130EQ 1.25" or 200P 2" eyepiece

[datman]

Hi

I have both a C130Eq and a SW200P and have take a fancy to the idea of a 2" EP for wide views. Because of my age I was looking for exit pupil of about 5mm so that puts me in the 24-26 range. While doing my research I came to this theoretical conclusion. I would get a wider FOV with the C130Eq with a 1.25" 32mm (exit pupil 6.5) I have than I could ever get with a 2" SWA EP. So am I wasting my money or does someone know something I don't?

So the first question is:

Would I get a better view with the C130Eq and a 32mm 1.25" than with a 200P with a 26mm 2" EP

[great_bear]

Not quite - but it's close - you could get a slightly wider view with a 40mm 68 degree SWA in the 200P, but I thought you wanted exit-pupil to be the limiting factor?

If so - and assuming the 130 is an F5 scope like the 200P, then yes, for a given exit pupil you would see a wider true field of view with the 130.

From a practical perspective in the 130, a 32mm Plossl gives you no more true field of view than a 24mm SWA does - and from my own experience with a Sky-Watcher 130P I can thoroughly recommend the Meade 24mm SWA provided you can get it at a good price (such as here <click>)

At 2.5 degrees true-field @ 68 degrees AFOV, it's all the field you need, and the view is really, really nice.

[datman]

Hi

Thank for that.

My understanding of exit pupil is that 40mm would give an enormous exP of 8mm. I've read that your pupil diminishes by 1mm per decade so at 64 I should be blind by now ;-) Anyway even with a 6mm pupil 25% of the light is being wasted.

So by that reasoning I thought that 5mm exP ought to be perfect. So 25 would spot on and your suggestion would be a tad less so equally good if not better.

So as I was starting to suspect the best option may well be to buy a very good quality 1.25" which can be used on both scopes.

Any other thoughts on this?

[great_bear]

Any other thoughts on this?

Yes - I've had this dilema myself...

even with a 6mm pupil 25% of the light is being wasted.

A bigger problem is that the sky - even with moderate light pollution - can tend to look a bit washed-out at such an exit pupil, and also that the image of the secondary mirror starts coming to focus at the same time as its shadow also starts to rob light from the system.

I was starting to suspect the best option may well be to buy a very good quality 1.25" which can be used on both scopes.

A good-quality widefield 24mm really is something that I consider to be a "must have" eyepiece - either the Meade SWA or alternatively - if you want to spend more money - a Tele Vue 24mm Panoptic; generally considered to be a "classic", much-loved eyepiece by its owners.

[datman]

Hi

Well the Meade 24mm is a very good price at the Web site you linked but I've seen one at my local and compared to what I have already it's more of a glass counterbalance than an eyepiece! So I've done a compromise and bought an Antares W70 25mm 60 degree FOV. I'm still a little resistant to spending vast(ish) sums on eyepieces put my sights are slowly rising.

I'll see how I get on with that.

Thanks for your input.

[great_bear]

For just a few pounds more than the Antares, you could have the equivilent Celestron XCel-LX 25mm 60 deg. eyepiece, which is a better bet in terms of quality.

For more info click <here>

[datman]

Hi

Oh well, it's too late now, I did look at that and the Meade 25mm but they all look to have the same specification so I went cheap! RVO is only a 15 minutes away and no wait! The Meade does look nice though. However this is my most expensive eyepiece yet. The others are Antares Possel (20+32) which I'm quite happy with so I thought a more expensive Antares should be OK. I also have Paradigm Dual EDs which I really like but I'd read the 25mm was not that good hence the search for something else.

I'm still pretty new to this and the learning curve is still pointing upwards. I'm sure the advice you are offering is very sound but at the minute I'm in a different league price wise on EPs.

I'm trying to focus on Astrophotography which has been sucking at the wallet a bit.

Still plenty of time to have a change of mind though

[great_bear]

It's true - good widefield eyepieces at ~25mm are few and far between. Good luck with the Antares. RVO: Top retailer, excellent guys.

[datman]

Follow up, the Antares W70 25mm 1.25" in the SW200P was for want of a better expression awful! Worse than the much cheaper Antares possels.

By awful I mean either centre 1/2 in focus or outer 1/2 in focus but not both. Clearly this eyepiece does not like fast reflectors.

I was refunded without any problem.

I have since bought a 2" GSO 30m which I had been put off by some reviews by other people. Despite this after reading the manufacturer's description and a very attractive price I decided to risk it.

I thing it is excellent! Maybe a bit soft on the edges if I look very hard but not enough to concern me. Exactly as the manufacturers review said. i.e. 85 percent in focus the rest a bit soft with a fast reflector.

Maybe 20-20 vision reviewers who can pick out a double photon at 20 metres should say so. ;-)

Why don't all eyepiece manufactures specify which telescopes are suitable. It would save a lot of hassle for all involved.

The view that fast scopes need expensive EPs is not necessarily true either. None of mine cost more than £50 and they all work very nicely thank you.

[rwilkey]

The SW PanaView 32mm 2" is a great eyepiece in the 200P, or if you feel the exit pupil is a bit large then go for the 26mm. However, it works for me (age 61), great flat field, yes, a tiny bit soft at the edges but not enough to put you off. My first and best ever eyepiece for my 200P.

[John]

The 32mm is the "sweet spot" of the Panaview range in my opinion. The 38mm is next then the 26mm - I'd be tempted to "try before you buy" with the 26mm.

[datman]

Nice to hear someone has a similar view, I believe the GSO Superview 30mm is a 5 element (Erfle?) so may be similar to Panaview? Anyway exit pupil was a consideration (my eyes are about 4 years older than yours Robin)! Also at £45 a real bargain too! I tried it out last night and am still very pleased with it.

[rwilkey]

The GSO Superview sounds good at a reasonble price, heard about them but never seen or tried one.