Detecting pressure waves from the Tonga Eruption (2022/01/15)

On January 15th 2022 at 15:10 AEDT (04:10 GMT) the Hunga Tonga Hunga Ha’apai underwater volcano near Tonga erupted. Hunga Tonga-Hunga Ha’apai is 1.8 kilometres tall and 20 kilometres wide, but most of it is underwater, with the top 100 metres visible above sea level. The pressure wave generated by the explosion blasted through the atmosphere at more than 1000 kilometres per hour.

Dave mentioned to me that the people had registered a pressure increase on their monitoring devices due to the pressure wave and checking the internet the Met Office has issued a nice graph on Twitter.

On the observatory Grafana dashboard I could indeed see two pressure waves at the correct time. We only record the pressure every 60 seconds because for astronomy that’s all we need so we do not have the resolution of others but the height of the two events are in the correct range compared to the graph above.

Double pressure wave

The first pressure wave arrived (19:13-19:24) we was 2hPa increase as we have lost some resolution due to sampling period and the Met Office is ~2.5 hPa. We could change the sampling to be lower (15 or 30 secs) as storage is not an issue and then we would have caught a nice defined peak. The second pressure wave (2022/1/16 01:55-2:14) and we measured ~1hPa drop and again was lower than the Met Office due to our sampling period.

Our auxiliary pressure monitoring install was down during this period as the box appeared to have been restarted/rebooted and the ASCOM Alpaca instance was not running which was unfortunate 🙁

Viewing Report 4th January 2022

17:53 – 02:34

Clear night! So I’m going to setup and let the dome run all night if it stays clear which is the forecast as I have work tomorrow.

All Sky Camera

I have run the guiding assistant on PHD2 so that I can hopefully better track objects. The drift in frames from the last time out whilst using the ST80 as a guide scope was less than ideal. I have now put al the new settings suggested into the PHD setup and have swung round to do a focus run on a star near to M32.

PHD2 new settings

After successfully running autofocus in SGP at 23,560 on Luminance I have now slewed to M32 to gather more data that is desperately needed to resolve the outer spiral arms of the companion giant galaxy M31.

SGP Focus Run

So it is now just gone 9pm and whilst the guiding is managing to stop trailing of stars, the image is moving between frames, enough to loose the object over the course of 4-8 hours. This is clearly not good enough and it does look like the focal length of the ST80 is simply not long enough.

To get around the problem this evening I have turned guiding off, as the exposures are short (3 minutes) the trailing of stars is not an issue. At midnight I took flats for M32. I then centred on M78 for the rest of the night. Before starting I performed another focus run as the focus point had changed over the night with the temperature drop.

Auto Focus

I choose the same exposure settings and Gain 139 and Offset 21 settings as for M32. -25C was the temperature but this time I rotated the camera by 90 degrees to also fit in NGC 27309.

M78 & NGC 27309 and a satellite trail

So I left the scope running and it completed at around 2:30am with 40 frames taken across 4 filters giving me 30 minutes per channel. This will be enough to get started and if clear tonight I will setup for another run at M78 and hopefully improve the guiding.

Update. On reviewing the files this morning it looks like I forgot to select the filter in SGPro which means all my M32 and M78 images from this evening are in fact luminance only! Which is ok for M32 but for M78 I need some colour. Below is the weather data for last night.

Viewing Report 2nd January 2022

19:26 – 01:30

I started with M76 Ha as I need some frame for this object. I already have many hours in OIII. However after starting to image I realised the guiding, which is currently being tested through Dave Boddington’s ST80 was not pointing through the slit correctly as M76 was near the zenith. This means I have suffered from trailing as the guider was trying to guide on long stars due to diffraction.

M76 – 1 x 600s Ha

I swapped to a different object, this time M32 as I have not imaged this directly before, just as a happenstance of imaging M31. I have chosen 180s exposures using Gain 139 Offset 21 to keep the saturation of the core down. At 300s the core was blown out.

M32 – 1 x 300s Lum

M31 can be seen to the left and lower left of the small galaxy. M31 covers a large part of this image! So how well was my guiding doing?

Guiding with the ST80 guider

The guiding looked fine. 0.52 arcsecs total error which I am happy with. I stayed up until just before midnight and then left the observatory running. In the morning I noticed the dome shut around 1:30pm due to the images after that looking like flats.

