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Dobsonian Telescopes

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#26 Illinois

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Posted 04 August 2014 - 06:32 AM

Go for 10 inch! I can tell big different from my old 6 inch and 10 inch dobsonian for deep sky object and planets. I sold my 10 inch and got 16 inch dobsonian.


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#27 jethro

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Posted 04 August 2014 - 06:57 AM

As for the collimation tools, I find my plastic cap works for me. Yes, I always do a star test. So far, my views are great- including double stars and planets.

Maybe I received a really good scope. I cannot attest to everyone else's equipment. If I had a problem with my collimation, I'd consider another tool, though I will not buy one until I find there's actually a problem. 


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#28 bvillebob

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Posted 04 August 2014 - 11:41 AM

 

How sure are you that your collimation is within tolerance? For deep sky, precise collimation is not necessary but for double stars and planetary viewing, it's got to be within a fraction of a millimeter. 

 

In law school we used to say the big question we learned to ask was "Or else what?"  Statements like these concern me as newbies read them and decide they don't want to buy a reflector if they're that difficult to use.

 

I doubt that 100 telescopes in the U.S. are collimated to within a fraction of a millimeter and yet somehow people manage to get great views out of them.

 

Saying they need to be collimated to that tolerance may drive sales of expensive collimation tools, but for for an average guy with a GSO mirror and secondary and a focal length greater than f/4, I just don't believe that kind of collimation is needed to get 99 percent of the performance out of their optics.  I know I saw spectacular detail on the surface of Mars a few months ago using a Cheshire to collimate my scope.

 

Could you quantify the effects of a millimeter of miscollimation?


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#29 Jon Isaacs

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Posted 04 August 2014 - 01:01 PM

 

 

How sure are you that your collimation is within tolerance? For deep sky, precise collimation is not necessary but for double stars and planetary viewing, it's got to be within a fraction of a millimeter. 

 

In law school we used to say the big question we learned to ask was "Or else what?"  Statements like these concern me as newbies read them and decide they don't want to buy a reflector if they're that difficult to use.

 

I doubt that 100 telescopes in the U.S. are collimated to within a fraction of a millimeter and yet somehow people manage to get great views out of them.

 

Saying they need to be collimated to that tolerance may drive sales of expensive collimation tools, but for for an average guy with a GSO mirror and secondary and a focal length greater than f/4, I just don't believe that kind of collimation is needed to get 99 percent of the performance out of their optics.  I know I saw spectacular detail on the surface of Mars a few months ago using a Cheshire to collimate my scope.

 

Could you quantify the effects of a millimeter of miscollimation?

 

 

 

At F/5, the radius of the diffraction limited circle is about 1.4mm.  To get the good planetary views, to split tight double stars, you want to the tilt of the primarily mirror to be adjusted so that the collimation is within a relatively small fraction of that.  But expensive and/or fancy tools are not necessary precise collimation, A Cheshire, a decent collimation cap, used properly are plenty good enough.  I suspect that there are many, many scopes that are collimated to within a fraction of a millimeter. 

 

In this forum, I think it is important to be honest.  Precise collimation is important and a scope that is not collimated will not perform it's best...  Precise collimation is not difficult, but it does take some effort and understanding.

 

Jon


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#30 PondJumper

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Posted 04 August 2014 - 04:05 PM

Ok, so if I go with the Apertura 10" is the tweakers dream package necessary? So far the only thing in that package that seems like it could be necessary are the stainless steel springs. Can I just get the springs? Otherwise I'd just assume get the Meade. But the meade is on the edge of my price range. That being said Orion is selling a very attractive package, an 8" with a barlow, starchart, and two books for $400 even plus free shipping.



#31 PondJumper

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Posted 04 August 2014 - 04:48 PM

The more I look at and read reviews the more I like the Apertura 10" and I found that I can just get the springs for primary and the thumb screws for secondary mirror. Their site says free shipping to lower 48, does that apply to everything? Think I'm gonna place an order tomorrow. Currently its between the Apertura 10" and the Orion skyquest 8". The Apertura is gaining ground quickly. Orions focuser is single speed, Apertura's is dual, etc...



