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2x, 2.5x or 3x Barlow lens?

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#1 APR28

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Posted 23 September 2019 - 02:55 PM

My Celestron XLT 102 is showing up tomorrow. Is anything above a 2x Barlow overkill for my quality or type of telescope?
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#2 Jim Waters

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Posted 23 September 2019 - 03:05 PM

What lenses will you be using?



#3 APR28

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Posted 23 September 2019 - 03:07 PM

Celestron 8-24mm zoom and 32mm
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#4 Jim Waters

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Posted 23 September 2019 - 03:20 PM

You scope f.l. is 1000mm.  Your zoom 8mm will give you 125x power which is approaching the optical limits of your scope.  I wouldn't do anything until you get your scope.  Invest in good quality eyepieces.

 

The zoom lens optical performance may will be less than expected.

 

EDIT - Sell the zoom.


Edited by Jim Waters, 23 September 2019 - 05:12 PM.

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#5 sg6

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Posted 23 September 2019 - 03:55 PM

If 1000mm focal length then stick with the zoom to find out how you get along. At 8mm I would not expect much more from the scope, a 6mm may work at times but not often. So a barlow will not really give you anything. If impatient buy a 6mm instead.

 

Never sure of how good a zoom is these days, but you are not going to get the quality and fields of what amounts to 5 eyepieces in one package at the cost of one eyepiece. Something has to give.

 

My future preference would be an 8mm and 12mm eyepiece with the 32mm you have. Something along the Paradigm specification and cost.

 

Maybe a bit unfair but although I read often the guidance to get a zoom and have multiple focal lengths, I actually know of no-one that either owns one nor uses one.


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#6 aeajr

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Posted 12 October 2019 - 11:15 PM

I always recommend you provide a link to your scope to be sure we know what scope you are talking about.

 

Is this your scope?

https://www.celestro...t-102-telescope

 

Optical Design Refractor
Aperture 102mm (4.02")
Focal Length 1000mm (39")
Focal Ratio 9.8
Focal Length of Eyepiece 1 25mm (0.98")
Magnification of Eyepiece 1 40x

Finderscope 6x30

 

The amount of magnification you can use will depend on several factors:

  • the target you are trying to view
  • the transparency of the atmosphere the night
  • the seeing that night
  • the light pollution level may come into play on some targets

If your primary eyepiece is the Celestron 8-24 zoom, as you posted above, I like mine, that eyepiece will give you 41X to 123X in that scope.  So, if you want to barlow that eyepiece I would use a 2X barlow for 82 to 246X with that eyepiece.   

 

Note that you are unlikely to be able to use anything over 200X on a regular basis, except perhaps on the Moon, and only on exceptionally good nights. Many nights I would expect you will not be able to exceed 150X, based on target, seeing and transparency conditions. Other nights 200X may work just fine.

 

 

Understanding Telescope Eyepieces- There are recommendations, based on budget, but the meat of the article is about understanding the issues when selecting eyepieces.
https://telescopicwa...cope-eyepieces/

 

 

Understanding and using a Barlow Lens
https://telescopicwatch.com/?s=barlow


Edited by aeajr, 13 October 2019 - 04:57 AM.

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#7 BFaucett

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Posted 13 October 2019 - 12:13 AM

Just a note: There are two Celestron Omni XLT 102 refractors.  

 

Celestron Omni XLT 102, FL=1000 mm  f/9.8

https://www.celestro...t-102-telescope

(As linked to by aeajr above.)

 

Celestron Omni XLT AZ 102, FL=660 mm  f/6.5

https://www.celestro...omni-xlt-az-102

 

 

Hopefully, the OP will let us know which one he has. 

 

Bob F.  


Edited by BFaucett, 13 October 2019 - 12:45 AM.

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#8 BFaucett

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Posted 13 October 2019 - 12:38 AM

Celestron 8-24mm zoom and 32mm

 

For starting out, I think that is a very usable combination. I now have some other (and more expensive) eyepieces but I still frequently use my Celestron 8-24 Zoom eyepiece. (I also have the Meade version.)

 

For now, I wouldn't even bother with a Barlow; use what you now have and get used to using the telescope. But, IMHO, a 2x Barlow would be okay if you want to get one. You could experiment with it and see for yourself. Personally, I wouldn't go with a Barlow higher than 2x at this time. 

 

Just my two cents,

Bob F.



#9 HouseBuilder328

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Posted 13 October 2019 - 02:01 PM

If 1000mm focal length then stick with the zoom to find out how you get along. At 8mm I would not expect much more from the scope, a 6mm may work at times but not often. So a barlow will not really give you anything. If impatient buy a 6mm instead.

