International Space Station in H-Alpha

Ever since I made the images and video of the ISS solar transit at Huntsville State Park, I have wanted to do the same thing using an H-Alpha solar telescope. The right combination of location, weather, and available time came together on May 6, 2018, so I borrowed a Coronado PST and headed to Davy Crockett Memorial Park in Crockett, Texas.

The transit occurred at 11:27:44 AM, and lasted about six tenths of a second. Considering it took nearly an hour to drive to the site and then almost a half hour to set up, this seemed like a small reward for the effort. But, it was very satisfying to see the space station race across the face of the Sun literally seconds after I had finished setting up and focusing the scope.

Composite of 11 separate images, combined and colorized in Photoshop CS6.

A 300% zoom of one of the better images in the series, showing some of the structural details.

Telescope: Coronado PST
Mount: Vixen Super Polaris
Camera: Mallincam SkyRaider AG
Processing: MALLINCAMSKY, PIPP, Photoshop CS6

First Light - AT72EDII

Wow! This little scope is a major step up from the ST80.

There is a lot that I want to cover in this post, so bear with me, please. If you're just here for the pictures, then skip down a bit.

The AT72EDII is an air-spaced doublet refractor with an FPL-53 element. The lenses are made by Ohara. The FPL-53 lens makes a huge difference in correcting chromatic aberration, rendering sharper images with much more realistic colors--closer in hue to those that I have gotten from the Epsilon-200. In comparison, I thought the colors I was getting from the ST80 were somewhat "cartoonish," even with the Baader Contrast Booster.

Here is the rig as it was on the night of first light. Using a little of my redneck engineering skills, I cobbled together a viewfinder mount out of plywood and plastic.

A new telescope calls for a new focusing mask, right?  Using the astrojargon Bahtinov Focusing Mask Generator, I printed the mask on card stock, then mounted it to a cap made of more card stock, peel-and-stick foam, and duct tape. It fits over the end of the dew shield.

Yes, I used duct tape.

So, after getting everything put together, the mount aligned, and the focusing mask in place, I pointed the scope at Deneb to set the focus. There wasn't a lot of interest to see during the focusing process, but when I took a 30 second exposure with the mask still on, I got this:

Diffraction spikes on Deneb. Aside from being reduced in size, this is an unprocessed image.

Note the lack of spurious color as compared to these images from the ST80:

I knew that I was in for a treat! So, I took off the mask and made a single, 30-second exposure of Deneb:

Unprocessed, resized image.

Yes, there is a bit of a halo around Deneb, at center, but it is far less prominent (and less purple) than similar images that I've taken with the ST80.

I wanted to image the Double Cluster in Perseus, first, but it wasn't in a good position for the mount when I started. So, I decided to grab a few images of Messier 45, the Pleiades, until the Double Cluster was a little higher in the sky.

Messier 45, the Pleiades
Click here for full size

Exposure: 10x180@ISO1600
Telescope: AT72EDII
FF/Reducer:  ATR8 (f/4.8)
Mount: Vixen Super Polaris
Camera: Canon EOS Rebel T3
Processing: Deep Sky Stacker, Photoshop CS6

This is a close-up (full-size) of a portion of the nebula:

Click here for full size

I admit that, at a quick glance, there isn't a lot of difference between this image and what I think is my best image of the Pleiades made with the ST80. A close look, though, will reveal that the new image has more detail and better color balance. In addition, it took A LOT of processing work to make the older image look like that--there were a lot of problems that had to be dealt with. Frankly, I wouldn't have posted a close-up of the older image. It just didn't look this good at full size!

The Double Cluster finally got high enough to image, but the Moon was only about an hour away from rising. Working quickly, I settled on a relatively short exposure time. Very little processing was required for this image:

NGC 869 (left) and NGC 884
Click here for full size

Exposure: 20x90@ISO1600
Telescope: AT72EDII
FF/Reducer:  ATR8 (f/4.8)
Mount: Vixen Super Polaris
Camera: Canon EOS Rebel T3
Processing: Deep Sky Stacker, Photoshop CS6

Cluster NGC 869 contains an asterism that I call Perseus Man. Some call it The Cowboy.

Now, for the negatives.

