81 replies to this topic

[JanSpace]

This question came up due to repeatedly seeing on forums and in videos that a Maksutov is "not good for faint DSO viewing"

 

So, if you take a Maksutov and a Newtonian with (almost) the same aperture:

Mak: https://www.firstlig...ax-102-ota.html

Newt: https://www.firstlig...-dobsonian.html

 

And then you pair them with eyepieces that provide the same magnification and exit pupil for both:

1300FL, ~13FR Mak with 32mm eyepiece: 1300/32 = 41x mag, 32/13 = ~2.5 exit pupil

400FL, 4FR Newt with 10mm eyepiece: 400/10 = 40x mag, 10/4 = 2.5 exit pupil

 

Is the Newt still going to provide a "brighter" image? Despite the same exit pupil, magnification and aperture? I feel like that shouldn't be the case, but is there something I'm missing there?

 

My current guess for why that phrase is popular is:

It's because it's much easier to get a large exit pupil with even most "slow" Newtonians than it is with Maksutov telescopes, since they are almost always even slower; i.e. you can get a large exit pupil with a much shorter focal length eyepiece on a Newtonian, for a "brighter" view, while Maksutovs are always locked into exit pupils below 3 or 4mm even with 40mm+ eyepieces.

 

Is this a correct assumption, or are there also other factors involved? Sorry if I'm stating the obvious here, I'm just trying to figure out where that piece of conventional wisdom comes from.

[Bubbagumps]

It's not a good choice for faint DSO imaging. But in terms of what you see through an eyepiece, this is similar to the question of whether a faster lens will result in a brighter visual image than a slower lens. It's kind of a loaded question to ask whether images will appear brighter.

 

There is always going to be light loss through any optical system simply due to physical optics. The more elements you have in a lens or eyepiece, the more loss there will be. An SCT and Mak have corrector plates as well, so there are more elements to disperse light. But this type of loss in efficiency is usually very small and it won't stand out in a major way visually unless the optics are dirty or distorted and/or not collimated to the same level.

 

In terms of the actual differences in design and optical specs, the answer is that with the optical elements being equal in terms of transmission efficiency of the overall system, when an object is viewed through an eyepiece at the same magnification through two primary lenses of the same aperture but different focal ratios and focal lengths, the light that is making it's way to your pupils will theoretically have the same intensity. The light is simply being collected through different optical paths and this is dependent on the design of the scope. You will just need different focal lengths for the eyepieces to achieve the same magnification. 

Edited by Bubbagumps, 19 April 2024 - 03:32 PM.

[Kitfox]

Really the only truth to this is that some Maks will start vignetting (for multiple reasons) at large exit pupils.  You won’t detect this with your eye so much, but you can with afocal imaging. 

Edited by Kitfox, 19 April 2024 - 03:25 PM.

[Astrojensen]

 

Is the Newt still going to provide a "brighter" image?

No, not if everything else is equal (reflection losses, etc.). 

 

 

Despite the same exit pupil, magnification and aperture? I feel like that shouldn't be the case, but is there something I'm missing there?

No, your understanding of the situation is correct. 

 

 

 

My current guess for why that phrase is popular is:

It's because it's much easier to get a large exit pupil with even most "slow" Newtonians than it is with Maksutov telescopes, since they are almost always even slower; i.e. you can get a large exit pupil with a much shorter focal length eyepiece on a Newtonian, for a "brighter" view, while Maksutovs are always locked into exit pupils below 3 or 4mm even with 40mm+ eyepieces.

Correct! 

 

Summary: A slow (f/15, for example), is not worse for deep-sky, for any given exit pupil, than any other telescope, but it's just a lot easier to reach very low magnifications on fast systems, like an f/5 Newtonian. At medium to high magnifications, the Mak-Cass and the classic f/15 refractor can be excellent, and they often have much better correction across the field of view, than faster Newtonians. 

 

 

Clear skies!

