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

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#1 Nate1701

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Posted 30 September 2020 - 10:38 AM

I'm thinking of a ST80 type scope ( possibly Meade Infinity) for grab and go during the Winter. Quick setup with Alt-Az tripod. Not too long in the cold. 

On these forums a 80mm 'frac is such a tried and true setup for quick and easy astro observing. 

A couple points: I wouldn't be using a refractor on planets and the moon - i would use the Mak. The ST80 would be for clusters and faint fuzzies.

I would like to compare the views of an 80mm refractor @ around 30x to 40x with by 25x100 Binoculars on a few clusters.

 

However - if i want 30 to 40x with a 80mm refractor and around 2.5mm exit pupil, I could just buy a 32mm plossl for my Mak?  That would give me 46x. and similar exit pupil. I don't have an Alt-az mount for my Mak, but i could just get one and plop the Mak on it with low power it should be ok for panning right?

 

I don't have refractor experience but i'm thinking the benefits of having an 80mm refractor is:

1. that it would give a wider view at the same magnification because of lower F ratio.

2. Also benefits of no central obstruction?

3. Smaller and lighter for running outside for a bit.

4. More portable that my binos (for low-wide field) since i dont need to setup my P-gram and chair ( but i could do this with the Mak too)

5. A bit more comfortable for low wide field than binos with 90 degree eyepiece over straight through. 

6. more power than Binoculars but less power than a Mak - a nice in-between

 

 

But i'm not sure these benefits are so great that i need to buy another scope. The 127mm on an Alt-az ( with low magnification) could still be enough grab-n-go setup. BUT its not really the tool for a lower power wider field, I totally get that.

I definitely appreciate that each scope type has its best "use case". I don't necessarily want the the lowest-widest field - i could just use binoculars. 

Also the other angle is - if it's the most often used scope - make it nice and buy an ED version? But from what i understand ED is best for bright objects and high magnification - and i would just use the Mak for that.

 

Thanks in advance for any opinions and comments


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#2 Shorty Barlow

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Posted 30 September 2020 - 10:42 AM

I've been looking at Mars at over 200x alternately with my 127mm Mak and 80ED DS Pro Evostar. I prefer the 80ED. 


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#3 Nate1701

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Posted 30 September 2020 - 10:46 AM

I've been looking at Mars at over 200x alternately with my 127mm Mak and 80ED DS Pro Evostar. I prefer the 80ED. 

really wow.

 

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



#4 cookjaiii

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Posted 30 September 2020 - 10:50 AM

The ST80 has nice attributes, no doubt about it.  In your shoes, I would buy a ST80 used (they come up pretty often in the classifieds), try it to see if you like it.  If you don't, you can re-sell it and recoup most of the cost.  Think about it like you are renting it for a while.


Edited by cookjaiii, 30 September 2020 - 10:51 AM.

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#5 Nate1701

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Posted 30 September 2020 - 10:52 AM

The ST80 has nice attributes, no doubt about it.  In your shoes, I would buy a ST80 used (they come up pretty often in the classifieds), try it to see if you like it.  If you don't, you can re-sell it and recoup most of the cost.  Think about it like you are renting it for a while.

That's a good point and would even apply to buying a new one/ 



#6 Nate1701

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Posted 30 September 2020 - 10:53 AM

I also thought of another benefit for cold weather - less worry about cool down times?


Edited by Nate1701, 30 September 2020 - 10:54 AM.


#7 sg6

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Posted 30 September 2020 - 10:55 AM

I wouldn't get the ST as that is f/5 and the image will be "colorful".

ES or Bresser do an 80mm at 640mm focal length being f/8 it should be better. It comes on its own mount - Nano whatever that is like. And at $220 could be a simple one purchase item. You get scope and a manual mount. If you want goto later get the Skywatcher Az GTi and put the scope on that.

 

The 80ED's are as you would expect better unfortunately new they cost more and if you went for used you have to wait for one to appear.


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#8 Mike Lynch

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Posted 30 September 2020 - 10:56 AM

Ah, the continuing debate between getting a Mak or a wider-field refractor!

