astrophoto – Page 7 – A Darker View

Postcard from the Universe – Scutum & M11

M11 Region — The open cluster M11 and surrounding region, 24 x 5 min, Canon 60D and TV-76

C/2011 L4 PanSTARRS

A better image of comet C/2001 L4 PanSTARRS. The comet is moving slowly near the north celestial pole, still a nice object for observation through much of the night for any northern hemisphere observer.

Comet C/2011 L4 Pan-STARRS

Now for a truly awful comet image.

But it is all I managed to get this evening. A to-do list that is much to long and vehicle trouble caused me to reconsider plans to observe at the VIS. Thus I planned to observe the comet from the driveway. This works well in some respects, using the mounting points in the driveway I can have the ‘scope reasonably well polar aligned in the daytime. This would make finding the comet far easier, I could offset from the Sun and have the ‘scope aimed at the correct coordinates before it was dark.

It had been wonderfully clear all afternoon. It was just as the sky darkened that trouble appeared, a band of high clouds sweeping in from the west. Noooo!

The comet appeared in the STi guide camera right on schedule, my coordinates less than half a degree off! Not bad with a manual telescope mount offsetting from the Sun. The clouds swept over the comet a few minutes later, just as the tail was beginning to appear in the darkening sky.

I did grab a few images from the guide camera and snap a few frames with the DSLR. The monochrome CCD on the guider managed slightly better shots despite a fairly bright sky. I managed a few more frames as an opening appeared a few minutes after that. It is still an awful image. The only reason I could tell it was the comet is that it remained centered as the clouds swept through the image. Take my word for it, the barely there spot at the center of the photo is the comet.

At least my vehicle is fixed, a new alternator in place. Try again tomorrow?

Postcard from the Universe – Comet C/2012 K5 (LINEAR)

Another product of imaging earlier this week. Comet C/2012 K5 (LINEAR) is fading, but still bright enough to image. Right beside Orion it was well placed to target from my driveway. Just refreshing my comet hunting skills, getting ready for the show over the next few months as C/2011 L4 (PanSTARRS) comes into view.

Astrophotography with the EOS-M

In the few days I had the camera I was determined to acquire some astrophotography test shots with the EOS-M camera. Even if it meant getting up at 3am to have some dark sky after moonset. It would have been easier a few days before, but a Pacific storm system had provided several days of overcast with occasional rain. This particular morning was just about perfect, clear skies, decent seeing and no wind to bounce the telescope around.

Astrophoto Setup with the EOS-M — Astrophoto setup with AT6RC, SBIG STi autoguider and the EOS-M camera

For testing I used the same setup I often use with my Canon 20Da or 60D. An Astro-Tech 6″ (150mm) Ritchey–Chrétien telescope riding atop a Losmandy G11 mount. A 0.8x focal reducer has T-thread at the rear allowing a Canon EOS lens adapter. To attach the EOS-M I used the Canon M Mount to EOS Mount adapter. An SBIG STi autoguider completes the setup.

The result is an f/7 optical system with 1080mm focal length. This gives a field of view of about 72×48 arc-minutes (1.2 x 0.8 degrees) on the sky when using a camera with an APS-C sensor.

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Astrophoto Interference on Mauna Kea

Mauna Kea is simply a great place to shoot astrophotos from. Dark, clear skies with typically good seeing. Unlike some mainland locations there is a distinct lack of aircraft overhead. I am not sure how many shots I have had ruined by the bright anti-collision strobes crossing through the frame when shooting from locations in Arizona.

There are hazards to shooting photos here that do not commonly exist elsewhere. I was unpleasantly surprised when reviewing the take the next morning to find brilliant yellow lines through a hour and a half of exposures taken of the Cygnus region. The material is otherwise great, the makings of a nice shot, except for this one little issue. There are ways of suppressing artifacts like this when processing, but the beam is so bright I am not certain they will work all that well.

Worse, I checked the schedule, the offending laser is coming from Keck 2 AO, a system I work on.

The observatories have a system in place to deal with this issue. There are four operational lasers on the mountain, Keck 1 and Keck 2, Subaru and Gemini. Each optical observatory using a laser maintains a server that posts their laser location, status, and calculates the position of each beam in the sky. This can be queried by the other observatories to check if the beam crosses the field of view. A set of rules has been negotiated to determine who has right of way, usually who is on target first.

Obviously this computer system does not take into account my little telescope shooting photos from Hale Pohaku. If I had known I could have called Heather and asked her to shutter her laser, I was on target first. Being the kind soul she is, she would probably laugh with me.

Cygnus and Laser — Rough processing of a single frame, Cygnus region, with the Keck 2 Adaptive Optics laser crossing through the frame

Postcard from the Universe – Galactic Center

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.

Galactic Center — The galactic center region on the Sagittarius-Scorpius border

A Dark Night

Another new Moon weekend, another observing outing to Mauna Kea. With some shiny new astro equipment to play with I decided to load for photography instead of visual. Disassembling the photographic mount I realized it had not been taken apart in over two years, setup in the garage and used in the driveway. I did not expect to be alone, a few other local observers had indicated plans to get out this night.

