Barlow Vs Powerful Eyepiece

[Neon]

It's getting to that time of year where I might possibly have some money in my pocket and fancy treating myself to a new eyepiece

I'm still using my trusty 80mm Sentinel and have been getting into planetary and lunar observation of late, so I'm looking to get a decent eyepiece with fairly high magnification.

At the moment the most powerful eyepieces I have are a 12.4mm Plossl and an 8mm Hyperion, along with a x2 barlow lens. These give me magnifications of x77 and x120 respectively. Ideally I'm looking for something in the region of x150 to x200.

Orthoscopics seem to be a good choice, but I'm not sure how well they barlow, or if I should just try to get a single eyepiece around the 2.5 - 3mm range and cut the barlow out altogether.

Any ideas or suggestions?

[daz]

A straight eyepiece is preferable, as you are not introducing more glass into the train.

Ortho's have a narrower FOV and are especially good at high power planetary and lunar.

Trouble is at 80mm aperture, 2.5 or 3mm is going to be really pushing the limits of the scope I feel....

[Neon]

I think I will be pushing the scope to its' max on stuff like Saturn or Mars, but for lunar observation I think it should be okay (depending on the conditions). Obviously, if I do go for a straight eyepiece it'll be the highest mag I'll use on the scope.

I'm looking to spend around the £60-80 price bracket for this eyepiece (whether straight or barlow'ed). Are ortho's available in the 2.5 or 3mm size?

[Rob]

I had the sentinel 80.. nice scope, but you will be pushing it hard as Daz says. My advice to you would be to pick up a 90mm / 105mm or 127mm Skymax mak. the 8mm Hyperion is fantastic in one of those long F raito scopes. You will not need new EP's or a barlow!!..

Save your cash and speak to FLO. A nice 90mm Skymax will sort you out here (budget wise).

Keep the Sentinel for wide & DSO work.

Rob

[GazOC]

In addition to pushing a 80mm scope pretty hard, the CA will really start to show on a 80mm f6 achro at those mags esp on the planets.

I've never come across a 3mm orthos but Tak (I think!) do a 2.5mm but they tend to be expensive if bought new.

[Neon]

Whilst I'd love to get a new scope (preferably a mak) I doubt I'll have the money readily available for a long time, and I can appreciate that this eyepiece will be pushing it. It's not that I'm trying to use my little semi APO as a planetary telescope, just to give me the option to use it as such occasionally, if the conditions are right.

Part of the reason for this is that I saw a couple of articles on Cloudy Nights about the William Optics SPL range, here and here. The authors use at least one 80mm scope in the testing (albeit a fully APO, but with longer focal length) and speak favorably about the outcome. In my scope a 3mm SPL would be x160 mag, slightly higher than recommended (50 mag x each inch of lens).

[philsail1]

Neon,

I have a Skywatcher 90mm Maksutov (f13.88, and 1250mm Focal length), and though it is a great little scope, it will not cope with either the "TAL" 6.0mm Orthoscopic (giving a magnification of 208x), or my unbranded Japanese 6.3mm Orthoscopic (198.4X). The images produced are a bit on the "blurry" side, and focusing is critical. However, it does cope very, very well when using a 10mm Vixen NVL eyepiece (125x), and even better with an "Celestron" 18mm Orthoscopic (69x Magnification). I can Barlow this to 138, and the image and field of view is still very good. Yes, the 6.0mm and 6.3mm will greatly magnify the Moon's features very, but I find it uncomfortable, and tend to change down to a more moderately sized eyepiece.

I don't have experience of a "Sentinel" scope, but at "f6" I too would be wary about spending a lot of money on a powerful eyepiece which may not give good results.

Perhaps it might be an idea to try to loan an eyepiece to "try before you buy."

I would go for a 12mm or 18mm Orthoscopic eyepiece. (You are will be getting a size of eyepiece which will work on your scope, and you will increase the range of magnifications from your eyepieces, with the Barlow you already have).

You could of course, buy a Skywatcher 127 Mak!