 

Years go, I bought a 127mm Mak and almost immediatelly didn't like it. I realized I enjoy the wider-field views in a short tube 80 or 90mm refractor.

 

Today I have an 80mm short tube (pulled the lens out of an old Meade ETX 80 and built a more "standard" refractor around it.) that I use for birding in my backyard and grab 'n go wide field astro viewing. Love that kind of liesurely gazing!

 

I also have an ETX 90, used exclusively for planetary viewing. I have recently seen some excellent views of Mars, once the ETX 90 completely cooled down!

 

   The cool-down IS a major issue with Maks!

 

Mike


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#9 Shorty Barlow

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Posted 30 September 2020 - 11:11 AM

really wow.

 

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

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.


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#10 Wildetelescope

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Posted 30 September 2020 - 11:30 AM

I'm thinking of a ST80 type scope ( possibly Meade Infinity) for grab and go during the Winter. Quick setup with Alt-Az tripod. Not too long in the cold. 

On these forums a 80mm 'frac is such a tried and true setup for quick and easy astro observing. 

A couple points: I wouldn't be using a refractor on planets and the moon - i would use the Mak. The ST80 would be for clusters and faint fuzzies.

I would like to compare the views of an 80mm refractor @ around 30x to 40x with by 25x100 Binoculars on a few clusters.

 

However - if i want 30 to 40x with a 80mm refractor and around 2.5mm exit pupil, I could just buy a 32mm plossl for my Mak?  That would give me 46x. and similar exit pupil. I don't have an Alt-az mount for my Mak, but i could just get one and plop the Mak on it with low power it should be ok for panning right?

 

I don't have refractor experience but i'm thinking the benefits of having an 80mm refractor is:

1. that it would give a wider view at the same magnification because of lower F ratio.

2. Also benefits of no central obstruction?

3. Smaller and lighter for running outside for a bit.

4. More portable that my binos (for low-wide field) since i dont need to setup my P-gram and chair ( but i could do this with the Mak too)

5. A bit more comfortable for low wide field than binos with 90 degree eyepiece over straight through. 

6. more power than Binoculars but less power than a Mak - a nice in-between

 

 

But i'm not sure these benefits are so great that i need to buy another scope. The 127mm on an Alt-az ( with low magnification) could still be enough grab-n-go setup. BUT its not really the tool for a lower power wider field, I totally get that.

I definitely appreciate that each scope type has its best "use case". I don't necessarily want the the lowest-widest field - i could just use binoculars. 

Also the other angle is - if it's the most often used scope - make it nice and buy an ED version? But from what i understand ED is best for bright objects and high magnification - and i would just use the Mak for that.

 

Thanks in advance for any opinions and comments

Comparing apples and Oranges.  Each scope design is meant to do something different.  What do you want to look at more?  Planets or wide field scanning.  The real answer is that they are complimentary.   If you already have the mak, you will loose nothing and benefit from picking up an ST 80 for wide field panning and scanning.

 

 If properly collimated(they usually come that way and stay that way)  and allowed to equilibrate to the surrounding temperature, the 5 inch mak should trounce a 3 inch refractor in terms of light gathering on DSO's and detail on planets and the moon. 2 inches of additional aperture  is a big deal at that scale of scope.  However, the field of view is limited compared to what is attainable from the ST80.  If you live in an area with truly dark skies, then the 80 mm scope would really be impactful and an addition to your Mak.  On planets, the Mak should simply rule. Even compared to an ED 80 mm refractor.  There is that much difference in resolution and light collecting area.  

 

Maks do cool down slower, but for a 5 inch Mak, this is much less of an issue.  Just need to let it sit out in the shade for 30 minutes to an hour, and you should be good to go(this is what I do with my 6 inch mak and it works).   It is true that the Refractor will be faster Cooling down, but if you want to look at planets or the moon, the wait is worth the advantage you will get.  

