Nikon Full-Frame Astro DSLR

On Thursday, February 12, 2015 at 12:11:33 AM UTC-6, Davoud wrote:
Davoud:
http://petapixel.com/2015/02/10/niko...full-frame-dsl
r-astrophotography/

Uncarollo2:
The problem with these multi-megapixel chips is the very limited well depth
and high noise levels. This limits their use in Astro-photography to the
limited number of bright objects. The small pixel size and large pixel count
does not add up to high resolution when it comes to astronomical images..

To give an example, a very faint object may register a count of only 300 out
of 64,000 bits in a 16 bit image using one of these small pixel 35mm chips.
The object will be squeezed into a very narrow range between the noise floor,
say at 150 and the maximum exposure level of 300. That 150 count range then
needs to be stretched into a 16 bit image in order to be processed further.

Contrast that with a similar sized chip consisting of 9 microns or even 12
microns where the well depth is some 5 times larger and the noise level is
several times smaller. That same object will now register at a level of 1500,
while the noise might be down to a level of 50. The range for this object is
then 1450 which is stretched to a 16 bit image with almost 10 times the signal/noise ratio.

True enough, I'm sure. Nonetheless, there are plenty of bright
objects--M42, M45, M1, M31, the Milky Way, Comets, the Moon, and so on,
to satisfy an entry-level astrophotographer using a DSLR. S/he knows
nothing of noise floors, full wells, and the like, but still manages to
produce satisfying astrophotos with a camera that has custom white
balance controls and can thus be used for a variety of other purposes
as well. Tools like Pixinsight and Photoshop help too, of course.

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

Yes of course these cameras do a wonderful job on basic astronomical objects where a full astronomical camera is not necessary and sometimes is inappropriate. I have a little Sony NEX-7 which I've used to take images of the Milky Way that are quite striking for a consumer camera. That said, it has a noise floor that I cannot go below for truly faint stuff. That's mainly a limitation due to lack of cooling the chip.

However, one person I know has modified his Canon camera with a thermoelectric cooler and has taken many images of very faint deep sky objects. Some examples:

http://www.pampaskies.com/gallery3/D...bjects/Sh2-308
http://www.pampaskies.com/gallery3/D.../NGC2170_combo
http://www.pampaskies.com/gallery3/D...C6188_LHaRHaGB

On 2/12/15 10:22 AM, Uncarollo2 wrote:
However, one person I know has modified his Canon camera with a thermoelectric cooler and has taken many images of very faint deep sky objects. Some examples:

http://www.pampaskies.com/gallery3/D...bjects/Sh2-308
http://www.pampaskies.com/gallery3/D.../NGC2170_combo
http://www.pampaskies.com/gallery3/D...C6188_LHaRHaGB

Those are nice pictures.
Coupled with what I hear about the quality of the beef steaks, one must
believe that's the place to be.

On 2/10/15 6:43 PM, Davoud wrote:
http://petapixel.com/2015/02/10/niko...full-frame-dsl
r-astrophotography/

From link:
"Nikon does warn that, due to its modifications, the D810A is not
recommended for general photography."

Yet it's pictured with a terrestrial lens and viewfinder.
What's up with that?

On Thursday, February 12, 2015 at 5:56:28 PM UTC-8, lal_truckee wrote:
On 2/10/15 6:43 PM, Davoud wrote:
http://petapixel.com/2015/02/10/niko...full-frame-dsl
r-astrophotography/

From link:
"Nikon does warn that, due to its modifications, the D810A is not
recommended for general photography."

Yet it's pictured with a terrestrial lens and viewfinder.
What's up with that?

I know practically nothing about cameras... but couldn't you just put a screw-on filter on the lens to replace that which had been removed from the camera, in order to make it a terrestrial camera again?

\Paul A

On Thu, 12 Feb 2015 17:56:25 -0800, lal_truckee
wrote:

From link:
"Nikon does warn that, due to its modifications, the D810A is not
recommended for general photography."

Yet it's pictured with a terrestrial lens and viewfinder.
What's up with that?

What's a "terrestrial lens"? I don't normally use a DSLR on a
telescope (the pixels are uselessly small), but I do use one for wide
field sky imaging, and for that I normally use an ordinary camera
lens.

On Thu, 12 Feb 2015 18:46:33 -0800 (PST), palsing
wrote:

I know practically nothing about cameras... but couldn't you just put a screw-on filter on the lens to replace that which had been removed from the camera, in order to make it a terrestrial camera again?

Possibly. But if it's an interference filter, it will only work over a
limited input angle range, so only for longer focal length lenses. And
of course, you'd need a set of them for all the different aperture
sizes of your lenses. And they might be pretty expensive, being much
larger than the one over just the sensor.

