Wild Ducks and Jupiter (11 Jun 2020)

 DSO, Jupiter, Open Cluster, Planet, Solar System, Wide FOV  No Responses »
Jun 132020
 

While waiting for Jupiter and Saturn to clear my tree line, I did some more testing with my wider FOV scope that has a simple DSLR mounted on it. I am still manually focusing the system but it doesn’t take too long to accomplish. The recently installed flattener corrects the distortion apparent in the stars at the corners of each image.

The target for tonight’s testing was Messier 11 (The Wild Duck Cluster). Legend has it the cluster was given its name by British Admiral William Henry Smyth (1788-1865). When describing the cluster, the Admiral, a very accomplished astronomer and avid hunter, commented the V-shaped group of stars looked like a flock of wild ducks.

Classified as an open star cluster, the flock is located in the constellation Scutum (The Shield). The constellation is right in the middle of the plane of the Milky Way and towards the center of the galaxy. That is fairly apparent by the sheer number of stars in the image. North is to the right putting M 11 right on the northern edge of the Scutum star cloud. The dark area towards the bottom right side of the image is not a lack of stars. It is a large area of dust and gas dense enough to block the light of more distant stars. Several of these areas were individually cataloged as dark nebulae by American astronomer E. E. Barnard, hence the B numbers on the matching chart.

Wild Duck Cluster (M 11) [M:11x120s]

As can be seen on the constellation chart, Scutum is in the southern sky located between Aquila and Sagittarius. The image and matching chart are rotated 90° to the constellation chart.

Chart generated by Cartes du Ciel

Chart courtesy of the IAU and Sky&Telescope

Once Jupiter and Saturn cleared the trees I switched over to planetary equipment and was able to get a couple of series of both planets before wispy clouds moved in from the south. As usual, the best Jupiter image was uploaded to NASA’s JunoCam web page for mission planning.

Jupiter [(V)TR:2506×0.74ms;TG:2501×1.1ms;TB:2505×1.7ms]

 Posted by at 15:32

Beehive cluster (M 44)

 DSO, General Commentary, Open Cluster, Wide FOV  No Responses »
Apr 072020
 

I have been testing a new optical configuration to give the PTO the ability to record larger FOV images. Mounting my Nikon D90 to a 80mm f/6 apochromatic telescope gives a 2.9°x 1.9° FOV image. The resulting 5.26 sq° image is 97% larger than the standard science image used for asteroid/comet analysis. The size of the camera chip is large enough though that significant distortion is visible at the extreme corners of the image. As you can see the stars are ‘stretched out’ with each pointing towards the center of the image. This is known as pincushion distortion. A field flattener will need to be added to correct this problem.

The test target is a fairly large open cluster. It lies in the center of the constellation Cancer and is known as the Beehive cluster. The current population count is about 1,000 stars although only the brightest form the naked eye object. This is one of the first objects observed by Galileo when he first turned a telescope to the sky. He counted 40 stars.

Beehive Cluster (M 44)
[M:4x60s]

The compressed display makes the image background much brighter than it should be. Click on the image for a larger more accurate view. This will also make the corner distortion easier to see.

 Posted by at 14:24

Wide Field Experimentation

 DSO, Wide FOV  No Responses »
Oct 232018
 

I am doing some wide field experimenting with my ancient and honored Nikon D50 DSLR. The images below were taken through a 18-55mm zoom lens, set at a focal length of 55mm. This generates a FOV of 25.7°x17.0° with each pixel representing 30.5″ of arc. The camera is mounted on a GEM (Losmandy G-11) to prevent long exposures smearing the stars.

I haven’t come up with a way to flat field these images yet which is why there are some dark splotches visible. These are known as dust donuts and are the result of dust or other material somewhere in the light path. Additionally, the camera was manually focused resulting in a soft look to the stars.

The first image is centered between the open star clusters Pleiades and Hyades. Most of the image is in the constellation Taurus. The bright star at the bottom right is the star Aldebaran. The ‘V’ shaped Hyades, the lower cluster, forms the head of the Bull with Aldebaran representing the eye. The orientation of this image is north to the left and east down and is slightly cropped to remove the tree line along the southern edge.

