|Posted by Owen Gwynne on March 31, 2018 at 6:50 AM||comments (0)|
So, someone asked the above question via this website. My immediate response was this
All telescopes are compromises between aperture (size) , magnification and bulk.
In an ideal world, you would want a telescope that had the largest possible aperture as that collects the most light and gives the brightest image.
Less obviously, you also want to consider the range of magnification you want. Now, most newbies would expect to go for the highest magnification possible, but in fact, you often appreciate lower magnification images better, because they have a wide field of view - a lot of what looks really good is actually on quite a large scale. So, for example - there are things called 'open clusters' of stars, which look really good if you can see them against the more sparse background.
In technical terms, this is measured by what's called the f/ratio, the higher the f/ratio the smaller the field of view, which can be annoying. However, a high f/ratio does give you more magnification for the Moon and Planets, though you can get the same effect on a low f/ratio telescope by using a different eyepiece.
The third factor is the physical size of the telescope - obviously, a large aperture will be bulkier than a small aperture scope, so if you have to travel to find a dark site, then a very large aperture or a very long scope will be less convenient. On the other hand, if you have a really dark sky, you will get a lot more out of a smaller scope than you would from towns.
There are several designs of telescope, refractors (the traditional telescope with a lens at one end and the eyepiece at the other) can give very good clear crisp views, but getting a large aperture rapidly gets expensive.
Reflecting telescopes can be larger for the same price, so the Newtonian telescope can be quite long - but generally has a lower f/ratio so gives lovely wide angle views. Don't get one that's too small as it misses the main advantage of offering larger apertures for the price.
There are other telescopes that have a combination of lens and mirrors (catadiotric) that can give less bulky telescope tubes, but these designs have high f/ratios so give a relatively narrow field of view. These are known as SCT (Schmidt Cassegrain Telescopes) or Maks (Maksutov) depending on the design.
Across the range of astronomy, there are lots of areas that people get interested in, and different telescope designs are often suited to one area than another. So, what I suggest is getting a good general purpose scope on the basis that it's your 'first' scope - as your interest develops, you may well find yourself geting a second scope that is more suited to your particular interest.
A commonly made recommendation is to look for a 6" or 8" Dobsonian telescope, and I would agree with this for you. A Dobsonian is a reflecting scope on a simple mount that you push around by hand. If you have that, a planisphere and an app like Stellarium on your phone or tablet, you can get a very good start in Astronomy.
You'll probably want spend a bit more on widening the range of eyepieces (often the ones that come with scopes aren't that great), but eyepieces are transferable, so will be usable in any other telescopes you buy in the future.
You may be tempted by telescopes with Computers and GOTO, all I can say is that I started with those, and they generally were the cause of most of the frustration I have had with the hobby. They take a while to set up, and if they don't work perfectly you resent the extra money you spent on that rather than on light gathering capability.
There can be benefits in having a telescope with a motor drive, but I'd say save that for the future.
Of course, the best advice would be to get in touch with your local friendly Astro Society.
So, that was my advice, what would you say?
|Posted by Mid-Cheshire Astronomical Group on March 9, 2018 at 6:50 PM||comments (0)|
We've created a MCAG Photo album on Google Photos.
You can access it here - https://tinyurl.com/MCAGpics
If yiou have a Google account, you can add photos to the Album - so why not ?
|Posted by Mid-Cheshire Astronomical Group on February 16, 2018 at 2:25 PM||comments (3)|
We were contacted by one of our local primary schools, who asked if we would help with their Space Themed Science Week; in particular, whether we could bring some telescopes along to their Science Evening, for pupils and parents on Thursday 15th Feb.
The forecast was clear and we were able to take some telescopes and a mounted binocular for people to look through.
The school was really well organised, with a number of indoor and outdoor activities on offer, including an inflatable planetarium and 'Astronaut Training'. We had a steady flow of pupils and parents past our scopes, with which we could show the Orion Nebula, the Pleiades and Mizar and Alcor, the famous double star in Ursa Major.
A great evening, but we were glad to get away to the warm at 8pm.
|Posted by Mid-Cheshire Astronomical Group on February 4, 2018 at 6:10 PM||comments (0)|
A transcript here.
NEWTONIAN COLLIMATION MADE EASIER, FAR BETTER and RELIABLE
or, Making you mighty in collimation by myself, Peter Clark, a retired Master Mariner and amateur astronomer, living near South Cave in rural East Yorkshire, England. 'With California like skies, says renowned artist David Hockney.
It is in fact the script for the You Tube movie accessed via 'Collimating a Newtonian NHBS' then clicking on the arrow.
It began in 2006 as a stumble when the black plastic front cap of my 8” Wise-Newtonian cracked, so I made a new one in translucent fibre glass. Three years later when starting yet another session of indoor collimation I forgot to take it off.
'Eureka' was the response to the clear uninterrupted view through a peephole eyepiece without moving the telescope, such that the indoor stages could now be performed more easily. Take a look with a Cave Collimator off then with it on. Without moving the telescope, any distractions are dispersed as shown on the book's front cover. I became successful enough at f 4.4, but not with the f 3 spherical primary mirror of the 8”. This was because by being wrong, no instructions for Newtonian secondary mirrors could scale up to f 3.
