rw5373

@John Thank you for that link.... apologies - I did search this forum before posting but clearly didn't do a through enough job as I didn't find that post! Everyone else and John - thank you for such quick replies with advice. nice to find a friendly Internet forum! 🙂 Bobby

Just back from my first night out with my first ever telescope - Celestron Astromaster EQ 130. Super chuffed to have glimpsed Saturn.... but I have a question about eyepieces and what is 'normal'! The telescope came with 2 eyepieces - a 20mm 'Erecting' Eyepiece, and a 10mm (non-erecting) eyepiece. When I use the 20mm erecting eye piece - is it normal/correct that, when I look through it: - the image is not quite perfectly circular.... about one third of the circumference is slightly shadowed - as if the circumference of the image disc is being squashed slightly from one side - also - if I rotate the eyepiece within the eyepiece holder - I was expecting the image I saw just to circle around perfectly on its centre point.... like watching a disc spin... but it doesn't quite do this - the centre point seems slightly offset - so the as I rotate the eyepiece, the field of view of the image changes slightly - bringing in different parts of peripheral image that I can only see with the eyepiece in certain positions. When I use the 10mm eyepiece I don't see these same issues - the image is perfectly circular, and when I rotate the eyepiece the image spins around a central point like a disc. Is this something intentional about the design of the 20mm lens, or have I got a fault optic? As best I can tell the telescope mirrors are all aligned OK - but could the eyepiece be out of kilter? Thanks in advance fir any adivce Robert