Carina in H Alpha with EasyHDR

[avandonk]

Did a test last night and since the Moon was interfering used an Astronomik 13 NM H Alpha filter.
It was also very cold and when I started imaging ambient temperature was 7.2 deg C and at finish 3.2 deg C. I have also mounted a 80mm 0.7 A 12V fan to blow ambient air onto the 5DH. This does drop the internal temperature of the camera by a few degrees and consequently lowers thermal noise.

Large Image 1.6MB
http://members.optusnet.com.au/~avan...EHDR_HA_5C.jpg


Details
Canon 5DH, Canon 300mm F2.8L at f/2.8 and 500ISO, in camera noise reduction (ICNR) ON, 5X( 1M, 2M, 4M, 8M).
Used ImagesPlus to convert from RAW to TIFF and flat corrections and digital development. Then used Registar to median stack each exposure set and produce perfectly aligned versions of each exposure stack which were then processed using EasyHDR to produce a HDR image and then convert to an LDR image. Levels adjusted in PS only red layer used.

This has the result that the bright regions of the nebula are not blown out and the very dim regions show clearly. Noise is almost entirely absent due to the low temperature, ICNR and median stacking.

I am converting a peltier fridge to cool the 5DH so I have more control over camera temperature rather than rely on Melbournes cold clear nights.

Bert

[leon]

Bert, that is an awsume shot, love the colour.

Leon

[ballaratdragons (Ken)]

Wow, Bert, Fantastic. The amount of detail in the Nebula picked up by the H-alpha filter!!!
Wierd seeing the stars red too.

Amazing image.

It shows how bright Eta is, it shines white even thru the filter!!!!

[Ric]

Lovely image Bert, the fine detail showing through is amazing.

top stuff

[tornado33]

Great work there Bert. I must try the HDR process, as currently I just mask a bright burnt in image, with a dark one showing only the bright parts, in order to get a shot that shows faint outer areas and bright regions fully, using Goussian Blur on the mask. It is a bit hit and miss though, sometimes having to have a few trys at it to get an acceptable image, so the HDR process might be the go.
Yes the advantage of peltier cooling is not just less noise, but control. Taking the dark frames and light frames all at the same temperature ensures very accurate dark subtraction and thus more boise free images. With Houghys cooled DSLR I would slowly back off the cooling as the night wore on to try to keep the sensor temp the same throughout.
Scott

[seeker372011 (Narayan)]

Ok I'll bite. I'll admit I didnt know what HDR stands for...but HDR is High Dynamic Range..thats what google tells me.

anywhere where the actual technique is described? is this something you developed? any details as to what you actually do?

thanks in advance

[Dennis]

Hi Seeker

In Photoshop CS3 there is a “Merge to HDR” function which works as follows:

When you have a scene that contains deep shadows and bright highlights, a single exposure cannot manage the full range of brightness levels, so either the shadow areas are black and show no detail, or the highlight areas are completely white and burned out.

Photoshop CS3 can compensate for this. For a terrestrial scene, using a tripod mounted camera, you expose 3 or 4 images at the same F stop, but varying the shutter speed for each image.

Image #1 has a slow shutter speed (e.g. 1/30 sec) so that detail is revealed in the shadows.
Image # 2 is exposed at say 1/60 sec for the mid tones.
Image # 3 is exposed at say 1/125 sec for some highlights.
Image # 4 is exposed at say 1/250 sec to show e.g. details in the sky and clouds.

The CS3 HDR function then automatically combines all 4 photos, using the correctly exposed shadows in Image #1 through to the correctly exposed highlights in Image #4.

Hope that makes sense!

Cheers

Dennis

PS - Have a look here http://www.luminous-landscape.com/tutorials/hdr.shtml for a CS2 tutorial. It shows a 7 frame blend from almost black to almost burned out, and how they were combined to produce quite a pleasing final photo showing the full dynamic range.

Here is an astronomy example http://www.astropix.com/HTML/J_DIGIT/PS_HDR.HTM

[seeker372011 (Narayan)]

Many thanks Dennis..I'll study the CS2 tute carefully
Narayan

[tornado33]

Hi, I opened it in Photoshop and using just the red channel turned it to grayscale. Lots of nebulosity there.
Scott

[avandonk]

I have not had this much fun for quite a while. h0ughy's camera and Scotts expertise has given me evil thoughts of trying to be cool! I only put this up to show the result of the experiment.
I am now trying to come to grips with HDR imaging and cooling at the same time. I only put up this image to show what is possible in the hope it would give others some ideas.
In the meantime watch out for future images.

Yes nice conversion to B&W Scott. I did not want to go there as I thought I would get the troops used to seeing more RED.

Bert

Thanks for all the comments!

[Dr Nick (Nick)]

Wonderful!