Lenses for planetary observing?

[philipw]

I had my first night out with my New 200p dob this week, beautiful clear night, so much to see!

Would appreciate some advice on buying a new lens for planetary obs, a 6mm I think? Have £50 to spend. I am unfamiliar with various makes so would appreciate pointing into e right direction for a good quality eyepiece.

Thank you

[LouisJB]

BST starguider 6mm maybe?

[stevend]

Depending on conditions where you live I might consider an 8mm BST (150x) as I find 200x, albeit with my 127 Mak, to often be at the limit. Though it is probably best to wait for other Dobs users to advise.

[philipw]

The starguider has been recommended previously.

I'm in central london, so a faint amount of LP slough my garden backs onto a cemetery so not a lot of very local light.

[Mr Spock]

I'd go for the BST 6mm. It's the best you'll get at that budget and you'll need x200 to get the fine detail your scope is capable of.

[Zuben Elgenubi]

The 8mm Starguider/Explorer is a popular eyepiece, unfortunately they don't make a 6mm. The 5mm would give you 240x with your 200P dob, perhaps a bit too much magnification for most nights.

A 6mm is a lot more useful though. I bought a 6mm TS HR Planetary which is good value. It is a clone of the TMB design and available from Modern Astronomy, priced the same as a BST. The William Optics SPL also seems to have quite a few fans, although it does exceed you budget.

These EPs offer fairly generous eye relief - if you are comfortable with you eye closer to the EP then you can also look at Plossls and orthoscopics for high quality planetary views.

[philipw]

Thanks.

There's a lossless 6mm for £25 on fleabay. Worth the money?

[NGC 1502]

Depending on conditions where you live I might consider an 8mm BST (150x) as I find 200x, albeit with my 127 Mak, to often be at the limit. Though it is probably best to wait for other Dobs users to advise.

I'd agree with that.  But you are likely to get varied and genuine advice.

On Thursday night I was out observing with my 10" Dob.  The scope was well cooled and collimated.  Of course Jupiter was a prime target, just after opposition and high in the south.  The seeing was fairly steady and I tried 200 & 240x.  At times the atmosphere was steady enough for a good view, but I dropped down to 170x then 150x, because the view was consistently crisp at those powers.

A smaller and sharper view trumps larger and fuzzier.   Not saying an 8" Dob cannot be good at 200x and over, I'm certain it can, but I do think that around 150x would be more useful more often, and of course easier to track with a manual Dob if you keep the power down a bit.

This is only my opinion of course, so see what others say, not just me, before you spend your money.

Regards, Ed.

[Zuben Elgenubi]

A smaller and sharper view trumps larger and fuzzier.   Not saying an 8" Dob cannot be good at 200x and over, I'm certain it can, but I do think that around 150x would be more useful more often, and of course easier to track with a manual Dob if you keep the power down a bit.

This is a very good point. An 8mm eyepiece would be a lot more versatile and you would almost certainly get more use from it. Perhaps that would be a better first purchase? You could always add a 6mm later on if you felt you would use it.

[LouisJB]

I also recommend the 7mm Celestron X-cell LX, between the 6 and the 8, little bit more money but adjustable eye relief is nice. I think they're all decent and an improvement on kit Plossls for the $$. Staying at or below 200x probably means you'll get to use it more, otherwise it's going to be very seeing critical. A smaller sharp view of Jupiter in the context of its moons is a really nice sight, a larger fuzzier image less so I doubt you'd be disappointed with any choices. But if you go 7 or 8mm you might also x2 or x1.5 barlow it occassionally, on a good night, whereas at 6mm or 5mm barlowed would be too much to be useful only rarely, if ever.

[philipw]

Ok, I hate shopping. Too much choice makes me want to hide in a pub for the day.

I want to buy something, but now not sure about 6mm. 8mm may be a better first step? Or shall I just get both!

[cotterless45]

Try the excellent flat field 8mm ep from skys the limit. It works well at f5/f6 and gives sharp views across the fov. This will give you a handy x150, most nights in this country , that will surfice.

The very best 6mm that I use is a 6mm Antares Plossl. Silly cheap and gives razor views. I also use a cheap UHC filter on Jupiter to take down the glare. Also great on nebulae,

Nick.

[LouisJB]

great advice there... Good tip on the UHC filter too, might try that myself, Jupiter often looks bright and glarey to me.