I have mainly used either SCTs or refractors in the past for visual.
I should try my CDK again.
But for a lighter setup how would you rate Mak Cass scopes and what brands and apertures would you recommend? I don't think I have even looked through one before.
I don't know a lot about who makes Maks. TEC used to. Skywatcher/Saxon seems to have some. Meade had a small one on a goto. Intes Micro used to make them.
Mewlon isn't a Mak but seems in a similar category. Price is now a fair bit higher though.
Just general visual not specifically planets more like an SCT goto which is a jack of all trades visually.
I don't know a lot about them or which ones are good or best value.
- Maksutov Newtonians, mainly by Intes and Skywatcher; typically f/4 to f/8;
- DD Maksutov's original designs;
- The "Gregory Maksutov" cassgrain with an aluminised spot on the corrector, probably the most common type;
- the Rumak cassegrain, where the secondary mirror is separate from the corrector;
- sub-aperture mak cassegrains (Vixen and Takahashi).
2. The optical characteristics inherent in the design you are considering, and there are several if you include scopes that can only be acquired secondhand.
If looking for a lunar & planetary scope they're typically f/12 - f/15 with small secondaries and this really does count. Intes made some at f/8 and f/10, but like Meade/Celestron SCT's, it is not an optimal choice.
All maks are by design perfectly corrected for spherical and chromatic aberration on axis and if well made, should show textbook diffraction patterns at extremely high power. For example the Rumak gives perfectly corrected images over a flat focal plane (nirvana, some would say), whereas the Gregory Mak designs typically have a slight spherochromatism and a curved focal plane, similar to SCT's.
There is as usual the question of the central obstruction due to the secondary mirror and baffles. This varies. Some of the smaller maks have quite large CO, as high as 35% (eg the 102 and 127mm ones from Skywatcher/Orion).
Some designs have smaller secondaries - mine for example is 26%, and some have secondaries around 20% at which point the image is as good as unobstructed.
3. The quality of the optics.
Some manufacturers were awful, some average and some are consistently very good. Over several decades there have been a few premium maks like mine with very high quality optics which are in class of their own.
The point here is that some - notably Intes, Santel, AP, and TEC - consistently produced exquisite optics and these do command a premium. My Mk91 for example is probably the best thing you could wish for, short of a 9" APO.
Intes guaranteed 1/6 wave for standard scopes, 1/8 wave for the deluxe versions. Excellent if you can find one but heavy, built like a Russian tank - crude mechanically but effective.
Santel likewise 1/8 wave or better and with a DPAC interferogram.
Meade - made a 7" Mak Cass LX200, these are excellent optically if you can find one - however need some surgery - throw the fork in the bin and open up the OTA to remove a massive iron weight in the back;
APM Germany - Intes optics (ie superb) in an OTA built buy Matthias Wirth, small numbers only.
Astro-Physics and TEC - don't know if they set a tolerance but they are consistently excellent and beautifully built.
Skywatcher - early ones (2006-8) OK but not great, but the recent examples I've seen are consistently very good.
Orion (Synta) - same as the Skywatcher ones, rebranded
Saxon - Chinese versions included a 150 and 203mm mak, no idea of quality as I haven't seen one. Rare, it seems.
Ottiche Zen (Italy) - good optically but the correctors are not coated. Handmade in small numbers by a craftsman.
iOptron (made by Bosma) - cheap mass-produced Chinese version. Haven't seen one, personally.
Orion UK - do not touch those with a bargepole.
4. Size, weight, portability.
5. The ultimate is Questar, who build a scope designed as a portable observatory in a shoebox, built to last a lifetime, provide guaranteed support seemingly forever (a Questar made in 1957 can be serviced, cleaned, recoated and updated even now). Much admired, for obvious reasons.
6. Issues.
- the heavy corrector - can dew over but because it it is so thick theres more thermal mass, so this doesn't happen as quickly as it does with an SCT. Options include heaters or dewcaps. I use a dewcap and don't need a heater.
- internal tube current off the baffle - as with SCT's and the options is the same - either cool the scope, or insulate it. Insulation works very effectively on mine - it is usually ready to observe as soon as I am.
- focussing mechanism - some maks have moving-mirror focussing (like SCT's) with the usual issues with mirror slop (Skywatcher). Some use moving mirror focussing but got it right (no slop) - Intes, AP, TEC. Others have fixed mirrors and use a focuser bolted on the back (Santel, APM and some Intes) which means the focussing range is limited.
- collimation. Like all cassegrains they are sensitive to misalignment but f you get it right it should stay that way for a very long time.
One thing to keep in mind is two scopes, same aperture but different focal ratios, at the same magnification the image will be just as bright. You may know this, but some people can confuse f/ratio as having some visual consequence. f/ratio only matters photographically.
Sure, you won't be able to drop the magnification to get the same wide field with an 8" f/13 Mak as with an 8" f/5 Newt, but it's not like you are looking through a house brick either. Same magnification and with same AFOV, same image brilliance. What can vary though is optical quality, regardless of whether it's a Newt, SCT or Mak, & yeah sure, throw in refractors too.
Wavy has mentioned a lot of the tech stuff around Maks. I'll just relate my visual experiences with Maks vs SCTs.
