2" Eyepeices for a fast scope

[globular]

You are doing the right thing - get the scope and see how your existing EPs work in it.

I will repeat my earlier comment on exit pupil though.  Your 40mm plossl will give you an idea of the FOV you can get - but I suspect the way the FOV is presented will not be very good, and not representative of what a higher power but wider eyepiece would produce.

With an exit pupil of over 8mm you will not be able to get all the light from your scope into your eye all at once.  This means the image will be dimmer and is akin to losing some of your telescopes aperture.  
Your scopes aperture is already small at 102mm so I'm not sure you'll enjoy the view when giving up a significant proportion of it.
If your eye's pupil size is, say 5mm, then you're losing about 22% of the light when using a 40mm eyepiece - so the brightness will be like that from an 80mm telescope (although the magnification and field of view will be that of your 102mm scope).

My guess is that the best wide field views you'll get from that scope will be using a 20 to 25mm eyepiece.

 

Edited September 28, 2023 by globular

[lawsio]

35 minutes ago, John said:

If you have the 32mm plossl, that will show you the same amount of sky as the 40mm but with a more pleasing, and wider, apparent field. The exit pupil will be smaller as well so you should see a slightly darker background sky which helps pick out deep sky objects.

I have a 32mm Meade Super Plossl that I acquired many years ago, cant remember if it was an expensive one or not but it's my nicest low-power one in my slower scopes so suspect that will live in it for a while.

[Mr Spock]

1 hour ago, lawsio said:

I have a 32mm Meade Super Plossl

I have one too, it is very good. Superseded by the UFF now, it sits in a drawer.

[johnturley]

On 28/09/2023 at 13:16, johnturley said:

Thanks for the info.

I have now successfully placed an order with Harrison Telescopes, so remains to be seen whether they will actually be able to supply one.

Assuming it does arrive, I will compare it with my 36mm Aspheric, and 56mm Meade Plossl, and if it compares favourably, possibly sell both of these. My Meade 56mm Plossl is actually one of the original 5 element made in Japan eyepieces, so may fetch a bit of a premium price.

John 

Just received notifications from Harrison Telescopes, that they have now shipped the 42mm Vixen LVW.

Although their website showed that this eyepiece was available, I did have my doubts as to whether they would be able to supply one, as Vixen ceased production some time ago, none of my 'usual' retailers were listing it, and it does state on their website that this product comes direct from their supplier. In fact its still showing up as available in case anyone else had thoughts about getting one.

John 

Edited September 29, 2023 by johnturley

[johnturley]

On 29/09/2023 at 16:07, johnturley said:

Just received notifications from Harrison Telescopes, that they have now shipped the 42mm Vixen LVW.

Although their website showed that this eyepiece was available, I did have my doubts as to whether they would be able to supply one, as Vixen ceased production some time ago, none of my 'usual' retailers were listing it, and it does state on their website that this product comes direct from their supplier. In fact its still showing up as available in case anyone else had thoughts about getting one.

John 

The 42mm Vixen LVW from Harrison Telescopes finally arrived today via DHL (took nearly a week to come), and they are still indicating that stock is available.

At first sight it is quite an impressive and well constructed eyepiece, and according the my kitchen scales (which may not be very accurate) it is lighter than advertised at just 484g, definitely lighter than my 30mm UFF (570g), but heavier than my 36 mm Aspheric (400g). 

Holding the eyepiece up to the light, the APFOV appears larger than the advertised 65 degrees, similar to my 30mm UFF (70 degrees), and my 36mm Aspheric (72 degrees) and noticeably wider than my 24 mm Panoptic (68 degrees)

I am now waiting for some clear nights to to see how it performs, in particular compare it with my 30mm UFF, 36mm Aspheric, and 56mm Plossl. In particular I am expecting significantly better edge performance compared to my 36mm Aspheric plus a slightly wider field of view, otherwise I will have made a fairly expensive mistake.

