Refractor for visual

[bosun21]

6 hours ago, mikeDnight said:

Schmidt originally designed his telescope to be a camera, so it's not surprising that's where it shines. DP is an imager not a visual observer, and so it's not surprising his choice of telescope is a Schmidt Cassegrain.

They still have to produce sharp images for the camera to capture!

[dweller25]

I believe SCT’s vary in optical quality which is a shame as I like the form factor.

I have had three, one was average, one was good and one was an utter lemon and trust me cool down, collimation and seeing were not factors.

I would never recommend SCT’s for visual astronomy based on my - limited - experience with them, which is a shame as I think the C6 might suit the OP quite well.

 

 

Edited January 25, 2023 by dweller25

[dweller25]

3 minutes ago, dweller25 said:

Edited January 25, 2023 by dweller25
Duplicate post

[Voxish]

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Edited January 30, 2023 by Voxish

[Mr Spock]

1 hour ago, Voxish said:

The views are sharper, the contrast better and the cool down faster and general usability better.

The comment about contrast always puzzles me as the difference in contrast range between 4" and 12" is beyond staggering. Same with sharpness. My 12" is still sharp at x380. Even a 6" apo can't come close.

A few nights ago I was looking at some doubles. One was 2.5" and separation was wide. The stars has small airy discs with a single faint diffraction ring. The diffraction ring is smaller than the airy disc of a 4"... How people can say the 4" apo has pinpoint stars when the airy disc is so large is another one of those baffling statements people made.

 

[Voxish]

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Edited January 30, 2023 by Voxish

[Louis D]

3 hours ago, Mr Spock said:

A few nights ago I was looking at some doubles. One was 2.5" and separation was wide. The stars has small airy discs with a single faint diffraction ring. The diffraction ring is smaller than the airy disc of a 4"... How people can say the 4" apo has pinpoint stars when the airy disc is so large is another one of those baffling statements people made.

At the same exit pupil size, the refractor's star image will be tighter because there's no central obstruction or spider vanes reducing the central peak intensity of the Airy disk.  The following diagram from TelescopeOptics.net shows how as the central obstruction grows from 0% to 50% of the clear aperture diameter, so grows the bloat of the Airy disk.  This manifests itself at the eyepiece as bloated instead of pinpoint stars.  I can confirm that my ED and APO refractors show much tighter stars than my Dob or Mak at a given exit pupil.

It is entirely possible that it is impossible as you say to separate a given double star pair due to insufficient resolution as a result of insufficient aperture in a smallish refractor versus a large reflector.  It's just that the unresolved pair will look nice and tight in the refractor relative to the larger reflector's view at the same exit pupil even if resolved into two slightly bloated stars.

[Louis D]

3 hours ago, Voxish said:

One of the most disappointing things, and something which ruins the  whole experience is that the contrast is, unless you are somewhere really dark is awful.

At the same exit pupil, the contrast should look the same.  It could simply be that your skies are incapable of supporting the Dob's higher powers necessary to equalize the exit pupil with that of the smaller refractor.  If you're looking for contrast on big objects like M31 that require lower powers to frame it properly as a whole; then yes, the smaller aperture instrument is the better choice.

[paulastro]

I do get some amusement from threads like this, proponents of all types of scopes making  out their favoured telescope is the best.  And, if you don't agree trying to persuade others with different views to change their minds.  Of course, they rarely will.

Well, I have a Celestron Starsense Explorer 8inch Dob a Celestron C5 (yes a SC!) and an Altair 80 ED-R doublet.  I enjoy using them all, and they all have advantages over the other two - and each a unique role. I'm not telling anyone what these are because you know what, it makes no difference at all what other people think.

And yes, I sometimes sit back and enjoy looking at each one of them when it's raining and I can't use them 🤣.

 

[Stu1smartcookie]

1 minute ago, paulastro said:

And yes, I sometimes sit back and enjoy looking at each one of them when it's raining and I can't use them 🤣.

 

lol Paul , you could start another debate with that line 🤣.. although im sure its been done before . 

[Mr Spock]

10 hours ago, Louis D said:

at a given exit pupil

But there's your problem. When I'm looking at a double star at x217 in my Dob; the equivalent exit pupil in the 102 is x71... If I use the same magnification in the 102 the exit pupil is 0.47 and the airy disc is huge unlike the Dob which is three times smaller.
 

10 hours ago, Louis D said:

At the same exit pupil

Same issue. When I look at the moon at x300 in the Dob the image is very bright with huge contrast; in the 102 it will be dull and lifeless. So at any given magnification, which is what observers use, so there is indeed a massive difference in contrast between the two.

You are not comparing like with like. If we were comparing a 6" Dob to a 6" Apo, then it's obvious which would be better in every way - except of course the huge difference in cost.

And for the record I believe both my scopes are excellent and fit for purpose and their intended use 

[Voxish]

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Edited January 30, 2023 by Voxish

[dweller25]

10 minutes ago, Voxish said:

Different scopes for different folks, who cares really, let's just go observe. 

