Best scope for around £600

[James Vincent]

I do Agree that Refractors  give a higher contrast image than reflectors because there is no obstruction, reflectors also suffer from coma that inversely proportional to the F ratio.

is the secondary mirror on your dob glued on to the mounting or is it in a cell?

The reason i ask is that lots of dobs suffer from distortion of the secondary mirror  causing astigmatism.

[John]

My refractors seem to "punch above their weight"  quite often. My ED120 produces planetary images that are surprisingly close to that which my 12" F/5.3 dob produces, given the very large aperture difference between the scopes. When seeing conditions are moderate or better the dob pulls ahead though has shown me planetary and lunar details that the refractors can't or can only hint at.

On double stars I prefer the precision with which the refractor resolves the airey disks of stars with a faint diffraction ring around the brigter ones - just like in the optical text books. The dob star images are the best I've seen in a newtonian but are still a little unrefined compared with the refractors.

I think a skilled, dedicated and experienced observer can make 4" refractor optics reveal some amazing detail. I see far more with my 4" and 5" refractors now than I did observing with similar scopes a decade or more back. But back then I did not have the experience that I have now and was starting to find 4" of aperture a little frustrating. Fortunately at that point I acquired more aperture in the forms of an 8" SCT and then an 8" dobsonian and those enabled my limited observing ability to probe further, reveal more detail and to see deeper. This kept the flame of my interest in the hobby alive and bright.

Thats why I'd tend towards reccommending something like an 8" or 10" dobsonian to someone relatively early in the hobby.  The additional aperture will give them access to views that will motivate them further wheras staying with a smaller aperture, even if it is of high quality, will mean that they need to work much harder to obtain further observing rewards running the risk of frustration setting in.

Those are just my thoughts based on my own personal experience over the years. As ever "your mileage may vary" 

 

 

 

 

[Timebandit]

 

The conclusion I have come to is what the OP might not want to hear but this is my opinion based on experience and knowledge. But there are many more experienced and knowledgeable people on this site so I can only speak for myself 

In my opinion you need a refractor and a newt to get the best out of this hobby. You then have the clarity of a lens and the aperture of a mirror to work with as the tools so to speak. This is the route I have taken the refractor because I like the crystal clear sharp views and great for handling and transport. And the reflector of 14" with 1/10pv as a great aperture for DSO (good on planetary also) . Therefore I have a foot in both camps and I am very glad I have this. 

If I had to choose from the 14" dob or the refractor then I would not like to be without either. But if I really really had to choose then I would keep the Dob. And the reason for this is as I have become more interested in DSO lately, rather than just planetary and lunar. The Dob is just so good at DSO and also very capable of planetary (but without that HD type of image the frac seems to produce in my eyes) . So to the OP IMO  buy one recommend frac and one recommend dob when funds allow. In which order you buy first is for you to decide after reading all these posts. Or go to the local astronomy club or a star party and have a look through a few scopes, your eyes may prefer the views through a refractor or prefer the reflector, all are eyes are different and see things in possibility a different way. ☺

[N3ptune]

This discussion makes me want a Refractor badly now...

[mikeDnight]

14 hours ago, Chris Lock said:

+1 for the above, and to ad to it I personally feel the image is more steady particularly in a long frac. Partly this is because of the large depth of focus, and maybe faster thermal equilibrium, easier to figure slow lens etc? I don't even notice the atmosphere at all with my classic Japanese 76mm f16 refractor from the get go, but do with a 6" f5 Newt for example. The down side of the pea shooter frac is that the image is dim and you have to resign yourself to having muddy knees when viewing anywhere near zenith. 

I'd be interested to see how a 6" f/8 Newt/Dob does on planets, I occasionally hear very good things about these but note that they pass hands quite regularly for some reason.

A 6" F8 Newtonian is a very capable planetary scope. My observing buddy paulastro (image attached) currently uses a 6"F8 for lunar and planetary. He calls it his 6" Apo! 

Paul is a really experienced planetary observer with an exceptionally keen eye. Though he prefers apo doublet refractors above anything else for planetary and lunar he's also as tight as a ducks rear, and so feels content using his humble reflector. Large aperture reflectors are not the way to go if a person's interest lies primarily in the Moon and planets. They may appear to give excellent views but they all suffer from "The Dob Throb!" which is that undulating softness and image smearing that destroys the finest threads of planetary detail. As one of our U.S. brethren stated on Cloudy Nights in response to the aperture is King brigade, " If aperture is King then quality is queen, and as in chess, the queen is more powerful"!

