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Benefits of a 80mm refractor over a 127mm MAK ?

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#51 Escape Pod

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Posted 14 October 2020 - 09:55 PM

Thank you SO much for the thoughtful reply, Jeff. Not only did you help me understand the technical bits. You helped me understand the feeeeelings underneath that explain why we subject ourselves to this weird science.

Actually, I think I’m going to follow you in following Shorty’s advice. In this case, to go the refractor route with the Orion ED80. It seems more promising than the Mak should I graduate to some basic DSO photography. It leaves the door open for a Mak or a big reflector down the road should I decide to see the planets again for the first time at high-magnification. Most of all, the refractor strikes me as a simple, minimalist entre to learning my way around the night sky.

Now to find a good, cheap, alt-az mount to grab and go....

Thank you so much again,

Don
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#52 BillP

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Posted 14 October 2020 - 10:59 PM

When I had my 127 Apex I went to Scopestuff and got adapters so I could use a 0.63x SCT reducer on it.  With a 24 Pan then could get almost 1.5 deg TFOV.  Was quite a treat.  Look at the TFOV difference when  using the 32mm Konig 1.25" (Yellow and Green circles)!

 

127 Mak TFOV copy.jpg
 
 
2117598-ApexSCTadapter.JPG

 


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#53 Miranda2525

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Posted 15 October 2020 - 07:42 AM

med_gallery_249298_10284_284688.jpg

 

The Mak's larger resolution doesn't make up for the sharpness and contrast of the FPL-53 glass in the doublet. Also the image of Mars was much brighter with glaring being a problem. There are ways to ameliorate this but the 80mm refractor doesn't really suffer from this. 

 

med_gallery_249298_10580_667543.jpg

 

The Mak's great for binoviewing the Moon. It's not really as versatile as the 80mm refractor though.

Nice setup!  Looks light 'n' easy for grab 'n' go!



#54 Chuckles34

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Posted 15 October 2020 - 09:27 AM

I know the ease of use and little to no cooldown time of a small refractor has increased my viewing sessions and enjoyment.  I keep my AT80ED on Vixen Porta II with a 7-21mm zoom and 2x barlow by the side porch sliding door.  Popped out last night for 30 mins and checked out nu Dra, mu Dra, eta Dra, 16 Dra, 17 Dra and epsilon Lyrae.  Beautiful doubles.  Perfect wind down to the day before going to bed.

 

Cheers!

 

Chuck    


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#55 MalVeauX

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Posted 15 October 2020 - 09:51 AM

really wow.

 

I guess ED contrast beats out long focal lengths. Glass technology seems to be changing conventional approaches to optics. 

I have an ED80 and a 127mm Mak. I view planets with them nearly daily here in Florida. The 127mm Mak beats the ED80 every single time. The difference is seeing conditions usually. There's no magic to the glass. The refractor's FPL53 and focal length is just trying to produce a color free image (which is gets close to, but not perfect). The Mak's larger aperture gives significantly more brightness, significantly more resolution and is completely apochromatic. The contrast loss from having an obstruction is more than made up for with the significantly larger aperture (if it were merely an inch difference, it would be too similar, but more than a inch, like 2 inches or more, and it is clearly different). The Mak requires collimation and thermal acclimation but it's not too bad. If thermal acclimation is achieved and its well collimated and the seeing conditions are excellent, the Mak will show the higher contrast, higher resolution, brighter view than an ED80 will in the same conditions. There's no magic. Both are good, small scopes. The Mak is better if you have conditions that support the aperture and temperatures. With planetary viewing, seeing is everything. Not magical glass.

 

A 102mm ED/APO would beat both of them for this purpose; significantly higher cost though. Still "ok" to mount these. Bigger than this and you start needing a significantly more robust mount which is another major cost.

