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View from the high ground August 29, 2021: Hurricane Ida

2021 August 29
by Russ

This recent imagery from NOAA’s GOES-East satellite shows Hurricane Ida coming ashore in southern Louisiana.  The GOES-East satellite is parked in a geostationary orbit  22,000 miles (36,000 km) overhead. You can find the most current GOES-East imagery here.   Track GOES-East (aka GOES-16) here.

Jupiter July 4, 2021

2021 July 6

09:37:37 UT

09:50:34

10:01:37 UT

Jupiter was well placed in the pre-dawn morning sky of July 4th.  It was nearly due south, approaching the celestial meridian, and 42° above the horizon.  

I got the C8 rig powered up and Jupiter focused on the imaging chip around 04:30 a.m. (09:30 UT). It was still dark. The sky was clear.

I started capturing video right away and kept going until around 05:05 when I noticed it was becoming more difficult to keep the image histogram level at 60%-70%. I kept increasing exposure lengths and gain levels, but Jupiter’s image kept getting fainter. Finally, I looked up at the sky. Clouds!

It was now overcast from horizon to horizon. Jupiter, usually very bright and visible to the unaided eye, was only faintly visible as a pale dot through the clouds.  The imaging session only lasted a little over a half an hour.

At the start of the brief session, the Great Red Spot was not visible, having just rotated out of view on Jupiter’s preceding limb. And, The feature known as Oval BA had not yet rotated into view on Jupiter’s following limb. As usual, my timing was not good. I managed to miss both.

So, what we’re looking at here are Jupiter’s belts and zones. While there are no big dramatic features to see, the seeing was good enough for my small rig to resolve some detail in the belts, and to resolve two small white ovals in the south polar region. These two ovals are the leading end of a string of ovals that precede the much larger Oval BA, which I should have captured if he clouds hadn’t intervened.

Good seeing is relative though. On the imaging scale devised by world-renowned planetary imager Damian Peach, the seeing only rated a “fair” grade.  According to the Peach scale, fair seeing  shows: “Significant fuzziness or undulation. Fair contrast. Larger scale detail well seen. Minor details mostly invisible.”

As this short video snippet shows, the seeing during this session falls squarely into Peach’s “fair”

This video snippet, captured on July 4, 2021, shows a fuzzy, quivering image of the giant planet Jupiter. The atmospheric seeing conditions would probably be rated as fair on Damian Peach’s seeing scale. Contrast is good. Large scale features are visible. Some smaller scale features are occasionally seen, but mostly not.

category. By Oklahoma standards though, the seeing rarely rises even to this level. Compared to the usual blurry soup the sky serves up here, this session’s seeing might be rated “good.” Oklahoma’s flat midcontinent location, with its near-constant surface winds and turbulent jetstream overhead, puts us under a roiling ocean of air that causes the planets to shimmy and dance when they should be holding still for the camera. As a result, here in Oklahoma, when Jupiter holds still enough  to show good contrast and some large scale detail, fair seeing is really good seeing.

Notes:

Date: July 4, 2021
Telescope: Celestron C8 (203mm F10) and Orion Shorty 2x Barlow
Camera: ZWO ASI224MC
Captured in FireCapture. Aligned and stacked in AutoStakkert. Wavelets and color balance in Registax. Color levels, unsharp mask, crop, in GIMP.

[1] 09:37:37 UT    800/3703 frames, 53 fps,  15.7 ms.
[2] 09:50:34 UT   2000/3824 frames, 55 fps, 14.26 ms.
[3] 10:01:37 UT   2000/6663 frames, 69 fps, 14.26 ms.

Jupiter Season 2021 Begins

2021 July 1
by Russ

09:31:47 UT

10:08:07 UT

10:30:19 UT

The Jupiter observing season for 2021 began for me in the pre-dawn early morning of June 19th.

When I finally landed Jupiter on the camera’s imaging chip and brought the view into focus, I was pleasantly surprised to see that the Great Red Spot was visible and, as an added bonus, a shadow transit by Jupiter’s moon Ganymede was in progress.

