Image Processing Overview: Data Reduction

This post describes how one creates an astro-image like the one below. This will be a bit of a dry post. Let’s start start with the finished product, an image I took of Messier 81 in the constellation of Ursa Major, also known as Bode’s Galaxy.

Messier 81

I use the term “image” intentionally to contrast with “photo.” These images are the result of capturing data on a CCD through a telescope in multiple long exposures. They are not photos. These data need to be processed to become the pretty images we see. The image of M81 above used 3 hours 25 minutes of exposure time, taken in multiple 5-minute exposures with white light, red, green, and blue taken separately and processed as described below to create the final image.

The data are noisy. There are anomalies in the optical system like dust or uneven illumination though the telescope. Heat causes random charges to accumulate on a CCD during long exposures, even with the CCD chilled to -25°C. The CCD chip itself may have minor defects that generate differences in how photons are collected. The electronics introduce noise when data are read off the CCD and passed to the computer controlling the camera. Finally, the objects being imaged are very dim, so the signal we are trying to capture is small, just barely above the background glow of the sky.

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ASCOM Platform Installation Error on Windows 10

I am in the process of installing a new computer in my observatory. It is never fun going through the mass of software installations, etc. that accompany replacing what was a smoothly operating system. I’m replacing the old PC, which I built from parts from an even older PC I used at home, because the BIOS stopped saving its settings. It is probably the battery on the motherboard, but after 7 or so years it is time for an upgrade.

I bought a new HP Envy Windows 10 64-bit machine at Costco. All the installations (The Sky, Maxim DL, PinPoint, ASCOM, etc.) seemed to go fine at home. But I ran into problems with ASCOM when I was setting up the PC in the observatory and checking connectivity. When I tried to connect to the mount from Maxim DL, ASCOM brought up an error window and then did not have an mounts to select. The Astro-Physics setup program worked fine and connected to the mount. I ran the ASCOM diagnostics program, which reported that it had “Completed function testing run: 1559 matches, 2 fail(s), 5 exception(s).” It was not at all clear what the issues were.

So I ran the installer and repaired the installation. That did not change anything, I was still getting the same errors. The ASCOM Profile Explorer also brought up error messages and then didn’t work. I then ran the Profile Explorer as an administrator. And it worked. Running Maxim as an administrator also worked. Running as administrator, however, is not a good long-term solution.

So I went to the ASCOM Yahoo! Group (it is linked from the ASCOM Support page) and searched there. Success! I found a thread with my exact problem and, after figuring out Yahoo! Groups navigation, found a solution. Apparently the installer did not set permissions properly on a certain registry key. Here is what to do, taken from the wonderful people on that Yahoo! thread. But be careful, editing the registry can kill your computer.

  1. Run Regedit (hit the Window key, type “run”, hit enter, enter “regedit”, hit enter, agree to changes)
  2. Back up the registry (File > Export, select a place to save and a name)
  3. Open HKEY_LOCAL_MACHINE then SOFTWARE\WOW6432Node (Note these instructions are for 64-bit Windows)
  4. Right click on ASCOM and select “Permissions” You may be prompted to allow Regedit to reorder the permissions, that is OK
  5. Scroll to the bottom of the list of groups and select “Users”
  6. Make sure the box next to “Full Control” is checked and click OK
  7. Close Regedit and you should be good to go

In looking back, there are a couple of places where I could have found the error in the diagnostic and installation logs.

At the bottom of the installation logs, there is a section that starts with “Error List.” Two lines below it is this message, which points directly to the error:

Error RegistrySecurity - Subkey SOFTWARE\Wow6432Node\ASCOM does not have full access rights for BUILTIN\Users!