Omega Centauri, NGC5139, sum of 31 x 1min exposures, AT6RC and Canon 60D

Worry on the drive up, the cloud deck seemed quite high. I was concerned that the Mauna Kea VIS, at 9,200ft, may be in the clouds. With wipers and headlights on, through the heavy fog I drove, not encouraging when you expect to use a telescope. The worry persisted until the last switchback, ascending through the last wisps of cloud just a few hundred feet below the VIS to behold a cloudless blue sky overhead.

As expected the Mauna Kea Visitor Information Station was a zoo. A dozen summit tour buses added to a heavy Saturday night crowd. The parking lot was full with even more cars parked along the road. Not a real problem, the tour buses use reserved spaces right in front of the building. They pull out about an hour before sunset, headed for the summit with their customers. We swoop in on the vacated parking spaces and set up our gear.

Astrophotography — A trio of telescopes set up for astrophtography at the Mauna Kea VIS

The crowd is an interesting experience. Well over a hundred folks waiting for dark and the evening program. There are the usual issues of headlights and camera flashes. It may not be all that dark for a while, but we gain a nice paved place to setup, and there is electrical power available. The crowd will slowly wane as the night progresses, mostly gone by 9pm, driven off by the cold. At 10pm the VIS closes and the remaining lights are turned off.

In addition to the VIS telescopes, there were quite a few local amateurs taking advantage of a moonless Saturday night. Cliff and Tony brought Cliff’s 24″ Dob, a two person job to move that ‘scope. Wayne brought photography gear. Mike was likewise set up for photography, planets instead of deep sky, using a Flea 3 and an ancient 10″ Celestron. Olivier brought his 19″ Pricilla, providing plenty of glass for visual astronomy while the cameras exposed for hours.

It was Malalo o Ka Po Lani, cultural night at the VIS, with a special lecture. This meant a large crowd, most of whom stayed to enjoy the perfect skies the mountain provided this night. They wandered around the telescopes asking lots of questions. While the photographic ‘scopes did not offer views through the eyepiece, there was still a lot of interest in the process. I chatted with many folks as I worked, fiddling with the complex equipment necessary to take photos of the sky.

It was quite the gathering of Losmandy G-11’s! Wayne brought two, Mike brought one to carry the old 10″ Celestron, I had mine setup for photography with the AT6RC. Add the three that the Mauna Kea VIS uses! A testament to these well-built mounts, some of which are two decades old.

The astrophoto gear was working nicely. There were a few issues to deal with at the beginning of the night, the usual new gear stuff. A few things I need to fix before next time… need to remount the guider so I can co-align it with the imaging ‘scope. I need to mount a real finder, and make it easier to hunt down the targets. But overall I was pleased, the new setup worked as I hoped it would.

SBIG ST-i Autoguider — The SBIG ST-i autoguider mounted to the top of the AT6RC telescope

I will write more about the SBIG ST-i later. The short version… Much easier to use than the ST-4, accurate, painless acquisition of guide stars, it just locked on and stayed there. The only real drawback is the inability to dispense with a computer. I recently re-built one of my older laptops for use as the astrophoto machine. But since the computer is going to be there, I may as well use it, time to integrate the DSLR with the computer and shoot tethered. I have the software, just that I had tried to keep it simple in the field.

Another pleasant surprise was the ease of focusing with the AT6RC with a Bahtinov mask. I have been wondering about the stock focuser on the new ‘scope, how well does it handle the heavy DSLR camera. One lesson is that it locks the focus quite well, I noticed no drift each time I checked focus. Indeed, at one point I pulled out the 60D, swapped the focal reducer and adapter onto the 20Da and checked focus again, it was still perfect.

While my camera took exposure after exposure, I took in the views that big glass can produce. Bouncing back and forth between Cliff 24″ and Olivier’s 19″. No surprise for a spring session, galaxies were in rich supply. We viewed a lot of the showpiece objects, from Ursa Major to Virgo and Corvus.

This night was the type of night we hope for when planning an observing outing… Not too cold, no strong wind, and no clouds. Just a dark sky to delight the imagination all night long.

Postcard from the Universe – Rising Milky Way

MIlky Way over A'a — The rising Milky Way silhouetting and old a'a lava flow on Mauna Kea, Canon 60D @ ISO12800, 17mm f/4, eight 10 second frames aligned and averaged

Canon Introduces the 60Da

Most of my astrophotos are taken with my venerable Canon 20Da, a special version of the EOS 20D that was produced for astrophotography. Normal DSLR cameras work quite well for astrophotography, with one major drawback… The filter placed in front of the sensor blocks much of the Hα light emitted by many nebulae.

NGC1976 or M42, the Great Orion Nebula, taken with the Canon 20Da and a AT6RC telescope.

This light, emitted at 656mn, a wavelength deep in the red, give emission nebulae their characteristic shades of rich red. Hα is the strongest component of light produced by emission nebulae. Without this light, the nebulae will often appear bluish in photographs, as the next strongest component OIII dominates.

Specifically for astrophotography, Canon produced a special version of the 20D with a re-designed filter that allowed Hα light to reach the sensor, the Canon 20Da. The camera also featured on-screen focusing, a feature now found on most DLSR cameras, but unusual back in 2005.

The 20Da was discontinued in 2006. Astrophotographers wanting a DSLR camera with a filter that admits Hα light must buy a standard camera and remove the filter, or have it modified by specialist that offers a conversion service.

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