Focusing

[Comet71210]

Hi, I recently bought a celestron astromaster 130eq and bought a lens kit to go with it, it included a x2 barlow lens and a 6mm plossl eyepiece and I've been getting some great views of Saturn the past couple of nights with the other lens' but focusing seems somewhat impossible with these two, could it be that the magnification of these to combined are too powerful for my 5 inch scope? Any help would be most appreciated, thanks in advance.

[Charic]

You need very good  seeing conditions to get the best from your telescope, also check out page 27 of your manual to ensure that the telescope is properly collimated?
Your right about the issue of magnification, too much can be an issue? Your scope has a focal length of  650mm, divide that by the focal length of the eyepiece 6mm and you get 108x power/mag and because your using a Barlow, the telescope focal length is now effectively 1300mm,  giving 216x power.  The telescopes focal length is increased by the factor  of the Barlow, so a 3x  Barlow would give you a telescope that is now effectively 1950mm, 325x power Ouch!  but whatever the telescopes focal length, you divide that by the eyepiece to achieve the sum of the magnification / power of the telescope. 
If your seeing conditions are good to better,   from a suitably dark place, with your eyes  dark adapted to the conditions, with the scope cooled to the ambient temperature  and collimated, you should do well at 130x power to  twice that of the aperture, so up-to, effectively 260x,  which suggests the 6mm Plössl/Barlow combination should work, providing all other conditions are met.
 I have a 127EQ Powerseeker (similar setup) which taught me a few things, but have  opted for the simplicity and larger aperture with  my present scope. Make the most of what you have, follow the instructions in the manual provided, hope for good nights of seeing and if possible the darker the place ( away from man-made light pollution ) the better, until the urge to upgrade defeats you.

Welcome to the SGL.

[Ricochet]

As a general rule of thumb the atmospheric conditions in the UK tend to limit us to ~200X magnification. As Charic has calculated, your 2X Barow and 6mm combination is above this so it is likely that you will only get good results from this combination on good nights and will often have to drop down a notch to match the conditions. It would not surprise me if the conditions in Manchester make even this figure optimistic.

In addition to the general atmospheric limit you should also pay attention to the atmosphere in two more locations that will further degrade your view. The first is the atmosphere close to the ground. Earth and vegetation radiate heat away quickly so at night they are relatively cold and the air close to the ground is stable. On the other hand the materials we build our towns and cities with hold on to the heat during the day and release it at night which is detrimental to the views. Buildings that we actively heat are even worse offenders so if possible observe over fields and gardens, tarmac if needed and over houses only as a last resort. Even waiting for an object to move over the gap between two houses will have a significant effect.

The second location you need to consider is inside the scope itself. Your mirror needs to cool down to match the atmosphere or else currents in the tube will be the limiting factor. If you store your scope inside then I think the general rule is to allow 10 minutes of cooling per inch, so 50 minutes for your 5 inch scope. If you store your scope in an unheated shed or garage then this time will be reduced. You can either get your scope out early in preparation for observing or just start by observing at low powers until your scope has had time to acclimatise.

[Louis D]

Have you tried the 2x barlow with any other longer focal length eyepieces to eliminate the possibility that you simply can't come to focus with a barlow in your scope?  What other eyepieces do you have?  Work your up from longest focal length to shortest and note what happens to the image along the way.  Does the image get larger but fuzzier?  If so, you're better off going back to a lower power combination for the night on that particular target.

[wimvb]

Add to the above:

A shorter eyepiece not only magnifies the target more, it also magnifies deficiencies more. Any abberation, coma, or what ever optical shortcoming, is magnified. Sometimes the eye is more forgiving if the magnification is less. The highest usable magnification for your kit is specified as 150x, according to Celestron. With the barlow and 6 mm eyepiece, you're way above this limit.

To know whether you can or can't reach focus; if you find that when you move the eyepiece in one direction (in or out) that you pass a point where the target is least fuzzy, then this is your focal point. If the image isn't sharp at this point, it is due to either seeing or optical effects, vibrations, heat currents, etc

[LukeSkywatcher]

With your set-up, i'd say its a combination of too high a magnification and local atmospheric conditions. 

[Comet71210]

Thankyou all for your advice and input, i have a 25mm, 15mm, 10mm a 6mm and the Barlow lens I also have a few filters, I have used all the eyepieces with the Barlow and the all work perfectly when looking at the moon aswel as the Barlow with the 6mm, being new to astronomy I didn't account for seeing conditions and think this could have been the problem as Saturn was close to the horizon at the time, my area hasn't really had any good clear nights to be able to see much more 

[Louis D]

Glad you got it all worked out.  Here's hoping you get some good, clear nights to observe.