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.