Tuesday, 31 March 2020

Venus's Close Encounter with The Pleiades


Venus’s Close Encounter with The Pleiades


Messier 45 the Pleiades by Mary McIntyre, October 2016

The path of Venus during the first half of April. Map created by Mark McIntyre using Star-Charter

During the first week of April, observers will be treated to an awesome spectacle in the western sky after sunset.  The stars within Messier 45, the Pleiades, will be joined by the extremely bright planet Venus. This open cluster which is also known as the Seven Sisters, is a firm favourite amongst astronomers because the gas and dust around the young, hot and blue stars are very striking in long exposure photographs.  



Venus moving through the Pleiades - 1st - 5th April.
Animation created by Mary McIntyre using Stellarium and PIPP

Venus is currently blazing around mag -4.5 and on 2nd, 3rd and 4th of April it passes very close to the Pleiades. The animation above shows the position of Venus from 1st – 5th April. On 3rd April it is at its closest and will look like an extra “star” within the cluster. The picture below shows the closest approach on 3rd April.  



The position of Venus and the Pleiades at 21:00 BST 3rd April 2020

Screenshot from Stellarium

It’s not unusual for Venus to be visible in the same part of the sky as the Pleiades, but it’s only once every 8 years that it passes this close to the cluster, and it always occurs in early April. This is due to the orbital resonance between Venus and the Earth. This ratio is 13:8, which means that Venus orbits the Sun 13 times in the time it takes the Earth to orbit 8 times. The next close conjunction will occur on 4th April 2028.


The conjunction can be seen with the naked eye, but it will look even better if you observe it with a pair of binoculars or a small telescope and it will make a fantastic photo opportunity!  Venus and the Pleiades will become visible in the West after the Sun sets. The best time to view them will be around 21:00 – 21:30 BST but they will remain visible until they set at around 23:30 BST.

Mary McIntyre FRAS
www.marymcintyreastronomy.co.uk








Friday, 20 December 2019

Lunar X and V Times for 2020


Lunar X & V Times 2020

The Lunar X and V are transient lunar features which are visible on the lunar surface for about 4 hours, once a month. They are caused by sunlight illuminating the edge of craters. The “X” is caused by light illuminating the rims of craters Blanchinus, La Caille and Purback. The “V” is caused by light illuminating crater Ukert along with several smaller craters.  They are at their most striking when they are visible on the shadow side of the terminator, but they will remain visible against the lunar surface even after the terminator has moved because they are brighter than the surrounding area.


Lunar X & V - 11th May 2019 by Mary McIntyre



The X and V are usually visible a few hours before First Quarter phase, however, due to libration, the exact time of the X and V being visible is different from month to month. I initially used the Lunar Terminator Visualisation Tool to get the approximate times of the X and V, then as I did in previous years, I used the NASA Scientific Visualisation Studio Moon Phase and Libration tool for 2020 (https://svs.gsfc.nasa.gov/4768) to check the start times. I did this by scrolling through hour by hour on the date of the X and V to ensure I had the most accurate times for the X and V becoming visible.  The times I recorded are listed below.  There is no fixed end time listed because as mentioned above, these features remain visible even after the terminator moves across them. But if you assume they are visible for around four hours from the start time, you will see them at their best.


The Lunar X and V on the illuminated side of the terminator, 5th May 2017
By Mary McIntyre

Although the X and V occur every month, the time may be before the Moon has risen or after it has set from your location, so you will not see them every month. They may also be visible during daylight, and they are more difficult to observe and photograph on a daytime Moon.  Please also note that the times given are in 24 clock and are in UT (the same as GMT) so you will need to correct for time zones and daylight time savings changes. I have included the approximate moonrise and moonset times from Oxfordshire, UK and a note about when the X and V are visible from the UK.  