The scope is difficult to balance on the declination axis on the Vixen Super Polaris. Judging by the subs that I got, this is probably not a big issue. After all, the mount only has a right ascension motor, and I'm not autoguiding.

The only troubling issue has to do with the ATR8 field flattener/focal reducer. It was advertised as providing "images that are sharply focused out to the very corners of a large format DSLR chip." Although much better than the ST80 (with no flattener), the images still have distorted stars out toward the edges, as seen in this full-size clip from the Deneb image, above:

I'm not certain of the cause. I wonder if I didn't install the T-ring correctly. It's also possible that the flattener doesn't perform quite as advertised. I will do some investigation and testing.

Other than that, I am very pleased with the results. With the winter constellations coming up, there are a lot of targets to image. So what's next? Sword of Orion? Horsehead and Flame? Monkey Head? M35? Dare I try the Flaming Star or the Christmas Tree? I think a return to the X Bar Ranch is in order.

Sword of Orion

Yet another image of the Sword of Orion. I admit that it's one of my favorite targets, however, my primary purpose was to test how the Baader Contrast Booster performed.

The Moon rose around 10:00 PM, so my window was tight. I limited each set of exposures to 8 "good" subs each. The exposure times were 5, 15, 30, 60, and 120 seconds at ISO-3200. Images were stacked in Deep Sky Stacker with darks, flats, and bias frames, and then processed in Photoshop CS6 using the former Google Nik Collection.  (The current version of the Nik Collection can be found at DxO.)

Sword of Orion; ST80 w/Baader CB on Vixen SP; Canon EOS Rebel T3

Close-up of Messier 42 (right), the Great Orion Nebula, and Messier 43 (lower-left), De Mairan's Nebula.

Close-up of Running Man Nebula

The detail on this version isn't quite as sharp as my previous attempt. I think this may have been due in part to the seeing being poor (a front had come through the day before). More 120-second subs would have definitely helped.

The filter performed as expected. There was very little chromatic aberration, and I did nothing to remove what little there was. Note how the stars are not nearly so bloated as in the older image. Keep in mind that these images are from a relatively inexpensive achromat!

The distortion that is particularly noticeable in the stars on the left is due to coma.

Google recently made their Nik filter collection free to the public. There are tons of features and options, and I haven't explored them all. I used the Detail Extractor from the Color Efex Pro 4 collection and Dfine 2 noise reduction filters for these images. I was particularly impressed with the Detail Extractor as it brought out some very faint parts of the nebula in the lower part of the full-size image.

X Bar Ranch Nature Retreat

My older son and I spent a couple of nights at the X Bar Ranch Nature Retreat near Eldorado, Texas. The ranch features hiking and bike trails, and they have observing fields for amateur astronomers. They also host the annual Eldorado Star Party.

The sky at the X Bar Ranch is rated Class 2 on the Bortle Scale, which is almost as dark as possible. The night sky is amazing!

Below is a panorama of the one of the observing fields, taken from the deck of the Live Oak Lodge. The area is kept mowed, and electrical outlets are located on the back of the lodge and surrounding cabins:

We stayed two nights, but it was only clear on the first night. Seeing was steady above about 20 degrees, with some haze below that. I set up in a small field outside of our cabin and took some pictures of the Milky Way, and the Lagoon and Trifid nebulae. Here is a single 2-minute exposure of the Milky Way taken at ISO-3200 with the Canon EOS Rebel T3 (1100D) mounted on the Vixen Super Polaris:

The very dim illumination of the field at the bottom of the image is from some small, solar-charged walkway lights located behind the camera. The regular observing field is darker.

This is a crop of a stack of 27 2-minute exposures at ISO-3200:

Compare that image to images that I took at the same time two years ago from the SHSU Observatory. While I am pleased with how the older images turned out, they required a great deal more processing to tease the stars out from the light pollution. Most of the time that I spend processing images is usually concerned with removing haze and gradients caused by city lights. More on light pollution later...

One of my goals that night was to make a mosaic of four to six images in the area around the Lagoon and Trifid nebulae. Time was running short, though, and the Trifid was in the haze by the time I got to it. I had to settle for three sets of images. Still, I think it turned out well over all. Here is a mosaic stitched together using Microsoft Image Composite Editor (free software alert!):

Each of the three images is a stack of 12 2-minute exposures at ISO-3200. All were taken with the Canon EOS Rebel T3 (1100D) on the Orion ShortTube 80 with a Baader Contrast Booster filter. The scope was mounted on the Vixen Super Polaris.

