Reflector or APO refractor for viewing solar system?

[andy435]

To start exploring the solar system mainly the planets, moon and maybe the biggest DSO. I've narrowed it down to two telescopes based on what I've read and what I've been recommended. First is the Skywatcher Evostar 80ED and a second is the Skywatcher 130PDS.

- Evostar: Portable, needs no collimation (easy with laser anyway), can be used for imaging later (not a priority) but collect less light and is more expensive.
- The 130PDS: collects more light, less portable, needs collamination

The telescopes will be used with an alt az mount Vixen Porta II or the Skywatcher AZ4 (not decided yet).

What would you choose and why?

[Moonshane]

Out of these two I'd go for the 130 PDS. It has more aperture, is faster and also can be and is used for imaging. More aperture = more resolution and faster = more data in a given time. To image you will need a coma corrector for the newtonian and a field flattener / reducer for the refractor and a good EQ mount. 

That said, both would be very good and both would work well on the objects stated and for the purpose planned.

Both can be used for white light solar with a suitable filter over the front end.

 

[mikeDnight]

The 130 will definitely have an advantage over the 80 with regard to dso's! 

When it comes to the planet's, the 80ED will give you very sharp images, which helps greatly in detecting planetary detail, and which can prove more advantageous than increased resolution at times. 

The ED's are very very good scopes! I bought a Equinox 80ED just over two years ago and it amazed me at just how well it performed on the moon and planets. As it was such an easy scope to use and carry about, I would nip out with it for just a five minute session and find myself still observing over an hour later. It regularly showed five belts on Jupiter as well as the great red spot hollow, and the red spot itself, as well as shadow transits. Cassini's division in Saturn's rings was easy and the Moon will knock you bandy! I didn't get to use it for viewing Mars but I know from past experience that a 80mm scope is more than capable of revealing significant albedo features, as well as the polar cap and clouds. If all I had was an ED80, I'd be very happy! I'm not sure I'd feel the same way about the 130 reflector!

Really its what suits the observer! The 130 will offer brighter images and many observers like this quality in a telescope. The ED will be sharper, and that's where its power lies. Each to their own!

With regard to the mount, I've owned both the porta ll and the AZ4. Many people like the porta but mine and every other porta and porta ll that I've used has had the damping time of a tuning fork. The AZ4's, though lacking slow motion controls, is a far more solid option in my view. 

Mike

 

 

[Peter Drew]

If your main interest currently are the Moon and planets I would go for a 6"F8 Dobsonian rather than the ones you've mentioned. It would give better resolution and higher magnifications and could also be used for lunar and planetary imaging. I think the other choices you are considering are best suited to imaging in the future. 

[andy435]

Thanks you! Magnification is relative but what magnification can I expect from the two whitout loosing too much details.

I'm looking at at FOV simulator to get a idea of what to expect. If the FOV simulator is somewhat correct the difference is not that big between the two telescopes.

[Moonshane]

usually I work on 1x-2x aperture in mm so between 80-160x for the 80mm ed and 130-260x for the newt. That said, the sky conditions usually dictate the max magnification which in both cases is more likely to be around 150-200x on average. the environment in which you observe matters too, as heating plumes in winter and hot rooftops in summer has an effect.

[ollypenrice]

For me 80mm is a bit small for visual unless you're wanting a widefield scope and you're not. I'm a great refractor fan but even so... on reflection I'd reflect this time!

Olly

[Ruud]

The 80 mm has too low a maximum magnification. Where it about gives up, the 130mm is right in the middle of its comfort zone.

I have a Porta II. It's a bit of a disappointment but it may carry an 80mm well. The SW alt az 4 is probably much better. Its round, steel legs are definitely better than Porta's flat aluminium legs.

Have you considered a 150 mm Maksutov as your planetary telescope? The tiny secondary of a Mak makes for good contrast in the smallest details.

[andy435]

Funny you said that just looking at the MAK now but the 127mm

I would line to hear more about MAK how does it compare to Newt?

[ronin]

I always get a bit uncomfortable when someone says "viewing solar system".  Reason is there is not a great deal of it to view.

Jupiter - in about 3 months, Saturn in about 6 to 8 months, Mars next year sometime (and you will need bigger then either scope for Mars). After those planets that really is it. Venus is a fuzzy cresent, Neptune and Uranus too far away so very bim green/blue star like.

