Sunday, July 23, 2017

Two visitors from deep space

While I have been spending time familiarizing myself with the 8-inch Celestron EdgeHD Schmidt Cassegrain I recently bought and taking photos with it, I've also been observing with my 15-inch Dobsonian last week at the local club's dark sky site. Normally, it's cloudy and murky here during the summer, but windows do open in the weather of good conditions for observing faint objects from time to time. While I observed the usual Messier, NGC and IC objects that are prominent in the summer skies, I stopped to take a look at two icy visitors to the inner Solar System that are observable right now as soon as the skies are fully dark. They are the long period comet C/2015 V2 Johnson and the periodic comet 71P/Clark.
 
 
C/2015 V2 Johnson is a long period comet that has been on the scene for months now, and now it's on it's way back into the frigid, dark outer reaches of the Solar System. Discovered by Jess Johnson of the Catalina Sky Survey, this comet is escaping the Solar System on a hyperbolic trajectory forever after reaching perihelion last June. It's original orbit had an aphelia of about 59,000 astronomical units or nearly a light year away from the Sun, but gravitational perturbations from the giant planets have accelerated it to Solar escape velocity. Through my 15-inch at 227X, it appeared as an elongated object of about eighth magnitude with a bright inner core. Right now C/2015 V2 Johnson in Virgo, soon to be lost in the twilight then daytime skies. It's soon to be a very faint object for large telescopes only, so if you wish to see this comet, take any opportunities available now since it will never return.

 
The periodic comet 71P/Clark on the other hand has been seen on a number of occasions since it's discovery in 1973 by Michael Clark at the Mt. John University Observatory. This periodic visitor has an orbital period of 5.5 years, an orbital inclination of 9.5 degrees and an eccentricity of .499. That places perihelion at 1.56 A.U., or just outside the orbit of Mars, and aphelion at 4.68 A.U. which brings it close to but not across Jupiter's orbit. It is therefore under Jupiter's gravitational spell. It has been observed at every apparition since it's discovery. Through the 15-inch at 227X, it looked more like a remote and faint galaxy or globular cluster than a comet. It had a round, diffuse appearance with a very weak central brightening, it was a little difficult to see due to the light pollution that pervades the Gulf Coast. This comet is impossible for small telescopes or anyone in badly light polluted areas, therefore plan to look for 71P/Clark in Scorpius from at least a reasonably dark area and an 8-inch or larger telescope. The comet just passed through perihelion three weeks ago, and is now fading quickly. The next appearance of 71P/Clark will be in 2023.

Friday, July 21, 2017

The last quarter moon

Last week, I set up the Celestron to image the last quarter moon at some of the same places I imaged it two weeks before as well as new locations I have not imaged before. The images below are the result, using the same camera and Barlow lens, which I am probably going to be upgrading soon. There seems to be a color fringing problem that originates with the Barlow lens, it's most definitely not the telescope itself. They can introduce chromatic and spherical aberrations, which the EdgeHD telescopes otherwise stamp out completely. I'll have to purchase some top shelf Barlow lenses to cure this defect, and even at that the atmosphere can also introduce color fringing because it acts like a weak prism. The only remedy for that is imaging when the moon or planet are as high in the sky as possible.
 
 
The Straight Wall or Rupes Recta is an immense thrust fault formed when the surface to the left of this feature dropped downwards relative to the ground to the right. Contrary to the namesake, it's not a vertical cliff, scarp or even a steep slope. The actual slope is about ten degrees, which people can walk up to the top easily over its 1,300 foot height and sixty five mile length. To an astronaut on the ground, it would look like a high hill that extends to both sides as far as he or she could see. To the right is a rille that formed when a lava tube collapses or the ground drops between parallel faults in the lunar crust. When the Sun angle at the site is low, both features are easy to see near the moon's first and last quarter phases through a small telescope. At first quarter, the straight wall is visible as a black line, at third quarter the Straight Wall's face is illuminated and appears white. At other times it's very hard to impossible to see.
 
