Bright Potential Supernova in Tucana - Day 2.

Yesterday's discovery from the ASASSN team and subsequently imaged by me remotely in the afternoon is shown here in VPhot at the AAVSO. As I had used the iTelescope.com instrument T31 in Australia and had set up the link to the US based AAVSO it automatically transferred the image into the VPhot photometry software as soon as it completed the imaging run.

I set the PSN as a target and searched for comparison stars. There were none readily available as there would be for well known variable stars so I used the SkyX to find stars that were part of the Tycho catalogue. I know that this catalogue contains V and B data for each star so as I took a V image I used a star close to the target as a comparison. Strictly speaking I should have taken a B image as well and used both V and B magnitudes to generate transormation coefficients to apply to the magnitude measurement.

This shows the PSN and comparison star in VPhot

 

Here is a closer view

The result is here

I realise that the result of around 13.6 may not be very accurate as follows. 

The exposure is too long (600s) giving a near saturated  comparison star - I could not find a dimmer comparison star. As you can see from the images above there is too much difference in brightness between the target and comparison star. This may just be a case of me needing to try harder to find a suitable V value comparison.

 Here is the target showing the aperture - the inner measurement circle , the gap and the outer "sky" background annulus. As you can see the situation is complicated because behind the target is the light from the sky background AND the light from the galaxy itself. The outer annulus by necessity cuts through a region of just sky and a region of sky plus galaxy. The magnitude calculation determines the average background value per pixel within this annulus - multiplies it by the number of pixels within the aperture and subtracts the result from the measured total count within the aperture. (Total count is obtained by adding all the individual counts within the aperture. ) So - is that good enough - I need to find more information from the experts on that.

 I chose the aperture and annulus sizes so that the galaxy core and a brighter part of the spiral arm fell within the gap - excluded from the measurement. The aperture is too large because I had to use a bright comparison and the aperture MUST be the same for both target and comparison star.

 Here are the values

The value of 17589 is fine relative to the maximum (saturation point) value of 65535 - this is a 16 bit camera so 2 to the power of 16 is 65536 - meaning that there are 65536 shades of grey possible with values from 0 to 65535. Anything brighter that 65535 still returns a value of 65535 so the photometry values will be incorrect.

Here is the comparison star.

 and the ADU (count) values

So the highest value of around 62000 is NOT saturated but very close.

Also I should have used a known check star to see if the measured value for that came close to the true value. 

To be continued and improved upon ..........

UPDATED: Potential Supernovae in Tucana discovered this morning.Imaged this afternoon using T31 Siding Spring

A potential supernova in PGC 128348 in Tucan was announced at 03:12 this morning (29th October 2014) following discovery by the "Assassin" (All Sky Automated Survey for SuperNovae) team.

Details were given as follows:

Constellation: Tucana

Host Galaxy: PGC 128348 Alias: 2MASXJ23331223-6034201 NED Data   DSS (R) IMage

Object Designation: ASASSN-14jg

RA: 23:33:13.90  DEC: -60:34:11.5

Discovered: 2014-10-29.05

The dicovery V magnitude was 14.9 so it is quite bright for a supernova but I will not be able to image it from Spain at a declination of -60 degrees. As I write this it is 6:25 p.m. local in Siding Spring in Australia so there is a possibility of getting an image from one of the telescopes there a little later. 

It is a little later now and I finally managed to get an image of this Supernova by using telescope T31 at Siding Spring.

This is the reference Deep Sky Survey image

This is the image I took this afternoon from Siding Spring T31 telescope.

 The (potential)  supernova is not easily missed. To be continued.

Five galaxies in Vulpecula and the Crab Nebula

This is one of the 430 images from my Saturday Night's session. It shows 5 galaxies in a single image.

This lists the galaxies in order of the major axis size in minutes of arc.

The fainter galaxies are just visible on the image so the limiting magnitude on the 30 second image is about magnitude 18.

 PGC 64678 or NGC 6921, the brightest galaxy, is estimated to be at a distance of around 55 MParsecs (NED Data) which is about 180 million Light Years. It is moving away from us at 4567 km/s so in an hours time it will be 16 million km further away - not much chance of any NGC 6921 residents popping in for a chat then! Also if we travelled at the speed of light for 180 million years to go to see them they would have gone anyway....... It makes your head hurt.

I also took a 30 second image of the Crab Nebula

 

Clocks back - more astronomy last night - 430 galaxies -a 1 second M42 image and Variable Stars.

The extra hour last night meant that I felt I was given more observing time so my last image was taken at 3:02 a.m. (updated time - it was really 4: 02 old time!) A busy night for the telescope imaging galaxies in Cygnus, Lyra, Vulpecula, Equueleus and Delphinus to a total of 430. I also imaged a few objects of interest - for example the Great Nebula in Orion - this is a one second image. 

