Backyard Astrophoto – Improvements in the Last 10 Years

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.

Messier 101 - Pinwheel Galaxy
Messier 101 – Pinwheel Galaxy (Skywatcher 80ED and Canon 80D)

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).

My results of Messier 101 in 2008

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.

The Great Comet of 2020 That Never Was

Back in March, the astronomy crowd was buzzing about a possible”naked-eye” comet expected in late May 2020.  Comet C/2019 Y4 (ATLAS) was first detected at the tail end of December as a very dim magnitude 19.6 object and by mid-March it had brighten to an easy telescope target magnitude of 8. Those not familiar with the magnitude scale, going from 19.6 to 8 is not a doubling in brightness, but around a 4000 times increase!

That dramatic increase in brightness help fuel the hype for the Great Comet of 2020, and there were two other factors that got people excited:

  1. It would be visible at dusk from the Norther Hemisphere, hence within easy viewing to much of the world population.
  2. It was following a similar orbital path as the “Great Comet of 1843“, suggesting that it was from the same original body and could potentially provide the same viewing spectacle. That 1843 comet was visible in daytime!

Well all that went south when the comet’s breakup was observed in late March after peaking momentarily at magnitude 7. It began to dim, along with any hopes of a Great Comet repeat. Below is a graph showing the the original (grey line) and revised (red) comet brightness forecast (dots being observed measurements) on this chart created by Seiichi Yoshida (comet@aerith.net)

Comet C/2019 Y4 (ATLAS) Brightness - Copyright(C) Seiichi Yoshida

Comet C/2019 Y4 (ATLAS) Brightness – Copyright(C) Seiichi Yoshida

Comet C/2019 Y4 is expected to make its closest approach to the sun on May 31st, however most experts believe it will disappear (disintegrate) before that date.  Seeing that I had a small window of opportunity to capture the comet I decided to try my luck last Saturday evening.

Below is an extremely processed (and ugly) image that I got by combining 25 photos (15 seconds each at ISO 3200) using my Skywatcher 80ED scope. The photo just about makes out the distinctive blue-green hue and elongated shape of a comet. It is around magnitude 10, very diffuse and about 147 million km away from us the day this photo was taken.

Comet C/2019 Y4 (ATLAS) on April 18, 2020 - Very faint at about magnitude 10. Imaged with 80ED telescope 25 x 15sec

Comet C/2019 Y4 (ATLAS) on April 18, 2020 – Very faint at about magnitude 10. Imaged with 80ED telescope 25 x 15sec

I pushed the image processing so hard that I was able to pick up faint magnitude 13 galaxies!

On to the next comet!

Telescope: Skywatcher 80ED
Camera: Canon 80D
Image: 25 x 15sec at ISO3200 (6 minutes)

Field of View Between Two Telescopes

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

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)

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

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…

A Crater Named Tycho

10 Days old Moon (April 04, 2020) - Benoit Guertin

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.

Updated how to process RAW Moon photos

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.

The Sun is Awfully Boring Right Now

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.

Sun on April 4, 2020 with no sunspots.

Skywatcher 80ED, Thousand Oaks Solarite filter, Canon 80D

So far this year we’ve had 70 days without sunspots, that is 74% of the days with no sunspots.  We are at the lowest part of the sun cycle, however things should change soon.

wolfjmms

Maybe by the fall we should have something a little more interesting to look at.

So you have a bunch of Moon shots in RAW. Now what?

UPDATED 07-Apr-2020: Cropping instead of reducing image size


The Moon should be your first target when you start off in astro-photography.  It’s easy to find, does not require dark skies and you don’t need specialized gear.

So now that you’ve found yourself will a bunch of RAW photos of the Moon you’re wondering what to do next.  You took them with the RAW setting right? All astro-photo need to be taken in RAW to conserve as much information as possible because all the processing is done at the pixel-level and you want to retain as much detail as possible.

Registax is a great software for Moon and planetary stacking.  Unfortunately I find it has two drawbacks:

  1. Cannot deal with .CR2 CANON RAW files
  2. Crashes or gives a memory fault when dealing with large images from DSLR.

Luckily there are ways around it… You must be wondering, why use Registax if it can’t deal with large RAW CANON files?  It’s because it can align and stack images by sub-dividing your image to address atmospheric turbulence and it has one of the best wavelet analysis tool to sharpen images.

Here is what you must do: convert your RAW files to 16-bit .TIF and reduce the image size (not just the filesize, but the number of pixels in the image).  I use Digital Photo Professional 4 that came with my CANON camera, it can be downloaded. For other camera brands or photo software should allow you to also convert RAW into TIF format.

There are two possible ways to reduce the image size:

1. Resize the image – this is the fastest and simplest

Highlight the desired RAW files and select File – Batch Process

DDP4 - Main window. Selecting the desired files

DDP4 – Main window. Selecting the desired files

In the Batch Process window select to save the files as 16-bit .TIF and ensure that you resize the images.  Normally 50% reduction will do the trick. In my case a reduction to 3000 x 2000 was sufficient.

DPP4 - Batch process window : Saving as .TIF and Resizing the images

DPP4 – Batch process window : Saving as .TIF and Resizing the images

Resizing will reduce the size of the Moon, and Registax has a better chance of dealing with alignment. It’s also a simple way to reduce noise and improve a less-than-perfect  focused image.

2. Alternatively : Cropping the image – more time consuming

If you don’t want to shrink the image, an alternative is to crop the image. With DPP4 it’s possible to apply the same crop setting to all the images, however it must be done one at a time.

First select one of the images and open the Tool palette.  Select the cropping tool and the area you wish to crop.  Once that is done, use the Copy button in the Tool palette to record your crop setting.

DDP4 - Cropping with the Tool palette

DDP4 – Cropping with the Tool palette

You then need to open each file individually and Paste the crop setting using the Tool palette. Once you’ve done all of that, you can select all your images and run the Batch process to save them to 16-bit .TIF as explained above.  No need to resize if you’ve cropped.

DDP4 - Image selection pane shows the crop box around each image.

DDP4 – Image selection pane shows the crop box around each image.

Now on to alignment and stacking with Registax

Then it’s simply a matter of opening the resulting .TIF images in Registax as you would normally.

moon-raw-3

Once the alignment completed and the images stacked, your photo can be saved

moon-raw-4

But before you close the program, head over to the Wavelet panel and tweak the image to get as much detail out of the moon’s cratered surface.

moon-raw-5

If you compare both images it is clear that the 2nd one has sharper details.

As always, the best is to try different things and experiment with your setup to see what works best.

Equipment used for the above photos:
Canon 80D
Skywatch 80ED (600mm F7.5)
1/250sec ISO 200