 

And a well collimated, thermally acclimated 200mm mirror of any class under supportive seeing conditions will eat all of those small scope's lunch and dinner on a planet. People thinking their magical little scopes do something better other than provide a wider FOV and ignore all the environmental and thermal conditions are just really telling you how bad their seeing conditions are and how impatient they are with the idea of thermal acclimation, let alone all the other stuff. But bottom line again is seeing conditions and temperatures. If you have rotten seeing conditions and you don't have the time to deal with thermal acclimation, then yea, the tiniest refractor is a good instrument for those conditions with respect to planetary viewing. I prefer refractors myself, but there's no magic, just physics, and aperture rules secondary to atmospheric seeing.

 

Very best,


Edited by MalVeauX, 15 October 2020 - 09:59 AM.

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#56 Shorty Barlow

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Posted 15 October 2020 - 11:48 AM

People thinking their magical little scopes do something better other than provide a wider FOV and ignore all the environmental and thermal conditions are just really telling you how bad their seeing conditions are and how impatient they are with the idea of thermal acclimation, let alone all the other stuff. 

 

 

My 80ED DS Pro isn't magical as far as I know. Unless it was constructed by elves, and this isn't generally admitted by Synta, so I'm a bit sceptical. Elves may exist as an ontological construct of course, even so I am not going to dismiss the idea of elven-made telescopes entirely. I'm just a tad sceptical.

 

There's no argument that the 127mm Mak will give a brighter and larger image. That image isn't as sharp and contrasted as the 80ED though. 

 

I live in a small village in the country surrounded by woodland and have a Bortle 4 sky. 

 

At the end of the day, like I stated before, I'm seeing a slightly bigger image with the Mak' but I don't think that the aperture resolution gain of the Mak' allows me to see significantly greater detail than with my 80ED.

 

I also have very good eyesight. 

 

The FPL-53 elves who work for Ohara make a high quality product with an Abbe number of 94.94. My 127mm Sky-Watcher Maksutov cost me less than a new DeLite eyepiece. I think that says it all.



#57 Shorty Barlow

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Posted 15 October 2020 - 11:53 AM

Nice setup!  Looks light 'n' easy for grab 'n' go!

With my disability, nothing's easy for grab and go lol.


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#58 MalVeauX

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Posted 15 October 2020 - 12:30 PM

That image isn't as sharp and contrasted as the 80ED though. 

 

I live in a small village in the country surrounded by woodland and have a Bortle 4 sky. 

 

At the end of the day, like I stated before, I'm seeing a slightly bigger image with the Mak' but I don't think that the aperture resolution gain of the Mak' allows me to see significantly greater detail than with my 80ED.

 

I also have very good eyesight. 

 

The FPL-53 elves who work for Ohara make a high quality product with an Abbe number of 94.94. My 127mm Sky-Watcher Maksutov cost me less than a new DeLite eyepiece. I think that says it all.

This is not supportive of anything other than your opinion however and perhaps an example of your copy variation of your instruments. You keep going on and on about how perfect your small refractor is compared to other instruments that have clear physical advantages and your evidence and argument is simply your anecdotal experience with your particular instruments. We are all very happy that you are enjoying your telescope(s). That doesn't mean it's the correct option for everyone and certainly doesn't lay ground for any sort of evidence based application of telescope selection and use.

 

Sky darkness is irrelevant for planetary viewing. Light pollution doesn't effect planetary viewing. So this additional information does nothing for this argument.

 

You see a slightly larger image with your finer image scale producing 127m Mak, but you don't "think" the resolution and brightness gain allows you to see greater detail than that of a smaller aperture. No physics supports this, other than your sky must have very poor seeing conditions and poor transparency and that's why nothing is having a "gain" over your magical 80mm on a planet in terms of resolution and detail. Seeing is everything. I'm not trying to be harsh or poke fun either, but what you're saying openly in this thread as argument isn't supportive of your idea that the ED80 is better, for you, it's really just exposing the conditions you're doing visual in, unless what you're saying is simply hyperbole in support of your favorite little aperture instrument.

