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Advice for all purpose grab and go OTA?

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#26 dmgriff

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Posted 14 January 2016 - 02:40 PM

The 6in f/5 newt makes the most sense to me for your Twilight I. I have a Twilight I alt/az mount and the 6in f/5 newt is about the biggest aperture/fl newt the mount can handle (imo). 

 

Other posters have indicated the versatility of the 6in newtonian, so I shall simply sign off.

 

Good viewing,

 

Dave


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#27 gene 4181

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Posted 14 January 2016 - 02:58 PM

 My most used scope is a 6inch f5 skywatcher  reflector , very versatile , wide fov and very good planetary/moon views , if the seeing is good.  I've had this scope for quite awhile too ,  at 219 dollars its a real bargain considering  the aperture and versatility . It cools quickly , holds collimation fairly well .  Another honorable mention here , $ -wise is the 102mm ES  f6.5mm achro  and since it includes the 2inch diagonal a very good deal also if a little color is acceptable. 299$


Edited by gene 4181, 14 January 2016 - 03:37 PM.

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#28 Sky Muse

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Posted 14 January 2016 - 04:48 PM

Collimation is not the beast as it might seem at first.  It consists simply of aiming the celestial light-cone produced by the parabolic primary mirror directly at the perfectly-flat surface of the secondary mirror.  Then, the secondary, the "middleman" in transferring the "goods", is aligned to aim said light-cone directly into the focusser, through the eyepiece and into the observer's pupil, like so...

 

http://www.company7....tPath649499.jpg

 

 

There are only two components inside a Newtonian, a 6" f/5 specifically: the primary and secondary mirrors...

 

mirrors.jpg

 

*Note the white "doughnut" in the center of the primary mirror.

 

The secondary mirror is oval in shape, and fastened to the secondary-stalk at a 45° angle.  But when the primary mirror "sees" it, and as the "scene" is reflected within the secondary when looking down into the focusser, the secondary appears to be perfectly round, and just as the primary...

 

collimation.jpg

 

 

This is the simple collimation-cap that was provided with my 6" f/5, however the Celestron may not come with one...

 

collimation cap.jpg

 

http://agenaastro.co...t-eyepiece.html

 

The cap is then inserted into the focusser in place of the eyepiece...

 

Here is the "scene" again, larger, but thrown out of collimation, and in order to demonstrate its various aspects, and as seen through the collimation-cap...

 

bad collimation3.jpg

 

1. The pinhole of the collimation cap when looking through it.

2. The white "doughnut" of the primary mirror.

3. The inner reflective surface of the collimation cap.

4. The secondary mirror itself.

5. The secondary assembly's spider-vanes.

6. The primary mirror itself.

7. The primary mirror's clips which hold the mirror in place.  All three must be visible, and evenly as shown.

8. The inside of the focusser's drawtube.

 

After collimation is complete, the "scene" should appear, again, like so...

 

collimation1.jpg

 

*Note that the secondary, #4 within the image above, doesn't seem quite centered within the "scene".  Fast Newtonians require their secondary mirrors to be slightly off-set, thereby to direct all of the gathered light into the focusser's drawtube, and so to fully illuminate the eyepiece...

 

http://www.skyandtel...condary-mirror/

 

 

These are the screws used to adjust the tilts, the positions, of both mirrors...

 

collimation2.jpg

 

The primary cell's larger screws adjust the tilt, whilst the smaller, slimmer screws lock the position in place once adjusted.  The secondary's larger, center screw is used to move the secondary mirror back and forth, and to twist the secondary mirror's flat surface side-to-side, and all in order to center the flat surface directly beneath and parallel to the focusser drawtube's opening...

 

secondary scene3a.jpg

 

 

In future, you might want a passive, combination Cheshire/sight-tube tool in addition...

 

I'd prefer this one, and from across the "pond"... http://www.firstligh...g-eyepiece.html

 

This is Celestron's, in any event... http://agenaastro.co...tors-94182.html

 

Collimation instructions... http://www.astro-bab...ation guide.htm

 

There are numerous instructions for collimating online, including for the use of the aforementioned tools.

