When I first started astro-photography you had people like me who were just starting off and did it on the cheap with a webcam, a small newton telescope and basic mount, or you could fork out an astronomical amount of cash to get really specialized gear.
Below is a photo of Messier 101 the Pinwheel Galaxy taken last week with a $500 Skywatcher80ED telescope and Canon80D DSLR on an unguided mount.
I agree that it’s not as fancy as some of the research grade setups or some other hobbyist out there, but it’s many times better than my first try in 2008 (below).
What has changed? Well for starters the optical quality of beginner and intermediate telescopes has dramatically improved, largely thanks to automated and computerized lens and mirror shaping and polishing. Yes they are made in China, but so are most carbon-fiber bikes and the latest smart-phones. As the process is automated, quality can be tightly controlled and the results are hard to beat. A quality image starts by being able to collect and focus light properly, and for $500 you can get some really descent optics.
Another great boost is improvements in camera sensors. DSLR became a go-to solution because it was a cheap way of getting a large sensor with low read noise and good sensitivity. Of course there are still monochrome specialized astro-gear available for backyard astronomers, but the one-shot color results of a DSLR are hard to match. DSLRs offer ease of use, compatibility with most software and are the biggest bang-for-your-dollar compared to specialized astro-cameras.
And the third major improvement in 10 years is computing power. A night imaging session can easily generate 1GB of RAW images that need to be processed. Transferring and storing data is now cheap, and software has followed in lock-step to handle the increase in image size and quantity. Registering and stacking software can easily handle at the pixel-level hundreds of images each with millions of pixels. Sure it might take 20 minutes to process 120 photos from the DSLR, but that is a far cry from the hours of computer crunching. If your parameters were wrong, you just wasted a hour….
So while light pollution is choking the stars out of the night sky, one easy way to gain access to the universe is through astro-photography. It’s now easier and cheaper than ever to get good results with a simple setup.
I have two telescopes, a Skywatcher 80ED (identical to the Orion 80ED – 600mm focal length at F7.5) and a Williams Optics Gran Turismo 71 APO with 420mm focal length at F5.9. Just looking at the numbers it’s easy to see that the GT71 is a smaller and faster telescope, and because of the shorter focal length it should have a larger field of view.
Comparing size with Skywatcher 80ED
Now I’ve photographed the same part of the sky with both telescopes, and can now overlap the images to see exactly what is the difference between the field of view between these two telescopes.
First I need to say that that GT71 NEEDS a field flattener when imaging with DSLR. The distortions off-center are terrible. Don’t get me wrong, as a three objective lens telescope (including 1 fluorite for color correction), it has provided me with the best lunar photos, however it has issues when using the large DSLR sensor. The SW80ED provides a much flatter field of view for photography out of the box.
The flattener for GT71 is in the plans…
So how does both telescope compare? Below is a photo of open star cluster Messier 38 taken with my GT71 and I’ve overlapped as a brighter box an image taken with the SW80. For those wondering, I used IRIS to register and align both photos using the coregister command.
Messier 38 – Field of view with William Option GT71 and Skywatcher 80ED (brighter box)
Both telescopes deliver just about the same field of view with the GT71 providing 1 degree more of horizontal field. But the difference is much less on the vertical.
What did surprise me is how much light the GT71 gathers. Inspecting the photos showed me that even with the smaller setup, the GT71 has great light gathering capabilities. I got down into magnitude 12 with only 15 seconds of exposure, which is nearly similar to the SW80ED at 30 seconds.
WO GT71 vs SW80ED Optics
In conclusion I would say the GT71 has good photographic potential, but requires a field flattener if it will be used with DSLR. Stay tuned…
10 Days old Moon (April 04, 2020) – Benoit Guertin
The photo above is of a 10-day old Moon taken a few days ago. After the darker “seas” of old lava flow, one particularly bright crater in the southern hemisphere stands out, especially with the rays that appear to emanate from it. That is Tycho, a 85km wide and 5km deep crater and one of the more “recent” ones if you consider 109 million years the not-to-distant past. The Moon is 4.5 billion years old after all… having formed just 60 million years after the solar system. On the Moon, “fresh” material have a higher albedo and hence appear brighter, whiter.
