70/700 refractor

[tamer]

Hello all.

I am a novice when it comes to astronomy, and was planning to buy my first telescope. I came accross one for a fair price of £60 (Great Britain Pound), but not sure if this is worth it, and what I may be able to see through it.

It is a 70/700 optus refractor telescope with the following specs:

*includes 2 eyepieces, equatorial mount and aluminium tripod
*Focal length: 700mm
*Lens diameter: 70mm
*Magnification: 35x - 175x
*Adjustable alminium tripod
*6 x 30 viewfinder
*High contrast images for terrestirial and astronomical observations
*Comfortable equatorial mount with flexible handles
*High performance air-achromatic lenses for bright images
*Includes astronomy software for your PC with real time star charts to help you plan your star gazing sessions.

These are what it actually says on the box, but we all know how much companies tend to give their customers a little 'fib' here and there.

Can anyone tell me whether it would be worth paying the price asked for, and what type of things I may end up seeing with it. Otherwise I plan on buying a Sabens 6" telescope from e-bay (also not sure if it is worth it), but the prices are around what I am prepared to pay for a taster telescope for a hobby that I havent got much knowledge on.

All your help is well appriciated.

Thank You.
Tamer.

[Richard0802]

Hi Tamer, with Christmas coming up this is a good question.

The description you have given for a 70mm (3 inch) second-hand refractor sounds an excellent choice to me provided the tripod is sturdy and the objective lens, and eyepieces, are in reasonably good condition and not scratched reducing their performance.

With such a telescope expect to see enough detail on planet Jupiter to view the ‘Great Red Spot’ When more red and prominent (it changes colour on different occasion and fades from view). Also you will be able to do the timing of ‘Transits’ of atmospheric phenomena in Jupiter’s atmosphere across the planets meridian. Expect to see at least 4 Saturnian moons including Titan. You can also do lots observing the Moon, bearing in mind of course that a good 3-inch refractor is equivalent to a 6 inch Newtonian reflector when it comes to observational astronomy. Don’t forget deep-sky objects, double star observations and even comets. Comet Machholz now in the constellation of Lepus (The hare) will become a magnitude +4 body next spring. See the info in a related Forum to this one.

My advice is, view the telescope and if it looks fine and in good condition then buy it, otherwise if you are just starting out in the field of observational astronomy, then buy a good pair of binoculars, they will serve you very well indeed.

Clear Skies

[tamer]

Considering that it's not a second hand telescope, I'm guessing then that it is well worth £60. I don't think that it has any barlow lenses though, which I think magnifies the view even further. Is there anything I else I should know about buying a telescope like this, like I heard that some telescope the image might be upside down.

Also, one final question for now, will I be able to see any galaxies, nabula, messier objects, etc, with this telescope.

Thanks again.

[Richard0802]

Nice to hear from you again Tamer.

Firstly the larger the aperture of the telescope the fainter is the limiting magnitude of the objects you see, so a 50 mm refractor will allow you to see stars and etc. down to magnitude +11.2 while a 75mm will let you see down to magnitude +12.1 which makes the scope ideal to observe star clusters, nebulae and galaxies (Deep-sky objects). Because a telescope needs to gather as much light from astronomical objects as possible the image through the eyepiece will always be upside down, since inserting a extra lenses to turn the image around requires more light to do so. However the upside down image is never really a problem for astronomers.

The Barlow-lens uses optics to either X2 or X3 the magnified image seen through your eyepiece, the trade-off being that the image is correspondingly fainter due to light absorption of the lenses. Therefore the Barlow lens is very useful to observe the brighter bodies in the Sky at Night (The Moon and Planets), and the daytime Sun (Do not look through your telescope at the Sun directly, even with a dark filter it may blind you in an instant) by projecting the image onto a piece of card held behind the eyepiece.

Please also bear in mind that the image you are viewing through your new telescope is highly magnified so a sturdy telescope mounting is very important, preferably with an equatorial mounting for your telescope. Second all of the colourful images you see taken by many amateurs (some using a ‘guided’ 75mm scope) subscribed to The Universe Today Forum, and by professional astronomers, look splendid. However, the eye cannot discern these colours; astro’ photographers therefore take long time exposures. The general rule here is the Deep sky objects have practically no observable colours; the Moon and planets do have observable colours.

I hope this advise helps, if there is anything else you need to know please do drop by later.

Clear Skies

[Dave Mitsky]

Richard,

I beg to differ with a number of your statements.

