What Do I Need For My Telescope

[lighty89]

I have a 700x76mm Newtonian Reflector Telescope, with the following specification:

• Focal Length - 700mm
  
• Aperture - 76mm
  
• Brightness - 117
  
• Resolving Power In Arc-Seconds - 1.82
  
• Focal Ratio - f9
  
• Star Visible up to Magnitude - 12
  
• Focuser - Rack & Pinion Type (Accepts 1.25" & 0.96" Eyepieces)
  

The lenses that came with it are really basic and plastic.

Even the barlow lens was.

When I come to use anything about 12.5mm lens I cant focus it at all, and planets just look like stars still, like really small, what can I do to improve this?

I'm thinking new lenses but I'm a student and cant afford a lot!

So cheap-ish lenses please?

[yeti monster]

First off, are your mirrors collimated acurately? I have an 86mm newt, of a fair vintage, which is f8.9, so not much grander than yours, I got my first view of Saturn in this scope and was bowled right over. So I would start with checking the optics. If you can borrow some known, good EPs and see how they compare to the ones you have.

What's you location, there may be a forum member close by whom you could meet up with for on hand advice/assistance.

[lighty89]

Stoke-on-Trent!!

Thanks for the advice mate, but, some of that went straight over my head!

I really want to get into this properly, its just setting it up properly.

Does it matter that the lenses are plastic? They are called "Huygens" I think.

What are EP's and how would I go about collimating the Optics?

Sorry about the questions lol!

[Cornelius Varley]

A 12.5mm eyepiece will give you 56x magnification with you telescope. A 700x76 telescope will have a practical maximum of no greater than 150x, which should be enough to show the planets as discs rather than points of light.

This website http://www.12dstring.me.uk/fov.htm will give you some idea of what you can expect regarding image size of planets etc with different eyepiece/telescope combinations. To be able to see the planets in greater detail you will need a bigger telescope. In the meantime I would advise you to replace the cheap eyepieces that came with the telescope with Skywatcher plossl eyepieces plus a 2x barlow lens.

Peter

[John]

Your eyepieces (EP's) are the weak link I think - the Huygens design is very basic indeed. To give your scope a chance you might want to invest in a couple of plossl eyepieces which cost £20 each - this is about as little as you can pay for a decent eyepiece. Do check that your scope can really take 1.25" fitting eyepieces before you buy. I would be thinking of a 25mm eyepiece and a 10mm to start with. You can then add another lens or a better barlow lens for high power later.

I would not worry about collimating right now.

[yeti monster]

No worries, none of us were born astronomers.

Are the eye pieces (EPs) in plastic sleeves? Or do you mean (which I'm sure that you don't) that the actual lenses are plastic?

Collimated light is when it is all travelling in the correct direction (opimally), so to collimate your scope you need to set the secondary mirror so that it is directly below the focuser, and angled directly at the centre of the Primary mirror (the one at the bottom of the optical tube.

Look (search) for astro babys collimation guide (I'd post alink, but am about to go to bed). As an interim measure, you can follow the steps without the need for a collimator (costly kit, even a cheshire is 25 quid). A suitable cap over the open ended focuser will help, if it has a 1.5-2mm hole bored dead centre.

Like I say, read the guide, and be sure to do the work with theoptical tube horizontal, in case you drop something onto the primary mirror. And don't worry about cleaning any mirrors unless they are really boggin', and follow the cleaning mirrors advice, which is also around here somewhere.

[yeti monster]

I type too slow...........

[lighty89]

Thanks for the link, but, according to that, I will only be able to see Mars as a little dot:( Is that correct?

I will eventually get a better telescope when I'm a bit more into it all lol.

[lighty89]

And yes, the lenses came in plastic tubes, and yes, the lenses themselves are actually plastic!

If I was to buy one lens that I could use with a Barlow for a good view what do you recommend in mm's?

[Doc]

John is correct those eyepieces are a very basic design and in truth are rubbish.

The link below will give you skywatcher plossl eyepieces, these are a big step up on what you have but are still pretty cheap at about £20 each. I would say go for the 26 and 10mm ones.

http://firstlightoptics.com/proddetail.php?prod=SW_SP_super_plossl

The 26mm will give you a magnification of x27 and a field of view of 1.93°

The 10mm a magnification of x70 and a fov of 0.74°

Then later invest in a x2 barlow to double those figures.

[lighty89]

Will 70x give me some good views of say, Mars, or Saturn?

[Doc]

Through your scope Saturn will be small, at x70 you should see the rings but thats about it. You could add x2 barlow which will get you a little closer and you might see some banding on the planet. You should be able to detect at least 3 moons I would say as well.

Mars on the other hand will be very small and I doubt any detail will be made out, you might see a polar cap but alot of this is down to seeing conditions.

[lighty89]

Thanks for that info!

Is there actually anything I can see quite good with my telescope then?

Other than the moon lol?

[Doc]

Don't get me wrong Jupiter and Saturn will look good but will be small.

M42 will look really cool especially with the 26mm eyepiece giving a wider fov.

M31 will fit nicely onto the 26mm fov.

You might see bodes galaxy (M81&M82) if your skies are dark.

Again you might see M57 if you are lucky.

M36, 37 and 38 open clusters in Auriga will look good.

M45 the seven sisters will look great.

[lighty89]

So, a few things then, what are the "M"s are they Moons or constellations?

Also, is this EP any good?

ScopeTeknix Super Plössl Eyepieces (6.5mm, 10mm, 15mm, 20mm & 40mm)

[John]

Thanks for that info!

Is there actually anything I can see quite good with my telescope then?

Other than the moon lol?

You should see that Saturn has a ring system and see it's britest moon, Titan.

You can see Mars as a disk rather than a point of light as stars are.

Jupiter should show 2 faint belts around it's equator and 4 moons.

You should be able to make out the phases of Venus.

Open clusters like the Pleiades, the Beehive in Cancer and the double cluster in Perseus should look nice.

You will see some shape in M42, the Orion nebula and should be able to resolve the 4 stars of the Trapezium at it's heart.

So, yes, you can see some things if you are patient. I would get a guide on astronomy with binoculars. Your scope should show things a bit better than 50mm binoculars so that will be a bonus.

[Doc]

Yes those eyepieces are very similar to skywastcher plossls, and a step up from your Huygens eyepieces.

"M" stands for Messier after Charles Messier who listed all 110 Messier objects in the late 18th century.

[John]

So, a few things then, what are the "M"s are they Moons or constellations?

Also, is this EP any good?

ScopeTeknix Super Plössl Eyepieces (6.5mm, 10mm, 15mm, 20mm & 40mm)

M = Messier, the guy who catalogued many of the brighter deep sky objects.

Those eyepieces will be much better than the ones you have. Do phone the company to order + check stocks before ordering.

[John]

Look - we are falling over ourselves to help here so you get the same advice twice !!!

So you know it must be good :-)

[Cornelius Varley]

So, a few things then, what are the "M"s are they Moons or constellations?

Also, is this EP any good?

ScopeTeknix Super Plössl Eyepieces (6.5mm, 10mm, 15mm, 20mm & 40mm)

"M"s arer objects in the Messier catalogue and are a collection of different astronomical objects. M31 (Andromeda Galaxy) M42 (Orion Nebula) M45 (Pleiades) are three of the most popular in the list. Altogether there 110 objects in the list, galaxies, nebula and star clusters that Charles Messier catalogued in his search for comets.

Peter