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Altair Astro Ultraflat 24mm 65°


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I'm considering replacing my Celestron 25mm 60° eyepiece. I've owned it two years and now fancy moving up to a more premium eyepiece.

The Explore Scientific 24mm 68° seems to be the one based on price vs performance reviews. To be honest, with the proceeds of the Celestron sale, the ES priced at £155 is the most I can afford.

However, they're out of stock everywhere except Ali Express at cut down prices even but I don't want to go there.

I've noticed Altair have a range of premium eps.The Altair Ultraflats received a favourable review in Sky at Night Magazine. The 24mm 65° caught my eye and at £135 it's £20 cheaper than the ES.

The specs look decent, but do any of the eyepiece gurus here have experience of this Altair range or any clones? Should I just hold out for the ES 24mm 68°? Thanks.

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Edited by ScouseSpaceCadet
Ali Express...
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The Altair is the same optically as the APM, so if you search for that you will find more reviews. The general consensus is that they are very good eyepieces and one would be a worthy alternative. 

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Just now, Ricochet said:

The Altair is the same optically as the APM, so if you search for that you will find more reviews. The general consensus is that they are very good eyepieces and one would be a worthy alternative. 

Thanks.

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Here's my comparison image of ~24mm eyepieces.  Your 25mm Celestron is probably similar to the 25mm Meade HD-60.  The 24mm APM UFF is optically identical to the Altair Astro.

It's a decent eyepiece that suffers a bit toward the edge.  I much prefer my 22mm AT AF70 (Omegon Redline, TS Optics Expanse) for just a bit more TFOV.  However, it does require a 2 inch focuser.

578339646_23mm-28mm2.thumb.jpg.f77e023a4bf75f823a79732e878b16b0.jpg1537884485_23mm-28mmAFOV2a.thumb.jpg.c95b4ccbeec2d7c0173289fcb5ca9ea2.jpg

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In my f/7 apo, the 24mm APM UFF has a better edge of field than the ES 24x68.

Both are not quite up to the standard of the TeleVue 24mm Panoptic, though.

But the APM is the only one of those 3 24mm eyepieces compatible with glasses.

 

As for true field size, the 22mm 70° eyepiece Louis mentions is a great alternative if you have 2" eyepiece capability.

Now sold as:

Arcturus Ebony
Astromania SWA
Omegon Redline
Skywatcher SWA
Telescope Service

Expanse ED

They might be available used as an Astrotech AF70, an Olivon 70, or a Celestron Ultima LX

My calculations show a 26.9mm field stop in that eyepiece versus a 27.2-27.3mm field stop in the APM, which is close enough the field size is pretty much the same.

Measurements of the others show 27.0-27.2mm, so all of these can be safely considered to have roughly the same true field size.

 

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From my yard stick field stop measurements:

24mm APM UFF: 27.5mm FS

22mm AT AF70: 28.4mm FS

There is a bit of falloff/fuzziness for the APM at the edge, so it's not a good, clean 27.5mm FS.  Measured AFOV=63°, eAFOV=66°

The AF70 has low distortion toward the edge, helping maximize its TFOV. Measured AFOV=70°, eAFOV=74°:

1833175478_18mm-22mm.thumb.JPG.b2a9f1289172154a138f3813b09da0a4.JPG1381562251_18mm-22mmAFOV.thumb.jpg.88386d195597c48c65f2953c28d718d7.jpg

Edited by Louis D
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The 22mm Astrotech/Olivon/Omegon and clones are excellent and a real steal at the price. It's a real hidden gem.

The only reason I sold my Omegon recently is that it's a 2 inch eyepiece.  Had it been a 1.25 inch I'd still have it.

 

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