So, What is the Nikon Project?
In early 2013, I saw an ad on AstroMart for a "monofied" Nikon d90. The imaging chip in the Nikon was modified by a fellow in Canada to turn it into a monochromatic chip. Essentially, the microlens and the color filter array are physically removed from the front of the chip. What remains after the removal is actually just a black and white chip. All imaging chips in consumer DSLR cameras are basically monochromatic chips with the microlens and color filter arrays added.
Anyway, in the case of the Nikon d90, after the modification, you end up with a camera with a very large, 12 megapixel monochrome imaging chip. One advantage of the modification is that the sensitivity of the camera is significantly improved. These benefits, large chip size and sensitivity, should make the "monofied" Nikon a stellar astrophotgraphy camera. I think it was the image below that sold me on the idea of purchasing a "monofied" Nikon camera. On the left is an image taken with an unmodified Nikon, and on the right is the same image taken with a "monofied" Nikon. What a difference!!! Since I have now seen the degree of sensitivity from the Nikon d90 I purchased, I believe I can testify to the reality of the image below...
I envisioned using the "monofied" Nikon d90 as my primary camera for narrowband imaging from my very light-polluted driveway in Tempe, Arizona. I was already imaging from that driveway using the Hyperstar lens system mounted on an N11GPS telescope, while using a Canon DSLR and a light pollution filter. I figured that the increased sensitivity of the Nikon would enable me to use a similar set-up and add narrowband filters to the mix. Everything was progressing according to plan until I received my Hyperstar Nikon camera adapter from Starizona. Unlike the Canon Hyperstar adapter, there is no place on the Nikon adapter to screw in a 2" narrowband filter. Oops!!! I must say, I was disappointed that my plan wouldn't work the way I envisioned it.
And then I remembered that I had tried the same thing (narrowband imaging) with the Canon and an Astronomik clip-in Ha filter. The results had not been particularly encouraging, but I still had that EOS clip-in filter. Naturally, the filter was designed for the interior architecture of the Canon and did not fit properly in the Nikon, but it was close. So close, in fact, that if I turned the filter 90 degrees, it would fit in the Nikon. A downside to that solution is that the filter opening is wider than it is tall to accomodate for the shape of the imaging chip. Turned sideways, I am going to get some vignetting on my images. Also, the filter was still lying a bit loose in the body of the Nikon, but not too much so. I cut two "washers" out of cardboard stock and placed them atop the filter and that eliminated the movement of the filter within the camera body. You can see my rather inelegant solution below. What can I say, it works.
Nikon cameras have never been used as much as the Canon cameras for astrophotography. Because of that, I have had another obstacle to overcome. I think the main reason for the popularity of the Canon over the Nikon in astrophotography has to do with the earlier ability of the Canons to handle "bulb" imaging, that is long exposures, with a single USB connection. The Nikon requires two cables, one a rather expensive custom made affair, to enable computer controlled long exposures. So, very few developers seem to have tackled the need for astrophotographic software packages designed for Nikons. There are a number of software packages for the Canon, but its pretty thin and mostly expensive solutions for the Nikon. What we are talking about is "tethering" software.
There are a number of tethering software packages for the Nikon, but they are designed to be used in portrait studios and have had no need to enable bulb exposures. Those programs all have a max exposure time of 30 seconds. Now it just so happens that 30 seconds is a reasonable exposure time for a Hyperstar equipped N11GPS. Oh, 45 seconds would be nice, but 30 seconds will work. The N11GPS is an alt/az mount, so anything over one minute will usually result in stars showing up as streaks rather than round dots. I have been using an inexpensive piece of software called "Control My Nikon" to tether my camera to my netbook in initial testing. Some aspects of the software do not work particularly well in an astrophotography setting, but the included digital Intervalometer makes up for many of the other short-comings. The intervalometer is easy to use and allows me to program a series of exposures and then just let the laptop computer control the camera.
That info now needs to be updated. "Control My Nikon" has released a much improved version 4.3 that enables "bulb" exposures. Now, only a few Nikon cameras can handle bulb exposures with just a USB cable and the Nikon d90 is not one of them, but supposedly the program is also compatible with the DSUSB from Shoestring Astronomy. I can not verify that as I haven't gotten mine to work that way, but I have found that a simple programable and CHEAP hand held intervalometer works great with the new version of the software package. So, you use sub-30 second exposures to align you scope and focus your camera, then start using the hand held intervalometer to control the camera with plus 30 second exposures. Trust me, it works pretty well...
