Archive for the ‘Astronomy’ Category

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Old photos of the 2001 Leonids from Malalla

January 3, 2019

I was looking through a bunch of old photos and slides today and came across these star-trailed pictures (film-based) I took of the 2001 Leonid meteor shower from Malalla, South Australia:

Star trailed images taken with a tripod-mounted Pentax K100D

Meteors radiate outward from a point in the sky in the constellation Leo (called the radiant) since the Earth is ploughing into left over sublimated material from comet Temple-Tuttle in that direction.

My father and I stayed up until the wee hours watching the meteors come thick and fast. I have good memories of that evening spent with dad. After he’d had enough, I stayed up to watch them until the sun came up.

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July 2018 Lunar Eclipse from Adelaide

July 28, 2018

Apart from the “getting up at 4:15am” part, the total lunar eclipse on Saturday morning (July 28) was very enjoyable.

MidTotality

Luna 1 minute after maximum totality (f2.0, ISO 200, 1 sec). For reference, the right-most star is rho Capricorni, a double with a brightest component of magnitude 4.8.

I took a little over 200 images from our backyard starting a few minutes before totality began at 5am ACST until just after the end of totality at around 6:45am.

I also looked at the Moon through 7×50 binoculars from time to time, from which the impression of the Moon as a 3D ball of rock hanging in the sky was evident.

I had initially planned to use my 8″ telescope for imaging as well, but in the end, was happy with to take wide field shots, so left the scope inside.

All images were taken with a tripod-mounted Canon 1100D and 100mm fixed lens controlled using Canon EOS Utilities.

EclipseMontage

A montage showing Luna 5 minutes before the start of totality (f2.0, ISO 400, 1/8 sec), 1 minute after maximum totality (f2.0, ISO 200, 1 sec), and 9 minutes before the end of totality (f2.0, ISO 200, 1 sec).

Along with most images I’ve seen, these present a vividness not evident only by eye. The following images are perhaps closer to what was seen without aid of imaging equipment.

MarsMoonTotality2

Moon and Mars 20 minutes before the end of totality (f2.8, ISO 200, 1 second).

MoonLowOnHorizonJustBeforeEndOfTotality

The Moon and Mars 8 minutes after the end of totality (f2.0, ISO 100, 1/10 sec), just above our SW fence line.

The final image shows an incidental image of the International Space Station passing “near” our lemon tree when I noticed it passing above the Moon.

ISS

ISS trail (f2.0, ISO 100, 1.3 sec)

At least one image of the eclipsed Moon also ended up with a “stray” satellite in the field.

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Nova Carina 2018 update #2

March 27, 2018

Shortly after my last post I observed the nova again. Within 24 hours it has dropped by a full magnitude after peaking at 5.7, a little higher than my binocular estimate of 5.8 from last night.

My two observations are in purple, as usual, with the observation an hour ago under the cross-hairs.

ASASSN-18fv-2018-03-27

 

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Nova Carina 2018 update

March 27, 2018

A “happy snap” (with iPhone) of the sky over my backyard rooftop, with Luna peeping through cloud. The nova’s location is behind me from this vantage point.

After being away for a week and a cloudy sky on Sunday, I caught my first glimpse of Nova Carinae 2018 (ASASSN-18fv) in 7×50 binoculars minutes before the sky started clouding out.

I estimated it to be 5.8 (purple, at top right) at just after 11pm Adelaide time.

Note also the upward trend-line.

I had hoped to subsequently image the nova to carry out DSLR photometry for better accuracy but that didn’t pan out due to cloud.

At the time of submission to AAVSO the last observation before mine was 6.5, several hours earlier. Since then, others have submitted observations up to 5.9. So, I appear to have caught Nova Car 2018 on the rise and at its peak so far.

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Nova in Carina

March 23, 2018

Nova Car 2018 or ASASSN-18fv was discovered by the ASAS Supernova network on March 21st and has so far reached around magnitude 6.5 from a progenitor magnitude of 19.9 within a couple of days.

Below is a Stellarium view of the location of ASASSN-18fv, very close to the 5.1 magnitude comparison star near the Eta Carina nebula and star, a variable whose brightness I often estimate.

A binocular finder chart with a slightly different orientation from the Stellarium screenshot is shown below:

This is a crowded area of the sky, and being so close to the 5.1 star, it may be tricky in a low power binocular field.

Rob Kaufman posted this image of the nova, with yet another different orientation:

asassn-18fv2c202120mar20201820text2030-sec

I have not yet had the opportunity to observe the nova; hopefully in a couple of days.

The AAVSO alert notice has more details.

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Nova Cir 2018 Gamma-ray Space Telescope observations

February 3, 2018

AAVSO alert notice 613 for the nova in Circinus requests visual, DSLR, CCD and spectroscopic observations, with multiple observations each night if possible, in support of the Fermi Gamma-ray Space Telescope’s observations that are currently underway:

 

spacecraft

Source: https://fermi.gsfc.nasa.gov/inc/img/spacecraft.jpg

Target-of-opportunity observations requested by Dr. Mukai are taking place now through February 6 UT with the NASA Fermi Gamma-ray Space Telescope. To support these observations, observers are asked to make several observations per night.

I’m processing DSLR observations of the nova from last night and plan to continue observing over the next few nights. Its visual magnitude is currently at around 7.2.

Here’s a spectrum taken by Rob Kaufman on January 31:

ncir201820spectrum2c203120jan2020182c2012-5420ut20text

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Total Lunar Eclipse from Adelaide

February 1, 2018

Adelaide was largely clouded out for the eclipse but the cloud thinned at times well enough to get some reasonable images, especially after midnight. Taking more than 100 images also helped.