 

Maybe your 127mm Mak is a really awful copy. Maybe your ED80 is an exceptional copy. But again, all your arguments are just anecdotal and you're going on and on in this thread about small refractors beating out large aperture completely apochromatic instruments like someone selling snake oil instead of using arguments that can be supported by known physics.

 

Anyhow, again, please don't take this as a flame thrower, it was not intended, other than to reply to your rebuttable to my remark above. I'm very happy you enjoy your ED80. I enjoy mine as well. But I will not suggest that it can do things that my 127mm Mak, same as yours, does better and not just from anecdotal experience, by from hard physics. Let alone bigger, better mirrors. This approach perpetuates the idea of magical and mystical properties in refractors which is all too ripe in this forum. And naturally I'm pro-refractors, but not to the point of high fantasy.

 

flowerred.gif

 

Very best,


Edited by MalVeauX, 15 October 2020 - 12:35 PM.

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#59 Shorty Barlow

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Posted 15 October 2020 - 01:43 PM

This is not supportive of anything other than your opinion however and perhaps an example of your copy variation of your instruments. You keep going on and on about how perfect your small refractor is compared to other instruments that have clear physical advantages and your evidence and argument is simply your anecdotal experience with your particular instruments. We are all very happy that you are enjoying your telescope(s). That doesn't mean it's the correct option for everyone and certainly doesn't lay ground for any sort of evidence based application of telescope selection and use.

 

I’ve never ‘gone on’ about how ‘perfect’ my ED80 is. Although I’m still not convinced it’s been manufactured by elves. In my experience with other refractors of around 3” and reflectors of around 5” I find the same phenomenon. I have experienced this for many years. I’m not the only one to experience this either.

 

Sky darkness is irrelevant for planetary viewing. Light pollution doesn't effect planetary viewing. So this additional information does nothing for this argument.

 

I once tried to teach my grandmother to suck eggs. To my surprise, she already knew!

 

You see a slightly larger image with your finer image scale producing 127m Mak, but you don't "think" the resolution and brightness gain allows you to see greater detail than that of a smaller aperture. No physics supports this, other than your sky must have very poor seeing conditions and poor transparency and that's why nothing is having a "gain" over your magical 80mm on a planet in terms of resolution and detail. Seeing is everything. I'm not trying to be harsh or poke fun either, but what you're saying openly in this thread as argument isn't supportive of your idea that the ED80 is better, for you, it's really just exposing the conditions you're doing visual in, unless what you're saying is simply hyperbole in support of your favorite little aperture instrument.

 

I doubt it. I had a good 360x with my 150mm Newtonian on Mars a few nights ago. I can have nights of excellent seeing, not always of course. Unless the elves can help me. Again, you have no evidence that my 80ED is actually magical. I may have to phone Harry Potter about this though. Or Gandalf maybe. Not sure what Gwynn ap Nudd is doing right now.

 

Maybe your 127mm Mak is a really awful copy. Maybe your ED80 is an exceptional copy. But again, all your arguments are just anecdotal and you're going on and on in this thread about small refractors beating out large aperture completely apochromatic instruments like someone selling snake oil instead of using arguments that can be supported by known physics.

 

There is only one indigenous species of poisonous snake in my country. I tend to stay away from them. My argument is a statement. There’s nothing wrong with my 127mm Mak, I’ve used other 127mm Mak’s. I see no difference between them. It's a decent scope for 250 quid. The slight improvement in aperture resolution just doesn’t make up for the sharpness and clarity of the 80mm refractor in my opinion.

 

Anyhow, again, please don't take this as a flame thrower, it was not intended, other than to reply to your rebuttable to my remark above. I'm very happy you enjoy your ED80. I enjoy mine as well.
But I will not suggest that it can do things that my 127mm Mak, same as yours, does better and not just from anecdotal experience, by from hard physics. Let alone bigger, better mirrors. This approach perpetuates the idea of magical and mystical properties in refractors which is all too ripe in this forum. And naturally I'm pro-refractors, but not to the point of high fantasy.