Taurus [M:17x60s] (mouse over for labels.)

The second image contains most of the constellation Orion. Visible in the ‘sword’ is the Orion nebula (M 42;NGC 1976) and just at the limit of visibility is a hint of the Flame nebula (NGC 2024) next to Alnitak. Curiously, M 42 is not identified in the annotated image. The orientation of this image is north up and east to the left.

Orion [M:30x60s] (mouse over for labels)

My next steps will be to try some different techniques to eliminate what appears to be some external reflections in the images and to add in the color. I like the scale of the image when the lens is set to 55mm and the optical distortion at the edge of the FOV is not as extreme as when the lens is set to a faster focal length. I think I will add this configuration to my list. I will also look for an affordable 50-55mm non-zoom lens.

 Posted by at 16:39

2018 Perseid Meteor Shower

 General Commentary, Jupiter, Mars, Meteor, Planet, Saturn, Solar System, Wide FOV  No Responses »
Aug 152018
 

The 2018 Perseid meteor shower was the perfect opportunity to test my equipment and procedures for full sky imaging. I had previously set up the camera in my backyard but the trees severely limit my FOV and the light from the base keeps the sky pretty bright. The Munson observing site the EAAA shares with the NWFAA would have neither of those limitations and the addition of the meteors would provide a more accurate evaluation of the camera sensitivity.

I started the run at 2046 (L). I’ve annotated a copy of the first still image to show the 3 classical planets that were visible along the southern horizon. Venus had already set below the western tree line. The lens I currently use for the all sky view is designed for a 1/2″ sensor camera. My camera has only a 1/4″ sensor which is apparent by the cut-off Big Dipper. A sizeable portion of the sky is not visible due to the lens/sensor mismatch. North is at the top of each picture.

The evening started with some high clouds but ended up fairly clear. Along with several meteors there were a lot of aircraft. My personal meteor count was 69 but that included several meteors that were not Perseids. Meteors not aligned with any known shower are called sporadic meteors.

This is an assembly of 2,251 10 second images taken on the evening of the 12th of August and morning of the 13th. The images are played at 0.1 seconds per frame. A quicker video (0.03 sec/frame) is on the Facebook page.

After several hours of Earth’s rotation, additional constellations and objects were visible. Of note is the constellation Perseus (the namesake of the meteor shower) and the Andromeda galaxy just visible as a smudge on the night sky. Although I have viewed the Andromeda galaxy naked eye before, Monday morning was the most prominent that I have ever seen due to Munson’s lower light pollution.

Lessons learned from this outing:

  • Extend exposure time to at least 20 seconds to increase the signal to noise ratio. That will also half the number of exposures I have to process.
  • Look for a 1/2″ sensor camera to avoid wasting FOV.
  • Look for a more sophisticated dark frame algorithm (note the peppered appearance of the clouds early in the video.
 Posted by at 11:33

Taking a break from asteroids

 General Commentary, Wide FOV  No Responses »
Apr 292018
 

Most of the images taken by the PTO are used to monitor asteroid and comet orbits. Collisions or gravitational interactions can, over time, change the orbits of small solar system objects. This could bring them closer to the inner solar system and potentially closer to Earth’s orbit.

By necessity the PTO will be taking a break from its primary tasking as well as any deep sky imagery. Recently, I have noticed an interfering pattern in some of the images. It has become worse over time. Troubleshooting has not identified the usual suspects (USB cable, USB hub, etc.). So, my primary camera is now on its way to the service center for diagnosis and hopefully repair.

Early interference was about 1 in 10 images.

Most recent interference is about 5 in 10 exposures.

So, for now, I will leave the telescope configured for planetary/lunar imaging. I also piggy-backed my Nikon along with a 105mm lens and will do some very wide FOV imaging. I have always planned on developing that capability; now looks like a good time. It will take learning a different software package and processing procedure. One of the first wide images is the constellation Lyra. The new software package can annotate each image and an example is below.

Lyra (The Lyre or Harp)

The FOV has increased from 37.85′ x 25.5′ to 12.⁰ 57′ x 8⁰ 35′.

 Posted by at 15:28