Thomas, Denmark

[havasman]

 ...a Maksutov is "not good for faint DSO viewing"

 

There are too many available qualifiers that should be applied to think that a valid statement. But there are expansions to it that may be made. What faint DSO, for instance. Many are large and a large FOV hasn't been a strong suit of any Mak I have seen. Others are small or tiny and can benefit from the larger apertures that Newts, particularly Dobs, provide at much lower costs. That is because a larger aperture yields higher magnification at a given exit pupil than a smaller aperture and a brighter image at the same magnification as a smaller aperture.

 

Your assumption is not incorrect but neither is it completely correct in all cases. Sure there are other factors involved. A major weakness of most yt videos is how they present conclusions inadequately qualified or explained. Presenting an overarching factoid as a core principle is not wisdom, conventional or rare. It should be reason for caution.

 

Equal exit pupils should present equally bright images.

 

Here's some reference arithmetic that can help show the relationships between magnification, exit pupil and true field of view:

MAGNIFICATION  =  SCOPE FOCAL LENGTH / EYEPIECE FOCAL LENGTH

EXIT PUPIL  =  EYEPIECE FOCAL LENGTH / SCOPE FOCAL RATIO

TRUE FIELD OF VIEW  =  (EYEPIECE FIELD STOP DIAMETER / SCOPE FOCAL LENGTH) x 57.3

 

A while we're at it here's what is IMO the reference website for optical questions including regarding scope designs  -  https://www.telescop...BLE_OF_CONTENTS

[ShaulaB]

Maksutovs tend to max out at 7 inches aperture. A beginner reflector telescope these days is a 10 Dobsonian. So there's that.

[gnowellsct]

Modern newtonians are typically much faster than modern commercial Maks. It's possible to buy a Mak at about f/7 and a Newtonian at f/10.

In that situation you could view at a lower magnification in the maksutov than in the Newtonian. Generally the lower magnification is going to be brighter and so for open clusters and fairly large galaxies like m33 or m101 you might feel a preference for the lower magnification view, given everything else equal.

At equal magnifications and equal apertures that won't be an advantage either way.

There are situations where the advantage is with the higher magnification at least up to a point. At higher magnifications a small Galaxy like ngc1 and 2 which are a pair, these small galaxies are magnified and therefore they trip more cones on the retina and therefore you get a better view. So that's the basic answer. Small faint objects need more magnification to trip more cones and the Maksutov is typically very good at that.

And some deep sky objects are very friendly to magnification. M57, m13, m27 are all examples.

[gnowellsct]

The formula for magnification

Where the eyepiece has the same focal length as the scope, the diameter of the objective in millimeters is equivalent to the magnification.

So in a 100 mm f/6 telescope, a 6 mm eye piece yields 100x magnification, or 1x per millimeter. That's the basic fact to remember to keep the formula straight.

For other eye pieces divide the focal ratio by the millimeter of the eyepiece and multiply times the aperture.

F/6 / a 3 mm eye piece = 2, times the aperture equals 200. F/6 / 40 mm eye piece it's about 1/6 or or 1/7. 100 / 7 = 14.

This formula relieves you of the tedious chore of calculating the focal length and then dividing by the eyepiece in millimeters.

Furthermore it reveals final information. An eyepiece whose length in millimeters is 1/2 the aperture of the scope always yields 2X per millimeter of aperture and with that and exit pupil of 0.5. this is pretty much a definitional boundary of highest possible magnification and is a much more efficient calculation. When you get from 1X per millimeter of aperture moving towards 2x per millimeter and beyond, you know you will encounter the phenomenon known as dimming out.

You also can immediately calculate the maximum advisable magnification for an instrument just by doubling the aperture in millimeters. 80 mm scope it's 160 x for a 250 mm scope it is 500x tho experience tells us the sky won't support it.

Greg N

Edited by gnowellsct, 19 April 2024 - 04:34 PM.