 

 

A 6" f/5 does not need a laser-collimator, as attractive and fascinating to some as they might be; an 8" f/6 might, and a 12" f/5 most definitely.  It is very easy to look into the focusser and reach back to the primary cell's adjustment screws, at the same time, with the relatively-short tube of a 6" f/5.  Laser-collimators are for those times when you don't feel like climbing up and down a ladder...

 

http://www.cloudynig...-1412985122.jpg

 

Quite a few laser collimators require collimating in and of themselves, and before one can even use it to collimate their telescope.  In any event, the work performed by the laser-collimator is usually double-checked, for peace of mind, and with guess-what...

 

http://www.firstligh..._collimator.jpg

 

:whee:


Edited by Sky Muse, 14 January 2016 - 06:45 PM.

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#29 Tony Flanders

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Posted 15 January 2016 - 07:08 AM

Again, thanks for all the responses!  I was really starting to thing that a 6" Newt was perfect for my needs, but after reading these last two posts I think I get the pro's and con's of Newts vs refractors a little better.  It sounded like the 6" Newt probably really is the best all rounder, it has decent aperture, relatively wide FOV, and moderate power.  That said it sounds like small refractors are actually better grab and go's.


Yes, that pretty much sums it up. A 6-inch f/5 Newt is a fundamentally better scope than a 120-mm f/5 achromat. But the achromat is ready to observe just about the moment you take it outside, whereas the Newt needs to cool and be collimated.

Once you know how to do it, collimation is fast and easy. I often just check the collimation, decide it's still fine, and that's the end of it. Tweaking it typically requires about a minute. Cooldown is a much bigger issue.
 
Here are two other things worth considering. Newtonians are nearly immune to dew. Even with a built-in dewshield, the refractor will start to dew up long before the Newt.
 
With both optical tubes, you would definitely end up observing from a sitting position if you're using the Twilight I mount. Stability is roughly a wash. The refractor is lighter and more compact, but with the Newt you can keep the legs fully retracted, because you're viewing from the top of the tube rather than the bottom.
 
With the Newtonian, you could probably use a standard chair, because your head height barely changes with a 6-inch f/5 Newt as you move from horizon to zenith. When the eyepiece is highest, it's horizontal, so it's at the same height as your head. When it's lowest, your head is above the eyepiece.
 
With the refractor, you would probably want an adjustable-height chair, which is an additional expense. Here, the eyepiece height and eyepiece angle work against each other rather than with each other. When the eyepiece is at its lowest (and that's very low indeed!) your head is at the same height as the eyepiece -- also very low.
 

Would a 80mm APO and a 6" Newt be redundant?


  Absolutely not! Those two scopes would complement each other beautifully.
 

Back to focal reducers, is there really no downside?  If there wasn't wouldn't that make a Mak-Cas the perfect all rounder?  Its small, optically sealed, holds collimation well, pretty good aperture/$, sharp image, powerful AND wide FOV with a focal reducer.  This seems to good to be true, otherwise everyone would do this instead of spending exponentially more on refractors.  Am I missing something?


Yes, several things. Sealed is bad, not good. It means that the scope cools down very slowly. Collimation is a double-edged sword. It's fine as long as the scope does stay collimated, but many Mak-Cas's, especially the cheaper ones, cannot be collimated by the user. So if the collimation does drift, it means a trip back to the factory.

 

Many low-cost Mak-Cas's also come with built-in focusers -- often ones that accept only 1.25-inch eyepeices -- and cannot accept a reducer, which needs to be inserted in front of the focuser. Sticking a reducer into a 1.25-inch focuser doesn't help one bit in eliminating the narrow FOV inherent in a long focal ratio combined with a narrow focusing tube.

 

SCTs are generally more versatile in this regard. A conventional f/10 SCT combined with a 2-inch back and a reducer-corrector is indeed a good wide-field instrument. But that's a pretty expensive package.


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#30 Jon Isaacs

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Posted 15 January 2016 - 08:12 AM

Back to focal reducers, is there really no downside?  If there wasn't wouldn't that make a Mak-Cas the perfect all rounder?  Its small, optically sealed, holds collimation well, pretty good aperture/$, sharp image, powerful AND wide FOV with a focal reducer.  This seems to good to be true, otherwise everyone would do this instead of spending exponentially more on refractors.  Am I missing something?