The first image (top left) shows the black dot of Ganymede’s shadow already having transited across two-thirds of Jupiter’s disc when I started imaging. Ganymede itself is just outside the field of view to the left.

In the second image (middle left), taken a little over thirty minutes later, Ganymede’s shadow has moved close to Jupiter’s limb, and Ganymede is just entering the field of view along the upper left edge of the image. At this point, with the transit nearing its end, Ganymede’s shadow is no longer a round dot, but appears as an elongated egg shape. This is because the shadow is no longer being cast on Jupiter’s relatively flat disc, but instead is being cast on the curved edge of Jupiter’s limb.

In the final image (bottom left), captured an hour after the first, Ganymede has moved further into the image but its shadow has now slipped off Jupiter’s face, being cast into empty space. The transit is now over.   

The seeing conditions during this session were mostly poor, but occasionally rose to fair/average. Luckily, I captured some video sequences during these brief periods of improved seeing and was able to cull enough good frames from each video to create these images.

Notes:

Date: June 19, 2021
Telescope: Celestron C8 (203mm F10) and Orion Shorty 2x Barlow
Camera: ZWO ASI224MC
Captured in FireCapture. Aligned and stacked in AutoStakkert. Wavelets and color balance in Registax. Color levels, unsharp mask, crop, in GIMP.

[1] 09:31:47 UT 1800/5317 frames,  48fps,  13.91 ms.
[2] 10:08:07 UT  2000/5407 frames, 56 fps, 11.45 ms.
[3] 10:30:19 UT  2000/5595  frames, 97 fps, 10.22 ms.

 

Comet C/2020 T2 Palomar June 15-16, 2021

2021 June 30
by Russ

Comet C/2020 T2 (Palomar) moving through the constellation Bootes on the night of June 15, 2021. The animation covers a period of approximately 45 minutes. At the time these images were captured, the comet was moving across the sky at approximately 4 arcminutes per hour. The field of view is 13×10 arcminutes. North is up. East is left. More details below.

Comet C/2020 T2 (Palomar) was in the southwestern sky in June.  I was able to image it late in the evening of June 15th and into the early morning of June 16th.

This animated image shows C/2020 T2 Palomar as it crawled through a rather barren area in the constellation Bootes southwest of the bright star Arcturus.

If you notice a slight brightening of the background in the lower right quarter of the animation (southwest quadrant), you are seeing noise creep into the telescope’s field of view from a nearby crescent moon.  When these images were taken, the Moon was only five fist widths (50 degrees) southwest of the comet.  

During this pass through the inner solar system, C/2020 T2 (Palomar) isn’t showing a tail. All we can see of the comet is its coma, the diffuse cloud of gas and dust that enshrouds its tiny nucleus and keeps it hidden from view.

At the time of this image, the night of June 15-16, the comet’s brightness was being reported by various observers around the world as magnitude 10.5. This is approximately sixty times fainter than a bare eyeball can see from an extremely dark observing location.

Comet C/2020 T2 (Palomar) made its closest approach to Earth on May 12th, and will reach perihelion, closest approach to the Sun, on July 11th. After passing perihelion, the comet will recede from the Sun out into more distant areas of the solar system, well past the orbit of Pluto.

Note:

This animated sequence was captured with a Celestron C8 telescope (203mm f/10) and  F0.63 focal reducer, using a ZWO ASI224MC camera. Each of the eight images in the sequence is made up of a stack 10-23 sub-images, each exposed for 20-30 seconds.  The sequence was captured, live-stacked, and live-processed using SharpCap. The animation was created using GIMP.

 

 

A Two Comet Night as a Lesson in Air Temperature and Humidity

2021 January 8

Three nights ago on January 5th, I caught two comets in one imaging session. The first, Comet 156P/Russell-LINEAR, was in the constellation Triangulum. The second, Comet 398P/Boattini, was in the constellation Orion.