I'm really impressed with how well the Baader Contrast Booster works at minimizing chromatic aberration. After using this filter a few times I've concluded that my ShortTube 80 crown/flint achromat is now working about as close to the performance of an ED achromat as it ever will. If only I could find a 1.25" field flattener...

Here are close-ups of the Lagoon and Trifid from the images that compose the mosaic:

Messier 8, The Lagoon Nebula

Messier 20, The Trifid Nebula

The sky here at the ObservaRory is about a 4.5 on the Bortle Scale. The Milky Way is fairly bright overhead, but is lost in the light dome of Huntsville, Texas near the horizon. The difference between the ranch's Class 2 sky and my Class 4.5 sky was immediately apparent, both to the naked eye and through the scopes. Even the polar alignment scope on the mount had a better view at the X Bar Ranch!

To illustrate the difference, compare these two subs taken exactly one month apart. Each image is a 2-minute exposure taken at ISO-3200 with the same equipment under similar weather conditions. No processing has been performed on either image, except to reduce them for display here. (The yellow cast was caused by the Baader Contrast Booster.)

Bortle Class 4.5 Sky at the ObservaRory

Bortle Class 2 Sky at the X Bar Ranch

Besides the darker background, many more stars are visible along with fainter portions of the nebula.

I am definitely spoiled by the sky in West Texas. I plan to make more trips as often as I can.

I hope to visit the X Bar Ranch again, too. The accommodations are comfortable, and the scenery is beautiful. The Meador Family, who own the ranch, are terrific hosts. They've thought of nearly everything and seem very friendly. If you happen to head that way, also check out the Caverns of Sonora:

Lower Room, Caverns of Sonora

Comet C/2013 R1 (Lovejoy)

Lately, comet ISON has been getting a lot of attention in the press and among astronomers, but at present it is difficult to see because it is close to the horizon just before dawn. Comet C/2013 R1 (Lovejoy), however, is considerably higher up in the early morning sky at my latitude.  It reached naked eye visibility in early November.

Comets are named using a convention that indicates the type of comet, and the year, half-month and order in which it was discovered. The discoverer's name is often included, and is sometimes used as the familiar name for the comet. This comet was discovered in September 2013 by famous amateur astronomer Terry Lovejoy. It is a long-period comet, with an estimated orbital period of over 10,000 years.

I made these images early in the morning on November 13. The first is a stack made in RegiStax 5 of 16 two-minute exposures centered on the comet core. The comet was moving rather quickly, so over time it moved a significant distance within my camera's field of view. As a result, aligning the images on the comet core caused the stars to trail.

Comet C2013 R1 (Lovejoy); ST80 on Vixen SP; EOS Rebel T3; 16x120 at ISO-1600

The second image is a combined stack of four images using the comet stacking settings in Deep Sky Stacker. The program attempts to stack the comet and stars separately, then combine them.

It did a fair job of producing the image, but it washed out the color of the comet and left "holes" in the brighter stars. After a bit of work I got most of the color back and fixed the stars.

Although it does not have the detail of the first image, it looks better than a single frame.

4x120 at ISO-1600, stacked in DSS using the "Comet and stars" stacking mode.

Messier 5

Messier 5 is a globular cluster in Serpens Caput (the Serpent's Head). It is one of the brighter globulars and is visible to the naked eye from dark locations.

For for those of you who are only interested in seeing the picture, here it is. Boring details about the imaging session are below. :)

Messier 5; ST80 on Vixen SP; 10x120 at ISO-800

Last night had nearly ideal viewing conditions, and I like to take any opportunity that I can to do some imaging or viewing, even if it's only for a short time. Fortunately the mount was already set up from the solar imaging session earlier that day, so I decided to work on improving my alignment skills.

