Cassiopeia Observatory

D7000 DSLR Horsehead Nebula
Posted: 28 November 2011

The wind that caused me to end the previous night's session early continued to blow during the day on Sunday, 27 November, with gusts to 26 MPH. But they calmed down after sunset. I opened the observatory at 2135 MST, 51°F, with just an occasional light breeze. At 2145 MST, viewed Jupiter with the 8" LX200-ACF and a 26mm (77X) eyepiece. Three moons were visible. Switched to a 9.7mm (206X) eyepiece; nice details were visible in the cloud bands. The seeing was much better this night than on the two previous nights. I added the moon filter to the 9.7mm eyepiece to reduce the glare from the planet; good view.

I then did some D7000 DSLR prime focus + 3X TeleXtender imaging of Jupiter. I did HD video recordings of 1 and 2 minutes, at shutter speeds of 1/200sec, 1/160sec, and 1/125sec, at ISO 3200. The 1/160sec exposure was best and I stacked the two minute video (2333 frames) in Keith's Image Stacker. This is the (cropped) result:

I ended Jupiter imaging at 2210 MST; four moons were now visible. I began preparing for imaging my primary target for the night: the Horsehead Nebula in the constellation of Orion. Beginning at 2219 MST, I began observing with the 26mm eyepiece, with and without a Hydrogen-Beta filter. Initially, I could see some of the surrounding nebulosity but not the Horsehead itself. Finally, after 17 minutes of looking, I picked up the Horsehead visually using averted vision and no filter. With the Hydrogen-Beta filter attached, seeing the Horsehead was more difficult due to the darker view, but it was detectable with averted vision.

I then began setting up for D7000 DSLR prime focus + Off-Axis Guider (OAG) imaging of the Horsehead Nebula. Did a focus test using the Bahtinov Mask on the star Rigel. With the camera attached to the telescope and the telescope slewed to the Horsehead Nebula, I immediately saw an excellent guide star in the OAG reticle eyepiece. I did a 1 minute, ISO 3200, framing test exposure. I could not see the Horsehead in the resulting image on the D7000 screen but I could see the nearby nebula NGC2023, so I decided to go with it. I did 10 guided images of 2 minutes each at ISO 3200. During post-processing, these were stacked using Lynkeos, for an effective exposure of 20 minutes, with this result:

I then did guided 5 minute ISO 3200 and guided 10 minute ISO 3200 exposures. This is the 10 minute exposure:

I ended imaging at 2350 MST. At 0000 MST, I began a tour of DSOs in the constellation of Orion using the 26mm eyepiece: M42 (Great Nebula in Orion), NGC1977 (diffuse nebula), M43 (diffuse nebula), NGC1990 (diffuse nebula), NGC2024 (diffuse nebula), IC434 (Horsehead Nebula), M78 (diffuse nebula), and NGC2194 (open cluster). I then returned to M42 for further study using the 26mm (77X), 15mm (133X), 9.7mm (206X), and 5.5mm (364X) eyepieces.

At 0030 MST, I went back to Jupiter for a quick look at 77X and 206X; the Great Red Spot had now rotated into view. At 0033 MST, I started a tour of DSOs in the constellation of Canis Major: M41 (open cluster), NGC2354 (open cluster), NGC2360 (open cluster), and NGC2362 (open cluster). Next, I viewed M79 (globular cluster) in the constellation of Lepus.

At 0050 MST, Mars had just risen above the hill to the east. I took a look at 77X but it was just an orange distorted blob due to its low altitude. At 0101 MST, I returned to Jupiter and viewed it at 364X, 206X, 133X, and 77X. Seeing was not as good as it had been earlier. I began closing up for the night. As I was putting things away, I discovered that I had forgotten to set the D7000 ISO to 6400, which is what I had planned for the Horsehead Nebula imaging. I thought I might have to re-do the imaging, but based on the results I obtained at ISO 3200, I don't think I will need to retake the images. At 0121 MST, I took a final look at M42, and then Mars, now a little higher in the sky. Mars was still a distorted blob.