The reason for The Dob Throb isn't just to do with sensitivity to atmospheric turbulence due to greater aperture, or with internal heat. It's also a product of the design. An examination of the ray trace of say a 14" F4 Newtonian as compared to that of an average ED apo, or even an 6"  F8 Newt' illustrated the problem. The image forming capability of such a short F ratio reflector is crippled by its design. Even fractionally off axis and the image falls to bits! For that reason a longer F ratio Newtonian is a far better choice for planetary. Planetary observers don't need the light gathering power of a large aperture, they need the sharpest image possible. I've seen a 4.5" F11 Newt' best a Vixen fluorite. It's power lay in It's focal ratio and not in It's aperture! That same Vixen regularly pounded the pants off countless much larger reflectors.

Having said all that, there is something else to bare in mind and it was stated by the great W.F. Denning in his wonderful book 'Telescopic Work for Starlight Evenings. He wrote "Some men will undoubtebly see more with 5" of aperture than others will with 10". He also amusingly stated "The observer himself constitutes the most important part of his telescope: it is useless having a glass of great capacity at one end of a tube, and a man of small capacity at the other." 

Orion Optics make a 150mm F10 Newtonian on a Dobson mount which is reportedly an outstanding planetary performer. It's optics would be essentially perfect! Looking at Paul's 6" F8 it is easy to see why such a scope would be a delight to use. If bigger really is better and with 46+ years experience at the eyepice, he'd be using a big scope!

Mike 

 

[mikeDnight]

13 hours ago, John said:

My refractors seem to "punch above their weight"  quite often. My ED120 produces planetary images that are surprisingly close to that which my 12" F/5.3 dob produces, given the very large aperture difference between the scopes. When seeing conditions are moderate or better the dob pulls ahead though has shown me planetary and lunar details that the refractors can't or can only hint at.

On double stars I prefer the precision with which the refractor resolves the airey disks of stars with a faint diffraction ring around the brigter ones - just like in the optical text books. The dob star images are the best I've seen in a newtonian but are still a little unrefined compared with the refractors.

I think a skilled, dedicated and experienced observer can make 4" refractor optics reveal some amazing detail. I see far more with my 4" and 5" refractors now than I did observing with similar scopes a decade or more back. But back then I did not have the experience that I have now and was starting to find 4" of aperture a little frustrating. Fortunately at that point I acquired more aperture in the forms of an 8" SCT and then an 8" dobsonian and those enabled my limited observing ability to probe further, reveal more detail and to see deeper. This kept the flame of my interest in the hobby alive and bright.

Thats why I'd tend towards reccommending something like an 8" or 10" dobsonian to someone relatively early in the hobby.  The additional aperture will give them access to views that will motivate them further wheras staying with a smaller aperture, even if it is of high quality, will mean that they need to work much harder to obtain further observing rewards running the risk of frustration setting in.

Those are just my thoughts based on my own personal experience over the years. As ever "your mileage may vary" 

 

 

 

 

I've never felt frustrated by smaller apertures, honest!?

Mike

[Chris]

Just now, mikeDnight said:

A 6" F8 Newtonian is a very capable planetary scope. My observing buddy paulastro (image attached) currently uses a 6"F8 for lunar and planetary. He calls it his 6" Apo! 

Paul is a really experienced planetary observer with an exceptionally keen eye. Though he prefers apo doublet refractors above anything else for planetary and lunar he's also as tight as a ducks rear, and so feels content using his humble reflector. Large aperture reflectors are not the way to go if a person's interest lies primarily in the Moon and planets. They may appear to give excellent views but they all suffer from "The Dob Throb!" which is that undulating softness and image smearing that destroys the finest threads of planetary detail. As one of our U.S. brethren stated on Cloudy Nights in response to the aperture is King brigade, " If aperture is King then quality is queen, and as in chess, the queen is more powerful"!

The reason for The Dob Throb isn't just to do with sensitivity to atmospheric turbulence due to greater aperture, or with internal heat. It's also a product of the design. An examination of the ray trace of say a 14" F4 Newtonian as compared to that of an average ED apo, or even an 6"  F8 Newt' illustrated the problem. The image forming capability of such a short F ratio reflector is crippled by its design. Even fractionally off axis and the image falls to bits! For that reason a longer F ratio Newtonian is a far better choice for planetary. Planetary observers don't need the light gathering power of a large aperture, they need the sharpest image possible. I've seen a 4.5" F11 Newt' best a Vixen fluorite. It's power lay in It's focal ratio and not in It's aperture! That same Vixen regularly pounded the pants off countless much larger reflectors.

Having said all that, there is something else to bare in mind and it was stated by the great W.F. Denning in his wonderful book 'Telescopic Work for Starlight Evenings. He wrote "Some men will undoubtebly see more with 5" of aperture than others will with 10". He also amusingly stated "The observer himself constitutes the most important part of his telescope: it is useless having a glass of great capacity at one end of a tube, and a man of small capacity at the other." 