There is also this section in the diagnostic log that points out the problem:

12:01:08.912 ScanEventLog 12/29/2016 11:43:45 AM ASCOM Platform Error 24 FinaliseInstall - Exception HKCR\ does not have CreatorOwnerGenericAccess!
12:01:08.912 ScanEventLog 12/29/2016 11:43:45 AM ASCOM Platform Error 24 FinaliseInstall - Exception HKCR\ does not have SystemGenericAccess!
12:01:08.912 ScanEventLog 12/29/2016 11:43:45 AM ASCOM Platform Error 24 FinaliseInstall - Exception HKCR\ does not have SystemSpecificAccess!
12:01:08.912 ScanEventLog 12/29/2016 11:43:45 AM ASCOM Platform Error 24 FinaliseInstall - Exception HKCR\ does not have AdministratorGenericAccess!
12:01:08.912 ScanEventLog 12/29/2016 11:43:45 AM ASCOM Platform Error 24 FinaliseInstall - Exception HKCR\ does not have AdministratorSpecificAccess!
12:01:08.912 ScanEventLog 12/29/2016 11:43:45 AM ASCOM Platform Error 24 FinaliseInstall - Exception HKCR\ does not have UserGenericAccess!
12:01:08.912 ScanEventLog 12/29/2016 11:43:45 AM ASCOM Platform Error 24 FinaliseInstall - Exception HKCR\ does not have UserSpecificAccess!

The Finalize Install log has these entries, which also point to the problem.

11:43:45.810 CheckHKCRPermissions HKCR\ does not have CreatorOwnerGenericAccess!
11:43:45.811 CheckHKCRPermissions HKCR\ does not have SystemGenericAccess!
11:43:45.812 CheckHKCRPermissions HKCR\ does not have SystemSpecificAccess!
11:43:45.812 CheckHKCRPermissions HKCR\ does not have AdministratorGenericAccess!
11:43:45.813 CheckHKCRPermissions HKCR\ does not have AdministratorSpecificAccess!
11:43:45.814 CheckHKCRPermissions HKCR\ does not have UserGenericAccess!
11:43:45.814 CheckHKCRPermissions HKCR\ does not have UserSpecificAccess!

My sincere thanks to the ASCOM Yahoo! Group contributors. I have memorialized their advice here so that it might be helpful to someone else.

Andromeda Galaxy, Orion, the Pleiades, and the Double Cluster

Over the Thanksgiving weekend, I was able to get the iOptron Sky Tracker Pro out again and try some more wide field astrophotography. I learned (and should have known) that level is as important as polar alignment for good tracking. Having done most of my imaging with autoguiding which corrects for leveling and other mechanical errors, I did not level properly back in October and had a number of disappointing images. This night, however, turned out better.

I used my Sony RX-100 M4 camera to take the images, controlling the camera over WiFi using Sony’s PlayMemories Mobile software. This software allows complete control of the camera’s function from any iOS or Android device and is available from the respective app stores. [Please note that I am currently an employee of Sony Pictures Entertainment, and Sony is the parent company of my employer.] This night, I used my iPad. I selected three targets: The Pleiades and the Double Cluster in Perseus, M31 — the galaxy in Andromeda, and the constellation Orion.

For each image, I used 15 second framing exposures. Focus was set to manual and at infinity. Once framed, I took longer images, settling on three minutes for my target exposure time. The camera performs a long-exposure noise reduction that lasts as long as the exposure. So a three minute exposure is six minutes of imaging time. I tried turning that off in my failed October attempt, but the remnant noise was not easily removed (I admit I have not experimented extensively with this, but I did get good results with camera long-exposure noise reduction turned on).

I captured all the images in Sony raw (.arw) format and imported them into Adobe Lightroom. I exported them in TIFF format and then processed them in PixInsight. In PixInsight, I performed background neutralization, color correction and balance, and some contrast adjustment. I imported the result back into Lightroom, did light touch-up and noise reduction to produce the final results.

The first image I took was of the Pleiades and the Double Cluster in Perseus. Two beautiful objects in a small telescope or with binoculars. This was a simple, three minute exposure. The Pleiades are on the right in the middle of the image, the Double Cluster is in the upper left, and the bright star in the lower left is Capella.

Please click on any of the images to be taken to the gallery and see a higher resolution image.

The Pleiades and the Double Cluster

For my image of the Andromeda Galaxy, I did a bit more processing. I took one two minute exposure and a one minute exposure, combining them in PixInsight. I would have taken a three minute single exposure but it was cold and I wanted to get on to Orion. This image had the most processing in PixInsight. The galaxy is the fuzzy spot in the middle of the image.