 

Never sure of how good a zoom is these days, but you are not going to get the quality and fields of what amounts to 5 eyepieces in one package at the cost of one eyepiece. Something has to give.

 

My future preference would be an 8mm and 12mm eyepiece with the 32mm you have. Something along the Paradigm specification and cost.

 

Maybe a bit unfair but although I read often the guidance to get a zoom and have multiple focal lengths, I actually know of no-one that either owns one nor uses one.

 

I have heard so many good things about the Hyperion Baader Zoom with Barlow 2.25.  Would you say this is a good quality zoom for convenience or would still go with separate eye pieces?  The price of this item is much higher than the Celestron zoom and I've hard it is much better quality as well.

 

https://www.highpoin...with-hyp-barlow



#10 aeajr

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Posted 13 October 2019 - 03:35 PM

I love my BH Zoom. I don't have the 2.25 Barlow.

I also have ES82 eyepieces.

I use the 24-16 part of the range but spend most of the time in the 16-8 part of the zoom range.

#11 Redwin

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Posted 16 October 2019 - 03:25 PM

Hello. I am going to tag on to this post because it is asking the same question I have. I have a AWB OneSky Reflector Telescope (https://shop.astrono...ector-telescope) with the 10mm and 25mm eye pieces for about a month now. I have been able to see both Saturn and Jupiter which made me super excited, but I would like to see more if my scope allows for it. I am slowly scanning my way through jlandy's massive thread looking for nuggets about eyepieces, but there is a lot of stuff in there and I have probably missed nine useful tips for every one I have found so far. Would something like a Vixen Optics 2x Barlow Lens (1.25") with Built-In T-Mount Adapter (https://shop.astronomerswithoutborders.org/collections/frontpage/products/vixen-optics-2x-barlow-lens-1-25-with-built-in-t-mount-adapter) be recommended for this scope or should I go in a different direction? I do not have deep pockets, but I would prefer to buy quality at a reasonable price over a cheap alternative that may or may not get the job done.

 

Thank you for your time.

 

v/r

Alan


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#12 Hugh Peck

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Posted 16 October 2019 - 03:58 PM

You don't need a built in T-adapter unless you're planning on hooking a DSLR to it, which might be a bit much weight for the scope. On the other hand it is a decent Barlow, I had one, particularly if you're on a budget and the built in T-adapter may come in handy in the future. 


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#13 vtornado

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Posted 16 October 2019 - 04:39 PM

The AWB one sky is different than the 100mm f/10 refractor.

First the aperture is significantly larger, and second the f ratio is f/5 vs f10.

 

With that in mind,  and I have the AWB, it works best for planetary (high power) with a 5 mm eyepiece.

You could get that by using a 2x barlow and a 10mm eyepiece or buying a native 5mm eyepiece.

Do you know how to collimate your AWB?  The higher the power the more necessary collimation 

is.  The collapsible design means you need to collimate each time if used for high power.

 

For the refractor the member has an 8-24mm zoom eyepiece.  For this telescope I think

that 8mm is getting close to the highest power that one should use.  If they are really

bent on using more power a 2x barlow will give them 4-12mm.  Some of this range

may not be useable on most nights, and mostly for lunar, or double star observing,

but balrows are inexpensive and not much risk to try.



#14 aeajr

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Posted 16 October 2019 - 04:54 PM

Hello. I am going to tag on to this post because it is asking the same question I have. I have a AWB OneSky Reflector Telescope (https://shop.astrono...ector-telescope) with the 10mm and 25mm eye pieces for about a month now. I have been able to see both Saturn and Jupiter which made me super excited, but I would like to see more if my scope allows for it. I am slowly scanning my way through jlandy's massive thread looking for nuggets about eyepieces, but there is a lot of stuff in there and I have probably missed nine useful tips for every one I have found so far. Would something like a Vixen Optics 2x Barlow Lens (1.25") with Built-In T-Mount Adapter (https://shop.astronomerswithoutborders.org/collections/frontpage/products/vixen-optics-2x-barlow-lens-1-25-with-built-in-t-mount-adapter) be recommended for this scope or should I go in a different direction? I do not have deep pockets, but I would prefer to buy quality at a reasonable price over a cheap alternative that may or may not get the job done.

 

Thank you for your time.

 

v/r

Alan

Alan,

 

You might find these helpful.