Messier 5 was a good target for testing since it is fairly bright and was located near the celestial equator. As I've stated before, I use an old Vixen Super Polaris mount that was probably manufactured in the mid-1980s. The mount's polar alignment scope has an outdated reticle with a circle in which one is supposed to center Polaris. The circle is intersected by another circle that is drawn 48' from the center of the reticle, which represents the North Celestial Pole.  The position of Polaris has changed significantly due to precession, so I've had to estimate where to place Polaris in relation to the markings on the reticle. Until last night my attempts have been anywhere from bad to not quite so bad.

I downloaded an app named Polar Finder for my Android phone. It features an iOptron reticle that makes it easy to pinpoint where Polaris should be in my Vixen finder scope. I estimated the location in the reticle, aligned the mount, and then took 23 two-minute exposures.

The results were pretty good! There was a little bit of drift, but the main problem was just periodic error, which I have no control over, anyway. The image below is a combination of all of the exposures made in Startrails. It illustrates how much the mount moved off target during the session.

23 images combined in Startrails, showing the effects of periodic error and misalignment.

The stars are streaked up and down due to periodic error. I expected to see something more like the oscillations captured during the 1998 QE2 imaging session, but apparently the alignment was very good. I think that the small "hook" to the right was due to vibration or wind affecting the mount. I'm looking forward to trying this again and taking long exposures on some galaxies and nebulae!

Asteroid 1998 QE2

Asteroid 1998 QE2 passed relatively close to Earth back on May 31, 2013. It remained relatively bright for several days after its closest approach, and I was able to capture it with my ST80 on June 3rd.

1998 QE2 is classified as a Potentially Hazardous Object because its orbit may occasionally bring it close to Earth. It is unlikely that 1998 QE2 will ever pose a significant threat, though.

Below is a link to a movie composed of 100 30-second exposures made at ISO-6400 with my Canon EOS Rebel T3 (1100D). The exposures start at approximately 9:47 PM CDT and end around 11:09 PM CDT. The bright star near the bottom is Yed Posterior in Ophiucus. Several satellites can be seen streaking through the video.

1998 QE2 Movie

I had to manually remove the effects of periodic error and bad polar alignment from each frame. The image below illustrates the effects of these errors over time. It is a combination of all 100 images compiled in Startrails. The up/down oscillation is due to periodic error, while the progression from left-to-right is the result of incorrect polar alignment. Autoguiding, Periodic Error Correction and various alignment techniques can reduce or remove these effects. Sadly, my mount does not support autoguiding or PEC.

The effects of periodic error (up/down oscillations) and misalignment (progression from left-to-right).

Lightning!

I usually use a DSLR to capture lightning images, but this time I set up my Samsung Galaxy S III in the window at my office and caught a couple of strikes on video. I converted the MP4 video file to AVI and used VirtualDub to copy and paste the individual frames with lightning in them to Paint.NET to save them to files. The first strike was split up between a couple of frames, so I combined them using Startrails. Pretty cool for a phone, huh?

Look carefully where the bolt meets the ground and you can see the reflection of my hand in the window.

Huntsville Panorama 2

I learned a few lessons from my previous attempt to create a nighttime panorama of the town, so I set about trying it again at the first opportunity.

Right-click on the image and open it in a new tab or window for best viewing.

The main differences between this and the previous version are:

• I made sure that the camera was level before taking pictures, so it was not necessary to cut out a great deal of the original images in order to level the view.
• I picked a better location on the parking garage roof that granted a wider view of the town.
• Each image is a stack of two separate exposures (1/2 second and 5 seconds). This helps bring out the contrast on brighter objects.

Also, I found that the reason that Hugin failed on the last step on the previous attempt was because I had not installed Enblend.

From left to right:

• The Bank of America building on the west side of town
• Businesses at the I-45/Hwy 30 intersection, Home Depot and the Holliday Transfer Facility
• Sam Houston Village at Sam Houston State University
• The LDS Institute
• Belvin-Buchanan Hall
• Elliot Hall (the building with the two bright white lights)
• Businesses at the intersection of U.S. 75 and 11th Street (Hwy 30)
• First National Bank
• First United Methodist Church
• The Square, including the Walker County Courthouse
• First Baptist Church Family Life Center
• First Baptist Church sanctuary
• Lone Star Hall
• Huntsville Unit

Huntsville Panorama

The family and I went out last night to look at Christmas lights. If you're in the Huntsville, Texas area, I highly recommend visiting Bob and Sandra Moody's display on Spring Circle Loop. It is the best display in town, in my opinion. Visit their web site at http://moodychristmas.weebly.com/ for details on the display and directions to their house.

