Reflector or Refractor ?

[Golfox2]

Hello guys, I may have found exactly the forum I need here 

I would be really glad if you could help me a bit please : I love stargazing on the mountain next to home (low light pollution), but now I want to level up. I mean, I'd like to use a device that is better than my eye to see the night sky.
The problem is I am quite lost between telescopes, lenses, reflectors, refractors, and hybrids devices etc. 
So here I am, coming for your advice that will be, I am sure, of great help.

Here's my question : what device is best suited for my use ? 
I'd like to see constellations and close deep sky like big galaxies (andromeda M31 for example). I am aware that refractor lenses are less bright than reflexion telescopes but I'm not certain which one to buy.

> The main purpose would be a looking through device, but ideally if I can plug my Canon DSLR it would be fantastic.

What are best brands for an amateur ?
I prefer to pay more but once than cheap but twice and have a budget of around 250-300 € (if one is a bit above but really effective I can go a higher).

Thank you a lot in advance for your time and advice !

Golfox2

[Stu]

Welcome to the forum Golfox2.

Your question is a very broad one, and quite difficult to answer without knowing your preferences. I shall make some assumptions though. It seems like you have good conditions near or at your home so the size of scope is not an issue.

The standard suggestion, and one that is perfectly valid, would be an 8" Dobsonian reflector such as the Skywatcher 200p. This would show you excellent views of a wide range of objects both in the solar system and deep sky objects such as galaxies etc.

https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-200p-dobsonian.html

The limitations? Well it is totally manual so you would need to find objects yourself. This should be something which is fun to learn and part of enjoying the hobby so not in itself a problem. Under dark skies, finding objects should be relatively easy.

The mount also does not track the stars as the earth rotates so you have to nudge it back into position quite frequently (less so at low powers, often at high powers)

This scope would be at the higher end of your budget, and you may want to leave some available for a couple of additional eyepieces so the 150P is also worth considering.

https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-150p-dobsonian.html

Finally, visual astronomy and astro photography have very different requirements. Yes, you could attach a camera to either of these scopes and take short exposures of bright objects with moderate success, mainly the moon and planets. To do deep sky photography you need multiple long exposures and an Equatorial mount to track the stars. It is beyond the budget you have available generally so I would suggest focusing on the visual side for now.

[Cosmic Geoff]

Since you are starting from zero, I would suggest that you get a small, portable telescope outfit from a well-known brand (Celestron, Sky-watcher, Bresser) and see how you get on with it. Your modest budget will not run to anything more. You will get widely varying advice about what to buy, and to a large degree it matters less what exactly you buy (so long as it isn't rubbish) than that you buy something and see if it's the kind of thing you like.

Serious astro-photography will be beyond your budget.

With experience, you may find that you don't like manual telescopes (including Dobsonians) because you can't find anything, or conversely that you can't master the detailed set-up of a GoTo.  Or that you like the simplicity of an alt-azimuth mount over the tracking ability of an equatorial. But you won't know till you have given it a go. You can always re-purpose your first instrument or sell it on.

I would suggest that you contact a local astronomical society if at all possible and see what you can learn from them. 

I re-started a serious interest in amateur astronomy with a  supermarket 70/700mm refractor (too cheap, too frustrating) and then a small Maksutov on a portable GoTo mount. I have never regretted the latter and still use it.

[Golfox2]

Thanks for your answers guys.

So @Stu, I'll probably get a shot on one of the two dobsonians you mentioned. You told it's fully manual, but what are alternative options ?
what is considered automatic or "non-manual" and what does it do ?
as Cosmic Geoff said, I could go with a GoTo device to track objects for multiple exposures instad of fully manual scope ?

And @Cosmic Geoff, I guess a 2kg scope from Bresser would be fine ? like this one :
http://www.astroshop.eu/bresser-maksutov-telescope-mc-100-1400-eq-3/p,54021#tab_bar_0_select

I don't mean to do serious astrophoto, only a few pictures time to time, the main purpose is see through.

Am I right assuming a GoTo is an object tracker ? Would it be better to buy this Bresser scope + a separate goto mount instead of the tripod ?
And I'm not sure about differences between alt-azimuth and equatorial mount :s

Thanks !

[MarsG76]

I recommend the Celestron NexStar 8SE.

It has great optics, I had some amazing views through it and it's GOTO. 

