Archive for the ‘VStar’ Category

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

 

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.

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.

 

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.

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.

asassn-16manov11

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-16manov10

 

Update on two novae in Sagittarius

November 7, 2016

Poor weather then being away for work for three days last week has kept me away from variable star observing since October 29. Last night (November 6) I observed TCP J18102829-2729590 and ASASSN-16ma again.

While the first is on the decline currently (around magnitude 9):

tcp-j18102829-2729590-lc-nov-7

On the other hand, I caught ASASSN-16ma on the rise. My October 29 observation gave a visual magnitude of 10.3 whereas last night it was 7.3. Several hours later others were recording it at around 6.5:

asassn-16manov-7

So, ASASSN-16ma has exceeded TCP J18102829-2729590’s maximum (so far) by around one magnitude. If this rate of increase continues, who knows, maybe it will reach naked eye visibility. Here’s hoping!

 

TCP J18102829-2729590’s undulations

October 29, 2016

My visual estimate of nova TCP J18102829-2729590 last night was magnitude 8.0 using my trusty Meade LX-90 at 82x magnification. In my light-polluted corner of suburban Adelaide, 7×50 binoculars just aren’t good enough for this.

The third observation from right, three days ago, showed an apparent rapid increase in brightness. For me, one of the attractions of novae is their less than predictable nature.

Looking at the light curve today, my observations look a bit like (purple) buoys bobbing up and down on the surface of an undulating ocean.

tcp-j18102829-2729590-lc-oct-29

Maybe I’m spending too much time looking at novae at the moment. My wife would probably agree with you, even though she’s very understanding. 🙂

ASASSN-16ma = PNV J18205200-282210

October 29, 2016

ASASSN-16ma, the nova candidate in Sagittarius, has been designated PNV J18205200-282210 by IAU CBAT as per today’s AAVSO alert notice.

I made another visual estimate of the nova again last night at magnitude 10.3.

asassn-16ktlcsep29

Two novae in Sagittarius!

October 28, 2016

Since my last post I’ve made two more observations of TCP J18102829-2729590, on Oct 26 and 27. Mine are the larger purple data points. Fraser Farrell pointed out a nice recent Sky & Telescope News article about this nova.

tcp-j18102829-2729590-lc-oct-28

Another nova was discovered in Sagittarius on Oct 26: ASASSN-16ma. There are only a few observations of this one so far. Mine is at top right under the cross hairs.

asassn-16ktlcsep28

ASASSN-16ma is currently three magnitudes fainter than TCP J18102829-2729590, but the latter arrived on the scene first, after all.

The weather looks good for tonight and tomorrow so I hope to get some more observations in over the weekend.