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https://undersouthwestskies.blogspot.com/2025/01/welcome-to-my-new-astronomyastrophotogr.html
And welcome.
Welcome to 'UnderSouthWest Skies'. Thanks for stopping by. I hope you find the experience worthwhile. This blog post has been written from my own 'beginner perspective' after doing lots of reading on various basic astronomy and astrophotography topics of interest to beginners. In getting my head around it all, I may have got odd bits slightly wrong; but, like you, I am on a leaning journey, so please forgive any unintentional errors. Also, just because I have gone down a particular road regarding equipment, it doesn't mean that I have chosen the 'CORRECT' route!
Meanwhile, clear skies to you. Take care and thanks for visiting Steve aka PlymouthAstroBoy
Getting my DSLR camera astro-modified
When I heard that after so many years, and over 2500 astro
conversions, Andy Ellis of ‘Astronomiser’ was hanging up his
tools – I immediately did some research and reached a decision.
My research was – ‘what are the advantages and disadvantages of astro
modifying my camera’ and I have sort of summarised my findings
below.
The decision? I am posting my DSLR to Andy ASAP, having got one of his last conversion slots. He came highly recommended and I haven't been able to find someone else in the UK at the moment who would do it. Ideally I wanted to wait another year or so until I was better at post editing but, as is always the case, I've decided to jump right in and get it done now. 😕
So, what is astro modifying a DSLR all about?
I have a Canon 800D. It is several years old now. It has become my astrophotography camera. I tend to use a compact Canon digital zoom for my daily photography as it is compact, easy to slip into a pocket on my travels and takes really good photos.
Now my Canon camera, like other Canons, has a fitted filter that cuts out swathes of red light at a particular frequencies (about 75% of the light in the red band I think) – and this can really affect the Hydrogen Alpha band of emission nebulae. Thus to have a better chance of capturing the red in nebulae etc, then I have to do lots of long exposures - making an astrophotography session, very long!
But, what is the science behind the astro modification?
I am going to defer to my go to guru on astrophotography, the one and only Alyn Wallace, who very sadly passed away last year. In his video which I have put in below and in his outstanding book 'Photographing the night sky' , Alyn sort of sums up the science as follows
"The Bohr model - electrons exist in quanitsed energy levels surrounding an atom's nucleus. An atom absorbs energy and the electrons may jump to a higher state - this is described as them being excited. Excited atoms drop to a more stable level and the excess energy is emitted as photons of light.
H-alpha emissions produced by hydrogen atoms happen when the electrons fall from the 3rd level to the 2nd lowest energy level. The photon of light emitted during the process has a wavelength of 656 nm, putting it into the deep red section of visible light"
So, what does this mean? Stock cameras only record 15 - 20% of the H-alpha light detected at the sensor. Remove the filter and the cameras red response gets improved by a whopping x4 in this Hydrogen Alpha band, thus reducing the amount of imaging time required. The mod will also improve my milky way photos, shots of star forming regions and enhance any hydrogen alpha in galaxies.
At least, that's what I understand thus far!
So, I am getting the rear filter removed. This is a UV/IR
cut and colour correcting filter so I am told. Hence its an ‘IR Mod’. They key
here is its removal stops the colour correcting bit which is where the 75% of
light loss occurs.
At least I think this is right. As always, I flag up my long-standing
caveat – I’m a beginner at astrophotography and so I may make mistakes, for
which I apologise! If you think I have anything wrong, drop me a comment and I
will correct it immediately. Remember, this is a blog written by a beginner,
for beginners!
Back to my astro-mod. I think Andy will remove this rear
filter and reposition the sensor to correct for the loss of the filter glass.
So, lets move onto the advantages
of doing this mod – I have
already raised a few:
·
Removal of the filter will allow more sensitivity
light to the Hydrogen Alpha band -
easier to capture faint red wavelengths!
·
Increased sensitivity means I can capture more
detailed vibrant images of DSO’s in shorter imaging sessions - more accurate
colours
·
I will be able to do better narrowband imaging
·
With shorter imaging time, my images should
suffer from fewer stars overwhelming the main DSO I am imaging
·
I can still use my existing DSLR lenses and Zenithstar 61ii small
refractor
Disadvantages of doing the
mod:
· My camera will now capture all images in the red spectrum and so I will need to make a custom white balance adjustment if I want to use the camera for daylight shots OR I can use a clip in astronomic OWB filter to compensate (although many report that this filter causes flaring if there is a bright light source in your image). I read somewhere that setting a WB of 2500K for daylight photography will work but only time will tell. I could do post editing WB adjustments but as I am already struggling with affinity photo already, adding to my woes seems daft! Basically day time and night time landscape shots will have a magenta tint!
·
an astro-modified camera might struggle with
capturing detail in bright objects like the moon due to its increased
sensitivity to red light.
·
For capturing lunar details or wide-field shots
with a high dynamic range, an unmodified camera might be preferable.
·
I may lose automatic focusing on my lenses (not
an issue for me as I tend to use them all in manual focusing mode at night)
·
The costs of the astronomic filter and
conversion
·
It will void my factory warranty (but that was
already out of date anyway)
·
I am going to get post editing frustration as I
will need to do colour corrections to my milky way landscapes – they will have
a purplish hue! So, I will need to re-write my cheat notes about post editing
work flow.
Is the modification worth doing?
Jury out on that as far as
I make out on various forums. For everyone who says yes, someone says no! Many
say invest in a tracker instead for any landscape photography and don’t mod the
camera.
I have decided to take the plunge. If nothing else, it will force me to master colour correcting techniques in Affinity Photo! Or I buy the Astronomik / Optolong OWB filter and use that.
Below are some of the videos I looked at:
Anyway, when the camera is back, I will do some test shots and come back and update this post with my findings.
Clear skies, have fun, stay safe out there at night
Steve
Postscript:
Well here we are a few weeks later and I managed to do several nights imaging whilst on a recent motorhome trip to the Isle of Purbeck area.
First thing to note, yep, there is a definite magenta tint to daytime/blue hour photographs. There is a horrendous tangerine tint to any night time shots in a Bortle 4 area!
Upside - the Ha gases definitely come through x 4 what they did when it was un-modded.
So here are the first test shots - single frames taken across the nights:
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