Whats the best all round telescope currently?

[gregbradley]

A controversial question no doubt but I am interested in others thoughts about what the best all round telescope is at the moment.

I suppose that should be in 2 categories - imaging and visual although some scopes are great at both.

Also within reasonable price limits. Not $200K mountain top 60 inch RCs etc.

The trend seems to be towards largish aperture and fast F ratio. But then Corrected Dall Kirkhams and other variants are becoming popular. The venerable Newtonian seems to be popular with the F3.8 and F4 versions around. APO's are still popular as an all round good performer, mainly for wider field shots which suits many targets.

Greg.

[glend]

You will get a lot of varying opinions on this question, sort of like asking what's the best car. It's all about what you want to do with it. As an all-rounder, and if I could only have one that can do both I'd suggest something like a 10" newt (I prefer f5) with a slightly oversized secondary for imaging work but which can still be used for visual with an extension tube. These scopes tend to be very cheap and of good quality with good limiting magnitude and resolution. I should point out that I have one, but I also have a 16" f 4.5 dob, a f12 achro refractor, and ED Triplet f6 refractor, the newt gets use the most but they all have their own advantages at times.

Personally I'd avoid very fast Newts as they are hard to collimate, so don't travel well and really don't offer any advantages to imagers - where a few seconds less sub exposure time is irrelevant when you are guiding and on a good mount; but that's just my opinion.

[Wavytone]

Greg,

IMHO for visual use f/7 is the sweet spot. It permits a selection of eyepieces giving a range 10:1 or a tad more between the lowest and highest magnification. What's more, at f/7 its easy to make a newtonian reflector that performs superbly across this range, and its not too hard to find excellent ED refractors close to f/7 as well around 100-120mm aperture.

For imaging... the answer depends on what you want to photograph. The Gegenschein, or Barnards Loop ? M102 ? Mars ? Moon ?

Fast Newtonians... As low-to-medium power wide-field light buckets they're fine but don't expect them to perform well at high magnifications. They are popular only because:

a) very low cost commercially, far cheaper than any other design of comparable aperture (SCT's or Maks);

b) its easy to mount fast ones at f/4 quite adequately on a base made of MDF, chipboard or plywood with little care given to the engineering of it (Meade lighbridges come to mind). Mounting an f/7 or f/10 Newtonian is more difficult mechanically and requires a much larger and heavier mount.

c) fits on the backseat of a small car,

d) the availability of mass produced thin mirrors at f/4 that are adequate optically. 30 years ago these were far more costly, hand-made one-offs and optical quality usually poor below f/4.5.

[glend]

It's useful to remember that while all Dobs are Newtonians not all Newtonians are Dobs. GEM mounted Newts do not have MDF bases.

[Wavytone]

Glen,

... put it this way - if we could all buy 30cm Maksutovs for less than the price of a cheap 30cm Newtonian I'm sure they'd be the most popular scope on the planet.

But it can't happen.

Mind you Meade and Celestron SCT's have always sold well enough despite their price and limitations.

[Alchemy]

Imaging preference deep sky

My preference is for refractors, ready to use out of the box, travel well.

An all round telescope should be one you can use frequently, so a focal length of say 1000mm or less means seeing isn't such a huge consideration, from 4-6 inches keeps cost to affordable, APO goes without saying, Somewhere from f5 to f7. I don't travel with mine but a scope of this size is transportable and can be easily setup by one person.
There would be many in that class, the TAK106 has a great following although I don't have one, but it would fit the bill, Id prefer something a little longer say 150mm F5 .....

Visual.......

No sorry, colored dots don't interest me, you need to GO BIG, but that's probably not within the parameters you specified.

[Peter Ward]

I tend to agree with Clive, a big APO is pretty hard to beat.

Given my home is prone to bushfire threats, and I'm often away from home, and despite everything being insured, I've asked the family to grab my AP refractors if we have to be evacuated...as they would be very difficult to replace.

The AP155 with the 4" field flattener is a superb imaging/solar/visual instrument. Sure, I've used bigger/wider/shorter 'scopes...but none more beautifully finished or corrected.

[GeoffW1]

Hi,

After stuffing around for years, visual only, I settled on a 200 mm SCT on a go to alt az mount. Like all such solutions it lacks a bit here and there.

Horses for courses truly here.

