Monday, May 14, 2018

Seven Jovian Moons in Under and Hour


On the night of May 8-9, 2018, Jupiter moved into opposition. Now officially and “evening object”, there is no better time to attempt imaging its smaller moons. Although, I was unable to successfully image the tiny satellite that was my primary objective, I did succeed in imaging seven Jovian Satellites … all within an hour’s time.

When a planet or asteroid is in “opposition,” it can be found directly opposite the sun. For the superior planets, this generally means the planet is closest to the earth as well. The combined effect of the “opposition surge,” a brightening of rough surfaces when opposite the sun, and closeness makes the days around opposition the best time to search for faint moons orbiting the planets.

I really want to image Thebe. Orbiting close to Jupiter, Thebe was discovered by the Voyager spacecraft in 1979. I can find no example of amateur imaging of Thebe. However, the satellite orbits outside the orbit of Jupiter’s closest observable satellite, Amalthea. Although it is one magnitude fainter than Amalthea, the relative ease in which I imaged Amalthea makes me hopeful that imaging Thebe is a possibility.

Unfortunately, Thebe passed through its greatest elongation only one hour after Jupiter-rise. Our planet’s thick and turbulent atmosphere thwarted my imaging attempt.

Later that evening, Amalthea passed through its greatest elongation. I had never attempted to image Amalthea with the new ZWO1600 camera or color filters. I took a number of exposures through several different filters. The most successful image was created from a stack of 50 three-second captures imaged through the luminance filter.


Jupiter and Five Satellites

Amalthea can easily be seen taking her place among her larger brothers and sisters.
Even more exciting to me is this faint star just off Jupiter’s southern limb.

Detail of Last Image showing 14th Magnitude Amalthea and a 16th Magnitude Star


Its name is GSC 06168-0775, and it is a nondescript 16th magnitude star in Libra. It made me happy because at magnitude 15.85, it is the same brightness as Thebe. Moreover, it appears closer to Jupiter than Thebe at greatest elongation. I have proven I can image Thebe. All that is left to accomplish is to actually image Thebe. Keep watching the blog to follow this ongoing sage.

Because Jupiter’s blinding light is much dimmed by the CH4 filter, I attempted to image the inner system with the CH4 filter. I didn’t get any convincing evidence of capturing Amalthea even with a 90-second exposure. In the future, I plan to attempt longer exposures.

Jovian System imaged with a CH4 Filter.


On this night, I could actually see 4th magnitude stars in my suburban sky. I decided to attempt to image Jupiter’s faint outer satellites.

Jupiter has 69 confirmed moons. Many of them may be photographed with amateur equipment. Using, JPL’s Horizon Website, I obtained the position of Jupiter’s sixth and seventh discovered satellites, Himalia and Elara. Because these tiny moons are faintly traveling through highly-populated star fields, I imaged each predicted star field 30 minutes apart. While the stars would remain static, the tiny moons would move between the exposures.

I had already successfully imaged Himalia two years ago, so I was not surprised to have captured it.


Elara, had eluded all attempts at imaging. It took me a long time to find star-like Elara moving among the stars. I was looking for faint stars, Elara surprised me with her brightness. I have now imaged 24 planetary satellites.



Although my main objective, Thebe, could not be images, enjoyed a highly successful evening. Not only did I add another elusive moon to my list of accomplishments, I now am more confident that I am able to image Thebe in the near future.

Keep Looking Up to Clear Skies.

Ken

Wednesday, May 9, 2018

Sweet Serendipity



I chose the ZWO 1600 Mono Cooled because of its relatively wide field of view for the price. Likewise, having previously worked with the ZWO ASI224MC planetary camera, I felt familiar with the product and software (or so I thought.) With a new filter wheel and seven different filters, I was ready to conquer the world of monochrome and narrow-band imaging.

ZWO 1600 Camera attached to my Meade LX-850
Zwo Motorized Filter Wheel












Of course Maryland nights in March are notoriously schizophrenic. This year was no exception. Every moonless night, clouds filled the sky. So, I again made plans to meet a friend in Southern Georgia, packed my scope into the tiny Fiat 500 and braved the treacherous lanes of I-95 South.

Although never-ending lane closures in South Carolina delayed my arrival, The Stephen Foster State Park greeted me with crystal skies. My exhaustion dissolved as I saw a beautiful cone of the Zodiacal Light over The Okefenokee Swamp. I jumped out of my vehicle and immediately set my scope up next to my friend’s newly-purchased Meade LX-850.

