8
Beginner's Astrophotography: Can I use my unmodified DSLR?
Discuss this article in our forums
Beginner's Astrophotography: Can I use my unmodified DSLR?
It is often recommended to modify DSLR's for deep sky photography. It may be one of the first topics a beginner comes across and sometimes the recommendation sounds like modding is an absolute necessity. There are good reasons not to do it, for example the camera is used for daytime photography as well or the budget does not allow either to have an existing camera modified or get a modified one. I don't want to go deeper into it. I'm also not opposed to modified cameras. I just would like to show what can be done with an unmodded relatively low priced DSLR if modding is not an option. All images have been taken from Germany under Bortle 4-5 skies from my backyard with an unmodified Canon T3i or T7i. Theses are sold under the name 600D and 800D respectively in Europe.
Near Earth Objects
Any object in close proximity to our home planet is a pure broadband object. Our natural satellite the moon is one and it can be imaged with a telephoto lens from a static tripod.
The Moon. Canon T3i, Sigma 50-500 at f/8, 1/80sec, ISO 100, single image
Taking a photo of the international space station is demanding and requires a long focal length, much longer than what was to my disposal. A modified camera however is neither required nor beneficial.
ISS. Canon T7i, GSO RC8 at f/6, 1/2000sec, ISO 400, 7 images
Comets light up and develop the fantastic tales when they are close to our sun. They too do not benefit from a modification.
Comet Neowise 2020.
Canon T7i, TS 65mm Imaging Star, f/6.5, 40x30sec, ISO 400
Star Clusters
Star clusters reside near or in our own galaxy. Older globular clusters contain old yellow stars that are not burning hot enough to make hydrogen glow. This holds for all globular clusters in the Messier catalog.
M13. Canon T3i, GSO RC8 at f/6, 29x2min, ISO 800
Some open clusters are located in hydrogen clouds and make the cloud glow red. We will see this in a bit. Others are not. The famous Pleiades reside in a blue reflection nebula that does not benefit from a modification either.
M45. Canon T7i, TS 65mm Imaging Star, f/6.5, 19x4min, ISO 400
The Double Cluster in Perseus comes without any nebulosity and little variation in star color. Still many regard it as one of the most beautiful sights in our night sky.
h and Chi in Perseus.
Canon T7i, TS 65mm Imaging Star, f/6.5, 31x4min, ISO 400
Galaxies
Galaxies consist of stars mainly but galaxies also have star forming regions that typically show strong Ha emissions. In some cases the galaxies are so far away that it is impossible to resolve such small regions from earth. For example all the galaxies in the Coma Cluster will probably have Ha regions but we cannot resolve them.
The Coma Cluster. Canon T7i, GSO RC8 at f/6, 158x5min, ISO 400
If a galaxy is nearby the Ha regions can be resolved. They show up as pink dots in the spiral arms. When imaged with an unmodified camera these dots are blue. This does not necessarily ruin the image. Galaxies often show plenty of color in broadband. The stars near the center are the oldest. Only if a star burns at low temperatures it can become old thus the center is often a yellow or golden color. New stars are formed in the spiral arms in areas of high density. Many of them burn hot which gives the spiral arms a blue color. Between the stars there is interstellar dust that shows up as brown clouds. So even without the Ha regions the images do not suffer from lack of color.
M51 and NGC 5194. Canon T7i, GSO RC8 at f/6, 88x7min, ISO 400
M101 and M33 are among the largest and brightest galaxies. Thus they are suitable for beginner setups with a moderate focal length.
M101. Canon T7i, GSO RC8 at f/6, 120x5min, ISO 400
M33. Canon T7i, TS 65mm Imaging Star, f/6.5, 41x5min, ISO 400
O-III emission objects
The emission line of double ionized oxygen is a blueish green or teal color. It can be picked up easily by any unmodded camera. Many emission objects are so dim that only a cooled astro camera can pick up the faint signal. But there are brighter objects. Often objects emit Ha and O-III. With an unmodded camera only little of the Ha is picked up. Unlike galaxies with only tiny parts of Ha now larger parts may be missing in the image. Does that mean you must not image it? When the central star in the Ring nebula in Lyra shows up you can be proud of what you have achieved in terms of good focus and good guiding.
