SCT, Mak or frac?

[OK Apricot]

Hey guys, 

My mind has been wandering today, thinking how I've got my light bucket, now I need something laser sharp for the solar system. 

As I understand it, SCTs and Maks are most suitable for this kind of visual astronomy due to the large focal ratio and use of a corrector plate, especially SCTs as they tend to be larger in aperture. OTOH I've read good refractors like to eat up magnification, have no central obstruction and due to the generally smaller aperture, are less affected by atmospheric turbulence. 

I like the idea of something relatively small, grab-and-go, and something to compliment the 200P bringing its own strengths to the game. 

What would you chose and why? 

Cheers! 

Edited February 13, 2022 by OK Apricot

[johninderby]

I”ve had small maks and SCTs and have now settled on a Classical Cassegrain for my grab’n’go setup. Bit sharper on axis than the mak or SCT and no problem with dewing and quick cool down and a proper crayford with dual speed focusing.

https://www.firstlightoptics.com/telescopes-in-stock/stellalyra-6-f12-m-crf-classical-cassegrain-telescope-ota.html

BTW the photo of the front of the scope on FLOs website is wrong as it shows the RC with it’s much bigger central obstruction. Due to be updated when they get the time.

If you want a frac then something like this might suit. Great optics and build quality and more expensive but a good all round scope..

https://www.firstlightoptics.com/telescopes-in-stock/starfield-102mm-f7-ed-doublet-refractor.html

The CC, mak or SCT have a narrower field of view but ideal for lunar / planetary and small DSOs Also easier on eyepieces so less expensive ones can be used.

Edited February 13, 2022 by johninderby

[Mr Spock]

Here was my choice:

So easy to move around, and so versatile. I can use it either wide field or high power. Also makes a great solar scope. A Dob and an apo to me gives the perfect combination. One scope can't do it all; two gets as close as you need.

It's a stable combination. I don't bother with the spreader. Just plonk the mount outside, attach the scope and switch the mount on - all done in seconds. Cool down is pretty quick too.

[dweller25]

+1 for a 4” Refractor - a proper telescope 👍😀

Very sharp, high contrast, fast cooling, less affected by poor seeing, look great.

[Same old newbie alert]

Yeah all 3!

[mikeDnight]

1 hour ago, OK Apricot said:

Hey guys, 

My mind has been wandering today, thinking how I've got my light bucket, now I need something laser sharp for the solar system. 

As I understand it, SCTs and Maks are most suitable for this kind of visual astronomy due to the large focal ratio and use of a corrector plate, especially SCTs as they tend to be larger in aperture. OTOH I've read good refractors like to eat up magnification, have no central obstruction and due to the generally smaller aperture, are less affected by atmospheric turbulence. 

I like the idea of something relatively small, grab-and-go, and something to compliment the 200P bringing its own strengths to the game. 

What would you chose and why? 

Cheers! 

 If you're looking for a sharp complementary scope, I'd suggest you discard the idea of a SCT, as they really don't deliver as visual solar system copes. They have light grasp and theoretical resolution, but nearly always produce soft, poor definition views when compared to pretty much any other design of telescope. As imaging instruments they can be superb!

 Refractors are arguably the sharpest scopes out there, but they are expensive aperture for aperture. They do however often compensate for their lack of resolving power by delivering superb definition and contrast, and can also out perform larger apertures in delivering the most aesthetically pleasing views of the Moon and planets.

 Maksutov's, unlike SCT's, approach refractor sharpness but with the advantage of greater aperture, or lower cost. Classical Cassegrains are both sharp and powerful due to their greater focal ratio, and cool relatively quickly as the are op-en tubed. 

 You could however consider a long focal length, smaller aperture Newtonian, such as a 150mm F10, which would be a great solar system scope.

Personally I love refractors, but that's a secret!

 

[OK Apricot]

Thanks for the input. So with a refractor, a decent one anyway, I'd probably be looking at similar money for a good mount to put it on. HEQ5 or similar. A lot of Maks I've seen come either fork or single arm mounted already. Something to think about I guess. Say your budget is... £700... What would you do and why? 

[MalcolmM]

4" refractor is hard to beat for the reasons stated above. Ironically I use a 60mm scope as my grab and go and my 4" as my main scope! It's all relative 60mm can be carried out/anywhere with 2 fingers! 4" is still easy (but more awkward than the 60mm) and probably would seem light as a feather compared to your 200mm. Personally I would go for a 2.5 or 3 inch refractor on the basis of it being so easy to take out on a whim when you don't want to drag the light bucket out!