[Kitfox]

Let me elaborate on my first post…

 

Everyone here is right, as long as there are no obstructions in ray-traced paths all the way to a, let’s say, 6mm exit pupil. This is not the case on a lot of Mak/Cassegrains, nor many Mak/Newts. A quality Mak has three things the MAY impact large exit pupils:

 

-Significant, sometimes gigantic, baffling (not likely a contributor)

 

-Small secondary (this is a critical design feature)

 

-Loooooong baffle tube  (only on a Cass, of course)

 

Any of the above can intercept part of the off-axis light rays.  This results in vignetting. Not sharp vignetting like a field stop on an eyepiece, but gradated loss of part of the rays as you move off axis.  In a system only obstructed by a sufficiently large secondary and limited baffling to fully illuminate the large exit pupil, a Mak could equal a newt or straight Cass in off-axis illumination. However, Mak designers want high contrast, low scatter images. So aggressive baffling and minimal secondary obstructions are part of many designs. But this does, in reality, chop off (or allow them to reflect off the primary and miss the secondary) a portion of the off-axis rays. This results in a gradual dimming of the image as you move further off-axis. 
 

Afocal imaging of a blue sky with my STF 180mm f/10 and even a 31mm Nagler (3.1mm exit pupil) shows some vignetting. Put a 40 mm on and it is noticeably worse. But acclimate it well, put in a 3.5 Delos and point it at Jupiter?  That is what those genius Russians wanted me to see!

Edited by Kitfox, 19 April 2024 - 04:23 PM.

[gnowellsct]

So aggressive baffling and minimal secondary obstructions are part of many designs.

You are right on the whole but whenever you step out and say Maksutovs have long focal ratios and narrow fields of view somebody comes in and says oh no I have an f/7 Mac with a bigger secondary or meniscus or whatever you want to call it.

But in the usual case the Maks don't do well with two inch eyepieces. I consider that a limitation. And the unusual case a larger Mac with a shorter focal ratio can handle 2 inch eye pieces.

Some people are very fond of their Maks they're not my thing. I've looked through a few and never been interested in buying one.

Greg N

[Dave Mitsky]

In addition to the light loss due to the meniscus lens and its larger central obstruction, an MCT also requires a diagonal, so there is a somewhat smaller light throughput.  However, since most DSOs are rather small in apparent size, its smaller maximum true field of view is not that much of a concern.  (I've been able to observe hundreds of DSOs with a 17" f/15 classical Cassegrain with a maximum TFoV of only 26 arc minutes.)  However, it will make it more difficult to locate objects via star-hopping.

[Sketcher]

And then you pair them with eyepieces that provide the same magnification and exit pupil for both:

1300FL, ~13FR Mak with 32mm eyepiece: 1300/32 = 41x mag, 32/13 = ~2.5 exit pupil

400FL, 4FR Newt with 10mm eyepiece: 400/10 = 40x mag, 10/4 = 2.5 exit pupil

 

Is the Newt still going to provide a "brighter" image? Despite the same exit pupil, magnification and aperture?

The greatest difference in performance between those two telescopes is their widest true fields of view.  All other things being equal, a 500mm focal length telescope is going to have a maximum true field of view that's more than double that of a 1300mm focal length telescope -- and that will make a difference when it comes to:

 

a) observing some of the larger Deep Sky Objects (DSOs) -- fitting them comfortably within one's true field of view.

 

and:

 

b) a less experienced observer's ability to accurately point the telescope at all of those smaller, fainter DSOs.  Having a larger true field of view (especially when it's more than twice as large) gives one more room for error in one's pointing accuracy.

 

On the other hand, most DSOs are going to be small enough that the smaller true field of view of the Maksutov isn't going to matter.  But on the third hand  a few of those larger DSOs really will be much better when framed in a wider true field of view, and at least two of those objects are among the finest DSOs in one's entire night sky!

 

So, in my opinion, the 4-inch f/5 reflector would be a better choice for deep sky purposes -- for the above reasons -- not due to light-grasp differences.  But if the telescope you have is a Maksutov-Cassegrain, it can still be a good telescope for visual deep sky use, especially you have access to a good enough sky (no light pollution, no light trespass, etc.)

