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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Orion XT8 questions...and more...
      #5559200 - 12/07/12 12:16 PM

So I started a thread a page back about getting a telescope for my 6 year old niece and decided against it at this time. However, all of this talk about getting a scope for her has reopened the case for getting a scope for myself. Maybe it will be a birthday present for myself in April...or sooner (holiday bonus?). I did research years ago, but wound up spending my $$ on a Canon DSLR at the time.

I have been an avid stargazer since I was about 9 (so around 25 years now) and I can name the constellations and most of the bright stars (and even point out at least 1 DSO [Andromeda]). I don't need a small, beginner scope to learn the sky.

I have read all of the "dobs give the best bang for the buck for your first scope" comments everyone else posts. I am focusing on an Orion XT8. One of my other hobbies is photography, but I am trying not to catch the AP bug. The XT8 can at least get semi-detailed moon and blurry planet photos, right? I don't think I need the XT8i since I have phone apps that show where objects are. I would love the XT8g for tracking, but it's just not in the budget.

Question 1: Orion XT8, is it easy to transport? I live in an apartment and would need move the telescope to a different location to use it.

Question 2: Could someone run down eyepiece/lenses in layman's terms. I am versed in cameras/photography so is it the same where the higher the mm the more "zoom" you get? Are there "must have" and "don't ever buy" eyepieces. And what is a Barlow? I wear glasses, does that affect eyepiece selection at all?

Question 3: How high up is the eyepiece on average when viewing. I'm 5'10", would I need to be sitting or bending over to view? I have a camping chair, but I don't know if it will be tall enough to use.

Question 4: Any thoughts on Orion's "Build a scope" to customize accessories VS getting the scope and accessories/upgrades separate? What about the Beginner Barlow Kit or the LE Bundles?

Question 5: Everyone talks about how easy a dob is to push around to find something. Can you tighten/loosen the mechanics? I think I am more worried about finding something and then accidentally moving the scope and losing it than not being able to move it at all.

Question 6: What will I actually see when looking at, say, a nebula? I know it won't look like Hubble images, but will it just look like a cloud, or will it be interesting. Anyone have photos that more closely represent visual experience.

Oh boy...this was supposed to be a quick post, but I kept thinking of more things to ask. More questions likely to come...


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Tank
Carpal Tunnel
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Reged: 07/27/09

Loc: Stoney Creek, Ontario, CANADA
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5559249 - 12/07/12 12:52 PM

1. 8" is pretty portable
2. 1200mm is you FL of the scope divide this by the EP FL give you the magnification.
1200/6mm EP gives you 200x magnification
3. its about only 4'-6" at zenith pointed straight up! You will be viewing mostly at about 3'-6" off the ground
4. Lots to choose from as far as accessories the ES 82 N2 eyepieces right now are the best value EPs out there!
5. Most DOBs have tension controls. If you view enough with the DOB you will get the hang of it quickly
6. Forget the Hubble images!!!! For instance M42 without a filter will look like this without a filter and a bit better with also will look more life like!:
http://www.flickr.com/photos/emiliokuffer/8028102484/


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JoLo
sage


Reged: 02/09/10

Loc: Highland, IL
Re: Orion XT8 questions...and more... new [Re: Tank]
      #5559272 - 12/07/12 01:07 PM

The 8" scope is a great one to start out on, and not difficult to move around. I would describe it more as awkward than anything; i started out with a 10" solid tube Dob, which is about the limits of what I would want to drag around...I subsequently bought a 12" truss tube, which although heavier, is easier to tote in pieces. An 8" solid tube will not pose a problem.

Yep, I got some very nice moon / planet shots with a Dob and a Canon 450D...they are bright enough that you can take fast exposures and not get too much blurring. An afocal or eyepiece projection setup is a great way to get your feet wet with AP.

Quality eyepieces make a difference, save some of your budget to get good ones, a spread of focal lengths to get you wide views and moon/planet closeups.

A few items i would consider...adjustable astro chair is the best, back saving investment I have made. A quality star chart and a Telrad / Rigel Quickfinder. The combination of an optical finder and a Telrad or QF is hard to beat with star hopping. A good chart combined with finder/Telrad will make you an expert star hopper in no time. Learning the sky and how to star hop is a great skill that will serve you well.


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frito
Pooh-Bah


Reged: 10/05/12

Loc: Fremont, CA
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5559295 - 12/07/12 01:24 PM

so many questions so i'm going to answer what i can one a time

Question 1 : depends. if you live on the ground floor of the apartment or it has elevators transporting it as a single unit or split from the base will not be a problem. if you have to lug it up and down lots of stairs then i would think twice unless you get a carry bag or make handles/straps for the OTA. the base has a handle on it.

Question 2 : the shorter the focal length the greater the power/magnification. a barlow is basically a power doubler/tripler that can be put between any eyepiece and the telescope in the focuser to effectively double or triple their power depending on the barlow. there really isnt a eyepieces to avoid list per se. all but the cheapest ones you can find will produce good images and serve various purposes, as you wear eyeglasses if you want use wear them when you view you are going to want to make sure you get eyepieces that will have a longer eye releif. many cheaper esp high magnification eyepieces like plossl's will have a very short eye relief. even some higher end eyepieces can have very short eye relief. i have an older 16mm Televue Nagler type 2 that has very short eye relief. anyways this subject can be studied and discussed for ages. go check the eyepiece section on here sometime

Question 3: the scope to eyepiece is about 4-1/2 feet off the ground if pointed straight up. if pointed horizontally its about 3 feet off the ground approximately. folding camping chairs are terrible. i tried to use one when i first started. you will want a decent height adjustable observing chair. there are some that work well starting at around 100 dollars.

Question 4: build a scope is not necessarily a good deal. buying a used XT8 is the best deal. i got mine locally for 200 dollars!

Question 5: if anything the stock bearing are not smooth enough. I recently upgraded the surfaces the teflon rides on on my XT8 with FRP (fiber reinforced plastic) i had to make a counter weight to strap to the back of the scope to rebalance it but following objects and wait times for the scope to settle are greatly reduced. down side is yes if i bump the scope it will move. solution don't bump it!

Question 6: what you will see will depend on many factors. what type of object it is, your viewing conditions both as far as seeing and transparency goes as well as and more importantly how much light pollution you have at your viewing site. stars will be points with 4 spikes from the diffraction from the spider that holds the secondary. nebula will very from just a slight hazy spot to a detailed gas cloud but only the orion nebula shows a ton of detail from just about anywhere. galaxy's are going to often be super faint fuzzy's except for andromeda. its a larger faint fuzzy in light polluted skies. Globulars will look like faint fuzzys often. in good conditions without too much light pollution at higher mag you will be able to star resolving stars in the brighter globs. open clusters will look amazing in low light pollution areas and good even in high LP.


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Tony Flanders
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5559427 - 12/07/12 02:43 PM

Quote:

So I started a thread a page back about getting a telescope for my 6 year old niece and decided against it at this time. However, all of this talk about getting a scope for her has reopened the case for getting a scope for myself.




Sounds familiar. That's exactly how I ended up with my first scope, except it was a nephew, not a niece.


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: Tony Flanders]
      #5559438 - 12/07/12 02:50 PM

Thank you all for your responses.

@JoLo: Do you have example images you care to share? I see you have a 12”, so your exposures would probably be faster than with an 8”. I’ll definitely need to look into a chair. I already have a bad back.

@frito: I am on the first floor and my back door is close to the parking lot, so as long as it is easy to carry looks like that won’t be much of a problem. Ah so it's the opposite of camera lenses with the smaller number being more magnification.

So with the supplied 25mm eyepiece and an additional 2x Barlow would give me 96x, so I would probably need a barlow and at least a shorter focal length EP.

