Observation of the Sun

I thought I would try and do something useful today and so I took a picture of the sun. One way to do this is to use a telescope to project an image onto a white screen. Here is my attempt today:-

This is just a piece of white A4 paper clipped to a book and resting on a chair. The photograph was taken with a mobile phone camera. I used a Celestron NexStar 102 SLT (102mm refractor) with a star diagonal and a 25mm eyepiece to do the projection. The picture was taken at 12:15 GMT. I was quite pleased that the image pretty much undistorted. You can see three sunspots quite clearly in the upper left quadrant of the sun. 

Obviously, it is difficult to point the telescope at the sun because you must not look through the eyepiece or any finder scope. I achieved alignment by looking at the shadow that the scope casts and then, with the star diagonal and eyepiece removed, doing a rough projection onto paper. Once rough alignment had been obtained, I put the diagonal and eyepiece back and used the telescope slewing controls to improve it. I used the 'Solar System Align' functionality of the hand controller to enable the telescope to track the sun. For safety reasons, the sun doesn't appear in the list of solar system objects used for this purpose and you have to go into the 'Utilities Menu' to enable it. 

I have cropped the image a bit so that you can see the solar disk more clearly:-

Here is an image captured today from the Solar Dynamics Observatory (Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams):-

So you can see that the image I have taken corresponds well with the one taken by the SDO. 2976 includes the largest sunspot in this image and the spot to the left of it. 2975 is the much smaller group to the right of it. 2974 is the tiny spot on its own below left of centre.

All text and images © Duncan Hale-Sutton 2022 (except for the image from the SDO).

A trio of planets

 

We had a nice showing of three planets the other night about 45 minutes after sunset. Most prominent of these was Venus, the lowest of the three shown in this image taken on the 15th December (at 16:23 GMT). Venus is shining here at roughly magnitude -4.8 and through 8x24 binoculars you could just see the thin crescent of its sunlit side. Venus is approaching inferior conjunction on the 8th January 2022 when it will be between us and the sun. This has not been a good evening showing of the 'Evening Star' this winter due to the position of the ecliptic at this time of year.

The next brightest planet in the photo is Jupiter seen to the upper left. It was shining at magnitude -2.2 and is now beginning to fade from magnitude -2.9 when it was at opposition in August of this year. Between Jupiter and Venus is the much fainter planet Saturn shining at magnitude +0.7.

One of the other reasons I had been keen to look into this area of the sky was to see if I could find comet Leonard. This comet has just had its closest approach to the sun and is now emerging into the evening twilight. On this date the comet was observed to be as bright as 3rd or 4th magnitude and would have been located below and to the right of Venus in this image. Unfortunately, the glare from the setting sun has outshone the comet and, try as I might, I couldn't see it in the image or in binoculars. We might be able to see it climbing into the darkening sky as the days progress towards Christmas.

All text and images © Duncan Hale-Sutton 2021

A beautiful display of Noctilucent Clouds in June

About a week and a half ago on the evening of the 23rd June 2021 we had a beautiful display of Noctilucent Clouds (NLC's). I have written about these night-shining clouds before and we had a display last year about this time but this year's was much more spectacular. I looked out towards the northern horizon about 11pm and I took a number of photos over a period of about half an hour. Here are the best of them (click on any image to obtain an enlarged view):-

These were taken on a Nikon D90 at ISO 800 with exposures of 4 and 5 seconds. The colours of the images have not been altered in any way. The clouds appear as this electric blue. There is certainly quite a bit of structure in the clouds here. The first shows definite banding whilst the second has sort of waves near the television aerial in the foreground. The last is really quite complex.

I think it has been quite a good season for NLC's. You can search for other images on the spaceweathergallery.com.

All text and images © Duncan Hale-Sutton 2021

Partial Solar Eclipse on the 10th June 2021

On Thursday of last week we had a partial solar eclipse as viewed in the UK. The timings for Norwich were for first contact at about 10.11, maximum coverage (around 33%) at 11.17 and last contact at 12.27. All times BST. I decided to set up my Celestron NexStar 102SLT in good time for the beginning of the eclipse and I am glad I did because cloud began to increase after 10am and by about 10.45 we lost all visibility. I decided to project the sun's image onto a screen using a 25mm eyepiece. Initially I didn't include the star diagonal which was a mistake because I couldn't rack the focus far out enough to get a clear image. Once I used the star diagonal everything was fine. I took this image at 10.31 BST:-

This was taken with a Samsung Galaxy A21s phone camera. The 'nibble' out of the sun's image by the moon can clearly be seen. I decided to do a bit more by videoing the image with my phone and putting it live on Facebook. The resultant video can be seen here.

Elsewhere on the earth this was an annular eclipse - the further distance of the moon from the earth meant that its face didn't cover the entirety of sun. The annular eclipse began in northern Canada, moved over the north pole and ended in the far east of Russia.

All text and images © Duncan Hale-Sutton 2021

New Nova in Cassiopeia

On the 18th March this year a new nova was discovered in Cassiopeia by Yuji Nakamura of Japan and was given a designation of V1405 Cas. It was found to be about 1/2 degree south of the open cluster M52 and about 1/2 degree east of the Bubble Nebula (NGC7635). I have been meaning to get around to photographing this 'new star' since I heard the news. Within a few days of its discovery it had brightened from visual magnitude 9.6 to about 8.0 and for about 7 weeks it stayed roughly at that brightness. Then around the 6th May it began to brighten again and it reached a peak of about magnitude 5.3 on the 11th.

