Some daylight trials of the Vixen SLV 5mm and TV 25mm Plossl

[michael.h.f.wilkinson]

I couldn't stand waiting any longer for clear skies so got out the 80mm APM and aimed it at the trees in the distance with various EPs to check out the quality of the latest two additions to the collection. No real stringent test, but it gave some idea. I first tried the TV Plossl 25mm against the MaxVision 24mm 68 deg. This was a close run thing. There is very little difference in the amount of detail shown. The TV 25mm might have had a smidgen more contrast, but the MV 24 looked perhaps a smidgen brighter. The FOV was a hands down win for the MV, of course, whereas in terms of weight, the TV wins clearly. I then switched to the other end of the spectrum, and put in the SLV 5mm. The view was much dimmer, of course, but contrast was good, and the details were crisp, once the eye adjusted. The Pentax XW 7mm gave a much brighter and larger view, but in terms of sharpness or internal reflections the SLV was great (and very light of course). Another pleasant surprise is that the SLV is nearly parfocal with the XW 7. The difference in focus between the SLV 5 and XW 7 is no larger than between the XW10 and XW 7, I feel. Very nice when switching between different magnifications, which I do a lot in planetary observations. If it performs as well on planets as it did on trees and lichens I might consider getting a 9 and 6mm as well, to have a close-spaced series (XW10, SLV 9, Delos 8, XW 7, SLV 6 and SLV 5) for planetary work. The Delos 8 might feel a squeeze a bit, as it is far from parfocal from the XWs. We will see.

Whatever the outcome, the new EPs certainly seem keepers; the SLV as high mag planetary and solar white-light, and the TV {Plossl for solar H-alpha (both in LS35 and future Quark).

[Floater]

Rock on, Michael!

[YKSE]

Very interesting result Michael  So the wider FOV (68deg and 70deg) give brighter view, even the magnifications are higher AND lower than the narrow FOV EPs, still the contrast is not affected by this difference?

[Chris]

Looking forward to hearing your thoughts under the stars Michael, fingers crossed for some clear nights

[Pig]

Nice one Michael  I am glad you are happy with the SLV's

[John]

Sounds very promising on the SLV Michael

I'd have thought the TV plossl would be a pretty bright eyepiece - the measured light transmission through them is about as high as eyepieces get. It will be interesting to see how it does under "battle conditions" ie: at night

[michael.h.f.wilkinson]

Very interesting result Michael  So the wider FOV (68deg and 70deg) give brighter view, even the magnifications are higher AND lower than the narrow FOV EPs, still the contrast is not affected by this difference?

My writing may not have been clear. Remember these are all visual impressions, and the brain can play strange tricks. Comparing the 25mm TV and 24mm MV, the wider FOV of the latter at (roughly) the same magnification may be the reason that the image appears brighter, simply because the total amount of light reaching the retina is larger, because the entire FOV is illuminated in daytime. At night the dark sky background may reduce this effect. Regarding the XW7 and SLV5 comparison, the SLV shows a lower brightness, mainly due to the higher magnification (but perhaps the smaller FOV contributes as well). Once the eye is adapted to the lower surface brightness, I find a "normalising" effect takes place, and the contrast in fine detail appears on a par with the XW.

[bomberbaz]

I have a SLV 9mm and although I haven't fully broken it in, when on the two occasions used I compared it to the delos 10mm, it was slose run to me although these were not dark sky conditions.

The delos gave the bigger fov obviously and was crisp edge to edge and seemed a little brighter as michael said but the tighter view of the 9mm seemed to just have a slightly better contrast.

I really haven't had more than 2 decent nights viewing since I bought it (didn't stop me buyng a 15mm SLV though) but as I have previously stated if I had not bought a 5 and 6mm eyepiece already (XW and Delos ), I think I would have gone for these instead. Cracking eyepiece and just feel so nice to put our eye against. Think thats what made me buy a 15mm as well, that and a bit of space in the eyepiece case  .

Steve

[YKSE]

Thanks Michael, that's the effect of wider FOV I was suspecting.

[YKSE]

This is the review which got me to start thinking the effect of FOV:

http://stargazerslounge.com/topic/208793-maxvision-24-v-maxvision-24/?hl=%2Bmaxvision+%2B24mm+%2B68+%2B82

[michael.h.f.wilkinson]

Odd, that. I will compare the TV 25, MV 24, and the mighty Nagler 22T4 on M42 and see if my experience is the same. There may of course be transmission differences. Having said all this, my main use for the TV25 will be solar H-alpha, in which transmission is less of an issue than in deep sky. The field stop is big enough both in the LS 35 with B1200 filter and in the future Quark.

[Fozzie]

If the 5 mm slv is as good as the 6mm that I'm currently taking breathless views of the moon through then you will be a very happy man...

[michael.h.f.wilkinson]

I am sure it will, although only on the very best nights with the C8. In the APM F/6 it will see a lot of use on solar white light, and on lunar and planetary when I use it as travel scope.