Orion Optics make a 150mm F10 Newtonian on a Dobson mount which is reportedly an outstanding planetary performer. It's optics would be essentially perfect! Looking at Paul's 6" F8 it is easy to see why such a scope would be a delight to use. If bigger really is better and with 46+ years experience at the eyepice, he'd be using a big scope!

Mike 

 

What a wonderful post  I'm going to come back to this and memorise those quotes! I happen to be in the market for a Dob and a frac after a switch around so this is giving me food for thought!

[kerrylewis]

Very interesting thread.

What do people think about masking to reduce the aperture on a large Newtonian for planetary use? I have experimented with a mask on my 14" Dob and on Jupiter, for example, it did improve the contrast but I don't think that it improved the clarity of detail; refractors still won out in that department.

As a compromise though it may be worth considering.

[John]

1 hour ago, mikeDnight said:

I've never felt frustrated by smaller apertures, honest!?

Mike

As I said "your mileage may vary". And yours obviously does Mike

I have been frustrated when I owned scopes with less than 100mm aperture so thats the minimum for me. If that was all that I'd owned there are so many fine sights that I'd have missed out on that I'd have quit the hobby, at least the observing part, years back I think. I'm far from the best observer around and I'm not that patient or diligent so I have to make up for those deficiences with some aperture I'm afraid 

 

[Moonshane]

The thread's wandering a bit but I suppose it all helps!

Mike's comments above are why I 'invented' my dobfractor using aperture masks of different aperture (100mm f18, 130mm f15 and 165mm f11) to adjust for seeing. The results are really excellent and allow me to swap between big fast aperture and smaller slower aperture in a jiffy.

 

Thankfully I also have a 6" f11 newt too, although I have now just got the OTA which I use on a giro iii

 

[alacant]

Traditional elegance? A 4" f10. HTH.

[Moonshane]

I sold the OTA recently (and bought one at a slightly higher spec) for £100 so yes, they are cheap!

[mikeDnight]

27 minutes ago, Moonshane said:

The thread's wandering a bit but I suppose it all helps!

Mike's comments above are why I 'invented' my dobfractor using aperture masks of different aperture (100mm f18, 130mm f15 and 165mm f11) to adjust for seeing. The results are really excellent and allow me to swap between big fast aperture and smaller slower aperture in a jiffy.

 

Thankfully I also have a 6" f11 newt too, although I have now just got the OTA which I use on a giro iii

 

Its not often youll hear me say this but thats a beautiful Newtonian and right up my street. Equatorial too! 

Mike ?

[StarryEyed]

A orion optics 150 vx with free 1/10 optics costs ￡381. Good quality scopes can be had for little money. 

 

[mikeDnight]

1 hour ago, John said:

As I said "your mileage may vary". And yours obviously does Mike

I have been frustrated when I owned scopes with less than 100mm aperture so thats the minimum for me. If that was all that I'd owned there are so many fine sights that I'd have missed out on that I'd have quit the hobby, at least the observing part, years back I think. I'm far from the best observer around and I'm not that patient or diligent so I have to make up for those deficiences with some aperture I'm afraid 

 

I'm sure you do yourself an injustice there John! I've read your excellent equipment reviews! 

As the original post expressed his interest to be the planet's, this thread has helped me to focus on where my own heart lies, which would be a 4 to 5 inch refractor or a long focus 6" Newtonian.  That's where contentment lies for me. I'm quite happy looking through other folks big scopes but have no desire to own one. ☺

Mike

[Chris]

4 minutes ago, StarryEyed said:

A orion optics 150 vx with free 1/10 optics costs ￡381. Good quality scopes can be had for little money. 

 

Stop it you're giving me ideas!

[kerrylewis]

1 hour ago, Moonshane said:

The thread's wandering a bit but I suppose it all helps!

Mike's comments above are why I 'invented' my dobfractor using aperture masks of different aperture (100mm f18, 130mm f15 and 165mm f11) to adjust for seeing. The results are really excellent and allow me to swap between big fast aperture and smaller slower aperture in a jiffy.

 

Thankfully I also have a 6" f11 newt too, although I have now just got the OTA which I use on a giro iii

 

1 hour ago, Moonshane said:

The thread's wandering a bit but I suppose it all helps!

Mike's comments above are why I 'invented' my dobfractor using aperture masks of different aperture (100mm f18, 130mm f15 and 165mm f11) to adjust for seeing. The results are really excellent and allow me to swap between big fast aperture and smaller slower aperture in a jiffy.