 

 

 

The focal reducer doesn't actually change the focal length of the scope nor does it change the maximum field of view possible, those are determined by the optics and the geometry of the telescope.  What a focal reducer does is change the effective focal length of the scope much the same way a Barlow does.  You can get a wider field of view with the same eyepiece with a focal reducer but eventually you run into the fact that the rear port of a 5 inch Mak, of a 5 or 6 inch SCT is only 1 inch and diameter, vignetting is inevitable. 

 

Over the years, I have been blessed with a large number of scopes and the opportunity to spend enough time with them to get to know them. In this size range, these include refractors from 60mm to 120mm, achros and ED/apos, Newtonians, 3 inches, 4.5 inches 130mm and 6 inches of a variety of focal ratios as well as Maks and SCTs, 90mm, 4 inches and 5 inches.  This is the way I see it based on my experiences:

 

An all "purpose grab and go scope" needs to be reasonably portable, one trip out the door on the mount is my criteria.  It needs to be capable of reasonably wide fields of view as well as clean, crisp high magnification views and it needs to be thermally stable, take it outside or to a local park, I want the scope to be giving me decent quality high power views essentially the moment I am out the door, seeing of course permitting.  

 

Refractors, Cats and Newtonians can provide good quality high magnification views. both Newtonians and good quality refractors can provide the low power, wide field views.... But only the refractor is stable enough thermally that it can provide nearly it's best views within moments..  Newtonians and Cats take real time to become truly thermally stable and if the temperature is dropping, they may never thermally stabilize.  To be rock solid at 300x, my experience is that a hour might be enough but some nights, it just never happens.  

 

Not long ago I setup a Orion 127mm Mak before sunset. I waited about an hour to begin observing and I observed for about an hour, either the seeing was not good or the scope had not cooled down.  I went inside and grabbed my 120mm ED refractor, brought it out, looked at the same target I had been struggling with, a close double star, and the refractor provided a clean view and made the split.  Even with scopes this size, thermal issues are very important.

 

For me, grab and go.. it's a refractor.. Whether it's an 80mm, 100mm or 120mm, they can all do the job.  

 

Jon


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#31 NIckwin

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Posted 15 January 2016 - 10:00 AM

Thank you everyone for the wealth of information!  I expected a lot of input, but I didn't think I'd learn as much from this as I have.  I think I'm all but decided on the 150XLT.  Like I said, Ive always wanted a nice 80mm range APO (ever since I laid eyes on a Meade 5000 triplet as a kid), and to everyone who suggested one, I totally get it, they sound awesome, but I decided to go with the 6" f/5 Newt first for a few reasons.  First and foremost at $220 I'll actually buy and and be using it right away instead of just thinking about pulling the trigger for weeks, months years like I would with a $1000+ purchase.  Secondly the 6" Newts seem to be, being kind of middle of the road in a lot of ways, the ideal multipurpose telescope.  Third I feel like learning to and dealing with collimation and cool down is part of the experience!  I don't think I would truly appreciate the awesome ease of use of a refractor without experiencing this first :) .  I definitely plan on adding a nice 80mm range APO down the road, and considering I'm only forking out $220 this time it might not be that far off.

 

Now, I'm already starting to thinking EPs.  As I said I have a Hyperion 24mm and a TV 2x plossl.  I'm thinking if the Hyperion's edge of field is really bad at f/5 I could trade it pretty much strait up for a xcel/hd60 25mm.  Would a 6.6mm Xcel/hd60 be a good addition for high power?  This would give me 3.3mm*, 6.6mm, 12mm*, 24mm (*with barlow).  Then I'm thinking I could add something like a 32mm 68 degree later on for really wide views.  Am I on track here?


Edited by NIckwin, 15 January 2016 - 10:18 AM.

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#32 Jon Isaacs

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Posted 15 January 2016 - 10:22 AM

 

First and foremost at $220 I'll actually buy and and be using it right away instead of just thinking about pulling the trigger for weeks, months years like I would with a $1000+ purchase.

