The Great Comet of 2020 That Never Was

Posted on April 19, 2020 by Benoit Guertin

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:

It would be visible at dusk from the Norther Hemisphere, hence within easy viewing to much of the world population.
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 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

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

Posted on April 18, 2020 by Benoit Guertin

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…

A Crater Named Tycho

Posted on April 7, 2020 by 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

Posted on April 7, 2020 by Benoit Guertin

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

Posted on April 4, 2020 by Benoit Guertin

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.

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.

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