did they stop making the DSLR EOS 60Da?

[Cosmos5112]

I want to get into astrophotography so I was wondering. Yet I can't purchase on Canon site, amazon, & walmart....help please

[TCampbell]

I just checked B&H Photo and Adorama and don't see it listed there either.  A "Google Shopping" search showed only a single merchant who claims to have one (a merchant I've never heard of before.)

The Canon online store doesn't list it anymore.  the Canon "refurbished" page in the store does list it, but says it's not in stock.

I use one of these cameras and I do really like it.

Most imagers that I know will get old Rebel bodies (no longer under warranty) and then modify them for astro-imaging (lots of websites offer services to do the modification for you.)  

I was just at a presentation by Axel Mellinger -- who became famous for traveling the world in order to capture an image of the entire sky (you can find his web page here:  http://people.cst.cmich.edu/melli1a/Astronomy.html  which includes links to his Milky Way panorama.)  Anyway, I believe that particular image was captured using SBIG CCD imaging cameras, but he mentioned he prefers to use a full-frame DSLR for most astrophotography of the night sky (and I *think* he actually said he uses a Canon 6D -- but I think his has been modified.)

I use my 60Da for astrophotography, but I use a 5D III for my normal non-astrophotography shooting.  I still own a "gently used" 5D II body (I had it only 3 months before Canon released the 5D III and I eventually upgraded) and I've been mulling over the idea of modifying the 5D II for astrophotography work.  Most of the sites that will modify cameras only mention doing this to Canon "Rebel" bodies and I don't see any references to full-frame bodies. 

Clear Skies!

Tim

[Waddizzle]

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@TCampbell wrote:
 

I use my 60Da for astrophotography, but I use a 5D III for my normal non-astrophotography shooting.  I still own a "gently used" 5D II body (I had it only 3 months before Canon released the 5D III and I eventually upgraded) and I've been mulling over the idea of modifying the 5D II for astrophotography work.  Most of the sites that will modify cameras only mention doing this to Canon "Rebel" bodies and I don't see any references to full-frame bodies. 

Clear Skies!

Tim

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What do you think sbouy using the 5DS=R for astophotography?  It doesn't have a low pass filter, either.

[TCampbell]

It's not really the low pass filter... it's the IR filter that astro-imagers are concerned with.

To understand why the IR filter is important, it helps to have a little background.

A normal camera has a bandpass filter which is designed to produce images that match what the human eye expects to see.   We normally believe that we see a rainbow of colors with equal intensity of each color hue.  But the visible portion of the spectrum runs from roughly 400nm on the "short" end (indigo) to rouhly 700nm on the "long" end (reds).  Below 400nm is the start of the UV area and above 700nm is the start of the IR area.

The vast majority of ordinary matter in the universe is the Hydrogen atom -- which in round numbers is on the order of 90% of all matter.  Hydrogen atoms absorb and emit energy following something called the Ballmer series (those are the primary wavlengths of color when Hydrogen glows).  

Most people are familiar with a "Neon sign" -- a glass tube filled with neon gas and energized by electrodes to excite the gasses and cause them to glow.  A "neon" tube will glow in an orange/red color to our eyes, but if you use a spectrascope (diffraction grating) you would see that it's really emitting light in several different hues of red, a few hues of orange (one of which is particularly strong) and actually a few hues of green (but those are rather weak.)  But when you combine all of these colors (no spectrascope or diffraction grating) the color appears to be red/orange to our eyes.

For Hydrogen gas, the colors are different.  If you fill a glass tube with hydrogen gas and then excite the gas, you see a pinkish color.  But in the spectrascope you'll see four different colors.  Those colors are a rich red (656nm -- that number is important), an aqua color (486nm), a blue color (434nm), and a deeper navy-blue color (410nm).   But the red color dominates so much that the red outweights the rest of the colors combined so much so that the combined color appears pinkish/orange hue.

When an atom (in this case a Hydrogen atom) loses energy, the electron drops from a higher orbit to a lower orbit and that drop causes the atom to give off a photon of light at a particular wavelength (depending on the drop).  But all atoms of the same type have identical behavior.  Which means that every Hydrogen atom will give off the same four colors (there are actually four more but they are in the UV spectrum so we can't see them) and the Hydrogen atom gives off far more light at the 656nm wavelength than any other (that wavelength is named the "Hydrogen alpha" wavelength... "alpha" because it's the strongest of them all.)

So here's why this matters to astro-imagers...

A normal camera isn't actually very sensitive to red.  We all assume that the red we see with our eyes is normal, but actually humans aren't particularly senstiive to red (the "red" colors we see are actually much stronger than our eyes can detect.)  

When someone takes an astrophotography image of a deep-space nebula (specifically an "emission nebula") that nebula will generally tend to glow richly in red (and it may also glow in that blueish-aqua hue).  There are some emission nebulae that glow in Oxygen III (a strong green color).  

The camera is extremely sensitive to the green, also strongly sensitve to the aqua hue, but it is not very sensitive to the red hue (the Hydrogen alpha color) and yet there is more of this red hue in nebulae than any other colors.