[Cosmic Geoff]

56 minutes ago, Golfox2 said:

as Cosmic Geoff said, I could go with a GoTo device to track objects for multiple exposures instad of fully manual scope ?

I suggest some reading about what a GoTo does.   They all track, but their primary function is to find things. The alt-azimuth versions are not suited for long exposures as the field of view slowly rotates. (With an equatorial it doesn't, but we get a lot of posts here asking how to set up an equatorial GoTo mount. Clearly they are not so simple to use.).

The Bresser Mak looks okay (if you want that kind of mount). As far as I know, nobody ever complains about buying a bad Maksutov.  You can buy GoTo mounts separately (some models) but it is usually cheaper to get a complete scope & GoTo mount package.

[Ben the Ignorant]

2 hours ago, Golfox2 said:

 I am aware that refractor lenses are less bright than reflexion telescopes

It's not that refractors are less bright than reflectors, but reflectors are easier and cheaper to make in large sizes that collect a lot of light. Diameter being equal, a 130mm lens is brighter than a 130mm mirror system because the reflective side of mirrors absorbs several percents of the light, and the secondary is always in the light path, absorbing incoming light with its back, and not reflecting it all with its reflective surface.

The light loss in a double or triple lens is only two or three percent, some is lost to slight reflection on surfaces, some is absorbed by the glass, but no obstacles in the light path worsen the loss. The absence of objects inside the tube means contrast will be greater, too. Lastly, the least expensive 130mm apo costs 1,900€, but my clearance 130mm newtonian tube - with very fine optics - costed 85€!

Thus the light loss can be forgiven. 

[Stu]

47 minutes ago, MarsG76 said:

I recommend the Celestron NexStar 8SE.

It has great optics, I had some amazing views through it and it's GOTO. 

It's a very fine scope, but completely outside the budget range identified by the OP

[Golfox2]

Okay nice, thanks Geoff

So I should narrow down to a scope & GoTo mount pack.
After some reads, I understand now how alt-az and equatorial mounts work, and my go for an alt-az then (for now).
Can I mount a GoTo on an alt-az ? (maybe only for pointing, not for tracking)

Hum, thanks Mars, but it's a bit expensive for me, but thanks anyway =)

 

@Ben : oh, thanks, I didn't know that, and seems clearly logical after explanation !
What is the model of your newtonian tube please ?

[Ben the Ignorant]

https://www.teleskop-express.de/shop/product_info.php/info/p4778_Skywatcher-Explorer-130---130-900-mm-Newton---optischer-Tubus.html

It's this one, except I got mine when the price was halved for some reason.

[Golfox2]

25 minutes ago, Ben the Ignorant said:

https://www.teleskop-express.de/shop/product_info.php/info/p4778_Skywatcher-Explorer-130---130-900-mm-Newton---optischer-Tubus.html

It's this one, except I got mine when the price was halved for some reason.

Nice !! It seems perfect for my use, may I know what mount it is on please ? do you use a GoTo and alt-az or EQ ?

And I've read that Newtonians scopes have a con : coma. I understand it is a loss of quality on the side of the field of view, am I right ? Is it annoying or not ?

[Louis D]

3 hours ago, Golfox2 said:

I love stargazing on the mountain next to home (low light pollution)

I have to ask, can you drive up this mountain to your observing spot or must you hike in?  If you must hike in, then weight and bulk will play a major role in your choice of telescope.  A goto will require power.  That equals more weight and bulk to haul in.  If you want to pack light, I'd recommend something like the Skywatcher Heritage-130p Flextube.  That would leave you plenty of money for accessories like eyepieces, collimation tools, astro books/charts/planisphere, red flashlight, etc.  If you want to move up to something bigger, you'll always have it for camping trips when space is an issue.

[Louis D]

3 minutes ago, Golfox2 said:

Nice !! It seems perfect for my use, may I know what mount it is on please ? do you use a GoTo and alt-az or EQ ?

And I've read that Newtonians scopes have a con : coma. I understand it is a loss of quality on the side of the field of view, am I right ? Is it annoying or not ?

It is sold as a bare OTA.  You have to supply the mount.  A lot of folks already have mounts and don't need another, so telescopes can often be bought without them.

Coma isn't an issue for most beginners.  Low cost eyepieces have enough edge of field astigmatism to drown out any coma that would be seen there.

