34 replies to this topic

[Nightskyman]

I am looking to purchase a refractor for visual only viewing of planets and moon. I will be using an alt-az tripod. What I am specifically asking is for thoughts and recommendations for ideal specifications but not brand nor model. Rather aperture, focal length, and focal ratio to get started with and why? As a side question, what magnifications will be of most value for these targets?

[balcon3]

I find that 100mm aperture is the minimum that gives me satisfying views of planets. Of course the larger the better, and many decide on a 5 inch or 6 inch scope. But considerations of cost, portability, and ease of mounting then come into play. For planets, the QUALITY of the scope is important. Best would be a good quality triplet or ED doublet apochromat. Focal ratios of f7-8 or longer make it easier to control chromatic aberration, which is very important for planetary viewing, Achromats can also work well, but they need to have longer focal rations, which can make them difficult to handle and mount.

Edited by balcon3, 17 February 2025 - 05:24 AM.

[Jay_Reynolds_Freeman]

Some generalities:

 

o Aperture: More is better. How much can you transport/carry/set up/afford?

 

o Focal length and focal ratio: The limiting factor here is excellent color correction. For a given optical design, color errors get worse as aperture increases or focal ratio shortens. Designs that use expensive glass types (ED, fluorite) have better color correction, and well-designed triplets (which are even more expensive) are better still.

 

o Claims of excellent color correction at fast focal ratios are often exaggerated. Note that "APO" is a marketing term which means absolutely nothing -- telescopes described as "APO"s tend to be achromats (two pieces of glass) that use a fancy glass type for one piece. They usually do have substantially less color error than achromats of the same aperture and focal length that use less fancy and less expensive glass types, but they are not magic -- if they are too large and/or too fast the color error will be objectionable.

 

o Triplet objectives are often quite heavy, due to using three rather thick pieces of glass. Thus triplet optical tube assemblies tend to be nose-heavy, which means that you must either add weight to the back end of the tube or accept a wide variation in eyepiece height when you observe. The latter issue is likely no problem for small apertures.

 

I personally have used several sizes of Vixen's fluorite doublets, with apertures from 55 mm to 102 mm and focal ratios of f/8 or f/9. In visual use, they have showed no color error that I could find. I have used several superb triplets by Roland Christen of Astro-Physics, with apertures from 92 mm to 180 mm and focal ratios of f/6.3 to f/9, and they have also been color-free for visual work. I once had a Meade 127 mm f/9 ED achromat, and it showed enough color error to be give marginally inferior views to several similar-sized instruments that were either triplets or used more expensive glass types.

 

o Magnification: This will depend on aperture, seeing and what planet you are looking at. In excellent seeing, I believe many planetary observers find magnifications of as much as twice the clear aperture in millimeters to be useful occasionally, but I think that magnifications equaling the clear aperture in millimeters, or perhaps of 1.3 times that value, are more common.

 

Clear sky ...

[Martinbruce]

Nightskyman,

It seems your questions have been thoroughly answered. I only noticed a couple of things. You currently have a AT80EDL and I’m sure you’ve looked at the full EDL lineup. They are quite nice but to put them on your existing mount with its 15 pound limit would be a consideration, as I’m sure you’ve have thought of this. Lastly, I note that we look through the same sky here in SE PA and I can’t get past 200x on the best of nights. Mostly I’m between 100 - 150x. SE PA there are light domes all around between Philly, Baltimore, Lancaster, Harrisburg, etc. Always looking for just a tinny bit more darkness. Thanks for the post. 

[balcon3]

As a side question, what magnifications will be of most value for these targets?

One can enjoy the planets and moon at any magnification. Last night I spent 15 minutes looking at the moon at 22x. It had a 3D effect of being suspended in space more so than when I went to higher magnifications. You can see the belts on Jupiter at 40x or lower. But at 150x or higher, the details really become apparent. For Saturn, I think the sweet spot is even higher, say around 200x or higher, but it's still enjoyable at lower powers. This is one of the reasons that I prefer 4 inch or larger refractors for the planets; you can get to these magnifications without the image becoming too dim. The moon is enjoyable at all magnification as long as your scope is sharp and has high contrast.

[bobhen]

I see you live in southern PA. I've been living in southern PA all my life. So I know what the typical seeing is like in our state and at our location.

