When you want to see the stars, find someplace dark
Peering into the dark with a camera
Known as M6, NGC6405, or The Butterfly Cluster, this pretty open cluster lies just above the tail of Scorpius. Visible to the unaided eye under a dark sky, it is an easy photographic target.
I have been working on improving the color balance in my astrophotos. Color is an interesting and complex subject in photography, worse in astrophotography. I think the results are much better here that in my previous work. Hope to take a few more photos this week and will continue to experiment.
The last time out I fitted a camera ball mount to the counterweight shaft of the Losmandy mount. This allowed me to shoot an additional camera at the same time, along with the camera attached to the telescope. The second camera can be aimed at a different target completely. With a relatively wide angle lens, tracking errors become insignificant.
With the center of the Milky Way high overhead it made an obvious first target to test this wide-field setup. The results are quite nice, a series of one minute exposures reveal the star clouds in fine detail. The camera for this run was the Canon 60D, as the 20Da was shooting the Lagoon at the time. I need to swap places and try the shot again with the 20Da to see what the Hα sensitivity reveals, capturing more of the nebulae that is mingled with the stars.
The lens was an older Nikon 50mm f/1.8 stopped down to f/2.8, nice round star images right into the corners of the frame. Yes, a Nikon lens mounted to a Canon camera, you can do that. A very nice lens, I will be using it again for this work.
Another product of this last new Moon star party at the MKVIS. An easy target, suited to checking the performance of the new setup. As usual, click on the image to view the larger size…
Transit is over, an exhausting and exhilarating day! I am headed to bed, but still totally jazzed with the experience. Keeping the webcast going for seven hours was a huge effort. Given the comments from our viewers it was worth it. I will have to more fully write up the experience for a later post.
The best visual for the day was the few minutes just before second contact… A beautiful, razor thin arc of light coming through the Venusian atmosphere, connecting the two horns of the occluded Sun. It was delicate and sublime, one of the most memorable sights I have ever seen through a telescope. With the excellent seeing of Mauna Kea, and the wonderful optics of my TV-76 telescope, the sight was clear and steady. I have yet to find a photograph that captures what I saw through the eyepiece.
I will post a quickly processed version of one of the frames from the second camera…
It was a full dress rehearsal. Both telescopes, two cameras, the entire streaming rig set up on the lanai. No less than three computers with cables all over the driveway! Surprisingly enough, everything went pretty well!
Everyone wandering by the house noted the telescopes. I gave peeks to our mail-lady and a couple young women who stopped by, intending to read me a bible verse or two (that was fun;)
Two technical issues were key today… Using thirty feet of active USB extension cables to run the streaming camera remotely, no problem. Co-aligning the two telescopes to aim at the same point, no action needed, aligned from the start. I had thought I might need to shim the mount for the piggyback ‘scope. I was also able to play with the streaming camera further. The Baader film filter gives a blue-white image. Adjustment of the camera white balance will restore a little yellow cast. I do not have much problem with the white, but a hint of yellow will allow people to instantly realize they are seeing the Sun. The same reason I adjust my processed photos for a golden orange hue.
We are all swapping gear around to get the set-up ready. Chris was nice enough to loan me a Canon T-ring and some Baader film. I built a battery pack and some sun-finders for several telescopes. Last night I picked up a whole solar rig from Cliff for delivery to Olivier. Olivier lent a 40mm eyepiece to Keck for the public telescope that will be setup at HQ. The list goes on…
I was not the only one doing a dress rehearsal. So far today I have been on the phone to other folks setting up and using a sunny Saturday to check gear. Some of the guys over on Maui even posted a video of their test run. I should have thought to do the same thing! Will have to time lapse the summit setup.
The rearrangement of my astrophoto setup proceeds. If somewhat frantically in the face of the upcoming Transit of Venus. Another device has joined the toolkit, a bit of hand-wired electronica that gets the job done.
I did not design the device this time. This would have been completely within my capability, but why do so when someone else has already done the job? This is typical within the astronomy hobby, where many designs are shared for the benefit of everyone. In this case it is the USB to ST4 adapter designed by Gene Nolan.
All I had to do was follow the schematic and download the code into the microcontroller, the device worked first time. Gene does sell kits, but I wanted to do this quickly and had everything I needed on hand except the microcontroller and opto-isolators.
The only real problem that cropped up during construction was the wrong part received for the opto-isolators. The DigiKey description read DIP-8, so I ordered it, expecting to get something that fit into the DIP socket I had already wired onto the board. When the parts arrived I found that they were indeed DIP… lead-formed DIP packages meant to be surface mounted, with chopped off leads. I ended up soldering the devices to another DIP socket, using it as a header, which then plugged into the socket on the board. It looks funny, but it works.
It did take a couple hours of downloading and installing the drivers and other useful software packages to get everything working. This includes the very useful ASCOM driver framework, and PHD Guide. Both of which I plan to use beyond the upcoming Transit of Venus to do more astrophotography.
My wife may have been a little perturbed by the testing setup strung across the kitchen table, a laptop and the heavy Losmandy head, a Canon 60D camera, all connected by a snake pit of cables. But it worked, first time, that is always nice.
As we approach the Transit of Venus I decided to attempt to photograph Venus as a very thin crescent. I do not normally pay much attention to the planet, it is pretty when seen in the sunset. But when you turn a telescope to Venus it is quite boring, a white ball with no detail to be seen. I find I have been paying a bit more attention with the transit looming close on the calendar.
I could photograph the planet after sunset, but as Venus is quite near the Sun it would be very low in the sky and I would be shooting through a lot of air to get the imagery. Atmospheric distortion would be a major problem. The other method is to try something I had not done before, photograph the planet in the daytime, high in the sky and quite near the Sun.
Yeah, This will be a tricky operation. Venus will be only 12°44′ from the Sun, meaning I will have to be quite careful to avoid roasting my equipment, or my eyes.
I chose to use the 90mm APO refractor. With the optics at the front there will be some sunlight splashed down the interior of the tube. It should not be a focused image as it will hit the tube not even halfway down. There the heavy aluminum tube walls should dissipate the heat efficiently. The fully baffled tube should also stop much of this light before it reaches the camera. I may not have designed and built the optical tube with this sort of abuse in mind, but I did build it heavy, it will take it.
The results? The final image can bee seen to the left. Not horrible, but it could have been better. The seeing at 11am was already starting to degrade, I am always amazed at how well the software can extract a half decent image from such distorted original material. The magic of sorting through and averaging a thousand frames. I wonder what I could do with better seeing.
Another try? Probably not, Venus is quickly getting closer to the Sun as we approach transit in nine days. The next time I photograph Venus it will most likely be silhouetted against the solar disk. Maybe an attempt after transit? I could shoot earlier in the morning with possibly better seeing.
A Memorial Day Sun from Hawai’i. Another run at setting up and testing gear for the upcoming Transit of Venus. The seeing was not great, but I shot the Sun and some material of a thin crescent Venus just 12°44′ from the Sun.