#32 Kevdog

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Posted 04 August 2014 - 06:12 PM

Over the last 2 years from everything posted, unless you are getting the 'Intelliscope' version of the Orion, it's better to go with the Apertura.   Orion's "plus" version has narrowed the gap some but the Apertura is still preferred.



#33 PondJumper

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Posted 05 August 2014 - 09:05 AM

So I think I've settled on the Apertura AD10, unless someone can persuade me otherwise. I'd like to thank everyone for their advice. Everyone was very helpful in aiding my decision. Will post after first viewing.


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#34 PondJumper

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Posted 05 August 2014 - 09:21 AM

ok whats this flocking business? Why isn't that standard? Is it necessary? What is it? Exactly how much light does it absorb? I was only going to buy the collimation springs and screws. But the only option for this flocking stuff seems to be if you get the whole tweakers package...



#35 Jon Isaacs

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Posted 05 August 2014 - 09:25 AM

ok whats this flocking business? Why isn't that standard? Is it necessary? What is it? Exactly how much light does it absorb? I was only going to buy the collimation springs and screws. But the only option for this flocking stuff seems to be if you get the whole tweakers package...

 

Some people swear by Flocking but it's been my experience that a small amount of properly placed flocking material is all that it is needed.  The worst case is direct light (the moon) entering the draw tube of the focuser..  I have owned my 10 inch GSO scope for more than 10 years. the springs are a nice addition but these are things you can do yourself and save some real money. 

 

Jon



#36 Billytk

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Posted 05 August 2014 - 10:19 AM

If you want to get just the springs, Opticsmart sells them separately. 



#37 PondJumper

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Posted 05 August 2014 - 02:36 PM

Ok, its been ordered. I just went ahead and purchased the Apertura AD10 with tweakers package and Apertura's 2X barlow. It was more than I was wanting to spend. However after reading so many good things about the scope and realizing just how much it came with the for price, it was a no brainer. A wee bit stressed about spending that much but I'm excited. I've never looked through a telescope near 10" of aperture. I even had a good time over the weekend with my little refractor so I have a feeling I'll be overwhelmed. Thanks again guys! You were all a great help.


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#38 SteveG

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Posted 05 August 2014 - 03:51 PM

Good choice!  I've owned all the scopes in question, and would recommend either the Lightbridge or any of the GSO branded 10" dob's. Yes, you need to replace the springs. Heavier ones can be purchased at True Value hardware. As for the secondary mirror screws, you can buy the same glue-on knobs and Allen screws from the hardware store. 

 

If you want the stick-on black felt, then you could order that along with the springs and secondary knobs from Scopestuff. You won't need the primary knobs, the GSO scopes already have them.

 

Good luck and let us know how it goes!



#39 kfiscus

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Posted 05 August 2014 - 04:20 PM

I was going to try to persuade you to go the AD10 way and you beat me to it.  The adjustable alt bearings are good.  The service is good.  The scope is very good.  The Tweaker's Package worth it.  Peace of mind that you made a good purchase?  Priceless.



#40 xavierq

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Posted 06 August 2014 - 10:39 PM

 

If you go with the 8" you can safely use cheaper eyepieces. The 10" will require more expensive/better corrected eyepieces.



Over the years, I have owned a number of Dobsonians, currently own five.. It is true that at F/5, many eyepieces will show somewhat more off-axis astigmatism that at F/6 but in my mind, that does not mean that the faster F/5 scopes "require" fancier, more expensive, better corrected eyepieces. It just means the there's a little more off-axis astigmatism, stars near the edge are not a round and clean. I have some rather nice eyepieces that I typically use, TeleVue Naglers and a Paracorr to correct the coma, but some nights I will use a set of simpler, more affordable eyepieces, for the higher magnifications I use the TMB Planetary eyepieces and they do a very reasonable job, not as wide a field of view nor quite as perfect as the Naglers but there is little I see in the more expensive eyepieces that is not visible in the TMBs.

