Newbie requires scope help/advice please

[Killer]

Help! I'm totally new to astronomy and as tonight was the first clear sky since I bought my Meade ETX125PE, I gave it a runout. I used the Goto option and it took me to Vega and then Arcturus.

I used the 26mm eyepiece. When I focussed on Vega I saw a circle of white with a black centre - it looked quite a lot like a polo mint. I got exactly the same when I focussed in on Arcturus. There was one point when I thought it could have been the reflection of my iris! I know I was looking at SOMETHING in the night sky, because I slewed away from the object and saw nothing but darkness.

Is this how these two objects should have looked, or is there something fundamental I'm doing wrong?

Annoyingly there was a clear, bright moon tonight too, but it was low in the sky and was obscured by some pesky trees at the back of our garden, so I didn't get to try the scope out on it.

Any help or advice would be most welcome.

TIA

Killer / Steve

[ottUp]

No, that's not how they should look.

When a star appears as a ring of light with a dark centre, that means you are not in focus. We do this deliberately for a type of optical adjustment test; but in normal observing situations, stars should be pinpoints of light with almost zero diameter, and no dark centre. (When you say "I focused on Arcturus", I'm guessing you mean "I pointed at Arcturus").

(The dark centre is the reflection of the secondary mirror, glued to the back of the main lens at the front of the telescope.)

You need to adjust the focus knob on your telescope until the stars become pinpoints of light. If you run the focus knob through the entire range and cannot get the stars to be pinpoints, something is wrong - chances are you have omitted an optical element or have something in the wrong order. Try to find the focus point and if you can't, report back with a description of how your components are assembled.

Good luck

Richard

Ottawa

[Killer]

Hi Richard

Thanks for the quick response - what you've said makes perfect sense, I should have realised that what I was seeing looked too much like the mirror! And you're right, I did POINT at Vega and Arcturus, not necessarily focus on them. Having said that, I did adjust the focus knob and had them as pinpoints of light, but didn't realise that that was the correct view.

So when I've got them as pinpoints of light with the 26mm eyepiece, I can try a higher magnification eyepiece (lower number?) and should see the objects closer-up?

Thanks again,

Steve

[ottUp]

Hi steve.

Glad everything is working. Try higher power, by all means - but you may be surprised what happens. Stars will remain pinpoints of light - they are so far away that no amount of magnification you can apply will make them non-pinpoints.

We generally use higher magnification for:

- Planets and moon, which *do* respond to magnification by getting bigger; and

- Multiple stars (e.g. point at Albireo in Cygnus. Magnification reveals it to be a double star with a beautiful colour contrast)

- Some clusters of stars and some nebulae are better under moderate magnification.

This page shows simulations of the effect of increasing magnification while looking at the multiple star system Alcor/Mizar in the Plough:

http://www.themcdonalds.net/richard/astro/find/mizar.shtml

All that said, you'll probably find you use your lowest-magnification eyepiece the most, next lowest the next, and so on. High magnification is useful only in rare cases and on rare nights of perfect seeing (except for the moon and planets, which always benefit from some mag). Low magnification lets you look at large objects (star clusters, galaxies, nebulae) and see them in the context of the surrounding stars, and it also makes the things in your field of view brighter and easier to see.

Regards

Richard

[Vega]

Not much I can add really as Richard has covered it well. One thing I would say is dont be disheartened by the apparent lack of 'eye candy' up in the sky at the moment. June is the worst month of the year for astronomy due to the light nights (the sky doesn't reach true darkness all month). There will be plenty up there to hunt down by August .

Re: The Moon

You mention the bright full moon. Its a common misconception when starting out that the full moon might be the best moon phase to look through a scope but it's actually the worst. During full moon, most of the surface detail is 'washed out'. Best time to view the moon through a telescope is around half moon when shadows are cast across the craters and smooth seas. The views are stunning .

Enjoy your new hobby!

Matt

[Killer]

Thanks both for your replies - this is all part of my learning curve. I've joined a club, so hoping to get lots of tips from there as well.

Cheers

Steve

[barkis]

Hi. Steve,

I would just like to say without wishing to upset you at all, that since you have indicated a little inexperience in your posts I feel a warning about the sun is in order. The warning being that you must NEVER POINT ANY OPTICAL DEVICE AT THE SUN. IT WILL BLIND YOU.

You might already be aware that that danger exists, but nevertheless, I had to remind you of it.

You will soon get to grips with your scope and enjoy it to the full I am sure.

And any more help you need just ask away mate

[Killer]

Hi Barkis

Thanks for that advice - it is mentioned on the Meade's documents and there's a sticker on the scope too, but any advice/help's welcome, no offence taken at all. I need all the help I can get! I reckon I'm gonna be loving it though.

Cheers

Steve

[barkis]

Hi Barkis

Thanks for that advice - it is mentioned on the Meade's documents and there's a sticker on the scope too, but any advice/help's welcome, no offence taken at all. I need all the help I can get! I reckon I'm gonna be loving it though.

Cheers

Steve

Yeah! you are going to love it, especially in the later months when the sky gets dark enough, and hopefully clear enough , to see lots of the wonderful sights in the universe.

Also, if you can get to the ocassional star party SGL organize now and again, get to meet other members, look through other scopes, and generally have a great time.

Best Wishes mate.

Ron.

[Casus belli]

I have the little brother to your scope (ETX 90) and its a fine scope. I find it really good for planetary views and for the moon. Its also quite good for binary stars. I did hate the go-to but after reading the manual it was more due to my stupidity than any fault with the scope.

Handy place for accessories

http://www.astro-engineering.com/

The fleximate focuser is quite handy especially if you plan on photography