 

The ST80 refractor will handle 2 inch eyepieces without restriction, and can give you up to a 5 degree apparent FOV.   That is HUGE!.   In theory, you can put a 2 inch visual back on your Apex and use 2 inch eyepieces as well.  However, at some point you will see some vignetting as you go to longer focal length eyepieces.  The most I was able to coax out from my 6 inch Mak was ~ 1.3 degree or so Apparent FOV with a 35 mm Panoptic and just a touch of vignetting.    VERY different than in my what I get with my 80 mm F6 triplet, which is 5 degrees with a ~6 mm exit pupil (according to my Astroaide app:-). 

 

Hope this helps.  I would say if you want to try the ST80, do so.  It will compliment your current scope very nicely.

 

Cheers!

 

JMD


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#11 jeffreym

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Posted 30 September 2020 - 11:33 AM

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


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#12 Hesiod

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Posted 30 September 2020 - 11:37 AM

You may think to the ST80 as a smaller version of your 25x100.

The ability to change magnification is those refractors' best asset over conventional binoculars, while are much cheaper and less bulky than angled binos with interchangeable eyepieces; on the other hand, the field curvature is very apparent, so may end up not much pleased by their huge fov, and therefore a cheap second hand 80ST is IMHO better than a small APO to give it a try.

However I noticed you already own the canon 15x50IS, so the role of an 80mm refractor for widefield scanning is much more questionable, except for the fact that the refractor can easily mount nebular filters (and need just one instead of a couple of them); also, to observe at 40-50x I would prefer the 5" MCT


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#13 Brent Campbell

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Posted 30 September 2020 - 12:35 PM

Simple answers. The ed 80 will have a wide field of view because of a shorter fl and no worries about the size of the secondary.


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#14 Nate1701

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Posted 30 September 2020 - 01:27 PM

Comparing apples and Oranges.  Each scope design is meant to do something different.  What do you want to look at more?  Planets or wide field scanning.  The real answer is that they are complimentary.   If you already have the mak, you will loose nothing and benefit from picking up an ST 80 for wide field panning and scanning.

 

 If properly collimated(they usually come that way and stay that way)  and allowed to equilibrate to the surrounding temperature, the 5 inch mak should trounce a 3 inch refractor in terms of light gathering on DSO's and detail on planets and the moon. 2 inches of additional aperture  is a big deal at that scale of scope.  However, the field of view is limited compared to what is attainable from the ST80.  If you live in an area with truly dark skies, then the 80 mm scope would really be impactful and an addition to your Mak.  On planets, the Mak should simply rule. Even compared to an ED 80 mm refractor.  There is that much difference in resolution and light collecting area.  

 

Maks do cool down slower, but for a 5 inch Mak, this is much less of an issue.  Just need to let it sit out in the shade for 30 minutes to an hour, and you should be good to go(this is what I do with my 6 inch mak and it works).   It is true that the Refractor will be faster Cooling down, but if you want to look at planets or the moon, the wait is worth the advantage you will get.  

 

The ST80 refractor will handle 2 inch eyepieces without restriction, and can give you up to a 5 degree apparent FOV.   That is HUGE!.   In theory, you can put a 2 inch visual back on your Apex and use 2 inch eyepieces as well.  However, at some point you will see some vignetting as you go to longer focal length eyepieces.  The most I was able to coax out from my 6 inch Mak was ~ 1.3 degree or so Apparent FOV with a 35 mm Panoptic and just a touch of vignetting.    VERY different than in my what I get with my 80 mm F6 triplet, which is 5 degrees with a ~6 mm exit pupil (according to my Astroaide app:-). 

 

Hope this helps.  I would say if you want to try the ST80, do so.  It will compliment your current scope very nicely.

 

Cheers!

 

JMD

Thanks JMD. Good points. very helpful.

Complimentary is my goal, i just want to make sure it is "more compliment and less overlap", i.e. two tools doing a similar job. 

My skies are not really the darkest ( i don't know the Bortle number, im just 20 min outside the edge of Toronto area), and i'm not looking for the widest view and largest exit pupil. 

BUT the wider views and lower mag will work better on an alt-az was my thinking, which means a lighter tripod, easy searching, quicker finding targets, less vibration amplified etc.

Mostly i just wanted a bit more portable and quick but statisfying.

