Eyepieces

[tomys]

I have read The Warthog's thread about what I need for eyepieces, but I only have ones marked H and SR, which came with the telescope and I am also not sure about his post. What exactly do I need? Which mark would represent the best type of eyepiece? I have a 4" reflector dobsonion and a focal length of 700mm for the telescope.

Thanks in advance!

[yeti monster]

Hi tomys,

I use Sky Rover, being in HK, you should have no problem getting them sent to you.

SKY ROVER WA??

I'd recommend the WAs as they are superior to the ones generally supplied with scopes, reasonably priced and are happy with f6 and slower, they even do quite well in my f4 10" scope.

[tomys]

Thanks! I will ask my father about getting the new eyepieces.

YAY!

[Moonshane]

as with many things it's down to budget. there are decent cheaper eyepieces which will be a big step up from your current eyepieces and there are units costing £600+ which would not be feasible in your scope due to weight etc.

my advice would be take note of the article you mention - it's excellent and provides a good basis for a set up.

you can either use a (decent quality) barlow which is like a 2x magnifier and therefore doubles the scope of your collection - eg if you had a 25mm and a 10mm the barlow would effectively give you a 25mm, a 12.5mm, a 10mm and a 5mm.

OR buy individual eyepieces - I am going down this route. it's more costly but some say worth it in the long run.

if you can afford about £35 per eyepiece, then I'd recommend the Paradigm / Discovery or the TMB eyepieces on Ebay from the same seller. I would not normally recommend Ebay unless you are careful. This forum offers a for sale section after 50 posts. I buy all my eyepieces used.

the attached confirms the magnifications for your scope for some more common eyepieces. I hope it's useful - my estimate would suggest a maximum magnification using a 5mm eyepiece but you might get away with a little more occasionally.

Initially I'd suggest you buy eg one of the above and see if you like it, then either get another per the article or a good barlow etc.

good luck!

lenses.pdf

[tomys]

Thanks Moonshane for that document because I never knew aperture was just the inner diameter of the tube in mm. That means I have a f/7 scope! Never knew it was so good. Now I need some really lucky googling, or maybe check the forum's part on buying stuff.

BTW, how did you get that really nice shot of the moon?

[Moonshane]

no worries - the moon was taken with my refractor - see below - and a basic attachment to my point and press camera. it's surprising the results you can get (of the moon only) with literally just holding the camera to the eyepiece - try it with your scope, you might be surprised.

technically, aperture is the diameter of the main mirror or lens. focal length is the distance from the main mirror to where the eyepiece focuses and focal ratio (f7) is focal length divided by aperture. I usually work on 1.5x aperture in mm for maximum magnification for most applications.

[tomys]

I tried it, it is supposed to be my profile picture, but its still the old one. Attached is mine. :/

[Moonshane]

I used a low magnification eyepiece and then cropped it a little. yours looks quite grainy. did you use a low resolution? in an 'arty' way I quite like it!

[tomys]

maybe its just that my camera totally does not fit my tiny eyepiece hole. I mean using afocal the hole is still too small.