Another object was the Little Dumbbell Nebula M76 - a planetary nebula in Perseus otherwise known as NGC 650.

I also imaged a few Variable Star fields - yet to be analysed.

One of the galaxies on my search list is NGC 7264 - imaged a couple of night ago.

This is a standard 30s exposure unfiltered.

Jupiter outshines Sirius this morning. Dwarf Novae request.

Jupiter was brilliant at 5.15 a.m. this morning at magnitude -2.06. Sirius is a mere magnitude -1.44.

My latitude here makes it possible to see Canis Major in its entirety and as far down as the star Naos in the constellation of Puppis. Lepus is well above the horizon with the 2nd magnitude star Arneb at its centre.

This morning Gemini was overhead flanked by Auriga, Lynx, Cancer, Canis Minor, Monoceros, Orion and Taurus.

I received an email from the AAVSO this morning following a request that specified Dwarf Novae are monitored for outburst to trigger observations using the VLA to search for radio jets. The request came from Ms. Deanne Coppejans (PhD candidate, Radboud University Nijmegen (Netherlands) and University of Cape Town) and colleagues.

These are the targets

I have marked those that take priority with a green tick.

This is where they are located. 

The blue line corresponds to an observing plan I have generated in the SkyX as a script to allow them to be imaged in one session. I aim to try to incorporate this into my SN searching for every clear night. I would prefer to use a V filter but the breakdown of my remote focuser would mean manual refocusing at the telescope as the clear (no filter) approach I use for my SN images requires a change of focus for the V filter. However an outburst is an outburst so I will take clear images and take V and B filtered images if and when required.

The AAVSO Variable Star Designations in their Variable Star Index can be found here.

Supernova 2014dg imaged yesterday in Camelopardalis

This type 1a Supernova - SN 2014dg -  is still visible in PGC 13880 in the constellation of Camelopardalis - the Giraffe. It was on my run of galaxies for my supernova search and I came across it. It was discovered in September by Koichi Itagaki - who discovered another SN in the same constellation this year - 2014aj in PGC 16897. The latter SN has faded and was not on my image that was also on last night's list. Here is 2014dg - a rough estimate comparing with nearby stars puts it between magnitude 14 and 15 so you will need a decent size telescope to spot it.

A chart showing its location is here - the green laser shows its position.

 Here is the chart of SN2014aj.

The history of this SN can be followed at David Bishop's page about it.

Last Night's Observations of Pluto - a clear night in Spain

It is 2.43 a.m. (Friday morning 24th)and I have just finished a night of observing. What a night - no humidity - reasonable seeing - no wind - clear skies. I started by imaging Pluto - I am keeping an eye on that in case it turns back into a planet again - then reimaged some potentially suspect SN candidates - carried out a run of about 300 galaxies in Vulpecula, Cygnus, Camelopardalis and others and imaged some interesting star clusters. When I am back in the UK in the winter I can look back at these images and investigate them - too late for SN searching then - that has to be tomorrow - but plenty more interest in those images. When I closed down the telescope I realised that Orion was already high in the sky- the Pleiades overhead  - Aldebaran and the Hyades, Orion then Sirius blazing away in the East. I went in to get my trusty 8 X 30 binoculars and looked at the Pleiades, the Great Nebula in Orion, the kids in Auruga then M36, M37 and M38 - it is a wonder that I ever get any sleep. Tomorrow (well today)  first thing - produce the daily astronomy newspaper, a trip down the mountain for tea bags, a 30 second dip in the pool - getting chilly now -  and start checking the imaged galaxies for supernovae.  Oh and look at the biggest sunspot group for 10 years - a fantastic sight through my (Mylar filmed) Swarovski birding scope!

Pluto first - here is the chart of the position of my Pluto image - the small square is in the exact position of my image - generated automatically by solving the plate to match the stars on the image with the stars in the chart. 

Now the image itself - Pluto is marked

Plate Solution Details

******** ASTROMETRIC SOLUTION RESULTS ********

Center RA: 18h 47m 09.55s

Center Dec: -20° 40' 18.6"

Scale: 1.44 arcseconds/pixel

Size (pixels): 512 x 512

Angular Size: 0° 12' 15" x 0° 12' 15"

Position Angle: 179° 36' from North

RMS: 0.67 (X: 0.42 Y: 0.52)

Number of Stars Used in Solution: 21 (100%)

FWHM: 2.79 pixels, 4.01 arcseconds

***********************************************

Image Details

Object Name: Pluto

Object Type: Pluto

Altitude: +23° 14' 21"

Constellation: Sagittarius

RA (Topocentric): 18h 48m 02s

Dec (Topocentric): -20° 38' 58"

RA (2000.0): 18h 47m 10s

Dec (2000.0): -20° 40' 08"

Azimuth: 216° 13' 59"