For any planetary I would definitely pick the Mak every time. I wouldn't expect an F5 to compete. 

 

Thanks


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#15 Nate1701

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Posted 30 September 2020 - 01:34 PM

I've been looking at Mars at over 200x alternately with my 127mm Mak and 80ED DS Pro Evostar. I prefer the 80ED. 

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 ? 



#16 Wildetelescope

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Posted 30 September 2020 - 01:52 PM

Thanks JMD. Good points. very helpful.

Complimentary is my goal, i just want to make sure it is "more compliment and less overlap", i.e. two tools doing a similar job. 

My skies are not really the darkest ( i don't know the Bortle number, im just 20 min outside the edge of Toronto area), and i'm not looking for the widest view and largest exit pupil. 

BUT the wider views and lower mag will work better on an alt-az was my thinking, which means a lighter tripod, easy searching, quicker finding targets, less vibration amplified etc.

Mostly i just wanted a bit more portable and quick but statisfying.

For any planetary I would definitely pick the Mak every time. I wouldn't expect an F5 to compete. 

 

Thanks

Great.  The next question is how much do you want to spend?  If low mag sweeping is your goal, then it is hard to be the price of the ST80.  For about 4 times the cost(new), you can get a very nice 80 mm ED scope that you might find a bit more versatile.  If you have a good Alt az mount, then you should be able to pan around and look at things up to 200X with no problem, with either the Mak or refractor.  Best of Luck!

 

Cheers!

 

JMD



#17 Shorty Barlow

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Posted 30 September 2020 - 01:56 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 ? 

You can't compare refractors with reflectors. Even with a greater resolving power (R = 11.6/D D in centimetres, R in arc seconds) the Mak' can only effectively magnify to 127x. Anything over 127x will be bigger but will show no more detail than at 127x. So, that's 47x times greater than the 80mm aperture.

 

Anything over 250x, other than the Moon, is ambitious this time of the year where I live. 

 

A refractor will much more easily achieve 70x ~ 80x per inch aperture than a reflector. 

 

It just does it sharper, with more contrast.


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#18 TareqPhoto

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Posted 30 September 2020 - 04:14 PM

ST80 was my first ever scope, and 180mm Mak was my second imaging/visual scope, so i don't need to compare anything, and i bought a Newt same time of me getting the Mak, so now i got used for few different types, guide scopes are just refractors as well, but i am really thinking about going a dob way for visual, and i already ordered my first APO refr for imaging, i want to be set/done within 1-2 years i hope.



#19 Jon Isaacs

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Posted 30 September 2020 - 04:37 PM

You can't compare refractors with reflectors. Even with a greater resolving power (R = 11.6/D D in centimetres, R in arc seconds) the Mak' can only effectively magnify to 127x. Anything over 127x will be bigger but will show no more detail than at 127x. So, that's 47x times greater than the 80mm aperture.

 

Anything over 250x, other than the Moon, is ambitious this time of the year where I live. 

 

A refractor will much more easily achieve 70x ~ 80x per inch aperture than a reflector. 

 

It just does it sharper, with more contrast.

 

scratchhead2.gif

 

I'm not a Man guy but 127x?  Something ain't right. I had a 127mm Starmax. It wasn't a match for my 120mm ED refractor but it certainly managed 200x, 300x...

 

An ST-80 plus a 127 Mak is a nice combination.  An 102 mm F/7 ED doublet is a one scope solution that is better than either one on most targets.

 

Jon


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#20 Shorty Barlow

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Posted 30 September 2020 - 05:26 PM

scratchhead2.gif

 

I'm not a Man guy but 127x?  Something ain't right. I had a 127mm Starmax. It wasn't a match for my 120mm ED refractor but it certainly managed 200x, 300x...

 

An ST-80 plus a 127 Mak is a nice combination.  An 102 mm F/7 ED doublet is a one scope solution that is better than either one on most targets.

 

Jon

You're skim reading these replies again Jon. Technically it will give 127x for a 1mm exit pupil. As far as I know the resolution of a 127mm aperture basically limits it to a resolving power of 127x. You can increase the magnification of course, but you can't really increase the resolution limit. 