 

Years ago, I frequently observed from one of Montana's mountain tops with a friend who used a 3.5-inch Questar (a Maksutov-Cassegrain) telescope.  He concentrated mostly on the observation of DSOs.  So, yeah, a Maksutov can still do quite nicely for the visual observation of most DSOs.

[sevenofnine]

+1 on Sketcher's post...that has been my experience with the 3.5" & 5" Maks that I've owned. Because of the narrower FOV some DSO's are difficult to find if you're using a manual mount. A go-to mount really helps. But when you zero in on the DSO, it's definitely visible. Parts of the Veil for instance looked amazing with an OIII filter but was not easy to find. It would have been easier in a Newt 

[JanSpace]

Thank you for the responses everyone :o from a general understanding of the Maksutov's strengths and limits to answering the specific question itself, I would say this helped a lot

[Jon Isaacs]

This question came up due to repeatedly seeing on forums and in videos that a Maksutov is "not good for faint DSO viewing"

 

So, if you take a Maksutov and a Newtonian with (almost) the same aperture:

Mak: https://www.firstlig...ax-102-ota.html

Newt: https://www.firstlig...-dobsonian.html

 

And then you pair them with eyepieces that provide the same magnification and exit pupil for both:

1300FL, ~13FR Mak with 32mm eyepiece: 1300/32 = 41x mag, 32/13 = ~2.5 exit pupil

400FL, 4FR Newt with 10mm eyepiece: 400/10 = 40x mag, 10/4 = 2.5 exit pupil

 

Is the Newt still going to provide a "brighter" image? Despite the same exit pupil, magnification and aperture? I feel like that shouldn't be the case, but is there something I'm missing there?

 

My current guess for why that phrase is popular is:

It's because it's much easier to get a large exit pupil with even most "slow" Newtonians than it is with Maksutov telescopes, since they are almost always even slower; i.e. you can get a large exit pupil with a much shorter focal length eyepiece on a Newtonian, for a "brighter" view, while Maksutovs are always locked into exit pupils below 3 or 4mm even with 40mm+ eyepieces.

 

Is this a correct assumption, or are there also other factors involved? Sorry if I'm stating the obvious here, I'm just trying to figure out where that piece of conventional wisdom comes from.

 

As others have said, you are understanding the differences correctly.  Sketcher said it nicely, I am just saying what he said in a somewhat different way.  

 

Nonetheless, the devil is in the details.  A 100mm F/4 Newtonian is capable of a 3.9 degree TFoV with a 1.25 inch eyepiece with a 6mm-7mm exit pupil, the 102mm F/13 Mak will provide a 1.2 degree TFoV and a 3mm exit pupil with a 40mm Plossl.  

 

What this means is that the Newtonian is more versatile, you will see a wider range of objects and the objects that will not be visible in their entirety and objects that are best seen in a small scope.  The Pleiades, they are about 2 degrees in diameter, the 102mm F/4 will frame them nicely, the 102mm F/13 will only show a small portion.  The Andromeda Galaxy under dark skies is about 3 degrees across, the Newtonian will show the entire galaxy, the Mak, only part of it.  

 

The difference in brightness should not be ignored either.  A 6 mm exit pupil provides an image that is 4 times brighter.. Faint nebulosity is more easily seen.  

 

If one takes these two scopes out to some dark skies, the Newtonian will be an very good scope for slowly sweeping the Milky Way, the large field of view, the bright image makes some wonderful views.  The Mak just isn't very good at this sort of thing. The field is narrow, the image dim. 

 

The Mak is not without virtues. Compared to the F/4 Newtonian, it will be better at high power views, it will be easier to focus, it will have fewer aberrations, it will be easier on eyepieces.  An F/4 scope is demanding of eyepieces, stars in the center of the field will be sharp but as one moves away from the center, the off-axis astigmatism of affordable eyepieces becomes noticeable and combined with the coma of an F/4 mirror, things get pretty messy in the outer field.. 