I just did a price comparison of the stock classic XT8 and a build-a-scope (adding the items that come with the stock classic XT8) and it came to $428.36 compared to $359.99, a $68.37 difference…that seems wrong…best go with the stock and spend the $68.37 on an extra eyepiece.

I guess since I am pretty sure I am going with the XT8, I really need to start focusing on eyepieces. I really don’t know where to start with that. They look like they can get really expensive. I see Orion sells long relief eyepieces for $99.99 each…


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Pharquart
sage
*****

Reged: 11/11/09

Loc: Southwest Minneapolis Metro
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5559503 - 12/07/12 03:36 PM

Eyepieces indeed can get very expensive. I think almost everyone agrees that Televues are the acme of the eyepiece options, and their top ones are $500. The F/6 ratio of the 8" scope is in the range that is more forgiving of eyepieces, so you generally won't have to spend as much as someone using a F/5 or F/4.5 scope like the bigger reflectors. At the lower ratio, stars at the edge of field can be blurry or streaked.

You'll want to start your search for eyepieces based on focal length to achieve a desired magnification. Don't fall into the trap of thinking you need super high magnification. 200x might be the highest usable magnification you'll get out of most nights because of atmospheric conditions (seeing). Many objects actually look better at lower magnifications than higher. In basic eyepieces, shorter focal length (higher magnifications) means less eye relief. You can probably take your glasses off and use the telescope focuser instead, meaning you can use low eye relief eyepieces, but if you have to keep taking off/putting back on your glasses, you'll tire of that quickly. So probably better to pick eyepieces with long enough eye relief, maybe 15mm or more. Any eyepiece that's about 15mm focal length or longer should already give you that. It's the shorter focal length models that make you get close. A Barlow allows an eyepiece with a long eye relief to keep it, even though the magnification doubles. In fact, most advanced eyepieces that are short focal length and long eye relief have a built-in Barlow-like lens at the front end.

Next comes field of view, or how wide a patch of sky you can see. A basic inexpensive Plossl gets you about 50 degrees. (That's what your eye thinks it sees in the eyepiece. The actual field of view in the sky is 50 divided by the magnification.) Wide angle eyepieces go to 60, 68, 82, 100, or more. The Explore Scientific line of 82 degree eyepieces seem to be very good and very reasonable, particularly compared to similar Televue, but they're still $100 or more. Wide field + long focal length usually means you need a 2" eyepiece barrel, which the XT8 may or may not have, depending on which configuration you buy.

The nice thing is that eyepieces, if cared for well, retain a good chunk of their value. Browse the classifieds on this site and buy a used one, maybe something in the 15mm range. Probably stay away from 12-13mm, as you can get that effective length by using the 25mm with a 2x Barlow. Use the scope and decide if you want more or less magnificaiton, more or less eye relief, and more or less field or view. Sell whatever eyepiece doesn't fit your needs. If you bought it used and didn't scratch it, drop it, or smudge up the glass, there's a good chance you'll get most of your price back, less shipping. Buy one that's better. I've "traded up" my eyepiece collection over the years with remarkably low loss in value along the way.

In the end, get used to the idea that this initial purchase of a scope and eyepiece (and any other accessories) is just an initial purchase. Dobs in general are very easy to modify and customize over time. Eyepieces are interchangeable and your collection will likely improve in size and quality over time. Don't fret too much about picking the best accessories to start. Just pick something and get started, then change stuff out as you learn more about what and where you like to observe.

Brian


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: Pharquart]
      #5559555 - 12/07/12 04:20 PM

The XT8 does have a 2" Crayford focuser that accepts 1.25" and 2" telescope eyepieces.

It also comes with a 25mm Orion Sirius Plossl eyepiece (48x magnification/96x with 2x Barlow). Your recommended 15mm would give me 80x magnification (160x with 2x Barlow). I guess that sounds like a good start?

As far as the Barlow goes, is the Orion Shorty 1.25" 2x Barlow Lens decent? Would a 3x be better to start with, or should that be a future purchase.

Is there loss of image quality through a Barlow? For example would you get a better view through a 15mm eyepiece vs. a 30mm with a 2x Barlow?

I guess I will start lurking in the Eyepieces section...so far I have been spending all of my time here.


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csrlice12
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Reged: 05/22/12

Loc: Denver, CO
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5559710 - 12/07/12 06:05 PM

"Is there loss of image quality through a Barlow? For example would you get a better view through a 15mm eyepiece vs. a 30mm with a 2x Barlow?)

Oh, the can of worms you just opened......

I prefer to use separate focal length eyepieces. But will use a barlow on those nights of exceptional viewing....doesn't happen often. But, everyone who has a dob/newt should have a barlow. A barlow is essential if you use the barlowed laser technique to collimate your scope.

Edited by csrlice12 (12/07/12 06:09 PM)


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Tim D
super member


Reged: 10/08/10

Loc: Temecula, CA
Re: Orion XT8 questions...and more... new [Re: csrlice12]
      #5559996 - 12/07/12 09:32 PM

A zoom might also work well for you- I get great results with mine and my XT8
Tim


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kfiscus
Carpal Tunnel
*****

Reged: 07/09/12

Loc: Albert Lea, MN, USA
Re: Orion XT8 questions...and more... new [Re: Tim D]
      #5560105 - 12/07/12 10:49 PM

The eyepieces (EPs) you get with the XT8 are good and will give you low- and medium-power views, the views you'll use and enjoy more often. If you get a barlow, 2x is the most common magnification, you've just doubled your EPs' magnifications and you've effectively doubled your EP collection. The following is what happened to me...
I started out with decent stock EPs, years later upgraded to new wide-field $200 EPs, and now have upgraded to buying used but good-as-new Televue Type 6s for $250 each from reputable sellers here and Amart.

Edited by kfiscus (12/07/12 10:50 PM)


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JasonBurry
sage


Reged: 04/27/12

Loc: Cape Spencer, NB, Canada
Re: Orion XT8 questions...and more... new [Re: kfiscus]
      #5560124 - 12/07/12 11:02 PM

I observe with a telescope not terribly different from the XT8. I've found that I do the great bulk of my observing with 2 eyepieces and a 2x barlow. My mix is a 32mm plossl, and a 12.5mm plossl. Works for me.

With that, I get about 38x, 76x (32mm with and without barlow), 100x an 200x (12.5 with and without barlow). It's a rare day on which my 6mm sees use (400x with barlow), maybe a handful of times in the last 10 years.

The 3 main pieces, 32, 12.5 and 2x barlow can be had for maybe 150 easily enough, and maybe significantly less.

They've provided good value and some beautiful views. The 32mm shows some coma at the edge of field, but it's unobjectionable to me. I get 1.3 degree fov which ain't bad.

A decent chair will be nice too, but a rectangular box style seat can give a handful of height options on the cheap. You'll see more if your seat height is comfortable.

You're gonna have some fun!

J


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CosmoSat
Pooh-Bah


Reged: 07/24/09

Loc: India
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5560234 - 12/08/12 12:30 AM

Its kinda surprising the nobody pointed u to the Apertura AD8 dob...it has great value for money with excellent quality too..I would recomment u this one over the orionxt8. only if u want to hve the intelli feature..then go for the xti.

Clear Skies!


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Saneless
member


Reged: 12/03/12

Re: Orion XT8 questions...and more... new [Re: CosmoSat]
      #5560243 - 12/08/12 12:39 AM

Quote:

Its kinda surprising the nobody pointed u to the Apertura AD8 dob...it has great value for money with excellent quality too..I would recomment u this one over the orionxt8. only if u want to hve the intelli feature..then go for the xti.