Date
Start Time of X & V
Moonrise
Moonset
Visible From UK?
2nd January
20:00 UT
11:50
23:50
Y
1st February
10:00 UT
10:50
00:55
Y (Day)
1st / 2nd March
23:30 UT
09:35
01:00
N
31st March
13:00 UT / 14:00 BST
10:10
03:10
Y (Day)
30th April
01:45 UT / 02:45 BST
11:00
03:20
N
29th May
13:45 UT / 14:45 BST
11:20
02:20
Y (Day)
28th June
01:30 UT / 02:30 BST
13:10
01:30
N
27th July
13:00 UT / 14:00 BST
13:40
00:15
Y (Day)
26th August
00:30 UT / 01:30 BST
15:35
23:45
N
24th September
13:00 UT / 14:00 BST
15:45
23:20
Y (Day)
24th October
01:30 UT / 02:30 BST
15:51
00:30
N
22nd November
14:30 UT
13:45
23:40
Y
22nd December
04:30 UT
12:45
01:00
N

There are seven occasions during 2020 when the X and V are visible from the UK, but unfortunately only two of those occasions coincide with a night time Moon, the first being on 2nd January from 20:00 UT. The second occasion is on 22nd November when they first become visible during daylight, but by 17:00 UT it should be dark enough to make it easier to spot them.  However, if you have good binoculars or a telescope you will still able to observe the X and V on a daytime Moon, so please do try to find them on those dates too.


The Lunar X & V up close 11th May 2019 - by Mary McIntyre

Monday, 4 November 2019

Mercury Transit - 11th November 2019


Transit of Mercury 2019

On Monday 11th November 2019, we have the opportunity to observe a rare event; Mercury transiting the disc of the Sun. The last time we saw this from the UK was on 9th May 2016, but the next transit will not take place until 2032.

A transit occurs when a planet whose orbit is closer to the Sun than Earth, passes between the Earth and Sun, and the planet can be seen as a small black disc crossing the Sun’s surface. As viewed from Earth, the only planets that transit the Sun are Mercury and Venus. Because the orbits of these planets are slightly tilted, they do not cross the Sun’s disc every time they orbit. Approximately 13 times per century Mercury transits occur, but Venus transits are rarer. The last Venus transit took place in 2012, but the next one isn’t until 2117. The reason Mercury transits are more common is because Mercury is closer to the Sun and orbits more rapidly than Venus. Mercury only takes 88 Earth days to orbit the Sun whereas Venus takes 225 days to complete one orbit.  That said, a Mercury transit is still a pretty rare event.

How to observe the transit:
On 11th November 2019, Mercury starts to move across the disc of the Sun around 12:30 pm (GMT) and continues throughout the afternoon, leaving the disc after sunset.


Graphic showing Mercury’s position at 11:45am and 3:45pm on 11th November
Created by Mary McIntyre using Stellarium.
Note: we are unlikely to see this many sunspots on Monday!

SAFETY NOTICE: NEVER EVER ATTEMPT TO LOOK AT THE SUN EITHER DIRECTLY, OR THROUGH BINOCULARS OR A TELESCOPE WITHOUT THE CORRECT EQUIPMENT. YOU WILL GO BLIND! DO NOT UNDER ANY CIRCUMSTANCES TRY TO USE ECLIPSE GLASSES WITH BINOCULARS OR A TELESCOPE; THE MAGNIFICATION OF THE SUN WILL BURN STRAIGHT THROUGH THE GLASSES AND CAUSE PERMANENT DAMAGE TO YOUR EYES. IF YOU ARE USING A TELESCOPE, MAKE SURE YOU KEEP THE CAPS ON THE FINDERSCOPE. EVEN THAT LOW MAGNIFICATION IS ENOUGH TO BURN YOUR EYES AND CAUSE PERMANENT DAMAGE.

The Sun is so bright that even a glance at it through a telescope or binoculars can cause blindness. So you need a full-aperture filter of suitable material such as Baader AstroSolar on the front of your telescope or binoculars. Baader AstroSolar filter material is available from many suppliers in A4 sheets for about £20.

If your telescope has a lens cap that has a smaller removable cap, you can make a filter that sits inside the larger cap, making sure the smaller aperture cap is completely covered with solar film. It’s important to check that no light is getting through around the edges and that there is no damage anywhere on the filter.
Alternatively, you can buy glass solar filters, like the one in the image below made my Thousand Oaks. Whichever filter type you use, make sure it is well-secured with no risk of the filter blowing or falling off. 
A selection of solar filters

If you have a suitable filter in place, you can observe the Sun directly through the eye piece. Because Mercury is so small (it will be a tiny dot!), you will need a magnification of about around 50x or more. Because Mercury is so small, you will not be able to observe the transit using eclipse glasses or small binoculars with solar filters. To give you an idea of the apparent size of Mercury against the solar disc, see the image below taken during the 2016 transit.