While the telescope's temperature equalized to the chilly night air, I set up a Canon 60D on a steady tripod, pointed it toward Orion and allowed it to take 30 second exposures until the battery expired. Although my makeshift dew shield interfered as the breezy swamp air flowed by, I like the results. I had never attempted video astrophotography. Clearly, we positioned ourselves on the busy air corridor between Florida and the Northeast.


Deep sky astrophotography still challenges me with the paltry number of images obtained on a given night. Now that I would be imaging each object in multiple wavelengths, I planned to observe only a few  objects each evening.  The first two nights of the trip, I planned to observe only seven deep-sky objects. Between nebulae and galaxies, I would attempt to image a few of the Gas Giants’ irregular satellites


NIGHT 1

Object                     Total        File          Total        Description             
                                Time        Type        Images

Venus                      10 mins.  .AVI         4000        One Video of Each  Luminosity/Red/Green/Blue Filters
Mercury                  10 mins.  .AVI          4000        One Video of Each  Luminosity/Red/Green/Blue Filters
Flats                        30 mins.  .FIT          25            Five exposures of each- Luminosity/Red/Green/Blue/H-Alpha Filters
Horsehead Nebula 150 mins. .FIT          30            Six 5-minute exposures of each - Luminosity/Red/Green/Blue/H-Alpha Filters
Contingency Dark    5 mins.    .FIT          1              Single 5-minute dark while slewing
Cone Nebula           100 mins. .FIT          20            Five  5-minute exposures of each - Red/Green/Blue/H-Alpha Filters
Contingency Dark    5 mins.    .FIT          1              Single 5-minute dark while slewing
JIV – Himalia           15 mins   .FIT          3              Three 5-minute exposures of outer Jovian satellite – Luminosity Filter
JIV – Elara               15 mins   .FIT          3              Three 5-minute exposures of outer Jovian satellite – Luminosity Filter
Ringtail Galaxy        100 mins. .FIT          20            Five  5-minute exposures of each – Luminosity/Red/Green/Blue Filters
Contingency Dark    5 mins.    .FIT          1              Single 5-minute dark while slewing
S IX - Phoebe           15 mins   .FIT          3              Three 5-minute exposures of outer Saturnian satellite – Luminosity Filter


NIGHT 2

Object                     Total        File          Total        Description             
                                Time        Type        Images
Flats                        30 mins.  .FIT          25            Five exposures of each- Luminosity/Red/Green/Blue/H-Alpha Filters
Orion Nebula          150 mins. .FIT          30            Six 5-minute exposures of each - Luminosity/Red/Green/Blue/H-Alpha Filters
Contingency Dark    5 mins.    .FIT          1              Single 5-minute dark while slewing
Rosette Nebula       60 mins.  .FIT          20            Three  5-minute exposures of each - Red/Green/Blue/H-Alpha Filters
Contingency Dark    5 mins.    .FIT          1              Single 5-minute dark while slewing
M104                       100 mins. .FIT          20            Five  5-minute exposures of each – Luminosity/Red/Green/Blue Filters
JIV – Himalia           15 mins   .FIT          3              Three 5-minute exposures of outer Jovian satellite – Luminosity Filter
JIV – Elara               15 mins   .FIT          3              Three 5-minute exposures of outer Jovian satellite – Luminosity Filter
M87                         100 mins. .FIT          20            Five  5-minute exposures of each – Luminosity/Red/Green/Blue Filters
Contingency Dark    5 mins.    .FIT          1              Single 5-minute dark while slewing
S IX - Phoebe           15 mins   .FIT          3              Three 5-minute exposures of outer Saturnian satellite – Luminosity Filter


Knowing that I would be working with these images for the next few months, I needed a way to leave Georgia with more images on my hard drive.

I had an idea.

The LX-850 must be balanced on three axes. Not only must the operator balance the right ascension axis with the huge counterweights, the declination axis must be perfectly balanced as well. Unfortunately, the scope is designed to be intrinsically out of balance. The plate to which the heavy Optical Tube Assembly has more metal on one side.  A counterweight is provided to offset that difference. However, the counterweight over compensates. In order to achieve perfect balance, something must be placed on the opposite side of the counterweight.


LX-850 Mount. Left side of mounting plate is much larger than right side.