The AD8 is definitely a much better buy. Most of the time.

Only real issue is its weight compared to the XT8. It has much better bearings (mount and tube) but this also adds about 12-14lbs of weight. The XT8 is about 40 vs almost 53 or so for the AD8. And of course the XT6 is only 34.

I guess it really depends how far you have to go. If it's not that far, the bearings, better finder, better focuser, fan, and the fact you get a 2" 68 degree 30mm and a 9mm plossl make it worthwhile.

The XT kinda rips you off really with its 25mm. They should have at least made the single eyepiece a 32.


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FlorinAndrei
scholastic sledgehammer


Reged: 09/28/10

Loc: California
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5560362 - 12/08/12 02:45 AM

Either the Apertura AD8 or the Zhumell Z8 would be a somewhat better deal than the XT8. Two eyepieces instead of one, magnifying finder instead of 1x finder, OTA with adjustable balance instead of fixed OTA, dual speed focuser instead of single speed, primary mirror fan instead of no fan, etc.

The optics are similar, however. So if you get the XT8 as a Christmas present, keep it, don't throw it away, it's not a bad scope.

Quote:

is it easy to transport?




Any 8" dob can be easily carried in a sedan. Chances are it will fit on the back seat, unless your car is pretty small.

For carrying it down the stairs and so on, they split in two: base and OTA. You can carry the two parts separately, they are a little bit voluminous, but aren't too heavy at all.

Be VERY careful with the door frames, they hate focusers for some reason and are looking for every opportunity to ruin your scope.

Quote:

Could someone run down eyepiece/lenses in layman's terms. I am versed in cameras/photography so is it the same where the higher the mm the more "zoom" you get? Are there "must have" and "don't ever buy" eyepieces. And what is a Barlow? I wear glasses, does that affect eyepiece selection at all?




F = focal length of telescope

f = focal length of eyepiece

M = magnification

Then:

M = F / f

For the XT8, AD8 and Z8, F = 1200mm.

The shorter the eyepiece focal length, the greater the magnification.

For a scope like this, the useful range of eyepiece focal lengths is 3mm ... 36mm, although the extremes will be used very rarely (6mm and above will be used more often, and you may never need an eyepiece longer than 30mm if you get a wide angle 30mm like the 30mm Explore Scientific 82 degree).

You "must have" 3 or 4 eyepieces spaced uniformly within the range of focal lengths indicated above.

"Don't ever buy" many cheap eyepieces. Rather get a few better quality ones.

A barlow is a multiplier for magnification. A 10mm eyepiece plus a 2x barlow is the same like a 5mm eyepiece alone.

If your glasses are spherical, you can just remove them and adjust the focus on the scope until you see clearly (but it may look de-focused for other people). Or you could keep the glasses on and adjust focus like everyone else. If you must keep the glasses on, make sure your eyepieces provide plenty of eye relief, 12...15mm ER at minimum, ideally more like 20mm ER.

If you wear glasses for astigmatism, you may find that you must keep the glasses on. Then look for eyepieces with decent ER.

Quote:

How high up is the eyepiece on average when viewing. I'm 5'10", would I need to be sitting or bending over to view? I have a camping chair, but I don't know if it will be tall enough to use.




Excellent question.

The eyepiece on a dobsonian varies in height as the scope moves up and down. Therefore it's best if you have some kind of adjustable height chair. In the beginning, a rectangular box would suffice, it will provide 3 different heights. Or just any fixed chair will do, but you will do some gymnastics while bending over to the eyepiece.

Google "observing chair", it's the most comfortable solution. You could even build one if you have any DIY skills at all.

Quote:

Everyone talks about how easy a dob is to push around to find something. Can you tighten/loosen the mechanics?




Excellent question. Looks like you're doing your homework.

The tension in the altitude bearing should be adjusted for best push-to performance - when the motion is effortless and buttery smooth, it begins moving without jumping, and stops immediately, that's best. It takes some trial and error until you figure it out, after that it should be fine.

With the AD8 and Z8, don't adjust tension to compensate for a very heavy eyepiece; instead, take advantage of the OTA balance mechanism and move the OTA until it's balanced again. With the XT8, you can't do that, you'll have to sacrifice perfect friction to keep it from stooping down.

Quote:

What will I actually see when looking at, say, a nebula? I know it won't look like Hubble images, but will it just look like a cloud, or will it be interesting.




Not like Hubble, indeed.

It will look "just like a cloud", yes, but it will be interesting nevertheless. You're seeing light that has traveled thousands of years to reach you. Are you kidding me? Of course it's interesting!

Only one way to find out.

Buy this book, it will tell you what objects to observe in the beginning:

http://www.amazon.com/Turn-Left-Orion-Hundreds-Telescope/dp/0521153972/

Edited by FlorinAndrei (12/08/12 02:59 AM)


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phillip
professor emeritus


Reged: 11/26/05

Loc: Sterling, Illinois
Re: Orion XT8 questions...and more... new [Re: FlorinAndrei]
      #5560416 - 12/08/12 05:24 AM

My experiences with my XT8. Fun catching some of the brighter Deep Sky, Orion Nebula are hints of a Green Color, companions to the Trapezium cluster let me know if I'm in for a good night.

Planetary viewing is among my favored, more than one moon of Saturn not just Titan pop into view. Division in Ring is more than obvious. Several views of Mars during a close encounter was demanding to catch favorable sky conditions for details. One of those very rare steady sky's here in the Midwest released increadible details. Observation was over a 3 month period and highly rewarding teaching loads of patience viewing. Magnifications varied from just over 100 to over 350 latter those rare steady sky's. Mediocre sky's still release fleeting detail with continual focusing. Skills with higher power are rewarding with practice as shared 400 power group viewing putting the target just off edge of the scope and let it drift for just under a minute for the onlookers, they loved the huge image.

New Celestron only one night with an above average sky caught the Snowball Nebula rather sizeable puffy star stood out well at 60X, sure even better in the XT8.

Andromeda Galaxy is huge, brighter companion nice rather bright compact comet view, other more spread out companion sometimes elusive, but when there larger with averted vision hints of detail, nice indeed!

Sorry so lengthy, wish you the best.

ETX90
5 inch Short Tube
New SE6 Celestron
XT8
Nagler, and prized Clave 8MM Eyepices Planetary Views

Edited by phillip (12/08/12 05:46 AM)


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: phillip]
      #5561525 - 12/08/12 09:21 PM

Ack! Apertura AD8 and Zhumell Z8 VS Orion XT8!!!

@Saneless
Quote:

The AD8 is definitely a much better buy. Most of the time.


What are the exceptions?

Quote:

Only real issue is its weight compared to the XT8. It has much better bearings (mount and tube) but this also adds about 12-14lbs of weight. The XT8 is about 40 vs almost 53 or so for the AD8.



I guess this doesn't matter much. Chances are I will be transporting it in 2 pieces.

OK so running down the specs, the Apertura is only $40 more than the XT8. It replaces the 1.25" 25mm Plossl eyepiece with a 2" 30mm SuperView eyepiece and has a 2 speed focuser. And comes with the additional:
- 1.25" 9mm Plössl eyepiece (high-power) with 52 degree field of view
- 35mm Extension Tube (used to provide extra back-focus for eyepieces that need it)
- 1.25" Moon Filter
- Laser Collimator (1 battery included)
- Battery operated primary mirror cooling fan
- 4-slot eyepiece tray
- 35mm Extension Tube

I added up the cost of buying those items separately and it came to over $250!!! I don't think I can consider the Orion model anymore, unless someone were to tell me that the mirror or eyepiece that came with the Orion were vastly superior (which doesn't seem to be the consensus).

