Should I Buy The SVbony 135 7-21 Zoom

[refractordude]

Hello there


Has anyone own/tried this zoom? Did you experience kidney beaning and or blackouts? What would be a good budget 2X barlow to team it up with.


Thanks all

[Don Pensack]

The tested apparent field varies from 39° at 21mm to 55° at 7mm.
Are you sure you want an eyepiece this narrow?
Does your scope track? Are you primarily a planet observer?
If the answer to both is yes, then it might be fine.
But otherwise, the extremely narrow field will hobble your scope and seriously reduce the size of objects you can view.

[refractordude]

Don Pensack


Will be using it for the planets when in season and the Moon. What will be a good budget 2X barlow?


Thanks

[Don Pensack]

GSO 1.25" 2X Shorty Barlow
Celestron Omni 1.25" 2X Barlow
Baader Q Barlow 1.25" 2.25x

[doug mc]

As Don stated, the field of view is narrow at low magnification setting. I have this zoom and it works very well. I have not noticed blackouts or kidney beaing. You may not need a barlow at the 7mm setting, as that may be high enough power. There is a good GSO 2.5x barlow in the classifieds at the moment. It's really 2.2x apparently, so get that one if you think you need it. Excellent reviews all around the Web on that one for the price. It's the Bintel 2.5x barlow being sold by Morton.

[refractordude]

doug mc

Is this the barlow you and Don are recommending?

Thanks

[Don Pensack]

No, it's this one:
https://agenaastro.com/gso-1-25-2x-achromatic-barlow-lens.html

[doug mc]

It looks like Don is showing the standard GSO 2x barlow in the link.The one MortonH is advertising is a three element apo barlow. Most people recommend the 2.5x apo barlow over the standard 2x model. It's the one I'd choose at that price.

[Don Pensack]

The request was for a good 2X budget Barlow, so I mentioned the 2-element GSO, which is the same as the Celestron Omni.
There is no reason to make a 3 element Barlow unless the purpose is to make the Barlow higher power, or shorter in length without necessitating extreme curves on the lenses.
It really depends on the eyepiece focal lengths whether a 2x or 2.5x will be more useful.
I don't have any objections to the 2.5X GSO if the magnifications resulting are not too high for the seeing conditions.

[refractordude]

For high power I am using the Long Perng 9mm, 6mm, 5mm, and an Agena 1.25" zoom 8-24mm with a cheapo eBay 2X barlow. Eye placement with the Long Perngs and Agena zoom is not that good. Will buy the GSO 2.5 Apo barlow and the Svbony 7-21mm zoom. Will report back after next date with the Moon.



Thanks to you all

[refractordude]

Hello there Don Pensack and doug mc


Do the Apertura 2x5 1.25" Apo barlow and GSO share the same manufacture. I could not find more numbers for the Apertura. Thanks all

[doug mc]

GSO is the manufacturer.

[refractordude]

doug mc


I have an email response from High Point Scientific that sells the Aperture barlow.

[Don Pensack]

There is no issue with purchasing the GSO Barlow under other labels. There are at least 10 companies selling GSO Barlows under private label names.
If the Apertura is cost effective for you, it would be fine.

[refractordude]

Don Pensack

Cool

[refractordude]

Just got back in from an observation of the Moon with the Svbony 7-21 zoom lens and my Celestron 150mm F8 achromatic. The GSO APO barlow has yet to arrive. Even using a cheapo eBay 2x barlow the Moon's crater edges were very sharp. While looking at a cluster of craters the view was sharp to the edge. It has very good eye relief. I can take in the entire view from the lowest to highest mag. There was no kidney beaning and no blackouts. This Svbony very much bested the Agenaastro and Celestron budget zooms I use to own. It also bested the Long Perng 9mm, 6mm, and 5mm eyepieces.

My eyepiece starters are:

Meade 2" 56mm Super Plossle
Celestron/APM 2" 30mm UFF
Astromania/Olivon 2" 22mm
Agena Starguider/Paradigm 1.25" 15mm and 12mm
Svbony 1.25" 7-21 Zoom with Barlow

Bench warmers:

GSO 1.25" 32mm Plossle
GSO 1.25' 20mm Superview
Agena 1.25" Super Wide Angle 15mm
Gold Line 1.25" 6mm
Ebay 1.25" 2x Barlow

Thanks all for your help.

[refractordude]

Forgot to mention that the Orion Planetary eyepieces also known as Long Perng Long Eye Relief can be gotten at First Light Optics in England for a lower price. This in spite of shipping cost to the USA. Orion is a good company but business is business. Also the GSO Superview 20mm is a great eyepieces at it's price. It was my first eyepiece upgrade. It really is good on my two F8 refractors.

[Don Pensack]

The Long Perng LER "planetary" 55° eyepieces are sold under several labels:
Altair Astro (UK) Lightwave LER Planetary
Bintel Premium LER
Founder Optics Alien
Lacerta Super Planetary
Long Perng LER
Omegon LE Planetary
Orion Edge-On Planetary
Sky Optic (France) Elyth
Stella Lyra (FLO) Long Eye Relief

The GSO 20mm Superview is also sold under other labels, like Apertura and Bintel.

[refractordude]

The APO barlow arrived so back outside for another test. The cheapo no name eBay barlow is just as good. My target was two small twin craters. One crater had a structure inside of it. I tested the two over and over again against that structure. However, I could not find a noticeable difference in sharpness. It written on the side of the eBay barlow FMC.


I also tested the Svbony zoom against the GSO Superview 20mm and the Agena Starguider/Astro-Tech Paradigm 15mm. Testing at the same magnification the Paradigm was equal to the Svbony zoom. The Superview was slightly not as sharp.


Once again thanks for all the help I have gotten.