Regarding the difference between the 8 inch and the 10 inch... For me, not a spring chicken by any means, 66 years old, social security and all that.. The 10 inch is heavier and somewhat more bulky but the 8 and 10 inch OTAs are about the same length and the bases are about the same size. That means when it comes to putting one in a car or setting it up in the backyard, there isn't much difference.

At the eyepiece, the difference is quite apparent. It's not like the difference between 3 inch and a 6 inch but the added aperture is definitely worth while. I have my 10 inch GSO Dob for more than 10 years. During that time, several 8 inch F/6 Dobs have come and gone. I could just never find a reason to choose the 8 inch when the 10 inch was there just waiting.

The photo below shows three scopes, an Orion XT-8 (F/6) on the left, a 12.5 inch F/4.06 Discovery in the middle and a 10 inch F/5 GSO (Zhumell/Apertura etc) on the right.

Jon

1514635-3bears2.jpg

 

 

 

nice collection bro



#41 xavierq

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Posted 06 August 2014 - 10:44 PM

 

If you go with the 8" you can safely use cheaper eyepieces. The 10" will require more expensive/better corrected eyepieces.



Over the years, I have owned a number of Dobsonians, currently own five.. It is true that at F/5, many eyepieces will show somewhat more off-axis astigmatism that at F/6 but in my mind, that does not mean that the faster F/5 scopes "require" fancier, more expensive, better corrected eyepieces. It just means the there's a little more off-axis astigmatism, stars near the edge are not a round and clean. I have some rather nice eyepieces that I typically use, TeleVue Naglers and a Paracorr to correct the coma, but some nights I will use a set of simpler, more affordable eyepieces, for the higher magnifications I use the TMB Planetary eyepieces and they do a very reasonable job, not as wide a field of view nor quite as perfect as the Naglers but there is little I see in the more expensive eyepieces that is not visible in the TMBs.

Regarding the difference between the 8 inch and the 10 inch... For me, not a spring chicken by any means, 66 years old, social security and all that.. The 10 inch is heavier and somewhat more bulky but the 8 and 10 inch OTAs are about the same length and the bases are about the same size. That means when it comes to putting one in a car or setting it up in the backyard, there isn't much difference.

At the eyepiece, the difference is quite apparent. It's not like the difference between 3 inch and a 6 inch but the added aperture is definitely worth while. I have my 10 inch GSO Dob for more than 10 years. During that time, several 8 inch F/6 Dobs have come and gone. I could just never find a reason to choose the 8 inch when the 10 inch was there just waiting.

The photo below shows three scopes, an Orion XT-8 (F/6) on the left, a 12.5 inch F/4.06 Discovery in the middle and a 10 inch F/5 GSO (Zhumell/Apertura etc) on the right.

Jon

1514635-3bears2.jpg

 

 

 

nice collection bro



#42 xavierq

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Posted 06 August 2014 - 10:45 PM

 

If you go with the 8" you can safely use cheaper eyepieces. The 10" will require more expensive/better corrected eyepieces.



Over the years, I have owned a number of Dobsonians, currently own five.. It is true that at F/5, many eyepieces will show somewhat more off-axis astigmatism that at F/6 but in my mind, that does not mean that the faster F/5 scopes "require" fancier, more expensive, better corrected eyepieces. It just means the there's a little more off-axis astigmatism, stars near the edge are not a round and clean. I have some rather nice eyepieces that I typically use, TeleVue Naglers and a Paracorr to correct the coma, but some nights I will use a set of simpler, more affordable eyepieces, for the higher magnifications I use the TMB Planetary eyepieces and they do a very reasonable job, not as wide a field of view nor quite as perfect as the Naglers but there is little I see in the more expensive eyepieces that is not visible in the TMBs.

Regarding the difference between the 8 inch and the 10 inch... For me, not a spring chicken by any means, 66 years old, social security and all that.. The 10 inch is heavier and somewhat more bulky but the 8 and 10 inch OTAs are about the same length and the bases are about the same size. That means when it comes to putting one in a car or setting it up in the backyard, there isn't much difference.

