So I don't need a modded DSLR?...

[smr]

Referring to this article:

 

http://www.clarkvision.com/articles/do_you_need_a_modified_camera_for_astrophotography/

These photos were taken with a stock 7D Mark 2 Camera. I have a similar Camera with even more recent sensor technology insofar as the Canon 80D, therefore do I need it modifying in terms of Ha sensitivity ? I'd like your opinions please as I may be missing something from Roger's take on it.

"Modifying digital cameras is not necessary to obtain great astrophotos. Many stock cameras have good hydrogen-alpha response, e.g. recent Canon DSLRs. More important than a modified cameras is proper post processing methods that will bring out and not suppress hydrogen alpha emission, and cameras with good sensitivity and very low thermal dark current. The best digital camera for deep sky astrophotography that I have evaluated has good sensitivity, including hydrogen-alpha, and amazingly low dark current is the Canon 7D Mark II 20-megapixel digital camera. A great full frame digital camera for astrophotography is the Canon 6D 20-megapixel digital camera.

The advantage of a stock digital camera in astrophotography is that the color balance is close to that of the human eye, and shows compositional differences better. Modified digital cameras are too sensitive to hydrogen alpha emission, making scenes containing hydrogen too red, swamping colors from other compositions. Often this shows in amateur astrophotos as dominantly red. The choice of course is personal. I prefer images with more colors to show more processes and chemistry. I believe such images are more interesting, so I only use stack digitalcameras for my astrophotography."

[michael.h.f.wilkinson]

Much depends on the target, and personal taste. I find the above colours a bit garish, and personally prefer subtler handling. I have a modded 550D which works well, and gives good results in my book.

 

Not sure this is way too red, and anyway, to the human eye the scene is all grey because at night the cones in the retina don't work that well. You can always push back the red signal in postprocessing. I might give my non-modded 80D a shot one of these days, but I would expect I need far longer exposures to get the same S/N on H-alpha rich targets

 

[thomasv]

Hmmm, not sure there is such a thing as 'too sensitive to Ha'. You can always change the balance in post processing, while if you haven't captured enough of it in the first place, you can never make up for it properly. Sure, great astrophotos can be achieved with unmodified cameras, but I would never present greater Ha sensitivity as a disadvantage. 

[smr]

Very nice images. I like your PP on them, and I too prefer the more subtle editing. I agree that the colours in Roger's photo look a tad over done, I'd pull them back slightly if my own, but that's not to take away from what fantastic images they are as is. I was astounded more than anything at what a stock DSLR from the 7D2 era onwards can achieve though more than anything.

[Alien 13]

I personally wouldn't modify my Canon 80D (I think I would rather have hot needles through my eyeballs), the Ha response is plenty with the newer cameras and modification can introduce lots of negatives like bloated stars/no AF/loss of auto sensor clean etc.

Alan

[smr]

10 minutes ago, Alien 13 said:

I personally wouldn't modify my Canon 80D (I think I would rather have hot needles through my eyeballs), the Ha response is plenty with the newer cameras and modification can introduce lots of negatives like bloated stars/no AF/loss of auto sensor clean etc.

Alan

I'd never modify my 80D either, I was wondering if it's worth getting a cheaper DSLR just for astrophotography and modifying that though.

[Alien 13]

1 minute ago, smr said:

I'd never modify my 80D either, I was wondering if it's worth getting a cheaper DSLR just for astrophotography and modifying that though.

That is a better option I think..

Alan

[wxsatuser]

Have tried the 6D and 7DMK2 both are very good as is.

[JOC]

I can only afford one DSLR - it has to do for all purposes and so I leave it as it was purchased- unmodded!  At the moment it is taking photos that are giving me personal satisfaction and is plenty good enough for learning to do this night sky business.

[michael.h.f.wilkinson]

42 minutes ago, smr said:

I'd never modify my 80D either, I was wondering if it's worth getting a cheaper DSLR just for astrophotography and modifying that though.

That is more-or-less what I did: I got a modded 550D with fewer than 9000 clicks for around 200 euro, to replace my old (modded) 450D. The 80D is used for daytime imaging. It is however absolutely brilliant under low light conditions, showing very little noise even at ISO 6400, so I might give it a spin on targets like Markarian's chain.

[ollypenrice]

I'm afraid that I'm not keen either on his arguments or his images. If his aim is to create images with a full range of natural colours then I don't think he has succeeded. The heavy handed processing has produced strange by-products such as the cyan shell around M42/Running Man, which I think is spurious, and the curious green/blue streak around and above (in this orientation) the Trapezium. In imaging this target in assorted filters I've never found any trace of this, but maybe I missed it. I find the colours garish and unconvincing, but that can be said of any over-saturated image however captured. 

As thomasv says above, you don't have to retain the overly red colour balance captured by modded DSLRs but you have the signal in the bag. Once you have it you can process it as you wish.