Also, I'm confused about the 35mm Extension Tube. The description says it is used to provide extra back-focus for eyepieces that need it.
What does that mean exactly?

Now, I have seen other people posting that the Apertura and the Zhumell are clones of each other. Are there ANY differences/advantages of one over the other? It looks like they come with the same accessories (not sure if Zhumell has the 35mm Extension Tube as I don't see it listed anywhere).

Also, since they come with a 1.25" and a 2" eyepiece, does that mean that I would need 2 different Barlows and a moon filter for the 1.25?


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FlorinAndrei
scholastic sledgehammer


Reged: 09/28/10

Loc: California
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5561801 - 12/09/12 01:44 AM

Quote:

I don't think I can consider the Orion model anymore, unless someone were to tell me that the mirror or eyepiece that came with the Orion were vastly superior (which doesn't seem to be the consensus).




The consensus is that they are all made in similar factories in China, following similar industrial processes and standards.

Quote:

Now, I have seen other people posting that the Apertura and the Zhumell are clones of each other. Are there ANY differences/advantages of one over the other?




Just get the one that has the best discount for Christmas, or something. These scopes are almost identical.

Quote:

Also, since they come with a 1.25" and a 2" eyepiece, does that mean that I would need 2 different Barlows and a moon filter for the 1.25?




Somewhere on that list of accessories for either scope, there is a 2" / 1.25" adapter for eyepieces. Get any 1.25" eyepiece, plug it into the adapter, and now you could plug it into 2" focusers, 2" barlows, 2" coma correctors, etc.

A 1.25" eyepiece with an adapter is like a 2" eyepiece.

Many adapters are also threaded to allow you to use 2" filters with 1.25" eyepieces. Therefore you could get only the 2" version of any filter and use it with any eyepiece. If the adapter is not threaded, chances are it's one of those flimsy cheap ones which may or may not hold the 1.25" eyepiece exactly on axis, and you should get a better adapter - threaded, solid, well centered. But it's not an emergency, you could use the existing adapter for a while.

Most commonly used (and cheaper) barlows are 1.25". That means you can't use it with a 2" eyepiece. That's okay, since most of the time you would use it with the 9mm eyepiece anyway, when seeing is good, to give it a power boost. There are 2" barlows available for purchase, but they are more expensive, and it's less likely that you'll use it with the 2" eyepiece (but it's definitely doable).

Moon filters are over-rated. A telescope cannot increase the surface brightness of an extended object like the Moon. In fact, the Moon's surface brightness in a scope is lesser than in reality. The greater the magnification, the less surface brightness on the Moon. Keep the magnification rather high (which is how you should look at the Moon anyway), do not observe the Moon from a dark place, and filters will be unnecessary.

When I look at the Moon, I place the scope in front of the house; across the street there's a street light, there's enough light I could read a book. I observe at pretty high magnification (exit pupil is 1mm or less). I share the view with neighbors, passersby, etc. I can't remember when I used the Moon filter last time (in fact, I'm not even sure if I still have it).

Quote:

Laser Collimator (1 battery included)




Collimating with a laser is very intuitive, easy, quick, and precise. Here's a primer:

http://www.cloudynights.com/documents/primer.pdf

But there's a catch: It assumes that the laser itself is very precisely centered. That is indeed the case with high end models, but may or may not be the case with cheap lasers.

Not to worry. Just verify the laser if it's centered or not. If it's not, fix it. It's easy:

http://www.stark-labs.com/craig/llcc/llcc.html

After a while, when you acquire some experience, you could do some star testing, to verify your laser collimation. The star test is the ultimate authority for scope performance, but it's difficult to do and requires good conditions:

http://legault.perso.sfr.fr/collim.html

Quote:

Battery operated primary mirror cooling fan




This is why you need it:

http://www.garyseronik.com/?q=node/55

http://www.garyseronik.com/?q=node/69

Edited by FlorinAndrei (12/09/12 01:48 AM)


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frito
Pooh-Bah


Reged: 10/05/12

Loc: Fremont, CA
Re: Orion XT8 questions...and more... new [Re: FlorinAndrei]
      #5561816 - 12/09/12 02:02 AM

the Z8 and AD8 they are more or less the same scope but have a different name on them they are made by GSO in Tiawan. they offer more bang for your buck currently in just what comes with them than the XT8. now if you can find a used XT8 at the right price like i did (200 dollars!) then by all means get it instead. the XT8 is made by Synta in china, the company that now owns Celestron. Most of Orion's stuff is made by Synta but not everything.

out of the extra features/stuff included in the GSO scopes i would say the eyepiece rack, dual speed focuser and better bearing system are probably the biggest things. the XT8's bearing system can be made to work just as good if not better if your a DIY kind of person with just a 30 dollar sheet of FRP and some time spend cutting a disk for the base to ride on and two strips to wrap around the alt bearings. i did this to mine and love it but it has also required me to make a counter weight i have to attach to the mirror end of my scope so it stays balanced with heavy eyepieces and the 8x50 finder i got on it now.

no matter what you can't go wrong they are all great starter scopes. i already want a bigger scope but i will not get rid of my XT8 simply because of its portability and ease of setup. the easier it is to get out and observe the more likely one is to actually go out and do it often.

Edited by frito (12/09/12 02:04 AM)


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: frito]
      #5562452 - 12/09/12 01:20 PM

Here is an important question...is the $379.98 "sale" price a holiday time price or is that the normal price? http://www.telescopes.com/telescopes/dobsonian-telescopes/zhumellz8deluxedobs...

I wasn't looking to buy right away, but if the price is going to go back up after Christmas, maybe I will have to...


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Dave74
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Reged: 10/23/12

Loc: Gelatinous, MA
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5562475 - 12/09/12 01:38 PM

I think that's about 20 bucks cheaper than the regular price. Not a huge difference.

The price for apetura and Zhumell are pretty much the same.
8" ~$400
10" ~$500
12" ~$700


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kansas skies
sage


Reged: 12/02/12

Loc: Kansas, USA
Re: Orion XT8 questions...and more... new [Re: Dave74]
      #5562712 - 12/09/12 04:11 PM

Just a note on eyeglasses. I wear glasses for presbyopia and astigmatism. Focusing of the telescope is all that is required to correct for the farsightedness, but it does nothing for the astigmatism. What I basically see is the same as what you will see with pinched optics. Fortunately, this is only evident with longer focal length eyepieces having a larger exit pupil. I say fortunately because longer focal length eyepieces generally have plenty of eye relief to allow for wearing glasses. Shorter focal length eyepieces, at least in the standard plossls, tend to have a smaller exit pupil and are not much of a problem, so I am able to use them without wearing my glasses.

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tedbnh
scholastic sledgehammer


Reged: 11/14/07

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Re: Orion XT8 questions...and more... new [Re: kansas skies]
      #5563340 - 12/09/12 11:38 PM

Strap your XT8 (assembled) to a collapsible two-wheel luggage carrier and take it down the elevator in one piece. Your other hand holds your eyepiece case. Everything in one trip, unless you have to go back for your observing chair. (When will somebody design an observing chair that doubles as a collapsible scope cart with wheels...)

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BDS316
Carpal Tunnel


Reged: 09/16/09

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Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5563598 - 12/10/12 06:29 AM

I have an XT8 and I have also used just about every type and focal length of eyepiece in my scope at one time or another.

The 25mm sirius plossl that comes with the scope is a decent quality eyepiece with comfy eye relief and fine for outreach. Use it for a low power/finder eyepiece for now and get a better one after you take care of medium and high power.

