Here is my first successful image of M31 (Andromeda galaxy) from last January. Of course it also includes the small elliptical galaxy M32 (left of Andromeda's center) and the slightly larger elliptical (spherical?) galaxy M110 (below and to the right of Andromeda's center). I had tried to image Andromeda previously from my very light-polluted backyard in Sunnyvale, CA with rather miserable results. This image was taken at a reservoir about a one hour drive away where the sky is noticeably darker. Lens: Nikkor 300mm f/4 ED AFS Aperture: Approx. f/6.8 (manually set between 5.6 and 8) Camera: QHY-8 (6MP dedicated CCD astro-camera) (Note that the camera's sensor is the same physical size as the Nikon DX cameras) Mount: Orion Sirius GoTo equatorial mount Guide scope: Orion Short Tube 80 Guide camera: Orion StarShoot Autoguider
This image is a stack of 27 10-minute sub-exposures taken over two nights, captured with Nebulosity software and processed with Nebulosity and PixInsght. Earlier attempts with the Nikkor 300mm lens at wider apertures showed considerable coma on stars away from the center of the image. Even at f/6.8 there is still some visible coma, but nowhere near as bad as at wider apertures. Because the images from the two nights were not centered exactly the same, there was some cropping done to eliminate the areas where the stacked images did not coincide. I am still learning to process astroimages, and especially having trouble with color balance, but this was the best I could do. I plan to try this target again to see if I can improve on my results.
You did that with just a 300mm?? I was thinking a big scope, maybe a 6 inch refractor or a large SCT. I guess I better get outside and start really looking around. Would help if the stupid weather would cooperate!
#3. "RE: M31 Andromeda" In response to Reply # 1 Sat 20-Oct-12 11:45 PM by RABaker
"You did that with just a 300mm?? I was thinking a big scope, maybe a 6 inch refractor or a large SCT."
Andromeda is about 2 degrees wide, or about 4 times as wide as the full moon. It is best imaged with a moderate focal length telescope or a photographic telephoto lens (or a longer telescope with a focal reducer). With a DX-sized sensor the 300mm lens gives a reasonable sized image of Andromeda while also including some of the "environment." For us in the Northern Hemisphere I think Andromeda is the only galaxy that comes close to this size - most galaxies are pretty small and do need much longer focal lengths to image well. However, there are many other faint deep sky objects that are large enough to also be good targets for telephoto lenses (or short telescopes). For instance, I recently captured some frames of the North America Nebula with the 300mm lens and I hope to finish the processing this weekend (if I can find time from my chores).
#5. "RE: M31 Andromeda" In response to Reply # 4 Sun 21-Oct-12 02:59 PM by RABaker
The QHY8 camera uses a 6MP DX-size CCD sensor made by Sony (some say it is a close relative of the sensors used in the Nikon D40 and D50). In many respects the QHY8 (and any so called "one shot color" astro camera) is similar to a shutterless DSLR - it uses software to control its exposure time rather than an electro-mechanical shutter. Probably the biggest optical difference is the IR filter. As far as I know, all DSLRs (except a couple of Canon models aimed specifically at astrophotography) have an IR/UV filter in front of the sensor that is broad enough that it unfortunately cuts out some of the red light near the edge of the visible spectrum. As a result, most of the DSLR astroimages are somewhat deficient at the red end of the spectrum - and, depending on the IR/UV filter used, some are also deficient at the blue/violet end. As far as I know, all dedicated astro cameras use either no filter at all, or a much more narrow IR filter to be able to capture more of the available red light.
Another difference between the QHY8 and a DSLR is that the QHY8 does not have any built in color balance settings - it cannot be set to Daylight, Tungsten, etc. The photographer must adjust color balance of the image in post processing. This is one of the areas I am still struggling with at times. Also, the QHY8 must be connected to, and is completely controlled by, a program on a computer - it has no ability to function on its own. That brings with it the need to have a laptop with you when imaging.
I originally began astrophotography with my D200. After a few months, I decided that I wanted a dedicated astro camera in order to capture more of the visible red light and, hopefully, present a more "natural" color in the resulting images. I bought the QHY8 used as a *relatively* inexpensive step into the world of dedicated CCD astro cameras.
This was shot from the boat ramp parking lot at Coyote Lake near Gilroy. From my home in Sunnyvale it takes about an hour to get there in "normal" traffic - during rush hour more like an hour and a half. Here is a link to The Astronomy Connection (TAC) home page (a Bay Area online astronomy group): http://observers.org/ At the top of the home page under the heading "Observing" you will find a link to "Sites." This will take you to a list of about 15 or 20 observing/imaging sites in the Bay Area (and a few outside the Bay Area) along with some information about what restrictions may exist at the various sites.
Just for information: There is a restroom building with some relatively moderate lighting that remains on all night and a malfunctioning brighter light that comes on and goes off all night long on a cycle of about 80 to 90 seconds. These lights are on the western side of the parking lot and I believe they have little or no effect on images made primarily on the East side of the meridian - and that is the darkest part of the sky anyway. However, the light is bright enough that it can and will affect a person's ability to become dark adapted, so I believe this site is better for imaging than observing.
This is impressive. I'm going to have to learn about this image stacking software. I've wanted to do a little astrophotography, but clear skies very common here. Images like this make me want to try some more.
#14. "RE: M31 Andromeda" In response to Reply # 0 Wed 06-Feb-13 03:52 AM by glxman
South Australia, AU
Truly amazing image Richard, Got me all exited there for a while, Ive also got a 300 f4, Reading further down your post and subsequent google results soon showed me that there could be a "fiscal cliff" I would eventually fall over!
Thank you for sharing, even with all the "gadgets", you have shown an incredible skill, Regards, Gary