The Galaxy in Andromeda

The final image I took was of Orion, which was fairly low in the sky, not more than 40° above the horizon. I also zoomed the camera which reduced the f-ratio by one stop, from 1.4 to 2.4. Because of this, I took a four minute exposure. My only comment on the processing is that I think I may have clipped the blacks too much. I’ll try again when it is higher in the sky.

You can see the Nebula in Orion in the center right. Note that the two brightest stars are Betelgeuse and Rigel. Rigel is on the left, for you should always remember that Rigel is not red. If you zoom in to the lowest star in Orion’s belt (Alnitak) you can see a little red which is the Flame Nebula. I have an image of it in the gallery.

The Constellation Orion

Comments are welcome and I hope you enjoy the images.

Udayagiri Jain Caves, Bhubaneswar

Back in October 2015, I had the opportunity to visit Bhubaneswar, India for business. After our work day, we had the opportunity to visit the Udayagiri Jain Caves. Located on the northwest side of town, these caves were carved into the sandstone hill starting in the first century B.C. as dwelling retreats for devotees of the Jain religion.

Jains practice extreme asceticism so the dwellings are sparse on the interior. Not so the exterior which has many detailed carvings and reliefs. Rani Gumpha or the Queen’s Cave is perhaps the most impressive.

Rani Gumpha or Queen's Cave, cave #1 at Udayagiri caves

Rani Gumpha or Queen’s Cave, cave #1 at Udayagiri caves

There is a delightful carving of a tiger known as Bagh Gumpha. Yes, the “Tiger Cave.”

Bagh Gumpha or Tiger cave

Bagh Gumpha or Tiger cave

Udayagiri is part of a larger complex of caves and temples that includes caves and temples on Khandagiri hill. This is a view looking across to Khandagiri temple.

The Sun setting behind Khandagiri temple

The Sun setting behind Khandagiri temple

Small Elephant Cave has beautiful carved elephants.

Chota Hathi Gumpha or Small Elephant Cave

Chota Hathi Gumpha or Small Elephant Cave

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Wide Field Astrophotos

Since I haven’t taken the time to get the observatory up and running for quite a while, I have instead done some night photography with my Sony RX100. To that end, I acquired an iOptron Sky Tracker Pro tracking camera mount. It is a great device, complete with polar alignment scope and internal battery.

I took two nice Milky Way shots on my first night imaging on September 4th. The first shot is looking directly overhead. The bright star toward the top of the image is Vega, Deneb is near the mid point on the left, and Altair on the right. This is one three-minute exposure processed in Adobe Lightroom. (Lightroom is an absolutely amazing product.)

The Milky Way

The second shot is in the south, with the galactic center in the middle of the frame. The three bright stars on the mid-right of the image are actually two planets and a star. Saturn is on the top, Mars on the left, and Antares under Saturn. This is also one three-minute exposure processed in Lightroom, with some obstruction removal in Photoshop.

The Central Milky Way

Click on the images to be taken to the detail page in my photo gallery.

Talakadu — October 2015

Last year my hosts in Bangalore took me on a great trip south to Talakadu (or Talakad). Talakadu is a small town about 87 miles (140 kilometers) south of Bangalore and about 30 miles (50 kilometers) east of Mysore. From Bangalore, you take the Kanakapura road south, go well beyond Kanakapura and well into the countryside. It is a pleasant drive.

Talakadu is famous for its temples, and for the temples being buried in the sand. In a conflict in the early 17th century, a curse was put on Talakadu that led to it being covered in sand. Wikipedia covers it well as does this story from the Deccan Herald.

Several of the temples have been excavated from the sand. These are actively used for worship and are being maintained and restored. This is the Sri Vaidhyanatheshwara Temple.

A wide view of Sri Vaidhyanatheshwara Temple

A wide view of Sri Vaidhyanatheshwara Temple

Here is another view. The lighter colored carving is new work replacing stone that had worn away in the intervening years. I have been unable to find the date when these temples were originally built.