I also noticed this morning that the images were drifting so the guiding is not quite right as the image drifts. I will next time out run the guiding assistant and see if that helps.

Update the image scrubbed up fairly well but I lost a lot of frames to drift and trailed stars and then the dome closing. Resulting image around 3 hours 12 minutes exposure of which 48 mins was Luminance but there was cloud affecting many frames.

M32 – 3 hours

Below is a copy of the nights weather data.

Cloud cover


Viewing Report 10th December 2021 – IMT3

04:00 – 06:53

Comet C/2021 A1 Leonard. The last day to get this lovely little comet. Dave Boddington had captured a wonderful image yesterday through his 6″ and 4″ refractors. I was was never going to be able to do that with my 5″ refractor due to my broken foot and not being able to move it from the Warm room to the verge on the other side of the lane at the front of my property.

Space boot 🙂

So instead I settled for the good old Canon 6D on a tripod. I had slowly gone up and retrieved the kit the day before in the light and now at 4am set off out the front, crutches in hand, camera on tripod strapped round my neck, in the dark at 1℃.

After getting comfortable standing on the verge, I extended the tripod legs balancing on 1 foot and set the camera on Arcturus to focus at 100mm. I had chosen the 100-300mm lens for maximum flexibility. After achieving focus by hand and by using the zoom function on the camera screen, I placed the camera roughly in the direction of where the comet should appear just below Corona Borealis in the faint constellation of Serpens. This is the shot I got.

Comet C2021 A1 Leonard

I then changed focal length going to 300mm on the zoom lens, switched back to Arcturus to focus and then, after a few attempts, actually some 20 minutes, I managed to get the comet back on the chip. Result!

Comet C2021 A1 Leonard – 300mm

I packed up the tripod, hung it round my neck and headed slowly and gingerly across the lane and back up the drive to the house. When I had removed my one shoe, cleaned my boot and my crutches I looked at the camera lens and was not surprised to see a lens full of dew 🙄

Dew on the lens

I then set about opening the dome of the observatory as the comet would have now cleared the tree line. However it would not open 😳 On closer inspection, meaning I went back out in the cold and up the garden, I found the shutter would not operate. Some time spent investigating led me to believe the battery in the shutter box was dead 🥺 so I removed and took back to the house for further investigation later today. That meant no comet photo through the 12″, however I was pleased with my results given the challenge.

Battery box for shutter

Viewing Report 2nd November 2021 – IMT3

20:00 – 21:30

IC5067 Pelican in OIII and SII, rotated to new angle to allow guide star on West side of the mount. 10 x each channel at 600s and Gain 139 Offset 21, left running and dome shut later in the morning.

Rotation angle 218 from SGPro plate solve, 171.750 from TSX

Flats done the following day 3rd Nov.

Flats darks and darks still to be done

Viewing Report 8th October 2021 – IMT3

22:30 – 03:57

Tonight I am at Kelling Heath star party with Shane and Mark Radice. After a fantastic board game with Mark, Shane and Shane’s wife we then headed back to camp and I started to look through there binoculars using the NSOG (????) book as my guide. Whilst I realised I could have got away with bringing the Milkway edition, instead I brought along the Autumn/Winter version.

I had packed my 100mm Altair Astro binos so it was going to a visual night with some rudimentary drawing. I looked around and set my gaze on Pegasus and turned to the pages in the guide to set me off.

First on the list was M15. It appeared relatively close to

m15 – seen

peg 1 – seen

3 peg – seen

53 peg major seen not companion 

ngc 7217 – not seen

ngc 7331 – seen with averted vision

ngc 7332 – not seen

ngc 7814 – not seen

M39 seen

M42 seen

veil eastern seen

North American seen

tried UHC filter baader from Mark in 1 eyepiece in binos abs made nebula stand out

bed at 3:52am due to fog and 9deg c

looked at M81 and M82 through Keith’s 18”

could not see horse head 

M42 WOW!! and M43 both through 13m Ethos 100 deg and then 21m Ethos

Viewing Report 5th October 2021 – IMT3

19:21 – 21:00

NGC 6765

Focus 18,406

imaged for 1hour 36 mins and then the safety went off and it stopped imaging, no idea if the dome closed at that point or if it just lost a guide star but that was it, despite it being clear all night. So I need to not set the Boltwood OK to image setting in SGPro and I need to find a way of time stamping the dome closure

