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Nightspore

Luminos: Lemon or Luxury?

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Nightspore

I bought my first Celestron Luminos eyepiece around four years ago. Primarily for a high magnification in a small Maksutov. The thinking was that 82° of FOV would allow me more time to track a planet or the Moon before compensating for right ascension with the slow motion control.
This wasn’t a bad plan and more or less worked with my 10mm Luminos. That is until one day I discovered a large piece of visible debris in the field of view. At the time I didn’t realise that the Luminos has a detachable negative Smyth lens in its drawtube. The entire drawtube can be unthreaded revealing the large field lens to facilitate cleaning. I managed to clean the 10mm. Later I acquired 15mm and 19mm Luminos EP’s. The 19mm has a 2” barrel and is a veritable ‘hand grenade’ weighing in at nearly half a kilo (490 g). The field stop is an equally large and impressive 30mm.

 

TCfzVST.jpg

 

The Luminos series (formerly known as Axiom) generally have a bad reputation for astigmatism and often some mysterious and inexplicable edge of field brightness. The aberrations are supposedly particularly prevalent in fast astrograph Newtonians, where they also have a tendency to produce glare. Last night I gave the 19mm a bit of a session in my f/5.8, 72ED Evostar wondering just how bad it could be compared to my usual 1.25” 19mm TeleVue Panoptic. The Luminos gives about 22x for 3° 42’ TFOV and a 3.2mm exit pupil. The 68° Panoptic produces about 3° of TFOV and has a 21.3mm field stop. The 19mm Panoptic is one of my favourite and most used EP’s.

 

8nJpfwO.jpg

 

I don’t doubt the Panoptic has better quality glass but the 19mm Luminos accounted for itself pretty admirably. The field stop is nearly 9mm wider and the 14 extra arc degrees of field are definitely noticeable. The 490 g weight was not really a problem as the ED72 is nicely balanced on the AZ5 mount and tripod combination. I had no sensation of the strange EOFB that apparently mysteriously disappears when you try to look at it directly. Off-axis is pretty good and the seagulls were only making an appearance right at the edge of field. They were there, but 82° combined with a 3cm field stop sort of compensated for it. I probably got the best view of the Andromeda Galaxy with it last night between the Luminos, Panoptic and a 36mm Baader Hyperion Aspheric.

 

So, what is your experience of the Luminos, lemon or luxury?

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Bino-viewer
3 hours ago, Nightspore said:

So, what is your experience of the Luminos, lemon or luxury?

Interesting post.

I've never owned and used any eyepieces for any length of time that weren't either Vixen or Tele-vue,

so i can't comment on the Celestron Luminos series.

I share your opinion of the 19 Pan though, its also one of my favourites, and together with their 24mm brethren,

my most used pairs, and perfectly suited to binoviewing.

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Nightspore
56 minutes ago, Bino-viewer said:

Interesting post.

I've never owned and used any eyepieces for any length of time that weren't either Vixen or Tele-vue,

so i can't comment on the Celestron Luminos series.

I share your opinion of the 19 Pan though, its also one of my favourites, and together with their 24mm brethren,

my most used pairs, and perfectly suited to binoviewing.

Well you can't really go wrong with Vixen or TV. I have all the TV Plossls but I've nearly got all the NPL's. The 15mm NPL is probably the best 15mm Plossl I've used and it is has orthoscopic-like contrast. In fact I used it the same night I used the Luminos to view Jupiter & Saturn at 140x (it was used with a 5x Barlow). 

 

Luminos eyepieces can start long debates on some forums, I know they don't work well in fast Newt's but they seem to do pretty well in fast refractors. I never expected it to be a Nagler and there are a few things that bug me about it. It doesn't secure well in click locks and relies on tightening the safety screw. I'm not over impressed with the roll up eyeguard either.

 

 The real difference is that the nearest equivalent Nagler, a 17mm Type 4 is £349 and 726 g, and the lighter 19mm Luminos is £140 with a bigger field stop. 

 

I've heard that de-shrouded Luminos pairs are very popular for binoviewing with.

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Nightspore

I had another session with the Luminos.

 

zAoTF92.jpg

 

It was also with the ED72 but this time on a Vixen Porta II/Polaris tripod combo. I spent a bit of time with the 19mm and had a pretty good rich field session.

 

aV7RkOs.jpg

 

It was a Moonless night and quite clear. The seeing was better than the transparency though. The Luminos does display a little EOFB and I'm pretty sure there was a small amount of field curvature. Not as apparent as the curvature on my ES 14mm however. Some people have claimed the Luminos kidney beans slightly, although eye placement can depend on various factors, and I don't recall any problems. I'd question the Celestron claim of 20mm eye relief. All in all I enjoyed using it. The wide view and large field stop really seem to compensate for any deficiencies. I doubt I'll be drop kicking it over the fence any time soon. The so called 'kidney beaning' can be perceived if you move your eye around a lot in an exaggerated fashion. I should imagine this may be a problem for people who need glasses to observe. Again, I don't find it particularly a problem as I don't need eye glasses.

 

Synopsis

In the ED72:

1/ IMO the EOFB isn't that much more than on the Baader 36mm.
2/ Kidney beaning isn't really an issue for me.
3/ Any EOF astigmatism just isn't that much of a concern considering the huge FOV and field stop.
4/ Overall weight feels fine on the Porta II/Polaris.
5/ Any noticeable field curvature isn't a problem and it is significantly less than the 14mm ES.
6/ I'm technically back where I started as originally I bought the Luminos two years ago for the ST80 on the Porta II/Hal-130. I only abandoned it because the 130 tripod wasn't grab'n'go enough for me.
7/ I'm even warming to the twist-up eyeguard.

 

kmM0iLt.jpg

Either way, last night the Luminos still gave the best overall rich field views out of these three.

 

 

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