 
Rima Hyginus is an immense rille formed by faulting and collapse of the overlying rock and large scale volcanic eruptions, including fire fountains and pyroclastic flows. The pits along it's length are not impact craters, they are volcanic vents and collapse pits where a large dike channeled magma from the lunar mantle to the surface and spread out over the surround area. The largest pit Hyginus is a caldera. Between Rima Hyginus and the crater Triesnecker are the numerous but much shallower and smaller Triesnecker riles, which cover the lava plains like a fracture pattern in a window across Sinus Medii. They are not related to the crater Triesnecker, but instead are related to the deposition of the mare lavas that formed Sinus Medii. These are likely of tectonic origin.

 
Near this large and nearly buried by lava flows carter is the strange impact feature known as Davy Catena, a line of small impact craters that formed at the same time. It's thought a small asteroid or comet was disrupted by the Earth's or Moon's gravity before the fragments plowed into the Moon. The impacts occurred after the lavas invaded the region then hardened as evidenced by their fresh appearance, along with most of the other smaller craters in the region.

 
Near the moon's south pole the surface is entirely composed of lighter aluminum rich rock and is saturated with craters. In other words, the formation of a crater destroys one or more craters already there. Here the large crater Clavius dominates the scene near the center of the photo, with the younger and smaller crater Tycho at the top center. The immense heat of the impacts that formed the larger crater left pools of impact melt that hardened into a smooth crater floor before being crater by smaller and less numerous impactors. Clavius itself has an arc of smaller crater of decreasing size across it's floor while the much younger crater Tycho still has an impressive series of rays extending from it. It was formed about 107 million years ago by an asteroid or comet striking the moon. The 56-mile wide crater has a central peak two miles high in the center that was pushed by the rebound of the Moon's crust during the impact that created Tycho. Photographs from the Lunar Reconnaissance Orbiter show a 120-foot wide boulder resting on the summit of Tycho's central peak.

 
The 50-mile wide crater Archimedes lies in Mare Imbrium with the nearby smaller and younger craters Autolycus and Aristillus. After the impact that formed Archimedes but before the impacts that formed the other craters, the lavas that formed Mare Imbrium invaded and flooded the crater floor from below and the surrounding plain. By the time Autolycus and Aristillus formed, Mare Imbrium has solified into a vast plain of dark basaltic rock. Despite the flooding of the crater by lava, the rim towers over two miles above the lava that forms the present crater floor. Consequently there is a flat crater floor under which the central peak and original crater floor is now buried under lava flows. Luna 2, the first probe to reach the moon crashed into it between the crater Archimedes and Autolycus.
 
In general, l had a successful run of imaging that lasted until dawn was underway. However, I will clearly need to upgrade the way I'm increasing the magnification to get these lunar close ups and planetary photos. That requires better Barlow lenses, one of which with greater magnification than the 2.8X University Optics Barlow I am using now. When the seeing is very good, I clearly could use a 4X or even 5X to get all the detail I can. That will require careful polar alignment because any error will cause the moon to drift as the telescope tracks. That will make close up imagery much harder, even with stacking video frames. All of these pictures were 75 frames stacked from 20 second AVI video files taken the week before. With the coming favorable apparition of Mars, I'll want to be ready to image this challenging planet before it's out of view for another eighteen months.

Wednesday, July 12, 2017

Success at last!

 
 
After a semi-successful beginning, I succeeded in getting a sharp picture of the entire moon with my Nikon F3HP camera. I tried using a Bahtinov mask to focus on the bright star Antares, which was nearby, and fired off a series of exposures using the mirror lock up and the self-timer to prevent mirror slap and vibration. That could have blurred the photos. I found the mask not to be as helpful as I expected, thus I am looking into obtaining a replacement focusing screen for my camera appropriate for astronomical photography. So I then refocused carefully without it, and took another series of exposures which ranged from 1/250th to 1/15th of a second to ensure one or two would be well exposed, but not too over or underexposed to be useable. I then refocused again and exposed another series of frames until the entire roll was exposed to assure at least one or two negatives would be in focus. That was the error I made last time, I thought I had got the moon in focus when in fact I hadn't, thus all of the negatives were blurred.
 
 
To couple the camera to the telescope, I simply used a T-adapter and T-ring for my Nikon to connect it directly to the rear cell of the telescope. I then took the film to a local photo lab for processing. After scanning, I used Adobe Photoshop to adjust the levels, resolution, image size, color balance and contrast before sharpening the image a little. The negatives are of good enough quality to make prints on photographic paper. Now that I can get sharp, well exposed shots of the whole moon, I will start taking photos of it through the whole lunar cycle. I'll also be able to do the same thing with the Sun, for which I now have an over the aperture solar filter on the way. A total solar eclipse is going to take place in the U.S. on the 21rst of August, and weather willing I'll be able to photograph it. For now, the Sun's very quiet magnetically, so few sunspots are visible on it now. When and if sunspots increase in number, I'll be photographing the Sun too.

