I say that a lot too lol.

I got to see a twilight Saturn at 180x with the 5mm SW UWA. It didn't disappoint me and I doubt an Abbe orthoscopic would have done much better. I could see the Cassini Division and some surface detail but it was too light to see any moons unfortunately.


After Saturn became too low to comfortably observe I spent the next two and half hours first looking at prominent stars and MO's around Ursa Major and for the last hour and a half looking at the rich star fields to the south.



There was a lot to see at 47.3x with a 19mm Panoptic. I get a good 2.75mm exit pupil with the Panoptic which is just enough to get away with a Baader UHC-S sometimes.



Difficult to pick a highlight but I thought the Lagoon Nebula looked good until I lost the transparency, I could see the Trifid Nebula as well of course. I've always loved the sparkling effect of stars seen through the M8. I tried the Celestron 40mm Plossl for a short while with the UHC-S, but the 22.5x wasn't enough for me, regardless of the 5.7mm exit pupil. I forgot just how good that 19mm TeleVue Panoptic was in the Bazooka. I think it's possibly one of the most underrated TeleVue eyepieces ever.



Of course, they looked more like this to me lol.

 

I have no explanation for the price differential Ray. Over her the SW's are more or less the same price, although some retailers have slashed the prices on some f/l's, which seems to be what's happening your side of the pond. It may be that they want to get rid of old stock or something. Usually, if something is too good to be true, it isn't lol. I have a feeling these Barsta UWA's aren't edge blacked. There is some EOF darkening, but it doesn't really bother me as it's only in the last 2 or 3 degrees off axis. It may explain the lower prices of these EP's. It certainly won't stop me using these Barstas though. The 7mm sounds like a bargain anyway.


Weather's looking good so I may go out nebula hunting again tonight.



Time to get the Morpheus out I think. I can get a 2.1mm exit pupil on this for about 64x.

 

If you're getting it for a bargain/reduced price it can't be bad. It's bound to be useful some day lol. I bought the Dalek, I mean the 14mm Baader Morpheus, primarily for the Big Cat. Yet it's turned out to be surprisingly useful on the Bazooka. I saw Mars at Opposition with it (albeit plugged in to the TV x3 Barlow) and last night got a really nice view of the Trifid (M20) with the Baader UHC-S threaded into it. It gave me x64 for a 2mm exit pupil. I directly compared it to the dumpy 19mm Panoptic (also with the UHC-S). The image was better with the Dalek than the Dumpy I thought (bigger anyway). Mind you, the Dalek's huge. Remember the argument we had with a certain know-it-all jobsworth about the UHC-S? Well, everything I said then was vindicated last night with the Dalek and the UHC-S. Like I said then, regardless of what subjective opinions are on the efficacy and light curve of the UHC-S, it does work well on smaller aperture scopes. On some targets it will work well between a 2-4mm exit pupil. I very much doubt you'd get that with more aggressive filters on a scope 130mm or under.



Also, I directly compared the 5mm SW UWA with the 6mm BCO on Saturn last night. Deliberately switching between them to compare views. Apart from the magnification difference (30x) I couldn't distinguish any real difference in quality. In fact, I switched back to the Sky-Watcher and observed Saturn until it was too low for me to see comfortably. So if you can get the 7mm SW UWA for a really low price it's got to be good.

 

I'm not sure about the longer f/l versions as, to me anyway, they seem primarily as planetary eyepieces.


Although that doesn't mean you couldn't use them for anything else. TS have this 25mm which looks very similar to the Sky-Watcher UWA's. With your scope I'd probably go for the 15mm SW/Olivon. I think it will give you a 2.5mm exit pupil for 40x. Probably good for small nebulae lol.



The Trifid didn't quite look this big for me with the Dalek lol, but it is interesting that the UHC-S handled a 2mm exit pupil well.

 

It might be worth investing in a good wide angle low power though. Having said that, the Luminos only gives you 60x on its own doesn't it? That would work well. A 10mm EP only gives me a 1.4mm exit pupil on the Bazooka. So my Luminos or Delos are too powerful. Although I think it only gives you a 1.7mm exit pupil, which is pushing it for a UHC filter.