 

That is certainly a good solid reason to buy the 6 inch F/5 Newtonian.  My concern is the viability of a scope that heavy on the Twilight 1 mount.  

 

:question:

 

Jon



#33 NIckwin

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Posted 15 January 2016 - 10:59 AM

 

 

First and foremost at $220 I'll actually buy and and be using it right away instead of just thinking about pulling the trigger for weeks, months years like I would with a $1000+ purchase.

 

That is certainly a good solid reason to buy the 6 inch F/5 Newtonian.  My concern is the viability of a scope that heavy on the Twilight 1 mount.  

 

:question:

 

Jon

 

Good question. The whole reason I bought the Twlight I was because the instability of the Celestron Nexstar 4i mount I was using drove me nuts.  

 

Twilight I is rated at for a 18lb payload.  The 150XLT is 12lbs.  So thats approx. 65% of max payload.  Is there a certain ratio that usually provides decent stability?  I learned the hard way that max payload is what a mount will support, not necessarily what it will support well...  Any Twilight I users here?


Edited by NIckwin, 15 January 2016 - 12:31 PM.


#34 Sky Muse

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Posted 15 January 2016 - 01:27 PM

The Twilight I, whilst rated at said load-capacity, should, ideally, also take into account the bulk of the telescope's optical tube when attached thereto.  My AT Voyager I handles my 6" f/5 satisfactorily...

 

ATVI mount8a.jpg

 

Note how the optical tube is practically centered over the mount, and by virtue of its curved mounting-arm.

 

Still, 6" f/5 Newtonians are bundled and sold with mounts structured similarly to the Twilight I...

 

http://www.firstligh...-az4-mount.html

 

Other examples...

 

http://www.cloudynig...newt/?p=6451417

http://4.bp.blogspot...iscovery+02.JPG

 

This one is also similar, but on a smaller scale, and with a 5" f/5 instead... http://www.cloudynig...11199_thumb.jpg

 

Some owners of the Twilight I strengthen the mounting arm... http://www.cloudynig...ount/?p=5168623

 

Different folks mount their telescopes in different ways, therefore there are no hard-and-fast rules in that regard.

 

The mounting-arm of the Twilight I adjusts to several positions.  Positioning the arm straight-up might be an option with the 6" f/5. 

 

There is also the option, in future, of an equatorial mount, and for imaging in addition to visual use.


Edited by Sky Muse, 15 January 2016 - 01:28 PM.


#35 REC

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Posted 15 January 2016 - 01:53 PM

Collimation is not the beast as it might seem at first.  It consists simply of aiming the celestial light-cone produced by the parabolic primary mirror directly at the perfectly-flat surface of the secondary mirror.  Then, the secondary, the "middleman" in transferring the "goods", is aligned to aim said light-cone directly into the focusser, through the eyepiece and into the observer's pupil, like so...

 

http://www.company7....tPath649499.jpg

 

 

There are only two components inside a Newtonian, a 6" f/5 specifically: the primary and secondary mirrors...

 

attachicon.gifmirrors.jpg

 

*Note the white "doughnut" in the center of the primary mirror.

 

The secondary mirror is oval in shape, and fastened to the secondary-stalk at a 45° angle.  But when the primary mirror "sees" it, and as the "scene" is reflected within the secondary when looking down into the focusser, the secondary appears to be perfectly round, and just as the primary...

 

attachicon.gifcollimation.jpg

 

 

This is the simple collimation-cap that was provided with my 6" f/5, however the Celestron may not come with one...

 

attachicon.gifcollimation cap.jpg

 

http://agenaastro.co...t-eyepiece.html

 

The cap is then inserted into the focusser in place of the eyepiece...

 

Here is the "scene" again, larger, but thrown out of collimation, and in order to demonstrate its various aspects, and as seen through the collimation-cap...

 

attachicon.gifbad collimation3.jpg

 

1. The pinhole of the collimation cap when looking through it.

2. The white "doughnut" of the primary mirror.

3. The inner reflective surface of the collimation cap.

4. The secondary mirror itself.

5. The secondary assembly's spider-vanes.

6. The primary mirror itself.

7. The primary mirror's clips which hold the mirror in place.  All three must be visible, and evenly as shown.

8. The inside of the focusser's drawtube.

 

After collimation is complete, the "scene" should appear, again, like so...