Magnitude: 14.17

Phase (%):  99.98%

Rise Time: 13:51

Transit Time: 18:47

Set Time: 23:43

Hour Angle: 02h 21m 56s

Air Mass: 2.53

Earth Distance (au): 33.06

Sun Distance (au): 32.75

RA Rate (arcsecs/sec): 0.000682

Dec Rate (arcsecs/sec): -0.000058

Rise/Set Notes:  Rise: 12:50:39 DST_NOT_SET on 23/10/2014

 Transit: 17:46:40 DST_NOT_SET on 23/10/2014

 Set: 22:42:41 DST_NOT_SET on 23/10/2014

Date: 23/10/2014

Time: 21:08:13 DST

Constellation (Abbrev.): Sgr

Heliocentric Longitude: 282.7°

Heliocentric Latitude: +2.4°

Heliocentric Radius: 32.7485

Geocentric Longitude: 281.1°

Geocentric Latitude: +2.4°

Geocentric Radius: 33.0597

Geocentric Mean Longitude: 281.1°

Geocentric Mean Latitude: +2.4°

Geocentric Mean Radius: 33.0596

True RA: 18.8h

True Dec: -20.7°

Altitude w/Refraction: 23.7343

Apparent Magnitude: 14.2

Apparent Angular Diameter:   0° 00' 00"

Sidereal Time: 21:09

Julian Date: 2456954.29738021

Sunday 19th October 2014 Mars meets Comet Siding Spring

The comet C/2013 A1 Siding Spring made a very close pass to the planet Mars at 18:28 U.T.  (Universal Time). I took a series of 10 second  images starting at 19:11 U.T. i.e. 43 minutes after its closest distance from Mars of 87000 miles. The problem was that Mars was at magnitude  0.87 and the comet was at magnitude 8.52 so a magnitude difference of approximately 8 magnitudes  - which meant that Mars was around 600 times brighter than the comet making it rather a photographic challenge. Also at the time of my first image Mars and Siding Spring were only separated by 2 minutes 15 seconds of arc! (About one fifteenth of the diameter of the full Moon.)

 Also my CCD camera does not have an anti-blooming gate and to detect the comet I needed to heavily over saturate Mars which meant that large spikes indicating an overflow due to the bright planet would get in the way of the comet image - which they did!

The other factor was that the encounter was not long after sunset and the low altitude of the event. The altitude of the comet was 12 degrees 30 minutes when I started - dropping by a degree every 8 minutes or so. The initial Air Mass - a measure of the thickness of the atmosphere the light has to penetrate -  was 4.57 and it soon reached 10! Ideally it should be 1.

I targeted the comet using my SkyX software as shown below. I knew the angle that my camera was sitting at with respect to North so I was able to superimpose a Field of View indicator as shown. This chart should now correspond exactly to the image taken.

 This is the first image taken at 19:11 U.T. 

 The star just above and to the right of the comet is UCAC3 131:242659 (from chart).

If you check this on the image there is a direct correspondence.

 The animation below shows the comet moving away from the planet and Mars moving from left to right in its orbit. The images deteriorate as the animation progresses -  eventually the mountain edge crosses the image and the objects set.

 

NGC 6716 Photometry Part 2

I was watching the video on You Tube "Seeing in the dark" (Go here to see the video and the associated interviews)and came across a reference to Samuel Palmer's painting of the comet of 1858. I paused the video and Googled the painting to discover it had been stolen from its 89 year old owner earlier this year by a con man! See this article.

From "Seeing in the Dark"

 

NGC 6716 Photometry continued.

The B image below shows NGC 6716 with 25 target stars, 1 comparison star and 1 check star

 

 These are the B results

 After going through a similar process with the V image these are the V results

 

So I have measured the brightness in B and V bands of 25 of the stars that appear to be in the cluster NGC 6716.

Of course some of these will be line of sight stars either in front of or behind the cluster. I have not taken into account the extinction of light by the atmosphere or the interstellar medium. I may try that later but first of all I will estimate the temperature of the stars by calculating B-V in an attempt to do some real science.

To be continued..........

A study of the star cluster NGC 6716 Part 1

NGC 6716 is a star cluster in Sagittarius consisting of young stars.

I took a number of images on 13th September 2014 using the T17 telescope at Siding Spring in New South Wales, Australia with a view to analysis using BV photometry so that I could find more about the cluster stars and the cluster itself.

Just how much is it possible to find out from two of these monochrome images?

This telescope holds the world record for imaging the faintest object ever imaged by an amateur - a quasi stellar object whose light started its journey 12.79 billion years ago!

Here is the telescope data courtesy of itelescope.com

Here are my 3 minute V and B images. Note that North is down and East is to the right in all of these images.

This is the 300second B image in VPhot. Two variables have been identified in the image on the right hand side.

 

 To be continued.....