The normal filter in a DSLR, being designed to mimmick the sensitivity of the human eye so that our photos look normal to us, actually blocks quite a bit of the light in the reds.  They typically start trimming the reds (very slightly) around the 500nm wavelength and the amount of light filtered is slightly increased (ramped up) until it reaches the 700nm wavelength (the end of the visible spectrum and the beginning of the IR spectrum) at which point it blocks pretty much everything.

At the 656nm wavelength the filter is blocking about 75-80% of the light.

A camera modified for astrophotography typically has the UV/IR filter removed and replaced with a filter that does not cut out the reds at all... and then very abruptly does a strong cut once it reaches the IR (so instead of a slow ramp-up of blocking light to mimmick our human sensitivity, it blocks nothing until it reaches the IR and then does an abrupt cut.)

The results of this change are that the exposure times are substantially reduced because the camera is vastly more sensitive to red.... easily 2 full stops.  In other words, when I capture a 4 minute exposure with my 60Da, I get an amount of "red" that would take a normal camera probably about 16 minutes to collect.

I actually did such a test (it was the reason I bought my 60Da).  I had a friend in the club image an object with his 60Da (and I think it was a 4 minute exposure).  I then used my 5D II on the same telescope to image the same object using the identical exposure.  While the image was rich on the 60Da, you could barely even see anything on my 5D II image.  I doubled the exposure and ran an 8 minute test... this time I could see more of the object but not even close to what the 60Da had produced.  I doubled the exposure again, and I finally started to see more detail... but now I'm running an exposure which is 4 times longer.  The following week I went out and bought my own 60Da.

My guess (I'm not a Canon insider) is that the 60Da was just a special batch produced of the 60D using the identical assembly process... except that for this batch they used a different filter and put a different badge on the body.  The camera is otherwise identical.  They likely continued to sell the product for as long as inventory was available ... but have run out.

Nikon finally announced their D810a (I'm not even sure if it's shipping) -- so the rumor mills suggest that Canon would have no intention of surrending the astrophotography market to Nikon and will probably come out with something to answer Nikon's product.  Canon is VASTLY more popular than Nikon among astro-imagers (there are a numerous astro-imaging applications that work with Canon cameras... very few that work with Nikon.)  So apart from trying to find a vendor that still has a 60Da in stock, one would have to find a used camera, or buy a different camera body and modify it, or perhaps wait to see if Canon offers a different astrophotography model in the future.  I'm hoping they do offer an astrophotography version of another model.

[Waddizzle]

Wow.  I guess that 60Da had one more difference that I was unaware of.

[ebiggs1]

And if you try to use a 60Da for 'normal' daylight you may get some "bleed or smear" from the IR spectrum which will cause the photo to look unnatural.  Only because this is light we normally don't see.

[RobertTheFat]

What you can do with unfiltered or differently filtered cameras goes well beyond astrophotography. Many years ago I saw some pictures taken with a camera modified to extend its sensitivity into the UV range, the object being to show what some prosaic flowers look like to a bee. Some of the flower petals had bold, almost garish designs intended to attract the attention of bees, but which were completely invisible to the human eye.

[TCampbell]

Here's a graph that may help.

The graph represents the wavelength of light (along the horizontal axis) and the amount of light allowed to pass through the filter at any given wavelength (the height of the graph).

The bandpass for a typical Canon UV/IR filter is drawn in red.  This particular company (although their filter is fairly typical amoung modified astro-imaging cameras ... and probably similar to the filter in a 60Da).  This particular graph is showing the bandpass of a filter by a company called Baader-Planetarium. 

If you look at the red line, it starts slightly curving down at 500nm and by 550nm it starts ramping down aggressively.  The wavelength at 656.28nm (656.3) is the Hydrogen alpha emission line.  That's a key color found in many deep-space emission nebulae.  

You can see that at the H-alpha emission line, the filter is only allowing about 25% of the light (at that wavelength) to pass through.  That means a normal unmodified camera (which mimmicks the human eye sensitivity) is blocking 75% of that light.

It is possible to modify a camera by simply removing that filter, but if you do that then you also let in all the IR light and the IR light focuses at a different distance and that would cause the images to look a bit out of focus.  So when unfiltered cameras are used, there's general a seperate IR filter somewhere in the path (for example, a screw-on filter in front of the camera).  Most imagers tend to replace the normal UV/IR filter with a new UV/IR filter that simply has a more abrupt cut-off at 700nm rather than the slow ramp.

This is basically what all the fuss is about for having a dedicated camera for astro-imaging.

Astro-imaging cameras can still be used for normal photography, but you would notice the images look really warm.  You can always set a custom white balance to cool the images.

