Search found 450 matches

by JohnM
Sat Apr 10, 2021 9:44 am
Forum: General chat
Topic: Another possible meteorite fall
Replies: 4
Views: 170

Re: Another possible meteorite fall

In the early reports of this event someone reported that there was a flash - assumed to be from the meteor disintegrating above the Somerset coast in the Minehead - Watchet area. There were also reports of a fireball in South & North Wales.

Are these related or are they mistaken reports ?

John
by JohnM
Sat Apr 10, 2021 9:30 am
Forum: General chat
Topic: Another possible meteorite fall
Replies: 4
Views: 170

Re: Another possible meteorite fall

They will find a lot of craters plus metal fragments in the North of the New Forest east of Fordingbridge as this was used as a development bombing range in WW2. The largest bomb ever dropped on the UK was dropped there (by the RAF) and created a crater 130 yds across though it was filled in after t...
by JohnM
Sat Apr 10, 2021 9:21 am
Forum: Pop Astro Live
Topic: Viva Vicky
Replies: 12
Views: 800

Re: Viva Vicky

Thanks Bob,

The question was from me - I will have a look at your comments in General.

John
by JohnM
Thu Apr 01, 2021 6:54 am
Forum: General chat
Topic: Discovery of Phosphine in the Atmosphere of Venus
Replies: 2
Views: 1018

Re: Discovery of Phosphine in the Atmosphere of Venus

Eva, I think that 'proven' is to strong a word for what is still an uncertain conclusion. The latest published paper by Greaves et al defends the detection see https://arxiv.org/abs/2012.05844 There is a paper (yet to be peer reviewed or published) at https://arxiv.org/abs/2101.09831 which states in...
by JohnM
Sun Mar 28, 2021 9:50 am
Forum: General chat
Topic: What is your favourite silly Unit in astronomy
Replies: 19
Views: 575

Re: What is your favourite silly Unit in astronomy

Brian, I guess No14 filters are difficult to find as no one uses them - the table at https://www.millerwelds.com/resources/article-library/selecting-the-right-welding-helmet-for-you shows 14 as the comfort level for 'very' high current welding but accepts that you may need to go down to shade 10 if ...
by JohnM
Sat Mar 27, 2021 7:49 pm
Forum: General chat
Topic: What is your favourite silly Unit in astronomy
Replies: 19
Views: 575

Re: What is your favourite silly Unit in astronomy

David, I think you have a typo - the 7th root of 1000 is 2.6827 not that the difference is going to change much ! I wonder how they came up with that ratio. Perhaps they decided they needed to cover a range of 1000:1 and decided to use 7 steps of equal apparent attenuation. With most welders glass s...
by JohnM
Sat Mar 27, 2021 4:47 pm
Forum: Space exploration
Topic: Tianwen-1 reaches Mars
Replies: 15
Views: 539

Re: Tianwen-1 reaches Mars

Brian, I think we need someone who understands more about the aerodynamics of rockets than me to answer that question. It's not going to be easy as while there are models of the Earth's atmosphere I guess our knowledge of the density profile of Venus's atmosphere is a lot less well known. The ascent...
by JohnM
Sat Mar 27, 2021 10:35 am
Forum: General chat
Topic: What is your favourite silly Unit in astronomy
Replies: 19
Views: 575

Re: What is your favourite silly Unit in astronomy

Dr Becky Smethurst has a video about Bizarre Units used in astronomy at https://www.youtube.com/watch?v=hsEB65Q4kHI A lot of these are just units used for the very small or very large such as the Barn , Jansky & The Parsec and it's multiples. The units that I find most interesting are those used...
by JohnM
Fri Mar 26, 2021 9:55 pm
Forum: Space exploration
Topic: Tianwen-1 reaches Mars
Replies: 15
Views: 539

Re: Tianwen-1 reaches Mars

Brian, I was thinking of the surface gravity at 8.87 m/s² you are going to require a rocket of a similar size as launching from Earth. You have to land it first so I think that would be a challenge. I am not sure of the aero dynamics of getting through the atmosphere. Even if you get to orbit the ne...
by JohnM
Fri Mar 26, 2021 5:54 pm
Forum: General chat
Topic: What is your favourite silly Unit in astronomy
Replies: 19
Views: 575

Re: What is your favourite silly Unit in astronomy

Hello everyone, I think you have had long enough to consider the answer. Skywatcher is almost correct. It is called the dispersion measure and appears in Radio Astronomy. The number of electrons in 'empty' space between the radio source and the receiver result in a frequency dependent delay to the s...
by JohnM
Fri Mar 26, 2021 3:50 pm
Forum: Pop Astro Live
Topic: PAL - 26th March 2021
Replies: 4
Views: 149

Re: PAL - 26th March 2021

I quite agree with you Bob, I am not sure where the SPA would be without the enormous effort Robin puts in and no doubt others behind the scenes.
by JohnM
Fri Mar 26, 2021 11:51 am
Forum: Pop Astro Live
Topic: PAL - 26th March 2021
Replies: 4
Views: 149

Re: PAL - 26th March 2021

I think the notification requires Robin to be about to send the email so that could be another point of delay or failure.
by JohnM
Fri Mar 26, 2021 10:32 am
Forum: Pop Astro Live
Topic: PAL - 26th March 2021
Replies: 4
Views: 149

PAL - 26th March 2021

Has anyone seen a notification for PopAstro Live tonight ?

Do we just try to connect to the streaming video to see if it is happening at 20:00 UTC ?

John
by JohnM
Fri Mar 26, 2021 10:29 am
Forum: Space exploration
Topic: Tianwen-1 reaches Mars
Replies: 15
Views: 539

Re: Tianwen-1 reaches Mars - Venus Sample & Return

There is a session in the programme for the 238th Summer meeting of The American Astronomical Society on 'Venus Science & Sample Return' this is a virtual meeting next June. It will be interesting to see what the proposals are - is it just an atmospheric sample & return or something very muc...
by JohnM
Thu Mar 25, 2021 8:57 pm
Forum: Visual Satellite Observing
Topic: SpaceX launch 60 more Starlink satellites
Replies: 3
Views: 476

Re: SpaceX launch 60 more Starlink satellites

The Royal Navy cut the German telegraph cables n WW1 & WW2 not only to interrupt the long distance communications but to force the use of radio communications that could be intercepted. The normal method was to tow a grapnel behind a ship until the cable was hooked and then continue until it was...