Gfamily

To be honest, the Holmdel Horn Antenna wasn't really an Astro scope. Mine - of ones not mentioned Hale 200" Telescope at Mount Palomar (removed as already mentioned) Hooker 100" Telescope WMAP Bessel's Fraunhofer Heliometer Telescope

One thing you need to appreciate is that the RA is measured close to the Celestial Pole (at a declination of almost 80 degrees) so you have Round figures : 7909 seconds of RA per day = about 2h 11.8m of RA (32.95 degrees) But this is at 80 degrees N, so the distance across the sky is reduced by Cos (80 degrees) = ~5.72 degrees This is 20600" along the Small Circle at 80 degrees Latitude Along with the 5325" along the Great Circle of Longitude, you can apply Pythagoras (it's a small triangle) to get the 21,500" ish daily motion

Gresham College has existed since the late 16th century, with 7 original professors appointed to give public lectures in Astronomy, Divinity, Geometry, Law, Music, Physic (medicine) and Rhetoric. Since 2001 the lectures have been given online as well as in person, and there are a number of Astronomy lectures available to everyone. Amongst those that focus of the History of Astronomy are: Caroline Herschel: Discoverer of Comets The Astronomer and the Witch: Kepler's Mother The Clockwork God: Isaac Newton and the Mechanical Universe Shakespeare's Astronomy Coming up soon is Christopher Wren's Cosmos on 22nd Feb

Maybe surprisingly, it's less than 100 years since it was confirmed spectroscopically that stars are predominantly made of Hydrogen. Spectroscopic analysis showed the presence of atoms of Carbon, Oxygen, Nitrogen, Sodium, Calcium etc, and (if thought about at all) it was broadly thought that the Sun's chemical composition was similar to the Earth's. It wasn't until 1925 that Cecilia Payne, for her PhD, studied the relative strengths of those spectral lines against the strength of the Hydrogen and Helium spectral lines at the different temperatures in the Sun's atmosphere, and showed that H and He were by far the most abundant elements. This was later described by the renowned astronomer Otto Struve as "the most brilliant PhD thesis ever written in astronomy". Although her supervisor was initially sceptical of her results, they were confirmed later. Cecilia Payne married Sergei Gaposchkin and continued to do pioneering work on variable stars, and became the first female head of a department at Harvard.

The point is that there is good evidence for all the conclusions that you reject. You don't seem to have given any serious consideration of the evidence before you reject it, except for your feeling that it doesn't make sense to you. That's fine, we can't make it so that you actually consider the strands of evidence that give us the general understanding of how the universe it, but please don't assume that your rejection of the current model is based on a stronger evidence base than the explanations given here. Oh, and where has anyone said that the wavelength shift only has one cause? We know that there are multiple causes for wavelength shift, because we understand the science.

Time for me to post one of my favourite cartoons from Private Eye

In the last 6 months I've appreciated the value of Point and Track on the AzGTi (though this does rely on the value of a well aligned finder). This is useful if you can find something comfortably without alignment, you can then tighten the clutches and in the app select the "Point and Track" option. It'll then track with reasonable effectiveness. I have to say it's easier to do with my refractor, as it has a wider field of view.

If there is an obvious landmark you can identify from your balcony, you should be able to use a map to calculate its bearing (angle from True North) - with this, you can set a datum line for you to use. It should be close enough. Basically, when using North/Level, the mount moves to where it expects the first alignment star to be - when you adjust to get the first star centred, that gives the mount the correct offset to negate any inaccuracy in the North Level position.

I've very little to say, except that the RedCat is the only one that doesn't need a Field Flattener as it's a Petzval design. I've observed next to someone with a RedCat and he's getting great results from it.

It's the easiest mount I've had to set up and align. Yes, it works off your phone or tablet, and it uses your device's GPS to get your location and time. There are two easy options for aligning... Level and North - to do this you need to know the direction to your local North - i.e. towards the Pole Star (it doesn't need to be exact). Set the mount so the telescope is pointing North and is horizontal. You then choose two stars, and it will go to the first one selected (because it knows where you are, it knows where it should be relative to North). Very likely you'll need to make a minor adjustment to get it centred - it will then go the second star (which should be very close to centred). A final adjustment and confirm it's centred and the GOTO should then be good. Bright Stars - Without needing to know where North is, you just need to know where some of the brightest stars or Planets are. Select one you are definite about, and their second choice. You then need to manually move it to get the first star centred, confirm and it'll go to the second star for final alignment as above. You can download the app beforehand and there's an emulation mode to try it out. Yes, you can get a handset to control it (extra £££), but I reckon the app on the device is easier. If using it at home, you may find that your phone jumps back to your home wifi, so you need to reconnect to the Synscan wifi when you go back out - but it keeps tracking even when not connected, so it's not a problem. Forgot to say - there's also the Point and Track option - so with this, if you're looking at (say) the Moon during the day when no stars are available, you can manually point at it, and select "Point and Track" and it will track without any other alignment needed. You can also use the App alongside the Plus or Pro versions of Sky Safari or the Plus version of Stellarium on your phone. I use Sky Safari 6 Plus, which is relatively cheap (but often goes half price on Google Play, so if you're happy to wait, it's better value)

I'd reckon that the difference can safely be disregarded. What's the reason for the confusion?