Cheers

[Paul Haese]

My best views of Jupiter in near perfect seeing were as good as looking at an image in good seeing and that was through an 18" Newtonian just after an imaging session. I saw this with Anthony through my SDM scope. Still vividly etched in my mind.

However for imaging, refractors just make life easier. If I could afford an 12" refractor I would buy one. And if they made them at f5, it would be near perfect.

Though for angular resolution you cannot beat diameter. Either RC or CD are more affordable now for imaging and give you good imaging speed without have the moment that is associated with Newtonians. That said Newtonians have good contrast and less problems with collimation.

To be perfectly frank I could not guess which is the best all round scope currently. If money was no object then a very large aperture refractor would be the go, otherwise each has its limits and issues if your budget is under 25K.

[gregbradley]

Yuri at TEC is making 250mm APOs at the moment. He also makes a 20 inch RC that Roland Christian thought was the best he'd ever used. Images from it looked good but it needs extra baffling or something minor to correct some odd flaring on bright stars.

Looking over images posted on the net though 20 inch RCOS images are at the very top in my opinion. Crawford, Croman, Gabany (yes even with the colour). The 20 inch RCOS boys.

Peter, shouldn't you update that request to take the Honders first?

Officina Stellare have a whole range of fast astrographs up to 20 inch and F5 or F3.8.

Agreed, a good refractor does make life easier.

Greg.

[The Mekon]

Greg, assuming "there can be only one" I think you have the scope for sale right now and the only reason I'm not buying as it is too soon after offloading my own AP130, and I can still manage my large reflector and a smaller refractor quite well.
So when I want to reduce to just one scope it will be a 140mm APO. I'm on the wait list but don't hold out much hope - Roland may well be in a nursing home before my name comes around.

Advantages of such a sized refractor?

1. Portability (no ramps needed for transport)
2. Perfect for double stars and planter.
3. Performance on deep sky is worth double its aperture (never saw a 8' SCT that came near my 130 on deep sky)
4. Photographic capability.

-that's 4 P's in a row, so if you are talking just one all round scope it would be a 140 APO for me.

[marc4darkskies]

I honestly don't think there is such a thing as an "all-rounder" telescope. But if there is Greg, you probably own one! :lol:

[LewisM]

Both categories - REFRACTOR in my opinion.

I am not a fan at all of artificial inclusions in images like diffraction spikes, so that rules out MOST reflectors save the corrector plate types.

Whilst I would LOVE to own a Tak CCA250, at the end of the day, I will always come back to refractors.

[strongmanmike]

Hey Greg, I have an even better question with a much simpler answer:

"how long is a piece if string?" :lol:

That said and if $200K is your limit, I'd opt for a 12" refractor for visual and a well made fork mounted 20" F3.5 Corrected Newt (that has image plane tilt adjust) for imaging :D

Have to say, at least from an imaging perspective and keeping the price actually affordable and delivery time realistic, I have been very happy with my AG12 though :shrug:... it can do both THIS (http://www.pbase.com/strongmanmike2002/image/141738539/original) and THIS (http://www.pbase.com/strongmanmike2002/image/159445895/original) just change the camera. Of course if you add a 1.8X dedicated barlow then you can cover almost all bases and it is still quite fast :thumbsup:. It is portable enough for many people, is surprisingly easy to collimate (with Catseye tools) and holds collimation well and having used a 6" Starfire APO (the worlds finest refractor) to image with at F8, data acquisition speed is streets ahead and under good seeing conditions, the resolution is better :)

Now back to that piece of string, thing is...... :question:

Mike

[Slawomir]

AG12 is on special offer at the moment... about 15% discount at Orion Optics! :)

[strongmanmike]

Indeed, a good time to buy I guess?

After thoroughly enjoying the AG12 for 4 years now, I wanna try one of OO's ODK's now (long focal length envy :P)...so who knows? :)

Mike

[ausastronomer]

I think this is a very old fashioned approach and shows some narrow-mindedness and naivety in regard to modern Newtonian telescope design, construction and performance.

I don't particularly like Newtonians faster than F4, for a whole range of reasons, the main one being the fact that I have seen more poor quality sub F4 mirrors, than I have seen decent ones and these have all been from reputable US opticians. Myself and a large number of other observers share the view that some of their best lunar and planetary views have been in medium to large aperture Newtonians ranging in size from 12" to 20" and in F ratio from F4 to F6.