Malcolm

[MalcolmM]

For £700 I'd go for a Takahashi FS60CB. You then have upgrade options of 76mm objective or the extender Q. But I must confess to being obsessed with all things Takahashi

Malcolm

[mikeDnight]

For £700 I think I'd keep my eye on Astro Buy & Sell. You'll often find a second hand Skywatcher 100 ED or similar.  They are really superb! And to be honest, I feel most ED refractors are so good these days that you don't need to worry about getting a lemon. Although Takahashi are great, and its a privilege to own one, the performance gap between them and today's ED apo's has closed dramatically over the last 20 years.

[neil phillips]

With a smaller feild of view. The CC will eat up a 4" on planets and the moon. No competition. Game over. But likely not popular. I am running for the hills. 

Edited February 13, 2022 by neil phillips

[mikeDnight]

24 minutes ago, neil phillips said:

With a smaller feild of view. The CC will eat up a 4" on planets and the moon. No competition. Game over. But likely not popular. I am running for the hills. 

I'm sure you're right Neil. No need to run; we're all grown-up's! 🤬

[mikeDnight]

Neil is absolutely right in what he says. I suppose its down to what you expect of a telescope. During the last Mars apparition I used three different scopes, a 10" F6 Dob, a 8" F6 Newtonian, and a 4" apo. There was no question that the larger apertures revealed more, but they didn't show an image as well defined. The 10" Dob was just awkward to use, which made observing less pleasurable. The 8" Newtonian and the 4" apo were mounted on my Vixen GP which made observing more comfortable. Below is a comparison between the 8" F6 and the 4" F8.

 

Below, Mars as observed with an 8" F6 Newtonian and a 4" F8 apo 27/9/2020 

 

How much detail do you want to see on Jupiter? Below is a sketch made on a night of exceptional seeing when Jupiter was riding high.

The 10", 8", and 4". Despite the superiority of the 10" over the 8" and the 8" over the 4", the 4" gave the most pleasing views. And although much brighter in the first two, the laser etched detail in the 4" gave up little to the larger scopes.

 

Edited February 13, 2022 by mikeDnight

[OK Apricot]

A very useful comparison there, Mike. Thanks for that. It looks like the refractor is going down the right trail for me. Your sketches say it all really. 

Going down this route, I dare say, would lead me to an excuse to start out in proper astrophotography - having owned one before, I would've thought the HEQ5 would be more than enough mount, right? Certainly for visual - it's a solid mount and held up well with my old  f/5 200p - I'd imagine it'd be up to the job for shorter exposures?.... I'm going off on a tangent here. 

But yes, those sharp and detailed views of the moon and planets are desirable. Coupled with my 200P dob, I think I'd have got the night sky covered. 

[chiltonstar]

 Before you hit the buy button, maybe look at some images with each type of scope on challenging subjects like Plato craterlet detail and Saturn. Images are inherently objective, visual descriptions tend to be subjective.

Chris

 

 

[paulastro]

9 hours ago, mikeDnight said:

Neil is absolutely right in what he says. I suppose its down to what you expect of a telescope. During the last Mars apparition I used three different scopes, a 10" F6 Dob, a 8" F6 Newtonian, and a 4" apo. There was no question that the larger apertures revealed more, but they didn't show an image as well defined. The 10" Dob was just awkward to use, which made observing less pleasurable. The 8" Newtonian and the 4" apo were mounted on my Vixen GP which made observing more comfortable. Below is a comparison between the 8" F6 and the 4" F8.

 

Below, Mars as observed with an 8" F6 Newtonian and a 4" F8 apo 27/9/2020 

 

How much detail do you want to see on Jupiter? Below is a sketch made on a night of exceptional seeing when Jupiter was riding high.

The 10", 8", and 4". Despite the superiority of the 10" over the 8" and the 8" over the 4", the 4" gave the most pleasing views. And although much brighter in the first two, the laser etched detail in the 4" gave up little to the larger scopes.

 

Nice sketches Mike.  As you'll recall, I was lucky enough to be observing with you on the night of the Jupiter observation, with my DL at the time.

As you say though, it was a night of exceptional seeing, and not what you can see every night.  Secondly, not everyone has your good eye and excellent artistic talent.  The latter point also applies to the night that you did the Mars drawings of course.

It could mislead less experienced and talented observers if they expected to see, and sketch, what you were able to do on both of these nights.

