Eyepiece and Maximum Mag

[BigJock2005]

Dear All,

After spadeloads of research (much of it on this wonderful forum) I am about to invest in probably three decent quality eyepieces. I'll post my decisions on here for comment before I take the plunge.

But one very stupid (but simple!) question before I make my decisions... I am told by many people that in the UK you can rarely go beyond 200-250X mag as the atmospheric conditions just won't permit. I have an SW 200P scope which has a focal length of 1000mm. I have successully used the 10mm EP that came with it, and even put it on the end of the Barlow (that also came with it) focusing in on the rings of Jupiter successfully. Focusing is diffcult with the 10mm + Barlow however.

This should (I think) be giving in a mag of 200X (400X with Barlow). Given that these are very mediorcre quality EPs (they retail sub £20 and the Barlow gets very poor reviews) I would expect better results with better quality EPs.

But my question is this: is it a waste of time going down to a 5mm good quality EP on this scope in the UK? This would go straight to 200X mag, and obviously 400X with the Barlow - and that's the highest recommended on this speed of scope.

Thanks for any comments.

Jock

[John]

With a decent 8" scope I think 200x and 250x are useful "tools" to have in your armory. Jupiter will look better at 200x generally as it does not tend to "take" high power as well as, say, Saturn and the Moon. I find I use 250x quite often with my ED120 refractor actually. 

So, no, it's not a waste of time or money in my opinion.

[crashtestdummy]

As you say,it's hard to focus with the 10mm and with the experience of the same scope I went down to a 9mm and had the same problems.I would say replace the standard focuser with a duel speed one to make focusing easier then you may be able to go down to a 7mm on good occasions.

Conditions are rarely good enough to use my 9mm in my 1829fl scope but I have it for when it is

[brantuk]

My 5mm barely comes out to play with UK skies the way they are - but when it does it's a rare treat. The idea of a d/s focuser is sound - or you can upgrade the existing one with the Lacerta 10:1 kit which I quite like (cos it works and it's cheaper):

http://www.365astronomy.com/dual-speed-110-microfocus-upgrade-kit-for-skywatcher-crayford-focusers-p-2484.html

If however you barlow a 10mm then a decent eyepiece and a good quality barlow will be necessary and much more satisfying - and it leaves you with a good 10mm you can use most any time on it's own. But it's generally better if you use the least possible glass in the light path.

The best I can suggest is if you join a local observing group or astro soc and go out observing with them. You'll find most folks happy enough to lend you a better eyepiece to try out in your scope - that'll help you decide which eyepieces suit you and what sort of price range to aim at. £30 to £50 per eyepiece will make a marked difference with your 200P.

[ronin]

I find saying 3 eyepieces difficult as there is at the higher end no sort of leeway.

On your scope 1000mm an f/5 I would normally say: 5mm, 7mm 12mm and 25mm - this is assuming eyepieces with a 60 or greater degree of view. If plossl's then get a 30/32 in place of the 25mm. But a 5mm plossl is a waste of time.

The 5mm is for when conditions are good enough that it works, and it will at times, the 7mm is for the other times, likely most more of the time. 12mm for medium power and 25m for wide. To my thinking this covers all the options you are likely to encounter, or at least 98% of them.

One concern is that when Mars makes a decent appearance people will be using 250x and above to see it.

The lengths are from the Celestron X-Cel range, in the BST it would be 5mm, 8mm, 12mm and 25mm.

In either I suppose 12mm and a 15mm are swapable depending on which appeals most.

But as I say 4 not 3 eyepieces.

[bingevader]

Try before you buy would be good if possible.

On Jupiter, 200x is good for me, but it is dependent on the conditions. I have an EP to take me up to 240x and that's fab when I can use it, but it's not every time. Lately though I've been dropping back to 172x and I'm looking at the possibility of dropping back a bit further (8mm for me). Having said that, things were so bad the other night (first dry night in weeks!) that Jupiter wasn't sharp through any EP!