Hope this helps,

philsail1

P.S. If you haven't got anyone nearby to borrow a powerful eyepiece to try, I could loan you my TAL 6.0mm and the Jap 6.3 orthoscopics to try for a few days. All I would ask is that you pay for return postage (insured) - and return, as soon as you have finished with them!

[Neon]

Hi Phil,

That's very generous and trusting of you. I might well take you up on the offer once I've got a slightly better idea of what I need.

My current eyepieces are (just to give an idea for magnification purposes):

8mm Hyperion

12.4mm Meade Super Plossl

24mm Hyperion

32mm Erfle

Ideally I'll sell on the 12.4mm and maybe get something around the same size. I'm coming around to the idea that a 3mm eyepiece might be a mistake, but perhaps something around the 6mm size might be a better option. I'll probably get more use out of that than something that I can only really use in exceptional conditions.

I've got a friend who's just taken up this hobby and has a few EP's himself. I'll see what his got and have a little play around with them to see how they work in my scope. Not sure that he's got any Orthos though.

[philsail1]

You have a good range there Neon. Glad you have access to some eyepieces - my offer is there if and when needed.

Best wishes,

philsail1

[John]

I'd go for the barlowed approach Neon. A short focal length eyepiece in my ST80 scope (an F/5 achromat) does over-emphasise the false colour a bit too much IMHO wheras when I barlow a 5mm eyepiece the false colour is much more acceptable because the barlow has the effect of lengthening the effective focal length - and reducing the effects of false colour. You also maitain reasoanble eye relief to boot which makes observing more comfortable.

I use a Celestron Ultima 2x Barlow (it's actually a 2.2x barlow I reckon).

John

[part timer]

Yes don't forget Barlow's can be excellent. Most people seem to think they will degrade quality. They shouldn't!!!

If you choose a good one (say at least 50 pounds) from a good manufacturer they will give good performance.

[lunator]

Neon

If you are happy with the smaller field of view I would lookat getting a 12.5mm otho as an alternative to the 12.4 Meade.

I have one and it is a great eyepiece. They can be picked up for £20-£25 leaving plenty for a decent barlow.

Cheers

Ian

[Neon]

Cheers guys. I think it'll have to be a barlow and an eyepiece to solve my problem. Currently I use one of these to boost my magnification by 2, but the thumb-screw has come off . I can probably get it re-bored and get another thumb-screw fitted, but I'd definitely like to upgrade to a Celestron Ultima, or a 2" EDO barlow. I also use a William Optics violet filter to help with the colour diffusion, which may effect the image quality.

Jahmanson, I see that you have a quite a collection of quality eyepieces (Naglers etc) and similar sized scopes to myself. Do you notice that much difference in the performance between a £70 eyepiece and a £140 eyepiece in an F6 scope to warrant such an investment. Like you, I use an Alt-Az mount so keeping an object in my FOV is harder at higher mag, which may be a factor I should be considering.

If I can sell the Meade in the near future I'll probably go for a 10mm eyepiece (the 24mm Hyperion can be barlowed to 12mm) maybe an ortho, although I'd probably want something around 5 & 7 with that kind of eyepiece. Do orthoscopic lenses balow well?

[John]

Jahmanson, I see that you have a quite a collection of quality eyepieces (Naglers etc) and similar sized scopes to myself. Do you notice that much difference in the performance between a £70 eyepiece and a £140 eyepiece in an F6 scope to warrant such an investment. Like you, I use an Alt-Az mount so keeping an object in my FOV is harder at higher mag, which may be a factor I should be considering.

TBH I reckon the outright performance difference between say a Hyperion and an equivilent Nagler would be slight apart from the wider field of view which is really noticable and, to me, valued.

It's a very personal thing as to whether marginal performance differences are "worth" additional cost if course - I'm currently at a point where I wanted to build a set of top quality eyepieces and I don't regret any of the investments - they are a pleasure to own and use.

That said, if I had to sell my premium eyepieces and use a budget set I'm sure I would still be able to get a lot of enjoyment from the hobby

John

[Neon]

Thanks for your advice John. I think until I'll probably stick to the £60-80 mark for now, mainly since I don't know what I'm missing with regards to nicer eyepieces (my ignorance is bliss ), and I probably only get to use my scope for about 30 minutes a week.

Mark