When I got better eyepieces, the first priority was to get a medium power eyepiece of premium quality that had a 1.8-2.2mm exit pupil that could also be barlowed for a high power option. I got the TV 11mm Nagler T6 and this eyepiece spends a lot of time in the focuser natively at 109x with a pristine three quarter degree field and barlowed for about 200x. Granted Naglers are expensive but at that time there was no ES option. The 11mm ES N2 82 is VERY nice but not quite as nice as the Nagler. Few could tell the difference most nights.

So I suggest to you a minimalist approach of the 11mm ES and a good 2x Barlow. There is no gap between the low power eyepiece and the 11mm 82 because an 11mm eyepiece with an 82 degree field shows the same amount of sky as an 18mm plossl.

I have used many low power finder eyepieces in the XT8 and have come to the conclusion that if you have really dark skies and are very young, the gold standard is the 35mm Panoptic, and if not, the 27mm Panoptic. These are big bucks of course.

Less expensive alternatives would be compromises in some way, but look for a used Meade 28mm 68 degree which is pretty similar optically to the ES 28mm 68.

Less expensive than that but still nice would be the 2 inch Sterling plossls, the 30 or the 40mm.

You only need one 2-inch eyepiece with a 1200mm focal length scope and its purpose is to show more sky than can be seen with the widest 1.25 inch options which would be a 32mm Plossl or a 30-35mm Ultrascopic. If you want to stay with 1.25 inches these would be the way to go btw.

My 2 incher is a 30mm GSO SV which has its faults, but I can usually borrow something better from a club member because I’m the president of the club.

With regard to the build a scope option, I would say, take a pass on it. It's not really a better deal for you; it's a better deal for Orion. It locks you into buying orion brand EP's and accessories, and identical products are available elsewhere for less money and free shipping, for example Agena, Owl and Scope Stuff.


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rick-SeMI
sage


Reged: 01/08/11

Loc: Michigan - USA
Re: Orion XT8 questions...and more... new [Re: BDS316]
      #5563727 - 12/10/12 08:40 AM

If you have trouble carrying the dob sections you could use a folding hand truck like this.





I would go with the supplied eyepieces and maybe a 2x barlow for now until you try a few others.

You can do that by joining an astronomy club if you have one in the area.

If you go with a non push-to like the XT8 or XT10 and observe in an area with light pollution you
may have difficulty star-hopping. Also, star hopping whether you are in a light dome or not takes some time and practice.

Finally, you have to think about service after the sale and I know for a fact that ORION has the best reputation for that!!


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: rick-SeMI]
      #5563915 - 12/10/12 10:45 AM

@Dave74: That's good to know. As long as it wont go up $100+ after the holidays. I wont rush to get it.

@tedbnh & rick-SeMI: Great idea! While I don't have to worry about an elevator (I live on the ground floor of a 2 story apartment) moving it around would be easier with a hand truck.

I was thinking about the idea of putting locking castors on the mount so it can be rolled around. Has anyone done this?
http://www.homedepot.com/h_d1/N-5yc1v/R-100199256/h_d2/ProductDisplay?catalog...

@BDS316: So, if I go with the Z8 (with the 2" 30mm and 1.25" 9mm) would you suggest that the 2" 30mm should be the only 2" I should get (for now) and any additional starter EPs (like a 11 or 12mm) should be 1.25"?

I kind of wish both eyepieces were the same size so that I could use one Barlow for both and then have the combination of 40x/80x and 133x/266x magnification with a 2X Barlow. Or can I if I get a 2" Barlow and put it in the focuser first. So it would go 2" Focuser - 2" Barlow - 2" to 1.25" adapter - 1.25" EP? Where would a filter go? I don't quite get the sequence of putting it all together.


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Saneless
member


Reged: 12/03/12

Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5563967 - 12/10/12 11:11 AM

Quote:


@BDS316: So, if I go with the Z8 (with the 2" 30mm and 1.25" 9mm) would you suggest that the 2" 30mm should be the only 2" I should get (for now) and any additional starter EPs (like a 11 or 12mm) should be 1.25"?

I kind of wish both eyepieces were the same size so that I could use one Barlow for both and then have the combination of 40x/80x and 133x/266x magnification with a 2X Barlow. Or can I if I get a 2" Barlow and put it in the focuser first. So it would go 2" Focuser - 2" Barlow - 2" to 1.25" adapter - 1.25" EP? Where would a filter go? I don't quite get the sequence of putting it all together.



I like the 30mm 2" that came with the AD8 but I know there's better ones out there. Problem is, am I willing to spend $250 to replace it with something that is a bit better quality and larger FOV? Probably not. Not now, anyway.

As far as the barlow goes, I know GSO makes a 2" barlow that has a 1.25 adapter. I'm not sure if you can drop in the 2" barlow, then drop in the 1.25" adapter, then the 1.25 eyepiece. Never done it or thought about it until now

I already have a decent range of 1.25" eyepieces and instead of worrying about a 2" barlow to get the 30mm to 15mm, I'm just going to buy a very good quality 1.25" 14-16mm very wide view piece instead.

I'd say stick with the 30mm 2" and then just fill out some of the mid/lower range. The only other 2" ones you can get are as low as 24" (I think, maybe 18mm for 100 degree) and up to 50mm. I think 30mm at 68 degrees is enough to see bigger open clusters and that should be fine, for now. You will find out as you use it what you're lacking on the lower-powered end.

You'll probably be ok to get a 12-14mm and a barlow. 14mm is a great zone for this scope (gets it around 85-100x) and a barlow would get it to around 170-200x. Then the 9mm would take care of 133 and 266 if the conditions are right for it.

That's if you just want to add the minimum amount of extra eyepieces. Be sure to get a barlow that lets you remove the end piece to get you 1.5x. Then maybe you could think about getting something like a 24mm and you can go 24/12/15 and with the existing 9 you would do 9/4.5/6.

Again, that's a little more mucking around with unscrewing things and screwing them into other eyepieces a lot but it gives you a lot of versatility.

From there you can just get a good feel for what you like without wasting too much money on pieces you'll never use. And when you feel like upgrading your pieces you'll know that you like xmm better or plan to use ymm all the time.

TLDR Version:
Get a 12 or 24mm 1.25" piece and a barlow to complement your 2" 30mm until you get a better idea what more you want.

Edited by Saneless (12/10/12 11:12 AM)


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BDS316
Carpal Tunnel


Reged: 09/16/09

Loc: Sol 3
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5564021 - 12/10/12 11:50 AM

Quote:


BDS316: So, if I go with the Z8 (with the 2" 30mm and 1.25" 9mm) would you suggest that the 2" 30mm should be the only 2" I should get (for now) and any additional starter EPs (like a 11 or 12mm) should be 1.25"?





I would suggest a GSO rather than Orion (Synta). lower cost, better features and accessories, better mount, etc

The 30mm 2-incher is the same as the one I am using. At f/6 its not bad. This eyepiece you will not use barlowed. A 2 inch Barlow with a 2 inch eyepiece causes significant balance issues for small dobs.

You don't need a 15mm (30mm with 2x barlow) eyepiece with a 68 degree fov if you have an 11mm eyepiece with an 82 degree fov. The 11mm would show you almost the same amount of sky but with higher magnification, darker background, more contrast and a more favorable exit pupil for a medium power eyepiece option.

I always go right from low power to the 11mm Nagler, My 16mm Konig sees little use natively although it is useful when barlowed


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: Saneless]
      #5564082 - 12/10/12 12:31 PM

Quote:

Again, that's a little more mucking around with unscrewing things and screwing them into other eyepieces a lot but it gives you a lot of versatility.



Ha! Yeah...I don't think I would be comfortable taking apart a lens. Chances are I would A. Scratch it. B. Not be able to put it back together the same way.