I had used SCT's for my lunar sketching for many years. I had thought my SCT's were pretty good, even if the assembly of one of them was so poor that the corrector plate was very distorted by a way over tightened retention ring (current SCT owners, read this thread as it may affect your scope). I've since looked through Wavy's 9" Santel, and my 7" Intes Deluxe, and the difference is chalk and cheese. My Intes Mak, despite being an inch smaller in diameter, I can push it to 500X and I do not see image degradation, something I cannot do with my SCT and it is now of typical SCT optical quality. And a side-by-side comparison between the Mak and SCT, yes the image in the SCT is a little brighter because of the aperture difference, but the quality of the image, how fine the resolution is I can see in both scope, the difference in subtle contrast variations, and how stable the image is in both, the Intes tears shreds off the SCT. I ended up spending all my time with the Mak and the SCT just sat there, tracking, but with no one looking through it...
No matter the design of a scope, if optical quality is magnificent, then seeing conditions will be less detrimental for visual. If the optical quality is not there, then not all the photons will not be going where they should, so when seeing is not perfect, the photon distribution will be even more erratic, and the image instead of softly waving like a flag in a gentle breeze, will be scintillating/vibrating too making pushing high magnification difficult to impossible to use. But if the optics are schmick, then the image will just gently wave but high magnification will still be possible. This was one thing I came to find out when I tested 6 different Cats to find a new one. This pic below is of the final shoot out between the three shortlisted Cats, two SCT's and the Intes Mak.
Planets, particularly are sensitive to optical quality as it is not just about getting a sharp image, but contrast is often forgotten in the equation. Many of the details are either seen or lost as they are totally dependent on contrast. All the photons need to go where they should, as any stray photons will reduce contrast as well as resolution (coatings & baffling are not the only aspects affecting contrast).
DSO's. Nearly all my DSO experience with Cats has been under light polluted skies. You may think this is a disadvantage, but not really. Instead, it's meant that optical quality needs to be especially good in order to see the best image possible as contrast is the key. Get the optical quality right, and at the same magnification a Mak is good as the very best refractor and Newt around. Get the quality right, and it will mean seeing the skirt around the Homunculus Nebula or not in less than perfect seeing conditions at 200X.
Brands? Wavy has mentioned a few. There are not many Mak manufacturers, but all are boutique optics. Skywatcher though shouldn't be dismissed outright. Whoever it is that is making the 7" Maks for them is doing a stupendous job! They have been refining their manufacturing techniques over the years, and while their earlier Maks were very good (I've looked through these and seen the Enke division through one! ), the current crop of 7" Maks are even better. Will other brands that are re-badged Synta scopes be just as good? I cannot say as I have not looked through them. Maybe yes, maybe no - and there is form on the "no" side of things. Saxon at one time offered an 8" Mak, and I only know of one in Western Australia. And the Meade one I suspect is of Synta origin or the same manufacturer as produces for Synta.
Aperture? 7" is currently the largest readily available today. Larger aperture Maks are very rare today. With Intes now ceasing commercial production, and the sets of large diameter optics available to the likes of APM quickly diminishing, large diameter Maks (over 7") are very difficult to come by new. But what size aperture? That's entirely up to you and how deep your pockets are.
Alex.
Last edited by mental4astro; 04-04-2019 at 10:04 AM.
Thank you to Wavy and Mental for the great advice. Most helpful.
So a Skywatcher 180 would be a sweet spot for price, performance and availability? I am wanting a goto visual instrument as I haven't done a lot of visual for some time.
I can attest to the Maksutov being a brilliant design.
Whilst my limited time often sees me dragging out the little Skywatcher 127 Mak for brief glimpses at a clear sky, the images it throws out are ridiculously great for the price I paid for it. But of course its aperture is what it is, thus limited. On the occasion that I have the energy to set up my 8” Tec Mak, with conditions allowing, I am always absolutely blown away! Extremely large (and unaffordable to most) Apo views with a more limited field of view (perfect for planets, galaxies, planetary nebulae and globulars) is what I see this scope as being the absolute master of!
Take measures to manage the dew and these things are amazing!!
Take measures to manage the dew and these things are amazing!!
Catadioptric scopes have a bad reputation for being difficult to reach thermal equilibrium. They are notorious for being slow.
HOWEVER, there is a change of thinking about both cooling and dew control when it comes to closed-tube Cats, be they SCT's or Maks.
Instead of having them cool, DON'T let them cool!
Have a read through the following thread about insulating closed-tube Catadioptric scopes. It will mean not only not having to wait for thermal equilibrium, but you can begin using your scope at high power straight away, not two hours later.
Both of my Edge HD SCTs have the vents and have been fitted with TEMPest fans to help equilibrate. They generally don't cause an issue with thermals unless the temperature is dropping particularly rapidly...not especially unusual in winter even in Brisbane.
Another thing with closed tube designs is...don't store them inside. Sure, in the the garage/shed, but not in a spot where they're subject to Sun or other sources of heat. I think it goes without saying that no scope should be left in the Aussie Sun unprotected
The insulation thing is an interesting idea, might have to give it a go this winter...
On topic, all of these exceptional scopes are rare and not inexpensive instruments. The mainstream scopes can be great, but it's subject to random variability in QA. That doesn't mean good ones don't exist...IMO most of the reports (not those from the learned gents above of course!) of poor performing SCTs comes from folk that subject them to large temperature gradients and don't bother to collimate. The difference is night and day.
I, too, have seen the Encke Gap, about 4 years ago from our Sydney back yard, with my Edge HD 8". I wasn't looking for it but noticed it and observed it for some time, then looked it up afterwards. I was stunned. Having thought I was imagining things for some time afterwards, I've subsequently seen it again on those rare good nights with both my Edge HD 8" and Edge HD 11". Brisbane seeing is not usually good for 400x, but it does happen occasionally.
On the next image you quickly realise why it costs that much! 
......I want it..... NOW ..!!