My older son likes seeing cities at night, so we finished up the outing with a visit to the top of the Sam Houston State University parking garage. Here is a panorama of the town from the north side of the garage:

Right-click on the image and open it in a new tab or window for best viewing.

I used a free program called Hugin to create the panorama. It matches up and aligns the individual images, "distorting" them as needed to make them fit together. The program worked fine until the last step, where it was supposed to stitch the modified images together. Fortunately, it wrote the images to disk, and I was able to put them together myself in Paint.NET.

Visible in this image, from left to right, are:

• A loblolly pine tree.
• The shopping center at Ave Q and 11th Street.
• The First National Bank Building.
• First United Methodist Church (with a star on top).
• The Square, including the Walker County Courthouse.
• First Baptist Church (with the white steeple).
• The (infamous) Huntsville Unit, including the old rodeo arena.

Star Trails

This is a star trail image taken from my front yard. The stars are seen here "swirling" around the North Celestial Pole (NCP), which is located near the bottom of the image. The bright star near the NCP is Polaris, the North Star.

Located about one third of the way between the NCP and the upper-right corner of the image are two bright trails that were formed by Kochab and Pherkad. They form part of the bowl of the Little Dipper. The bright stars at the top of the image are part of the Big Dipper.

The light trails of several aircraft and a few satellites are also visible.

This image is a composite of 282 30-second exposures (2.35 hours total). They were combined with a neat little program called Startrails.

Star Trails around the NCP; Canon EOS Rebel XS (1000D); 282x30

HDR Image Processing - The Sword of Orion

The Sword of Orion is one of the most difficult deep space objects to process that I know. The problem is that some portions of the nebulae are very bright, while others are very dim. Bringing out the detail in the fainter portions overexposes the brighter areas, and toning down the brightness to reveal the detail in the brighter areas hides the darker ones. In photography, such an image is said to have a high dynamic range.

High dynamic range (HDR) photography is an art in itself. There are many tools and techniques for processing HDR images. This article lists the steps that I follow for processing some HDR astroimages in GIMP.

Here is the short version of the process:

1. Take groups of images at different shutter speeds (e.g., groups of 1-second, 5-second, and 10-second exposures).
2. Stack each group of images to create "master" images that represent each shutter speed. (For example, stack all of the 1-second exposures together to create a master 1-second image.)
3. Load the individual master images as layers into a single image in GIMP, with the shortest exposure time at the bottom, progressing to the longest at the top.
4. Align the layers using the stars on each image.
5. Select overexposed areas in each layer, feather the selection, invert it, and then create a layer mask to bring out detail from the lower layers.
6. Flatten the image.

The only difficult part of the process is in deciding on the shutter speeds. Experiment with different exposure times and choose those that overlap without losing image detail. My suggestion is to use more exposure times than you will probably need. It is better to have groups of images that you end up discarding than to have too great a gap in the dynamic range for the process to work.

Below are copies of the master images that I used for the Sword of Orion. You may use them to experiment with. The original images are very large files, so these have been reduced to save space and bandwidth. All images were taken at ISO-1600 on my Canon EOS Rebel XS DSLR using the Orion ShortTube 80.

1 second

5 seconds

10 seconds

20 seconds

60 seconds

120 seconds

Note how the brighter areas become progressively more washed out as the exposure times increase.

I selected these shutter speeds based on trial and error. My mount does not have the ability to autoguide, so the longest exposure time I can usually hope for is around 3 minutes. A 3-minute test exposure did not reveal any more detail than the 2-minute exposures, so I chose 2 minutes as my maximum. Your mileage may vary...

Each master image must be aligned with the others. This can sometimes be done with a plug-in, such as the alignment "filter" in Georg Hennig's Gimp Astronomy Plugins. I have had only limited success with this, though, so I prefer to align images manually.

To manually align the images, load the shortest exposure into GIMP, and then load each successively longer exposure as a layer. The image with the longest exposure time should be the top layer. Starting with the top layer:

1. Set the layer opacity to about 50% to allow the layer below to show through a bit.

Load all master images as layers in a single image.

