Skywatcher Planetary EPs

[Watchman]

Just a couple of quid cheaper than TMB IIs, are they any good? If not, what is the better option? I dont want to spend more than £40 on an EP at the moment but want something in the 7mm range (that I can barlow to 3.5) for looking at planets, particularly Jupiter and Saturn when they show their faces Later I will get a low power Ep for deep space and so on.

Thanks in advance as ever

[Northern Soul man]

Hi Ya Watchman, You could probably get away with around the 9 - 12mm EP focal length for the time being as this will probably be about the highest Mag you can use for the best object size for the given Mag for any given night with probably average seeing - some nights you may be able to go a little higher - but you could probably count the best nights of seeing out of the whole year on one hand - I think we get very few nights of the best seeing for planetary detail - not so much for DSO's, but for Planetary and Luna you could probably get away with around this range - any higher and the detail becomes really poor - the image size of each planet will be larger, but at the cost of detail.  I try to use a lower power - say around a 17mm EP to judge the seeing, then may increase to around the 12mm EP and try to see if I can see the same detail, but alot depends on several factors which are, Planet size (in arc seconds), height of the planet above the horizon, cooled optics and local seeing - all these factors need to be looked at to get the best out of our EP's.

As you can see, we are only going to get a few nights when all these factors are at their best to get the best out of each Planet - I think that's why we go out and set up night after night (when its clear - not many of these nights in a row!!)

Hope that helps a little Watchman - you can see its more to do with a lot of the factors falling into place more so than trying to increase Mag.

Paul.

[Dave In Vermont]

You might be able to push the magnification up to 200X on the rare night of excellent seeing with your scope at ambient temperature. This would translate to a 6mm EP in your 1200mm F/5.93 scope. But it would be a rare night as stated. Your Dob is at what I call the 'sweet-spot' where it will do quite well on planetary, as well as on DSO's. With a 200+mm aperture, you can pull in the vast majority of commonly sought objects - enough to keep most folks going for a lifetime.

Clear & Excellent Skies,

Dave

[craigfoot]

I've been considering getting the 4mm planetary, to use with my skywatcher 130. But gonna wait a few more months til the planets are up. . .though reading this makes me wonder if I should bother?

[John]

I found that 200x was pretty commonly used when I had the 200P dobsonian. I'm frequently using 200x-250x on the moon and planets with my ED120mm refractor. My observing conditions are fairly standard for a back garden I'd have thought.

[Watchman]

My bad, sorry. I don'thave the 200p anymore, I have been the rare exception that has scaled DOWN, I am about to buy a Skywatcher Explorer 130p on an EQ2 mount.  Simply put, I'd rather have a smaller scope I use a lot than a (excellent) large scope that I can't transport easily.  The 200p dob is superb, but I simply couldn't travel easily with it.

What I am really asking is - are the skywatcher uwa planetary EPs actually in the same league as say TMB IIs or BSTs? Cost is simply the main factor, with the SW being £37, the TMB IIs at £39 and BSTs at £49.  So it's really between the SW's or the TMB II's.

I have changed my sig as I forgot it said I have the old 200p..

[Watchman]

Well. I've ordered a SW uwa 7mm planetary so I'll let you know how that goes once it arrives and the obligatory clouds clear:)