Archive for the ‘Variable Stars’ Category

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:




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:


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:


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.


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.


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.


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:


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.


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:

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.


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.

Nova Interruptus

June 23, 2017


I like to call this wide field (12 x 8 degrees) image, taken with a Canon 1100D (ISO 100, f2.0 100mm), nova interruptus. 🙂

The red arrow points to ASASSN-17gk (shown in inset), an 11th magnitude nova in Centaurus I observed on May 21. It also shows the trail left by a passenger airliner as it moved from top left to lower right during the one minute exposure, with tree-tops at bottom.

ASASSN-17gk visual band

The signal to noise ratio wasn’t high enough to get a good value and error for the nova’s magnitude via DSLR photometry, so I didn’t submit an observation. The light curve at left shows observations made by others and the polynomial fit below highlights the rough shape of the light curve.

ASASSN-17gk visual polyfit

HD 148703

June 12, 2017

A request for observations by astronomers at the University of Wroclaw in Poland was announced by AAVSO on June 8.

The bright (magnitude 4.23 V) long period eclipsing binary HD 148703 (aka N Sco, HR 6143) is expected to undergo primary and secondary eclipses on June 11 and 14 each lasting around 20 hours.

The brightness and requested precision of 0.01 or better makes this an ideal candidate for wide field DSLR photometry.

I’ve taken pre-eclipse images but cloud prevented me from imaging the primary eclipse. I’ll take further images over the next few days, hoping to record the secondary eclipse.

Update on novae in Sagittarius

December 11, 2016

It’s been a month since my last update on ASASSN-16ma and  TCP J18102829-2729590, mostly due to family commitments; my wife was out of town with her sick father, and looking after her mother, so I was busy keeping things going on the home front.

As can be seen below, both novae have been in decline for most of that time.



ASASSN-16ma declining?

November 11, 2016

Poor weather prevented any observations last night but tonight the sky cleared after a late afternoon storm and I estimated the nova at magnitude 6.3.


So, it’s been gradually declining for 3 days, but whether that continues remains to be seen.

ASASSN-16ma update

November 9, 2016

As mentioned in yesterday’s updated post (with finder chart), conditions last night were less than ideal, but when the clouds cleared enough, I estimated the nova’s magnitude at 6.1.



ASASSN-16ma: easy binocular object

November 8, 2016

Last night’s observation of ASASSN-16ma was with 7×50 binoculars rather than my Meade LX-90 8″ SCT. The nova is now on the verge of naked eye visibility!


I estimated the nova at magnitude 5.5 last night with one before mine at 5.4 and two subsequent observations of 5.8 and another at 5.9. Mine are highlighted in purple as usual.

Here’s the section of Sagittarius of interest as it currently appears from Adelaide, low in the south-western sky at around 9pm:


The nova is just west of the circled star HIP 90012, the 6.2 (labeled 62) magnitude star near the middle of this AAVSO finder chart:


If you rotate this chart 90 degrees to the right, it will have roughly the same orientation as the Stellarium sky scene.

Alnasl is the star labeled 30 (magnitude 3.0) at bottom right of the finder chart. Kaus Media corresponds to the label 27 and Kaus Borealis with the star labeled 28. Kaus Australis and Φ Sagittarii do not appear on the finder chart, but would be off to the left of the unrotated chart.

As I write this, the sky here in Adelaide is quite overcast, so there may be no observation from me tonight.