This image was taken on the 16th May at about 23.30 BST. I used a Nikon D90 with a 18-105mm lens at 58mm. The exposure time was 15s at ISO 1600. I have adjusted the exposure compensation by +1.0 and binned the image x2. You can click on this image to see a larger view. I have marked the position of the nova.

By the time this image was taken its brightness had dropped from its peak to about 6.6 and since then has continued fall to about 8th magnitude. You can look at a light curve for this object by going to the AAVSO website and typing in V1405 Cas in the text box where its says plot a light curve.

So what is a nova? From an observer's perspective, a nova is the sudden appearance of what looks like a new star where previously there was none to be seen. In actual fact, what we are seeing is a sudden burst of light emitted from a binary star system that was much fainter than was observable. In a classic nova, which I think this is, one of the binary star members is a white dwarf and the other is a main sequence star like our own sun or an evolved star. The orbits of these two stars about their common centre of gravity is very close and tidal forces pull material from the outer layers of the main sequence star into an accretion disc around the white dwarf. A white dwarf is the stellar remnant of a main sequence star and as such, it is compact and very dense. Hydrogen and helium from the accretion disc eventually makes its way to the surface of the white dwarf and when enough of this material collects, a chain reaction of nuclear fusion occurs and the material literally explodes like an H-bomb. The white dwarf suddenly increases in brightness by 50,000 to 100,000 times and ejects material at very fast velocities.

All text and images © Duncan Hale-Sutton 2021

The Sunflower Galaxy M63

A few days ago we had our first clear moonless night in a while. Spring has moved on quite a way since I looked at M108 and M97 - the evenings are now much lighter (it doesn't get properly dark until 9.30pm BST) and Leo is giving way to Coma Berenices and Bootes. I had been hoping to image some more objects in Ursa Major but this constellation is pretty much over head and difficult to observe for an alt-az telescope so I started to look a bit lower in the sky at Canes Venatici (the hunting dogs). In its boundaries we have M63, a magnitude 8.6 spiral galaxy. I started observing it about 10pm using my NexStar SLT and began taking a number of 30s exposures at ISO3200.

My final image consists of only 27 such frames (13.5 minutes) combined together in DeepSkyStacker and edited in Photoshop (click on the image to see a larger version). I ended up having to throw quite a few frames away due to tracking issues and because quite a number of frames were spoilt by satellite trails. M63 is obvious just right and below centre. To get a better look at it I have cropped the original image (the main one is binned x2):-

It is possible to make out a number of tightly-wound spiral arms which are "knotty" in places due to the presence of HII regions. I have increased the colour saturation of the galaxy and there is some hint of the blue colour of the arms. Also notice how the galaxy arms are more widely spaced to the left of the centre of it.

Going back to the previous picture a couple other much fainter galaxies have been picked up in the image. One is just to the left of centre and the other is right over by the right-hand edge of the frame. The former is UGC 08365 and the latter is UGC 08313. These galaxies are magnitude 14.48 and 14.73, respectively.

All text and images © Duncan Hale-Sutton 2021

The Dimming of Betelgeuse - 20 January 2020

Going back further to January 2020, Betelgeuse, usually the second brightest star in Orion, was in the news because it had undergone an unusually deep dimming. Betelgeuse is a red supergiant - this type of star has evolved significantly off the main sequence and has entered an unstable end to its life. It is a semiregular variable star - its visual brightness varies between 0.0 and 1.6 with several underlying periods of variability that have been identified as 242, 430 and 2,200 days. This star is a lot more massive than the sun. Estimates of its current mass put it at between 10 and 20 solar masses with a current best fit of 12. In terms of its physical size, if it was placed at the position of the sun, its surface would be at maximum somewhere out beyond the orbit of Jupiter. At the end of 2019 and at the beginning of 2020, it was noticed that Betelgeuse was going through a period of unusually deep dimming. A star of this size has a relatively short lifespan (a star of between 10 and 15 solar masses has a lifetime of between 20 and 10 million years, approximately) and popular speculation was that this star might go supernova.

I took this image of Orion on the 20th January 2020 just about the time that Betelgeuse hit its minimum apparent visual magnitude of 1.61. I have labelled the star for easy identification and also two other stars (the brightest star in Orion, Rigel, at magnitude 0.2 and Aldebaran in Taurus magnitude 0.85). The image is constructed from 20x15s exposures using a Nikon D90 DSLR with a telephoto lens set at 18mm (ISO3200) and stacked in DeepSkyStacker. I included the star Aldebaran in the image for comparison. Aldebaran is also a yellow/orange star and so is a better visual match than, say, Rigel which more blue/white. You can see by clicking on the image that Betelgeuse is fainter than Aldebaran.

So we know now that Betelgeuse hasn't gone supernova so what was the cause of the dimming of this star? Observations by NASA's Hubble Space Telescope have shown that the dimming was most likely caused by an ejection of stellar material that cooled and formed an opaque dust cloud between us and the star. The ejection of hot plasma was possibly caused by an up welling of a large convection cell. The outer layers of these evolved stars are inherently unstable and undergo pulsations and heat transfer is dominated by convection.

All text and images © Duncan Hale-Sutton 2021