 

Considerations

1. I don't like refractors below 100mm for the moon and planets. They never left me totally satisfied but always left me wanting more. And I've had some good 80mm refractors, including a Vixen 80mm Fluorite doublet. 

2. The planets are the most demanding objects to observe, and being such, require superb optics. Average optics will not deliver all the very fine details that one wants to tease out when observing the planets. Many of those fine planetary details can be lost to low contrast or light scatter or SA, etc. with less than excellent optics.

3.The seeing in PA is notoriously average on most nights. I owned an Astro-Physics 6" refractor and that scope could do 100x per-inch in excellent seeing. But on the vast majority of nights of average seeing, that scope was limited to the 200-300x range on the planets and a little higher on the moon. And of course a large scope takes longer to set up and requires a larger mount.

 

Size and Optical Recommendations 

1. I would suggest an aperture of 100mm to 130mm. The 120mm aperture is really nice, as scopes of that size are still very portable but have more aperture than the 100mm size. It's kind of a Goldilocks size; not too big and not too small.

2. For visual in the 100mm to120mm size, you don't need a triplet, as the scopes will be light and portable even at f8

3. But you will need high quality optics. Get the best you can afford. Don't skimp. I mean, if you want average optics, you could get a larger Newtonian for the same money. Price is a good indicator of optical quality.

4. With a FPL 53 or Fluorite doublet, a FL of around F7.5 to F8 is plenty. 

 

Mount Recommendations

1. You can get a powered alt/az mount from various vendors

2. If you get a manual alt/az mount, I would suggest that the mount have slow motion controls. All mount manufacturers that DO NOT have slow motion controls say their motions are so smooth that slow motion controls are not needed. They are needed, especially at the high powers used for the moon and planets. 

 

My Thoughts and My Experience

1. I've owned 15 refractors of variousness sizes and of various designs and of varying quality and another 10 telescopes that were not refractors and also of various sizes and varying quality.

2. I love using refractors for the moon and planets, especially here in PA with our seeing, fast changing weather and the mid to mid-high position of the planets on their best appearances. And very high quality refractors have been my choice here for some time. They just seem not to disappoint, even in average seeing and challenging conditions. 

3. I'm not going to tell you what to purchase. I'll just tell you the brands that I've owned and really liked. And when I speak of high quality optics these and similar brands are what I am talking about: Takahashi, Astro-Physics, APM with LZOS optics. There are others of course. And there are some decent mid-priced offerings these days. I currently have a 120mm F7.5 triplet and a 100mm F7.4 doublet and I use them whenever I can. 

 

Good luck.

 

Bob

[therealdmt]

I’d get a 4" (100mm) ED doublet, preferably one incorporating an FPL-53 or equivalent (ex., FCD-100) glass element, or if you have the money, fluorite crystal. Focal ratio of from f/7 to f/9.

 

Why? Well, first of all, there is no one right answer. My reasoning is that over 4" starts to involve more cool down time before one can get high magnification views through the scope, but one of the biggest attractions of a refractor is convenience. They start getting less convenient as you get much over 4", unless you have an observatory. If you have an observatory (or similar), I’d go for 5" or 6" if possible. Meanwhile, regarding less than 4", well I certainly haven’t done every aperture size, but I know my 4" refractor gives a lot more satisfying planetary views than my ~ 3" refractor*. Obviously 90mm wouldn’t be dramatically different than 100mm, nor would 110mm be dramatically different than 100mm. Seems to a lot of people that 4" is the sweet spot. You might tweak your desired aperture from there depending on whether you more value convenience (go a bit smaller) or brightness and resolution (go a bit bigger).

 

*(though I was happy to have my ~ 3" 72mm when it was essentially my only telescope for over a year)

 

Why an ED doublet? — an ED doublet at f/7 to f/9 will provide sufficient correction of chromatic aberration for visual use and will cool down quicker and be lighter than a triplet. Nevertheless, some choose a triplet for both ultimate correction and to allow a faster focal ratio. For visual, a faster focal ratio means a wider field of view for a given eyepiece. Actually, there are a number of variables here that one may juggle to get their own ideal scope though. A 4 element scope can be even shorter (faster) while also providing a flat field, but cost will tend to go up compared to a doublet.
On the other hand, one could go with a slower focal ratio and perhaps with less expensive ED glass to get excellent color correction, such as with a few f/11 telescope models that are available. Some people love these longer scopes, especially for planetary and the Moon. Mounting can be a bit more challenging with a longer scope though due to moment arm and also eyepiece height (if you point the telescope near zenith, the eyepiece of a long telescope will be quite low unless the mount is up high off the ground, but in that case, then when looking at a low target, the eyepiece will be up high). But, long scopes do look cool and suit planetary viewing well. Field of view for a given eyepiece is less with a longer telescope, so you’d want either wide field of view eyepieces and/or probably a mount with slow motion controls (perhaps a driven mount).