Which leaves the Sun. On the basis that that is often around, good for standing outside in the summer under a clear blue sky (OK we are in the UK but imagine it). I would opt for the ED80. It will have enough to show Jupiter and Saturn, and clearly, and you can fit a herschel wedge and continium filter for the Sun.

The aspect of the ED 80 is that it may not be the biggest diameter or the greatest magnification but it can do a lot of things very well.

[Ruud]

Maks ate slow scopes. Their focal length is very long compared to the aperture. Often 11 to 15 times longer (f/11 to f/15). In practice, this means a relatively narrow true view at a high magnifications. 

Newtonians are often as fast as f/5, giving a relatively wide view of the sky at lower magnifications.

A 6" f/8 dob is somewhere in the middle. That's a nice all round instrument with a smallish secondary. Not as small as a Mak's secondary though.

If I had no telescope and if I were on a budget I'd go for a 6"' f/8 dob as a good all rounder. If I were really into planetary and lunar observation I'd want a Mak, and if I were really into deep space I'd get a faster dob (probably the ubiquitous 8" f/6).

When telescopes get faster they require better eyepieces (read more expensive) for maximum performance. When Newtonians/dobs get faster they'll have more coma (an off axis distortion) and a bigger secondary leading to loss of contrast.

--> Whatever you get, don't get a Bird Jones! <--

[Louis D]

9 hours ago, Ruud said:

A 6" f/8 dob is somewhere in the middle. That's a nice all round instrument with a smallish secondary. Not as small as a Mak's secondary though.

Um, maybe for a Mak-Newt they're equivalent, but definitely not for a Mak-Cass.  Both the 6" f/8 variations of the Newt would have a 15% to 20% central obstruction (CO) by diameter, depending on the focuser height and desired circle of illumination.  The Mak-Cass would be somewhat over 30% CO by diameter owing to the greatly folded light path.  An f/11 to f/15 Mak-Newt (if such a thing existed) would have a very small CO indeed, but I don't think that's what you were referring to.  The f/11 to f/15 Newt would also have the same sized CO.

[Dave In Vermont]

As Mike so well described the vibration-problems with these mounts:

"With regard to the mount, I've owned both the porta ll and the AZ4. Many people like the porta but mine and every other porta and porta ll that I've used has had the damping time of a tuning fork. The AZ4's, though lacking slow motion controls, is a far more solid option in my view.

Mike"  

Now in this following thread, I addressed this very issue:

          

 

 I hope some folks out there give this a try - including you, Mike!

It's rather distracting to have your great views spoiled by a mount that thinks it's competing in a dancing-contest.....

Have fun - not frustration!

Dave - it's snowing here.

 

[jetstream]

1 hour ago, Louis D said:

Um, maybe for a Mak-Newt they're equivalent, but definitely not for a Mak-Cass.  Both the 6" f/8 variations of the Newt would have a 15% to 20% central obstruction (CO) by diameter, depending on the focuser height and desired circle of illumination.  The Mak-Cass would be somewhat over 30% CO by diameter owing to the greatly folded light path.  An f/11 to f/15 Mak-Newt (if such a thing existed) would have a very small CO indeed, but I don't think that's what you were referring to.  The f/11 to f/15 Newt would also have the same sized CO.

I think that the 6" f8 newt will run about 23% (Orion USA) and a Mak Cass can run a very similar if not the same central obstruction. The ones I looked up seem to run 30% however... but then there's the Astro Physics.

http://www.lcas-astronomy.org/articles/display.php?filename=schmidt-cassegrain_and_maksutov-cassegrain&category=telescopes

http://www.astro-physics.com/index.htm?products/telescopes/10mak/10f146mak

 

[jetstream]

DOB!

My vote for the telescope goes to a 200mm f6 SW dob which is a very flexible scope in terms of eyepieces and observable objects. The resolution on the planets/moon will be VG and the stability of the mount is well known (excellent).

[Alan64]

Hello Andy,

"The telescopes will be used with an alt az mount Vixen Porta II or the Skywatcher AZ4 (not decided yet)."

The AZ4 mount will support the Sky-Watcher 150P-DS, 150mm f/5, if you'd like the extra aperture...

That telescope, incidentally, is Bresser's 150mm f/5.

I have a 150mm f/5 Newtonian, and most often mounted on a alt-azimuth mount of a similar build as that of the AZ4...

It's a good-sized telescope, but probably not as large as you might think at first, and with a standard table salt-shaker alongside to illustrate...

I've found a 150mm f/5 Newtonian to be a great all-around telescope, with magnifications ranging from 19x, to 250x and beyond with the aid of 2x and 3x barlows, and for observing virtually everything in the sky; the gamut.