On Thursday, 12 February 2015 05:01:35 UTC-5, wrote:
On Wednesday, February 11, 2015 at 10:48:17 PM UTC-5, RichA wrote:
On Wednesday, February 11, 2015 at 2:59:46 PM UTC-5, Uncarollo2 wrote:

pedantic rant deleted

Has anyone ever directly compared a DSLR to a comparably-priced astronomical CCD camera? Same scope, same night, etc?

The comparisons between some DSLR and mid-range CCD seem close enough, at least with well-known objects.

Here is one, somewhat dated perhaps:

http://www.astroacres.com/dslr_vs_ccd.htm

Years ago in one of the mags, there happened to be film images of the M8+M20 region taken through a $$$$ Mak and through a small achro refractor piggybacked on a $$ MCT. The $$$$ Mak photo was certainly better, but the image from the small scope wasn't bad at all.

For many newbies, a $$$$ CCD will remain a dream, whereas a $ DSLR might not.
(That concept eludes ugggaroller.)

True. The first real astro DSLR, the Canon Rebel (early 8mp DSLR with APS sized sensor) can be had used for $40.00 today. A real bargain to cut someone's astro photo teeth on.

On Thursday, 12 February 2015 13:22:31 UTC-5, Uncarollo2 wrote:
On Thursday, February 12, 2015 at 12:11:33 AM UTC-6, Davoud wrote:
Davoud:
http://petapixel.com/2015/02/10/niko...full-frame-dsl
r-astrophotography/

Uncarollo2:
The problem with these multi-megapixel chips is the very limited well depth
and high noise levels. This limits their use in Astro-photography to the
limited number of bright objects. The small pixel size and large pixel count
does not add up to high resolution when it comes to astronomical images.

To give an example, a very faint object may register a count of only 300 out
of 64,000 bits in a 16 bit image using one of these small pixel 35mm chips.
The object will be squeezed into a very narrow range between the noise floor,
say at 150 and the maximum exposure level of 300. That 150 count range then
needs to be stretched into a 16 bit image in order to be processed further.

Contrast that with a similar sized chip consisting of 9 microns or even 12
microns where the well depth is some 5 times larger and the noise level is
several times smaller. That same object will now register at a level of 1500,
while the noise might be down to a level of 50. The range for this object is
then 1450 which is stretched to a 16 bit image with almost 10 times the signal/noise ratio.

True enough, I'm sure. Nonetheless, there are plenty of bright
objects--M42, M45, M1, M31, the Milky Way, Comets, the Moon, and so on,
to satisfy an entry-level astrophotographer using a DSLR. S/he knows
nothing of noise floors, full wells, and the like, but still manages to
produce satisfying astrophotos with a camera that has custom white
balance controls and can thus be used for a variety of other purposes
as well. Tools like Pixinsight and Photoshop help too, of course.

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

Yes of course these cameras do a wonderful job on basic astronomical objects where a full astronomical camera is not necessary and sometimes is inappropriate. I have a little Sony NEX-7 which I've used to take images of the Milky Way that are quite striking for a consumer camera. That said, it has a noise floor that I cannot go below for truly faint stuff. That's mainly a limitation due to lack of cooling the chip.

The NEX-7 wasn't exactly noise-free as a regular camera either.

On Thursday, 12 February 2015 20:56:28 UTC-5, lal_truckee wrote:
On 2/10/15 6:43 PM, Davoud wrote:
http://petapixel.com/2015/02/10/niko...full-frame-dsl
r-astrophotography/

From link:
"Nikon does warn that, due to its modifications, the D810A is not
recommended for general photography."

Yet it's pictured with a terrestrial lens and viewfinder.
What's up with that?

Well, when Leica screwed-up the M8 (their first digital) IR (the sensor has insufficient IR shielding) all they did was add IR rejection filters to the fronts of their lenses. So Nikon could do that, however, the other mods they've made might cause other issues with terrestrial shooting. What I've found from "IR'ing" DSLRs is that using the camera's white balance can restore all colours except for plants which turn from a normal green to bright purple.

On Thursday, February 12, 2015 at 1:05:54 PM UTC-5, Uncarollo2 wrote:

Don't take it personal Chris. Snellieboy is on a raving windmill tilting
journey. He has us all in his sights (you, me, Peterson, Palsing, the video astronomer, and who knows who else).

You have to admit that peterson's

"It isn't a matter of free. It's a matter of accessible without regard
to the ability to pay."

is a statement worthy of ridicule!

Avoid saying stupid things and I will leave you alone.