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Dave74
sage
*****

Reged: 10/23/12

Loc: Gelatinous, MA
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5564100 - 12/10/12 12:45 PM

I use the a GSO 2 inch 2x barlow all the time. They're around $60. Comes with a 1.25 adapter. Pretty simple and easy to use even in the dark. The view from the 30mm in the barlow is one of my favorites. It's true, you might need to counter balance your scope, though.

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Saneless
member


Reged: 12/03/12

Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5564211 - 12/10/12 01:40 PM

Quote:

Quote:

Again, that's a little more mucking around with unscrewing things and screwing them into other eyepieces a lot but it gives you a lot of versatility.



Ha! Yeah...I don't think I would be comfortable taking apart a lens. Chances are I would A. Scratch it. B. Not be able to put it back together the same way.



It's not really taking apart a lens. Have you ever seen an eyepiece filter? That's basically what the bottom cell of the barlow is. It's just a 1/2" or so ring screwed into the bottom of a longer tube. If you screw that piece into an eyepiece (like a filter) then you get 1.5x. If you leave it as is and drop the eyepiece into the longer tube part, you get 2x.

The reason I bring it up is on some nights using a barlow on the 9mm might not work out so well viewing jupiter (266x), but at 1.5x it's at a usually always good 200x (meaning this scope can do 200x even on rough nights up above).


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: Saneless]
      #5564856 - 12/10/12 08:36 PM

Oh boy! I just saw this on another post that the Z8 has ! I have been looking at the Z8 too. I wasn't going to get it just yet, but will the price ever be lower? I hate making rash decisions...

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nploop102
member


Reged: 12/06/12

Loc: Austin, TX
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5564939 - 12/10/12 09:31 PM

I just ordered the Z8 and with the extra 25 bucks off, free shipping and no taxes, it's really a great deal.

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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: nploop102]
      #5564960 - 12/10/12 09:42 PM

Peer pressure!!

Did you order any accessories with it?


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5564978 - 12/10/12 09:59 PM

Ok, So I guess back to the Barlow question...

Zhumell 2in. 2x ED Barlow

Vs.

Astro-Tech AT22XB

Vs.

Any other Barlows?


Also 2" Barlowvs 1.25" Barlow?


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kfiscus
Carpal Tunnel
*****

Reged: 07/09/12

Loc: Albert Lea, MN, USA
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5564984 - 12/10/12 10:05 PM

I'd wait on the barlows. You won't use them as much as you'd think...

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nploop102
member


Reged: 12/06/12

Loc: Austin, TX
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5564989 - 12/10/12 10:09 PM

Quote:

Peer pressure!!

Did you order any accessories with it?




LOL. Peer pressure indeed.
No accessories. Just the scope.


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Dave74
sage
*****

Reged: 10/23/12

Loc: Gelatinous, MA
Re: Orion XT8 questions...and more... new [Re: kfiscus]
      #5564990 - 12/10/12 10:09 PM

They're the same.

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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: Dave74]
      #5565014 - 12/10/12 10:23 PM

Quote:

I'd wait on the barlows. You won't use them as much as you'd think...



Really? Even with only 2 EPs?


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Dave74
sage
*****

Reged: 10/23/12

Loc: Gelatinous, MA
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5565026 - 12/10/12 10:29 PM

I have a 2 inch barlow. It's great with the 30mm. I don't use it much with the 9mm. Things are mushy, and fly through the FOV. You can wait to buy it though. For sure. It's not a must have. A good chair would be a better accessory.

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kfiscus
Carpal Tunnel
*****

Reged: 07/09/12

Loc: Albert Lea, MN, USA
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5565038 - 12/10/12 10:40 PM

I have always given the advice to people starting to buy gear to start with 2 EPs, then a barlow, then a high-power EP if they still want to. If the OP is torn between brands of barlow, I'd say to wait, research, borrow and try, then buy. The nice thing is, barlows are cheaper than EPs.

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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: kfiscus]
      #5565093 - 12/10/12 11:15 PM

Order Placed! Went without the Barlow, but I do think I will be getting one. Just need to find the right one at the right place...

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Shawn Garbett
member


Reged: 10/02/12

Loc: Nashville, TN
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5565131 - 12/10/12 11:35 PM

I recently got the Orion XT10g for my wife. She loves it. I can answer a few of these.

Quote:


Question 1: Orion XT8, is it easy to transport? I live in an apartment and would need move the telescope to a different location to use it.





You'll probably be alright in that regard. For the 10" we're talking about a bigger car, probably a mini-van already. Moving it around is easy. It's the room it takes up in car that can be a problem (got to put kids somewhere). The 8 is probably more manageable.

Quote:


Question 2: Could someone run down eyepiece/lenses in layman's terms. I am versed in cameras/photography so is it the same where the higher the mm the more "zoom" you get? Are there "must have" and "don't ever buy" eyepieces. And what is a Barlow? I wear glasses, does that affect eyepiece selection at all?





Pay attention to the maximum and minimum effective magnification on the website. The range is 29-300X for the XT8. It has a 1200mm focal length. So eyepieces should never be outside of 41mm to 4mm in size. You want a wide field and a higher magnification. I would recommend something around 25-30mm for the wide field. Preferences for the higher mag run between 8-15mm for this size scope. We have the 25mm deep sky Orion and the 9mm ES 100. A 2X barlow would give you a 12.5mm and a 4.5mm equivalent with these two, a good range. Asking about barlows is a loaded question, opinions run the to all extremes about them. I think you have to try one for a year, and use several eyepieces before you make up your mind. If you wear glasses, eye relief is important. 17mm or larger is great. 15mm or less and the field of view will be reduced (I.e., if you get a 100 degree, can you live with only realizing 82 degrees?). Unless you have astigmatism, you can probably focus without the glasses. The package I got also had a 14.5 with illuminated cross hairs for alignment. It's irritating for anything but alignment on the goto, but I don't know how I'd live without it. If you don't get the goto, you won't need anything like it.

300X is for the rare day the weather is perfect, don't go for this to start.

Once you advance to seeing the limitations of your equipment in few years, consider a paracorr. At present, I've learned what the coma is, but haven't been bothered by it enough to drop the $$$. I've heard getting a paracorr, is like a scope upgrade for the dobsonians. So you can enjoy a better scope in years to come.

Quote:


Question 3: How high up is the eyepiece on average when viewing. I'm 5'10", would I need to be sitting or bending over to view? I have a camping chair, but I don't know if it will be tall enough to use.





You'll probably be fine standing. However, some folks like a right-angle finder upgrade to save their neck. Personally, I couldn't do without it--I'm physically fit, but had a back injury years ago that doesn't allow certain positions.

Quote:


Question 4: Any thoughts on Orion's "Build a scope" to customize accessories VS getting the scope and accessories/upgrades separate? What about the Beginner Barlow Kit or the LE Bundles?





Decide and try different configurations. Buy the minimum possible to get started--this is the best advice I got a few months back. To balance it if you get a bigger finder and heavy eyepieces, get a couple 1lb magnets and wrap them in duck tape.

Quote:


Question 5: Everyone talks about how easy a dob is to push around to find something. Can you tighten/loosen the mechanics? I think I am more worried about finding something and then accidentally moving the scope and losing it than not being able to move it at all.





After a few nights with it and a copy of "Turn Left at Orion". I can find things quite rapidly. Never tried to tighten or loosen. If you bump it, you find it again. It's part of the experience, and I find it relaxing. Each to his own.

Quote:


Question 6: What will I actually see when looking at, say, a nebula? I know it won't look like Hubble images, but will it just look like a cloud, or will it be interesting. Anyone have photos that more closely represent visual experience.





