Exactly 25 years ago today, the Discovery space shuttle took off with the Hubble Space Telescope aboard. For all the mind-blowing images Hubble has been able to bring to us, the project started actually pretty badly…
Above all the funding challenges that such a large project faced, there were many issues on how and who should grind the primary mirror. In all three mirrors were built by three different companies should there be issues during production. The Challenger disaster in 1986 delayed the launch of the telescope, and when it was finally placed in orbit, a faulty mirror wasn’t able to correctly focus the image to the clear and crisp views everyone had expected. As the flaw was due to an error in the calibrating instrument during the final shaping of the mirror, it meant it was flawed to perfection, and could therefore be corrected by giving it “glasses”. It wasn’t until 1993 that corrective optics were incorporated and we could finally start exploring the potential of the telescope.
As the Hubble Space Telescope is in low earth orbit it is within easy reach to be serviced by astronauts, and five shuttle missions were dedicated to servicing Hubble, the last one being in 2009 to extend the operation until 2020. By then the James Webb Space Telescope (JWST) should be operational. Something to note here is that while Hubble could be serviced and maintained over time due to its proximity to Earth, JWST will be too far out, located at the L2 Lagrange point – 1.5 million km, beyond Moon’s orbit.
To celebrate these 25 years, NASA and ESA have released this wonderful galactic firework: Westerlund 2
Galaxies are always a challenge… Imaging objects such as nebulas within our galaxy is much better suited to my small telescope. At 700mm focal length, galaxies over 30 million light years away are rather small and lack detail. Nevertheless this is my go at Messier 95 and 96 in the constellation of the Lion.
These galaxies were discovered by Pierre Méchain in 1781 with a 12in telescope, nearly 4 times the size of mine.
Galaxies Messier 95 and 96 – Benoit Guertin
The image was scaled to 30% and I’ve added insets of the galaxies.
Telescope: Sky-Watcher 80ED
Camera: Canon XTi (ISO 400)
Image: 30 x 30sec
With the last maneuver planned for April 24th, the Messenger spacecraft will be officially out of fuel and unable to maintain proper orbit around planet Mercury. Scientists expect the spacecraft to crash onto Mercury on April 30th. Unfortunately the impact is expected on the opposite side of the planet, out of view from Earth’s observation posts.
I know for past spacecraft impacts such as those on the Moon, NASA had asked the amateur astronomy community to observe and record the impact. Out of luck and out of reach this time…
In astrophotography, a solid mount is key. But you don’t want something that is too heavy that can’t be transported to your favorite spot away from light pollution. iOptron has released a Tri-Pier combines the stiffness of a pier with the portability of a tripod. It can be used with their mounts, or with proper adapter to other makes. With 220lbs of maximum capacity, this can hold some serious gear. I can’t even think up 220lbs of astro-gear!
On the same night that I imaged Messier 44 I decided to hop over to another nearby open cluster: Messier 67. While M44 appears three times larger, both of these open clusters are estimated to be of roughly the same size, but M67 happens to be 5 to 6 times farther away.
Click on the image to get the full image, it’s scaled and cropped below.
Open Cluster Messier 67 Benoit Guertin
Telescope: Sky-Watcher 80ED
Camera: Canon XTi (ISO 400)
Image: 19 x 30sec
Yesterday when I processed and posted the open cluster Messier 44, I noticed I had captured a faint galaxy in the background. So while the stars in the open cluster are within our galaxy at a distance of 577 light years, that faint galaxy UGC 4526 is located at 200 million light years away. Therefore the photons captured by my 80mm telescope lens in my backyard and counted by my Canon camera exited the stars within that galaxy at the start of the Jurassic period when dinosaurs just became the dominant vertebrate on land. The light travelled 1,903,000,000,000,000,000,000 km to land on the camera sensor where each pixel is no bigger than 5.7micro-meter. Pretty mind-blowing when one thinks about it!
Magnitude 14 Galaxy UGC 4526 in M44 Benoit Guertin
In January Meade launched the Series 5000 MWA Eyepiece. With an apparent field of view of 100deg, this is the widest available from Meade. Currently only four focal lengths are available: 5mm, 10mm, 15mm and 21mm. The 5 and 10mm are available in 1.25in while the 15 and 21mm are only in 2in.