 

Budget is a factor for many of us. You’ll have to decide where you’re comfortable. Lots of people enjoy their planetary views through an achromat, so if an ED doublet is too expensive, don’t worry about it and enjoy what you can afford. If planetary is your priority with an achromatic refractor, I’d go for a longer telescope (slower focal ratio) to reduce chromatic aberration, and you can also investigate minus violet filters and such to help from there if needed.

 

Magnifications would be very roughly about 200x (might typically range from 150x to 250x, but could be more or less depending on your local seeing conditions and how high the planet or the Moon is in the sky. Your own eye becomes a limiting factor too at higher magnification, for example due to floaters).

 

If only having one telescope, I’ve often thought that a 120ED would be a nice size. A little too big for optimum convenience perhaps, but there’d be that bit of extra aperture that would nice to have compared to never being able to go over 4".

 

Convenience, aperture, budget, and aesthetics might be the general factors to mix. Beyond that, one may have specific feature requirements. Happy hunting

Edited by therealdmt, 17 February 2025 - 10:18 AM.

[Sketcher]

I am looking to purchase a refractor for visual only viewing of planets and moon. I will be using an alt-az tripod. What I am specifically asking is for thoughts and recommendations for ideal specifications but not brand nor model. Rather aperture, focal length, and focal ratio to get started with and why? As a side question, what magnifications will be of most value for these targets?

Aperture: 80mm

Focal Length: 560mm

Focal Ratio: f/7

 

Magnifications: up to 200x depending on seeing conditions, quality of optics, and the observer's eyes.  In other words, there will be times when somewhat lower magnifications would likely make for better choices.

 

Why?  Because that's what you have and because that's pretty much ideal for getting started with visual observations of the moon and planets.  Furthermore, I've made lunar and planetary observations with an 80mm f/5 achromat and know how much can be seen with such a telescope; and your 80mm refractor is a more capable telescope than my ST-80.  Furthermore, in The Amateur Astronomer's Handbook by Muirden, page 24 the author discourages starting out with larger apertures, adding that the greatest observers started out with modest equipment and became better observers by learning how to make the most of modest equipment.

 

Why up to 200x?  Because that would be about 63x per inch of aperture.  Furthermore, 60x per inch is an often-quoted maximum magnification.  Furthermore, I've beneficially made use of 67x per inch of aperture with a 1-inch aperture when observing the moon:

 

 

Take up sketching (serious observing as opposed to causal looking) with your 80mm aperture and you'll be surprised at the capabilities of you and that telescope.  Those skills could later be transferred and made good use of while using other telescopes.

[PKDfan]

I've got 62m & 100mm apochromats and both are superb on the moon and even the planets. Optical quality can effect a huge variance in image fdelity. If your a one scope refractor fan then i'd pony up for a 100mm FPL-53 or equivalent and get a longer ratio rather than shorter.

And go with a long production optic rather than newer stuff.

Evostar has spectacular sales on right now. BUY BUY BUY.


CSS
Lance

[Nightskyman]

as my signature indicates, I have an AT 80EDL on a Sky-Watcher AZ5. I am newer to this hobby and this my first and also

It’s the only telescope I’ve ever owned so I have nothing to compare it to. As far as what I see I believe it to be good. I would prefer one scope as compared to several and I felt that the price for this one was a great deal as far as quality and price. I should also say it is only used in my backyard and I like the quick easy setup for viewing.You might ask why I’m asking about Using another refractor. While I do enjoy looking at nebulas, clusters, and doubles, I find that most of my time is spent on Jupiter, Saturn, and the moon. Maybe it is because they are easy targets. I so often read that many suggest a longer focal length/ratio would be better suited for lunar and planetary viewing. I must say that the first time I saw the rings around Saturn, it exceeded my expectations based on others experiences with similar scopes. I think as much as anything, I am looking for any input from those much more experienced observers now that I believe I am better able to understand what is being said. I hope this follow-up clarifies rather than confuses my actual questions,