 

It depends what you mean by better, I just prefer the sharper and more contrasted image of the 80ED. That’s where the physics lies; better optics. This isn’t a fantasy. Many would agree with me.


Edited by Shorty Barlow, 15 October 2020 - 01:51 PM.

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#60 barbie

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Posted 15 October 2020 - 02:50 PM

Over the last 20 years, I've had two of the 127mm Maks and can unequivocally say that the images in my small refractors by far have more contrast, especially on Jupiter.  The Maks were just so-so, not bad but not as sharp at the same magnifications that I use with my small ED refractors. I've also been observing long enough to know and see the differences between obstructed and unobstructed telescope optics in SMALL apertures(5" and under). Two years ago, I had a Synta ED100 side by side with a 4" Synta made Mak and the refractor clearly outperformed the Mak on the planets in terms of contrast. While I had the ED100, I compared the views to those of a 5" Synta Mak.  The views in the refractor were much sharper and all of the instruments were thermally acclimated.  The Mak wins on portability and its compact, optically folded light path but the results from the tests I ran much favored the small ED refractors. As with anything related to telescope designs however, these are the tradeoffs one makes when choosing one design or the other. If one is after larger apertures, then the Mak clearly comes into its own, but at smaller apertures 5" and under, I clearly prefer the small ED refractors based on my experiences, climate, local seeing conditions, etc.


Edited by barbie, 15 October 2020 - 02:56 PM.

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#61 Echolight

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Posted 15 October 2020 - 03:48 PM

I like using this Big achro on planets.

181A174F-9BA0-4B20-936A-468F75521942.jpeg

I've been told it sucks....and that I'm color blind. But it's fun to use. And for me, the views aint bad. Aint bad at all.

It's holding a 5mm for 240x and pointing at Saturn or Jupiter in the photo. I'll run it up to 360, 375x on a crescent moon.


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#62 Redbetter

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Posted 16 October 2020 - 04:46 AM

Having frequently used good samples of both types, it is obvious that either your 127 Mak is a poor performer by comparison, or there is some fundamental failure in the way you observe with the Mak.  Take your pick, but that is what the empirical evidence and theoretical considerations indicate based on your statements.   You still haven't provided any descriptions of what is seen in the your 80ED that would match what I see with a 127 Mak, let alone exceed it, so the onus is on you to prove otherwiseInstead, you provide an amusing and telling comment that 127x is it for your Mak...which suggests it is a real dog, perhaps 1/2 wave.  
 
Or perhaps you are ignoring extra detail provided by an otherwise adequately performing 127 for primarily aesthetics reasons: "I just prefer refractors over reflectors."    It is hard to beat a small quality refractor for aesthetic presentation, but when it comes to actual detail...well, it isn't so hard to beat it.
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#63 Escape Pod

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Posted 16 October 2020 - 08:28 AM

Thank you SO much for the thoughtful reply, Jeff. Not only did you help me understand the technical bits. You helped me understand the feeeeelings underneath that explain why we subject ourselves to this weird science.

Actually, I think I’m going to follow you in following Shorty’s advice. In this case, to go the refractor route with the Orion ED80. It seems more promising than the Mak should I graduate to some basic DSO photography. It leaves the door open for a Mak or a big reflector down the road should I decide to see the planets again for the first time at high-magnification. Most of all, the refractor strikes me as a simple, minimalist entre to learning my way around the night sky.

Now to find a good, cheap, alt-az mount to grab and go....