Saturday, July 8, 2017

More images taken through the Celestron

During the holiday weekend, I set up the Celestron and proceeded to start taking 30-second AVI video files of the moon, Jupiter and Saturn with the video eyepiece for later processing. I then imported them into Registax 6, and extracted these still images from them. I have been learning how to use the features of Registax then Photoshop to suppress noise and get as sharp a picture as possible with a limited capability camera.
 
The crater Eratosthenes, lunar Apennines and crater Archimedes.
 
Saturn and it's rings.

The lunar north polar region, the crater Plato and the Alpine Valley.

Close up of the Alpine Valley.

Close up of the crater Clavius.

The Straight Wall and its surroundings.

The planet Jupiter and the Great Red Spot.

Close up of the crater Eratosthenes and lunar Apennines'.

Close up of the crater Tycho and its central peak.

Lunar terminator with the craters Clavius and Tycho.
 
Close up of the crater Plato.
 
 
The extreme close ups of the moon and the images of the planets were made in the same way, by placing a 2.8X University Optics Barlow lens between the telescope and the camera to stretch the focal length to nearly 6,000mm. The wider area images of the moon were made by directly coupling the camera to the telescope's visual back.That gave the required image scale for closes ups of lunar craters and the planets while the image remained relatively sharp in spite of the turbulence in the atmosphere overhead. The seeing was good, but not excellent. As for the color fringing I noted, it's not due to the Barlow lens of the optics, it's refraction caused by the atmosphere and the low altitudes of the moon, Jupiter and Saturn that are the norm during the summer. I have been able to partially remove that with Registax 6, but not entirely. However, I am very pleased with what I have been able to achieve thus far, especially with the close ups of the lunar craters and other lunar features such as the Straight Wall. I will keep working with this camera until I can find a better one, possibly a camera that can be used for both planetary and deep sky objects.

Sunday, July 2, 2017

Some early results with a "video eyepiece" and my very old Nikon film camera

 
Now that the Fourth of July holiday weekend is underway, and I now have a polar alignment scope and dew heater controller, it's time to begin mastering this optical and mechanical marvel known as a Celestron EdgeHD Schmidt-Cassegrain and an AVX mount. I have been practicing getting good polar and GOTO alignments, and learning how to use the All Star Polar Alignment feature in the hand controller. I have been able to get a star to stay still for half an hour, and just tonight I got the polar alignment scope roughly calibrated, then a decent polar alignment with is right afterwards.

At the same time, I was trying the telescope out with my inexpensive video eyepiece on the Moon, Jupiter and Saturn. I'm also starting to learn the intricacies of a nifty free program called Registax6. It extracts frames from the AVI video files, aligns them, and stacks them to form a still image that can be sharpened enormously BEFORE you import it into a photo editing program such as Photoshop. The results I have achieved so far include the work below.

The photo of Saturn was made with a 2.8X Barlow lens, but all of the lunar photos were taken at prime focus. In other words, I simply used the telescope as a giant telephoto lens. I'm sure I could indeed photograph VERY distant subjects during the day time with this telescope, but turbulence would blur the photos.
 
 

 
 
 
 I achieved much more success so far than I was ever able to with my old Meade model 628 6-inch Newtonian and equatorial mount and my camera. I wasted whole rolls of film because finding objects and focusing the camera were VERY hard, I got the exposure time wrong, the polar alignment was WAY OFF or some other glitch scuttled my photos. It was wonderful to see the result as soon as I finished recording the video on my lap top. However, these pictures also show I will have to get a much better camera and among other things, a flip mirror and filter wheel. The limitations are obvious, especially when I was trying to image Saturn. It's faint and quite hard for the camera to record it well. I would also like to be able to record video of deep sky objects or take still images at some point.
 
