information on eye pieces

[Beatlejuiceviv]

Hi all,

First timer, just joined the site. My brother gave me a 150mm refractor telescope. In the package came a  plossl 6.5mm AF50deg, also a plossl 25mm AF40deg and a 1.5X erecting eyepiece.

Still getting use to handling the telescope, lining up etc but can only use the 25mm on the Moon and Jupiter. Tried the 6.5 on Jupiter but couldn't really make anything out.

The erecting eye piece..cannot make sense of.

Question.

What am I doing wrong?

I have noticed when looking for fresh eyepieces that the mm either increases or decreases.

Question.

Please advise on the best eyepiece to view the Moon and Jupiter etc currently on the market.

Many thanks,

Viv.

[ronin]

Besides 150mm - diameter I presume, is there another value on the scope, probably around 1200mm, but could be about 800 to 1500.

That should be the focal length, that is needed, or at least useful.

I would forget the erecting eyepiece, they are meant for terrestrial viewing and can add problems when observing the sky.

Can you focus the 25mm eyepiece on the moon?

If so that is a start point.

Will ask now - is there anything else on the 25mm eyepiece?

I ask as a plossl should have an AF of 50 or 52 degrees not 40, so may not be a plossl.

To see Jupiter I suggest 80x and upwards.

As magnification is scope focal length divided by eyepiece focal length you/we need the scope focal length to get a suitable eyepiece.

[Beatlejuiceviv]

There is no more info on the scope so not sure what the focal length is.

Am I right in saying that to get this measurement you can measure the length of the scope and double it? If so then we make it a 1000mm.  Having said that  we've looked online and every 150mm diameter scope (which we've been told this is) we've seen has been 1400mm focal length.   

Yes I can focus on the Moon with the 25mm eyepiece which definitely says Plossl  AF40deg on it,

not that I have a clue what that means

Hope that all makes sense to you!

Thanks for your reply,

Viv.

[bingevader]

Hello Viv,

A bit more info would be useful, how about a pic?

You said a 150mm refractor, which would be quite a beasty of a refractor, but you wouldn't double the length of that 'scope to get the focal length as there'd be no mirrors involved.

Cheers

[ronin]

For the eyepiece I assume that it is a plossl but is stopped down internally to restrict the field of view, may sound odd but that would mean the edges are lost and the image appears better.

Scope wise, more confused.

You would seem to be saying the tube is about 500mm long, if that is the tube bit only and not including the focuser and diagonal then I guess it is an f/5 achromat similar to the Skywatcher Startravel 150 in design. Giving a focal length of 750mm. You don't double it - doubling one of the measurements is another property of mirror manufacture.

Assuming 750mm FL then you would need something like 8mm for Jupiter, about 94x.

For Saturn you need a bit more magnification as in 120x to 150x, that really means a 5mm eyepiece.

A plossl may be OK at 8mm but not really at 5mm.

Anything else at all on the scope body?

Anything engraved/written on the front of the scope around the lens when you look at the lens ?

What colour/colours is the tube ?

If it is an f/5 achromat at 150mm dia then there will be a reasonable amount of chromatic aberration on things like Jupiter and Saturn - basically faint coloured halos or edges to them, more apparent when looking at the moon.

[Cornelius Varley]

Does it look like one of these ? 

Seben Big Boss 150/1400. If it does then it is a short tube reflecting telescope with a focal length of 1400mm in in much shorter tube. 

[ronin]

I started to wonder if it was a reflector but the original says:

First timer, just joined the site. My brother gave me a 150mm refractor telescope. In the package came a  plossl 6.5mm AF50deg, also a plossl 25mm AF40deg and a 1.5X erecting eyepiece.

Unless they have mixed up refractor and reflector, they say refractor.

I would expect a refractor to have information on the tube and around the lens housing.

It is the absence of information I find most puzzling.

[hippie]

Hi Viv, The standard eye pieces that come with scopes are not that good generally the 25mm normally work!, But higher Mag ones don't,

Better eye pieces is your next route But which ones is how much you can afford really?,

Try & get along to local starparty's if you can Other fellow gazers will be only to pleased to let you look at differant EP's normally so you can see what suits you  . 

There are some BST starguider lenses @ £49.00 each from:-  http://www.ebay.co.uk/usr/skies_unlimited

These are good lenses for the money and Alan is very helpful if you have any questions, .

Hope this helps Ian.   

[Beatlejuiceviv]

Morning everyone,

Thanks so much for all the replies and rest assured that when I get the chance later today I shall get back with some answers for you.

Cheers,

Viv.

[rwilkey]

Hi Viv, your 150mm refractor is probably a 1200 focal length or thereabouts, which with the 25mm ep gives you 48x, and with the 6.5mm ep gives you 184x, which can be a bit on the high side for some recent viewing conditions, it should come to focus on objects like the Moon and Jupiter, so try it on something big and bright if you can!

[Beatlejuiceviv]

Evening all,

First of all, thank you for your replies.

Well done Cornelius Varley, that is exactly the one I have!!

So, now we have the correct scope and me being an absolute beginner,

what is the best eyepiece to view the planets?

Thank you all for your time and patience.

Viv.

[rwilkey]

Hi Viv, in my opinion the best ep for planets is the 8mm BST Explorer/StarGuider which will give you 175x, your scope therefore is a catadioptric newtonian and therefore has a barlow in the focuser to extend the focal legnth to 1400mm, not the best arrangement I might add, but OK for starters.  The BST is available here: http://www.ebay.co.uk/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.H0.Xbst+explorer&_nkw=bst+explorer&_sacat=0&_from=R40

[brantuk]

You may find this and interesting thread to read:

http://stargazerslounge.com/topic/56373-sebens-big-boss-1400mm-150-reflector/

Hth