Thank you so much again,

Don

Okay I lied, Jeff and echolight. I’m going for the 150mm Mak as my first one. If I split the binary of all the scope wars on here, it seems highly probable that both Maks and Fracs are really good scopes for a beginner to learn how to “see” with :)

 

I found a used Orion 150mm Mak in the classifieds that comes with the Starseeker IV mount, which I really wanted for the ED80 but didn’t want to pay the “alacarte” price for. He’s also going to sell me a 2” diagonal so I can mount a widefield EP that will hopefully get me started with some of the deep space adventure. Any suggestions there? He recommended a 2” 38mm wide.

 

Any other tips when receiving a new (used) Mak? Checking collimation? A good case to put the scope n for travel?



#64 Escape Pod

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Posted 16 October 2020 - 08:44 AM

Okay I lied, Jeff and echolight. I’m going for the 150mm Mak as my first one. If I split the binary of all the scope wars on here, it seems highly probable that both Maks and Fracs are really good scopes for a beginner to learn how to “see” with smile.gif

 

I found a used Orion 150mm Mak in the classifieds that comes with the Starseeker IV mount, which I really wanted for the ED80 but didn’t want to pay the “alacarte” price for. He’s also going to sell me a 2” diagonal so I can mount a widefield EP that will hopefully get me started with some of the deep space adventure. Any suggestions there? He recommended a 2” 38mm wide.

 

Any other tips when receiving a new (used) Mak? Checking collimation? A good case to put the scope n for travel?

Actually, rereading your posts I see you went with the ED80 as your eyepiece, Jeff. I’ll keep that in mind!

 

ps, I hope you know I was calling myself the “snooty photographer”. You’ve been the opposite of snooty here!



#65 Shorty Barlow

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Posted 16 October 2020 - 11:57 AM

sml_gallery_249298_5348_53240.jpg

 

https://www.astrosho...and-127/p,55897

 

These are perfect for 127mm Mak's.



#66 kim.davis

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Posted 16 October 2020 - 04:07 PM

Here is the case I used to store 150 Mak, should handle 127 Mak easily. Very affordable!

 

https://www.cloudyni...se-for-150-mak/



#67 BillP

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Posted 16 October 2020 - 05:29 PM

I prefer refractors myself, but there's no magic, just physics, and aperture rules secondary to atmospheric seeing.

Excellent post waytogo.gif  One slight embellishment though..."there's no magic, just physics, and aperture rules (with respect to resolution and light gathering only) secondary to atmospheric seeing".


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#68 sojourneyer

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Posted 16 October 2020 - 06:13 PM

I couldn't agree more. There's nothing wrong with any of my reflecting telescopes, I just prefer the crisper, sharper, more contrasted views of a decent ED refractor. 

 

I recently compared my 127mm Mak with my 80ED DS Pro on Mars. The image with the Mak seemed bigger and brighter (glare was a problem), but it wasn't as sharp or as contrasted as the Evostar. I thought the Acidalia Planitia was a bit easier to see, but I don't think the extra resolving power of the Mak gave me significantly more detail (if any).

 

I like my 102mm Mak as it is compact and I can carry it and the AZ5 down my garden in one journey. I tend to use it predominantly for lunar observing and sometimes Mercury/Venus.

 

The 72ED DS Pro gives a sharper image though and on a good night I've pushed it to 210x on the Moon and more recently Mars. 

 

The 102mm Mak copes well up to around 170x and can often do 200x or more. It's a great little portable scope, but it isn't as sharp or as crisp as the 72ED. Regardless of any slight resolution increase. 

 

A good ED refractor can push 70~80x per inch fairly effortlessly on a good night. In my experience a reflector can't do it so well. 

There is another element to the picture, I believe, that no one brought up.  The focuser.

Crayford dual vs Mak focuser


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#69 barbie

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Posted 16 October 2020 - 06:31 PM

Agreed on the type of focuser!!


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#70 sojourneyer

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Posted 16 October 2020 - 07:30 PM

Maybe consider this:

https://celestron.fa...ogitemid=207327

 

I know, it's not the 80mm refractor but the setup is light and portable. Slow motion controls.  The optics of these are very good.  Sell the 114 and buy an 80mm to put on the mount if that turns out to be more what you want.

