The 6mm Cup Final with penalty shoot out

[michael.h.f.wilkinson]

I never felt Jupiter responded less to magnification than Saturn. Saturn does have some "knife-edged" features (in the rings, and its shadow) which might show up better with high mag than the softer edged features on Jupiter. Mars and the moon respond best of all in my book, probably because the surface brightness is much higher.

[mdstuart]

One thing you have not mentioned is transparency. As a viewer of galaxies this is quite a big deal.

??Pick a field with a few stars around the limit of the scope and see which eyepiece can pick out the faintest stars..

Mark

[alan potts]

Mark

I agree I didn't really do that and have not done that in other reviews I have written very well. At this time of the year it is a bit of a waste of time because the seeing conditions take a good deal of transparency away, I am assuming you mean of the atmostphere. I did however badly refer to it in the part where I was looking at Saturns moons, pointing out that the Delos brought them out that bit better. I will however take what you have said on board and try to improve by including this better in the next thing I write. To try and answer as to which was best for deep sky seeing and without being able to put a figure on it I would say agian it was the Delos that wins the spoils.

Alan

[John]

I use Saturns fainter moons for testing purposes too. A really good high power eyepiece needs to both control light scatter well and have enough light transmission to pick up faint point sources of light. The Pentax XW's excell at this as, clearly, do the Delos range.

Thats probably a different sort of test from the one that Mark had in mind although I've been reading on the Cloudynights forum that an experienced member there, who observes with really large aperture scopes, has crowned the Delos the best deep sky eyepiece he has ever used as it goes a touch "deeper" than his previous favorite, the Ethos. Some stuff of his is here:

http://www.faintfuzz...m/AboutUs2.html

[alan potts]

I stick to what I said in the review, I wish we could all get together and see if we all saw the same thing with a box of eyepieces. That in itself would be a test, we all know eyes vary and also people seeing ability, I may be able to pick things you can't and vica vera.

If however it has been stated in America that Delos is king then that it, interesting that a 15% sale seems to have been launched at the same time, or is it me.

Alan

[mdstuart]

Thanks Alan

it was not a criticism. Your review was very professional which is why I would value your thoughts on transparency as well.

mark

so I save for a Delos!

[alan potts]

Mark,

Was what I said what you meant because I think John thought you were meaning something else? Seriously the Delos, I think everyone should have one in the collection, a bit like Dark Side of the Moon, you haven't got a record collection if you don't have that one.

Alan.

[John]

I hope I've not caused any confusion here

Alan's review was great but I know Mark is a galaxy fiend so light throughput is a high priority for him, more so perhaps than for someone who observes the moon and planets more. It is a difficult time of the year to test eyepieces on faint DSO's though. I only posted the link above as some info complimentary to Alan's review.

It seems to me that the Delos really is a true "jack of all trades" and master of them as well !

[alan potts]

Thanks' John. The addition was nice, thinking of a 30 inch scope? Even with the amount of land I have that would be bit much. Think I would dig a big hole for it to reduce the step ladder size a bit, I have been on flights that didn't get that high off the ground.

To me reviews are a leaning process and we all learn all the time, if I can try something that I may even find very interesting and it helps others then I will try to do it, after all I have a site that would be loved by a galaxy hunter, when the moon is not around that is.

Alan

[alan potts]

I managed to grab an hour last night before the rain moved in again. I was keen to revisit the Saturns moons with the 3 eyepiecesa as a test to checkout the ability of the eyepieces to dig deep. The first thing that was again on my mine was, is Titan really 8th Magnitude, it looks fainter than that to me.

The sky was very clear as it had rain twice during the day so it had sort of been washed, which always makes a difference and it had not been so hot. It was a sort of English day with temperature getting up to the 22-23 degree zone. This should help the seeing a good deal as when it is very hot you tend to get a lot of the days heat rising from the ground in the first few hours of observing.

In the time I had I was able to change eyepieces a good many times, I think the BGO was again just making a better job of the Cassini division but the other two were so close. If it were put into driving terms you would on the back bumper of the car in front. It was as far as I could see the Delos that made a better job of the 5 moons I believed I could see, they just seemed that half a magnitude brighter, if that makes any sense. There was also something I could see in the Delos that eluded me with the other two, whether this was another moon or a star I do not know but it was there. I couldn't even see with averted vision using the BGO and zoom, but sometimes this takes a little time and with the clouds rolling in behind I was in hurry up mode. I am going to have to view some of the galaxies in Virgo and Leo to get a better take on this with the position they are in my sky it would be a bit lazy not to.Maybe the tripet in Leo would be a good target.

Anyway I packed up and 5 minutes later it was raining. On Saturday I got a 180mm Mac and a fancy weather station, astronomical gear comes with free clouds we all know, but did you also know weather stations do too, you read it here first.