[Jon Isaacs]

as my signature indicates, I have an AT 80EDL on a Sky-Watcher AZ5. I am newer to this hobby and this my first and also

It’s the only telescope I’ve ever owned so I have nothing to compare it to. As far as what I see I believe it to be good. I would prefer one scope as compared to several and I felt that the price for this one was a great deal as far as quality and price. I should also say it is only used in my backyard and I like the quick easy setup for viewing.You might ask why I’m asking about Using another refractor. While I do enjoy looking at nebulas, clusters, and doubles, I find that most of my time is spent on Jupiter, Saturn, and the moon. Maybe it is because they are easy targets. I so often read that many suggest a longer focal length/ratio would be better suited for lunar and planetary viewing. I must say that the first time I saw the rings around Saturn, it exceeded my expectations based on others experiences with similar scopes. I think as much as anything, I am looking for any input from those much more experienced observers now that I believe I am better able to understand what is being said. I hope this follow-up clarifies rather than confuses my actual questions,

 

 

There is a lot to be seen in an 80mm apo and the more you observe, the more you see.  A larger scope will show you more observing with an 80mm will help you develop your skills.  I look at the observations Thomas Jensen makes with his 63mm Telementor, it's something to strive for.  

 

Jon

[balcon3]

 I would prefer one scope as compared to several and I felt that the price for this one was a great deal as far as quality and price. I should also say it is only used in my backyard and I like the quick easy setup for viewing.You might ask why I’m asking about Using another refractor.

I was in a situation very much like yours. I had an TS80mmEDL (still have it) and also a larger scope. I wanted something with the convenience of the 80mm refractor but with more reach like the larger scope. I got a fine 100mm refractor, f7.4. It has fulfilled all my expectations. It could easily be my only scope. It is large enough aperture and of high enough quality to give excellent views on planets (I use it at 250x or sometimes even higher if the seeing permits). And it can give a wide enough view to frame all but the largest targets (up to 3.6 degrees total field of view). When my 80 EDL was my main scope I was often looking for more magnification and more light gathering. I don’t feel that way with the 100mm scope. If you are like me, I think you will be very satisfied with the move up to 100mm. You could go higher to 115 or 120mm, but I didn’t want to because those scopes are larger, heavier and more of a challenge to mount. There is a reason why many experienced observers say that everyone should have a 4 inch refractor.

[Oldfracguy]

I used to have the same mount, the Sky-Watcher AZ5 with the "Heavy Duty" tripod with the 1.75" diameter tubular steel legs.  I was able to mount a Sky-Watcher 100ED Evostar on it because these Sky-Watcher Evostars are lighter in weight than the comparable KUO-made ED refractors like the AT80EDL, AT102EDL, etc.  Here is a photo of my old Sky-Watcher 100ED Evostar on the AZ5:

 

 

 

The previous owner of this scope always dreamt of owning a Takahashi some day, so he had this SW 100ED Evostar expertly painted white.  When he finally did get an FC-100 he sold this scope.  I was able to see a lot of things for the first time using this 4" refractor, and was able to appreciate how much clearer the images appear in one of these ED scopes with the better glass, but your AT80EDL is the same type of scope that provides exceptionally sharp views.  One thing I did have a problem with using the fairly long SW 100ED Evostar on the SW AZ5 mount was reaching the Azimuth (side-to-side) position control knob.  On the AZ5 that Azimuth control sticks out at a right angle to the axis of the telescope tube, so it can be hard to reach unless you have long arms:

 

Edited by Oldfracguy, 18 February 2025 - 02:00 PM.

[Sketcher]

I am looking for any input from those much more experienced observers now that I believe I am better able to understand what is being said. I hope this follow-up clarifies rather than confuses my actual questions,

(You might want to ignore everything here other than the paragraph that appears below in bold type )

 

Many participants in these forums have many decades of experience.  I've been seriously using astronomical telescopes since about 1968.  I moved to a (literally) middle of nowhere location in 1981 (or thereabouts) and stayed here -- because of this hobby.  I have two observatories (one a two-story affair with a roll-off roof, the other an open-air observatory) on my property.  Don't let my use of and talk of small telescopes fool you into thinking I'm a beginner.  It's just that I know the (often hidden) value of smaller telescopes.