Using a DSLR and Zoom Lens:
If you have a DSLR camera and a 300mm (or greater) zoom lens, you can make a solar filter to sit on the front of the camera to photograph the transit. If you do this, make sure you use the live view screen to achieve focus; never look through the view finder! You will find it easier if you cover the back of the camera and your head with a black blanket to keep out residual light while you try to get the camera focused. Below is the set up I used for the total solar eclipse in the USA back in 2017.
Home-made DSLR Solar Filter


Telescope Projection Method:
If you do not have time to make or buy a solar filter, you can use a projection method. But do not attempt this method unless you know what you’re doing. Do not attempt this method if you have a large aperture reflecting telescope because the parts may get too hot. Also make sure that all of your eye pieces and eye piece holders are not made of plastic, because they will melt in the heat of the Sun.
First of all, you need a piece of white card, or white paper glued onto a piece or card, or a piece of white board. This will be your projection board. If you can, try to find a way of mounting it onto a tripod or broom handle so it is free standing. It will help you greatly later on if it can stand up by itself.

Begin by lining up your telescope with the Sun.  Place your projection board behind the eye piece and use the finderscope to help you get things lined up properly. If you are using a refractor, your projection board will be behind the telescope, but if you are using a reflector (as shown in the image below) it will be at the side. When everything is in place, you will see a large bright disc on your projection board. Adjust the focus on your telescope until the disc is nice and sharp. You should easily be able to see any sunspots which are currently visible. Once you have aligned the telescope, immediately put the caps back onto the finderscope because even that small amount of magnification can cause permanent eye damage if you accidentally look through it. During the transit, you will see Mercury as a tiny black dot slowly passing across the projected Sun’s disc. If your telescope does not track, make sure you constantly make adjustments to keep the Sun in shot, otherwise in the internal components of your telescope may be damaged. If you want to take a photograph of the projection on the white board, it is safe to do so, but do not try to take a photograph by holding your camera up to the eye piece - it will burn your camera sensor! Never leave a solar projecting telescope unattended in case somebody who doesn’t understand the danger tries to look through the eyepiece.



Using a 4.5” reflector to project the Sun

At the time of writing (4th November) the weather forecast is not looking good for my location in North Oxfordshire. But let’s hope that we get at least some brief cloud gaps and get a chance to witness this rare event. Wherever you observe this event, good luck and happy observing!

Mary McIntyre FRAS
Oxfordshire, UK


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Saturday, 26 January 2019

Getting Started with Lunar Sketching


Lunar Sketching

I am always totally captivated by crater shadows on the Moon and they are one of my favourite subjects to sketch. If you have never done any astronomy sketching before, it can be a daunting prospect. But don’t worry! It’s really not that difficult to get started and produce some great results. I have done several lunar and solar sketching workshops and even people who have never done any art before created stunning sketches just by following some basic steps. In this blog I will talk you through how to get started with sketching the Moon by explaining how I created the sketch below. This blog accompanies my You Tube video where I explain what I’m using and includes a timelapse video of me completing the sketch. 

To view that video click here: https://youtu.be/pc4u3_9ET2w

The Flickr version of the video is here: https://flic.kr/p/2embLtJ



It’s up to you whether you prefer to sketch on white paper with pencils or if you would rather use black paper and pastel/charcoal pencils. I enjoy both, but you can get such a striking result using black paper, so that is now my material of choice. I just buy black paper – it doesn’t need to be anything fancy. If it has too much texture it will be difficult to get fine detail into your work with pastels. Do keep in mind that pencil sketches won't dull like your pastel sketch will.


To begin, chose a photo that has lots of really well defined regions of light and shadow. The photo below was taken with the Liverpool Telescope which is a 2 metre robotic telescope in La Palma. Images taken through the National School’s Observatory access to this telescope are all available to use for educational purposes. I chose this photo because it is one of my favourite lunar regions and it has some lovely crater shadows. I downloaded the image and processed it first.