Alan

[Moonshane]

I may be wrong Alan but could the larger area of darkness around Saturn in the wider field create a marginally larger exit pupil than a narrower field and this is what means you can see a little deeper? Perhaps (following this theory) the slightly smaller exit pupil of the narrower field might create a slightly smaller exit pupil which more closely matches maximum visual acuity? Might be a daft suggestion but it seems logical. Either way, I think your excellent summary and ongoing updates confirm that these are truly excellent eyepieces with little between them. The fact that the BGO (and probably the Hutechs) remains in contention at their price point is a great achievement.

[foundaplanet]

Mark,

Was what I said what you meant because I think John thought you were meaning something else? Seriously the Delos, I think everyone should have one in the collection, a bit like Dark Side of the Moon, you haven't got a record collection if you don't have that one.

Alan.

That's quality that one A very good analogy.

[alan potts]

Shane

I thought exit pupil was directly linked to the focal length of the eyepiece and the focal ratio of the scope. That being the case then the focal lengths would have to vary in the eyepiece, which lets face it, they may do slightly.

Here is the info Apm F 7 Mac/Newt F5.26 So the Exit pupil in the APM is 6 / 7 . 857mm and for the Mac Newt it is 1.14mm So we have a difference there, last night I was using the Mac/Newt.

I really don't know if that is significant or not.

alan

[John]

I think exit pupil size affects perceived performance more than we realize. It's a subject that I need to find out more about

[Moonshane]

I think that the overall exit pupil of the eyepiece would be as expected but I meant more the size of the (eye) pupil might expand slightly with a wider field (containing more darkness) and that this might reveal fainter moons and stars than a narrow field eyepiece which has more of a percentage of its actual field filled by a bright planet making the (eye) pupil shrink slightly increasing depth of field and making details like Cassini and banding etc more prominent. Just a thought that popped into my head but might explain why people say that orthos are 'planetary eyepieces'?

[John]

There is a trick to reduce the size of the pupil before planetary observing and that is to stare at a sheet of white paper illuminated with a white light torch just before starting to observe.

It's just the opposite of what you need for deep sky observing of course but apparently does get the eye into a more receptive state to spot that elusive planetary detail earlier in the session

[alan potts]

Shane,

Interesting thought, I have no idea if there is anything in it but there could be.

John,

I will give that a try and then the wife really will think I have lost it, I am always having a go at her for leaving lights on the point my way. The Kitchen spot lights shine almost out the windows and being where we are there is no need for blinds ( I spent the money on eyepieces ).

Alan.

[michael.h.f.wilkinson]

The dilation size of the pupil does not matter as long as it is larger than the exit pupil of the scope. I think these differences are down to transmission, and nothing else. I spotted a similar effect comparing the XF8.5 and the Radian 8. Both have the same AFOV, but the Radian produces a yellowish cast, where the XF is neutral. This means that the Radian is not transmitting blue as efficiently as yellow and red. Given that I could see more trapezium stars in M42 with the XF, that indicates that the XF transmits blue better, rather than being worse than the Radian in yellow. The difference in magnification would actually be a disadvantage for the XF, as the background would be a shade lighter, making observation of faint point sources harder. I made a similar comparison between the XW10 and Radian 10, and came to the same conclusion.

Transmission is determined by the amount and type of glass used, the number of glass-air interfaces, and above all by the quality of the coatings. If you used Delos/XW quality coatings on the BGOs you might well get a better transmission on the BGOs

[Moonshane]

cheers Michael - I bow to your greater optical knowledge than I'll ever have - I bet you have forgotten more than I know

[michael.h.f.wilkinson]

cheers Michael - I bow to your greater optical knowledge than I'll ever have - I bet you have forgotten more than I know

what's "forgotten"?

[Moonshane]

what's "forgotten"?

I did know once but I have .....erm......what's that word again?

[cs1cjc]

Saturn always seems to respond better to high power than Jupiter does.

I think this is largely to do with brightness and and perhaps to size. Jupiter (magnitude ~-1.6 to -3) is on average around three times brighter than Saturn (-0.5 to -1.5). This brightness means that the more acute, photopic cones are active so less magnification is needed to see the same detail. The brightness also shows up defects in the optical chain at high magnification which are simply not visible with less bright objects. For example the disturbing ghost image so prominent in TMB type planetary eyepieces when viewing Jupiter is not an issue when viewing Saturn.

Venus (up to -5) is a particularly harsh test of optics, for example showing up tube currents in a Newtonian as an ugly smear, which again are not visible on dimmer objects but which are presumably robbing the instrument of sharpness.

[michael.h.f.wilkinson]

That does not quite chime with the fact that I find Mars hold high magnification better than Jupiter (as does the Moon), for me at least.

[Naemeth]

I've no real experience of Mars observation, I only spotted it once quite a few months after an opposition.

The Moon probably takes more magnification as it's closer, larger and far brighter than anything else in the night sky (from our location).

[alan potts]

It is just as well Mars takes magnification, it is so small we would never see it if it didn't.

Alan