TMB planetary eyepiece.

[cosmic dave]

I bought a 6mm tmb planetary eyepiece from kelling last year and I have found it great to work with. But does anyone know what the most powerful piece I should get if I was to get another ? I was thinking of getting a 4 or 5 mm, I use a 90mm skywatcher f9 refractor and also have an 8 inch orion reflector.

[russ]

I would say the 5mm. It gives 180x in the Evostar, which should be within its limits. The 4mm would push it too far.

You don't say which focal ratio Orion you have, the f4.5 or f6. If it's the f6, the 5mm will give a very handy 240x for good nights. If it's the f4.5 the power will be the same as the Evostar, a nice 180x. Useable most nights of the year.

[cosmic dave]

I would say the 5mm. It gives 180x in the Evostar, which should be within its limits. The 4mm would push it too far.

You don't say which focal ratio Orion you have, the f4.5 or f6. If it's the f6, the 5mm will give a very handy 240x for good nights. If it's the f4.5 the power will be the same as the Evostar, a nice 180x. Useable most nights of the year.

Its f6 :hello2:so should be great with the planets.

[Ben Ritchie]

I agree with Russ, 5mm would be a good next pick - might then be worth looking out for a 4mm used (about £30 for a Sky's the limit one) which will deliver on those rare nights of great seeing, but the 5mm will get more regular use.

[Supay]

Didn't want to create a new topic for a very similar question. I have a skywatcher explorer 200p and am picking up some new eyepieces. My girlfriend has really enjoyed seeing the planets and moon closeups and getting a high power EP to get a better look at these will both entertain me and ease my attempts at later purchases!

I was considering picking up a 5km ED or TMB from sky's the limit, however I was also wondering whether a 4 or 3.2mm would be a worthwhile investment?

The scope seems well known, but just for reference it is f/5 and 1000nm focal length with a 200nm aperture. I currently only have the supplied 10nm and 25mm, hence my desire to upgrade.

Does anyone have any experience or confirmed knowledge of those shorter focal lengths on my scope please?

[Ben Ritchie]

Does anyone have any experience or confirmed knowledge of those shorter focal lengths on my scope please?

On my 1040mm focal-length 'scope I find I use a 5mm quite regularly, a 4mm occasionally and the 3.2mm TMB very rarely - to the extent that if I didn't also own a short focal length refractor there would be little point in keeping the 3.2mm.

So I suspect that would be similar for your 200p - the 5mm is a great buy and will get regular use, shorter focal lengths less so. Depending on your budget and willingness to own 'occasional use' eyepieces, it might be worth getting something with a longer focal length instead.

[Supay]

Please ignore my daft phone randomly replacing mm with nm or km as it decides is best, I sadly do not possess such an obscurely sized scope.