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More Sky Tests: Rokinon 8mm 180° Fisheye Lens;
Io Transit of Jupiter

Posted: 8 December 2012

Cloudy skies returned on Monday, 3 December. On Tuesday, I decided to do a "cloudy day project". For night all-sky photography with the D7000 DSLR with the new 8mm fisheye lens, I had originally planned to piggyback the camera on my ETX-90RA to provide tracking:


I've used the ETX-90RA in the past for night sky photography with a piggybacked Pentax Spotmatic SLR, Nikon D70 DSLR, and Nikon D7000 DSLR, so I knew this would work fine. But I remembered that I still had an old LXD55 tripod (sans telescope) from when I upgraded to the LXD75 tripod in May 2006 (that was subsequently stolen in December 2007 along with the 8" SC telescope and lots of other gear).

I unboxed the LXD55 tripod. I then began to wonder if I needed to use an AutoStar with it or whether an old ETX standard Electronic Controller I had would work. I connected the EC handcontroller and attached an external power supply. It worked! I could slew the mount at any of the four speeds available and the Right Ascension motor seemed to be running for tracking. I assumed it was tracking at sidereal rate but would have to wait until I could do a nighttime test to verify that.

I then began to investigate how I could mount the camera on the dovetail with what I had available. I was able to mount the camera using an old wood piggyback adapter I made back in the early 1960s (for use with my Edmund Scientific 3" Newtonian telescope tripod). It was not a perfect fit so I added some string as extra security against the camera mount coming loose. I was hoping I would not need the GEM head counterweight but the camera was enough weight to require it. The counterweight I have is too much but just the rod alone helped. This is how the setup looks:


It should work but would need to test it on a clear night. One slight bummer is that the ETX-90RA and its tripod is much lighter than the LXD55 GEM head and tripod. I can carry the ETX on its tripod with one hand; can't do that with the LXD55.

The sky finally cleared up again on Friday, 7 December 2012. The observatory was opened at 1805 MST, 63°F. I initially started the session by observing Jupiter, low in the east, 77X. Four moons were visible, but viewing was hampered by Jupiter's low elevation. I then began setting up the LXD55 mount for sky photography using the Rokinon 8mm 180° Fisheye Lens. I set up near the observatory:


I polar aligned the LXD55 using its polar alignment scope. I then began doing a series of test photographs. All were 10 minutes in length (using the Vello Shutterboss Wireless Remote) at f/3.5, f/5.6, and f/8, using ISO settings of 500, 1000, 1600, and 2500. After the first test image, I discovered that the mount was not tracking. In fact, the Right Ascension motor was not running (unlike during my initial tests discussed above) while using the old ETX EC handcontroller. I returned to the house and grabbed the AutoStar #497 from my ETX-125AT. Connected it to the LXD55 and went through some intial power-on steps. Did another exposure; still not tracking properly although the RA drive was running now. So I did what any respectable AutoStar user would do: I did a CALIBRATE MOTOR. Problem solved! All the next series of exposures properly tracked. This is one of the test exposures, f/8, 10 minutes, ISO 2500. North is on the left and east at the bottom.


Jupiter and the constellation of Taurus are at the bottom, with the Pleiades just above them. The Milky Way runs vertically through the image. During post-processing of the fisheye lens tests, I determined that using f/8 provided the best sharpness over the entire field-of-view (as expected). Using ISO settings of 1600 or slightly higher compensated for the loss of light from the higher f/ ratio, and should provide good meteor imaging during the upcoming Geminid Meteor Shower.

During the 10 minute exposures, I would return to the 8" LX200-ACF and do some observing. Jupiter was a prime target, viewed using the 2" Explore Scientific 9mm 100° eyepiece (222X). As Jupiter rose higher in the sky, the views got better and better. Also viewed NGC7606 (faint galaxy) and NGC488 (faint galaxy) using the 9mm eyepiece. Both were nice views using averted vision. M1, the Crab Nebula, showed some structure in the 9mm using averted vision.

I finished my fisheye sky photography tests at 2053 MST, and began setting up for iPhone imaging of Jupiter. The iPhone 4 was mounted on the 8" using the Magnilux MX-1 Afocal Adapter. I used a 1.25" 9mm eyepiece + moon filter + 2X Barlow Lens, yielding 444X. Video recordings were made using FiLMic Pro (which can lock focus and exposure) and were 90 seconds in length. During post-processing, the videos were stacked using Keith's Image Stacker. After I completed some imaging, I resumed observing Jupiter with a 5.5mm (364X) eyepiece and the 2" 9mm eyepiece.

Next, I viewed M42, the Great Nebula in Orion, using the 2" 9mm eyepiece. I then began trying to see the Horsehead Nebula using the 2" 9mm eyepiece. No luck. I slewed to the Flame Nebula; it was faintly visible in the 9mm eyepiece. I switched to the 1.25" 26mm (77X) eyepiece and tried again for the Horsehead Nebula. Still no luck. Added a Hydrogen Beta filter; still no luck. Without the filter I could see some nebulosity but could not identify the Horsehead. I have seen it before in the 8" so I know I can view it.

At 2208 MST, I returned to Jupiter, 222X, and began watching the start of the Io transit. I then did some iPhone imaging of the transit of Io and its shadow. At 2233 MST, I resumed Jupiter observing.

Here are some Jupiter images captured with the iPhone 4. They show Io before the transit (left image), and Io and its shadow during the transit.

photo photo photo

The videos were stacks of 2202 frames (90 seconds), 1470 frames (60 seconds), and 1467 frames (60 seconds), respectively.

I then captured one final fisheye lens sky photo, f/8, 10 minutes, ISO 2000. The image is cropped. South is at the bottom. Orion is at the lower left, Jupiter, Taurus, and the Pleiades below center, and even M31, the Great Andromeda Galaxy, near the right edge just below the Milky Way.


I completed sky imaging at 2300 MST, and continued observing the transit of Io, 222X. Io was very bright against the South Equatorial Belt and its shadow was very black and crisp.

At 2316 MST, I returned to Orion to try again for the Horsehead Nebula now that it was higher in the sky. Used 77X, but still no luck. I could see lots of nebulosity and some dark areas, but I could not spot the Horsehead. At 2330 MST, returned to M42 and viewed it at 77X. Always a grand sight. Switched to the 2" 9mm eyepiece (222X); lots of structure in M42 was visible. Using the 26mm eyepiece (77X), I then viewed M44 (open cluster), followed by a tour of open clusters in Gemini: NGC2158, M35, NGC2266, NGC2420, and then NGC2392 (Eskimo Nebula). Switched to the 2" 9mm 100° eyepiece and viewed the Eskimo Nebula. Wow! A lot of fine structure was visible. Love this new eyepiece!

Then viewed the galaxies M81 and M82 with the 2" 9mm eyepiece. M81 showed a very bright nucleus with little structure visible. But M82 was impressive at 222X, with lots of structure visible.

Closed the observatory at 0015 MST, 51°F, after a great six hour session.

I have added a "History" button to the Nav Bar at the top of the page. It has the history of "Cassiopeia Observatory". Check it out. As a result of this addition, the Welcome text has been removed from the home page and the "Welcome" button in the Nav Bar changed to "Reports".

One other change to the Site is that the "Weather" Photo Album has been renamed to "Sky & Weather"; I will occasionally add fisheye lens sky photos to the page.

Comments are welcome; use the Comments section below, or you can Email Me. Thanks.

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