I didn't explain my comment about masking very well. It was intended to suggest that a medium aperture Dob might be the best answer for the OP who said that, although he was interested in the planets, he would also like to view DSOs, and perhaps some masking would help with the planets.

 

[paulastro]

8 hours ago, mikeDnight said:

A 6" F8 Newtonian is a very capable planetary scope. My observing buddy paulastro (image attached) currently uses a 6"F8 for lunar and planetary. He calls it his 6" Apo! 

Paul is a really experienced planetary observer with an exceptionally keen eye. Though he prefers apo doublet refractors above anything else for planetary and lunar he's also as tight as a ducks rear, and so feels content using his humble reflector. Large aperture reflectors are not the way to go if a person's interest lies primarily in the Moon and planets. They may appear to give excellent views but they all suffer from "The Dob Throb!" which is that undulating softness and image smearing that destroys the finest threads of planetary detail. As one of our U.S. brethren stated on Cloudy Nights in response to the aperture is King brigade, " If aperture is King then quality is queen, and as in chess, the queen is more powerful"!

The reason for The Dob Throb isn't just to do with sensitivity to atmospheric turbulence due to greater aperture, or with internal heat. It's also a product of the design. An examination of the ray trace of say a 14" F4 Newtonian as compared to that of an average ED apo, or even an 6"  F8 Newt' illustrated the problem. The image forming capability of such a short F ratio reflector is crippled by its design. Even fractionally off axis and the image falls to bits! For that reason a longer F ratio Newtonian is a far better choice for planetary. Planetary observers don't need the light gathering power of a large aperture, they need the sharpest image possible. I've seen a 4.5" F11 Newt' best a Vixen fluorite. It's power lay in It's focal ratio and not in It's aperture! That same Vixen regularly pounded the pants off countless much larger reflectors.

Having said all that, there is something else to bare in mind and it was stated by the great W.F. Denning in his wonderful book 'Telescopic Work for Starlight Evenings. He wrote "Some men will undoubtebly see more with 5" of aperture than others will with 10". He also amusingly stated "The observer himself constitutes the most important part of his telescope: it is useless having a glass of great capacity at one end of a tube, and a man of small capacity at the other." 

Orion Optics make a 150mm F10 Newtonian on a Dobson mount which is reportedly an outstanding planetary performer. It's optics would be essentially perfect! Looking at Paul's 6" F8 it is easy to see why such a scope would be a delight to use. If bigger really is better and with 46+ years experience at the eyepice, he'd be using a big scope!

Mike 

 

 

Cor, that's one handsome dude in that photograph with the 6 inch f8 !   

At the risk of heaping ridicule on the good looking devil, here's another picture of him in 1973 with, yes your quite right, another 6" f8.

 

 

Personally, I think the guy has improved with age!

[Moonshane]

If you didn't setup the photos to look alike then they are an amazing coincidence of stance!

 

[rockystar]

if you've got a stance that works, no need to change it

 

[paulastro]

5 minutes ago, Moonshane said:

If you didn't setup the photos to look alike then they are an amazing coincidence of stance!

 

Ha ha, I'm afraid I'm rather a sad OG, so no coincidence! 

[Moonshane]

True. After all, it's the same jumper

[Gary170782]

Thank you everyone for your detailed responses. I decided on the 200p dobsonian for several reasons but mainly after trying a few other scopes, this one just felt right for me. I've taken some Peoples advise also about getting a telrad finder and bought a Cheshire collimator which I'm not sure if I needed it or not when brand new? I'm going to take my time with the EP's as i know there are loads to choose from. Well okay I bought 1, got myself a nice little 18mm BST so I'll see how that goes. Thanks again everyone. 

On 13/12/2016 at 23:07, rockystar said:

Come down to Heaton Park on a clear thursday evening. there will be a variety of scopes on show that you will be able to look through

 

Isn't that going to be over 5 meters long? 

Thanks, I only live round the corner from Heaton park, where abouts does everyone set up?? J

[N3ptune]

@Gary170782

Congratulations, this 203mm Newtonian will keep you busy for a long time! there are many things to see with it.

After more then 1 year using a 203 mm aperture, I feel I am good to use it for many more years to come.

 

[Mark at Beaufort]

13 hours ago, paulastro said:

 

Cor, that's one handsome dude in that photograph with the 6 inch f8 !   

At the risk of heaping ridicule on the good looking devil, here's another picture of him in 1973 with, yes your quite right, another 6" f8.

 

 

Personally, I think the guy has improved with age!

Paul that looks like an AE scope made in Luton?? Am I correct? I always wanted to buy a scope from this company - I think I got the correct name.

Gary well done on buying the 200mm Dob I am sure it will be a good purchase.