Reflector vs Refractors

[Stu]

5 hours ago, andrew s said:

I am happy to accept that if you can have two or more telescopes then a small apo refractor for bright wide field observing and a large reflector for dimmer smaller objects is ideal. 

However, that is not the point I have been trying to counter. I have just been looking at the intrinsic comparison of reflectors and refractors.

Say you are looking for your first telescope and you go to the FLO website what might you chose for visual work. 6mm max pupil as per @Alien 13.

Sky_watcher for price performance. You might consider:

Heritage 150 P 150 mm diameter f/5 750 mm fl £199

Heritage 130P 130 mm diameter f/5 650 mm fl £142

Evostar   80ED  80 mm diameter f/7.5 600 mm fl £379 without mount

Evostar 100ED 100 mm diameter f/9 900 mm fl £757 without mount.

I would submit that there are eyepieces available to allow the maximum possible field stop for all these in a 2"  and that for all of them the magnification can be such that the exit pupil is 6mm or less. The reflectors can be equipped with a coma corrector for the cost of the refractor mounts / field flateners.

I conclude that at the two ends of the spectrum the small refractor and large Dobsonian are givens but there is an overlap where things are not so clear cut.

On @Stu f/1 Dob it might be worth considering that the ESO VLT 8m mirrors are f1.8  and while it might not do for visual that f/1 Schmidt Cameras were made.

Indeed as a teenager I visited the Cambridge astronomy department where the were trying out an all mirror telescope design which is only now being build as the LSST (3.5 degree field). The main mirror was just 200mm in diameter. 

So extremes are possible for specific use just like the Scopetech 80mm f/12.5 or LSST.

Regards Andrew

PS In the end I don't think the technology matters that much. Some of the best telescopes are hybrids. 

All interesting points Andrew. I don’t think I would ever suggest, say, a 4” apo refractor as a first scope for anyone. I quite agree that there are many better entry points with larger aperture that would be more affordable and show more.

I think visually people can then go in a few different directions, or possibly multiple directions eg increase aperture to show better DSO views or better resolution on planets or the Moon. Or, they can appreciate the aesthetic element of observing in terms of stars shapes, contrast and  also widefield views, and they then head towards the 3 to 5” apo refractors.

I know that you can see more in a larger scope, but I could easily survive with my 4” Tak because it does everything; lunar, planetary, doubles, white light solar and widefield deep sky, even enjoyable DSO performance under dark skies, plus it is portable enough to take on a plane to get to those dark skies.

No right or wrong answers as ever.

[andrew s]

@Stu I included the150P and 100ED on the very old rule of thumb that the minimum for serious astronomy was a 4" refractor or 6" reflector often repeated by Sir PM.

If I was going to have just one telescope for general use it would be the best quality 8" Newtonian I could lay my hands on. You could then go almost any where. Wynne corrector for imaging,  powermate for planets etc. If truth be told my wow moment was an 8" Hinds A mirror in a homemade Newt, after two indifferent refractors and a disastrous Cosmotron SCT. It snapped into focus and the diffraction spikes were to die for. Loved them ever since.

Enjoy your (whatever the collective noun is for telescopes is) of telescopes.

Regards Andrew 

[John]

I suppose there comes a point when you have been in the hobby quite a while and have seen quite a lot of stuff.

Perhaps there is a fork in the path at that point where you becomes less interested in seeing new stuff and more interested in seeing the best quality views possible at lesser apertures ?

Maybe light pollution intrudes and you either get a huge dob and a camper van to carry on going deeper and further or invest in premium quality smaller apertures ?

As @Stu says in his post above, there are multiple options as you go down the path and all of them lead to interesting new challenges and places

Just don't step on the fork !

 

[andrew s]

22 minutes ago, John said:

I suppose there comes a point when you have been in the hobby quite a while and have seen quite a lot of stuff.

Perhaps there is a fork in the path at that point where you becomes less interested in seeing new stuff and more interested in seeing the best quality views possible at lesser apertures ?

