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First light: Leica Zoom ASPH 17.8-8.9mm


YKSE

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Finally, a 3-hour-session with the new EP after cloudy nights.

The Leica is in its native 17.8-8.9mm, and comparing EPs are mainly BCO 18mm and BCO 10mm, in some cases Maxvision 20mm and 16mm.

The targets are Jupiter, M36, M37 and M13. M42 was in the plan but treed out when it cleared up.

Seeing is about my average in backyard, some mag 4 stars visible naked-eye in the observing area.

Some general impressions about the Leica Zoom:

1. Eye relief : very good, the whole FOV visible all the time with glasses on, it feels like about 16-17mm,  i.e. a little better than HR and BST and just shy of Baader aspheric's 17mm.

2. Stray light controll: excellent, moving Jupiter just outside the FOV, not the slightest hint about where it is.

3. Scatter: About the same level as BCO.

4. Field flatness. The flatest EP I've had, really pin-point stars right to the edge. Maxvision EPs were best before, but still minor astigmatism in outer 5-10%.

5.Par focal: If focus on high mag fist, then no refocus needed, the other way round may need slight adjustment.

6. Clearly more inwards than all my other EPs.

Jupiter: (the whole zoom range) quite steady air, 4 bands and polar caps visible in all EPs, Leica shows a little more details here and there, such as colour variation, extension etc, than BCOs in coresponding focal lengths.

M36: (about 17.8-16mm) about the same as BCO 18mm, better than MV 16mm in showing more fainter stars in this bright cluster, about the same pleasing star colours as MV 16mm.

M37: (about 17.8-16mm) Better than BCO 18mm in showing some real faint stars, while BCO 18mm is a notch better than MV16mm.

M13: (the whole zoom range) Resolves more stars than BCO 10mm, the comfortable ER and wider flat FOV make it easier.

Some other observations:

Eyepiece Outer Field Brightening(EOFB): Yes, there's is a ring of right edge, especially in 17.8mm, by zooming in some what, both intensity and size of the brigtening will reduce. I put the just found M95 on the edge in 17.8mm, it disappeared in the brightness, but zooming in a little, with essentially the same FOV, M95 reappeared.

Sky background: mostly not as dark as seen in MV, about the same as BCO, my guess is better throughput in Leica. When the EOFB is more visible, the center field gets really dark, especially noticable when viewing M37.

First light conclusion: Leica meets my expections with margin, I can continue with the plan of restructuring my EPs :smiley:

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A very nice report Yong. This sounds like something to consider even with my array of fine glass, are you sure the astigmatium is not the scope which may well not show in the BCO's?

Alan

BCOs have 52 deg FOV, wider than conventional orthos. With no aspheric lens, this increased FOV seems to introduce some fussiness in about 10% afre, not affecting the clearity though.

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Great report Yong. I assume you were using the C8 for these observations ?

If it's matching or slightly improving on BCO's then it's doing well :smiley:

Mind you, the fact that the BCO's run something exotic like this so close for £50 a throw is impressive too. 

I agree with you regarding the outer 10% of the FoV of BCO's - it's there for framing rather than critical observing is my conclusion !

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Great report Yong. I assume you were using the C8 for these observations ?

If it's matching or slightly improving on BCO's then it's doing well :smiley:

Mind you, the fact that the BCO's run something exotic like this so close for £50 a throw is impressive too. 

I agree with you regarding the outer 10% of the FoV of BCO's - it's there for framing rather than critical observing is my conclusion !

Yes, It's C8, Just forgot to write it.

I'll do a second run with 80ED to test the VIP barlow combinations.

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Mind you, the fact that the BCO's run something exotic like this so close for £50 a throw is impressive too. 

I totally agree. 18mm is a perfect choice for beginers who want an inexpensive new mid focal length EP, and the whole BCO kit priced at FLO is a great beginers' choice for those who doesn't wear glasses, IMHO.

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Oh, man! I shouldn't read these reports :)

Sounds as if it could be the ideal eyepiece for a minimalist setup - reducing clutter to carry about and the need for eyepiece changes, while still giving great quality views.

Thank you for the careful and detailed write-up.

John

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