January 2022 – IMT3b Observatory

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.

https://twitter.com/metoffice/status/1482538198634876928

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.

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 🙁

The Night Sky Observer Guide Series

When I started attending the Practical Astronomy Show held at Kettering I picked up my first copy of “The Night Sky Observers Guide Volume 4 – The Glories Of The Milky Way to -54°” written by George Robert Kepple and published by Willmann-Bell inc. These were sold at the Kettering show by the very helpful and knowledgeable staff of The Webb Deep-Sky Society for around £20.

Then in December 2019 ‘The Global Human Malware’ happened and the world went nuts, the Astronomy shows were cancelled year on year and I forgot to complete acquiring the rest of the series. Then suddenly in late 2020 it was announced that the publishers Willmann-Bell had closed and their entire portfolio went out of print.

Unfortunately I did not see the announcement until late Jan 2021, however I managed to obtain a copy of “Volume 2 – Spring & Summer” (ISBN 0-943396-60-3 (V2)) from Zoltan at 356 Astronomy but he told me he was out of stock for the rest of the series.

I contacted the Webb Deep-Sky Society to see if they had any available copies in stock. The president of the society Owen Brazell very promptly replied but informed me that they had sold their remaining stock just days before. He was extremely helpful in trying to help me source any remaining stock but eventually to no avail ! I recommend any avid astronomer should consider subscribing to the Webb Deep-Sky Society here …… I just did 🙂

Example of Webb Deep Sky Society Digital Issue

Fast forward to 16th August 2021 and it was announced that the American Astronomical Society would acquire the inventory and related assets of Willmann-Bell. Luckily by January 2022 I noticed that FLO (First Light Optics) in the UK had managed to obtain a few copies and I promptly ordered a copy of “Volume 1 – Autumn & Winter” (ISBN 0-943396-58-1 (V1)) for £35.

Well, it arrived this morning and I apologised to my regular postman for having to carry it around by hand all morning.

As with the other volumes the information, maps, diagrams and descriptions are very useful for planning imaging or observing sessions.

The King of the Northern Winter Constellations – Orion

I now have only Volume 4 “The Southern Skies” left to purchase but as that would only be a reference for objects I can’t see from the UK it would go mostly underused unless I start using my remote telescope account or travel around or below the equator.

I would like to thank Owen Brazell for all his time and for the ongoing activities of the Webb Deep Sky Society and hopefully we will see them at the next Practical Astronomy Show in March 2022 …. fingers crossed !

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.

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.

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.

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.

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.

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.

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.

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?

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.

Below is a copy of the nights weather data.