2. Select the layer below from the Layers palette and use the Move Tool to move the selected layer to line up the stars. You can use the keyboard arrows to move pixel-by-pixel, if needed.

Use the Move Tool to line up the stars.

 3. When the two layers are lined up, set the opacity of the upper layer back to 100%, and then click the visibility icon (the "eye") on the Layers palette to hide that layer.

4. Repeat steps 1 through 3 for the next layer, and continue until all layers are aligned.

Next, create layer masks to bring details from the lower layers up through the overexposed sections of the upper layers:

1. Turn on the visibility for all layers and select the top layer.

2. Select the Fuzzy Select Tool from the Toolbox, and then set the Fuzzy Select Mode to Add to the current selection.

Fuzzy Select Tool and Fuzzy Select Mode.

3. Select the overexposed areas. The Threshold may be set in the Toolbox to allow the tool to select larger or smaller areas.

Select the overexposed areas on the selected layer.

4. Select Feather... from the Select menu, and set the feathered area to a large value. For my image (the full-size version) I selected 120 pixels.  The exact value will depend on the size of your image and the size of the overexposed areas. In general, the shorter the shutter speed the smaller the area that needs to be feathered. Experiment with different values to see what works best for you.

5. Select Invert from the Select menu.

6. From the Layer menu, select Mask and then Add Layer Mask... Click Selection from the Initialize Layer Mask to list, and then click Add. Part of the layer beneath will show through into the selected layer. The feathering from step 4 creates a gradual transition between the images. If the transition appears unnatural, then undo everything back to step 4 and try a different feather value.

First layer mask on feathered selection.

7. Select None from the Select menu to clear the selected area.

8. Turn off the visibility on the current layer, then repeat steps 3 through 8 for the next layer.  Continue until all layers have been processed. No processing is needed for the lowest (background) layer.

All layer masks created.

9. Once you are satisfied with the image, select Flatten Image from the Image menu to combine all of the layers into a single layer.

I do most of the rest of my image processing after merging the layers. Experiment with different processing sequences to determine whether some steps are better performed before or after merging.

This is by no means the only way to process HDR astroimages. I have found, however, that it is easy to do and produces good results; and, you can't beat the price of GIMP!

Focusing with a Bahtinov Mask

Polaris B asked in a recent post if I was using a Bahtinov mask for focusing. I'd never heard of such an animal until then, but after some research on the Internet I found that it is a very simple device to use. Basically, the mask is a pattern of slots that one places over the end of the scope. The slots produce a pattern of diffraction spikes around stars, one pair of which moves as the scope's focus is adjusted. The scope is in focus when this pair of spikes is centered in the pattern.

Bahtinov masks are available from various manufacturers and retailers. You may also generate your own mask using the astrojargon Bahtinov Focusing Mask Generator. One advantage to using the generator is that you can experiment with the parameters to tweak the performance of the mask.

I generated a mask for my ST80 using the default parameters, printed it on card stock, and cut out the slots with a hobby knife:

Bahtinov Mask printed on card stock.

I remove my scope's dew shield and fasten the mask in front of the objective lens using transparent tape. After polar aligning the mount, I swing the scope around to a bright star and view it through the live view mode of my DSLR camera.

The image below was taken while focusing on Sirius:

Sirius through the Bahtinov Mask.  At left, the image is out of focus.  At right, the star is in focus.

My new electronic focuser is capable of making fine adjustments, so centering the spike is relatively easy. When the star is in focus, I remove the mask, replace the dew shield, and everything is ready to go! The whole process takes only a couple of minutes, which includes the time that it takes to manually point the scope at the star. That's a big time saver over my old method, which would take up to half an hour and didn't always yield satisfactory results.

Despite the mask's ease of use, though, I still cannot see the monkey.

Software

In case anyone is curious, here is the software that I use to process astroimages:

• RegiStax 5, for stacking subs and performing wavelet sharpening.
• Paint.NET, for simple image manipulation.
• GIMP, for advanced image manipulation.
• A set of astronomy plug-ins for GIMP.  The star-rounding filter is particularly useful.
• Neat Image, for noise reduction.