Someone Please Explain

Discuss telescope eyepieces.
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Bigzmey United States of America
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Re: Someone Please Explain

#21

Post by Bigzmey »


Ylem wrote: Mon Nov 18, 2019 1:38 am
notFritzArgelander wrote: Mon Nov 18, 2019 12:08 am
Ylem wrote: Sun Nov 17, 2019 11:40 pm Interesting thread, I do not own a Barlow. But have always wonder if there would be any advantage in using one in an ST80?
Would there be any advantage to Barlowing a 20mm EP over just using a 10mm EP?
It depends on what you want, what are your requirements"

If you are worried mostly about cost and eye relief then great! Go for it!

If you want the best quality image and to improve your observing skills? Nope. The images will deteriorate slightly. If getting the most out of your Mark I eyeball, no again. It's like playing a musical instrument, you need to practice on a good enough axe that allows you to improve your skills. You can stop your observing skills from developing by using less than stellar gear.

Would you give a cardboard violin shaped object or guitar shaped object as encouragement? I wouldn't.
Yeah, that's what I have kinda thought. Hence I have never had a Barlow ;)
I played with barlows and fast achros mainly to see if they would improve performance on planets. Nope, you get better results if you stop down ST80 or any other fast achro.

Good quality barlows can clean up views from lesser EPs, but as nFA indicated even the best barlows slightly degrade views through good quality EPs, mainly through light scatter. It is most noticeable with Orthos.

I prefer dedicated fixed length EPs to zooms and barlows. But they do provide utility, in fact my air travel EP set consists of Baader Mark IV zoom and Baader Q-barlow. :D
Scopes: Stellarvue: SV102ED; Celestron: 9.25" EdgeHD, 8" SCT, 150ST, Onyx 80ED; iOptron: Hankmeister 6" Mak; SW: 7" Mak; Meade: 80ST.
Mounts: SW: SkyTee2, AzGTi; iOptron: AZMP; ES: Twilight I; Bresser: EXOS2; UA: MicroStar.
Binos: APM: 100-90 APO; Canon: IS 15x50; Orion: Binoviewer, LG II 15x70, WV 10x50, Nikon: AE 16x50, 10x50, 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Panoptic & Plossls; ES: 68, 62; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV.
Diagonals: Baader: BBHS mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: 2" prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S, 6-color set; Astronomik: UHC.

Observing: DSOs: 3106 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 2180, S110: 77). Doubles: 2382, Comets: 34, Asteroids: 255
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Shorty Barlow
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Re: Someone Please Explain

#22

Post by Shorty Barlow »


I have a large collection of Barlows, ranging from simple 1.25" shorties (Barsta, GSO), more sophisticated shorties, to full length 2x, 3x and 5x Barlows including Tele Vue and Vixen. I also have 2.5x and 5x TV Powermates. Not forgetting the Baader Hyperion Zoom Barlow that I don't use. I only have two 2" Barlows; a Luminos and a GSO.

In my opinion the difference in optical quality between the 1.25" Barlows is minimal visually, although the Baader Q-Barlow and TV 3x are extremely good.

My 2" Barlows seem very good for what they are and don't appear to degrade the image particularly. Out of these the Luminos is used more often, almost exclusively with the BHZ.

It seems to me that the polarity of opinion about Barlow use is dependent on how they are actually utilised.

For me, their main use is to rapidly enable a short tube refractor to become more viable as a lunar/planetary scope. In this way I can switch from rich field observing with my ED72 to lunar observing by simply using a 3x Barlow (usually a Celestron X-Cel) and a zoom.

I've been down the road of trying to alter 2" eyepiece performance with a Barlow. All it does is add extra weight and contribute to vignetting. I see no advantage in either placing a 2" eyepiece in a Barlow or threading a 2" Barlow element onto an existing 2" eyepiece. I did actually try this once with a 32mm GSO RK and the 2" GSO Barlow element. There was some improvement in edge astigmatism, but there was a cost in diminished field and some vignetting, notwithstanding the added weight.

There are certain topics in amateur astronomy that always seem to degenerate into binary arguments. Filters and their use are a typical example. I'm not entirely sure why this happens. Barlows are a prime example of this polarity. I should imagine that there have been discussions about the efficacy of Barlow lenses ever since Peter Barlow FRS built the first one in 1833.
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GCoyote United States of America
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Re: Someone Please Explain

#23

Post by GCoyote »


Ylem wrote: Sun Nov 17, 2019 11:40 pm Interesting thread, I do not own a Barlow. But have always wonder if there would be any advantage in using one in an ST80?
Would there be any advantage to Barlowing a 20mm EP over just using a 10mm EP?
1. How is that possible? Everything from the starter scope to the eyepiece set comes with a Barlow. I'm thinking of cutting them up for parts!

2. I'm not clear on the use of 'orthoscopic' in this context. Anyone?
Any metaphor will tear if stretched over too much reality.
Gary C

Celestron Astro Master 130mm f5 Newtonian GEM
Meade 114-EQ-DH f7.9 Newtonian w/ manual GEM
Bushnell 90mm f13.9 Catadioptric
Gskyer 80mm f5 Alt/Az refractor
Jason 10x50 Binoculars
Celestron 7x50 Binoculars
Svbony 2.1x42 Binoculars
(And a bunch of stuff I'm still trying to fix or find parts for.)
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kt4hx United States of America
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Re: Someone Please Explain

#24

Post by kt4hx »


Juno16 wrote: Sun Nov 17, 2019 12:30 pm I have the Starguider 12mm and 8mm and they work quite well in my f7 scope considering they are inexpensive eyepieces. They do cheapo barlow nicely on bright targets like planets and brighter double star pairs.

Thanks,
Jim
I used to have some of those under both the Agena Starguider and Astro-Tech Paradigm labels. I actually compared the 12mm to the ES 82 11mm. Putting aside the obvious AFOV differences, at f/5 the Starguider did quite admirably. For their price point they are quite nice overall. but of course they cannot keep up with some other designs. I will say the 25mm I used to have was pretty rough in an f/4.4 Newt, but that was as expected. :)
Alan

Scopes: Astro Sky 17.5 f/4.5 Dob || Apertura AD12 f/5 Dob || Zhumell Z10 f/4.9 Dob ||
ES AR127 f/6.5 || ES ED80 f/6 || Apertura 6" f/5 Newtonian
Mounts: ES Twilight-II and Twilight-I
EPs: AT 82° 28mm UWA || TV Ethos 100° 21mm and 13mm || Vixen LVW 65° 22mm ||
ES 82° 18mm || Pentax XW 70° 10mm, 7mm and 5mm || barlows
Filters (2 inch): DGM NPB || Orion Ultra Block, O-III and Sky Glow || Baader HaB
Primary Field Atlases: Uranometria All-Sky Edition and Interstellarum Deep Sky Atlas
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"Astronomers, we look into the past to see our future." (me)
"Seeing is in some respect an art, which must be learnt." (William Herschel)
"What we know is a drop, what we don't know is an ocean." (Sir Isaac Newton)
"No good deed goes unpunished." (various)
Some people without brains do an awful lot of talking, don't you think?” (Scarecrow, The Wonderful Wizard of Oz)
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