Camera Labs

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Once you are up to speed it doesn't take too long to get the initial processing done, especially on a fast PC. After that it's just like trying to "develop" any photograph.

I hope you do give this astrophotography thing a go. It's really fun to pluck these images out of an apparently almost featureless sky.

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

But David is not well-equiped with his Nikon (just like me). So he should wait until he gets a D300 or D3 or a Canon...

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Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
D800+assorted lenses

"or a Canon..." - Thomas, are you feeling quite allright?

Seriously, according to Christian Buil (author of the IRIS software and astro-imaging guru) all is not lost for owners of the D70, D80 or D200. From his page COMPARATIVE TEST CANON 10D / NIKON D70 IN THE FIELD OF DEEP-SKY ASTRONOMY we have:

Three different acquisition mode are used with the Nikon D70: MODE 1 = noise reduction option OFF, MODE 2 = Noise reduction ON, MODE 3 = Noise reduction ON, BUT the DSLR is shutdown during the automatic dark frame acquisition. The MODE 3 is unofficial (!), but it is the only solution for take a true raw image with the D70... Details are here:

Mode 1: The reduction noise option is put OFF. At the end of the exposure, the "raw" image is stored into the CompactFlash. But before this, the internal firmware applied a median like filter to the three layers of the image for erase hot pixels (local intense thermal signal). This processing is not mentioned in Nikon documentation, and the fact that it is applied automatically on RAW images is worst news! We will see the consequences. So, the RAW format of Nikon D70 is not a true raw format such as one has the right to await it, i.e. an image which would reflected the outgoing signal of a CCD sensor (via the analog/digital converter). The presence of this numerical filtering explains why the long exposure in the darkness in this mode do not show any sign of thermal signal, which is completely abnormal for CCD specialists.

Mode 2: The reduction of noise option is ON. In this case the DSLR take two successive frames. The first with the shutter open during the time requested by the operator. The second with the shutter closed, of the same duration. The second image is subtracted from the first and the result is stored in the CompactFlash card. It is the traditional technique used in astronomy for remove the thermal signal. But generally the operation is made a posteriori to avoid doubling the observation time. MODE 2 is far from practical for astronomical observation, where time is always counted. But moreover, Nikon engineers adds an operation: the median filter is also applied AFTER the dark frame exposure!

Mode 3: This mode preserve the CCD full resolution for astronomical long exposure applications. The first part is identical to the MODE 2 (noise removal procedure is ON), but for going until the end, it is necessary to turning off the power switch some fraction seconds or some few seconds after the first acquisition phase, i.e. once that the shutter is closed and that the D70 carrying out the dark frame. There is no risk to damage anything. The firmware of D70 automatically saves the image stored in the buffer memory on the CompactFlash card. It is a safety measure if the user cuts off the power supply without taking guard there. Now, the D70 save an absolutely true raw image. This RAW image is equivalent to a true CCD image, which it will be possible to process in-depth. Within the framework of a use automatically, a small electronics and a servomechanism which acts as switch at the level of the concentric on/off button can be developed. It is also probably possible to use a wired solution but it is necessary to open the camera (see web site in reference at the end of this page - the operation seen to be complex...).

Sorry for the length of this post but I thought it better to quote Christian's own words (he's French by the way) rather than try to paraphrase.

Thomas, I wish I had known this before your New Zealand trip.

So owners of the D80 and D200 (and yes, this does apply to those cameras) don't have to buy that Canon after all...

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

And a handy but powerful telescope !
It will be sometime before I can test one out.. though.
Maybe when I and IF I travel to the Nation Capitol City.

oh oh - and a beefed up wallet to go !

Based on your thread, (Thomas and Bob) Here I might have to go Canon before I can venture into this.

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Nikon D7000 and a bunch of Nikkors

But don't forget that the images I have posted in this thread don't use my telescope's optics at all.

I have been looking very closely at my original RAW images (normal and dark frames) and I agree that there are more hotspots than is comfortable. Looks like I'm going to have to run a few test sessions at shorter exposures. While I can obviously reduce the hotspots that way the trade-off will be how quickly I lose the ability to see any faint nebulosity.

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Yes, you don't need a powerful telescope, but you need a powerful auto-tracking rack (or whatever it's called)

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Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
D800+assorted lenses

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It should be possible to add a motor-driven equatorial mount to your arsenal for under £200/€300/$400. My own mounting (illustrated below - clickable) is the next one up the line and cost under £300/€450/$600 and that included dual axis motor drive (you only need single axis for DSLR "big sky" astrophotography) and a polar alignment scope. Polar alignment scopes are very useful to get the polar axis aligned with the Earth's axis (by sighting on the star Polaris) but only in the Northern Hemisphere! Of course, once you get the mounting it is very hard to resist getting a telescope to go with it rather than be content with just mounting plus camera.

Returning to my last set of images, I thought it might be of interest to show the first and last shots from my 22 image session. Each image was a 2 minute exposure and there was typically a 30 second interval between images. Air temperature was around 8°C.