However, I will be using my film camera, which is a Nikon F-3HP that I had for over 25 years. It's was a top of the line camera when it was introduced back in 1980, and still is today as far as 35mm film cameras are concerned. I have a T adapter that make connecting my camera to the telescope simple and allows me to use it as a 2,000 mm F/10 telephoto lens. That is how the last picture was taken, using Fujicolor 200 color print film. I found focusing the camera difficult, and to address that I got a Bathitnov mask, but it appears a clear focusing screen is needed, or a flip mirror. The photo wasn't as sharp as it should have been, but aggressive use of un-sharp masking and careful scanning of the film made a presentable picture possible. The photo is of the entire frame, not cropped.
 
I am used to the simplicity and quick set up of Dobsonians, and I won't be retiring them any time soon. They beat the EdgeHD SCT handily in terms of light gathering power and resolution. My 15-inch Dob easily shows objects that simply cannot be seen through any 8-inch telescope at the same site. However, the SCT has very good image quality. Combine that with a mounting that is stable and has excellent pointing accuracy once you align it correctly, this telescope is a very good choice for an all around telescope. For someone who wants a GOTO telescope that can be used for imaging at a later date, in a package that will fit in any car and is easy to set up, an 8-inch Celestron EdgeHD SCT is a telescope you should consider. If I was starting out in astronomy today, I would have wanted this telescope for my first telescope, even though I would have had a lot to learn along the way.

Tuesday, June 20, 2017

Bought an 8-inch Celestron

 
Earlier this month, a long term goal of mine was fulfilled. I have always wanted to be able to take photos of the moon, planets and deep sky objects, but my experience with film decades ago led me to shelve the idea, Merely focusing the camera was very difficult, and light pollution made long exposure work difficult to impossible, I also found the venture too expensive and complicated for me so for nearly three decades I stayed with visual observing. Over the years, the cost of photography capable telescopes and mounts have gone down while the capabilities have greatly increased over was what available back in the 1980's. So I spent $2,500 on a 8-inch Celestron EdgeHD SCT with an AVX mounting and accessories needed to accomplish lunar and planetary imaging as well as visual observing. I have been using it over the past few weeks to familiarize myself with the telescope and mounting. Last Sunday I decided to try video imaging of Jupiter with my 60 dollar Orion Starshoot video eyepiece.
 
 

 
 
To get the video from which I extracted this picture, I inserted the stock 1 1/4-inch prism diagonal into the visual back so I can switch between the camera and an eyepiece. Once centered in the field of a high power eyepiece, I turned up the gain all the way on the camera, then inserted it and a 2.8X Barlow lens so I could focus and record the video. Because my polar alignment was not precise, Jupiter was drifting to the south as the telescope tracked the planet. The telescope-Barlow combination resulted in an effective focal length of nearly 6,000 mm, enough to get a large enough image on the very tiny chip the Starshoot video eyepiece has.
 
Once I had the video, I downloaded the program Registax6, which is a free program for extracting frames from video files and stacking them to form a higher quality still image, I washed the video through this program then further processed the image with Adobe Photoshop.
 
Un-sharp masking and adjusting the color balance was the final touches to the results you see here. I probably created artifacts in these images by heavy use of the wavelet functions in Registax and un-sharp masking in Photoshop, but the seeing was poor and the video was blurry. I suspect the prism diagonal may have added an odd color fringing effect to the planet, which will be investigated the next time I try imaging by switching to one of my mirror star diagonals.
 
 
The combination of an 8-inch EdgeHD SCT and an AVX mounting represents an incredible value for the price. While it's not perfect by any means, it's steady, portable, and the optics compare favorably to all reflecting Newtonian telescopes of high quality. In a head to head comparison on Jupiter and Saturn at 300X, the views were very similar. Faint features were easier to see through the 10-inch, mainly due to the greater aperture. When properly aligned with regards to the celestial pole and the GOTO system, the mounting can place target after target in or very near the field of view at 300X. It does however, require care be taken to get a good alignment with the sky, a process the hand controller walks you through. The mounting is rated for loads of up to 30 lbs. not including the counterweight(s). You will need another counterweight or a heavier one if you add a camera to this telescope in order to balance it properly. The tripod is rock solid, and vibration suppression pads make it even more so. Best of all, it breaks down into sections, which are the tube, equatorial head, counterweight and tripod, none of which weigh more than 20 lbs. Set up this telescope weighs in a 55 lbs. or so. All of it easily will fit in the back seat of a car. The telescope also works well with any eyepiece of good quality. I have a range of eyepieces of various designs, and tried them all with the Celestron. While no telescope can do everything equally well, this combination of telescope and mounting come closer to that impossible dream than most. Few telescopes work very well for both visual and imaging, and the EdgeHD optical tubes, which also are made in 9 1/4, 11 and 14-inch apertures, do indeed fill both roles well. The telescope runs off of 12-volt DC power, which can be supplied by an AC adapter or a portable 12-volt power source such as the one beneath the tripod. I have yet to take it out to a darker site than my driveway, but that opportunity may come this weekend, if tropical storms and hurricanes don't intervene. Right now tropical storm Cindy is leaving my area with a sloppy, wet and windy parting kiss.
 