Edited February 14, 2022 by paulastro

[Nik271]

I own two Maks (127 amd 180 Skymax) and just bought a 4 inch ED refractor. I would say that any good scope with 4 inches of aperture would provide excellent detail up to x200magnificatioin on a good night. The OP already has  200P for top resolution on an excllent night of seeing so what is needed is a smaller scope for grab and go on most other nights.  Portability wise either a 4 inch ED refractor around F7-F8  or the 6 inch CC are  excellent choices which will deliver very sharp views.

Between a refractor or CC the choice is largely personal. CC will have diffraction spikes on bright objects, need to check the collimation occasionally when transporting. But it has the potential for even higher mags up to x300 I would expect. Refractor is smaller, lighter (4kgs) and hassle free maintenance with tighter stars. Good for wide views too. These days £700 buys a decent 4 inch ED refractor with FPL51 glass, good for up to x200.

PS. To throw a spanner in the works a cheaper option is the 127Mak (SW or Bresser) , of course smaller aperture than the 6 inch CC but really light (3kg) and excellent up to x200 again. Cons: no widefiled, some dewing issues. Costs only about £350 or so.

 

[OK Apricot]

Thanks for sharing your thoughts guys, looking like a refractor will be the way to go 👍

[MalcolmM]

One further thought @OK Apricot, you mention grab-and-go. For me, a 4" is just about grab and go! And I have one of the lighter 4" refractors I think. Whereas my 3" is a very easy grab and go. So ease of grab and go against that extra aperture and definition might be worth considering.

Malcolm

[OK Apricot]

Definitely, Malcolm, being grab and go is a more important factor here as I've got the aperture in my 200P. The main qualities of this next scope will be contrast and magnification in a package that I can get out the door, in the van and set up in a few minutes without getting the heart rate up too much. Not had a solid enough forecast for a full clear night yet, so I haven't had to get the dob in the van, but I'm a bit uneasy strapping the OTA and base in amongst my work equipment! That will be where the grab and go comes in - so I can break it down to smaller parts and take it in the cab of the van, not the cargo area 😬

[nfotis]

For planetary, I love my Skymax 180 Maksutov scope. It's no grab and go, though (easier to handle than a C9.25, to tell the truth). A Skymax 150 is easier to handle (a Skymax 127 is nice and cheap, but feels heavy despite its small size).

A 102ED or similar should be a nice refractor for general use (you may want to add a 2x Barlow for extra reach). It's longer than a Maksutov, though, and that may make handling it a bit harder. 

N.F.

[johninderby]

I’ve found the CC6” holds collimation as well as a mak. Never had to touch the collimation since I got it.

You should not disregard the increased resolution of a bigger aperture plus the ability to take higher magnification. My CC6” on a report tripod can be carried outside single handed. Fitted a carry handle to the OTA.

Thought about a 4” frac but bought a 5” APO instead. Lot heavier than the CC6” though and requires a solid mount. Not exactly grab’n’go. but a wonderful scope.🙂. 

Edited February 14, 2022 by johninderby

[MalcolmM]

2 hours ago, OK Apricot said:

grab and go is a more important factor here

A 3" APO would seem to be a good contender here. My 4" refractor (f7.4) is light but it is the length that makes it a little unweildy. I can take the 3" through doors on the tripod. I don't do that with the 4"

I may suffer Takitis but I acknowledge that there are many APOs at a fraction of the price that get universally great reviews.

Good luck and I genuinely feel a grab and go refractor will complement a big light bucket!

Malcolm

[Sunshine]

On 13/02/2022 at 13:30, johninderby said:

I”ve had small maks and SCTs and have now settled on a Classical Cassegrain for my grab’n’go setup. Bit sharper on axis than the mak or SCT and no problem with dewing and quick cool down and a proper crayford with dual speed focusing.

https://www.firstlightoptics.com/telescopes-in-stock/stellalyra-6-f12-m-crf-classical-cassegrain-telescope-ota.html

BTW the photo of the front of the scope on FLOs website is wrong as it shows the RC with it’s much bigger central obstruction. Due to be updated when they get the time.

If you want a frac then something like this might suit. Great optics and build quality and more expensive but a good all round scope..

https://www.firstlightoptics.com/telescopes-in-stock/starfield-102mm-f7-ed-doublet-refractor.html

The CC, mak or SCT have a narrower field of view but ideal for lunar / planetary and small DSOs Also easier on eyepieces so less expensive ones can be used.

That stellalyra sure is a nice looking piece of kit isn't it!

[johninderby]

5 minutes ago, Sunshine said:

That stellalyra sure is a nice looking piece of kit isn't it!

Yup and fits nicely into my scope lineup.  Hope the OP finds a scope that will suit them but there are so many nice scopes out there now can be a confusing choice.