 

For a Newtonian, F/5 is preferable to F/4.  There is about half the coma, affordable eyepieces are sharper across the field, things are just more relaxed optically.  The 130mm F/5 Table Top dobs like AWB OneSky are a nice scope for deep sky while also being capable planetary scopes.  A 32mm Plossl provides a 2.4 degree TFoV with a 6mm exit pupil at about 20x.. 

 

https://shop.astrono...ector-telescope

 

Jon

[Freezout]

Many people on this forum repeat that catadioptrics are not good for DSO because of the field of view. Like if all DSOs are as big as Andromeda galaxy.
In fact this will concern only a couple of DSOs.
I find the exit pupil story way more interesting and convincing.

The possibility to use eyepieces with high focal length and long eye relief and still get high power is a good advantage of a Mak.

[aeajr]

I am not as technically rigorous as some of the folks here, but I will share my views.  For context, I have F5 and F7 refractors, F4 and F5 Newtonians, and an F15 Mak.

 

They all get the job done but naturally each has it strengths and limitations.  To me, the only limitation that I concern myself with related to the 127 mm F15 Mak is that it has a more limited field of view range.  My max field of view in my 1.25" focuser is about .85 degrees at about 60X.  I can't go wider or lower than.  If I needed to go wider or lower in power I would choose a different scope.

 

If I wanted to view the Trapezium within the Orion Nebula, the Mak would be a very good choice.  However the Orion Nebula is about 1 degree across, so the Mak could not show it to me in a single field of view.  Sometimes that matters and sometimes it doesn't. 

 

The Mak is an excellent scope where I will be working smaller objects at higher powers, say over 100X.  Examples would be the Moon, planets, doubles stars, and smaller DSOs.  Since the max true field of view on my Mak is about .85 degrees,  I would not use it on something like the Andromeda Galaxy unless I was looking to focus in on a limited part of the galaxy.  This is not because it is a DSO, but because it is over 3 degrees wide.

 

My Mak is on a manual mount, so I want a little space in the field of view to facilitate tracking.  If I am looking at DSOs that are less than 1/2 a degree wide and will be viewed at greater than 60X, there is no reason not to use the Mak on DSOs.

 

My preference is for my 4" F7 ED refractor or my 12" F5 Newtonian/Dob.  This is not because the are better than the Mak, but because they afford me a wider field of view range than the Mak.  I consider my Mak a specialty scope that is used primarily on nights where I will be splitting doubles or viewing the Moon or planets.    

 

A big advantage for the Mak is its small size.  It is easy to take when traveling and it can go on a lighter weight mount.  Its weight is probably close to my 4" ED refractor, but the refractor is physically much longer and so places greater stress on the mount.  When mounted on my Twilight 1 mount the refractor has a much longer settling time when focusing.  The Mak settles almost instantly due to its shorter length.

 

Every optical system is a compromise.  You just have to recognize each one's strengths and weaknesses.  That is why I have a variety. 

Edited by aeajr, 20 April 2024 - 02:00 PM.

[maroubra_boy]

I have 8 scopes, four Newts/dobs 8" to 17.5", two refractors 80mm & 100mm, and two Maks, 127mm & 9". The scopes I most use from home (Bortle 8) are my two Maks, especially the 9" even though the two 8" dobs I just need to pick up, plonk down and start viewing while the 9" Mak requires me to set up a goto mount.

Do I have any qualms about using the Maks with DSOs? Not at all. So I cannot fit the Eta Carina Nebula in the one FOV, BIG DEAL! Is there a licencing requirement that means one cannot view a DSO unless it fits in the one FOV? Because if that is the case then anyone with a big dob is likewise screwed! What, no one moves their scope when viewing a DSO, even if it fills the FOV???

I actually find my Maks the best suited to my urban viewing. Their longer native focal length means they have better contrast straight off the bat. Their greatest strength with DSO's is nailing GC's and PN's as both take magnification really well and an Oiii filter is a boon with PN's. With my niche in astro being sketching, the Maks are the perfect tool for my urban sketching with their compact size coupling aperture grunt with long focal length.