Have fun.

Jeff

That mount would accommodate an 80 mm but not with diagonal, Zoom and barlow.

It is used on the Omni 102 refractors.. Well, I mean it was used on the now extinct Omni 102 f/6.5



#71 gnowellsct

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Posted 16 October 2020 - 07:32 PM

Personally I find some refractor mysticism going on here.  I have more invested in refractors than many of the refractor devotees on this group. I have refractor bona fides. The refractors have greatly enriched my observing.  I like them.

 

But OMG a 5 inch Mak being outperformed by an 80mm ED?  

 

There has to be some other kind of variable at work.  I have seen my former 9.25 outperform a 15" Obsession under the special conditions of a short observing session and the Newt was not sufficiently cool.  I have seen my C14 outperform a 25" Newt for what must have been a similar reason, unless it was all that sling nonsense in the days before the Glatter sling.  

 

I do remember that there was a time, nearly twenty years ago, when it seemed that Damian Peach was abandoning his C14 for a ten inch Mak from the continent.  He indicated with some rather strong language that the Mak was useless because it never cooled.  (Which by the way is consistent with my experience, C14s cool pretty easily).  So he went back to the C14.  (note that he observes in England and France as well as Barbados).

 

I've never been a fan of Maks, though I see people in these fora who love them.   But I dare say that each and every one of my telescopes, refractors and SCTs, can do a better job on planets than my SD81s (ED81sd).  But the 81 does well enough that it gave me some understanding as to why people might choose to observe that way.  I am prepared to believe that the 127mm Mak has some deficiency--a tube that prevents cooling, or an exceptionally bad figure, or bad internal hardware (that keeps unaligned things that need to be aligned).  Still the idea that the ED glass is the property that allows this small scope to outperform the larger one strikes me as a stretch.    

 

My final thought is that all bets are off if the Mak in question is a mainland export.  In such a case "the variance is wide."  That means that the chances of getting a bad one are pretty high in my book.  Production variance can and does ruin telescopes.  It ruined my 4.25" f/10 when I was a kid.  In adult life I replaced that mirror--found one from the same defunct company that was fantastic--and found out just how good a 4.25" Newt could be.  My 81mm could easily whup that defective 4.25".  I'm don't think it would whup the replacement mirror 4.25" Newt on planets.  The replacement mirror gave me quite the lesson on optics.   

 

But I find I have few really good reasons to venture out with a 4.25" f/10 Newt when I have all these apos around the house.

 

To sum up, there are reasons why a smaller scope might whup a larger one, and do so consistently.   The reason the thesis is encountering resistance here (in my view) is that off-handedly attributing the cause to the ED glass is not going to pass muster.  But there are in fact a number of variables that could put the Mak behind in the comparison. 

 

Greg N



#72 sojourneyer

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Posted 16 October 2020 - 07:32 PM

As i think about it a bit more... 

With my Mak the 'recommended' magnification is around 250x ( 127mm by 2), but i know i could push it to 300 to 350 on a good night. 

That might be one advantage of a Mak over an 80mm ED ? 

 

The 80ED recommended is 160x, and 250x is  maxing it out - which is just where the Mak is getting warmed up. 

 

So with a night of excellent seeing - i would guess the Mak should outperform?

But you own both. 200x on a good night is still limiting the Maks potential. Have you done a head to head when the Mak can take you to 300X ? 

The original post was about an 80mm Achromat and it now shifting to and ED which is more than 4X the cost.



#73 sojourneyer

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Posted 16 October 2020 - 07:44 PM

One of the advantages of small refractors is that they provide full or very nearly fully illuminated views of starfields. This gives the eyepiece view a very brilliant appearance on wide open clusters or rich star fields in the milky way.

