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Old 31-03-2024, 10:24 AM
refractordude
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Should I Buy The SVbony 135 7-21 Zoom

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
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Old 01-04-2024, 08:07 AM
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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.
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Old 01-04-2024, 10:21 AM
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Don Pensack


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


Thanks
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Old 01-04-2024, 10:35 AM
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GSO 1.25" 2X Shorty Barlow
Celestron Omni 1.25" 2X Barlow
Baader Q Barlow 1.25" 2.25x
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Old 01-04-2024, 10:42 AM
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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.
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Old 01-04-2024, 11:35 AM
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doug mc

Is this the barlow you and Don are recommending?

Thanks
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Old 01-04-2024, 03:10 PM
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No, it's this one:
https://agenaastro.com/gso-1-25-2x-a...rlow-lens.html
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Old 01-04-2024, 05:40 PM
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Quote:
Originally Posted by refractordude View Post
doug mc

Is this the barlow you and Don are recommending?

Thanks
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.
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Old 02-04-2024, 12:26 AM
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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.
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Old 02-04-2024, 06:40 AM
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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

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Old 06-04-2024, 08:46 AM
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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
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Old 06-04-2024, 04:16 PM
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GSO is the manufacturer.
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Old 11-04-2024, 04:58 AM
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doug mc


I have an email response from High Point Scientific that sells the Aperture barlow.
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Old 13-04-2024, 05:07 AM
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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.
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  #15  
Old 13-04-2024, 06:36 AM
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Don Pensack

Cool
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Old Yesterday, 03:00 PM
refractordude
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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.

Last edited by refractordude; Today at 06:36 AM.
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