I decided to attach my modified Canon Rebel XS DSLR camera and 90mm Pro Optic scope to balance the counterweight. Programing the camera to take five-minute exposures throughout the night, the Canon would serendipitously image the objects the main scope pointed toward. I realized that many of the images would be smeared as the scope slewed to other objects or I centered objects in the main field of view. However, some exposures should capture wide-angle views of the objects I imaged.


LX-850 with 90mm Pro Optic
Maksutov-Cassegrain and Modified Canon Rebel DSLR acting as Counterweight


Primary observing did not go well on either night. The New ZWO 1600 seemed to randomly choose its own exposure times leaving many of my images underexposed. Likewise, the camera seemed often to forget it was able to cool itself marring my images with noise. When everything seemed to be going well, I discovered the camera had forgotten that it had a filter wheel. The exposures that seemed be taken in red, green and blue light actually were only captured with one filter.

As Mercury was retrograde, I felt more like an astrologer than an astronomer.  I gathered my tainted image set and returned to camp.

I did briefly glance at the images acquired with the Canon. At first glance, they looked underexposed as well.  Thus, they were quickly forgotten.

Horsehead Nebula - Single Five-Minute Exposure - Pro Optic 90mm F/5.6 Lens - Canon Rebel XS (Modified)



With a storm front quickly approaching, we cancelled the rest of our trip. I bid my friend farewell, and returned to Maryland, crestfallen.

Sometime later, while struggling with Pixinsight to wring some usable images out of my data, I set my primary image set aside and looked at the images from the Canon. I pulled a single image of The Horsehead up and minimally processed it. I sat stunned as the Horsehead Nebula in all its difficult-to-image glory appeared in my screen.  

Horsehead Nebula - Histogram Stretched with Photoshop.


Yes, the image was imperfect. The less-than-perfect optics of the 90mm Pro Optic bloat stars along the edge of view. Moreover, whoever “modified” the camera, removing its infrared filter, damaged many pixels on the sensor. These show up as dark spots on the image and can be removed with flat fields.

Believing the images to be underexposed, I never bothered to gather flats or darks. Therefore, I immediately attached the camera to the 90mm Pro Optic and used a blank wall to get my flats.

Darks were going to be more difficult to acquire. They should be taken at the same temperature and exposure as the original images. How was I going to know the temperature of that humid swamp air weeks ago?  Again, serendipity stepped in to save the image. Remembering that the Zwo camera often turned its cooler off throughout then night, I need only look at the metadata from those noisy uncooled images. It was not difficult to get the sensor temperature from Zwo images taken nearly at the same time as the Canon images.

The first night was cold. Most of the uncooled images were taken at 5-7°C. I set the temperature of our refrigerator up to 6°C and placed the camera inside allowing it to take 10 five-minute exposures. The second night was warmer. Coincidentally, our garage’s temperature was the same 15°C as the swamp are on the night I took the images. The camera went from the fridge to the garage to get the second set of dark images.

With a little cropping and processing, I got the image of The Horsehead.


Here is the same data processed to bring more detail out in the nebula.



The images of The Cone Nebula were not as impressive. The nebulosity was barely visible at the edge of the field of view.



 However, with a little processing and a lot of cropping, I got a cute little image of The Christmas Tree.

The "Christmas Tree"


Images of The Rosette Nebula were not very impressive either. However, you can see its thick ring on the bottom left of the image.

Rosette Nebula - Single Five-Minute Exposure


With a little processing, The Rosette's famous ring structure becomes apparent.



Lastly, The Great Nebula in Orion shone brilliantly, I could see success on the unprocessed images. 

Orion Nebula - Single Image - Unprocessed

After stacking with Deep Sky Stacker.

Orion Nebula - Stack of 12 Five-Minute Exposures

After Working in Photoshop with the color.


When I look at these images, I cannot believe they were taken with an small telescope that I purchased to photograph the 1994 Annular Eclipse. The camera’s primary use is infrared photography.  The total cost of the setup (not including the mount) was $300.00.

Why did imaging with the new camera fail? The short answer is I was using software developed for planetary imaging to expose deep sky images. Of course not all of the images through the main scope were unusable. Those images will appear in some future blog posting.

Obviously, one doesn’t need budget-breaking equipment to obtain great astrophotographs. All that is required is good motor drive and a little serendipity.

Keep Looking Up to Clear Skies.

Ken


Seven Jovian Moons in Under and Hour

On the night of May 8-9, 2018, Jupiter moved into opposition. Now officially and “evening object”, there is no better time to attempt im...