 

attachicon.gifcollimation1.jpg

 

*Note that the secondary, #4 within the image above, doesn't seem quite centered within the "scene".  Fast Newtonians require their secondary mirrors to be slightly off-set, thereby to direct all of the gathered light into the focusser's drawtube, and so to fully illuminate the eyepiece...

 

http://www.skyandtel...condary-mirror/

 

 

These are the screws used to adjust the tilts, the positions, of both mirrors...

 

attachicon.gifcollimation2.jpg

 

The primary cell's larger screws adjust the tilt, whilst the smaller, slimmer screws lock the position in place once adjusted.  The secondary's larger, center screw is used to move the secondary mirror back and forth, and to twist the secondary mirror's flat surface side-to-side, and all in order to center the flat surface directly beneath and parallel to the focusser drawtube's opening...

 

attachicon.gifsecondary scene3a.jpg

 

 

In future, you might want a passive, combination Cheshire/sight-tube tool in addition...

 

I'd prefer this one, and from across the "pond"... http://www.firstligh...g-eyepiece.html

 

This is Celestron's, in any event... http://agenaastro.co...tors-94182.html

 

Collimation instructions... http://www.astro-bab...ation guide.htm

 

There are numerous instructions for collimating online, including for the use of the aforementioned tools.

 

 

A 6" f/5 does not need a laser-collimator, as attractive and fascinating to some as they might be; an 8" f/6 might, and a 12" f/5 most definitely.  It is very easy to look into the focusser and reach back to the primary cell's adjustment screws, at the same time, with the relatively-short tube of a 6" f/5.  Laser-collimators are for those times when you don't feel like climbing up and down a ladder...

 

http://www.cloudynig...-1412985122.jpg

 

Quite a few laser collimators require collimating in and of themselves, and before one can even use it to collimate their telescope.  In any event, the work performed by the laser-collimator is usually double-checked, for peace of mind, and with guess-what...

 

http://www.firstligh..._collimator.jpg

 

:whee:

This is an excellent description and great images with circles and arrows! Very nicely done and easy to understand. I always wondered why the secondary wasn't exactly in the center of my f/4.7 scope? I do use the cap, but also have a Hitech laser which shows me on collimated pretty well. I get clean tight stars. This post should be made a sticky note. :bow:


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#36 Sky Muse

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Posted 15 January 2016 - 02:04 PM

Now, I'm already starting to thinking EPs.  As I said I have a Hyperion 24mm and a TV 2x plossl.  I'm thinking if the Hyperion's edge of field is really bad at f/5 I could trade it pretty much strait up for a xcel/hd60 25mm.  Would a 6.6mm Xcel/hd60 be a good addition for high power?  This would give me 3.3mm*, 6.6mm, 12mm*, 24mm (*with barlow).  Then I'm thinking I could add something like a 32mm 68 degree later on for really wide views.  Am I on track here?

 

That seems to be a logical progression.  This one is on sale at present...

 

http://agenaastro.co...f-eyepiece.html

 

Seven elements is a lot of glass, but with the 6" aperture in combination with the eyepiece's modern multi-coatings, the loss of light-throughput should be negligible; 82° field-of-view and 13.2mm of eye-relief.

 

Do you wear eyeglasses when observing?



#37 Jon Isaacs

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Posted 15 January 2016 - 02:26 PM

The Twilight I, whilst rated at said load-capacity, should, ideally, also take into account the bulk of the telescope's optical tube when attached thereto.  My AT Voyager I handles my 6" f/5 satisfactorily...

 

attachicon.gifATVI mount8a.jpg

 

Note how the optical tube is practically centered over the mount, and by virtue of its curved mounting-arm.

 

Still, 6" f/5 Newtonians are bundled and sold with mounts structured similarly to the Twilight I...

 

http://www.firstligh...-az4-mount.html

 

Other examples...