First


Last


These are scaled down versions of the JPEGs saved together with each RAW image and the colours are exactly as they came out of the camera. The colour shift as the sensor warmed up is very noticeable. It's a moot point whether I would have been better off spending my hour taking just 11 images, instead of 22, and allowing a 3 minute cool-down interval between each image. The pictures also show how severe the vignetting was and why using a "flat field" is essential to help balance the final result.

So many options. So many ways to get it wrong.

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Hi Bob, the colour balance differences are quite dramatic there - could you reassure me these are not differences in applied white balance though by quickly checking the RAW files using exactly the same WB settings in your RAW software?

Hi Gordon,

The camera was set up in RAW + Large Fine JPEG and daylight white balance and landscape style would have been applied to the JPEGs by the camera. The only processing I have done to these JPEGs is to reduce the size. I used Microsoft Office Picture Manager (it was handy). I see the same colour shift when viewing the original full size JPEGs.

It might be of interest to display the entire sequence. The first is top left and the sequence is left to right with a new row after every fourth image. The EXIF data is all intact so you can extract the entire time line if you want but, as I mentioned before, each exposure was of 2 minutes duration and there was usually around a 30 second interval between the end of one exposure and the start of the next. The camera was exposed to outside temperatures for very roughly about half an hour before the first exposure (but some Live View focussing was done during that time).








The shift appears to have reached an approximately steady state after 14 or 15 exposures.

It was already completely dark before the first exposure was taken so ambient light was essentially constant. Subjectively the outside air temperature fell several degrees Celsius during the session. It's difficult to be sure but it seems that a two hour session with a high duty cycle of exposure time is sufficient to pretty much discharge a full battery so it is my assumption that the effect seen is due to the sensor getting quite warm.

Any thoughts?

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Well I agree on this - but I don't think any shops will sell only the 'legs' without the telescope.
I will only find out when I get to the Nation's Capitol.

Also - it may not be much but Bob
The amount translate to local currency is HUGE £1 roughly local $7

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Nikon D7000 and a bunch of Nikkors

Hi David,

Sorry, I was quoting US$, not Malaysian $. Of course the precise $ value is less relevant than the price as a percentage of income.

Buying telescope mountings without a telescope is not at all unusual. Many amateur astronomers prefer to "pick & mix" in this way.

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Hi Bob
Not to worry - I will definately give this astro-photography a go one of these days. I am quite intrigue by all the stars and how minute we are in this Universe.

Oh . that figure is relatively 20% of my monthly take home pay. Well what can I say. cheap labour here !

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Nikon D7000 and a bunch of Nikkors

Hi folks,

The image processing done courtesy of IRIS for the images posted above included use of a function designed to emphasise nebulosity. This time I went back to the original RAW files (there are thumbnails of all 22 posted above, each a 2 minute exposure on a EOS 40D at ISO400, f/1.2 with an 85mm focal length) and concentrated on getting a more accurate representation of the star field.

Clickable for the pixel-peeper's full resolution download (4.4MB)

The images were stacked using manually selected registration points and I removed the background gradient as well as compensating for vignetting. I also tried to get the colour balance looking a bit more natural (still a bit more cyan there than I would like) but I have boosted the red a little to emphasise the natural red colours in the nebula. In common with most DSLRs, my 40D has an infra-red filter in front of the sensor which, unfortunately for astrophotography, cuts out the strong deep red hydrogen alpha emission line which is characteristic of many nebulae. Without that filter I could have left the red channel alone. For the budding astrophotographers out there I hope that at the least I have demonstrated what a huge difference post-processing can make to the final result.

Anyway, I reckon I have worked this set of images to death (did someone mutter "hooray"?) so I guess it's time to get the camera out again.

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Hi folks,

Hopefully if you are reading this thread you have a passing interest in astronomy as well as photography. My recent posts have concerned the North American nebula. This post is veering a little off topic so very quickly there are two other really interesting objects in the picture above. Both are stars and both are about three quarters of the way across the frame.

The brightest star is Deneb (Wikipedia). It is about one quarter of the way up from the bottom. It is about 60,000 times more luminous than the Sun, has a surface temperature of about 8,400 Kelvin (the Sun is around 5,700 K) and check out its size:

The second is much less spectacular but extreme in its own way. Go up from Deneb in the picture and about halfway up there is a very red star - so red you might think it was a stuck pixel. Not so: the star is "V Cyg" (Cyg is short for Cygnus; the SAO number is 49940) and it is a Carbon Star. Carbon stars are evolved cool giants (but sometimes dwarf stars) with circumstellar shells or clouds of carbon dust material. Typical surface temperatures range from 2000 K to 3000 K. If you want more there is an article on Wikipedia.

Next time you go out at night watch out. You never know what's lurking above you.

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

Hi Bob, nice extra info - thanks!

Quick question concerning the star images. I noticed in your (and my own) long exposures that star images can often look quite electronic, and sometimes almost square-like. I realise the actual pixel locations on the sensor are smaller than the spread of the star using our optics and atmosphere, but wondered what your take was on this.