When I go bush, my various Newts are my preferred tools. Without the scourge of light pollution, then lower native magnification is what I exploit.

Others also add the longer cooling period of Maks as being a deal breaker, a kiss of death, an embarrassment. Yet these same people are all living under a rock as the innovation of an insulating wrap now sees Maks have ZERO cooling period while these same turkeys are still waiting for their "God send" of a scope to cool!

It is all about the right tool for the job and what is practical for an individual. If all you can have is the one scope then you need to decide on what best suits your situation, and this is not a simple equation as there are many factors to consider. If you are fortunate to be able to have several scopes, then it is no less a complex equation though with more flexibility. But to outright dismiss any one scope design because of personal bias towards some design or other is just dumb. Maks in particular experience this prejudice namely as a vestige of the Cold War bias against anything with a Russian sounding name - which is most curious as Questars are Maks and are considered as perfection! Yet the same vigour of prejudice is not put to SCT's, DK's, RC's or CC's...

Below are two examples of DSO's nailed with a Mak from under urban skies. Both are part of the sketching marathons I undertook of PN's and GC's.

Understand the strengths and weaknesses of any scope design and you will be able to exploit each to your own advantage.

Attached Thumbnails

• 
• 

Edited by maroubra_boy, 20 April 2024 - 05:06 PM.

[MrsM75]

I have 8 scopes, four Newts/dobs 8" to 17.5", two refractors 80mm & 100mm, and two Maks, 127mm & 9". The scopes I most use from home (Bortle 8) are my two Maks, especially the 9" even though the two 8" dobs I just need to pick up, plonk down and start viewing while the 9" Mak requires me to set up a goto mount.

Do I have any qualms about using the Maks with DSOs? Not at all. So I cannot fit the Eta Carina Nebula in the one FOV, BIG DEAL! Is there a licencing requirement that means one cannot view a DSO unless it fits in the one FOV? Because if that is the case then anyone with a big dob is likewise screwed! What, no one moves their scope when viewing a DSO, even if it fills the FOV???

I actually find my Maks the best suited to my urban viewing. Their longer native focal length means they have better contrast straight off the bat. Their greatest strength with DSO's is nailing GC's and PN's as both take magnification really well and an Oiii filter is a boon with PN's. With my niche in astro being sketching, the Maks are the perfect tool for my urban sketching with their compact size coupling aperture grunt with long focal length.

When I go bush, my various Newts are my preferred tools. Without the scourge of light pollution, then lower native magnification is what I exploit.

Others also add the longer cooling period of Maks as being a deal breaker, a kiss of death, an embarrassment. Yet these same people are all living under a rock as the innovation of an insulating wrap now sees Maks have ZERO cooling period while these same turkeys are still waiting for their "God send" of a scope to cool!

It is all about the right tool for the job and what is practical for an individual. If all you can have is the one scope then you need to decide on what best suits your situation, and this is not a simple equation as there are many factors to consider. If you are fortunate to be able to have several scopes, then it is no less a complex equation though with more flexibility. But to outright dismiss any one scope design because of personal bias towards some design or other is just dumb. Maks in particular experience this prejudice namely as a vestige of the Cold War bias against anything with a Russian sounding name - which is most curious as Questars are Maks and are considered as perfection! Yet the same vigour of prejudice is not put to SCT's, DK's, RC's or CC's...

Below are two examples of DSO's nailed with a Mak from under urban skies. Both are part of the sketching marathons I undertook of PN's and GC's.

Understand the strengths and weaknesses of any scope design and you will be able to exploit each to your own advantage.

 

 

THANK YOU Sir. maroubra_boy. THANK YOU.

 

I agreed with you 100% and I know we all bias with our scopes BUT what people fail to understand is they keep forcing their wide field view on us, I'm sorry but they not me, this is my eyes my retina. I literally don't care wide field, what I care is the long focal length to magnification big the objects I need see. I don't need a f/3 yada wide field that show Saturn as a star, I need to see not just Saturn rings but ALSO Saturn 4 Moons. 