Once collimation of a Newtonian is learned and mastered, and fairly quickly, it becomes quite the proverbial piece of cake.  Once collimated properly, the telescope would require only very minor adjustments on occasion.  It's the initial learning and mastering of the process that puts many people off, but after a time you would look back and wonder as to why people don't consider a Newtonian more often. 

The 150P-DS comes equipped with a metal 2" two-speed focusser, just as the 130P-DS; for a more precise focus, and in realising any given object at its sharpest.

As to the optical quality, I sometimes take afocal photographs of a few objects, and simply by holding a small camera of sorts up to the eyepiece and snapping a shot, on the fly...

My 150mm f/5 arrived as this, and as the Orion StarBlast 6...

...and a blast it has been indeed.

[michael.h.f.wilkinson]

I used to have an 8" F/6 with a small central obstruction (24% or so, smaller that the 33% of the SkyMax 127, larger Mak Cas scopes tend to have smaller CO), and it was really great on planets, and did well on DSOs. Aperture is king however, and my 8" SCT  beats it in detail seen (at a slight loss of contrast atthe same exit pupil). The 8" F/6 dob mentioned is a great all-round performer, but might be a bit big. BTW, the SkyMax 127 is and excellent performer on planets by all accounts

[alanjgreen]

I'm with Ronin on this one. There is not very much to see in the solar system on the nights we get outside. You may get 1 big planet and 1 small planet if you're lucky.

the moon may be out.

i would look to get a 6" or 8" inch scope (bigger is better)

6" could be a 150 newt or a dob

8" would have to be a dob

i am guessing your budget is limited.

with larger diameter you can get into the DSO and there are plenty of them all year around.

you could also think about double stars, they are there all the time and can be fun to split.

jupiter and Saturn are entertaining on the rare occasions that they are (1) in the sky (2) higher up so the earths atmosphere is not interfering with the view. This can happen every few years!

Alan

[Louis D]

9 hours ago, jetstream said:

I think that the 6" f8 newt will run about 23% (Orion USA) and a Mak Cass can run a very similar if not the same central obstruction. The ones I looked up seem to run 30% however... but then there's the Astro Physics.

http://www.lcas-astronomy.org/articles/display.php?filename=schmidt-cassegrain_and_maksutov-cassegrain&category=telescopes

http://www.astro-physics.com/index.htm?products/telescopes/10mak/10f146mak

 

Indeed, specialized Mak-Cass designs can have a smaller CO if only a smaller field of view is desired.  If you read about the CO in the AP Mak-Cass, you'll note that they don't recommend using wide FOV 2" eyepieces unless you also use their optional 32% CO baffle to prevent stray light from entering the eyepiece directly from the corrector.  This is not an issue with a 23% CO Newt or Mak-Newt.  Thus, this isn't really an all purpose scope.  In my newt, I have a low profile focuser so I can get away with an 18% CO to further improve contrast.  I've never noticed any vignetting visually even in my 40mm Meade SWA 5000, so I think it was a good compromise.

Basically, there's no free lunch when it comes to portability and standard mirror designs.  If you fold the light path to make a scope more compact, there will be compromises in either the field of view or contrast.  That's probably why I see so many folks online and at star parties mounting a short focal length ED or APO refractor next to either an SCT or Mak-Cass.  That way, you get the best of both worlds.

[jetstream]

38 minutes ago, Louis D said:

Indeed, specialized Mak-Cass designs can have a smaller CO if only a smaller field of view is desired.  If you read about the CO in the AP Mak-Cass, you'll note that they don't recommend using wide FOV 2" eyepieces unless you also use their optional 32% CO baffle to prevent stray light from entering the eyepiece directly from the corrector.  This is not an issue with a 23% CO Newt or Mak-Newt.  Thus, this isn't really an all purpose scope.  In my newt, I have a low profile focuser so I can get away with an 18% CO to further improve contrast.  I've never noticed any vignetting visually even in my 40mm Meade SWA 5000, so I think it was a good compromise.

Basically, there's no free lunch when it comes to portability and standard mirror designs.  If you fold the light path to make a scope more compact, there will be compromises in either the field of view or contrast.  That's probably why I see so many folks online and at star parties mounting a short focal length ED or APO refractor next to either an SCT or Mak-Cass.  That way, you get the best of both worlds.

I love newts

My 15" runs about 20.5% and with a very nice illuminated field.