[Golfox2]

Thanks Louis D !
I can drive up with a car yes, so volume/weight is not my first problem, but the most compact, the most convenient for me it is for sure
Wow the heritage 130p seems really convenient, but does it have a good quality for star seeing ? it looks really cheap...
And I may think I would prefer knobs for controlling my axis of rotation instead of a plate.

[Louis D]

50 minutes ago, Ben the Ignorant said:

It's not that refractors are less bright than reflectors, but reflectors are easier and cheaper to make in large sizes that collect a lot of light. Diameter being equal, a 130mm lens is brighter than a 130mm mirror system because the reflective side of mirrors absorbs several percents of the light, and the secondary is always in the light path, absorbing incoming light with its back, and not reflecting it all with its reflective surface.

The light loss in a double or triple lens is only two or three percent, some is lost to slight reflection on surfaces, some is absorbed by the glass, but no obstacles in the light path worsen the loss. The absence of objects inside the tube means contrast will be greater, too. Lastly, the least expensive 130mm apo costs 1,900€, but my clearance 130mm newtonian tube - with very fine optics - costed 85€!

Thus the light loss can be forgiven. 

The human eye needs about a 15% light loss IIRC to be perceivable.  Modern reflective coatings will come close to keeping things in this range.  High end reflective coatings can keep losses well below 10%.  More important is that they need to be very smooth to minimize scatter to improve contrast.  That's why silver coated or even glass prism diagonals are usually judged to be better than dielectric prisms.  Dielectric coatings just aren't as microscopically smooth as silver and polished glass.

Refractors excel at contrast because they don't throw any light into the outer diffraction rings like an obstructed design.  Of course, you can always start with a 16" reflector and use an off axis mask to get an unobstructed 6 to 7 inch system.  DGM optics makes somewhat smaller unobstructed reflectors in Teeter built scopes.  Less bulk, but similar in price.

[John]

4 minutes ago, Golfox2 said:

Thanks Louis D !
I can drive up with a car yes, so volume/weight is not my first problem, but the most compact, the most convenient for me it is for sure
Wow the heritage 130p seems really convenient, but does it have a good quality for star seeing ? it looks really cheap...
And I may think I would prefer knobs for controlling my axis of rotation instead of a plate.

The mirrors are good quality in Skywatcher scopes. I've owned and used them up to 12" in aperture and they always seem to perform as well as anything of the aperture can.

The challenge with a budget of £300 or so, if you decide that you want a GOTO mount, is that much of the budget goes on the mount and proportionately less on the scope optics.

Something like this seems to offer decent aperture and the GOTO facility but it's slightly over your budget:

https://www.firstlightoptics.com/az-goto/sky-watcher-star-discovery-150p.html

[Louis D]

2 minutes ago, Golfox2 said:

Thanks Louis D !
I can drive up with a car yes, so volume/weight is not my first problem, but the most compact, the most convenient for me it is for sure
Wow the heritage 130p seems really convenient, but does it have a good quality for star seeing ? it looks really cheap...
And I may think I would prefer knobs for controlling my axis of rotation instead of a plate.

By all accounts, it has optics as good as the typical commercial 130mm, 150mm, and 200mm offerings.  As long as it's a parabolic rather than spherical mirror, you shouldn't have any issues.  The only thing most people add to it is a light shroud made from some sort of stiff material to keep stray light from getting to the mirrors once it's extended.

Moving an alt/az Dobsonian mounted scope in two axes quickly becomes second nature.  It's only a pain if you have to share the views.  Using knobs on a cheap EQ mount can be a pain because of settling time each time you move the tube.  Dobsonian mounts tend to be much more stable and settle very quickly.  With the best ones, you can keep a light touch them at all times without introducing vibrations.

[Ben the Ignorant]

35 minutes ago, Golfox2 said:

Nice !! It seems perfect for my use, may I know what mount it is on please ? do you use a GoTo and alt-az or EQ ?

And I've read that Newtonians scopes have a con : coma. I understand it is a loss of quality on the side of the field of view, am I right ? Is it annoying or not ?

It rests on this mount, which is currently sold at a slashed price, too:

https://www.teleskop-express.de/shop/product_info.php/info/p8136_TS-Optics-Parallaktische-Montierung-EQ4-mit-Polsucher-und-Stativ.html

It's a manual EQ, I never use GoTo. The looks are not as refined as in a Sky-Watcher EQ-3 or EQ-5 but the motions are smooth, and the head is 10cm lower than an EQ-3 head. It's a plus or a minus depending on your personal ergonomics.