I have used all types of telescopes including Maks (Questar, Quantum, Intes & Intes Micro) ; countless SCT's from both Meade and Celestron, some of the best refractors money can buy up to 15" aperture (AP, Takahashi, TMB, Televue, TEC and D & G) and countless Newtonians ranging in quality from abysmal to exceptional in in aperture from 3" to 36" and in F-ratio from F3 to F12.

My best lunar and planetary views have come in my own 18"/F4.5 Obsession (OMI mirror) , my own 14"/F4.5 SDM (Zambuto Mirror) and James Pierce's 16"/F4 SDM (Lockwood Mirror). The problem is for a Newtonian to deliver its best images everything has to come together all at the same time. The scope has to be well built, it has to be properly cooled and collimated and the seeing has to be very good as large aperture scopes are more severely affected by poor seeing than small aperture scopes. To get a medium to large aperture fast Newtonian to properly strut its stuff takes some know how and patience, which many people that own them can't accommodate because they don't have the know how, patience, or both. Unfortunately 90% of Newtonians on the field at public star parties are poorly set up and will not be capable of delivering top quality high power views because of a combination of poor set up, poor collimation and inadequate cooling and air circulation.

When you get a newtonian in the 12" to 20" class that has a high quality thin mirror (faster cooling), in a good telescope structure with a good mirror cell that is properly collimated under excellent seeing, it will deliver better high power views by virtue of its greater aperture, hence greater resolution, than a smaller telescope of a different design.

An 18" AP refractor would undoubtedly give slightly superior views to my 18" Obsession under the same conditions, but unfortunately Roland isn't making them at the moment and I couldn't afford one if he was.

Cheers
John B

[ausastronomer]

Hi Greg,

Having used telescopes of all designs from 2" aperture to 36" aperture and from F3 to F16 in F-ratio, if I could only have one telescope for visual astronomy it would be a high quality Newtonian of 12" to 16" aperture and about F4.5 in F-ratio. This to me is the perfect compromise between visual performance and storability and transportability. I am yet to use a better "all round visual telescope" than my 14"/F4.5 SDM. It is a high quality product with a Zambuto mirror, Feathertouch Focuser, Servocat and Argo Navis. Set up as such they aren't cheap compared to the mass produced scopes (about $15K) but they give exceptional all round performance with accurate GOTO and tracking and high quality optics and functionality.

I am not an imager but one of my favourite scopes which I am sure would work very well for a large number of imaging chores is the Takahashi TOA 130. Excellent small aperture visual telescope which I am sure is a great imaging scope as well.

Cheers,
John B

[Peter Ward]

I think they are still being made...hence replaceable ...that said...as an imaging machine..it's like using a really short tubed, perfectly corrected 12" APO.....and is without doubt, one of he finest imaging 'scopes I've had the pleasure of using.

Visually that big secondary is noticeable...hence to be fair, it doesn't fit the "all rounder" moniker quite so well...

To add to my woes it won't be able to live in the dome with the new Alluna (simply not enough room). Bugger. :)

[ausastronomer]

This is another important aspect of visual performance and Newtonians that Peter has highlighted here. For a Newtonian to deliver high quality high power views it needs a small secondary obstruction. Typically it needs to be under 20%. The MTF curves show that a scope with a <20% central obstruction (regardless of design) has close optical performance to an unobstructed scope. The AG 12 has a CO over 30% as do most SCT's and MCT's.

Cheers,
John B

[gregbradley]

Oh the problems of the rich!

Greg.

[multiweb]

Well... if it's ever going to burn, let me know. I'll pick it up for you. No drama. :thumbsup:

[Shiraz]

bit out of left field, but has anyone used a Skywatcher 190/f5.3 Mak Newt?

By all accounts these perform visually like a very big APO (small central obstruction and no aberrations to speak of). The aperture is probably large enough to pull in a range of the brighter DSOs. For imaging, they have enough aperture to provide seeing-limited resolution (with small pixels) and have a short enough fl and are inherently well enough corrected, to provide a fairly wide flat field with a large camera or DSLR.

The downsides might be that they are heavy and that viewing may be inconvenient on an EQ mount. Also, Skywatcher's QC sometimes seems to be a bit iffy - but their optics are pretty good and, fitted with a decent focuser, this could be a useful choice as an all-rounder. Of course these scopes would lack mystique, bragging rights and premium build quality (= pleasure of ownership), but if they work OK....