Maybe light pollution intrudes and you either get a huge dob and a camper van to carry on going deeper and further or invest in premium quality smaller apertures ?

As @Stu says in his post above, there are multiple options as you go down the path and all of them lead to interesting new challenges and places

Just don't step on the fork !

 

I fully agree, but there are many forks visual/imaging, photometry and spectroscopy/art imaging, variable stars magnitude estimates/sketching etc. each to is own as long as it's enjoyable. We live in an age where we have far more options at a reasonable cost than in the past.

Regards Andrew

[Captain Scarlet]

58 minutes ago, andrew s said:

 

Enjoy your (whatever the collective noun is for telescopes is) of telescopes.

I believe the collective noun is “divorce”

Edited July 5, 2020 by Captain Magenta

[JeremyS]

1 hour ago, andrew s said:

after two indifferent refractors and a disastrous Cosmotron SCT

Ouch!

[JeremyS]

1 hour ago, andrew s said:

after two indifferent refractors and a disastrous Cosmotron SCT

On the plus side, it sounds like you managed to avoid the Dynamax 8 SCT, though 🙂

 

[Alan White]

1 hour ago, John said:

I suppose there comes a point when you have been in the hobby quite a while and have seen quite a lot of stuff.

Perhaps there is a fork in the path at that point where you becomes less interested in seeing new stuff and more interested in seeing the best quality views possible at lesser apertures ?

Maybe light pollution intrudes and you either get a huge dob and a camper van to carry on going deeper and further or invest in premium quality smaller apertures ?

As @Stu says in his post above, there are multiple options as you go down the path and all of them lead to interesting new challenges and places

Just don't step on the fork !

 

I have to say @John, I think you have hit this bang on and that you do reach that fork in the path.
It may be years, it may be sooner, but boy do you hit that fork.
I have chosen the present path with lesser aperture great quality refractor and as you say in my case light pollution has played a part in this.
I am sure that another fork will present itself in due time of course.

 

Edited July 5, 2020 by Alan White

[Timebandit]

 

 

 

I started of in the hobby on a refractor. And given the choice of a good refractor v reflector at the same aperture then I would opt for a refractor every time. I just find on targets such as stars / doubles then a refractor image is just so sharp and clear of a pinpoint star visual image. But after I had been in the hobby for some time you realise that to start hunting for those faint fuzzy DSO objects then you really do need aperture (together with Dark Sky's). And the only way to get plenty of aperture that is cost effective and portable is through a reflector. You get so much more aperture per inch to the £  with a reflector. So refractor v reflector is not a debate in my head anymore , as have both now and they are both needed and used for my particular preference on targets that I feel that I get the best views to my eyes.

 

 

[Dannomiss]

39 minutes ago, Timebandit said:

 

 

 

I started of in the hobby on a refractor. And given the choice of a good refractor v reflector at the same aperture then I would opt for a refractor every time. I just find on targets such as stars / doubles then a refractor image is just so sharp and clear of a pinpoint star visual image. But after I had been in the hobby for some time you realise that to start hunting for those faint fuzzy DSO objects then you really do need aperture (together with Dark Sky's). And the only way to get plenty of aperture that is cost effective and portable is through a reflector. You get so much more aperture per inch to the £  with a reflector. So refractor v reflector is not a debate in my head anymore , as have both now and they are both needed and used for my particular preference on targets that I feel that I get the best views to my eyes.

 

 

Love this. And how much would you budget for a refractor. I wouldn't have a clue 

[Dannomiss]

On 03/07/2020 at 19:27, Philip R said:

Here's my 3p's worth... (0.01p per bullet point)...

• cleaner/clearer views on brighter objects, ie no chromatic abberation as with 'some' refractors
• cheaper to make and sell, rather than grinding two or more elements of matching glass for lenses of the same size
• lighter OTA

We are talking about reflectors here, just so I understand? 🤔