The bright rays surrounding Tycho are made of material ejected (up to 1500km away) from the impact of a 8-10km wide body. In time these rays will disappear as the Moon continues to be bombarded by micro meteorites, which stirs the material on the surface. The rays are more present on the eastern side, as would be expected from a oblique impact.
Tycho is names after the Danish astronomer Tycho Brahe.
The Surveyor 7 space craft landed about 25km north of the crater on January 10, 1968.
Ever wondered how mosaic space photos were done before the invention of powerful software algorithm to stitch them together? Take a look at the series of Surveyor 7 mosaic photos. Someone had to painfully print each photo and lay them on a grid in a specific pattern matching optical field and geometry.
When I initially wrote the article on dealing with Canon RAW files in Registax, I mentioned to resize the image when converting to 16-bit .TIF format. However that is not ideal if you want to keep your target object the same size. Playing around with the Canon Digital Photo Professional 4 software I found out that it’s possible to apply the same cropping parameters to each photo, and when batch processed, they get all cropped. Therefore I’ve updated the article to now include the steps to crop instead of resizing to have images small enough for Registax to process it while retaining the original photo resolution.
Most of the world is self-isolating to reduce the spread of COVID-19, and we can’t even keep ourselves busy with daytime sunspot observations. The sun is completely free of any spots. Below is an image taken on April 4th.
Shooting wide angle long exposures of the sky is always fun, because you never quite know what you will get. On an August night I decided to take a few 20 seconds exposures of the constellation Perseus hoping to catch a few open clusters. However got surprised by the faint glow of Messier 33 (Triangulum Galaxy) in the photos. This is the furthest object that can be observed to the naked eye, located 2.7 million light years away, and part of the Local Group which includes Andromeda and our Milky Way.
Constellations Perseus and Triangulum (Benoit Guertin) – CLICK FOR FULL SCREEN
4 x 20 seconds
August 30, 2019
Most people don’t plan to take photos of the Moon, they just happen. You are outside doing something else and then you spot it over the horizon or high in the sky: “Hey that’s a pretty Moon tonight Maybe I should take a photo!”
I find that normal camera lens, even telephoto don’t do it justice. The setting and focus can be very tricky. The multi-lens setup of telephoto can also cause internal reflections or chromatic aberrations making the resulting photo less appealing.
So just grab the telescope tube and leave the tripod behind. If you have a small APO refractor you can simply hold the tube, but for anything heavier you’ll need to prop yourself up on something like a railing or a car roof.
The photo below is a single shot at 1/250sec and ISO400 with Canon 80D and William Optics Gran Turismo 71 held on the end of my arms.
80% Illuminated Moon on August 31, 2018 [Benoit Guertin]
The setup takes only a few minutes and the results are always worth it.
A few weeks ago after taking some photos of Jupiter, I changed my setup to do some long exposures on an easy target: a globular cluster. Unfortunately I forgot to note down the name of what I had photographed! So a few weeks later when I found the time to process the images I was at a loss to identify what Messier object it was. However, after an evening of matching up stars surrounding the cluster and I was able to correctly identify it as Messier 3.
Globular Cluster – Messier 3 (Benoit Guertin)
The above was taken with my Skywatcher 80ED and Canon 80D. It is a stack of 27 x 10sec exposures at ISO3200 on an unguided and roughly aligned mount.
Looking at my archives I found that I had imaged M3 about 10 years ago with the same telescope, so I decided to align both old and new image and see if anything would stand out. And to my surprise, spotted one star that appeared to have shifted. To help identify the star I colorized one of the photos and subtracted from the other (done in GIMP). All the stars within the field of view lined up except this one; the two colored spots are not aligned!
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!