As John has said Saturn and the Moon in particular will take more magnification, so if they're likely to appeal to you, then no, 200x wouldn't be a waste of time.

Sticking a barlow on it may have limited use though!   As you have said, 400x is supposedly the theoretical limit of magnification for an 8" 'scope. For fun, I've tried my 5mm and 6mm with a 2x barlow (480x and 400x!) on the moon. The 5mm was dark and predominantly floaters in my eye and dust on the EP, there was a moon somewhere behind all the detritus! The 6mm was dim and focus was close, but no cigar. A little step back might just have done it (hence the possibility of the 8mm).

This is all dependent on what seeing conditions are like at your site and only you'll be able to assess that for yourself over time.

Cheers

[AlexB67]

In my scope, a 10 inch Dob, I think 7mm would be excellent middle ground a l lot of the time for Jupiter at around 170x. I use 8mm to give me 150x and often think it is little bit low, and 200x a bit high on a lot of evenings when seeing is okay but not great. I have set aside the 7mm slot for a pentax XW so  I do no want to break the bank on a 6mm that close to it, but I would use 200x for sure, sometimes I go higher mag for brief periods under very good seeing with some combo using my 1.5x optional barlow element on the 2x barlow with what I have currently.

In my case I'll probably invest in a 6mm orthoscopic at some point, may be soon before the pentax before Jupiter goes away for the season. Also the ortho would be good for doubles,  but I expect it is not an eyepiece I'd not want to use everyday with a taxing tiny peep hole and short eyerelief and will require more nudging. Having said that, I tend to nudge a lot with the 8mm anyway, since I find planet detail is retained better nearer the centre of the view in that eyepiece, so in effect I am only using half the FOV of it anyway these days.  The pentax will be that more soothing and relaxing to use on other days when I don't feel like doing that so much.  Depending on how you feel on the nudging versus comfort of wider FOV you could save yourself quite a bit on the wallet for good optical quality and get great views for < 100 pounds 

[BigJock2005]

As always, thanks for the comments. I really like the suggestion of the dual focuser - I didn't think of that. And I'm clearer about mag limits too.

Although when I said 3 EPs, I really meant 3 fixed EPs as I really like the idea of a moderate quality zoom for estimating the best focus for viewing on any given particular occasion. The quality varies tremendously in my back garden - from poor and highly polluted (fiter on its way) down to very dark on some cold nights after around 11pm.

I'll think about this, and post my proposed selection - should give a few conundrums!

Thanks again.

[crashtestdummy]

One of the 8-24 zooms would do the jib of all 3 to some extent but it's the same with a zoom camera lens,it's never as good as a few primes

[BigJock2005]

Thanks for the link, the Lacerta kit looks good, and pretty easy to fit! It is cheaper at £56 than a dual-speed Crayford, plus, I guess if you replace the focuser then the scope needs to be recolimated? Shouldn't be necessary with the Lacerta as the focuser is not moved at all from its axis.

After all this advice, I think I will go for a i) a 5 or 7mm, ii) a 10 or 12mm, and iii) an 18 or 20mm, and then finally a zoom. Final choice will depend on price/quality balance, eye relief, FOV and then design/construction/sturdiness. Watch this space...

[David55]

Sorry I'm a bit late to this, but I have the Skywatcher 200p skyliner which is an F6. I have found the following combination the best. A 2" Skywatcher Panaview 32mm wide angle (x40), this gives fabulous wide field views and is my starting eyepiece to locate objects. I then switch either to a 12.5 mm Meade Series 4000 Plossl (x100) for most deep space objects- nebulae, clusters etc, or a Williams Optics SPL 6mm for planetary work (x200). If limited to 3 eyepieces these would be my choice, although I do also still use from time to time, my Meade Series 4000 26mm Plossl with came with the ETX 80 refractor.

[Kirscovitch]

Over here I get on a rare occasion to play with my 3mm. It brings my mag in the SLT to 216.

Most of my best views come with a 9mm and 2x barlow at 144x