 

I care 🙂

🤪🤪🤪🤪🤪

[dweller25]

I think the best solution for most people is 3 scopes…..

1. 4” refractor 

2. 7” Mewlon

3. 12” dobsonian

 

Edited January 26, 2023 by dweller25

[josefk]

12 minutes ago, dweller25 said:

I think the best solution for most people is 3 scopes…..

1. 4” refractor 

2. 7” Mewlon

3. 12” dobsonian

 

i don't think you're far off there...

[Grump Martian]

On 24/01/2023 at 08:09, badhex said:

Throwing in my lot with another vote for a 4" doublet, specifically the Starfield 102 as mentioned by @Mr Spock if you're in the UK, or other brandings for elsewhere in the world. 

Obviously it does not have the light gathering of a larger dob but the performance you do get per inch is exceptional. Added to that, with the right EP combo you can easily get 4° of sky at one end and 200x at the other, which is a great spread and covers many objects. 

I really enjoy using my Starfield under my light polluted skies

Edited January 26, 2023 by Grump Martian
Spelling

[paulastro]

6 hours ago, Stu1smartcookie said:

lol Paul , you could start another debate with that line 🤣.. although im sure its been done before . 

Perhaps best not 🤣.

[bosun21]

21 hours ago, Voxish said:

A big dob is a light bucket, it collects a lot of light, all of it.The light from distant galaxies, street lights, light from a factory miles away, all of it. One of the most disappointing things, and something which ruins the  whole experience is that the contrast is, unless you are somewhere really dark is awful. Everything is on a washed out milky background and all the detail is lost. The image is smaller with a frac, but since the contrast is so much better, after all the background is as black as black can be to contrast is far superior. 

I have to disagree with you on this. I sold my Starfield 102ED and bought a 12” dobsonian. It’s night and day as far as I’m concerned. I have only been bothered by extraneous light when the moon is up and it’s easily solved by a Baader Neodymium filter. The magnitude of difference in the amount of stars visible just can’t be compared to a 4” frac.

[mikeDnight]

The title of the post was refractor for visual, so presumably the op wants to know which refractor would be a good choice for visual observing. It seems that due to cost and ease of use, the humble 4" is a strong contender as a general purpose instrument. A 5" or 6" refractor would be better as far as being more capable, but cost can be the limiting factor.  And may be the op doesn't want to cart a large cumbersome tube assembly outside each time he wants to observe, as although it may initially be appealing to have a big reflector to play with, the in practice experience may not be so pleasing. I know that I personally much prefered observing with a small refractor on most occasions, despite large reflectors being alongside. One reason I like a good refractor is because of the definition.  Aperture isn't everything, as has been proven time and again. I've seen a beautiful detailed view of Saturn through a fine 200mm Dob on an excellent night of good seeing, made to look utterly lacklustre when compared to the view of Saturn through an 120ED alongside it. If the resolution gain of the 200mm was all that mattered, then he 200mm would surpass the 120ED showing the ultra fine divisions within the ring system, but it didn't. The difference was so obvious it was hard to comprehend, yet the smaller aperture refractor left the Dob way behind in terms of definition.

Edited January 27, 2023 by mikeDnight

[Franklin]

I see the old "Refractor v Reflector" debate has reared its ugly head again! I don't believe that there is a winner or ever will be in this. Different scope designs all have there pros and cons and of course the size and weight of the scope does as well. Finding the right fit for your particular needs is the important point and there are lots of factors to take into account. If you live in a top floor flat and have to carry your equipment down 3 flights of stairs every night then you will hardly want a big dob. On the other hand, if you have access to premier dark skies then a small grab and go refractor set up may not do your skies justice.

The "Refractor v Reflector" debate will always be with us and that is fair enough but.... surely everyone must know that proper telescopes have lenses?😄

[bosun21]

46 minutes ago, mikeDnight said:

The title of the post was refractor for visual, so presumably the op wants to know which refractor would be a good choice for visual observing.

Very true! We are all being sidetracked by our own personal preferences. I can wholeheartedly recommend the Starfield 102. It’s extremely well built and the FPL53 and Lanthanum lenses provide crisp and clear images. 

[RobertI]

Another vote for the 102ED. I'm a fairly recent convert to the joys of a 4" refractor for visual after many years with my highly capable Newts and an 8" SCT. Very pleased with the 4" all round and I tend to use it more than my other scopes for visual as most of my sessions are spur of the moment and fairly brief, so quick cooling, easy setup and minimal paraphernalia are important. The main limitations for me are globular clusters, where I think you need 6-8" and above to resolve enough stars to get that wow factor, and possibly galaxies. 

[Beardy30]

I love how my question has evolved in to such debate 😂 all good to read Chaps and we have shown how passionate we are for own scopes and preferences 👍🏼 it’s what this forum is all about 

Edited January 26, 2023 by Beardy30

[Franklin]

1 hour ago, Beardy30 said:

I love how my question has evolved in to such debate 😂

So have you ordered a 102ED F/7 frac yet?

[RobertI]

1 hour ago, Beardy30 said:

I love how my question has evolved in to such debate 😂

You mentioned the word “refractor”!