M57. Canon T7i, GSO RC8 at f/6, 57x2min, ISO 400
M27. Canon T3i, GSO RC8 at f/6, 51x2min, ISO 800
Bright Ha emission objects
An unmodded camera is not totally blind at 656nm. As a rule of thumb removing the filter enhances the sensitivity by a factor of two or three depending on how the IR filter is designed. In photographic terms this is just 1 to 1.5 f-stops. There are plenty of bright Ha objects. Probably the most famous one in the northern hemisphere is the Great Orion Nebula. When imaged together with the nearby Running Man nebula an unmodded camera can even be superior because it dims the bright Orion Nebula down a bit so that the blueish running man appears brighter in the image.
M42 and Running Man.
Canon T7i, TS 65mm Imaging Star, f/6.5, 27x2min, ISO 400
But this is by far not the only emission nebula suitable for unmodded cameras. The Trifid Nebula comprises a blue reflection nebula next to a red Ha emission area.
M20. Canon T7i, GSO RC8 at f/6, 29x4min, ISO 400
Coming back to open clusters that may or may not be associated with an emission nebula. The Rosette nebula is famous example of a star cluster and a Nebula but not the only one.
Open Cluster NGC2237 and Rosette Nebula.
Canon T3i, TS 65mm Imaging Star, f/6.5, 71x2min, ISO 800
M8. Canon T7i, GSO RC8 at f/6, 43x2min, ISO 400
M16. Canon T7i, GSO RC8 at f/6, 51x2min, ISO 400
Large Ha areas in the Milky Way
This group overlaps with the last one. All the objects shown in the last section are located in the Milky Way. I decided to put the next objects in a separate group because they are so large that the images are powdered by stars. You can easily find 20,000 stars and more in one image. The size of the object allows to shoot them with a moderate telephoto lens in case you do not own a telescope. Most beginners are troubled by the amount of stars that distract from the nebulae. When the stars are reduced in size during post processing the objects show up more clearly.
Heart and Soul. Canon T7i, Askar FMA180 at f/4.5, 54x3min, ISO 200
Sadr region. Canon T7i, Askar FMA180 at f/4.5, 60x5min, ISO 200
North America Nebula.
Canon T3i, TS 65mm Imaging Star, f/6.5, 18x5min, ISO 800
Remarks
You can find many of these images on my website 'elf-of-lothlorien.de'. Many of them are composite images that contain Ha data from a mono camera. These have been reprocessed for this article without the use of Ha data. Of course there are more objects suitable for unmodded cameras like dark nebulae or planets but alas I do not have any image of those.
Conclusion
It is perfectly possible to take decent images of the night sky with an unmodified camera. If you don't want to modify your camera for whatever reason be encouraged to use it as it is!
- F.Meiresonne, markb, hendric and 26 others like this
45 Comments
Hi Elf,
What do you use for processing/stacking?
I do everything in PI and I use the manual step by step pre-processing.
Inspiring article, thank you!
What mount do you use?
Thank you. My mount is the Skywatcher EQ6-R.
Elf, thank you most kindly for sharing your beautiful photographs and knowledge in such an open and friendly manner. What you have written here, presented on your website and shown in your videos is immensely encouraging and inspiring. I don't recall how I stumbled across this topic/thread, but I count myself lucky that I did. As a newcomer to CN and a beginner who is interested in learning about astrophotography with a DSLR, I hope others in a similar position will also find this topic. It would be nice if it was pinned here > Astrophotography and Sketching > DSLR, Mirrorless & General Purpose Digital Camera Imaging. Somewhere, I don't remember where, I read that you are a fellow Linux user. I would be grateful if you could share any information about what open source apps you use and others that are available.
Could you please expand on that a little? Are you referring to PixInsight?
Yes I am. PixInsight comes with a bunch of small operations for pre-processing and for post processing. It also comes with scripts or more complex processes that do a bunch of steps automatically. On top of that there are tools for image analysis as well. As far as pre-processing is concerned you have the choice either to pour all files into the BatchPreProcessing Script similar to Deep Sky Stacker or you can do everything step by step like so:
- calibrate the single flat files (i.e. subtract bias)
- integrate the flat files to a master flat
- calibrate the light files using whatever you like of bias, darks and the master flat
- apply a cosmetic correction or not
- debayer
- discard bad subs using the subframe selector
- star align to a frame you choose
- integrate the lights to a stack
That is what I do. Reason being you can see the results of each step and see if there is an issue. With the black box tools like BPP or DSS you put your data in and if the result is crap you have a hard time finding the reason. YMMV.
Basically I use PixInsight for processing (not an open source obviously!). The only small open source program I use is exiftool to check the subs ISO, exposure time and temperature. Many image viewers like gThumb show these as well. That's about it. My imaging is pure handcraft without computer, only the lacerta MGen II for guiding.
