Sunspot Special from Andy Devey

Click on the sun to access Andy Devey's Article all about the massive sunspot group.

Some photos of the telescope site with tonight's Moon

ASASSN-14jg at magnitude 14.7

From my previous blog I calculated the approximate magnitude of the supernova at 14.7 V. I display the photometry here again with the comparison and check stars identified.

I intend to determine the magnitude of the supernova every day if possible using telescopes in Australia - as an exercise for me in learning about photometry and to determine its light curve. .

The above V image was taken with T31 a 0.5m telescope at Siding Spring. The telescope also has a B filter but does not have a set of Transformation Coefficients calculated for it to the best of my knowledge. However I have reserved time on T31 to take V images at 11pm Australian time today ( 1pm Spanish time - in about half an hour as I type this) when the SN is at about Air Mass 1.24 - just less than 60 degrees in altitude.(and for the next two days)

The telescope T17 is about 0.4m but does have a set of Transformation values so I have booked that for the same time as T31 to take B and V images of the object.

==========================================================================================

Last night the Moon was bright and seeing was poor so I did no imaging. I noticed that the telescopes Telescopes remained under coverTurre is the nearest town to Cabrera where I am based up in the mountains.were available at Astrocamp - about 180 km away from me by road at Nerpio. They are a lot higher so perhaps seeing was better there than here. Nik Szymanek has a telescope there that he uses remotely(image). Astrocamp is linked to iTelescope.net and has three telescopes available for use. Astrocamp is at 1660m - much higher than my location of 400m and it has much darker skies - the development of Mojacar and Garrucha near me has brought a lot of light pollution in the last few years - back to thinking about that amateur space telescope again! The question is where can you get a compromise of not being totally isolated and dark - clear skies - it is getting more difficult every year. Remote telescopes seem more attractive. It is an Telescopes above the poolexpensive option to have a telescope hosted in Siding Spring or New Mexico but probably a lot cheaper than moving house. There is a continuous support expense however which is expensive on a monthly basis!

Andrew Harrison has done it however - here is a good description of what he has achieved.

This morning the eastern sky was red - not a good sign according to sailors/shepherds! The sun was breaking through however and I used my ETX90 with a Mylar screen to see how the Sun was doing - some sunspots - none to equal the large sunspots of last week which are on the other side of the Sun now. My friend Andy Devey (the Solar Explorer) just across the valley from me here in Spain achieved some spectacular results. One of his spectacular images - a mosaic - is shown below.

 Copyright: Andy Devey.

 I see that the images from T17 at Siding Spring have now arrived in the US and are in my VPhot image list - I need to go and sort those out - another blog later! I believe that T17 was originally based in Spain and for some reason was shipped off to Australia - I need to check that out.

Photometry of ASASSN-14jg

The three images from T31 finally arrived in my image list within VPhot at the AAVSO. Checking the images told me that the 300s and 180s exposures still gave stars that were too bright. The 60s image gives low values of ADU (counts) so I will take 120s exposures in future. The 60s V image is shown. This time I have set up one star as a comparison star and two stars as check stars. All three stars were from the Tycho catalog which includes their V and B magnitude. I intend to measure B magnitudes as well so that I can apply transformation coefficients and want to use the same comparison stars.

The problem becomes apparent - the target supernova only has a signal to noise ratio of 55 - general thinking suggest an SNR of 100 as a minimum value. If I use this image this is the result.

Now the 180 second image.

 

 The SNR of the target supernova is 114 - above the minimum but not by much. The large aperture is too big for the target. However even at this aperture size the aperture is too small for the comparison and check stars so any measurement would be inaccurate.

At 300 seconds the comparison star is saturated - it shows ADUs of 65535 so this will not work.

 So the problem is that I can not find any Tycho catalogue comparison stars(i.e. with available B and V reference values)  that are similar in magnitude to the target. If I could I could reduce the aperture size - getting a larger acceptable SNR and an accurate value from the comparison.

By taking a 120s exposure that will probably meet the requirements with the current comparison.

However by shifting the target off centre perhaps I can find suitable comparisons. That is my next task.

I could simply use the visual magnitudes (unfiltered) from other catalogues as being equivalent to a V filtered value to get an approximate indication of magnitude.

Using  UCAC3 stars as comparison and check stars

with a result

so an estimate of 14.75 mag. Note the check star measured value corresponds to the given value quite accurately.To be continued....................

More images from supernova ASASSN-14jg(taken 2 hours ago).

I just received three images of the supernova from T31 in Siding Spring Australia. They should have been sent directly to VPhot at the AAVSO but they have not appeared in the image list yet. I downloaded one myself directly ASASSN-14jg 300 second V filtered imageand tried to upload this into Vphot. Although it seems to have uploaded successfully for some reason it has not appeared in the image list. There must be some sort of issue there.

From the 300 second imageI want to get a V magnitude for the supernova based on a lighter image with lower ADUs further from saturation. For that reason I took 60s, 180s and 300s exposures and will choose the most appropriate. I will then take images every day to be able to plot the light curve.

