Another wide angled EP, but would it be worth it

[bomberbaz]

Turns out the 72 degree for the vixen 42mm is incorrect, its actually 65. Disapointed, well yes because it was the promise of the extra wide fov that made my decision. (the difference in my scope is 0.15) Had I known, I would have made a different choice. Either the skywatcher aero 40 or the WOpitics 40 and now I have spent the money, the skywatcher panorama 23mm/82 afov. thise two along with my existing 30mm/80 ultra wide would give me some very good wide field viewing.

Anyway, not decided which way to go as the panoramas are over £200 and the aero would take me over original budget, the WO although not the best EP would keep me in it.

Dam this hobby and misquoted websites

watch this space............

[Stargazer_00]

FLO quotes this on their page:

NLVW 42mm 2" 72° 20mm

545g (19.22oz)

Is that incorrect? The rest of the EPs show 65 degrees

http://www.firstligh...-eyepieces.html

[E621Keith]

Turns out the 72 degree for the vixen 42mm is incorrect, its actually 65. Disapointed, well yes because it was the promise of the extra wide fov that made my decision. (the difference in my scope is 0.15) Had I known, I would have made a different choice. Either the skywatcher aero 40 or the WOpitics 40 and now I have spent the money, the skywatcher panorama 23mm/82 afov. thise two along with my existing 30mm/80 ultra wide would give me some very good wide field viewing.

Anyway, not decided which way to go as the panoramas are over £200 and the aero would take me over original budget, the WO although not the best EP would keep me in it.

Dam this hobby and misquoted websites

watch this space............

Not sure where you got that information, but don't worry 42mm is 72deg. All other LVWs are 65 deg except the 42mm which is 72deg

The 42 LVW does not have a field stop (because the eyepiece barrel is the field stop), so you are getting as much field as can be fitted in a 2" barrel. If you want to go any wider than the 42 LVW, you will need to wait for the 3" 30mm ES100.

edit: forgot to add, the 42mm LVW's field is supposed to be slightly distorted, which increased its AFOV, but nevertheless it has the widest field stop of any 2" eyepieces, so it will give you the maximum true field.

[bomberbaz]

Hiya Keith, thanks for that but FLO quote 72 and thats where i made the purchase. Turns out that is wrong. Yesterday Vixen themselves were quoting on thier website 72 and today it is 65. So I got the info off the manufacturer, afraid its horse ajnd mouth here unless something is really starnge here...........

I am sure you believe me but check if you like. Quite annoying given the amount of time and thought I have gone into and the responses you people have kindly provided. See http://www.vixenoptics.com/acc/lvw_eyepieces.html

Waiting to hear back from Vixen who I have emailed for clarification

watch this space again

Steve

[E621Keith]

But the print on the eyepiece barrel says 72deg, so the Vixen USA website is wrong (as are their mount load capacity ratings)

http://www.kyoei-osa...n-eyeLVW42.html

Many website do quote 65deg, but I guess they just assumed all LVWs are 65deg and didn't read the small print about the 42mm

[bomberbaz]

Unless I get a satisfactory answer I am going to sack vixen off. When you are shelling out almost £300.00 you expect the information to be spot on. I am not sure who has provided the informatin to whom here but at first I thought distributor, then provider and now I am not sure what is what.

If you like, just google the EP and check out the distributor websites. Some quote 65, some 72 like you say, but now Vixen them selves. Trust me Keith, yesterday thier website showed 72 and today 65!!!!! Confused, I am !

Again, watch this space, I will report back on what I find out from FLO and Vixen. I hope to get a matching response.

Steve

[Dunkster]

I'd say Keith's photographic evidence makes it a pretty safe bet Baz...it's easy enough to not put the right info on a website, but a whole other thing to print the wrong specs on the barrel when you're a quality maker

[bomberbaz]

dam browser just erased a 15 minute explanation. Shortening now to Vixen have agreed to clarify the situation. At present nothing is either right or wrong. Confused!! you should be and I have been on with this all day. about 20 emails and a ton of other conflicting web based information.

Watch this space.

Steve

[E621Keith]

There have been a lot of confusion to the AFOV and TFOV of the 42mm LVW.

I will do a drift test on my 42 LVW next time I have clear skies (which could be weeks if I am not lucky).

If anyone else have a 42 LVW and clear skies before me, please measure the time it takes for a star at the equator to drift across the AFOV.

The formula posted on CN for drift transit time is given by:

TFOV (arcsecond) = Transit time (s)*15.04*cos(declination angle of star)

http://www.cloudynig...66/Main/3210955

[bomberbaz]

I'd say Keith's photographic evidence makes it a pretty safe bet Baz...it's easy enough to not put the right info on a website, but a whole other thing to print the wrong specs on the barrel when you're a quality maker

Even Vixen don't know what is correct dunkster. They have admitted to having conflicting information and this is a big concern. I wont say anymore until the issue is clarified and then I shall post a full explanation for any future would be purchasers of the said ep.

There have been a lot of confusion to the AFOV and TFOV of the 42mm LVW.

I will do a drift test on my 42 LVW next time I have clear skies (which could be weeks if I am not lucky).

If anyone else have a 42 LVW and clear skies before me, please measure the time it takes for a star at the equator to drift across the AFOV.