In Roger Clark's Heart Nebula and NAN we do indeed see what these objects would look like to a more sensitive human eye and, with their very low Ha component (low compared with what is possible) they have a certain natural charm. If that's the objective, fine. For other imagers, though, it isn't the objective. They are looking to find structure and detail not apparent without specialist filtration.

The mono camera's advantage is not its sensitivity to Ha but its ability to make efficient use of an Ha filter to isolate the Ha, and so isolate those structures emitting in that wavelength. These structures add information and interest to an image. A modded camera can still be tolerably efficient through an Ha filter but I don't know how well an unmodded one would work. The important aspect of a narrowband filter is not so much what it passes as what it blocks. I think it is this point which the author misses. You don't have to exploit an Ha layer in order to find lots more red, you can use it to find lots more structure.

Olly

 

 

[gorann]

I have used a Canon 60Da (i.e. factory Ha modded) since I started in AP about three years ago, and I thought that camera would have a great advantage over a standard 60D. Due to the few nights with clear skies, I have now first doubled and then tripled my effort in collecting data when the sky occasionally clears by adding a 300mm and 135mm telephoto lens side by side of my 5" refractor, and since the 60Da is still rediculously expensive (used) compared to the standard 60D, I felt I could only afford to buy two 60D for the other lenses. To my surprise, I have not found much difference between the 60Da and 60D although I have not felt I could use precious imaging time to make a direct comparison with the same lens and exposure times. Here is the California Nebula with a 60D and my Canon 300 mm f/4 and I feel it is red enough (76 x 3 min at ISO1600). A few days ago I even tried Ha imaging of the Soul Nebula with a 60D under a full moon and snow covered grounds, and I think it also worked out quite well (Canon 300 mm f/4, Astronomik 12 nm Ha clip filter, 38 x 8 min at ISO1600).

So my conclusion is that unmodded is good enough - Ha imaging can be done but you will need more exposures to get the same number of photons. I assume you had a look at the link that Clark gives, showing Ha transmission with different DSLRs:

http://kolarivision.com/articles/internal-cut-filter-transmission/

Apparently it is about 25% for the 60D, but some cameras are close to zero - so check that carefully before you buy a DSLR.

[newbie alert]

Flicking through the first part of the answers there's a of conflicting bad advice...you can't process ha signal if you haven't got it..and seeing it as a red colour on over sensitive modded cameras! Ha signal captures all the details and combined with a narrow filter ,smaller stars.. you can expose for longer without the light polluion affecting the image..capture more details with smaller stars..awesome...the only thing it won't give you is star colour..thats the only downfall I can see..the rest is a positive..

[ollypenrice]

On 16/03/2018 at 09:08, newbie alert said:

Flicking through the first part of the answers there's a of conflicting bad advice...you can't process ha signal if you haven't got it..and seeing it as a red colour on over sensitive modded cameras! Ha signal captures all the details and combined with a narrow filter ,smaller stars.. you can expose for longer without the light polluion affecting the image..capture more details with smaller stars..awesome...the only thing it won't give you is star colour..thats the only downfall I can see..the rest is a positive..

I do sense a problem in this reply. It may be a matter of wording. If we take, 'Ha signal captures all the details and combined with a narrow filter ,smaller stars.. you can expose for longer without the light polluion affecting the image..capture more details with smaller stars..awesome...the only thing it won't give you is star colour..thats the only downfall I can see..the rest is a positive' and apply it to shooting the Pleiades we can see that it can't  be right. There is insignificant Ha signal in this region but there is ERE (extended red emission.) Likewise you could shoot galaxies through a filter which passed only deep red (an Ha filter) but why would you do that? Galaxies do not emit primarily deep red light.

I think it's important to be clear why we use the filters we do. I shoot through (amongst others) red, luminance and Ha filters, all of which pass pretty much identical amounts of Ha light. What matters is not the light which the filters pass but the light which they block. The Ha filter allows the imager to extract those structures which are shining in Ha and emphasize them in the final image. Without careful processing, shedloads of Ha light will not make for a better image.

Olly

[newbie alert]

21 hours ago, ollypenrice said:

I do sense a problem in this reply. It may be a matter of wording. If we take, 'Ha signal captures all the details and combined with a narrow filter ,smaller stars.. you can expose for longer without the light polluion affecting the image..capture more details with smaller stars..awesome...the only thing it won't give you is star colour..thats the only downfall I can see..the rest is a positive' and apply it to shooting the Pleiades we can see that it can't  be right. There is insignificant Ha signal in this region but there is ERE (extended red emission.) Likewise you could shoot galaxies through a filter which passed only deep red (an Ha filter) but why would you do that? Galaxies do not emit primarily deep red light.

I think it's important to be clear why we use the filters we do. I shoot through (amongst others) red, luminance and Ha filters, all of which pass pretty much identical amounts of Ha light. What matters is not the light which the filters pass but the light which they block. The Ha filter allows the imager to extract those structures which are shining in Ha and emphasize them in the final image. Without careful processing, shedloads of Ha light will not make for a better image.