Coma is reduced when the f/ratio is smaller, thus that f/7 has no coma to speak of relative to my f/5 dobsonian, which doesn't display too much coma either, thanks to quality eyepieces that keep the stars tight enough over the whole field.

[Ben the Ignorant]

30 minutes ago, Louis D said:

The human eye needs about a 15% light loss IIRC to be perceivable.  Modern reflective coatings will come close to keeping things in this range.  High end reflective coatings can keep losses well below 10%.  More important is that they need to be very smooth to minimize scatter to improve contrast.  That's why silver coated or even glass prism diagonals are usually judged to be better than dielectric prisms.  Dielectric coatings just aren't as microscopically smooth as silver and polished glass.

Yeah, that's the general knowledge but that seems to vary from person to person, and from model to model in my experience. I compared my three GSO dielectric 99% diagonals to a simple aluminum diagonal (91%), the difference is 8% but I could plainly see the extra brightness of stars, and more obvious colors, with Airy disks chiseled more finely (tested with a Celestron 5 and an 80mm triplet).

Did the same comparo with a vintage Vixen-made Celestron prism, the dielectrics were sharper and brighter, found the same bonus in color saturation. Then a final exam between two recent chinese Celestron prisms and the old japanese prism, the latter scatters less inside the glass and at the (multi-coated) surfaces, as evidenced by shooting a laser through it. Plus it improved the diffraction patterns in a 130mm Vixen doublet apo relative to dielectrics because it acts as a glasspath, I assume. But most modern apos are not designed to be fine-tuned by their diagonal, I believe.

[John]

1 hour ago, Ben the Ignorant said:

..... which doesn't display too much coma either, thanks to quality eyepieces that keep the stars tight enough over the whole field.

Don't want to sound too pendantic but coma is most commonly produced by the scope mirror not the eyepiece.  Well corrected eyepieces enable you to see the coma that the scope produces.

[Geoff Lister]

Another possibility, within your budget, is the Skywatcher Heritage 90P Virtuoso. It is a nice compact setup, and under dark skies, it should show you many DSOs. It can be used, unpowered, as a Dobsonian mount; powered, with simple tracking, and the option of buttons to give fine control of the mount's position; and, you can add a Synscan handset for full GOTO. It also comes with an "L" shaped bracket, so that you can mount a DSLR camera in place of the optical tube.

Geoff

[Moonshane]

At the budget stated it is highly unlikely that minor differences in light transmitted will be a factor. Any scope is generally better than none.

[happy-kat]

I have the Virtuoso mount and in the cold it really didn't like running on a set of AA batteries, I now use a celestron liFeP04 battery and it's running great, I bought a goto handset for it too. However in your dark location I'd be more tempted to use my heritage 130p for the bigger aperture, having watched a juvian moon shadow transit on Jupiter the telescope did good.

If you can get to a local club to see different equipment and sizes it could help in your choice.

[JOC]

The standard answer always tends to be a Dobsonian 200P (or 150P).  The one I've got tracks and does Goto and new would bust your budget, but I did recently see one go second hand for much less.  However, a 200P should give you option to plug in your DSLR.  You buy something called a T ring and it mounts as you camera lens would and then provides a 'nose' that drops into the 2" focuser EP holder.  You can also connect to a 1.25" EP holder (the usual size that I imagine a 150P has), by adding in other connectors.  For example I've got a 2 x Barlow that unscrews and provides the bits needed for this. 

[Louis D]

4 hours ago, JOC said:

The standard answer always tends to be a Dobsonian 200P (or 150P).  The one I've got tracks and does Goto and new would bust your budget, but I did recently see one go second hand for much less.  However, a 200P should give you option to plug in your DSLR.  You buy something called a T ring and it mounts as you camera lens would and then provides a 'nose' that drops into the 2" focuser EP holder.  You can also connect to a 1.25" EP holder (the usual size that I imagine a 150P has), by adding in other connectors.  For example I've got a 2 x Barlow that unscrews and provides the bits needed for this. 

Although most Dob focusers don't have enough back focus to reach prime focus with a DSLR.  I can only reach focus in mine with the aid of a 2" barlow or the nosepiece of my GSO coma corrector.  Some Newts intended for photography actually have a focuser tube that has a section that can be removed when a camera is attached to increase back focus.  The down side is that visually, these scopes have a larger than typical secondary to better illuminate a camera sensor, which has the downside of decreasing constrast slightly.  TANSTAAFL