To begin, chose which part of the image you are going to sketch. You don’t have to draw the entire thing, so don’t panic if you feel a bit overwhelmed! Just pick your favourite part of the image, zoom in on it and sketch that.  I start my sketches by very lightly outlining the regions I’m drawing. If it’s a full disc image you’re working from then draw a circle first. 


In this instance, the craters are close to the terminator, so first, I very lightly marked out where the boundary was between the illuminated and non-illuminated sides, taking into account the crater morphology along the terminator. Then I lightly marked out the outlines of the craters. If you think of your image as a clock face, it will help you with placement of the features. You can also draw out a grid pattern on a clear acetate sheet and lay it over the photo. Then you can tackle one small square at a time. Once I’d finished with some basic outlining, I lightly shaded all of the illuminated side with white pastel pencil and blended it into the paper using cotton wool to create a light grey base colour.








Once I had a grey base, I began to mark out the regions which were very black, like the shadows on the crater floors. Alongside this, I also began to mark out the areas which were the brightest white. It helps to view the lunar surface with an abstract eye, and focus on just the shapes that the light and shade are making. Always keep in the back of your mind where the light source is coming from that is creating the shadows. I constantly switch between white and black pencil when I’m doing this step. Once I had the white and black areas marked out, I filled them in.





Now the rest of your sketch is about figuring out all the shades of grey in between the white and black. I work on small areas at a time, zooming in on the picture if I need to. But remember to zoom out again before moving on the next bit or else your scale will completely wrong in the rest of your sketch! I find blending with cotton buds really useful for this step. I usually have a couple for blending lighter shades and a couple for blending darker shades. 



When was happy with the fine detail around the craters, I moved onto the flatter surface regions.  Once you’ve blended a few times, there will be a lot of pastel colour on the cotton buds, so you can use them to mark out and blend out differences in colour on the surface. Then I added the finishing touches.

There have been many times when I was part way through a sketch where I’ve thought it was going badly and I wasn’t at all happy with the results I was getting. The best thing to do in this situation is to walk away for a few minutes and come back to it with fresh eyes. You will be amazed at how different your opinion can be just by viewing the sketch from a different angle. Also try taking a photo of it and look at it on the back of the camera. It’s amazing how different it will look. A few hours after I had filmed the timelapse video, I looked at my sketch again and realised that there were several small details I’d completely missed, so I took ten minutes to add them in and photograph the sketch again. So the completed sketch here is slightly different from the version in the You Tube video.


What I find interesting in my sketching workshops is how everybody can be sketching the same crater, yet every single sketch looks different. You can see this in the collage photo below which shows the results from a class of year 10 pupils at a local high school. None of them had ever done astronomy sketching before but the results were fantastic! No two people will ever sketch something in exactly the same way; your sketch will be your own unique style. So don’t compare your sketch with those produced by other people. 



If you have done your sketch with pastels, it's important that you keep it in a clear plastic folder to prevent it from getting ruined. You can fix pastel artwork with fixing spray or hairspray, but I've never yet found one that doesn't spoil my picture. As soon as I finish a sketch, I photograph it. I then put my original artwork into a folder and try not to get them out. I never take my folder of originals out of the house! I usually order printed copies of the photograph of the sketch and keep those in a separate folder which I take to talks with me. Pencil sketches will be fine to keep without any fixing.
 
In addition to recording your astronomical observations, astronomy sketching is actually a lovely art form in its own right. I have produced sketches of the Moon as it looked on a date that has meaning to a loved one, framed it and given it as a gift. I also paint astronomy inspired designs onto tote bags, and have even painted sunspot inspired designs onto glass cabochons and made them into necklaces. The possibilities are endless.


I hope you found this blog helpful and that you feel inspired to have a go at sketching. Working from a photo gives you the chance to really focus on fine detail, but you can use all of the same techniques when working at a telescope eyepiece. If you do have a go at some astronomy sketching, I would love to see your results, so please tag me on social media so I can see your work.



  
Some of my astronomy inspired designs on tote bags and necklaces

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