Comet 156P/Russell-LINEAR

Comet 156P/Russell-LINEAR on January 5, 2021, 02:54-03:26 UT. At the time of this 30-minute animated sequence, the comet was 78 million miles away from Earth and heading just beyond the orbit of Jupiter where it will turn around to make another inbound pass through the inner solar system. With an orbital period of 6.4 years, Comet 156P/Russell-LINEAR should be back this way in 2026. In this image north is up and east is left. The field of view is 16’x12.’ [1]

Both comets were in the sweet zone for my telescope and camera combination. I estimated Comet Russell-LINEAR at magnitude 12.3 and Comet Boattini at magnitude 12.8. These magnitudes are 300 times fainter than the faintest celestial object that can be seen by a pair of very good eyes from a very dark location.

On the images posted here Comet Boattini is noticeably fainter than Comet Russell-LINEAR. Both were captured using similar exposure times and gain settings. Under these circumstances, they should appear of similar brightness. At the time, however, I was imaging Comet Boattini in comfort from inside my warm house, and failed to notice that the outside air temperature and the dew point temperature were converging near 31° F. This was serious negligence.

I didn’t realize anything was amiss until I moved on from Comet Boattini to my next target, the Pinwheel Galaxy (M101) in Ursa Major. This large galaxy fills the whole field of view of my imaging set up, but no matter how I worked the camera controls, I just couldn’t get anything better than a pale noisy ghostlike pinwheel to show up on the monitor.

Comet 386P/Boattini

Comet 398P/Boattini on January 5, 2021 06:39-07:19 UT. At the time of this 38-minute animated sequence the comet was 38 million miles away from Earth and heading outbound to somewhere between the orbits of Mars and Jupiter where it will turn around and head back toward the inner solar system. With an orbital period of 5.5 years, Comet 398P/Boattini should be back in our neighborhood in 2025. In this image north is up and east is left. The field of view is 17’x13’. [2]

Thinking that clouds had rolled in, I went outside to check. No, the sky was still beautifully clear. But upon reaching the telescope rig in the back yard the situation became apparent. The entire rig was covered in thick crystalline icy frost. Even the foam dew shield over the front of the telescope was covered with the stuff.

After removing the dew shield the source of the problem became even more painfully obvious. The corrector plate, the large flat glass lens that covers the front end of my Schmidt-Cassegrain telescope, was completely frosted over like a heavily frosted car windshield on a cold winter morning.

Needless to say, this ended the session. But, although I was tempted, I didn’t take an ice scraper to the corrector plate.

Temp-Dew Point Graph

This graph shows air temperature and dew point temperature from my back yard weather station on January 4-5, 2021. The area inside the red circle encompasses the time from midnight on the night of the 4th through approximately 01:30 a.m. on the morning of the 5th. This was when I was observing Comet 398P/Boattini. During this time the air temperature dropped below freezing, hovering around 31° F and the dew point temperature hung around 29° F. This temperature differential put the relative humidity in the 85%-89% range, a fraught range for astronomical imaging. With the air temperature and dew point temperature within two degrees of each other, moisture condenses out of the air to form heavy dew on all exposed surfaces, especially telescopes and their optical components. But in this case the situation was made worse by the subfreezing temperatures causing the liquid condensate to freeze as frost. This was the death knell for what started out to be a promising observing-imaging session.

I didn’t realize it at the time, but the frosting event had already started while I was imaging Comet Boattini. This explains why Comet Boattini is fainter than Russell-LINEAR in these images despite both being at nearly the same visual magnitude.

Nevertheless, the dew shield did its job. It delayed the inevitable onset of frozen dew collecting on the optics, but it obviously was overcome by the onslaught of humidity and below-freezing temperatures and succumbed.

Having once again learned a lesson about humidity, temperature, and telescope optics I now have a telescope dew heater on order and am anxiously awaiting its arrival! There are a few months of winter left. I don’t want to get frosted again.

Notes:

[1] This animated sequence was captured with a Celestron C8 telescope (203mm f/10) operating at f/5 with a ZWO ASI224MC camera. Each of the eleven images in the sequence is made up of a stack 11-13 sub-images, or frames, each exposed for 15 seconds.

[2] This  animated sequence was captured with the same equipment described in note 1. The sequence is made up of nine images, each of which consists of a stack of 11-13 frames, each exposed for 15 seconds.