 

http://www.cloudynig...newt/?p=6451417

http://4.bp.blogspot...iscovery+02.JPG

 

This one is also similar, but on a smaller scale, and with a 5" f/5 instead... http://www.cloudynig...11199_thumb.jpg

 

Some owners of the Twilight I strengthen the mounting arm... http://www.cloudynig...ount/?p=5168623

 

Different folks mount their telescopes in different ways, therefore there are no hard-and-fast rules in that regard.

 

The mounting-arm of the Twilight I adjusts to several positions.  Positioning the arm straight-up might be an option with the 6" f/5. 

 

There is also the option, in future, of an equatorial mount, and for imaging in addition to visual use.

 

 

The AZ-4, is a far more robust mount than the Twilight 1, the first link shows the version with the 1.75 inch Stainless Steel legs.. It's sturdy.  Without the stainless steel legs, I would be concerned and the third link, I am also skeptical.. 

 

One thing I have learned the hard way:  Undermounting a scope is the quickest way to prevent a good optic from providing good views.  When the Twilight 1 mounts were on sale, I tried my 4 inch TeleVue refractor on one.  It was not up to it, I am concerned that the Twilight 1 will also compromise the 6 inch F/5.  People make these things work, get by with scopes that vibrate when you try to focus..  I try to avoid situations like that, I try to avoid recommending a scope for a mount that will be compromised.

 

Jon



#38 NIckwin

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Posted 15 January 2016 - 03:02 PM

Thats unfortunate, but I appreciate the honesty.  I guess I'll hold off and see if I can find someone who's has tried this combo before I make a decision. Maybe I could go down a size.  Are there any 5" Newts that are as appealing price to performance wise as the Omni xlt 150?


Edited by NIckwin, 15 January 2016 - 03:04 PM.


#39 SteveG

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Posted 15 January 2016 - 03:24 PM

Thats unfortunate, but I appreciate the honesty.  I guess I'll hold off and see if I can find someone who's has tried this combo before I make a decision. Maybe I could go down a size.  Are there any 5" Newts that are as appealing price to performance wise as the Omni xlt 150?

Yes, and these were going to be my recommendations:

 

BTW I believe you are on the right track in picking a small, fast reflector for this "mission".

 

My travel scope is an Ares 5 - Same as the AWB OneSky. A collapsable 5" f5 reflector.

This is an excellent scope, receiving rave reviews everywhere:

http://store.astrono...fldv5hrraps6rf4

 

The other option is to get this new Meade which is a similar optic in a solid tube:

http://www.highpoint...CFVJufgodjJEEOw

 

Both of these scopes have a dovetail rail mounted on them, which will allow you to quickly connect and balance on your mount. One drawback over the Omni, they both only have 1.25" focusers.

 

With mine, I use a Meade SWA 24/68 for low-power, and a 13T6 for med  power, which I can barlow for high power. This scopes are compact & lightweight, and are excellent "all-pupose" scopes. While I love ED refractors, my Ares 5" shows a ton more than my 80 ED. At a dark site, it is fantastic.

 

And this one just popped up - from Zhumell. I like this one the best as it has the rail and rings: http://www.telescope...ector-telescope


Edited by SteveG, 15 January 2016 - 03:33 PM.

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#40 lamplight

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Posted 15 January 2016 - 04:52 PM

Apo doublet. :) viewing in moments.  but if you want that extra aperture the reflector on a better mount.  I also learned the hard way. They even sell scope/mount packages that are innappropriately matched.  Just my $.02



#41 OrdinaryLight

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Posted 15 January 2016 - 05:29 PM

And this one just popped up - from Zhumell. I like this one the best as it has the rail and rings: http://www.telescope...ector-telescope

 

That Zhumell looks great - the rings allow the eyepiece position to be rotated for comfort, but if portability is a primary concern then the AWB OneSky is the one to get. It's lighter, it collapses for shorter length, and the low profile helical focuser takes up less room. Like Steve, I've found the AWB OneSky to make an excellent travelscope for trips to dark skies: http://www.theopport...ky-travelscope/

 

When needed, collimation of the scope is also very quick because you can see through the focuser while reaching the primary mirror adjustment screws on the back of the scope.



