Eyepieces for 10" dob, I'm lost !

[GasGiant]

Merry christmas guys n gals

Im lost ! 

Im looking to get maybe two or three eyepieces to match up with my 10" Dob.  It came with a 30mm Stellelyra and a 9mm plossl. 

There is such a vast array Im not really sure what I'm looking for.

So my main targets will be planets but I would also obviously like to look around at everything else too.

Am I right in saying that the smaller the number the MORE powerful the lens ?  Were as a larger number will give a wider field of view but have less sharp detail ? 

Can anyone recommend a set ?  Im not made of money so a mid range/quality, maybe ? lol 

Thank you

 

Carl 

 

[Spile]

I have the same 2” eyepiece as you and I pair in with a Baader Hyperion IV zoom. Take a look at the keenly priced and recommended Svbony equivalent as it gets lots of recommendations on here.

[Ricochet]

4 hours ago, GasGiant said:

Am I right in saying that the smaller the number the MORE powerful the lens ?

Yes. The magnification given by any particular combination of eyepiece and telescope can be found by

magnification = focal length (telescope) / focal length (eyepiece)

so the shorter the eyepiece the higher the magnification. 
 

4 hours ago, GasGiant said:

Were as a larger number will give a wider field of view but have less sharp detail ? 

If the apparent field of view (AFoV) of each eyepiece is the same then the true field of view (TFoV) will be larger in the eyepiece with the longer focal length. If the apparent fields of view are different then it may not be true. You can approximate the true field of view using 

TFoV = AFoV / magnification 

or substituting in the previous equation

TFoV = AFoV * FL(eyepiece) / FL(telescope)

Sharp detail is a lot more complicated as it is limited at low power by aberrations in your eye and diffraction at high power so you can’t say either high or low power is sharper. 

As for eyepiece suggestions I would suggest getting a DSO eyepiece that will give an exit pupil in the 2-3mm range which in your telescope means an eyepiece with a focal length in the 10-15mm range. 

For planetary a 1mm exit pupil is a good starting point, so a 5mm eyepiece, but this will give you 240x which may be above atmospheric limits some of the time so I would suggest a 7mm in addition to this. 

The 5/8/12mm BST Starguiders will work well in your scope and I believe the OVL Nirvanas excluding the 16mm will also work well in your scope so you could get the 5mm Starguider and the 7 and 13mm Nirvanas. 

Alternatively, the 3-8mm SvBony Zoom has been getting some good reviews recently, especially in the 5-8mm part of the range, so would work well for your planetary eyepiece and you could get this instead of the 5 and 7mm individual eyepieces. 

[Mr Spock]

If the scope has no tracking then you will need to 'nudge'. If that is the case I'd recommend as wide a field of view as possible. I have the Nirvanas and they are sharp edge to edge (not the 16mm which is poor) over 82° and comfortable to look through, so a 13mm and 7mm would seem ideal.

[GasGiant]

Thank you folks, very informative.

I think on balance I will go for the starguider lenses.  Having just done some quick research and seeing favourable reviews, I think at the point Im at now they will certainly match my expectations, and my budget ! 

I have popped some in my FLO basket as well as a barlow and will grab em on my birthday in Feb. 😀

Cheers folks

 

Carl