 

The below linked CN thread should give some idea of what I mean by observing vs. looking when using a telescope.  I started that thread before I had learned how to post images of my sketches, but you'll find many detailed verbal descriptions of observations that I made while using a $15 (price when new) 50mm Galileoscope.  Your 80mm refractor is capable of far more.

 

https://www.cloudyni...e-observations/

 

I know what I'm talking about when I speak of the capabilities of small telescopes, the importance of observing vs. "viewing" or just looking, etc.

 

But if you just want a better, more capable refractor for lunar and planetary "viewing" than what you currently have, then you can pretty much ignore much of what I've posted in this thread and simply go out and purchase the highest quality, largest aperture apochromat refractor (f-ratio wouldn't matter for your purposes with a high-quality apochromat) that you can afford and make use of.  It's really as simple as that -- since you want to ignore brands.

 

A telescope like this:

 

 

which happens to be a 130mm f/6.4 oiled-triplet apochromat that I purchased new in 1995 for $3000 (came with no star diagonal, no eyepieces, no finder, no mount, no tripod -- just the telescope in a case) would be very capable when it comes to "viewing" the moon and planets (as well as many other celestial sights).  Nowadays I could probably sell that telescope for $10,000 (without including the mount, etc). -- considering the brand  .

 

But don't be so quick to dismiss the value of smaller telescopes such as this modest little Galileoscope:

 

 

and of course, the fine telescope that you currently have.

 

Telescopes aren't capable of seeing anything.  It's up to their users to learn how to see all that they're capable of showing.  Some users just look at stuff, never learning how to "see".  Others who've learned how to see will generally be able to see more while using smaller, lower quality, less capable telescopes.

 

P.S.  I prefer using German Equatorial Mounts (GEMs) for my own lunar and planetary observing (actually, for pretty much all of my astronomical purposes).  GEMs were invented specifically for use with astronomical telescopes.  But I also know about alt-az mounts and their capabilities:

 

One is better for astronomical purposes:

 

The other is better for terrestrial purposes, and/or for those who've never learned how to use a GEM:

[Nightskyman]

how do you quote part of someone’s response

[balcon3]

how do you quote part of someone’s response

Hit the Quote button and then erase the part you don't want. That's how I do it, anyway.

[mikeDnight]

 I'm very happy with my 4" & 5" refractors and have no desire for anything larger, but quality really counts when it comes to the planet's. A good 4" Apo/ED around F7 or 8 will knock the socks off a 6" F8/10 achromat, even with the Moon. I love both my scopes, but if I had to only keep one, it would be the 4" F8 apo..

 If you have good eyepieces that will give you upto 250X you'll have all the power you'll need. However, the better the optics, the better the performance on a good night with steady seeing, and the harder the scope can be pushed effectively.  The Moon takes high mag well on a steady night, but the planet's are a bit more stubborn.  Jupiter will play nicely at around 180X with lots of detail on view. Mars likes higher powers of 200X to 250X,  or even 300X. Saturn is similar to Mars as regards magnification. A SvBony 3-8mm Zoom is a great planetary eyepiece. 

Edited by mikeDnight, 19 February 2025 - 04:14 PM.

[Nightskyman]

 

I know what I'm talking about when I speak of the capabilities of small telescopes, the importance of observing vs. "viewing" or just looking, etc.

 

 

 

 

Maybe a better question for me to ask is in regards to the telescope I now have, an AT80-EDL, what do you feel are its strong points and which do you feel are it’s shortcomings? What areas should this excel with and which areas not as much? What are the best target suited for this particular telescope and which ones the least? as my first and only telescope, did I make a good choice? Please don’t laugh, but between the scope, the tripod, the diagonal, and a few basic eyepieces it’s more than I initially intended to spend, but I realize quickly that my initial intentions weren’t very realistic either.

[Sketcher]

Maybe a better question for me to ask is in regards to the telescope I now have, an AT80-EDL, what do you feel are its strong points and which do you feel are it’s shortcomings? What areas should this excel with and which areas not as much? What are the best target suited for this particular telescope and which ones the least? as my first and only telescope, did I make a good choice? Please don’t laugh, but between the scope, the tripod, the diagonal, and a few basic eyepieces it’s more than I initially intended to spend, but I realize quickly that my initial intentions weren’t very realistic either.