#42 NIckwin

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Posted 15 January 2016 - 05:35 PM

The Omni xlt 150 still seems to stand out as a really good deal at 6" with a 2" focuser for $220.  I definitely envisioned a 2" EP in the mix.

 

I just saw this package at high point:

http://www.highpoint...dar127065-maz01

 

Thats a substantially heaver scope.  I know that doesn't mean it will work well, but I'm still wondering.  That AWB OneSky looks pretty cool too though.


Edited by NIckwin, 15 January 2016 - 05:49 PM.


#43 Jon Isaacs

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Posted 15 January 2016 - 06:29 PM

The Omni xlt 150 still seems to stand out as a really good deal at 6" with a 2" focuser for $220.  I definitely envisioned a 2" EP in the mix.

 

I just saw this package at high point:

http://www.highpoint...dar127065-maz01

 

Thats a substantially heaver scope.  I know that doesn't mean it will work well, but I'm still wondering.  That AWB OneSky looks pretty cool too though.

 

 

That is a substantially heavier, more expensive scope.. Looking at the scopeand it's size, I went back and re-read your original requirements:

 

"Other info and summary:

 

- My backyard is a green zone boarding on blue on the light pollution map I've used, but I do have some local light from neighbors and lots of trees.  Its also on a small lake, so I think that may adversely effect seeing in the summer.  Some of my viewing will be done from really dark sites, but generally transparency is not great here in Michigan but sometimes we get lucky.  

 

- Dew is always an issue here.

 

- The only accessories I already have and would love to be able to keep using are the Twilight I mount and a Baader Hyperion 24mm (I'm reading this might not be too good at f/5) and a TV 2x barlow.

 

- Needs to be grab and go, easily transportable by one person, quick to set up.

 

-Good for everything from the moon to scanning star fields (I'd like it to be great at the latter)

 

- Looking for a bright, wide, sharp image.

 

- I might want to mount it on a Goto mount down the road.

 

EDIT: I'm not concerned with photography at this point.
EDIT:  Since its not worth anything, I'll keep my frankenstein ETX90 OTA for high power viewing.
EDIT:  I'll keep the OTA mounted in-between uses for back-yard use, but I will also travel with it and have to set it up in the field.
<$1000"

 

============

 

My Question:

 

Why Not an 8 inch Dob?  

 

It's definitely an easy one person setup.  

 

It is more capable at just about everything than the scopes being discussed. It will be better on the planets, better for any deep sky object that fits in the field of view, and it is capable of a 2.2 degree TFoV with the right eyepiece. The mount is simple and stable.. 

 

If you are going to go with a Newtonian, why compromise by trying to make it fit your Twilight 1 mount?  Dobs are popular because they are effective..  

 

Jon


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#44 CollinofAlabama

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Posted 15 January 2016 - 07:29 PM

I agree with Jon, here.  If you want grab 'n go, get the Lunt I wrote about above.  It costs just over $700 for the OTA, but it'll be ready in a jiffy.  Of course, you might need to improve your mount a bit, but with the tube extension, it'll probably ride okay.  But if you go the newtonian route, why not go big?  I really do think that in the 6" and less reflector world, refractors bring a lot to the table, but when you get to an 8" (or larger) mirror, you're simply at the point of no return regarding the number of photons getting into your eye.  Refractors big enough to begin to keep up (6" and larger) become enormous beasts,  Color gets very problematic for achros and ED/APOs get used-car sized in costs. But both require crazy-big mounts, so big that the joy of astronomy can get killed in a fellow.

 

So I think you should keep to your original premise, and get a 4" ED refractor (or 80mm ED refractor) -- or get an 8" dob.  The 8" dob will have it all over any of these other scopes at the eyepiece.  It's field of view isn't huge, but it is compared to a Maksutov, and 1.8-2 degrees ain't so bad.  But the details will amaze you.  A 6" newt is a good scope, but it has a lot of compromises that, to me, aren't as nice as a 4" refractor for grab 'n go.  OTOH, neither will compete with a good 8" dob, which will cost a little less than double the 6" F/5 newt, but only 55% of the 4" ED scope.  But it's your money and time, and I agree, the price tag on the Celestrons is a siren's call that's hard to quell.  Good luck.