Does anyone have any experience with one of these? - would this design meet Greg's criteria?

[sn1987a]

I'm quite enjoying the amenity of my 20" f4 Ultralight at the moment actually. A lovely Zambuto mirror 2" thick. Cooldown time is practically straight away and coupled with TV wide angle eyepieces the views are superb. Jupiter the other night was the best I've seen it. Setup/teardown time is in minutes. At f4 most of the time I'm standing on the ground with only an occasional hop up near zenith. No Argo or Servocat (yet). 12v hairdryer sometimes required :D.

[Clancy Lane]

Ray,

I have owned both the Orion and Sky watcher versions of this wonderful scope and absolutely agree with your assessment.

The views were amazing compared to my 10" and 12" Newts and even though my Meade 127 Apo gave crisp, clear views, the Mak-newt left it for dead.

Viewing was even better using WO binoviewers!

Imaging thru these scopes, even with the stock focuser but utilising an electric focuser, was also excellent.

Both scopes were reluctantly sold due to my advancing years and declining health.

I now use a TSA120 but miss the versitality of the Mak Newt configuration.

cheers,

Phil

[rustigsmed]

g'day phil

what's the go with collimation with the mak-newt? is it hard to do? and is it even required?

cheers

rusty

[raymo]

My scope of choice would be a Mak, and given my age it would
unfortunately be limited to a 10". I've just started my 63rd year of
owning and/or using scopes, and have enjoyed my 150 and 180mm
Maks more than any other scope I've owned. I've never owned anything
really large, a 17 1/2" Dob being the largest.
raymo

[Clancy Lane]

Russell,

I did a lot of experimenting with different collimation methods, including lasers, but found the best way to collimate these Mak Newts was with a long Cheshire and the extension tube pulled right out as far as it will go.

This will give you a much better view to see if the focuser is correctly placed over the secondary mirror.

There are so many circles in the view but once things become clear in your mind as to what goes where, it becomes easier. (there is a faint circle on the secondary)

The hardest part was centering the focuser over the secondary correctly - it took a bit of persuasion.

It was very easy to see in your images if the collimation was correct - star colours would be even around the star instead of off to one side.

If contemplating buying one of these scopes (even brand new)please make sure it is the latest model and not the earlier with single speed focuser.

Hope this helps!

regards,

Phil

[dannat]

for visual i would think something like an acf/edge 8"..reasonable price, easy to mount/transport
big refractors give great star views but are heavy/expensive not that portable

[wavelandscott]

Sorry to be late in my in adding my comments. I agree with John's take on this...12-16 inch reflector (properly cooled and collimated is tough to beat visually. However, I will concede that portability for some might be an issue.

There are a few 130 mm (or so refractors) that I could also suggest fit that "sweet spot"...not too big and not too small

Cheers,

[gregbradley]

Personally I am leaning the discussion more towards imaging rather than visual.

I guess visual large Dobs are hard to beat.

Imaging with a high end APO is hard to beat. Perhaps the AP RHA is the current king - not sure. Certainly for wider field.

Greg.

[Hans Tucker]

A proponent of the Officina Stellare brand might disagree.

[Peter Ward]

They might, but it still won't make it an AP. :D

[clive milne]

If equatorial mounts were sold for free then nothing would beat a Newtonian dollar for dollar. Being that they are not, the equation slews more towards the RC and corrected DK designs.
If narrow band imaging is the intent then the fastest focal ratio wins.

Refractors are unchallenged up to 4" of aperture, but pretty much untennable (from a cost/performance basis) beyond a 6" objective.

[Hans Tucker]

I'm a bit sour towards AP...I checked their website and it looks like Roland has dropped the 12" f12.5 Maksutov-Cassegrain from his product line....looks like his focus is on the 12" f3.8 Riccardi-Honders Astrograph.

[Slawomir]

Perhaps then this one might be quite close to being 'ideal', at least in terms of value for money?
http://www.bintel.com.au/Telescopes/Cassegrain/Bintel-GSO-RC12-A-f/8-Astrograph/1957/productview.aspx

[Stefan Buda]

The Busack-Riccardi-Honders formula is the only 21st century design when it comes to amateur astrographs , and as such, not many people have used them yet. I think this design will grow in popularity due to its ultra compactness and excellent corrections. Once the Far East manufacturers start making them, the price should come down a lot because the design is rather simple.