Keith, do you not also have an aero ed 40mm. According to the simple EP calc spreadsheet if the Vixen has a AFOV of 72, you will see a very noticeable difference in the TFOV over the Aero, if it is actually 65, then the TFOV for both ep's should be identical. !!

Just wondered if there were any landbased objects you could home in on to see where the edge of the fields were or something !

[E621Keith]

I'm afraid not. I have a 30 Aero, but not a 40.

The AFOV of eyepiece is not easy to measure just by looking at the eyepiece, especially wide field designs. On top of this, the AFOV is also affected by rectilinear distortion, so the only definitive way to accurately measure the true field is to carry out a timed transit or finding some terrestrial targets for measurements.

[Stargazer_00]

I've read in a number of places that the stated AFOV isn't always accurate but more approximate.

For instane the 82 degrees on all my eyepieces; some could be 78, others would be 85....it's all 'close enough' was the impression I got reading some articles.

[bomberbaz]

Do you know this is actually quite amusing as well as frustrating. Some might think it being pickie but you want to know what you are getting and that it is has described. Hopefully hear back from someone at vixen this afternoon. :-)

[michael.h.f.wilkinson]

I gather that the 42 mm has a 48mm field stop. That works out to a 69.7 mm true or geometric apparent FOV. The apparent FOV could easily be 72 deg if the EP has just a few percent pincushion distortion. These EPS always have some, so the figure on the barrel is correct (most likely)

[Macavity]

Yes, I seem to remember I could never get the supposed true field of view out of my 10mm (long, quirky) Mk.I Speers-Waler. The apparent field looked plausible, by eye... But then, they did "reappraise" the focal lengths, when it became Mk.II version? <G> Moreover, the focal length of a CAT system varies a fair (surprising!) bit with focal settings. That before you start on (presumed) eyepiece distortions.

The LVW 40 is a lovely (looking too!) eyepiece though. I'm glad the (my) Hyperion Aspheric, performs reasonably well. I have seen claims that LVWs are "good to F4", generally. As previously mentioned, I remain slightly confused as to why Hyperions (An LVW clone) aren't. Or more generally, what kind of "Magic", e.g. Televue, Pentax use, to make them work well with a "steeper light cone" or whatever?

Am currently using a "British Standard" (neighbours!) Chimney Pot to measure my setup TFoV at various settings. A hard-copy of the VIDEO image is particularly handy - One can then use a ruler! I do remember, that Vixen Lanthanums were (according to me!) notably close to their specification focal length / AFov etc though.

[bomberbaz]

I gather that the 42 mm has a 48mm field stop. That works out to a 69.7 mm true or geometric apparent FOV. The apparent FOV could easily be 72 deg if the EP has just a few percent pincushion distortion. These EPS always have some, so the figure on the barrel is correct (most likely)

I do remember, that Vixen Lanthanums were (according to me!) notably close to their specification focal length / AFov etc though.

I sincerely hope that you are both right. FLO will have received the EP by the time this matter is resolved and hopefully if you ARE right my EP will be but a day or two away!

Steve

[Macavity]

Heheh. Actually, my (once) Vixen Lanthanums were the 1.25" / 40-50 deg ones.

The quality was great though - I would have similar hopes for your LVW 42.

[bomberbaz]

Received a reply from the man at Vixen. They have had a response from the japanese manufacturer who have told then the fov for the 42mm is 65.

This is good enough for me but it would be very ijnteresting to know how your drift test does Keith. Now its deciding what to do next about this, but for now its nothing cos zebedee is calling. Night all.

[John]

Received a reply from the man at Vixen. They have had a response from the japanese manufacturer who have told then the fov for the 42mm is 65.

This is good enough for me but it would be very ijnteresting to know how your drift test does Keith. Now its deciding what to do next about this, but for now its nothing cos zebedee is calling. Night all.

A bit disappointing though as they would loose their "crown" as the widest true field eyepieces available in the 2" fitting now. Some dealers are going to need to revise their website descriptions too.

[E621Keith]

No luck tonight, but weather forecast says there may be a few hours of clear skies tomorrow night. Fingers crossed.

[alan potts]

This is something I was saying on a thread a while back and everyone was telling me I am wrong, many of the sites that sell this eyepiece e.g. TS have stated 65 degrees for a long while. However when you see the photo they have of the eyepiece it shows 72 degrees on the barrel, as to which is correct I don't know. I know Keith has one so it would be a bit silly not to listern to him.

Alan.

[bomberbaz]

No luck tonight, but weather forecast says there may be a few hours of clear skies tomorrow night. Fingers crossed.

i am going to wait for the results of this hopefully. I am not entirely convinced that the man at Vixen knew his onions as well as he should. And that maybe his "Japan say 65 " remark was just to get rid of me. In all fairness they have changed thier website to 65 but lets see what keith's results are.

Steve

[bomberbaz]

A bit disappointing though as they would loose their "crown" as the widest true field eyepieces available in the 2" fitting now. Some dealers are going to need to revise their website descriptions too.

excatly John and the crown would go to the rather budget priced WO swan 40 mm. !

[Dunkster]

SW Aero 40mm?

[Stargazer_00]

Really very surprised that they printed 72 degree on the eyepiece when it's 65 degrees. Especially when all the rest in the range are 65 degrees, it hardly a typo.

Baz, could you cut and paste the response from them? Obviously edit out anything personal to you for security.