15mm Altair ULTRAFLAT

[Nightspore]

I originally acquired the 15mm Altair ULTRAFLAT in April 2019 for my 80ED DS Pro Evostar. It was a month later that I managed to get first light with the 15mm Altair EP. Fast forward a couple of years and it really hasn’t been used since then. There are various reasons for this situation. I initially bought the ULTRAFLAT eyepiece to solve a weight problem. Not my weight obviously as I’m a bit skinny. A 15mm focal length EP gives a 2mm exit pupil for 40x on the 80ED, which is a great mid-range magnification for the scope, particularly for many open clusters.

 

At the time I carried the 80ED out in its supplied ‘Jason Statham’ hard case instead of a soft (and therefore lighter) bag. The case had provision for accessories, including eyepieces. Progressively over time the case seemed to get unnaturally heavy. I was taking a 15mm Celestron Luminos out in the case among other eyepieces and assorted accessories. I’m one of the few people who actually like the Luminos range. The eye relief and eye placement suit me and the overall ergonomics are very good. The 82° FOV and large field stop are outright luxurious. I even like the twist-up eyeguard and excessively shiny housings (well sort of).

 

I can live with some of its peccadilloes like the slight edge of field brightening and occasional glaring. However, I just can’t live with its weight. The Luminos is 140g heavier than the 15mm Altair which is just over 200g. I have a much smaller 15mm GSO SuperView, and although I like it a lot, it just wasn’t the same. I even have a 16mm T5 Nagler which is very lightweight and the dreaded ‘ring of fire’ wouldn’t be a problem for rich field. I’m not a fan of long eye relief and can tolerate quite short lengths for lunar and planetary viewing. I’ve always considered the T5’s 10mm relief was ample for concentrating on high magnification targets but I wasn’t keen on it for low power sweeping. The Luminos was also unwieldy in the 80ED’s stock focuser which doesn’t rotate.

 

The ULTRAFLAT series were apparently designed in the US by Mark Ackermann and are actually manufactured by Kunming United Optics. APM owned the exclusive rights for two years. They are now sold under a variety of brand names and housing liveries. Although the range has ‘only’ a 65° AFOV they were reputed to have a very flat, sharp field.

 

 

It’s very similar in size and weight to a 19mm Tele Vue Panoptic and even resembles it in many respects. It had 5° of field over my 15mm TS Optics Planetary EP and was smaller and more compact. The barrel had no undercut but was equipped with Baader-style safety kerfs. Which is almost as good as a smooth barrel.

 

I was quite impressed with the Altair when I first used it with the 80ED. It was easily rotated in the diagonal. The field was incredibly flat with a dark background and the colour separation and acuity were superb. As far as I could tell it was like this right up to the field stop with no discernible chromatic or spherical aberrations. I could detect no eye placement issues and the purported 16mm eye relief felt comfortable for rich field sweeping.

 

However, the rubber eyeguard seriously started to bug me. There’s nothing actually wrong with it and it can be rolled down out of the way. For most people it wouldn’t really be a problem. I’m partially paralysed in my right hand and arm. So fiddling about with stubborn rubber eyecups can regularly involve getting greasy fingerprints on the eye lens.

 

 

Recently I’ve discovered that I have a spare Baader lens cap that fits the eyepiece with the guard rolled down. This does change things a bit and I plan to use this lightweight eyepiece with small aperture grab and go refractors more often.

 

 

For the 80ED The ULTRAFLAT was eventually replaced by a 15mm Tele Vue DeLite. Once I’d changed the Evostar stock focuser to a rotating one I felt much happier placing a larger or heavier eyepiece into the diagonal.

 

 

I'm looking forward to getting the 15mm ULTRAFLAT out more often.

[+Streetbob]

I have an Altair 15mm Ultraflat too and it tends to be my go to ep. The 62^o fov is better than 82^o for me as I wear varifocals at the eyepiece and don’t get the full advantage of larger fovs. I’ve been thinking of trying other focal lengths as well.

[Nightspore]

2 hours ago, Streetbob said:

I have an Altair 15mm Ultraflat too and it tends to be my go to ep. The 62^o fov is better than 82^o for me as I wear varifocals at the eyepiece and don’t get the full advantage of larger fovs. I’ve been thinking of trying other focal lengths as well.

 

I often wonder what the other focal lengths are like. Although it performs well, it's the small compact size that appeals to me about the 15mm. The 10mm looks interesting. I wish they had better eyeguards though lol.

[+Streetbob]

The eyeguards aren’t a problem for me the Es eyepieces have folded down guards which I have to fold up. Horses for courses as they say.

[+Bino-viewer]

Thanks for sharing your findings 🙂

I have the APM version (15mm/65º)

 

I've been pretty pleased with them and think they are a good value eyepiece at £119

They give me 170x magnification in my larger refractor, which is as much as i ever need on most nights.

The smooth barrels are right down my street ; my only niggle is that i find the top dustcaps a bit tricky to replace.

 

 

 

[Nightspore]

1 hour ago, Streetbob said:

The eyeguards aren’t a problem for me the Es eyepieces have folded down guards which I have to fold up. Horses for courses as they say.

 

Don't get me started about Baader and Tele Vue Plossl eyeguards lol.

[Nightspore]

1 hour ago, Bino-viewer said:

Thanks for sharing your findings 🙂

I have the APM version (15mm/65º)

 

I've been pretty pleased with them and think they are a good value eyepiece at £119

They give me 170x magnification in my larger refractor, which is as much as i ever need on most nights.

The smooth barrels are right down my street ; my only niggle is that i find the top dustcaps a bit tricky to replace.

 

 

 

 

You're welcome. I seriously considered a 15mm pair for my bino to replace the 15mm SuperViews. You can see from the picture I replaced the stock SuperView sticky-up eyeguard with easily rolled down ones.

 

 

The SuperViews are half the weight of the 15mm UFF and as I only really use them to look at the Moon (and possibly M42) with my 127mm Mak I never bought a second ULTRAFLAT. The safety smurfs, I mean kerfs, probably don't do anything really. It's nice to see a general tendency now for OEM's and distributors to abandon the undercut defect.

Edited October 6, 2021 by Nightspore

[DeanWatson]

I have the 30mm 2 inch Altair (what is it with us and mixing metrics...?!) and its just about, short of my Apo, one of the nicest pieces of glass I own.

[Nightspore]

On 07/10/2021 at 16:36, DeanWatson said:

I have the 30mm 2 inch Altair (what is it with us and mixing metrics...?!) and its just about, short of my Apo, one of the nicest pieces of glass I own.

 

You mean the 1.181 inch, 2 inch? Or is that the 30mm, 50.8mm? lol

 

The 30mm looks very nice. Might be a tad heavy for smaller scopes though.