I used a Canon 1100D at the prime focus of my 8″ Schmidt-Cassegrain Alt-Az (Meade LX-90) telescope.

Here are some images I thought were interesting enough to show. These are straight off the camera with no processing except RAW to JPEG conversion.

IMG_0013-low

Pre-totality umbral shadow through cloud. ISO 100, 1/10 second.

IMG_0064-low

Totality. ISO 800, 2 seconds.

IMG_0006-low

Not long before end of totality. ISO 800, 2 seconds.

IMG_0027-low

Soon after end of totality. ISO 800, 1 second.

 

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Nova Cir 2018

January 28, 2018

In my last post on January 20 about Nova Mus 2018, I said that another southern nova had been discovered, this one by John Seach in the early hours of January 19 in the constellation of Circinus, near alpha and beta Centauri. That post also showed a Stellarium context screenshot and pointed to an AAVSO finder chart.

This nova has slowly been on the rise for the last several days from around magnitude 8.5 to 6.3 by January 27.

The following 15 second DSLR images I took on Jan 22, 23, 26 and 27 show the nova brightening over time:

NovaCir2018Panels

If the images seem out of focus, that’s because they are. They were used for photometry rather than with the intention of being pretty; use of defocus is part of the procedure. See this talk I gave about DSLR photometry in 2015 for more detail. There’s some positional differences between frames, reflecting the difference in observation time from night to night.

The light curve below shows visual, Johnson V, and Tri-Color Green (DSLR) observations from January 19 to 28; mine are in purple. I’ve also submitted observations in blue and red bands.

NovaCir2018LCJan28

This light curve doesn’t appear to show a simple linear increase, so it will be interesting to see where the rise stops.

Rob Kaufman (discoverer of Nova Mus 2018) said that a low resolution spectrum he took on January 26 was essentially featureless.

The sky is largely clouded out tonight here in Adelaide at the end of a hot day (42° C), but I just caught a quick glimpse of the nova in 7×50 binoculars, but wasn’t able to check against comparison stars. It’s around the same magnitude as last night though. I’ll carry out more DSLR photometry as soon as I can.

In the meantime I have two more nights of Nova Mus 2018 (currently on the decline) DSLR images to process. I’ll write an update post for that nova too.

 

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Nova Musca update (and another one)

January 20, 2018

It’s been several days since the nova in Musca was found by Rob Kaufman. The alert notice was sent out by AAVSO on January 16.

Below is the green filter channel of a DSLR image I took around midnight on January 17. The nova is shown via red markers with a faint satellite trail at upper right. Compare this with the narrow field Stellarium screenshot in my last post.

img-g13-cropped-annotated

That was one of 20 images used for photometry of the nova that night. I’ve repeated this on two other nights since submitting untransformed green (visual wavelength), blue and red band observations.

My visual band (binocular and DSLR photometry) observations are shown below in purple alongside visual band contributions from others:

NovaMusca2018Jan20

A polynomial fit makes the emerging pattern a little more obvious (if exaggerated in parts); up and down from night to night as is common with novae.

NovaMusca2018

This morning another southern nova was discovered in the constellation Circinus (near Alpha Centauri) by John Seach in NSW at magnitude 9.1. John also discovered a bright nova in Centaurus in 2013. I have not been able to observe this yet due to cloudy conditions tonight.

Here’s a Stellarium screenshot of this latest nova’s location:

Nova Circinus 2018

The AAVSO finder chart I will be using initially is this:

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Nova near Southern Cross

January 15, 2018

Rob Kaufman in Victoria discovered a possible nova (PNV J11261220-6531086) near the Southern Cross (Crux) in the constellation of Musca on January 14 2018. All novae start out having the designation PNV or possible nova.

Rob’s discovery visual estimate was magnitude 7. I estimated it tonight with 7×50 binoculars at magnitude 6.7 relative to magnitude 6.4 and 7.1 comparison stars.

This context screenshot from Stellarium shows the nova’s location (cross-hairs at upper middle of image) relative to familiar stellar sign posts, including Crux and Alpha Muscae at 10pm Adelaide time (AEDT).
PNV J11261220-6531086 wide

The next shows a narrower field of view with the nova at right of the helpful triangular, A-shaped asterism.

PNV J11261220-6531086 narrow

Here’s a 10º finder chart from AAVSO
X22594EOand an 8º finder chart with the orientation closer to that of the sky around tonight’s observation time. The two comparison stars I used are circled in red.

X22594EI

After submitting my observation tonight to AAVSO I noticed that since Rob’s discovery observation, only two have been submitted other than mine:

  • another visual estimate by Sebastian Otero in Argentina (6.85);
  • and a tri-colour green DSLR observation (6.72) by David Blane in South Africa.

What I love about such transients, is their spectacular brightness rise and unpredictability.

Initial spectroscopy by Rob indicates a classical nova. I’d expect to see more amateur spectroscopy of this object in the near future.

Will it become visible to the naked eye like the similarly southern and close-to-Crux V1369 Cen did in 2013 (peaking at around magnitude 3.4)? One never knows with these things but it’s worth noting, as per the CBAT transient report page, ASAS-SN observations suggest the nova may actually have started in the first few days of January. If so, perhaps we’re a little too far down the track to expect naked eye visibility. All we can do is to observe it and see!

Being such a southerly object, it will not be as well observed as novae in the northern hemisphere, but it’s in a great location, so have a go if you can! I’ll be out every clear night observing it when I can in the days to come, visually and possibly via DSLR.

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