I use bluefish editor to maintain my website but any other editor works equally well. For my year in review images I use Pinta, basically a MS Paint clone.
BTW PixInsight also includes a plate solver so there is no need to install another one. If you want computer controlled imaging it is a different story but I have never tried and probably won't try it any time soon.
Elf, many thanks for your most helpful reply. I hear what you're saying and appreciate your advice very much. It seems to me that maybe I should invest in PixInsight, sometime in the future. Right now, I feel that I'm barely crawling (with astrophotography), looking forward to being able to walk a little. Running is a long way off, yet. Despite having used cameras since I was a kid in the 1950s, I'm finding this learning curve steep, but fascinating. For better, or for worse, I decided to invest in a Fornax LighTrack and a copy of Charles Bracken's Primer. When I have recovered from the cost of that outlay, maybe I will try PixInsight. I toyed with the idea of spending money on a computerised GoTo mount, but decided I'd probably enjoy spending time taking photos using a LighTrack more. For now, I'm trying to get my head around how to use Siril. I am already familiar with RawTherapy and GIMP, so hope I will be able to make some progress without need for much more expenditure, for a while at least.
Siril is a good choice.
You might find this channel helpful:
https://www.youtube....rch?query=siril
I can't stop watching Nico.
Thank you kindly.
That was something i did not know. But i experienced it. At 714 mm the Bahtinov works great...at 335 becomes tedious to see, in my 61 mm scope... ...no spikes to be seen.
I am still a bit undecisive with the APT Bahtinov aid...confuses me...
Rubbish - you can control every step of DSS - sounds like you just haven't bothered to try
As I say: YMMV.
Pure handcraft without computer.?..What do you mean, no automated shooting then ? Or do you use an automated remote control device...?
The magic box in my case is the lacerta MGEN-II stand alone auto guider. It corrects the mount via an analogue ST4-cable and it triggers the DSLR via an simple trigger cable. The DSLR is set to bulb. The images are stored on the memory card. All other things: hand crafted.
Polaralignment: by eye and polar scope
Focus: via life screen and Bahtinov mask
Mount alignment: via 3 stars and mount hand controller using a Telrad and the camera screen
FOV: by test image and manual adjustments. I sometimes bring a print of the stars from stellarium to get the FOV right.
Filter change by manual removal of the T-ring and replacement with a different one with another filter inside
Meridian flip: via mount controller, quick recalibration of the guider for the reversed axis.
You can see the whole story in this video:
https://www.youtube....h?v=Z9jePIkHjG0
It is like cutting trees: I do own a chainsaw and cut down a bunch of trees with it. One fine day I decided to cut one down purely by hand with a hand saw just half as long as the trunk diameter. Just for the experience of doing something like centuries ago without steam or petrol power. Now I respect the work a tree does growing a lot more. It is similar in imaging. I just don't want a computer to do the job. I want to do it myself to experience a deeper connection to what I am doing. I strictly oppose transferring the need for extreme efficiency at work to my private life. My hobby shall be a meditative zen experience.
When it comes to dish washing I prefer the opposite approach and let the machine do it for me. Dish washing just does not resonate as much as garden works and photography does. :-)
Haha,
Pretty much like i do...
Only i do use PHD2 for guiding and APT for controlling the DSLR. But guiding is through ST4 also..just , well , it works well...once all is running i control it via my indoor pc via Teamviewer...from my sofa...
The rest is well pretty manual..
I have a Rebel T3 chosen for big pixels for the price.
I've also loved handholding a Nikon S8100 Coolpix for moon photos.
What gets me is, when I started with a DSLR, I was told to remove the I/R filter. When I got my OSC astro camera, I was told to get an I/R filter.... smh.
Thats because the cut off point at the IR/red light boundary are different with DSLR blocking filters and astrophotograpic UV/IR blocking filters. The standard blocking filters in DSLRs roll-off the red response at a point that diminishes hydrogen-alpha emissions significantly - you will not get good responses from emission nebula. However if you take the DSLR filter out and do nothing more then stars that emit strong IR light at longer wavelengths will not be in focus at the same time visible light is in focus if you are using a refractor telescope as most are not optimised to cover near IR. Hence you need to put in a IR blocking filter that cuts-off closer to the red/IR boundary
So in essence you are taking out one filter to replace with another to SHIFT the IR/VIS cut-off boundary and allow H-alpha light through