In my opinion your AT80-EDL is an excellent 80mm telescope for visual use.  Its strong points would be its optical and mechanical qualities and the fact that it comes with a 2-inch focuser.  For an 80mm visual telescope I wouldn't list anything as a shortcoming.  For its aperture, I would be hard pressed to point out anything that I would look to improve as far as the telescope itself is concerned.

 

In my opinion, your only path toward getting anything better (in the refractor world) would, all other things being equal, be a larger aperture refractor of equal or better quality.

 

Yes, the price of that telescope is on the high side for 80mm refractors, but in return you got a higher quality telescope, and many find paying more for higher quality is money well spent.

 

A less expensive 80mm telescope, say an achromat of similar f-ratio, would perform similarly for most deep-sky objects; but your higher quality telescope would perform better in showing low-contrast planetary details -- one of those areas where optical quality matters more.

 

Did you make a good choice?  For the most part, I would say yes.  Though personally (and many would disagree here) I would have preferred a less expensive achromat as a first telescope.  But that preference really only comes in if you make mistakes in caring for the telescope.  Otherwise, as long as you were OK with the cost, yeah, I think it was good choice.

 

For the moon, that telescope ought to be awesome!  For a meticulous visual observer, it ought to take years before becoming bored with what that telescope is capable of revealing.  If one needs something better for lunar observation in less time, then one (in my opinion) hasn't been making the most of what that 80mm telescope is capable of showing.

 

For planets, it depends on the observer and their expectations.  In an ideal world where one comes in with no expectations, that telescope ought to be an awesome planetary telescope as well.  But in the real world, many have higher (often unrealistic) expectations from seeing photos and/or sketches made by others while using larger telescopes.  But as a first telescope, that telescope ought to provide good enough planetary views to keep a person content for a fair length of time.

 

But it takes experience to see all that any telescope is capable of showing a person.  A person sees more when they try to sketch what they're looking at.  There's absolutely no need to share your sketches with anyone else unless/until you want to for one reason or another.  It's the simple act of looking at a planet (or whatever else) closely enough to actually justify making a sketch that's important.  It trains the eye-brain system to "see" more.  It leads one to become a better observer.  This is something I highly recommend.  Don't let it bother you if you're not satisfied with your sketches.  That's very, very normal.  Most astro-sketchers don't sketch to make works of art.  They sketch to become better observers and/or to produce hard, physical records of their observations.

 

I don't know anything about the quality and quantity of your observations with your current telescope.  But I would venture to guess that there's room for improvement in those areas before moving on to a more capable telescope.  That thread on the Galileoscope that I posted earlier would give some idea of the kinds of details one could be shooting for when making visual observations with any telescope.

 

Of course, when it comes to deep-sky observations one's sky conditions -- especially in the realm of light-pollution and light-trespass can greatly limit what one will be able to see.  But there's also a very real element of knowledge and experience involved here, just as in any other aspect of visual astronomy.

 

With practice, we all end up seeing more.  Through sketching, the entire eye-brain training/learning process improves more rapidly.  In a very real way, one might even say: "One hasn't really seen something until they've sketched it."

 

Hopefully this has shed at least a little light on your questions and provided direction toward seeing more -- with your current telescope as well as with any future telescope.

 

P.S.  I have larger telescopes, but for the past few years I've limited myself to the use of 6-inch and smaller apertures for the simple reason that I can see more than enough with 6-inch and smaller telescopes to keep me going strong in this hobby.  Of course, many others prefer using telescopes as large as they can afford and handle.  Different people are different in their preferences.  What's right for one person may be wrong for another person.

[Lookitup]

 I'm very happy with my 4" & 5" refractors and have no desire for anything larger, but quality really counts when it comes to the planet's. A good 4" Apo/ED around F7 or 8 will knock the socks off a 6" F8/10 achromat, even with the Moon. I love both my scopes, but if I had to only keep one, it would be the 4" F8 apo..

 If you have good eyepieces that will give you upto 250X you'll have all the power you'll need. However, the better the optics, the better the performance on a good night with steady seeing, and the harder the scope can be pushed effectively.  The Moon takes high mag well on a steady night, but the planet's are a bit more stubborn.  Jupiter will play nicely at around 180X with lots of detail on view. Maes likes higher powers of 200X to 250X,  or even 300X. Saturn is similar to Mars as regards magnification. A SvBony 3-8mm Zoom is a great planetary eyepiece. 