Overall this is an evolution on the Meade UWA with improved AFOV and eye relief, but with half the 5000 series Xtreme Wide Angle’s price.
A few days ago after taking some video of Jupiter with a modified webcam, I slewed over to the open cluster Messier 44 also known as the Beehive Cluster and changed over to the Canon XTi to take some long exposures.
Below is the result of stacking 20 x 30sec exposures at ISO 400.
Messier 44 – Open Cluster Benoit Guertin
Telescope: Sky-Watcher 80ED
Camera: Canon XTi – ISO 400
Image: 20 x 30sec
Planetary imaging is usually where everyone starts. The targets are bright objects in the sky such as the Moon and the planets that don’t require long exposures; Venus, Mars, Jupiter and Saturn. And because there are no long exposures, no need for a mount that tracks. The electronics of a webcam allows between 5 and 60 frames per second (fps), more than enough to get a good image that can be used with any sized telescope, and the result is a AVI movie that can be easily processed.
There are two ways to use the webcam:
Prime focus: the original webcam lens is removed and the telescope becomes the lens; like swapping lens on a SLR camera. Magnification is provided by the focal length of the telescope and the optional use of a barlow lens.
Eyepiece projection: the webcam replaces the eye and the magnification is provided by the ratio of telescope focal length to eyepiece focal length.
In my case I went with a prime focus solution, hence I needed a webcam where the original lens could be removed and replaced with an 1.25″ adapter to fit into the telescope’s focuser.
Philips Vesta Pro 680K webcam modified for use on telescope
The camera sensor, be it CMOS or CCD is sensitive to a wider spectrum than the human eye, therefore most have build-in UV and IR filter, either on the lens or the sensor. As this filter was on the original webcam lens I purchased a BAADER UV-IR Rejection 1.25″ #2459207 filter for use with the adapter. Refractors have a challenge getting all colours focused at the same spot, and even with an APO scope what falls in the UV and IR range will generally appear out of focus. Best to keep those out with a filter.
Today a good planetary imager can be purchased for under $200, but when I started, most astronomy imaging devices ran in the $1000+ camp. The Philips Vesta 680K was rather popular as a wonderful man by the name of Steve Chambers figured out how to easily modify the webcam electronic to get much longer exposures. The Vesta was also equipped with a CCD-based sensor, more sensitive than the CMOS technology used in most webcam. These modified webcam became to be known as Vesta-SC.
I’ve spotted Jupiter, can I take a photo? Actually you should take a video. The reason is that there is a great deal of turbulence in the atmosphere and this causes the image to blur and giggle about. By taking a video you are doing two things:
Capturing a large quantity of images which can be later processed
May happen upon a brief period of atmospheric stability
Here is a 30 second segment of Jupiter with my setup
I recommend taking a few videos with different settings such that you’ll be able to see after which provided the best results. Select an uncompressed format such as AVI as to not get compression artifacts, and AVIs are easily broken into individual image frames.
Software such as IRIS or REGISTAX can be used to process the video. REGISTAX is actually quite good and painless at doing this. Don’t be intimidated by the large number of settings and parameters, you can get great results out-of-the-box with the default settings.
The process breaks down into 5 steps:
Select your target (what you want the software to track on)
Filter on the frames that have good image quality; only keeping those that are sharp and resemble each other
Align (register) the individual images
Stack the individual images
Wavelet analysis and final brightness/colour balance
Because of the high number of images, you can actually improve image resolution by up-sampling or drizzling the image prior to stacking. The end result is often an image that can be scaled up by 2x while maintaining resolution.
Wavelet analysis is a type of sharpening, similar to unsharp-mask, but treating each level of granularity as a different “frequency”. While unsharp-mask is tuned to a specific size of detail, wavelet is able to treat various levels of details as different layers of the image and add the results.
Jupiter is a good target right now as it’s high in the sky, so you’re not looking through too much atmosphere and turbulence. Now this is far from my all-time best shot, but after a 3 year break, I’m a … Continue reading →
Welcome to a journey into our Universe with Dr Dave, amateur astronomer and astrophotographer for over 40 years. Astro-imaging, image processing, space science, solar astronomy and public outreach are some of the stops in this journey!
Ben Backyard Astronomy 