I have no intention of retiring my Dobs, but since I have many more opportunities to observe and image the moon and planets than observing deep sky objects, I'd like to make more use of those nights at home. So I will continue to observe and sketch objects and post them here. I will also be posting lunar and planetary images, as well as images of comets and deep sky objects as I can successfully take them. For those interested in the telescope I used for the images, there is a very good article and review of this telescope in the December 2014 issue of Sky & Telescope. There you can see for yourself why this telescope is very popular among local amateur astronomers I know personally and in regional clubs.
 
 

Saturday, March 25, 2017

Return of the comets

Recently a number of comets have either entered the inner Solar System for the first time from far beyond the Kuiper belt or made another periodic return observable from Earth. As of now, four of them are nicely observable in modest telescopes if you can catch them from a reasonably dark site on a moonless night. Others are also observable, but much more challenging to see because they are either very faint, or incredibly diffuse. That is why I was not able to see the comet 45P/Honda-Mrkos-Pajdusakova at all even with my 15-inch, but 41P/Tuttle-Giacobini-Kresak was fairly easy to see with a 10-inch from the same site on a considerably poorer night. That comet is at this time in Ursa Major. The long period comet C/2016VZ18 PANSTARRS was small and faint, but I had little trouble spotting it with the same telescope. Both of these objects are well placed right now for evening observation. Two more comets for early risers or night owls that should be apparent in large binoculars and small telescopes is C/2015 ER61 PANSTARRS and C/2015 V2 Johnson are visible before dawn in Sagittarius and Hercules. They are well worth a look.

March is also a great time to peruse the star clusters and nebulae that line the winter Milky Way under warmer weather and at a convenient hour. One of my favorite winter star clusters is the open cluster M-93 in Puppis. Obvious in binoculars under good skies, through a 10-inch Dob even from my driveway it's bright, fairly large and looks like a mostly eaten pizza with the crumbs. Most of the stars are white or off white, but two bright orange stars also are within the cluster's boundaries. Whether or not they are related to M-93 I do not know.
One comet that moved from Perseus to Camelopardalis is the long period comet C/2016VZ18PANSTARRS. At the time of this drawing, it was about a magnitude 12.5 object that has a brighter center and an elongated shape, much like a distant spiral galaxy. It was faint and was best seen with averted vision. It will remain well placed for observation through this month into the next.
 Another fine winter star cluster is the very large and sprawling open cluster M-47 and it's neighbor, the smaller and fainter open cluster NGC-2423 which is to the lower right of M-47 in this drawing. It's a magnificent sight through my 11X56mm binoculars and even more so through a small to medium aperture telescope at low power through a wide or ultra-wide angle eyepiece. The bluish white stars are widely scattered in chains and clumps, far more than I could have sketched. Also in the same field is NCG-2423, which is a nice open cluster in its own right at higher magnifications, but at low power it tends to blend into the star field around it.
The best and brightest of the comets now in the inner Solar System is 41P/Tuttle-Giacobini-Kresak, a Jupiter family comet with an orbital period of 5.4 years and an orbital inclination of 9 degrees. At perihelion, it's one astronomical unit from the Sun as we are, at aphelion it's 5.1 AU from the Sun, just inside Jupiter's orbit. At the time of this drawing, it was around 7th magnitude, but it was very diffuse with a brighter inner region. This comet is close to the Earth, in the half hour or so I was watching it, it's motion against the background stars was very obvious. The skies were not very good at the time I was observing it, and I was not able to find it with my 11X56mm binoculars. It will however remain observable for quite some time, but act now if you want to catch this comet when it's fairly bright. It's next return will take place in 2022.