Between my Tak 100DF and SM 125ED I pick the 4" Tak on Jupiter 90% of the time due to seeing. With binoviewer X170 is the highest I can achieve in clear nights. My 125ED at X250 was sharp once in 1+ years. Actually I just ordered a F/11 Planeta scope to see if the increased focusing range helps with the current sky conditions.

[hendric]

For targets, beyond the moon and planets, take a look at the Messier open clusters like the M35 - M38 or the Double Cluster. They can be quite pretty within a wider field of view that the AT80EDT provides. Those you can see in pretty light polluted skies.  The brighter large nebulas like the Orion, Cocoon, Omega would also be good choices, and will look better the darker the skies. Galaxies can be pretty underwhelming IMO naked eye unless you are in very dark skies.

[T1R2]

I used to have the same mount, the Sky-Watcher AZ5 with the "Heavy Duty" tripod with the 1.75" diameter tubular steel legs.  I was able to mount a Sky-Watcher 100ED Evostar on it because these Sky-Watcher Evostars are lighter in weight than the comparable KUO-made ED refractors like the AT80EDL, AT102EDL, etc.  Here is a photo of my old Sky-Watcher 100ED Evostar on the AZ5:

 

101_1497.JPG

 

 

The previous owner of this scope always dreamt of owning a Takahashi some day, so he had this SW 100ED Evostar expertly painted white.  When he finally did get an FC-100 he sold this scope.  I was able to see a lot of things for the first time using this 4" refractor, and was able to appreciate how much clearer the images appear in one of these ED scopes with the better glass, but your AT80EDL is the same type of scope that provides exceptionally sharp views.  One thing I did have a problem with using the fairly long SW 100ED Evostar on the SW AZ5 mount was reaching the Azimuth (side-to-side) position control knob.  On the AZ5 that Azimuth control sticks out at a right angle to the axis of the telescope tube, so it can be hard to reach unless you have long arms:

 

101_1289.JPG

Were the AZ5 slo-mo knobs able to be replaced with the standard Vixen cables, (the ones that are 12" long) ? 

[T1R2]

Usually depending on your seeing, you should be able to push the scope magnification wise to 2x is aperture in mm's, so an 80mm = 160x, 100mm= 200x etc. you can even go over that a few x's. I couldn't find an EP that gave exactly 120x in my 60mm, but I did have 6mm that gives 133x and it works fine for lunar/ planetary/ double stars etc and still doesn't dim the view past being unusable, and I occasionally go way past that to 160x on the brighter moon. 

[Erik Bakker]

Between my Tak 100DF and SM 125ED I pick the 4" Tak on Jupiter 90% of the time due to seeing. With binoviewer X170 is the highest I can achieve in clear nights. My 125ED at X250 was sharp once in 1+ years. Actually I just ordered a F/11 Planeta scope to see if the increased focusing range helps with the current sky conditions.

This is probably the essence in a nutshell for the question the OP asked  

 

To add: a great 100mm f/8 doublet is a superb planetary scope for up to around 200x, a similar 125mm up to around 250x and a great 150mm doublet up to around 300x. Many times, local seeing will max out at 150x, in those cases he bigger scopes will show more color saturation and easier views because of larger exit pupils at a given magnification. 

 

On very good nights, my Questar 7 would show more than any of them, only to be dwarfed in both bulk and planetary views by my custom 16” f/5 Dob. But those nights were very rare where I live.

 

Generally, a great 125mm f/8 doublet is the Goldilocks for planetary observing IME, that is is you can mount and carry it to your convenience, otherwise a great 100mm f/8 doublet is a fine choice. Both go together well with your 80mm EDL, although the 125mm scope would be a better addition perfomance wise.

 

If I lived in the US, I would not look much further than the wonderful A-T EDL scopes to complement your A-T 80 EDL .

[bobhen]

Between my Tak 100DF and SM 125ED I pick the 4" Tak on Jupiter 90% of the time due to seeing. With binoviewer X170 is the highest I can achieve in clear nights. My 125ED at X250 was sharp once in 1+ years. Actually I just ordered a F/11 Planeta scope to see if the increased focusing range helps with the current sky conditions.

The increase in FL will not help with the seeing. The best defense against average seeing is to get the absolute best and highest quality optics.

 

Bob