Edited by CollinofAlabama, 15 January 2016 - 07:51 PM.

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#45 SteveG

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Posted 15 January 2016 - 08:00 PM

http://www.theopport...ky-travelscope/


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#46 lamplight

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Posted 15 January 2016 - 08:14 PM

Aw he'll.. now I want one. 



#47 Sky Muse

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Posted 15 January 2016 - 08:40 PM

Thats unfortunate, but I appreciate the honesty.  I guess I'll hold off and see if I can find someone who's has tried this combo before I make a decision. Maybe I could go down a size.  Are there any 5" Newts that are as appealing price to performance wise as the Omni xlt 150?

 

With this... http://www.telescope...ector-telescope

 

...you can do the exact same thing I did with my "StarBlast 6".  Transfer the OTA over to the Twilight I...

 

6 f5d.jpg

 

There's also the Vixen 5" f/5, and also with a plastic 1.25" focusser... http://www.adorama.c...CFdgPgQodrMYM0g

 

A 5" f/5 Newtonian with a 2"/1.25" focusser is somewhat rare here in the States, perhaps being that smaller refractors are more popular here for imaging... http://www.firstligh...30p-ds-ota.html ...for example, only.

 

That one is designed for astrophotography, primarily, but it can also be used for visual.  The focusser even has a fine adjustment knob. 

 

I've ordered from overseas before, several times, in both directions.  Are you game?  Given its small size, it would ship well.

 

Teleskop Service offers the same... http://www.teleskop-...rd-focuser.html

 

...US $247.89 to your door(POST).  Never choose UPS Express, and not due to the fact that it costs more.


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#48 NIckwin

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Posted 15 January 2016 - 08:48 PM

Are there any relatively inexpensive manual alt-az mounts out there that would support the xlt 150 adequately? 

 

Will a Twilight 1 hold a 100mm ED doublet? 80mm?

 

8" dob is an interesting thought too and I could probably fit it in my back seat...  The thing with the twilight 1 is I literally just bought it.  Yeah, I didn't really plan that one out.  I really thought with its "18lb" payload it would handle a 4" refractor or 5" newt.  I guess I wasn't really thinking as big as 6" at the time when I bought it.



#49 NIckwin

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Posted 15 January 2016 - 08:55 PM

 

Thats unfortunate, but I appreciate the honesty.  I guess I'll hold off and see if I can find someone who's has tried this combo before I make a decision. Maybe I could go down a size.  Are there any 5" Newts that are as appealing price to performance wise as the Omni xlt 150?

 

With this... http://www.telescope...ector-telescope

 

...you can do the exact same thing I did with my "StarBlast 6".  Transfer the OTA over to the Twilight I...

 

attachicon.gif6 f5d.jpg

 

There's also the Vixen 5" f/5, and also with a plastic 1.25" focusser... http://www.adorama.c...CFdgPgQodrMYM0g

 

A 5" f/5 Newtonian with a 2"/1.25" focusser is somewhat rare here in the States, perhaps being that smaller refractors are more popular here for imaging... http://www.firstligh...30p-ds-ota.html ...for example, only.

 

That one is designed for astrophotography, primarily, but it can also be used for visual.  The focusser even has a fine adjustment knob. 

 

I've ordered from overseas before, several times, in both directions.  Are you game?  Given its small size, it would ship well.

 

Teleskop Service offers the same... http://www.teleskop-...rd-focuser.html

 

...US $247.89 to your door(POST).  Never choose UPS Express, and not due to the fact that it costs more.

 

Nice looking options.  Is the focuser something that can be easily swapped out on a newtonian?



#50 Sky Muse

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Posted 15 January 2016 - 09:04 PM

This is the present incarnation of my AT Voyager I, and in black, minus the extension pier and eyepiece tray which are no longer available... http://agenaastro.co...ltaz-mount.html

 

The extension pier is for refractors in any event.  A 6" f/5 Newtonian would certainly be doable on the GSO, and the latter has the curved mounting-arm.




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