A 3 inch (75mm) achromatic refractor, actually less than 3 inches in this case, is not nearly equivalent to a 6 inch Newtonian reflector in terms of light grasp and resolution. (A 90mm achromat is perhaps roughly equivalent to a 4.5 inch Newtonian.) This isn't meant to imply that small refractors, in particular the fast but expensive apochromats that are available nowadays, don't offer certain advantages, portability and large fields of view being two of them. I say this having used dozens of such instruments and being the owner of 4 of them ranging from 80mm to 101mm.

Refractors are very seldomly used without a star diagonal. In which case, the image is upright but mirror-image reversed, not upside down as is commonly, but somewhat incorrectly, said about Newtonians.

Modern Barlow lenses, especially the improved Powermate design marketed by Tele Vue, do very little to degrade image performance.

It is perfectly safe to observe the Sun using a full aperture solar filter made of Mylar, Baader AstroSolar material, or aluminized glass as long as the proper precautions are taken.

Dave Mitsky

[Dave Mitsky]

Tamer,

I have heard too many horror stories about telescopes sold on E-bay to recommend buying one there. Have you tried Astromart at http://www.astromart.com ? It's a safe place to buy used astronomical gear at reasonable prices.

You may want to read Stephen Tonkin's advice to telescope buyers in the UK at http://astunit.com/tutorials/firstscope.htm before making a decision.

Keep in mind that a 70mm telescope will not provide awe-inspiring views of very many deep-sky objects or the planets for that matter and that dark skies will be essential for successful DSO observing. For example, I observed the relatively bright galaxy NGC 1023 in Perseus last night with my 101mm Tele Vue apochromat from a very dark site (M13 is visible to the naked-eye there) and it appeared as only a small and fuzzy circular patch.

Dave Mitsky

[Richard0802]

Hi David,

That's all very well if you happen to be on the rich list and able to afford an expensive specialised Sun filter and a near top of the range telescope!

An amateur astronomer just starting out and looking for his first scope does not have the money to buy such a good modern telescope. The 3-inch scope described by Tamer sounds a good choice for a beginner to learn his way around the night sky and to look at the deep sky objects.

However, instructing a new comer that it is safe to look at the Sun through his telescope using a Mylar, Baader AstroSolar material, or aluminized glass, without explaining what Myler or Baader AstroSolar material is is not a good thing to do. Even though you add " as long as the proper precautions are taken"

This buddung astronomer may not know what you mean by 'proper precautions.' :unsure:

[tamer]

Sorry for the late reply,

Got the telescope yesterday, been testing it out. A little disapointed, but preety sure that it wasn't because of the telescope, reading up on telescopes before hand I was quite aware that I shouldn't have too high expectations when paying only 60GBP for a beginners scope, when everyone talks about paying between 200-400 for one.

Where did the disapointment come from??? British weather! Always cloudy. Got the chance to see some stars yesterday, but stars on their awn seem rather boring. Looked for M45 and the Andromeda Galaxy but couldn't locate it. Another bad thing for me is that I live in London, AND in a block of flats, so as you can guess, my first observations were through a window on the forth floor. The light polution didn't help, and I'm guessing normal polution also played a part.

Looks like I will need to wait for some clear skies and someone to drive me to a place with less light polution (being lazy and not applying for a driving licence some time ago wasn't a good idea). My girlfriend and my brother also seems a little interested in the telescope aswell so I guess it shouldn't be that difficult to convince them.

Also, with the moon on the other side of the flats didn't even allow me to do any lunar explorations, (not that it wasn't explored already).

Anyways, once again, thank you for all your help and advice. I don't think I made a wrong decision with buying the telescope. Looks like it's worth a lot more than the 60 that I paid for it. Quite a good mount. Not that happy with the eye pieces, but will probably invest in a few more in the future. With the interest that I currently hold for astronomy, I think I will be asking a lot more questions in the near future.

Now, lets hope the clouds bugger out the way.

Tamer

[Metalllion]

Hi Tamer.
Don't worry about the weather, that was to be expected.
It's called "The Curse of the New Scope" and it means that nobody who buys a new scope is entitled to use it for at least 2 weeks.
Florida has been hit by 3 hurricannes in a row and everybody is searching for the fool who bought a 16" sct down there
In the meantime, just go to http://cleardarksky.com/ , enter your location and check if the weather will improve.

Clear sky and bright stars to you.

[Dave Mitsky]

Originally posted by Richard0802@Sep 22 2004, 11:53 AM
Hi David,

That's all very well if you happen to be on the rich list and able to afford an expensive specialised Sun filter and a near top of the range telescope!