A nebula will look like a wisp of grey cotton in an odd shape, unless it's Orion. They are more difficult to see, and nebula filters help. They are still fascinating. I did a public telescope party recently. Setup the dumbbell nebula with a filter. When you tell a 6 year old that's an exploded star, their jaws drop. I personally, having a background in finding resonances in 3-d spaces, found the shape fascinating. Orion, is the only one you can really see the color, and it's jaw-dropping.

Read up on dew. Get a hair dryer. I've been looking into 12V ones to run off a marine battery.

Jupiter is incredible right now, if it weren't for the d*** clouds.


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Allan...
sage


Reged: 10/24/12

Loc: Penticton B.C. Canada
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5565224 - 12/11/12 12:32 AM

I have an XT8 and was wondering if I should buy an ES11 or not. I already have a good Agena 20mm (70 deg) which I like very much; barlow it down with a 2x to 10mm. Will I see much benefit in getting the 11mm (other than wider view)? Or should I go for something like an 8.8mm ES? I dont have anything in that range as yet, though I do have a 14mm that I sometimes try to barlow down to 7mm but often its too much, with my seeing conditions. thanks, Clare

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CosmoSat
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Reged: 07/24/09

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Re: Orion XT8 questions...and more... new [Re: Allan...]
      #5565371 - 12/11/12 03:25 AM

with ur f/6 scope for highpower planetary viewing I would recommend atleast one eyepiece giving u something around an 1mm exit pupil like this Agena 1.25" Enhanced Wide Angle Eyepiece - 6mm to be used whenever the conditions allow.

Clear Skies!


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Billytk
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Reged: 04/22/12

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Re: Orion XT8 questions...and more... new [Re: CosmoSat]
      #5565464 - 12/11/12 07:14 AM

I have a Baader zoom eyepiece and a 2x barlow. The zoom ranges from 24mm to 8mm. It's like having a case of eyepieces in one package. I love it!

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nploop102
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Reged: 12/06/12

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Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5566861 - 12/12/12 12:40 AM

Quote:

Order Placed! Went without the Barlow, but I do think I will be getting one. Just need to find the right one at the right place...




Sweet!


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stargazer424
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Re: Orion XT8 questions...and more... new [Re: nploop102]
      #5567756 - 12/12/12 02:42 PM

Quote:

with ur f/6 scope for highpower planetary viewing I would recommend atleast one eyepiece giving u something around an 1mm exit pupil



Ok so I understand Focal Length, Field of View and Eye Relief. What is the exit pupil?


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pogobbler
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Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5567832 - 12/12/12 03:29 PM

Quote:

Quote:

with ur f/6 scope for highpower planetary viewing I would recommend atleast one eyepiece giving u something around an 1mm exit pupil



Ok so I understand Focal Length, Field of View and Eye Relief. What is the exit pupil?




The exit pupil is basically the diameter of the light exiting the eyepiece. You can calculate it by dividing the focal length of the eyepiece by the focal ratio of the telescope... for example, a 30mm eyepiece in an f/6 scope would give an exit pupil of 30/6 or 5mm. Lower powers have larger exit pupils and higher powers have smaller exit pupils. Since the pupil of the dark adapted eye is going to be around 7mm (the "entrance pupil") for most people, an exit pupil of greater than that is "wasting" light, reducing the effective aperture of the scope, so a power that gives a 7mm exit pupil is generally given as the lowest effective power for the particular scope. People's maximum pupil size will vary, and tends to decrease with age, but 7mm is a decent rule of thumb. At small exit pupils, the floaters in the eye become more prominent-- think of the sharp shadows produced by a concentrated light source, equivalent to a small exit pupil vs. diffuse shadows produced by an extended, diffuse light source. These floaters can be an issue with high powered planetary or lunar observing, bothering some observers more than others. Doing a little math, the 1mm exit pupil the poster recommended would be a 6mm eyepiece (6mm/6 = 1mm), or, of course, a 12mm eyepiece with a 2x Barlow. The magnification would be 200x, which is a good reasonably high power, though, with scopes about 6-8" and up, I like being able to hit around 300x, too, for those nights of very good seeing. I've used such powers on my own XT8 on Jupiter this fall and it was still a very useable power and I could track manually just fine.


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Allan...
sage


Reged: 10/24/12

Loc: Penticton B.C. Canada
Re: Orion XT8 questions...and more... new [Re: pogobbler]
      #5568017 - 12/12/12 05:51 PM

Great (and easy to understand for a newbie) explanation of exit pupil, Tom. My eyes arent that young anymore and I think mine are likely less than 5. How do you find that out? From an Optomestrist/eye exam? I have witnessed the floaters, too; not a big problem though; I learn to ignore them. In the Summer, when I had just got my XT8, I thought that I was looking at insects flying across the scope but when Fall and Winter hit, and they were still there, THEN I knew what was happening...lol. As I said, its no biggy. thanks, Clare

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Starhunter249
sage


Reged: 06/07/10

Re: Orion XT8 questions...and more... new [Re: Allan...]
      #5568280 - 12/12/12 09:06 PM

I have the xt8g and its very portable in two pieces. I seldom carry it all in one piece. Its heavier than the classic version. It should be pretty easy to move around. Stairs will be a two trip affair for just the telescope.

Eyepieces- I rarely use a 4 mm. Most of the time I can push 200x (6mm) on average. Good nights, 250x. Nights of extreme dry and steady air that permits the use of the 4mm, i can push the scope to 400x with a barlow.

I have the 38mm 2inch Q70. It is surprisingly really good for those massive wide field views of the pleades and double cluster for example. Good bang for your bucks.

The owl expanse pieces are cheap and better than the Orions. I think they are $30 dollars a piece. Atleast that is what I paid for them. The 9mm and 15mm are my favorite. The TMBs are not as good as I was expecting. Bright objects will scatter light around the edges. Its really annoying. I don't use them as much. Other eyepieces that I recommend are the sterling plossls. There are wicked sharp and cheap. My favorite is the 20mm. I have two of them for binoviewing.

You can get a lot of good cheap eyepieces that perform to about 90 percent of the top of line expensive eyepieces. I have a poor man budget so I got to shop for bang for the bucks. Wait til after xmas. Massive eyepiece sales and you can pick a lot on the cheap.


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: Starhunter249]
      #5568879 - 12/13/12 09:38 AM

Eyepiece sales AFTER Christmas? I would have thought they would be cheaper right before. Oh well, I will keep my eyes open. Just have to decide which pieces to get. I don't have a huge budget for EPs, and I can't really imagine spending $100+ on one at this time.

Since the telescope I ordered comes with a 2" 30mm Wide Field (40x) and a 1.25" 9mm Plossl (133x), I was thinking of the following to start:

- 2" 2x Barlow so I can use it for both the 30mm and the 9mm giving me a 15mm (80x) and 4.5mm (266x)
- Something in the 12mm range (100x/200x)

With that I would have 40x, 80x, 100x, 133x, 200x, 266x. That would probably give me a good, even starting setup, right?

Is there any need for a beginner to get something LARGER than 30mm or something between 30 and 12?


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Shawn Garbett
member


Reged: 10/02/12

Loc: Nashville, TN
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5568922 - 12/13/12 10:13 AM

Quote:

With that I would have 40x, 80x, 100x, 133x, 200x, 266x. That would probably give me a good, even starting setup, right?




That's a lot of options. The 30mm and 9mm with barlow is enough to start.