The lighter stone is new construction replacing worn away stone

The lighter stone is new construction replacing worn away stone

The interior at the back is beautifully carved and decorated.

The interior is quite pretty

The interior is quite pretty

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Pterosaurs at LA County Natural History Museum

We recently visited the Los Angeles County Natural History Museum to see the Pterosaurs exhibit. This is an excellent exhibit and I highly recommend seeing it. It runs through October 2nd 2016.

Here is the original entrance to the museum. Now you enter off of either Exposition Boulevard or opposite the Coliseum.

The original entrance to the LA County Natural History Museum

The original entrance to the LA County Natural History Museum

Pterosaurs are prehistoric flying animals. Closely related to dinosaurs, they are only one of three groups of animals to have achieved powered flight, the others being bats and birds. They ranged in size from a wingspan of 18 inches to the massive quetzalcoatlus which had a 33 foot / 10 meter wingspan. I’m not sure of the name of this one, though; it greets you at the entrance to the exhibit.

This pterosaur greets you at the entrance to the exhibit.

This pterosaur greets you at the entrance to the exhibit.

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Julian Gold Mine

Back on the July 4th weekend, we traveled south from Lake Riverside to visit the historic town of Julian. It is about a 50 mile, one-hour drive through beautiful countryside from Aguanga, through Oak Grove, through Warner Springs to Julian. We have visited many times but not for the last couple of years. But on all of these visits, we have not gone to the Eagle & High Peak Mine tour.

Yes, you do walk into the hillside.

The entrance into the Eagle Mine and the starting point for the tour.

The entrance into the Eagle Mine and the starting point for the tour.

The whole reason for going is the tour, of course. This tour has a good guide. He not only looks the part, he is very knowledgeable and presents the content well.

Our rour guide was knowledgeable and presented the material well.

Our tour guide was knowledgeable and presented the material well.

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Cedar Springs Trail

On Memorial Day weekend, we took a hike up Cedar Springs Trail in the San Jacinto National Forest. The trail starts about three miles up Morris Ranch Road in Garner Valley. The trail is shown on Google maps as Pathfinder Road. You turn north on Morris Ranch Road from CA Highway 74 (the “Palms to Pines Highway”) at the fire station in the village a few miles west of the junction with CA Highway 371.

The trail head is clearly marked.

Cedar Springs Trail is at the end of Morris Range Road on the north side of Garner Valley

Cedar Springs Trail is at the end of Morris Ranch Road on the north side of Garner Valley

The San Bernardino National Forest hiking guide describes the trail as follows:

Cedar Springs Trail (4E17) This moderate trail begins on Morris Ranch Road 4 miles north of Hwy 74. The trail travels through private property; please respect private property rights and stay on the dirt road. This 3.2 mile hike begins at 5760 ft. The trail connects with the Pacific Crest Trail along the Desert Divide south of Palm View Peak at an elevation of 6400 ft. To reach Cedar Spring cross the PCT and continue northeast for one mile.

We only went up the first mile, turning around just where the relatively flat road ends and the switchbacks begin. It was a very pleasant day, with the plants in spring green and blooming. The trail starts wide and flat. Clearly this has been used as a road.

There were many wildflowers on the trail

Ther were many wildflowers on the trail

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Lovric’s Sea Craft, Anacortes Washington

When we were on Spring vacation in Anacortes, Washington, we had a chance to walk through Lovrić’s Sea Craft, a large boatyard on Oakes Avenue. Follow the link to the website for the facility, it has some great before and after pictures of their work on boats of all kinds.

Lovrić's Sea Craft -- A large boatyard in Anacortes, Washington

Lovric’s Sea Craft — A large boatyard in Anacortes, Washington

Lovrić (the correct name, according to the website, is without the “‘s” but with the acute accent on the “c”) is on the north west side of Fidalgo Island, along Guemes Channel. This is a view from the boat yard toward the island.

Looking south toward Anacortes.  Cranberry Lake is over the hill to the right.

Looking south toward Anacortes. Cranberry Lake is over the hill to the right.

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