Lunar observation - 21/03/21

Hello, everyone - especially if you love observing the Moon. 
I set up my William Optics 158 mm F/7 apochromatic refractor in my back garden on Sunday 21st March 2021 to observe the Moon. 
The wind was minimal - about 10 km/h. The air temperature was 5 degrees Celsius. 

Luna was 8.4 days old. It was 52.2% illuminated. Its angular diameter was 30.6' and its distance was 392,200 kms from Earth. 
I observed our nearest neighbour at 112X most of the time for 60 minutes precisely from 18.15 to 19.15 UT. 
It had become increasingly cloudy during the second half hour. 

But never mind that! 

Using Antonin Rukl's Atlas of the Moon I saw my favourite lunar feature appear live in real time with my observing eye. 

At 18.35 UT I could only see the southern half of Rupes Recta which has a complete length of 110 kms. You see, even though it is called the Straight Fault it is tilted very slightly diagonally from south to north. Have a look at a picture and you will see what I mean. 
Yes - the sword handle of Rupes Recta was fully visible and the whole rim of the 17 km crater Birt was beginning to appear at that time. 
But the northern 50% of Rupes Recta was invisible. 

However all that was going to change by 18.55 UT. 
Suddenly the whole "sword" of Rupes Recta was totally in view with some grey surface surrounding it. 
Amazing! I have never seen such an occurrence and I have observing Luna since 1977!!
I had never thought I would ever see my favourite lunar feature appear in such a fashion with yours truly at the eyepiece. 
I am so delighted and relieved the clouds didn't ruin the show too much! 

It most certainly is going to be one of my top ten observations of 2021. 

So no 100th carbon star tonight. 
But maybe we will have a clear night very soon. Back to the Moon. There were 3 craters whose centres were in darkness: 41 km Herschel (William), 40 km Alpetragius and 55 km Thebit. The Sun hadn't shone inside them yet.
Other craters which were fully visible were: 118 km Alphonsus and its central Alpha peak, 97 km Arzachel and its central peak, 153 km Ptolemaeus, 109 km Orontius, 63 km Huggins, 51 km Nassireddin, 61 km Miller (these last 3 craters are very much interlocking), 56 km Saussure, 80 km Aliacensis, 63 km Apianus, 36 km Halley (Edmund), the man who successfully observed the comet, 30 km Horrocks, the first man to observe a Transit of Venus in 1639 with a telescope, 16 km Pickering, 28 km Sporer who studied the Sun and its sunspots, and finally, 75 km Flammarion. 
One other thing I must say: the northern rim of Alphonsus looked very complex and stunning as it was touching the southern rim of Ptolemaeus. 

Clear skies from Aubrey. 

Hello Aubrey,

Having read that you set-up your scope when you and Valerie returned from your walk I thought it might have been in vein considering that cloud blew in. So, I was delighted to read that you managed to get an observational session in this evening. And what a session you had!

I have page 135 of Rukl's Atlas open in front of me as I am writing this post, and you're right: it is tilted very slightly diagonally from south to north. It must have been a wonderful feeling to see the entire sword reveal itself over a 20 minute period. What a privilege!

And very many thanks for highlighting those other craters for us - Alphonsus sounds superb.

Very well done, and clear skies to you,

Darren.

As always i look forward to your wonderful observing reports. I hope you dont mind but I have a question about a Williams Optics Telescope. You have a large wo 158mm apo Telescope for your Observations. I currently have a Celestron CPC 800 Go to and while i use it occasionally i have found it very time consuming to setup and find it very heavy that it doesnt get the use it should, and as a result ive purchased a pair of Celestron Echelon Binoculars 18x70 mounted on a Parallelogram and finally started to enjoy observing the Stars again. Im thinking about selling my CPC 800 and Accessories and a friend of mine is selling his Williams Optics 80/500 triplet Super ED Apo. From what ive read the Stars are Pin Sharp with this Refactor, but is it a sufficient Aperture at 80mm for say observing the Moon and Splitting double stars, and also would you advise using an EQ or ALT-AZ mount for this size of Telescope. Thanks for you advice,
Stephen

Hello, Darren. 

Thank you for replying to my Lunar report. It's always nice to see such replies from you and from Stephen also. 
I have been checking as to when was the last time I observed Rupes Recta so close to the Moon's terminator. 
It was one year ago - 3rd January 2020. 
But at that time I could see Rupes Recta in its entirety. 
So that's why last Sunday night was that little bit extra special. 
When it finally reappeared just before 7 pm, it was the last time I saw the Moon before it was completely covered by cloud. 

Very best regards from Aubrey.  

P.S. Stephen. 
Please give me a little time before I reply to your post. 
I can see it's not so simple to reply to. 

Hi Stephen

An 80mm refractor is more than sufficient for observations of the moon and doubles, you will be limited when it comes to the tighter doubles, though that still leaves thousands more.
I observe the moon with my 120mm f/8.3 refractor stepped down to 50mm or 60mm, this cuts down on the glare and makes for more comfortable viewing.
There is an observer in the US who has observed the Herschel 400 with a 60mm refractor, quite a feat.
I use an alt-az mount, as does Aubrey, the set up is quick, no polar alignment and the sense of discovery is great.  Eq mounts are great too, especially if you plan to image, or you are showing objects to friends or family.
I can understand not using the bigger scope, when it becomes too much of a chore to set up, then you feel like you are losing out on clear nights.
The binoculars are a great choice and the parallelogram mount makes a perfect match.
Hope this was of some help.

Paul

Hello, Stephen. 

I agree 100% with Paul. 
He always knows what he is talking about as he has much more experience than any of us - even us all put together. 
I used to have an equatorial pillar mount which seemed to weight half a ton! Slight exaggeration I know. 
But I'm not as young as I once was. 
That's why so many are downsizing these days. Slipped discs and hernias are occurring regularly so often these days and nights. Your Celestron CPC 800 is usually found inside a dome. 
Plus there seems to strong opinions in regards to GoTo systems. They appear to break down eventually - some sooner than later. That's why my William Optics 158 mm F/7 apochromatic refractor is 100% free from all computers and what not. 
I would definitely recommend that William Optics 80/500 Super ED apo to you, Stephen. 
But please do watch out for nights when there is dew floating around. 
If dew does settle on your main lens you will have to clean it. 
In fact please consider buying Optical Wonder which is made by Baader Planetarium. 
Paul will recommend Hand Warmers for the same reason which can be bought for Amazon. 
And they are perfectly good too. 

Lastly I thank you for giving me your kind thoughts in regards to my lunar observation. 
I shall look forward to reading some of your reports whenever you have them to share with the rest of us on www.irishastronomy.org  

Clear skies from Aubrey.