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stargazer424
sage


Reged: 10/03/05

Loc: Central NJ
Re: Orion XT8 questions...and more... new [Re: Shawn Garbett]
      #5569217 - 12/13/12 01:00 PM

OK, so Barlow it is! I'll need a 2" Barlow. Been looking at this one:

Zhumell 2in. 2x ED Barlow

Or this one at the same price:
Apertura 2” 2X ED Barlow Lens


Then there is this one, which looks like the same one, and pretty much the same $$ with shipping:
Astro-Tech AT22XB

This one looks the same but its more $$:
GSO's 2" 2x ED Barlow

I am guessing they are ALL the same ones, but with different branding?

Any other websites/stores that would sell any of these for less? Amazon has them at 59.98 too.


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nploop102
member


Reged: 12/06/12

Loc: Austin, TX
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5569236 - 12/13/12 01:07 PM

Let me know how that Barlow works out for you. I might get one as well sometime after Christmas.

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galexand
sage
*****

Reged: 07/10/12

Loc: Bloomington Indiana
Re: Orion XT8 questions...and more... new [Re: stargazer424]
      #5569386 - 12/13/12 02:34 PM

I figure you've got more than enough answers on most of these questions. So for most of them, I'm just going to say: Don't be afraid to under-spend on eyepieces. The "cheap garbage" coming out of China these days is comparable to a precious gem 20 years ago.

But question 6, what do you see. I recommend looking at sketches. Sometimes the artist can get a little carried away with nebulae, but a lot of the sketches here just exactly match how I see it through the eyepiece. For example I would call these drawings of globulars canonical:

http://www.cloudynights.com/ubbthreads/showflat.php?Cat=&Board=Sketching&...

Might want to check out the rest of the board:

http://www.cloudynights.com/ubbthreads/postlist.php/Cat/0/Board/Sketching


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Allan...
sage


Reged: 10/24/12

Loc: Penticton B.C. Canada
Re: Orion XT8 questions...and more... new [Re: galexand]
      #5570049 - 12/13/12 10:08 PM

Would like to hear people's opinions of using weights on the OTA of an XT8. I may order a RACI and heavy eyepieces soon and suspect it will be top heavy. Magnets? Where to get? How best to attach? thanks, Clare

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galexand
sage
*****

Reged: 07/10/12

Loc: Bloomington Indiana
Re: Orion XT8 questions...and more... new [Re: Allan...]
      #5570634 - 12/14/12 10:48 AM

Testing your pupil size...

This may not be accurate, but here's how I *think* I tested the size of my eye's pupil. This could probably stand to be a whole separate thread.

I put a 25mm eyepiece in my 6" F/5 reflector, so that yields an exit pupil of 5mm (mm of eyepiece / F-number of telescope). I found a bright star and slightly de-focused it, just so it was big enough that I could clearly see the secondary shadow. So I was looking at a little white circle with a black hole in the middle, and 4 black lines for the secondary spider supports. I think that white circle basically represents the primary mirror, or equivalently the aperture of the telescope. So if my eye's pupil is bigger than the exit pupil, I would expect to be able to see light from the entire mirror at once. On the other hand, if the exit pupil is larger than my eye's, then part of the mirror would not be visible, the light that hit that part of the mirror would be wasted.

In this case, I could not see the entire mirror. As I moved my eye around (getting different angles into the EP), I could clearly see different parts of the mirror, but never the whole thing at once. So I concluded my pupil was (slightly) less than 5mm. I switched to a 17mm EP (exit pupil 3.4mm), and could easily see the whole mirror at once, so I think the pupil was more than 3.4mm. I'm only 32, but there is a *lot* of localized light pollution on my front porch so I was probably not very dark-adapted so a pupil around 4-5mm seems plausible to me.

The only caveat I can think of is that the exit pupil of the EP might change slightly when it is out-of-focus like that, that's why I de-focus it only a little bit. But for all I know the technique itself is entirely bogus. I just like thinking of new ways to look through the telescope to try to visualize some of the optics concepts I read about..


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Billytk
Pooh-Bah


Reged: 04/22/12

Loc: Lake Mary, Fl.
Re: Orion XT8 questions...and more... new [Re: Allan...]
      #5570786 - 12/14/12 12:35 PM

Quote:

Would like to hear people's opinions of using weights on the OTA of an XT8. I may order a RACI and heavy eyepieces soon and suspect it will be top heavy. Magnets? Where to get? How best to attach? thanks, Clare




Try Scope stuff. I think that's the name? I belive they have them.


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CJK
professor emeritus


Reged: 12/05/12

Loc: Northeast TN
Re: Orion XT8 questions...and more... new [Re: Allan...]
      #5572077 - 12/15/12 07:06 AM

Quote:

Would like to hear people's opinions of using weights on the OTA of an XT8. I may order a RACI and heavy eyepieces soon and suspect it will be top heavy. Magnets? Where to get? How best to attach? thanks, Clare




ScopeStuff likely has what you need: Telescope Balancing Kit

-- Chris


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kenrenard
Carpal Tunnel


Reged: 12/13/12

Loc: Dunmore, PA
Re: Orion XT8 questions...and more... new [Re: CJK]
      #5573359 - 12/15/12 10:44 PM

I have an XT 8 and used cheap magnet hooks from Harbor Freight on the bottom of the Tube 4 makes it balance perfectly with heavy eyepieces. They are about $2 for a pair.

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Allan...
sage


Reged: 10/24/12

Loc: Penticton B.C. Canada
Re: Orion XT8 questions...and more... new [Re: CJK]
      #5573525 - 12/16/12 01:39 AM

Anyone ever try this approach on a dob instead of adding weights?
http://www.astronomy-shoppe.com/scope-gripps.htm?107,21


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frito
Pooh-Bah


Reged: 10/05/12

Loc: Fremont, CA
Re: Orion XT8 questions...and more... new [Re: Allan...]
      #5573553 - 12/16/12 02:18 AM

Quote:

Anyone ever try this approach on a dob instead of adding weights?
http://www.astronomy-shoppe.com/scope-gripps.htm?107,21




ok i'll answer your questions on this subject as a i have an XT8 and have had to rebalance it.

first off. a normal sized RACI finder plus a ~1 lb eyepiece is not enough to throw a stock configured XT8 with the springs attached off balance.

i only ran into balance issues once i modified my alt bearing surfaces with FRP so they are much smoother, i expected balance problems with the modification and i indeed got them. here is the skinny on it. with my very smooth FRP to stock teflon pad bearing surfaces using the springs always i do not have balance issues with my 8x50 RACI + Rigel + small eyepieces (most 1-1/4" size plossls) in the scope. if i throw say my 40mm plossl and the barlow in i get problems with no counter weight. if i throw in either my 38mm Q70 or 16mm Nagler i get balance problems, both weigh in around 1 lb.

solution was simple either remove the RACI finder to reduce weight or strap a counter weight i made from dead D and C cell batteries taped together with electrical tape to the bottom of the tube via a velcro strap i already use for holding wires for dew heater cables to the OTA for. i played with it till i found the right config and i think it is 4x D's and 2x C's i have kept some extra dead batteries with my observing gear in the event i need more but i have not thus far and i've stuck some serious eyepieces into my scope out at parties before. magnets and other more fancy counter balances can work and look better or whatever but what i'm doing works perfectly but i will stress once again i only really run into this issue because i modified my ALT bearing surfaces to make them many times smoother and easier to move than a stock XT8 is. without the modification i think it would require some major top end loading to cause problems as long as you are using the tension springs on the scope. without the tension springs its closer to how my scope works with the modification but still not as smooth or easy to move.


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Allan...
sage


Reged: 10/24/12

Loc: Penticton B.C. Canada
Re: Orion XT8 questions...and more... new [Re: frito]
      #5573582 - 12/16/12 03:20 AM

Thanks, Dwayne (and others); great info. I will leave my XT8 stock for now and see how it goes with a RACI and the odd heavier eyepiece. Appreciate greatly the comments. Clare

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