It took 5 years from 2009 to produce the correct methods. These have proved to work perfectly and with full relevance to slower ones. Then hunting for support or else produced four suspects with the wherewithal to escape from what everyone including myself had all been sucked into. What a relief! In order to prevent intuitive and unscientific adjustments these like minds had removed two of the secondary mirror's adjusters or changed their use:-
Norton's Star Atlas 11th-16th editions, p.50, says, 'Rather than having 3 adjuster bolts, a better arrangement for the mounting of the secondary mirror is a single angle adjusting screw and a central bolt for rotating and clamping it.' Arthur P. Norton B.A. was far too polite about it and died in 1955.
Conradhoffman.com/secondary greatly improved 'The dastardly thing' in c. 2000, by his design that retains three bolts, two of which are strict followers of the central bolt.
In 2007 R.F.(Bob) Royce, in his Ultimate Newtonian web pages, 'How many times have you struggled with conventional 3 bolts holder and endured much frustration and bad language...the basic adjustment design process is INCORRECT and ILLOGICAL and does not follow right angle relationships.' The instructions in my book do exactly that.
Oct. 2010. Sky & Telescope page 70 shows Ed Jones's Tracking Travelscope, using Norton's arrangement of the secondary mirror.
From 2012 my instructions began to compliment their metalwork and start being CORRECT by starting from mechanically square, the two maverick adjusters having become strict followers of the central bolt.
The book's 3rd edition of 3.2014 has 'Rotation is superior to slewing' with these bolts, and by experience to 2009 the laser collimator had become regarded as the most unwelcome of tools.
Then in 2015 a 4th edition was suddenly needed. The Laser Collimator had become the answer to me losing the black art of sometimes getting the secondary's vertical tilt angle spot on, angels in bed saying, 'Ignore the maker's advice and try it for this purpose only.'
So Newtonian secondary mirrors need just a central bolt for travel along the main axis to position it under the focusing tube and rotate it into alignment with the eyepiece and primary mirror. Also an off centre bolt for setting the vertical angle and clamping everything. The usual two lateral bolts fitted allow unscientific fiddling. It is bad enough having one increasingly black art adjustment because of the 90° reflection angle as the f ratio reduces, without having three hit or miss bolts to be played with just because they are there. Nothing more complicated than a one port laser collimator for the secondary's vertical tilt only is well worth having.
And now to make you mighty in collimation with instructions that scale up to the task in just 4 or 6 pages. They will get it done without you being whipped by ghosts into the usual maybes and sometimes of the just about adequate and sadly wrong universal methods I have been blessed with the time to sort out that manufacturers just do not have.
|Posted by Mid-Cheshire Astronomical Group on January 28, 2018 at 6:40 AM||comments (0)|
Dr Steve Barrett has kindly provided links to the slides and a recording of his fantastic Hubble Space Telescope talk
The slides (if you didn't pick them up as a handout)
A recording of the talk (a 1h 10m video) is here
|Posted by Mid-Cheshire Astronomical Group on June 23, 2017 at 11:20 AM||comments (0)|
If anyone is interested in trying for a GCSE Astronomy, the Thursday evening group are going to be following the syllabus when we start back in September.
The course is likely to be meeting at Cransley School (to be confirmed) on a Thursday evening. There will be a mix of classroom teaching and project work, with observation work done as a group if possible on Thursdays, or in our own time. We think the school grounds are able to give reasonable views of the night sky.
Malc Beesley will be leading the course
Although the course is intended to lead to sitting the GCSE Astronomy exam, it's not mandatory - so if you just want to come along with no obligation to sit the exam at the end, that'll be fine.
If interested, get in touch via the Contact Us page and we'll let you know more about what's planned.
|Posted by Mid-Cheshire Astronomical Group on May 3, 2017 at 4:20 PM||comments (0)|
I've updated the link on the Resources page so it links to the Cloudy Nights 2017 Eyepiece Buyers' Guide
Mouse over the 'MORE' navigation and then click on 'RESOURCES' link
|Posted by Owen Gwynne on April 20, 2017 at 6:45 AM||comments (0)|
The Gaia mission from ESA continues to provide a wealth of data on stellar positions and motions.
If you're not familiar, it's a satellite that continuously scans the sky as it rotates, plotting the position of stars with unprecedented accuracy. As the satellite moves with the Earth around the sun, this gives it the scope to measure the parallax of a billion stars in our galaxy, and measure the proper motion of a lot of them too. The satellite is fitted with a spectroscope so that it can measure the radial velocity of stars as well, allowing ESA to develop a catalogue of stars with velocity measurements in 3 dimensions.
ESA has recently issued a subset of measurements, showing the movement of 2 million stars projected forward for the next 5 million years.
Details from the ESA Gaia mission web page
|Posted by Owen Gwynne on April 3, 2017 at 6:05 AM||comments (0)|
|Posted by Mid-Cheshire Astronomical Group on August 31, 2016 at 4:00 PM||comments (0)|
In our July meeting, Tracey gave us a heads-up for August's Perseid Meteor Shower. She also gave us a great advice sheet to take away.
A copy has been linked to from the Resources Page