 

I need to see the Whirlpool galaxy as a big fat SNAIL which I need the Mak magnification for that. I don't need to see the wide field  area around Whirlpool, I need to see Whirlpool itself as a big fat snail. btw I see Whirlpool with my Mak.

And another misconception that Mak cannot see DSO right? I will debunk that theory. The newbie me only has Maks, and even with 4-5 inches Maks AND in a Borle 7.8 and in a barely 19 SQM, my Mak still pick up DSO fine. Thank you to it focal length to magnification what I want to see. 

 

Galaxy let see what my Mak can see, and I'm a newbie, with very limited scope and sky. But I can see all these:

 

I see Sombrero galaxy in Virgo, and stumble on another one elliptical galaxy but not sure which Messier number.

 

Andromeda M31 and and M32 and M110

 

I see M81 and M82 in Big Dippers, and stumble on another one oval shape galaxy too but not know which Messier number.

 

I see M51 Whirlpool galaxy.

 

I see the diffuse nebula M1 the Crab nebula

 

I see the Ring, Dumbbell, Saturn Nebula, Trifid Nebula, Lagoon.

 

I see Orion and that Running Man Nebula NGC 1977 conjunction Orion.

 

I see Omega here everynight at 8 degrees altitude, but all I can see is a Big Grey Glow.! but this is not a Mak fault, this is because of my darn sky fault and it super low at 8 degrees altuitude so I'm looking through alot of atmospherre, and SQM 19 and Bortle 8 sky,

 

I see too many way too many Open stars clusters that I not know which Messier or NGC number, way too many open stars clusters to counts. 

 

Now to my favorite, globs, I see alot of globular clusters, M75, M2, M80, M54, M15, M28, M62, M92, M5, M13, M30, M53, M69, M70, M79, M3, M19, M22, M9, M14, M9, M4, M12, M72, M56, M71, M55, NGC 6144

 

They are DSO, M75 and M72 are dark sky globs which M72 at magnitude 9.4 dim

 

And Mak can't see DSO eh? I just debunk that myth, all that above are DSO objects.

 

My point is, use whatever scope fit your eyes and your personality, this hobby is not a competition on which scopes design is better, or who can see more stuff than who, or who has darker sky than who. Work with what you have, as long as you enjoy your scope and enjoy what you see, then it doesn't matter other people see North America Nebula, who cares, it not a darn competition.

Edited by 34degN, 20 April 2024 - 06:17 PM.

[Echolight]

It seems that you want the Mak.

My problem would be that you are willing to spend much more for the Mak and still need a mount.

 

Anyhow, neither a 102 f4 newt or a 102 Mak will be ideal for viewing DSO.

But if you were to jump up in size of the newtonian to match what the Mak plus a mount would cost, you'd be in a little better shape.

 

Aside from the rather small aperture for faint DSO, my biggest problem with the Mak would be the narrow available field of view, making it hard to find and fit many objects in the eyepiece.

Edited by Echolight, 20 April 2024 - 07:14 PM.

[maroubra_boy]

FOV is a function of focal length, not scope design. So why do you have a C8? You obviously will never use it to view M31 as it won't fit in the widest TFOV a C8 can give. Nor view it with your 10" Newt for the same reason.

Here's some blasphemy! M31 sketched using a 17.5" dob, and M31 DIDN'T fit in the one FOV! Straight to Hell for me!

Attached Thumbnails

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Edited by maroubra_boy, 21 April 2024 - 12:59 AM.

[MrsM75]

FOV is a function of focal length, not scope design.  So why do you have a C8?  You obviously will never use it to view M31 as it won't fit in the widest TFOV a C8 can give.  Nor view view with your 10" Newt for the same reason.

 

Here's some blasphemy!  M31 sketched using a 17.5" dob, and M31 DIDN'T fit in the one FOV!   Straight to Hell for me!