An amateur astronomer just starting out and looking for his first scope does not have the money to buy such a good modern telescope. The 3-inch scope described by Tamer sounds a good choice for a beginner to learn his way around the night sky and to look at the deep sky objects.

However, instructing a new comer that it is safe to look at the Sun through his telescope using a Mylar, Baader AstroSolar material, or aluminized glass, without explaining what Myler or Baader AstroSolar material is is not a good thing to do. Even though you add " as long as the proper precautions are taken"

This buddung astronomer may not know what you mean by 'proper precautions.' :unsure:

Richard,

I certainly don't consider myself to be rich. I made a Baader AstroSolar filter cell for about $10 which I use with an 80mm f/5 Orion ShortTube 80 achromat - http://www.telescope.com/shopping/product/...&iProductID=330 - which is hardly a high-end telescope. I also have a Celestron Mylar filter, which I consider to be inferior, for my 114mm f/7.9 Celestron C4.5 Newtonian.

The proper precautions are only common sense. Inspect the filter before use for integrity and make sure that it is securely positioned before looking into the eyepiece. I spend far too much of my time on astronomy forums to spell out everything I say in detail. If someone has a question they can certainly use a search engine if they have the intiative or reply directly if they don't. For the benefit of novices everything one needs to know about solar observing can be found at http://www.roboticobservatory.com/jeff/faq/

Dave Mitsky

[Richard0802]

Hi tamer,



Excellent, so now you have your ‘new’ telescope and have already tried it out from your flat window. From your description the Moon was low in the SSW in the constellation of Sagittarius, which means that you have a northern view from your window. I guess that you now need to know how to prepare yourself for an observation session. For this you will need a torch, pen (blue-ink), pencil, sketch pad, comfortable chair, star atlas book, warm clothing, flask of tea or coffee, clock or watch to note the time --- Oh yes, a box of chocolates for your girlfriend, the type wrapped with coloured cellophane, so that you can pinch all of the red ones!

Once you have your red cellophane fix this over the front of your torch to hide all of the white light so it only shines red, which is important.

You will need to sit indoors with all the lights off for several minutes to allow your eyes to become accustomed to the dark so that you may see fainter detail through your scope. If you turn on a white light after this, the effect is lost and you will have to do it over again. The red torch will not affect your vision and will allow you to write down notes, make sketches etc. The flask will let you have a warm drink without having to make one to again avoid turning on a light. When looking through the scope’s eyepiece at an object that looks faint, keep looking through the eyepiece and divert your vision left or right. The front ‘side’ part of your eye(s) are slightly more sensitive to light than the light entering the retina, so the object will seem brighter.

What can you see in the night sky right now? I encourage you to look at Dave Mitsky’s monthly sky diary. He is a highly experienced amateur astronomer and his sky notes should tell you everything that you need to know about what’s up and visible. David’s October diary should be appearing on the Forum shortly. The star map here will show you what is on view right now. If you have any questions about this subject do go along to David’s forum pages and pop your question, and I am sure he will do his best to answer it for you.

If you would eventually like to observe deep-sky objects, it’s a good idea to begin learning the constellation patterns. Many star atlases today indicate these by lines connecting the main star members (like dot-to-dot) as shown on the map here. The history of star atlases goes back along way. The Hyginus. Poeticon astronomicon. Venice, 1482, was one of the primary ancient literary sources on the constellations. It is important to recognize that star maps were based on star catalogues, and the principal catalogue used for star maps until 1600 was that compiled by Claudius Ptolemy in the second century A.D (Ptolemy, Claudius. Almagest [m]. Venice, 1515). Without going deep into this topic, the point I am making is that these old star atlases depict the constellations as true character figures. Cassiopeia as ‘a queen sitting on her thrown, Draco (The dragon), Ursa Major (The great bear) or Triangulum (The triangle), and so on. With this in mind I rather like the star atlas, Flamsteed, John. Atlas coelestis. London, 1729. John Flamsteed was the first Astronomer Royal of England and presided over the building of Greenwich Observatory. He was a dedicated observational astronomer, and his "British Catalogue" of stars, finally published in 1725, well after his death, brought stellar astronomy to a new level. Follow this link and you will be able to see many original pages from these early star atlases. B)

USEFUL LINKS

1. Flamsteed's Atlas Celeste

2. Original Star Atlases

Finally, aim to learn one new constellation every clear sky, then move onto locating the brighter deep-sky objects in each of these constellations using either the (M) essier or © aldwell catalogues.

Lots of luck with your new astronomical hobby tamer. If you have any questions, of course you can always return to this Forum and either David Mitsky, myself or other contributors will do our best to answer them.

Clear Skies