Search found 389 matches

by JohnM
Mon Feb 25, 2019 10:28 am
Forum: Gallery
Topic: Mercury Observation tonight
Replies: 17
Views: 3438

Re: Mercury Observation tonight

Mike, I can't compete with that number - I think I may be on about 40-50 observations. Houses in the evening and a tree in the morning make things difficult. I have also seen two transits of Venus and two of Mercury. The November 2019 Mercury transit will be difficult from the UK due to the low alti...
by JohnM
Sun Feb 24, 2019 10:35 pm
Forum: Gallery
Topic: Mercury Observation tonight
Replies: 17
Views: 3438

Mercury Observation tonight

Managed to get the image below of Mercury before it set. Handheld from my upstairs window Canon 70D 1/90th Second f5.6 ISO6400 cropped from a larger image. Mercury was clearly visible when I found it but was lower than I expected. As you can see my Western Horizon is not very good ! The black object...
by JohnM
Fri Feb 22, 2019 4:58 pm
Forum: Telescopes and instruments
Topic: Aligning a finderscope
Replies: 9
Views: 2932

Re: Aligning a finderscope

A large part of the Hazard comes from the fact that a large proportion of the lasers on sale emit partly collimated infra-red radiation see the paper at https://arxiv.org/abs/1008.1452v1 . One thing I had not realised that while I knew that the infrared is what heats the eye and destroys the retina ...
by JohnM
Thu Feb 21, 2019 4:06 pm
Forum: Telescopes and instruments
Topic: Aligning a finderscope
Replies: 9
Views: 2932

Re: Aligning a finderscope

skyhawk,

ESO seem to manage quite well with 4 lasers per telescope on the VLT so who are we to complain ?

The lasers operate all the time they are imaging and they have 10 telescopes on site but still manage not to image the lasers from other telescopes.

John
by JohnM
Wed Feb 20, 2019 3:17 pm
Forum: Astrophysics
Topic: Earth's shifting north magnetic pole
Replies: 5
Views: 1891

Re: Earth's shifting north magnetic pole

There was an interesting post on the BGS blog in January about the unscheduled need to update the World Magnetic Model see http://britgeopeople.blogspot.com/2019/01/updating-world-magnetic-model-from.html this has some nice animations of the current declination and how it is changing with time. Wher...
by JohnM
Wed Feb 20, 2019 8:16 am
Forum: Telescopes and instruments
Topic: Aligning a finderscope
Replies: 9
Views: 2932

Re: Aligning a finderscope

Hi Mike, I agree few people would have the skills and facilities to make this out of metal. However one could make it out of wood, 3D print it or even use a bit of ingenuity with an old 35mm film canister (these are 1 1/4" diameter), a piece of 1/2" ID tube and a hot glue gun. The problem with the m...
by JohnM
Tue Feb 19, 2019 7:51 pm
Forum: Telescopes and instruments
Topic: Aligning a finderscope
Replies: 9
Views: 2932

Aligning a finderscope

In the latest edition of Popular Astronomy Robin Scagell describes the two traditional methods of aligning a finder scope with the main scope before it can be used. These are: 1: Point the telescope at a distance object during daylight such as the convenient church steeple that appears in so many of...
by JohnM
Tue Feb 19, 2019 7:03 pm
Forum: Astrophysics
Topic: Earth's shifting north magnetic pole
Replies: 5
Views: 1891

Re: Earth's shifting north magnetic pole

If the Earth's magnetic field does reverse it will be quite a slow process. During the reversal the magnetic poles are likley to be in strange places like near the equator and the field is likely to be very weak. This will have some interesting effects on the aurora. Perhaps we will have to fly Sout...
by JohnM
Mon Feb 18, 2019 8:43 pm
Forum: Astrophysics
Topic: Is the density of Dark Energy Increasing
Replies: 0
Views: 1062

Is the density of Dark Energy Increasing

ESA have announced some new results on the expansion of the early universe that seem to indicate that the difference between the measurements of the Hubble - Lemaître 'Constant' as measured locally by SN1a standard candles and that measured using the cosmic microwave background may be real and not m...
by JohnM
Fri Feb 15, 2019 10:10 pm
Forum: Computers and astronomy
Topic: PanSTARRS DR2 Temporal Photometry now available
Replies: 1
Views: 4883

Re: PanSTARRS DR2 Temporal Photometry now available

If you download the PanSTARRS DR2 photometry data as a Virtual Observatory .XML file rather than a CSV file there are two problems with the format of the .XML file you need to be aware of. 1: The data is stored in single element arrays - while not wrong I have been told this is unusual or even eccen...
by JohnM
Mon Feb 11, 2019 9:45 pm
Forum: Computers and astronomy
Topic: You can never have enough (astronomy) data !
Replies: 0
Views: 2564

You can never have enough (astronomy) data !

The database that operates the CDS Astronomical Server and is the powerhouse behind aplications such as Aladin that I have mentioned in other posts have acheived a new record in the amount of data they store. In terms of image data they have 5.21E14 bytes of image data - 521 TeraBytes - in the form ...
by JohnM
Thu Feb 07, 2019 9:55 pm
Forum: Computers and astronomy
Topic: PanSTARRS DR2 Temporal Photometry now available
Replies: 1
Views: 4883

PanSTARRS DR2 Temporal Photometry now available

If you are interested in the light curves of variable start the PanSTARRS team have now released the temporal photometry in 5 bands on 'several' billion stars. The entire data set is around 1.6 petabytes so no chance of downloading it all ! However there are several tools that allow access to the ph...
by JohnM
Sun Feb 03, 2019 7:21 pm
Forum: Observing
Topic: Meteoroid hitting the Moon during eclipse
Replies: 5
Views: 1588

Re: Meteoroid hitting the Moon during eclipse

David et al, In terms of accurate time if you have a GPS connected to a Linux Computer you can use GPSmon to see the time - however I am not totaly convinced if it shows the time from the GPS or the time from your computer clock. Whern I turn my Raspberry Pi on it shows a time before the GPS satelli...
by JohnM
Sat Feb 02, 2019 10:09 pm
Forum: Observing
Topic: Meteoroid hitting the Moon during eclipse
Replies: 5
Views: 1588

Re: Meteoroid hitting the Moon during eclipse

One thing I should have addded for the information of anyone who may come across this thread in the future is that you have to be very careful with Summer Time (Daylight Saving Time). The EXIF standard for camara image Metadata has no concept of Summer Time. The times are normally shown as what you ...
by JohnM
Sat Feb 02, 2019 4:35 pm
Forum: Observing
Topic: Meteoroid hitting the Moon during eclipse
Replies: 5
Views: 1588

Re: Meteoroid hitting the Moon during eclipse

A tip for observers using digital cameras To ensure that I can work out what time an image was taken I usually take an image of a clock before and if I remember after observing. The image below shows a typical timing shot. I also rename my images by the camera time usig exiftools. As a result it is ...