I totally disagree with Maksutov lovers: Maks are the ultimate good for everything but excellent for nothing scope. They suffer from severe thermal problems. For those who disagree, let me tell them that planetary observing is not done at 150x - try 400x and more.

[gregbradley]

OS RHA you mean? I like the extensive use of carbon fibre on the OS range. I also notice the 10 inch RHA is now F5.6. Perhaps F3 was over optimistic and the requirement for perfection on the mechnicals was an issue. Bert had all sorts of rigs and stuff to correct flex on his etc. Mind you has was overloading it beyond its specification. Roland and Massimo worked together when making the AP RHA. So it has Massimo's optical genius coupled with Roland's optical genius but also Roland's decades worth of engineering excellence and quest for perfection. The difference is Roland makes the scopes, I don't think Massimo does, he designs them. Correct me if I am wrong. F3.8 is still very very fast but probably that little bit more workable. The Tak Epsilon F2.8 is famous for being difficult to collimate. So F3 is adventurous.

That is a huge difference. Also compared to other scopes I have used, you can tell Roland has done a lot of imaging and that know how ends up in the scopes. So I have never heard of flexure issues with focusers made by AP yet I have with every other brand. The AP RHA does not require collimation as well, a big plus. The mirror coating is on the rear side of the glass so it can't degrade, another big plus.

That attention to detail and the obvious standard that there is no compromise on quality is what makes them special.

I don't know the Mak Cass is not going to be made. There was a prototype 12 inch one a few years back. It may be a lot of work tooling up to make all these different models and you'd have to get a return on the Honders investment first. I am sure it took a lot of tooling up.


Anyway its all speculation. Why don't you ask Roland direct on the AP Yahoo Group. He's likely to answer you.

Greg.

[Alchemy]

RE ......AP RHA

Given F3.8 is the ratio of FL to width, which in refractors does give some comparison, but given the central obstruction and the interest in light gathering capability..... What is the central obstruction diameter and therefore the percentage variation in collecting ability in comparison to a refractor of equal dimensions and FL .....

Just trying to get an idea of its photon gathering capability, might be similar to F5 in a refractor.

[clive milne]

F4.38 or there abouts.

[gregbradley]

I've done those types of calculations before. Because the radius is squared and multiplied by Pi 3.142 you get a rapid increase in area when you go up in aperture.

So say compare the RHA at 305mm and 150mm secondary at F3.8:

http://www.astro-physics.com/index.htm?products/products

to FSQ106ED F5

You get 55,397 mm2 area in the RHA after subtracting the secondary area compared to
FSQ106 8825mm2.

When you consider F stops represent a doubling of light you get F stops:

F2.8 F4 F5.6

F3.8 to F5 then looks to be around 1 F stop = doubling of light.

So 55,397 of the RHA divided by 8825 of the FSQ = 6.2 times.

Now with the F stops I think you double this = 12.4 times the light gathering ability of an FSQ106.

Then factor in various CCDs and their different QE's although most are between 50% and 77% unless you use one shot colour and that goes down to 25%. The Sony 694, 814 and the new 12mp sensors are all 77% QE with 5 electrons or better read ( 3 electrons with the 12mp as smaller pixels means lower read noise).

A 180mm APO is 25,420 mm2 so that is about 45% of the RHA but again F7 versus F3.8 is now closer to 2 stops.

So the maths is very significant. You can't beat aperture and you can't beat fast F ratios when time is limited.

I must say I am impressed by the quality of many of the 8300, 694, 814 sensored camera images taken on small high quality APOs. There are many of these images on this site.

A small CCD on a small aperture with good optics is still an excellent setup and a way to get detail on smaller object.

Greg.

[Alchemy]

Hard to argue raw numbers, plus 1159 mm focal length still gives you good imaging for most nights.
Must say I definitely like The idea of the reflective surface on the rear of the glass, although the effects of the glass needed to be factored into the optical train ( how thick is rear element ) , the idea of a surface that never needs recoating is brilliant, plus never needing collimating also brilliant. Hard to find a problem with it so far. At a shade over 30 kg it will need a solid mount, plus might take a while for thermal equilibrium, although specs say it barely shifts due to temperature.

Is it the perfect scope for imaging ...... Not if you're on a mountain top in the desert, but for everyday use, it's got a lot going for it.

Look forward to the results.

[Stefan Buda]

Spot on Clive! Half a stop extra for 50% central obstruction.