 

It funny how bias people can be, I am also bias, but let face the truth too, they complaint Mak is so narrow Fov, but then they think their Refractor Chromatic Aberration is perfectly ok (which I just can't handle chromatic aberration period). And their Reflector Coma and spherical aberration is perfectly ok. 

 

My point is, we all have our own eyes on what fit our eyes, I have zero problem with a Mak narrow fov as long as I can see Saturn 4 Moons, or see the big magnification of Sombrero galaxy. 

 

by the way Sir I remember I read in an article, when it come to telescopes that has "mirror" meaning a Mak, Newtonian Reflector and SCT, scopes that has 'mirror" in it: the Mak, yes Mak will give you the most crisp view. SCT do not have as crisp view as a Mak, and including a Newtonian.

Edited by 34degN, 20 April 2024 - 07:41 PM.

[Keith Rivich]

A scope is a scope is a scope. Look through 10 different 8" scopes of 10 different optical designs and you are going to see pretty much the same thing in all 10. 

[Echolight]

FOV is a function of focal length, not scope design. So why do you have a C8? You obviously will never use it to view M31 as it won't fit in the widest TFOV a C8 can give. Nor view it with your 10" Newt for the same reason.

Here's some blasphemy! M31 sketched using a 17.5" dob, and M31 DIDN'T fit in the one FOV! Straight to Hell for me!

Why didn't you get a 17.5 inch Mak?

 

As to why I have a C8?, for DSO of course.

It's not a 4.

And because it was 20 years old when I got it, so cheap.

Plus I use a reducer corrector, and a 2 inch diagonal with 105mm backspace, and have 1.8 degrees available when I want it with a 28 PWA. 

 

It's more convenient than the 10 inch dob.

If funds allow, I'd recommend it.

 

But if all you can afford is a 4 inch Mak for DSO, I'd rather a 5 or 6 inch newt or however big I could buy for the money,,, up to the point of inconvenience,,, for DSO.

Edited by Echolight, 21 April 2024 - 08:56 AM.

[Jon Isaacs]

It funny how bias people can be, I am also bias, but let face the truth too, they complaint Mak is so narrow Fov, but then they think their Refractor Chromatic Aberration is perfectly ok (which I just can't handle chromatic aberration period). And their Reflector Coma and spherical aberration is perfectly ok. 

 

My point is, we all have our own eyes on what fit our eyes, I have zero problem with a Mak narrow fov as long as I can see Saturn 4 Moons, or see the big magnification of Sombrero galaxy. 

 

by the way Sir I remember I read in an article, when it come to telescopes that has "mirror" meaning a Mak, Newtonian Reflector and SCT, scopes that has 'mirror" in it: the Mak, yes Mak will give you the most crisp view. SCT do not have as crisp view as a Mak, and including a Newtonian.

 

I have three refractors that show no chromatic aberration.  One of those provides wide, flat flat fields.

 

I have Newtonians with premium optics as well coma correctors and eyepieces that are essentially perfect in fast scopes. They have small COs for planetary contrast.

 

So far, the limitations of Maks for deep sky have focused to their narrow field of view. Ed pointed out that his 5 inch Mak is only capable of a 0.85° TFoV, my 4 inch APO does 4.9°, the 22 inch Dob does 1.0°.  For many DSOs that's not a problem but small scopes are best for large objects so it is important

 

The second issue with slow focal lengths is the difficulty achieving large exit pupils. For viewing faint deep sky objects, particularly with deep sky filters, large exit pupils are often advantageous.

 

So it's not that a Mak-Cass cannot be used for deep sky. Rather, it's that other designs offer a wider range of capabilities. Slowly sweeping the summer Milky Way is best done with big, bright, wide fields of view. It's disappointing in a Mak. Objects like the North American Nebula, the California nebulae, these are best seen at large exit pupils with a their wide, bright fields 

 

I've owned a few Maks.. two 5:inches and one 90 mm. If ones first priority is deep sky, they're not scopes I recommend.  If you have one and want to use it for deep sky, by all means go ahead. 

 

Jon