At the eyepiece, the difference is quite apparent. It's not like the difference between 3 inch and a 6 inch but the added aperture is definitely worth while. I have my 10 inch GSO Dob for more than 10 years. During that time, several 8 inch F/6 Dobs have come and gone. I could just never find a reason to choose the 8 inch when the 10 inch was there just waiting.

The photo below shows three scopes, an Orion XT-8 (F/6) on the left, a 12.5 inch F/4.06 Discovery in the middle and a 10 inch F/5 GSO (Zhumell/Apertura etc) on the right.

Jon

1514635-3bears2.jpg

 

 

 

nice collection bro



#43 kfiscus

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Posted 06 August 2014 - 11:05 PM

Those are just his little scopes...



#44 James1996

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Posted 07 August 2014 - 03:41 AM

.........That's little then what the heck do his big scope's look like!



#45 Jon Isaacs

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Posted 07 August 2014 - 05:48 AM

.........That's little then what the heck do his big scope's look like!

 

Check out my avatar...

 

Jon



#46 jrbarnett

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Posted 08 August 2014 - 04:02 PM

Zhumell's are great, as are Aperturas.  They are both GSOs.  GSO is the Taiwanese optics maker who makes these scopes, and the Lightbridges for Meade.

 

I prefer Orions to the GSOs, but not by much, and the GSO made scopes are cheaper (but lack Intelliscope DSCs which are a good deal).

 

The light grasp difference between a 10" and an 8" isn't huge, but can be detected comparing them on the same targets side by side.  The 8" scope, though, is far and away the better beginner's scope.  It is cheaper.  It is slower, and less sensitive to poor collimation as a result.  It will produce better results with cheaper simpler eyepieces.  It will be a little lighter for transport too.

 

My recommendations in detail, here:

 

http://www.cloudynig...e/#entry3746585

 

- Jim 



#47 Whiskcat

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Posted 15 August 2014 - 03:29 PM

Good choice on the Apetura 10, I've been eyeballing that dob for awhile. Let us know how you like it!



#48 stryder

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Posted 27 August 2014 - 08:48 AM

I LOVED, LOVED, LOVED my AD10. It was my first real scope. I highly suggest getting a Telrad. I was skeptical at first, but after putting one on, it was like cheating. I was consdiering buying Opticsmart's setting circles and a digital angle finder, but in the end the AD10 was too big for my small car/house. I ended up selling it and getting an 8" Celestron Nexstar. 

 

Those first lights from that AD10 though were awesome. It was great when I took it to my club's dark sky site. Blown away by the views. You're going to love it!

 

Now, as long as we can get those stupid clouds to go away.



#49 cosmicmeow

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Posted 01 September 2014 - 01:06 AM

I'm going to do my best to answer all of your questions.

 

As for an 8" or 10", there really isn't much of a difference between the two. Yes, the 10" will have a tad bit more light gathering capability, but the difference between the two when observing will be miniscule. 

 

Should you go with an 8", I'd strongly recommend the Apertura 8" Dobsonian. It is a bit more expensive than the XT8, but keep in mind it has a better focuser, and comes with a collimator, finder scope, fan for the mirror, and a few other nice little things that just make it a better deal than the XT8, as well as a better telescope all around.

 

The LightBridge has been on the market for years. Not much to say about it other than yes, it is a nice scope and I believe you would be pleased with it as well. A guy in the local astronomy has had a 10" LB for years and he has had nothing but good to say of it.

 

Set up is typical fairly simple, as long as you follow the manual you should have it together in an hour or two at the most.

 

I've personally never had a scope get bruised up in shipping, but keep in mind that it is rare from what I have seen. Companies usually do a pretty good job at making sure that their telescopes are packaged well. 

 

The most important thing is that you enjoy yourself and have a great time. Whether you go with the XT8, the LightBridge, or even the Apertura that I mentioned, all are quality scopes that will bring you years of enjoyment.

 

Have fun, good luck, and clear skies!!!








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