Viewing Report 1st October 2021 – IMT3


Kelt 16b

Focus 20,329, taken with Luminance filter rather than red

GAIN 75 OFFSET 12 -25℃

Rotator Angle 29.420

Dome stopped at 582 images so need to see how many good ones I got

Clarity got worse from 1:18am until 3:52am when it clouded over, imaging is no good just before 1:15am so mid transit

Observ. Priority: LOW
Total obs. (Recent): 35 (5)
O-C minutes: 0.6±0.21
Alt: 65°
Azi: 228° (SW)
1h Before
Alt: 57°
Azi: 249° (W)
Alt: 45°
Azi: 266° (W)
Alt: 34°
Azi: 280° (W)
Alt: 25°
Azi: 291° (W)
Max counts increase during observationR:0% V:0%
Moon illumination: 22.5%, Moon distance: 126.5°
Observing times [ UTC+1.0 ] and target position
Kelt 16b FoV

Viewing Report 11th September 2021 – IMT3

22:35 – 23:45

Focus position 18464

Temp -25

Gain 139 Offset 21

OIII LRGB 20 x each, 600s on OIII and L and then 300s on RGB

Rotation angle 29.420

NGC 6765 planetary nebula in Lyra

Everything up until 23:45 is Luminance as the filter wheel was not connected correctly in SGPro and it thought it was moving but did not…..

Went to bed

Looks like it clouded over around midnight so a few images only. I also now seem to have a mark on the Luminance filter at the bottom which is a pain, not sure how that got there on a closed system. Also the scope must have moved during the imaging as a few of the images are of a different FoV.

Viewing Report 6th September 2021 – IMT3b

17:35 – 22:15

Opened dome early to cool down, we then had some cloud and it closed, so reopen around 8pm.

As it has been a very warm day, some 28 degrees C and is still 20 degrees, I will set the camera temp to -20 and image a different object to avoid several sets of flats, darks and flat darks. I settled on M56 as I had not imaged this for my Messier catalogue yet.

Loads of problems, mount kept saying it was not unpacked, guider would not connect, so rebooted and all fine.

Imaging at 22:10

Gain 75 Offset 12

Rotation angle 29.420

Temp -22 (need correct Flats/Darks and Dark Flats)

When I rebooted I noticed the PHD2 setting are wrong for the guider so need to change the profile to include DirectGuide not Pulse Guide. Also need to change SGPro so that it does not autofocus at the start of a run, also so it does not set the temp to -15.

Off to bed at 22:15 and left it running.

Everything went well, the dome shut at sunrise and the images look ok, maybe slightly soft focus but only when I process will I be able to tell.

Viewing Report 29th August 2021 – IMT3b

22:00 – xx:xx

Quick look at the Bat nebula given there is a break in the clouds. I had trouble with a guide star due to as hot pixel so I had to move the scope slightly to move the guide star. I need to take a some new darks for the off axis guider.

I tried 2 regions within the Bat nebula given its size, but neither showed any signs of nebula on a single 10min exposure.

I then tried Lynds Dark Nebula, LDN 1082 The Seahorse. |However again due to the expanse of this object a small portion was only available in the 12″ so again this will be more suited to the Esprit.

I then went for Palomar 10, a Globular cluster in Sagtta.

Viewing Report 28th August 2021 – IMT3b

22:14 – 00:52

All Sky Camera

RGB on SH2 – 132.

SH2-132 300s
SH2-132 600s

RGB focus 19,098, Temp -25℃ GAIN 139 OFFSET 21 , Rotator angle 256.020

Changed rotator angle to find guide star, must remember to force a calibration within PHD2 straight after so that the guiding works.


@ 00:45 LRGB on M15.


Lum focus 20,098, RGB focus 19,098, Temp -25℃ GAIN 139 OFFSET 21, Rotator angle 139.520

Left the observatory running at 00:52 and went to bed.

Forgot to set the Very Light safety limit so dome did not close when the Sun came up……

Weather report for the night
Temperature from the night

Need to do flats!!

Viewing Report 27th August 2021 – IMT3b

22:00 – 04:00

Warm room Log Cabin Construction

After a long day of building the new astronomy building with a few friends, I opened the dome on this clear night and start off by imaging SH2 132 until midnight for which I grabbed 18 x 600s Ha images at Gain 139 Offset 21 and temp of -25 deg C. I then switched to SH2 183 and went to bed.

