interest – but remember, at the sacrifice of sky area

• Include trees, hills, coastline, or architecture to give scale and grounding.
• Mind the balance of light vs. darkness—too much empty sky can feel flat.
• Try test exposures before peak activity to refine your composition –
• Use the rule of thirds loosely: horizon on the lower third if you want the sky to dominate, and foreground or radiant near intersection points for a dynamic feel.
• A diagonal element (a tree, rock formation, or shoreline) can help lead the viewer’s eye toward the radiant.

Helpful tool:

·       Use a star-chart app (Stellarium, SkySafari, Star Walk) to locate the radiant before you start shooting.

 

Copyright: stargazing website 

Camera settings on the night: These settings are a solid baseline and work for most cameras.

• Shoot in RAW. You’ll want maximum flexibility for noise reduction and colour.
• Manual mode for both exposure and focus.
• Long exposure noise reduction: OFF. Otherwise, your camera takes a dark frame after every shot, halving your chances of catching meteors.
• Drive mode: Continuous shooting.
• Aperture: As wide open as your lens allows (f/2.0–f/2.8).
• Focus:
• Set lens to manual focus.
• Use live view to zoom in on a bright star.
• Adjust until it becomes a precise point.
• Tape the focus ring to stop accidental movement.
  (Infinity marks are notoriously unreliable.)
• ISO: 800–3200. Darker skies allow higher ISO without too much noise. I normally start at 1600 on my test exposures – which I tend to do for 20 – 30”.  Overexposed? Shorten exposure length and take another test shot.  
• Shutter speed: 15–30 seconds.   Longer exposures increase meteor-catching probability but introduce star trailing. Start with 20–25 seconds, zoom in to check star sharpness, and tweak as needed.
• Capture as long as you can -  Once the setup is dialled in, shoot continuously for 1–2 hours without moving the tripod.

 

Practical Tips for a Successful Meteor Session

• Be patient. Even during peak showers, meteors can come in clusters with quiet gaps.
• Avoid moonlight. A bright Moon washes out faint meteors and reduces contrast.
• Let your eyes dark-adapt for at least 20 minutes. Use a red torch to preserve night vision.
• Check weather and cloud forecasts (satellite maps are best).
• Dress warmly! Layers, gloves, hat, and insulated boots are your best friends.

When you get home, check your images – download them to your laptop/computer and go through each frame – looking for that trail! Don’t get confused with plane or satellite trails!  Rename each ‘genuine’ meteor trail by just adding a prefix letter at the end of its file name.

 

How to Capture and Composite Multiple Meteors

Capturing a single meteor is exciting—but capturing dozens in one polished image feels magical. Here’s how to create that iconic composite.

Step 1 — Capture your sequence

Shoot hundreds of frames as described above. If you’re lucky, 5–15 will contain visible meteors.

Step 2 — Choose a base image

Pick your cleanest frame:

• sharp stars
• no meteors
• minimal cloud
• well-exposed foreground

This becomes your master background.

Step 3 — Prepare your meteor frames

In your editor (Affinity Photo, Photoshop, etc.):

• Open each RAW file. In affinity photo – that would be in ‘develop persona’
• Apply minimal corrections: lens correction, light noise reduction, exposure, and white balance.
• Do not crop or rotate—perfect alignment is crucial.

Place each meteor frame as a full-size layer above the base image.

Step 4 — Blend with “Lighten” mode

Set each meteor layer’s blend mode to Lighten.

This reveals:

• the meteor streak
• any stars brighter than those in the base frame

…and hides the rest.

Step 5 — Mask out unwanted areas

For each meteor layer:

• Add a mask
• Use a soft brush at 20–40% opacity to remove clouds, plane trails, or light pollution.

Step 6 — Final polish

• Global exposure + white balance adjustments
• A gentle noise reduction
• Curves adjustment to add subtle contrast
• Optional: light high-pass sharpening on meteor layers

When everything looks natural and cohesive, export your final image.

 

Final Thoughts

Meteor photography mixes patience, technique, and a bit of luck—but when everything comes together, the results are unforgettable. With preparation, the right settings, and a thoughtful workflow, you can go from “I hope I get one meteor” to creating stunning composite images full of movement and wonder.

 If you want further information about shooting meteors - i found this presentatiuon by PhotPills vcery useful: https://www.photopills.com/articles/meteor-shower-photography-guide#step12