Hi @gamermole - a couple of suggestions - * have a look on gostargazing.co.uk to see if there are any Astro Societies near you or any Astro Events where people are likely to have telescopes with them. This should give you a chance to have a look through a range of 'scopes, as that will help you get an idea of what you want to look at, and thus, what telescope will do best for you. * similarly, I don't know if you're one for camping, but if you are I would thoroughly recommend going to a Star Party before you get yourself a telescope. Again, people are likely to have a range of telescopes, and if you ask, they will mostly be happy for you to have a look through them (assuming they're not using them for imaging). You don't need to own your own scope to go, and there should be a good variety to consider. The only downside of Star Parties is that they are usually located in places with skies that are significantly darker than average, so you need to be aware that smaller scopes may well not perform so well at home. The first telescope that I was generally happy with was a Synscan 127 Mak, and if I want to look at the planets or close up on the Moon, that's the one I go for; however, I get far more joy from my little 72mm Refractor for looking at open clusters and galactic nebulae - the wider field of view helps to find the targets in the first place, but not only that, it helps to put them into context. Both of these go on my AZ-GTi mount - which is very reliable and easy to use - a particularly neat feature is its ability to track targets even if you haven't completed an alignment - if you can find it and get it centred by eye, then you can select "Point and Track" and it will keep it in the field of view for hours.

My first thought is that it was a true telephoto lens, where the primary doublet would have a shorter focal length than 300, and the negative lens would extend the focal length, giving a shorter than 300mm distance between the primary and the image plane. However, there is very little difference between the nominal 300mm focal length you mention and the 289mm shown on the technical spec. This makes me think that the second element is effectively a coma corrector for the relatively wide aperture f/4.1 lens, and the effects on any ray diagram would only be minor adjustments to the off axis image.

It's been cloudy today, but using eclipse glasses yesterday and on Wednesday, the big Sunspot was definitely visible.

I got a sheet of proplex* from Wickes for about £5 for a 2.4 X 1.2 m sheet. Cut to size and use sticky velcro pads to hold it closed. * twin walled sheeting used by builders to protect flooring. Lightweight, flexible, folds flat when not in use. Hard to think of anything easier.

I remember the predictions of a very quiet Solar Cycle for #25. https://www.swpc.noaa.gov/news/solar-cycle-25-forecast-update Yet it looks like we're potentially heading for the most active cycle on record.

You can take any image and add straight lines to it to make separate 'zones' for different types of program shortcuts Then, in Windows Explorer, right click on the image and select the 'Set as desktop background' menu item. Then drag the icons into the appropriate area

If you have a laminator, it is easy to print onto paper and make a fairly resilient mask that way. I made my own yesterday - used an online generator which i printed out and laminated. I then cut out the white bits with a craft knife and steel rule. I then cut around the mask, leaving 4 tabs that I can use with an elastic band to attach to the OTA (a 72mm refractor in my case)

Haven't been able to find any ray diagrams for it, but there's information here that might be of interest https://joseph-tang.blogspot.com/2017/11/tair-3-300mm-telephoto-lens.html https://allphotolenses.com/lenses/item/c_857.html http://photohistory.ru/1207248188998898.html (in Russian)

Try this page http://www.astronomycafe.net/FAQs/q1890x.html And this formula cos(A) = sin(d1)sin(d2) + cos(d1)cos(d2)cos(ra1-ra2)

This isn't the reason.

It's because the daytime ecliptic is low in the winter and high in the summer. Conversely, the nighttime ecliptic is high in the winter and low in the summer. When you saw the sun it was in the daytime, and when you saw the moon it was nighttime.

This link works https://www.eso.org/public/products/papermodels/papermodel_0005/ (15 hour construction time!). But your link was useful as it also gave a link to constructing a paper model of an ALMA dish https://www.eso.org/public/products/papermodels/papermodel_0001/

... that Saturn's moon Titan made a very rare transit of the Crab Nebula. This allowed the Chandra X-Ray Space Telescope to make an X-Ray image of Titan's atmosphere, data which was later used to help interpret the data captured during the descent of the Huygens probe in 2005

I can't give any specific advice, but would point out that NZ is known as 'The Land of The Long White Cloud' for a reason. We were there for 3 weeks in December a few years ago, and only had two evenings where we could do any astro - and one of those was clear for just 30 minutes. By the way, if you go to the Christchurch Museum, they have an element of the scale model of the Solar System that was created at Otford in Kent for the millennium. On the scale of the model, Christchurch is the right distance for the location of Ross 154 in Sagittarius.