All Sky Camera

On waking this morning I realised I got 22 x 600s Ha images at Gain 139 Offset 21 and temp -25 deg c before the clouds rolled in ands the dome shut around 4am. The seeing was particularly good as can be seen from the satellite image from skippy

Viewing Report 24th August 2021 – IMT3b

21:22 – 03:50

Another clear night whilst I am on holiday and after a long day of building the new warm room for my astronomy hobby. I finally got the camera imaging some more 600s Ha frames of the Sharpless 132 emission nebula in Cepheus (11 subs). The challenge was SGPro misbehaving and not plate solving. I used Gingergeek to look at it but he could not work out the problem either. So I used TSX to slew and solve instead before heading back into SGPro to start capturing data. I ran a set of Ha Flats before I moved to the next object at Rotator Angle 256.020, focus position 18500.

I then moved to SH2 183 another emission nebula in Cepheus. I let this running for the rest of the night whilst I went to bed at 00:47 during which time it took 19 images until more cloud lost the guide star which I need to fix so it restarts automatically.

I also worked out that plate solving was an SGPro bug as restarting SGPro allowed the plate solving to start working again, so useful for next time.

Observing conditions check. This morning I reviewed the environmental data and the conditions were fairly poor so I will redo the data. The Moon was just past full. The ASC video shows wispy cloud all night. The sky temperature was bumping around -13-14 degrees all night where -18 degrees is considered clear.

1st Exoclock Conference & IMT3b

25/09 AM – Exoclock Video Conference Day 1

So I had planned to sit in on the Exoclock Annual meeting all day for both days but in the end I could only attend for the pre-lunch meetings as I had promised Dave that I would assist at the IMT3b observatory. So I will catch up on the afternoon talks when they are made available online.

The talks were varied and included experts from the Ariel Mission, Twinkle Mission, JPL, Telescope Live, BAA , members of the Exoclock project followed by workshops of which again I really wanted to be present to participate in the CMOS workshop but I couldn’t.

1st Exoclock Annual Meeting Agenda

25/09 PM – IMT3b Warm Room & Donkey Work

We shutdown the dome computers, network and whilst Bob started on the warm room electrics Dave and I proceeded to 1 ton of scalpings from the front of the house into wheelbarrows and then push them up the garden to be stored ready for the warm room patio construction. It was a very humid day and we were both sweating heavily by the end of it.

The dome computers were repowered and outstanding software updates applied (BIOS, Windows updates, windows software and RPi4 OS & software) before the Autumn imaging sessions begin in earnest.

The day was rounded off by relaxing with a glass of red wine and dinner with Bob, Dave and the family. As the evening turned out to be cloudy there would be no imaging so it was an early night ready for the hard graft on the following afternoon.

26/09 AM – Exoclock Video Conference Day 2

Another set of fine talks and I especially thought it was a nice touch that an artist Lea who won the new Exoclock Logo Competition was awarded some imaging time on Telescope Live.

Lea took a bit a time explaining her background and how she formulated the design for the new logo.

New logo courtesy of Lea Changeat

It was even better that not being an astronomer she was persuaded to undertake some Exoplanet observations and report on her experience.

26/09 PM – IMT3b Warm Room Windows

The 7ft double glazed windows were put by Dave, Luke and Tim and myself. It was nerve racking as we manhandled the two panes from near the side of the main house up steps and along the garden with the Tim and Luke taking the awkward window corners whilst Dave and I used floor tile clamps on the glass.

The warm room aka “Wooden GreenHouse”

Bob came over to complete the electrics for the warm room and I left when Dave started stretching on tiptoes to put in the red & white light fittings. I figured I could complete the remaining software updates remotely.

The AAG software was updated to 9.1.4 from the old 8.1.0 version, we still need to investigate the wind sensor reading with Jamie from AAG.

AAG 8.1.0 sensor limits
AAG 9.1.4 sensor limits and new sensors

So we now access to the Humidity sensor settings and the appropriate alert levels. Previously I had to rely on both ASCOM local conditions and internal dome humidity via ASCOM (BlueAstro StickStation) but I wonder if we want to trigger an unsafe state by including the humidity thresholds.