New Person Needing Some Help!

[Button Moon]

Hello Everyone

As I'm new to astronomy AND my new telescope I was wondering if you could help with explaining a few things and giving some advice!

I apologise if this is basic stuff but i'm really just starting and don't know very much at all.

I'm really not sure what I'm doing with the eyepieces/lenses. I got 2 with my telescope 25mm and 10mm and a x2 deluxe Barlow lens (whatever that is??) Can someone explain what the different magnifications are, which is higher which is lower, and which ones are best for viewing what? Plus what a Barlow Lens is?

My telescope is a Skywatcher Skymax 127 Supatrak.

Thanks for your help I appreciate it!

[delilahtwinkle]

Hi Button Moon, I am a newbie aswell but have found a couple of things out by using my scope and also by asking. Here goes, I have found out that the lower number on the eyepiece means higher magnification, and that if you put the Barlow in first then the eyepiece it will double your magification. On my first night I used the 10mm to look at the moon and it was too close so I put in the 25mm and it was great, but the 25mm is great for the stars etc. Maybe what I am saying is pants but it is what I seem to have experienced, I am going to keep an eye on this post to get some advice myself. Hope I have helped a little. Regards Delilahtwinkle (Dt)

[Psychobilly]

Yep thats about right

Start with the 25mm on its own it will give you the widest FOV and lowest mag, then put the 25mm in the x2 barlow to give you an effective 12.5mm EP then change to the 10mm on its own and finally to the 10mm with the x2 to give you an effective 5mm EP.

Short focal Lents require clear stable skies you'll often get a better view at lower magnification.

Why am I talking about EP's ... i might start using them if I am not careful...

[SteveP]

Button

Exactly what you've been told previously!

To add a few more details ....I think your scope has a focal length of 1500mm. Think of that as how far the light has to travel from entering your scope before it reaches focus. Eyepieces also have a focal length. That's what the 10mm and the 25mm means. The overall magnification of your scope and EP together is calculated as the focal length of the scope divided by the FL of the EP. eg for 10mm EP, it's 1500/10 = 150times. For the 25mm, it's 60times. That's why the moon looked bigger in the 10mm ... sorry, don't mean to be condescending

As you can see, magnification has nothing whatsoever to do with the aperture (opening) of the scope

[AWR]

Magnification = Telescope focal length / EP focal length

With your telescope (1500mm focal length):

The 25mm eyepiece will give 60x magnification and a field of view of just less than 1 degree

The 10mm eyepiece will give 150x magnification and a field of view of about 1/3 of a degree

The barlow will double the magnification (and halve the field of view)

You'll probably find that 300x is a bit too much (like zooming in on a digital photo - you don't really see any more detail)

As has been said - the 25mm will give the best view of clusters and objects such as the Orion nebula

The small eyepiece is better for planets or splitting double stars

HTH

Andrew

PS - Buy "Turn Left at Orion" by Guy Consolmagno

[delilahtwinkle]

My scope is a little 130p Skywatcher... on the side it says D=130mm F=650mm. So does that mean that if I do 650mm/10mm eyepiece I get x65??? If this is right, is this really the lowest I could go?? Getting confused... sorry.. Dt

[SteveP]

DT

Yep, the 10mm will give you a mag of 65x. If you have an ep of 5mm,then the mag will increase to 130x. Alternatively, a 2x Barlow used with your 10mm will also double the mag to 130x

Still confused?

[delilahtwinkle]

Also when I was looking at the moon I had my 10mm and my 2x barlow so was that really a view from a 5mm???

[delilahtwinkle]

When I viewed Saturn yesterday, I used my 25mm and 2x Barlow

[delilahtwinkle]

Hiya Steve P. Understand it now... I think...When I viewed Saturn yesterday, I used my 25mm and 2x Barlow it was great but still quite small, is there any way that I can make it larger or was my scope be at it's max. Should I get a 3x Barlow instead of buying new eyepieces, using the ones supplied with the scope.

[AWR]

I had my 10mm and my 2x barlow so was that really a view from a 5mm?

Yes, that's right

If this is right, is this really the lowest I could go??

I haven't found much use for anything less than my 15mm (100x) EP yet. (in my huge and vast astronomical experience ) The 10mm reduces the field of view but doesn't show me any more detail (this is probably because it's the cheapy supplied with EP).

Andrew

[delilahtwinkle]

I think I am going to save up and buy a couple even if they are one's I have just to see if there is any difference... I think a call to FLO will be made in the morning. Just put my scope outside to get ready for the night. Will we see the ISS and Discovery going over tonight??

[AWR]

My 15mm is a Plossl from Vixen (about £35) and it is definitely a step up from the EPs supplied with the scope - I get much sharper images. Have a look at some of the threads regarding EPs on here (that's what I did). From memory; Vixen, Meade and TAL were all recommended at this price.

Andrew

[SteveP]

DT

There are lots of reasons why the image of saturn may not look any better with a different EP but generally you will get a larger image by using a 'smaller' EP or a Barlow. So have a try with your 10mm. You'll have a bigger image but you may lose some detail. Then try your 10mm with your Barlow ...

The usual problem is that as you get a larger image, the quality deteriorates. Think of it as all the little photons being spread over a larger image and therefore diluting the quality.

Equally, there are some rules of thumb about maximum magnification. For example, most 'experts' suggest that the max mag shouls be 40-50x the aperture in inches. So in your case, with a 3" scope like yours, the best you'll ever get is 120-150x .. and that would be with very good skies! A practical limit might be closer to 100x

Does that help you some more?

[Whippy]

One of the problems every stargazer faces is atmospheric conditions. I'm sure you know the basic rule of thumb for maximum magnification is the aperture of your scope in millimetres doubled right? Problem is that the sky will rarely allow you to crank up the magnification to that extent.

If your scope's theoretical maximum is say, x260 there will only be maybe a couple of nights per year that the conditions will allow good views over about x180 - x200. Do you want to keep an eyepiece for those nights or perhaps get something in a longer focal length that you could use a lot more and have a Barlow for those 'special' nights when it's clear, dry and steady?

Personally, I'm not a huge fan of barlows because you're adding more glass into the optical train which I think reduces the amount of light hitting your eye. Other people find Barlows great, it saves them buying loads of eyepieces.

Tony..

[SteveP]

DT

Apologies but I may have added to your confusion. Your scope is closer to 5", not 3". So the max mag would be about 250x but more likely closer to 200x in normal conditions

[Button Moon]

Hiya!

Thanks for your help I understand a little bit better now. What other lower eyepieces do they do below 10mm? And what makes are the best to buy?

Steve P - my focal length IS 1500mm

Andrew - thanks for the tip about the book I might get that

Also I'm having trouble putting my barlow lens into my diagonal so I can put an eyepiece into it. Am I doing something wrong? It's like it too big!

[starman69]

I've used these kind of sites before:

Eyepiece Calculator

Good way to play with the combos.