At apertures under 8 in lose field illumination so the view at the edge is not quite as bright as at the center. When you get to 5-in and smaller apertures the effect becomes noticeable if you've spent a lot of time with refractors or larger aperture telescopes.

When I rehabbed my 4.25-in Newtonian from my childhood the lack of full illumination was readily apparent to me since I had been using wide field refractors for years at that point. When I was a kid I never noticed it.

It did give me the chance to play with secondary sizing programs and it was very interesting to see that no matter what I did with focal ratio or size of the secondary the problem would not go away.

Varying the aperture does have an effect on field illumination and this forms one of the many reasons to recommend an 8-inch Newtonian over a 6 or 5-in even though the smaller scopes have certain advantages.

I'm with Jon on this one I don't see why one would fret about the difference between an 80 mm refractor and a 127 mm mak when the 100 to 110 mm ED options are sitting there to be had.

I don't consider a 5-in anything to be a planetary scope although there are many factors which might get them recruited to that purpose. I myself look at planets in smaller apertures.

But it can get tiresome in comparison to what an 8-in or larger aperture has to offer.

Heckuva lot of price difference between an 80mm Achromat vs 100-110mmED. Then  you are dealing with mount issues, etc.


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#74 barbie

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Posted 16 October 2020 - 07:55 PM

And the mounting issues are why I have downsized to 70mm-80mm apertures!!


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#75 Echolight

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Posted 16 October 2020 - 08:21 PM

Personally I find some refractor mysticism going on here.  I have more invested in refractors than many of the refractor devotees on this group. I have refractor bona fides. The refractors have greatly enriched my observing.  I like them.

 

But OMG a 5 inch Mak being outperformed by an 80mm ED?  

 

There has to be some other kind of variable at work.  I have seen my former 9.25 outperform a 15" Obsession under the special conditions of a short observing session and the Newt was not sufficiently cool.  I have seen my C14 outperform a 25" Newt for what must have been a similar reason, unless it was all that sling nonsense in the days before the Glatter sling.  

 

I do remember that there was a time, nearly twenty years ago, when it seemed that Damian Peach was abandoning his C14 for a ten inch Mak from the continent.  He indicated with some rather strong language that the Mak was useless because it never cooled.  (Which by the way is consistent with my experience, C14s cool pretty easily).  So he went back to the C14.  (note that he observes in England and France as well as Barbados).

 

I've never been a fan of Maks, though I see people in these fora who love them.   But I dare say that each and every one of my telescopes, refractors and SCTs, can do a better job on planets than my SD81s (ED81sd).  But the 81 does well enough that it gave me some understanding as to why people might choose to observe that way.  I am prepared to believe that the 127mm Mak has some deficiency--a tube that prevents cooling, or an exceptionally bad figure, or bad internal hardware (that keeps unaligned things that need to be aligned).  Still the idea that the ED glass is the property that allows this small scope to outperform the larger one strikes me as a stretch.    

 

My final thought is that all bets are off if the Mak in question is a mainland export.  In such a case "the variance is wide."  That means that the chances of getting a bad one are pretty high in my book.  Production variance can and does ruin telescopes.  It ruined my 4.25" f/10 when I was a kid.  In adult life I replaced that mirror--found one from the same defunct company that was fantastic--and found out just how good a 4.25" Newt could be.  My 81mm could easily whup that defective 4.25".  I'm don't think it would whup the replacement mirror 4.25" Newt on planets.  The replacement mirror gave me quite the lesson on optics.   

 

But I find I have few really good reasons to venture out with a 4.25" f/10 Newt when I have all these apos around the house.

 

To sum up, there are reasons why a smaller scope might whup a larger one, and do so consistently.   The reason the thesis is encountering resistance here (in my view) is that off-handedly attributing the cause to the ED glass is not going to pass muster.  But there are in fact a number of variables that could put the Mak behind in the comparison. 

 

Greg N

Maybe it's the oversized tube that allows better baffling. 




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