The image on the left is the longest exposure of 300 seconds.The supernova is still bright and equals the SN in M61 which is getting all the press. 

When will we get an amateur space telescope? Clouds came down last night - cloudy at remote telescope sites.

Last night it started quite clear - I removed the double layer of "scope coats" from my C14, plugged the power feed into the socket in my bedroom (yes I control the telescope from my bedroom - very practical!), plugged in the 30m powered USB cable to the laptop as well as the USB connection to my external drive that I use to store all incoming images, started Orchestrate (the scripting package) and used that to start up the SkyX software. I then connected the telescope , the camera and the filter wheel. (Sadly my remote focuser is waiting for a new I/O chip after the lightning storm). I homed the mount and then tested the pointing by slewing the telescope to M57. There it was - not quite central but close. I clicked the closed loop slew button. What it does is takes a 10 second image, compares the image with the chart of where it thinks it should be pointing, works out the difference and slews to the correct position- takes another 10 second image and displays it. Normally it does this flawlessly and I get M57 centred exactly in the cross hairs. This time it could not solve the plate - ie it couldn't work out where it was pointing from the first image. Normally this means that cloud has moved in and sure enough when I went out there was light drifitng cloud. Not deterred I manually centred M57 and synchronised the telescope within the current T Point model and started a run of galaxy imaging in Cassiopeia (59 galaxies) and let it run. As it ran I listened to part of "Contact" that I found on You Tube(audio only) read by Jodie Foster who does it very well! (See the video section of my daily newspaper for today 1st November 2014) The images were not very good but when checked would let me identify any bright supernovae - better than nothing. By the time the run was at its end about an hour later (30 second images) the cloud had become more extensive and thicker so I gave up and went through the closing down process. I checked the images by blinking them in Grepnova with previous ones and could not see any changes indicating supernovae.

This morning I checked on the iTelescope sites in the USA and the roofs were closed - clouds!

So the question is - will amateurs ever be able to avoid clouds and rent time on a space telescope in the same way that they can with telescopes on the other side of the planet? I wonder?

NGC 6405 (M6) - the butterfly cluster in Scorpius

I used telescope T13 at Siding Spring to take this 240 second image of NGC 6405 the Butterfly Cluster.

 North is up and East is to the left.

I solved the original fits file - this is the plate solution

The image has a plate scale of 3.67 arcseconds per pixel and is aligned to within 5 minutes of North. The sky coverage is just over 1.5 degrees by 1 degree 13 minutes. The cluster is 33 minutes square so it is slightly bigger than the full Moon.

 From Burnham he describes the cluster as being "some 5 degrees north of the tail of Scorpius and about 3 1/2  degrees northwest of the similar cluster M7"  

The bright orange star is the semi-regular variable BM Scorpii. I looked this up in the AAVSO VSX catalogue:

 

The last observation of this star logged at the AAVSO was on the 30th September 2014 and was given a Visual magnitude of 6.3

 I generated a light curve on the AAVSO site by requesting 1000 days of observations be plotted noting from Burnham that it had a long period of about 850 days. 

 I find it difficult to see a regular variation and realise why the AAVSO table above did not specify a value for the period.

Back to the cluster itself it is believed to be at a distance of 400 to 450 parsecs according to Burnham but the WEBDA catalogue gives a more up to date value of 687 parsecs. The diameter of the cluster is about 25 light years.

Probable Supernova discovered yesterday 30th October 2014 in Ursa Major

ASASSN has found a probable Supernova in Ursa Major.  As I write this I am taking an exposure from New Mexico (remotely) but as the altitude is only 21 degrees it may not be usable - I am surprised that the telescope can see it!

Details were given as follows:

Constellation: Ursa Major

Host Galaxy: PGC 24396  NED Data   DSS (R) IMage

Object Designation: ASASSN-14jh

RA: 08:40:44.27  DEC: +57:15:04.91

Discovered:   2014-10-30.51

The imaging run from New Mexico has just completed (07:30 Spanish time) so I can check shortly to see if it has arrived in my VPhot image list at AAVSO. I have just looked at the jpeg image emailed to me and it is not looking promising. The fits image has not yet arrived at VPhot. Ursa Major is getting higher in the sky so I can try again if I can get telescope time in a few hours.

Last night here in Spain started off well and I started a run of galaxy imaging - but cloud soon set in and I had to abandon it. 

 Yesterday I took an image of ASASSN-14jg using the T32 telescope in New South Wales

 here it is again

 

Probable Supernova in M61 discovered by Itagaki.

A probable supernova was discovered by Koichi Itagaki in Japan.

It is not visible during darkness in Spain and is only just above the horizon at dawn in New Mexico, similarly for Siding Spring. Japan would be a good place to be!

I have booked time T11 in New Mexico to see if I can catch it tomorrow morning.

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 ..........