Olly

I just re-read what I wrote and maybe I missed out what I was thinking,some of it didn't make much sense to me( words like structure and contrast were missing in order to describe what ha can give you)

Some DSLR can be almost blind in HA and only pick up on a the lower end of the red transmission line, having a ir pass or no blocking filter unlocks the sensitivity at this end..

I do know of a couple of people that have tried imaging the Pleiades in HA.. waste of time is what a said..

[Seanelly]

On 14/03/2018 at 06:16, smr said:

I'd never modify my 80D either, I was wondering if it's worth getting a cheaper DSLR just for astrophotography and modifying that though.

I retained my original trusty stock Canon T2i as an all-round camera and purchased a T6i to modify for this new hobby. Perhaps I could have done it the other way round but the T6i has better noise reduction. I doubt that the 18MP to 24MP jump makes much of a difference, but the T2i has a half million or so clicks on it and it was a concern that it might not hold up much longer through these Canadian winters, though it has worked steadily through -25C temps on many occasions in the past.

[smr]

So it's not just about colour then? Ha sensitivity also determines the detail and structure in nebulae ? If so than that would sway me towards buying a cheaper DSLR and having it modified. The only thing is that from what I have seen of images taken with modified DSLRs the nebulas come out just red and any other colours seem completely suppressed. Can anyone share some modded images that show differently ?

It would be frustrating that I have a DSLR which is ISO invariant in the Canon 80D but I wouldn't be able to get that modded as I need a DSLR for daytime photography. I can't seem to find the Canon 80D's Ha transmittance anywhere.

[Stub Mandrel]

I am reluctant to take advice from people whose 'one true way' is defined by what they see as the shortcomings of other people's approaches rather than the strengths of their own.

[StuartJPP]

It is quite strange that Roger's image looks like no other image of that region of sky, both from OSC or mono cameras. Perhaps everyone else is doing it wrong?

I am an advocate of having a DSLR modified if you can so that it's spectral response is similar/closer to that of a dedicated astro OSC camera. It all depends on your own personal preference.

Do you have to modify your camera? No, of course not but I will stick with my modified Canon 6D, my Canon 5D Mark III however will remain unmodified...

[smr]

18 minutes ago, StuartJPP said:

It is quite strange that Roger's image looks like no other image of that region of sky, both from OSC or mono cameras. Perhaps everyone else is doing it wrong?

I am an advocate of having a DSLR modified if you can so that it's spectral response is similar/closer to that of a dedicated astro OSC camera. It all depends on your own personal preference.

Do you have to modify your camera? No, of course not but I will stick with my modified Canon 6D, my Canon 5D Mark III however will remain unmodified...

 

Lovely image and lovely colours. I have yet to image the Horsehead and Flame but it's probably my favourite DSO, that, M42 and the Rosette Nebula, at the moment. The colours in your image are very nice and how I like to see that region. I think I could do with a light pollution filter anyhow, and just see what I can achieve without modifying my DSLR first, if after imaging the HH and Flame and the Rosette I find that it's lacking then I guess it'll be time to look at either a dedicated astronomy camera, which I hear is another learning curve altogether, or modifying a second hand DSLR. I guess. 

[ollypenrice]

1 hour ago, smr said:

 Ha sensitivity also determines the detail and structure in nebulae ?

No. I can't speak for what others are saying but that is certainly not what I'm saying. What I'm saying comes in two parts. 1) You do have to capture the Ha signal in order for it to appear in the image. That is hardly controversial.* 2) In order to isolate the structures unique to Ha you need to run your Ha sensitive camera through an Ha filter which blocks other signal.  It is this process which enhances contrast.

In my own imaging I'm trying use an Ha layer to find faint Ha signal and high contrast in Ha structures to enhance a broadband image. I don't advocate what Neil calls 'a one true way' but what I'm trying to do is think through the consequences of 1) high Ha sensitivity and 2) the isolation of purely Ha signal.

Olly

* Edit for further clarification: my luminance filter passes more Ha than my 3nm Ha filter and so, in all probability, does my red filter. What my Ha filter does do is allow me to expose for longer to catch more Ha and only Ha. Three channel processing then allows this additional signal and additional contrast to be incorporated into the image without turning everything red. Capturing ever greater amounts of broadband while simultaneously capturing ever greater amounts of Ha is not the same.

[smr]

I'm still undecided as to what to do with regards modifying a DSLR for astro use or not.

I don't know if it helps but this image was taken in the Summer with my Canon 80D, no light pollution filters, from a Bortle 6 sky, around 1h30m of total exposure at around 60 seconds each, with a 1.8 50mm stopped down to f 3.2

Is the sensor showing good Ha response or is it not possible to really ascertain with this particular image? I understand this may be quite different to faint dust in Ha rich targets but I'm unsure. 

I am most interested in emission nebulae DSOs.

 

Cygnus by Joel Spencer, on Flickr

[geordie85]

There is some noticeable ha targets in your image but I can't help but think the rest of the red/ oranginess is from your light pollution.