 

I think the 10mm Luminos would work as a low power eyepiece. But to effectively use an ultra high contrast filter of any sort really requires an exit pupil nearer 3mm or above. Although depending on telescope, overall conditions and target it's possible to get as low as about 2mm.

A 1.7mm exit pupil might be pretty good with some nebulae, after all, I was getting 2mm on the Trifid last night and I thought it looked good. I was getting 64x with the Dalek (14mm). I thought I could see more detail than with the Dumpy (19mm Panoptic) at 47x. Often, more magnification with some emission/reflection nebulae reveals more detail, especially with various filters. The trick is seeing how high you can get the magnification before the image gets too dark.

To calculate the exit pupil just divide the eyepiece focal length by the focal ratio of the scope (easy with SCT's as they're all usually f/10 lol).

So, your scope has f/l of 600mm (I think), divided by the 102mm aperture gives a focal ratio of approximately f/5.8.

The 10mm Luminos divided by f/5.8 gives a 1.72mm exit pupil. If my sums are right. I think you could get away with that with a refractor.

 

For high magnifications, usually without a UHC filter, the smaller the exit pupil the better. I can get 60x per inch on the Moon with the Bazooka (300x). For this, I usually Barlow a 6mm orthoscopic down to 3mm. This gives me an 0.43mm exit pupil. I can tolerate this and it is close to the 0.5mm limit at which the human eye can realistically use. Anything much lower than 0.5mm and I believe the eye struggles with it.

I had an argument with the SGL 'learned pundits' about this once, so I don't ever discuss it there now, and I'm a bit paranoid about talking about exit pupils now on any forum, but I'm fairly sure I'm right about this. In other words, the most efficient high magnification to use with any telescope gives you around 0.5mm. This is around the limit you will see the floaters in your own eyes. These sorts of magnifications are only really useful for lunar viewing IMO. Maybe Mars at times or very distant planets like Uranus where you're trying to see anything at all.

For other high magnifications, an exit pupil of between 0.5 and 1.0mm is perfectly acceptable (I get a 0.58mm exit pupil with a 4mm eyepiece for 225x on the Bazooka for example). These exit pupils/magnifications are good for bright objects like planets but are not so useful for DSO's as a rule. A near 1mm exit pupil can be good for some Messier Objects and splitting binary and double stars. A 7mm EP will give me a 1.01mm exit pupil for 128.5x on the Bazooka.

However, for fainter objects, especially nebulae, a good 2mm of exit pupil is probably the highest magnification you can achieve. If you utilise any sort of filter, especially an aggressive one, it's highly likely you're going to need an exit pupil of at least 3mm or above. I think 6mm is the limit before it ceases to become practical. With the Bazooka that's about a 40mm eyepiece (5.7mm for 22.5x). I tried a 40mm eyepiece on the Lagoon the other night with the Baader UHC-S and it just didn't give a big enough image to be practical.

Regardless of what some claim, I still say that using a narrowband filter on a scope 5" or under is not easy. I live in a Bortle 2 area, in a village on the edge of the greenbelt, at 152 metres above sea level on the edge of a glacial rift valley. The nearest town to me is over a kilometre away to the north east and the nearest city is over 15 kilometres away (also north east). To the south east, south and south west I have little light pollution and I'm at a higher altitude than most of the ground in those directions. I still find that my Lumicon UHC & OIII filters are a tad aggressive for a 13cm scope. Yet I can get a 2mm exit pupil with the Baader UHC-S.

 

Yeah, it's mainly when using aggressive filters that exit pupil can become an issue. The Fringe Killer and Neodymium shouldn't really affect it. I use the Baader Neodymium at 300x on the Moon. Aggressive Wratten filters may be problematical as well though.

 

Basically, the way I see it, anything with a transmission rate of less than 30% is aggressive. #80 A Blue has a 30% transmission and can be used on scopes of 130mm and under without too many problems. But I find #25 Red (14%) too dark. #12 Deep Yellow (74%) isn't always easy and I find #21 Orange (46%) better for twilight/daylight lunar viewing. I also find anything green is often too dark. Although #11 Yellow Green is generally good for Saturn on the Bazooka. #11 isn't a longpass filter though, so may not be blocking too much.