The hard-core astro-imagers will buy dedicated CCD imaging cameras that are cooled (the cooling system can usually drop the temperature of the imaging chip by at least 40-50ºC because there's a relationship between image "noise" and the physical temperature of the imaging chip.)  These cameras are monochrome and have no filters, but a mechanical filter wheel is typically installed in front which minimally contains a "red", "green", "blue", and "luminance" filter (a luminance filter is simply a filter that has a UV/IR cut and allows all the light in the visible spectrum to pass but blocks everything else.)  When they image, there's always a filter in front of the sensor... so they'll take a series of images with each filter and then assign the images to color channels in photoshop, which merges the image to produce a color images.

The dedicated CCD imaging cameras, filter wheel (a robotic device that rotates in the next filter between images), and the filters themselves are are rather expensive.  A "cheap" setup would typically be at least $5k and it's not unusual for them to be well over $10k.  One of the more accomplished imagers that I know considers any imaging camera that costs less than $50k to be a "cheap" camera (yeah, crazy... right?).  

[ddaniels1]

Kudoes to Tim C for a great explanation of the 60Da UV/IR filter and how it works for astroimaging.

I have a 60Da and attach it to my Celestron 9.25 EdgeHD scope. There is a frustrating problem in bringing the 60Da to focus when mounted on the scope. I have 'exp SIM' set to 'enable' and use 'Live View' mode. I use both 'Bulb' and 'Manual' modes when trying to focus but it is frustratingly difficult and time consuming. The 9.25 does have a 10:1 focuser.

Any tips on how to speed up the focusing process??

Dave

[TCampbell]

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@ddaniels1 wrote:

Any tips on how to speed up the focusing process??

Dave

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Do you own a Bahtinov focusing mask?

There are a few ways to spend along focusing ... with no equipment at all, I switch on live-view and crank the ISO to max and crank the shutter speed to 30 seconds (in manual mode).  This brightens up the live-view display (because Canon has "exposure simulation" in live-view mode).    Find a bright star anywhere in the sky (this time of year you'd pick Sirius ... follow the three "belt" stars in Orion toward the East (left for northern hemispher observers) and the brighest star you come across is Sirius.  It's the brightest star in the night sky.

Center on it and then increase the live-view magnification to 10x.  Now _very_ carefully adjust focus to try to make the star as pinpoint as possible.

If you own a Bahtinov focusing mask it's much easier.  The mask fits over the front of your scope much like the front dust cap/cover ... except it has slots milled in it.  The slots are angled in three different directions.  

A nuance of the wave-nature of light is that anytime light hits an "edge", it will bend perpendicular to that edge.  Since the Bahtinov mask has LOTS of edges, there's a lot bending going on and this casues any bright star to throw diffraction spikes.  Since the slots are angled in three directions, you'll see three sets of diffracction spikes.

If the scope is not focused, you'll notice that the three spikes don't actually converge at a common center point.  But as you adjust focus, they will all converge at a common center point ONLY when you've nailed focus.

I use a mask made by Spike-A (you'll want to do a Google search for "Bahtinov focusing mask" ... Canon doesn't allow links to commercial websites per their acceptable use policy on the forums so I cannot provide a direct link (well... I could, but it would get removed)).  Loads of vendors make these.  

After you've achieved focus, remove the focusing mask, return the camera to bulb mode and set the ISO back to some value (for a 60Da I recommend you do not exceed ISO 800 for astrophotography imaging ... that's the point where the camera switches from "upstream" gain (analog gain applied prior to analog-to-digital-conversion (ADC) and starts using "downstream" gain (digital gain applied by just multiplying the pixel values after ADC.  The reason this is a good value to know is because "downstream" gain results in a stronger loss of dynamic range.

There are other methods, but the Bahtinov focusing mask is my favorite.  

There are software based methods such as FocusMax (but that requires an electronic focuser ... which Celestron *just* announced and is finally available for your scope).

Many software programs support something called "full-width half-max" (FWHM) which is al algorithm for determine how "pin point" your star is.    If you were to graph the brightness of the star in 3D, it will look like a spike coming up out of the graph. (or think of it as a mountain rising up off a plane).  But the base of the mountain never really gets to zero.  How do you masure the diameter of something that doesn't get to a zero point at it's base?  So the idea is to measure the max hieght, divide by 2 (half the max) and then measure the diameter of the peak at that point.    

If you think about it ... a poorly focused star would have a very wide base.  A sharply focused star would have a very narrow and steep base.

So what you do is star at the FWHM value that the software reads out and *slowly* adjust focus until you get the FWHM number to be as small as possible.

But the trouble with this method is that if the seeing conditions are poor, the star will be fractionally distorting (due to atmospheric effects) and fooling you (this can be very frustrating).  When I use a Bahtinov mask, I don't have these problems (it's much easier and you can visually see that it's working).

Once you've achieved focus, you can return to the target you plan to image for the night (if anything in the night sky is focused ... then everything in the night sky is focused.)

Since your scope has a metal barrel on the optical tube and it's an SCT, it will be sensitive to temperature shifts.  As temps drop over the course of a night, you'll need to revalidate focus periodically ... otherwise you can find your initial images look good ... but your later images look mushy.  (Carbon fiber optical tubes have excellent "thermal" properties in that they really don't expand/contract with temperature shifts the way that metal optical tubes do.)

Good luck!