I did run into another little problem. My Nikon is producing mono RAW image files. Now, nobody ever did that before, at least not to any great extent. All the usual software packages designed to process digital images assume that a Nikon RAW file needs to be debayered (colorized). They even insist on doing that with my mono files. Not a good solution. However, it turns out that one fellow (Dave Coffin) did create a little piece of software that is able to handle just this situation. And it's free. Naturally that is not the end of the story. To read the rest of this little story, you will need to go here. I promise a good ending to the story...
So, how does all this work under the sky at night? I think my initial experiences have been very promising. Since I have finally figured out how to focus the camera while it is installed in the Hyperstar (one of those short-comings of "Control My Nikon" that I mentioned) I think I now have a few images good enough to share. So finally after all this talk, we get to the good stuff.
The first image I want to share is an Ha image of NGC 2359, Thor's Helmet. I am showing this one first because I have tried to get NGC 2359 before, with the Hyperstar and the Canon using only a light pollution filter in place, but I was unsuccessful. The object was just too dim to show up from the background noise. The image below, taken on 3/12/13, is a stack of 30 second exposures, stacked in Deep Sky Stacker, and processed in Nebulosity 2, and Adobe Photoshop. This is the only image of Thor's Helmet I have ever taken and I am pretty happy with it. OK, it could probably be improved with longer exposures, but this ain't bad given my equipment and methods...
This next image is also of NGC 2359, Thor's Helmet. It is just a newer version, taken since I have gotten some additional narrowband filters and perhaps improved my processing skills a bit. Hope you like it. The data from the top image was incorporated into this Ha and Oiii image. By the way, the Oiii subs were taken at an exposure time of 50 seconds using the new method of controlling the camera described above.
This next image is of NGC 281, the PacMan Nebula. It is also in the Sharpless Catalog as object Sh2-184. This shot was taken on 10/3013 from the driveway in Tempe. Once again, this is a stack of 30 second Ha images taken with the Hyperstar and the N11GPS. I can't say much for my processing but you have to admit, this is a pretty good image for a stack of 30 second subs using a Ha filter.
This shot is of the Rosette Nebula, NGC 2239, also known as Sharpless Sh2-275. Again, this is a stack of 30 second Ha images taken with the monofied Nikon d90, using Hyperstar and the N11GPS. The image was taken on 3/10/13.
This next shot is of IC 443, the Jellyfish Nebula. It is also known as Sharpless Sh2-248. This shot was taken on 3/6/13 with the "monofied" Nikon d90 and the Hyperstar equipped N11GPS and is a stack of 30 second Ha exposures.
This week I managed to acquire an Astronomik CLS Clip-Filter to use in my Nikon d90. This image is "first light" with that filter in the camera, replacing the Ha filter. All of the above Ha images were taken with 30 second subs and an ISO of 1600 on the Nikon. With the CLS filter in place, the exposure time was reduced to 20 second subs, and the ISO was set at 400 or 200, depending on the object. Because of the light pollution in Tempe, exposures longer than 20 seconds just ended up being washed out, even with the CLS filter in place.
The image of the Whirlpool Galaxy, M51, was taken from the driveway in Tempe with the N11GPS using the Hyperstar 3 lens system. My equipment, including the "monofied" Nikon d90, combined with my urban location seems much better suited to taking wide-field images of large emmission nebulas through narrowband filters. But I think this image demonstrates that the same equipment can also be used for some of the brighter "faint fuzzies" in a pinch...
Recently, I purchased an Astronomik Oiii clip-oin filter to use in conjunction with my Ha clip-in filter. My goal is to produce narrowband color images with the Nikon. For my first efforts, I have created false Sii images that are combinations of the Ha and Oiii images. I then used the three narrowband images to construct an RGB image.
The image of the Dumbell Nebula, M27, was taken from the driveway in Tempe with the N11GPS using the Hyperstar 3 lens system. I must say that I am pleased with the results from a purely asthetic standpoint.
This next shot is of Caldwell 27, the Crescent Nebula. Taken in narrowband with the Nikon d90 using the N11GPS. This image was taken on 6/16/13 using the Hyperstar system, and has be artificially colorized using PhotoShop.
I will be adding images to this page as time goes on. If you want to read more about the subject of "monofied Nikons," I would point you to a discussion on one of Cloudy Night's forums. You can find it here.
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