 

Understanding Telescope Eyepieces- There are recommendations, based on budget, but the meat of the article is about understanding the issues when selecting eyepieces.
https://telescopicwa...cope-eyepieces/

 

Understanding and using a Barlow Lens
https://telescopicwatch.com/?s=barlow

 

How to Use a Telescope:  First Time User’s Guide
https://telescopicwa...ope-user-guide/

 

The OneSky is a 5" Newtonian reflector.  You can see a LOT with that scope.   And the number of good targets goes up as your sky and ground conditions get darker.

 

Light Pollution
https://telescopicwa...ight-pollution/


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#15 hiMike

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Posted 16 October 2019 - 05:15 PM

Hello. I am going to tag on to this post because it is asking the same question I have. I have a AWB OneSky Reflector Telescope (https://shop.astrono...ector-telescope) with the 10mm and 25mm eye pieces for about a month now. I have been able to see both Saturn and Jupiter which made me super excited, but I would like to see more if my scope allows for it. I am slowly scanning my way through jlandy's massive thread looking for nuggets about eyepieces, but there is a lot of stuff in there and I have probably missed nine useful tips for every one I have found so far. Would something like a Vixen Optics 2x Barlow Lens (1.25") with Built-In T-Mount Adapter (https://shop.astronomerswithoutborders.org/collections/frontpage/products/vixen-optics-2x-barlow-lens-1-25-with-built-in-t-mount-adapter) be recommended for this scope or should I go in a different direction? I do not have deep pockets, but I would prefer to buy quality at a reasonable price over a cheap alternative that may or may not get the job done.

 

Thank you for your time.

 

v/r

Alan

A barlow is a great investment and one you can use with any other scope you ever purchase.

For the OneSky, you need to be careful which one you get. Some will require you to slightly collapse the telescope or you'll never be able to focus. Its a huge pain to adjust and absolutely not worth the hassle. That's what happened with the cheap one I bought... I returned it the next day.

 

I recommend this one by Orion Celestron*. Its double the price of the cheapo ones, but the optical quality is great and you don't have to retract the secondary mirror

 https://www.amazon.c...71263846&sr=8-6


Edited by hiMike, Yesterday, 12:05 PM.

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#16 SteveG

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Posted 16 October 2019 - 08:01 PM

A barlow is a great investment and one you can use with any other scope you ever purchase.

For the OneSky, you need to be careful which one you get. Some will require you to slightly collapse the telescope or you'll never be able to focus. Its a huge pain to adjust and absolutely not worth the hassle. That's what happened with the cheap one I bought... I returned it the next day.

 

I recommend this one by Orion. Its double the price of the cheapo ones, but the optical quality is great and you don't have to retract the secondary mirror

 https://www.amazon.c...71263846&sr=8-6

We need to put a list together of barlows that don't work with the OneSky. I use a Celestron Ultima with mine and it's outstanding. Good to know this Orion one works as well.



#17 SteveG

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Posted 16 October 2019 - 08:57 PM

 

With that in mind,  and I have the AWB, it works best for planetary (high power) with a 5 mm eyepiece.

You could get that by using a 2x barlow and a 10mm eyepiece or buying a native 5mm eyepiece.

Do you know how to collimate your AWB?  The higher the power the more necessary collimation 

is.  The collapsible design means you need to collimate each time if used for high power.

 

 

Interestingly mine has held collimation extremely well. I did it exactly once, then traveled with the tube in a trunk unprotected, checked it in a duffle bag as baggage on 2 flights to Hawaii, and the thing has been and remains in perfect collimation 2 years later.


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#18 BFaucett

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Posted 16 October 2019 - 09:04 PM

 

I recommend this one by Orion. Its double the price of the cheapo ones, but the optical quality is great and you don't have to retract the secondary mirror

 https://www.amazon.c...71263846&sr=8-6

 

Just a heads up: That link points to a Celestron Barlow.  

 

Cheers!  Bob F.



#19 hiMike

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Posted Yesterday, 12:06 PM

Just a heads up: That link points to a Celestron Barlow.  

 

Cheers!  Bob F.

Oops, good catch. The link is the correct one, I updated my post.


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#20 hiMike

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Posted Yesterday, 12:13 PM

Interestingly mine has held collimation extremely well. I did it exactly once, then traveled with the tube in a trunk unprotected, checked it in a duffle bag as baggage on 2 flights to Hawaii, and the thing has been and remains in perfect collimation 2 years later.

Mine only requires collimation when I set up in front of a crowd of anxious observers 


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#21 splitskull

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Posted Yesterday, 06:34 PM

We need to put a list together of barlows that don't work with the OneSky. I use a Celestron Ultima with mine and it's outstanding. Good to know this Orion one works as well.

I was looking for a list like this for OneSky. Or a list with barlows that you guys know work good with it.




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