In Plain Sight
For all my Rods & Cones I still cannot see what is in Plain Sight . . . .
So why is this and so many other Deep Sky Objects (DSO) hard to see? Even DSO‘s that are as large as the Full Moon (as viewed) in size. Well kido’s it all has to do with what’s inside your and my eyes . . . oh did I mention that what we do see when observing some of these nebulae we see in shades of gray! for the most part, and that too has to do with your eyes and their sensitivity to the low levels of light and its colors.
The retina contains two types of photoreceptors, rods and cones. The rods are more numerous, some 120 million, and are more sensitive than the cones. However, they are not sensitive to color. There is much more online about the eyes and what wonderful things those are . . . I treasure mine, but, let us get back on track and talk image capture and what hides in front of us.
Yep, all that light, speaking of which, the light in the photo above that I captured last night is what the Stars in that cluster are exciting the dust and gasses that surround them. The Stars are very young and will eventually consume or dispel most of the dust and gas to eventually look something like the Pleiades Star cluster . . . Now in the case of the Rosette Nebula and others like it is that it is in a class of nebulae that are called emission nebulae. Emission Nebulae emit light due to their makeup. An emission nebula is a cloud of interstellar gas and dust that emits light in different colors. There are several different types of emission nebulae with diverse sources of energy that are responsible for the glowing of gas and dust. The Rosette Nebula glows in several colors mostly from these elements mostly from Hydrogen (Red ), some Sulfur (blue) and Oxygen (green). The center is clear due to the solar winds created by the central stars. A look at a photo made from the Hubble will show these other colors in a spectacular image. To do this would require photos taken with a monochrome camera with specific filters used to record emissions in only those colors. I used a color sensor (digital camera) which is not sensitive enough to record them, I used a UHC/LPR filter to reduce the local light pollution.
The Nebula covers the field of view equal to about the same size as the moon on the sensor, again, because our eyes are not sensitive enough we can barely if at all see it (city dwellers cannot see any traces of the nebulousness because of light pollution) and that would be at a dark site. The nebula is about 4700 to 5000 light years distant. So just when did that light leave the Nebula? well the light we see today left it sometime during the time that the Great Pyramid of Giza was built and the first version of Stonehenge was constructed on the Salisbury Plain (England). So I am photographing ancient light.
The star cluster at the center of the Rosette nebula is the NGC 2244 cluster. This young, bright Blue white star cluster is responsible for creating the hole at the center of the nebula. The intense radiation from the stars has blasted away the gas around them. The intense radiation from the stars is what causes the gas clouds surrounding them to glow red.
I used a non modified DSLR to capture the previous photos, the second photo required multiple shots at 105 seconds each, which where then stacked using a special program called DeepSkyStacker (DSS) a freeware program that registers, stacks and allows for some minor processing, this compiles an intermediate tiff file which is then post processed in other programs such as CS, Corel PSP or GIMP photo editing software used to adjust the file to bring the data up to a usable photo. The data is very compressed and one has to stretch the levels. So with a few hours of captured data, one can expect to spend a few hours in post processing (yup expect some flat butt time behind the old computer screen). Color is a bit subjective, I will not get into this debate here, Reddish to pink is the color range for this nebula, to produce those Hubble style photos you need a mono camera and a special filter set (the Hubble pallet is unique), the more data captured equals more detail in your photo. One shot color DSLR captures are not as detailed as mono chrome cameras or modified DSLR’s but one shot color is less work for a color photo. Fun Fun Fun . . . one learns that those wonderful and beautiful photos that grace those Astro magazines are not what one sees through a telescope for the most part . . . Nebula are mostly invisible and if visible at all are usually a ghostly gray . . . because they are so dim you really need to be at a dark site to see any visually . . . the easiest one to see with the naked eye is the M42 Orion Nebula . . . and in a dark site you can see some color.
This post is meant to introduce capturing emission nebula with a non modified DSLR. You can image them with a standard camera lens in the range from 85mm to 200mm and some form of tracking to minimize star trailing. I would very much recommend a GEM (German Equatorial Mount) mount to easily locate the objects like emission nebula or other dim objects. A computer controlled Mount is even better (GOTO mount) and data is more accurate.
Here is the equipment list I used to capture the above Photo.
- Nikon D7000
- appropriate camera T adapter & extension to reach focus
- 2″ UHC/LPR filter to reduce light pollution and increase contrast
- Orion ED80 f/7.5, focal length of 600mm, 3.15″ (80mm) telescope
- Celestron AVX mount
Here is a list of the software and general post processing chain
- DSS align and stack light frames, Dark, Bias (TIFF)
- LR4 stretch the histogram and adjust levels (TIFF)
- On1 color and contrast and noise adjustments and final print sizing (TIFF)
- Corel PSP 8X to process file for Internet usage (JPG)
I would spend less time post processing my landscape and wildlife photos then one DSO photo. I would suggest to anyone wanting to follow the path of Astro Photography, read, read, read. Educate yourself before you ever purchase anything other then a book. There is a hidden “Nickle & Dime” factor that isn’t as obvious and there is a quality verses cost factor not mentioned. I am pushing every piece of my gear to or beyond its limit to produce a few photos. I enjoy a challenge, but if you have even a hint of defeatism, depression or struggle with challenging and ever changing requirements, lack of sleep, then DSO Astro photography is NOT for you. Stick to star trails and light painting at night . . . you’ll be happier in spirit and wealthier in your wallet. I’ve managed to keep things in my budget so far, but I have come close to throwing my plastic to the wind and going all out, but having a roof over my head, staying married and the need to eat have all weighed in to keep me firmly in check. Yes you can do it on the cheap if your willing to buy used, educate yourself and define your niche you can make some pretty cool photos that will blow your friends minds. Well I’ve blown enough time on this post, the weather is looking promising for tonight . . . except it may be cold. Have fun, I hope this post was a fun read and possibly educational and inspiring . . . Astro photography is a major challenge, it is very addictive and very much rewarding when you get it right.
OK . . Digi is outta here . . . until next time “get off your duff and go out and shoot some film”