The Ring Nebual (M57) is a planetary nebula in the constellation Lyra. The image below is a composite stack of nine photos taken the night of October 24, 2009. Each individual photo was captured at f/10, ISO1600. Total exposure time is 9×30sec, or 4 min 30 sec.
M57 - Ring Nebula
Location: at home in Tomball, TX
Cloud cover: less than 5%
Transparency: average (3/5)
Seeing: below avg (4/5)
Darkness: no moon, city glow
Wind: almost none (see below)
Temperature: 70º-72º
Humidity: 95%+
Dew Point: 69º+
Time: 10:45 pm – 12:15 am CDT
OTA: 8″ SC
First light using Starry Night Pro to control the telescope via serial cable. I have an old version of SNP (4.5) and there are a few minor user interface quirks, but generally I was pleased with the operation. Also first light using DIYPhotoBits to control the Nikon D50 via USB. I was very pleased with the results. I’ve actually modded DIYPB to display images after download using IrfanView, making it much easier to center and check focus.
I started with M57, the Ring Nebula. Exposures above 10 seconds exhibited elongation. It didn’t occur to me until later to use DIYPB’s time lapse feature to collect a set of images for stacking, so I only captured two at that speed. M57 is hardly visible at only 10 seconds, even using ISO1600, so there’s not much to see there.
Next I captured photos of Jupiter and the Galilean moons. Due to the bad seeing and the humidity the image quality was quite poor. The two main bands were visible but murky and the entire image seemed slightly out of focus. I rechecked the focus with the Hartman mask and that was not the problem. The composite photo below shows the relative positions of the planet and its four moons. Io and Europa (on the left) passed in conjunction over the next couple of hours, but it was already late and I didn’t want to stay up for it.
Jupiter and its moons (composite image)
Last I photographed M52, an open star cluster in the constellation Cassiopeia. As earlier with M57, I was unable to get an exposure longer than 10 seconds without elongation. It occurred to me then to use DIYPB’s time lapse feature to take several photos (10, actually) in quick succession then try to stack and merge them later. I tried stacking with RegiStax5, but I was not pleased with the results: the stars looked dull and washed out. I stacked the frames by hand and the result was much better.
Composite image detail of M52(click image for 1000x800 resolution)
This image shows far fewer stars than you might see in a typical photo of M52. This view is representative of what you might see in an amateur telescope. You mileage will vary depending on your telescope and sky conditions.
Tonight I tried my hand at photographing a few Deep Sky Objects. The Hartman mask was extremely useful for focusing, but after tonight it’s clear that I’m going to need to control the D50 by tethering it to the laptop to get best results. Manipulating the zoom controls for the LCD is awkward at best. I may need to spend some time just practicing focusing on a few different stars.
Saturn was actually the first target before the DSOs. I captured a couple of images at ISO 800 and 4 sec exposure that included the moons Titan, Tethys, Dione, and Iapetus (Rhea was transiting and lost in Saturn’s glare). I reduced the exposure time several steps, but it was hard to see much detail in the LCD (another argument for tethered control), so I moved on.
Next I tried M13, the globular cluster in Hercules. This actually turned out to be the best subject of the night. One of the photos had some jitter from the wind shaking the telescope (did I mention it was occasionally quite breezy?). Most were fairly good, however, with nearly round stars — limited by the sharpness of the focus, most likely. Click the image to see a very large full-sized photograph. If you look closely you can see stars of several different colors in the cluster. M13: FL 2032mm, ISO 800, 30sec exposure, f/10.
M13
Next came M57, the Ring Nebula in Lyra. I captured several images, but they all showed noticeable wind jitter. I’m certain this is telescope vibration and not tracking error because the motion vector varies from one photograph to the next. I merged the four best frames in Registax, stretched to compensate for the motion vector, applied a gamma correction to increase the brightness, then reduced the image size to improve the apparent sharpness of the focus. M57: FL 2032mm, ISO 800, 30 sec exposure, f/10.
M57 - The Ring Nebula
The next target I tried was M27, the Dumbbell nebula. However, even with a 30 sec exposure at ISO 800 there was almost no trace of any nebulosity in the photo, so I moved on.
I decided to re-balance the telescope forward to compensate for the extra weight of the camera on the back. This, of course completed wrecked the scopes alignment so I had to restart. After alignment I focused the camera on Mizar (ζ UMa). It’s a nice blue double, but it’s included here for more than aesthetic reasons. According to SNP, the separation between Mizar A and B is 14 arc-seconds. In the unprocessed photo, the distance between the centers of the stars is approximately 19.3 pixels (along a diagonal). This puts the resolution for the camera at about 0.725 arc-seconds per pixel. By comparing similar measurements of other doubles I should be able to calculate the actual resolution more accurately. Mizar: FL 2032mm, ISO 800, 1/2 sec exposure, f/10.
Mizar A and B
After rebalancing I Attempted several images of the Whirlpool galaxy M51. The cores of M51 and its companion galaxy both appeared tiny and featureless over several photographic attempts.
Location: at home in Tomball, TX
Cloud cover: 0%
Transparency: n/r, est. average (3/5)
Seeing: n/r, est. poor (2/5)
Darkness: no moon, city glow
Wind: light, less than 5 mph
Temperature: 75º+
Humidity: n/r
Dew Point: 45º-55º
Time: 8:45 pm – 10:00 pm CDT
OTA: 8″ SC
ε Boötis DBL very close pair, cannot split in 12.5mm except in rare moments of good seeing (poor seeing generally), appeared as oval with red and blue sides. completely blurred in bad seeing.
M81 GAL UMa very faint fuzzy with no detail.
ξ Boötis DBL est. mag 4 white and mag 5 orange, close pair easily split in 12.5mm. Wikipedia lists ξ Boötis A as 4.5-4.7 G8 variable and 7.0 K4.
κ Boötis DBL est. mag 4 blue and mag 5 /yellow, close pair easily split in 12.5mm. Wikipedia lists them as 4.5 A8 and 6.6 F1.
M3 GC west of M13 (which was behind the house in the NE 
) – wide fuzzy, no individual stars visible.
Mizar DBL est. mag 2 blue and 2.5 white. close pair easily split in 12.5mm. Wikipedia lists them asmag 2.2 A1 and mag 4 A7.
Cor Caroli DBL est mag 2 blue/white and mag 3.5 yellow/green, another easy split. Wikipedia lists them as mag 2.8-3.0 variable A0 and mag 5.5 F0.
My estimates were much worse tonight than last night, especially the secondaries.
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