John 

Edited October 10, 2023 by johnturley

[Mr Spock]

41 minutes ago, johnturley said:

Holding the eyepiece up to the light, the APFOV appears larger than the advertised 65 degrees, similar to my 30mm UFF (70 degrees), and my 36mm Aspheric (72 degrees) and noticeably wider than my 24 mm Panoptic (68 degrees)

It is 72°. They changed it to 65° to alleviate complaints about the true field of view. The eyepiece suffers from a difference in focal length across the field of view. As an average it should be called a 38mm 72° eyepiece...

As you can see, they were labelled as 72° once upon a time 

 

[johnturley]

Got the first chance last night to compare the 42mm LVW with my other 2in Wide Field Eyepieces last night, the 30mm StellaLyra UFF, 36mm Baader Aspheric, and Meade 56mm Super Plossl. Conditions were not good however due to haze and low cloud.

Looking at the Pleiades through my Esprit 150, I found the 42mm LVW gave sharper images than the 36mm Aspheric, and there was less falling off in image quality towards the edge of the field, but it was by no means perfect, and nowhere near as good as the 30mm UFF or for that matter the 56mm Plossl, although in the case of the latter, it only has a 52 degree APFOV, compared to the approx 70 degrees of the other three, so can't really made a comparison. On the plus side, though I found the LVW did not suffer from any 'black-outs' at all, which some observers have reported. I will agree though that the 30mm UFF stands out as an outstanding eyepiece both in terms of quality, and value for money.

The 56mm Plossl is one of the original 5 element made in Japan 'Smoothside' Plossls (similar in design I think to the current Masuyama eyepieces that FLO sell), and has massive eye-relief, making it necessary to position the eye about 2in away, which is awkward with these eyepieces not having rubber eye guards, and I wondered whether it is possible to buy something to fit. A 56mm eyepiece is really too low a power even for an f7 instrument, but I still find it useful for extra wide field views, and will probably keep it (I've had it over 30 years), but probably sell the 36mm Aspheric.

I would be interested to know how the 42mm LVW compares to the 41mm Tele Vue Panoptic, I don't know whether anybody has done a comparison, I would expect the Panoptic to be superior, but is nearly twice the price, and about twice the weight, and I really don't like very big heavy eyepieces, due to my fork mount (on which Esprit is piggybacked) being very balance sensitive, and it is not possible to lock the dec axis. Partly for this reason I decided to sell both my 20mm Type 2 Nagler, and ES 24mm 82 deg eyepieces, replacing the latter with a much lighter 24mm 1.25in Panoptic.

For comfortable wide field viewing, I generally prefer approx 70 APFOV eyepieces to those with 80 degrees plus.

John

Edited October 10, 2023 by johnturley

[globular]

Have you considered the Pentax XW40?
It's 700g so is heavier than the LVW's 550g - but not by 'that much'. And there are none of the distortions and varying magnification described by Michael in the LVW - and it's the same price.  I love mine. 

[johnturley]

1 hour ago, globular said:

Have you considered the Pentax XW40?
It's 700g so is heavier than the LVW's 550g - but not by 'that much'. And there are none of the distortions and varying magnification described by Michael in the LVW - and it's the same price.  I love mine. 

I would be a bit put off by the weight of the Pentax, almost as much as the ES 24mm 82 deg eyepiece which I sold partly for that reason.

I actually weighed the LVW on my kitchen scales (which may not be that accurate) at 484g, also the Pentax is a bit more expensive at £379, compared to £315 for the LVW at Harrison Telescopes.

John  

[John]

I think one of the challenges with lower power 2 inch eyepieces in a fast newtonian is maintaining the exit pupil at an effective size while maximising the true field width. Sticking with ~70 degree AFoV's adds a constraint but I can understand why some folks prefer that as well as wanting to keep the eyepieces size and weight (and cost) manageable as well. It's a matter of deciding what trade off's you want to make 🙂

 

 

Edited October 10, 2023 by John