 

The 127 Mak resolves better than the 80ED as it is a larger aperture. My point is that 240x in both scopes can be achieved, but although the larger aperture of the Mak gives a slight improvement with resolution, it is offset by the better contrast and sharpness of the smaller refractor. 

 

It's a bit 'swings and roundabouts' as we say, but I tend to prefer a smaller refractor over a larger reflector.


Edited by Shorty Barlow, 30 September 2020 - 05:27 PM.

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#21 barbie

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Posted 01 October 2020 - 08:40 PM

I've had both Maks and small refractors, both achromatic and apo and prefer my small Apo over a small Mak because of my climate and locale, typical seeing conditions, etc. I can go from 13X for wide angle viewing incremementally to 200X plus on the moon, planets and doubles with a mere switch of an eyepiece. My scope( a Skywatcher Evo 72 ED Apo) has a beautifully figured objective and excellent mechanicals and internal baffling/blackening of the tube interior and delivers excellent views of the brighter deep sky objects, doubles, moon and planets. It doesn't leave my wanting for more aperture or anything else for that matter. It thermally acclimatizes quickly and is ready to go on a moment's notice with no hassle setup and transport. Contrast  is excellent and it's lightweight for these old, worn out bones!!


Edited by barbie, 01 October 2020 - 09:26 PM.

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#22 gnowellsct

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Posted 01 October 2020 - 09:28 PM

 

 that it would give a wider view at the same magnification because of lower F ratio.

 

Thanks in advance for any opinions and comments

No that's a conceptual mistake.

 

It's an error probably all of us have made at some point.  But it's a point to be emphasized given how easy it is to fall into it.

 

At equal magnifications fields of view are identical.  (assuming the oculars have the same apparent field of view)  This is ALWAYS true.  A wide field scope is a *low magnification scope.*  At 100x with a 70 degree eyepiece your f/4 Dob Newt has EXACTLY the same field of view as my f/11 C14 at 100x with a 70 degree eyepiece.   Run the numbers.

 

Now, there is the issue of the eyepieces.  Maks very typically have 1.25 inch focusers because they have a small meniscus and a long focal length (optimizing for planets).   A refractor often will be able to accommodate two inch eyepieces.   Now in a 1.25 inch 32 mm plossl you'll have a 50 degree apparent field; and in a 40mm plossl you'll have a 43 degree field, and in a 24 Pan Optic you'll have a 68 degree field.  If you work the math you'll see they're all pretty similar in field of view (but different exit pupils, hence magnifications).

 

The question is: will your ST have a 2" focuser?  I see that the Orion ST 80mm is f/5 and an achromat and has a 1.25" focuser (also Meade 80).  It is perhaps the case that they don't get into 2" format because of other concerns (such as reducing spherical aberration).   I'm thinking 2" focuser is not common in these scopes at this price point.  

 

To get an idea how much difference that makes, consider an ST80 with a 32 mm plossl

 

400mm focal length, 400/32=12.5x. Apparent field of the 32 mm plossl is 50 degrees.  50/12.5= 4 degree total field.

 

Compare to Vixen SD81s which costs about 9 times as much.  f/7.7.  FL= 7.7*81=624.  But you can use a 2 inch 70 degree 40 mm eyepiece.

 

624/40=15.5x  so field of view = 70/15.5 = 4.5 degree field of view.

 

So the Vixen wins on wide field even though it has a longer focal ratio (and focal length) and a higher magnification (15.5x vs 12.5x), all because of its wider two inch focuser and diagonal.  (and it is also excellent at high magnifications on planets, if one is inclined to view planets in 80mm)

 

What is the lesson?  If you really want wide field of view try to get a scope built with a two inch focuser in mind.

 

However, the ST80s go for $100 to $150.  For the price they can't be beat.  I wouldn't want one.  But they are working telescopes and for the price they can't be beat.  And if the cat or dog knocks it over no worries.

 

If you have the funds and really want wide field, take the time and try to find either

 

80mm fast achromat with 2" eyepiece

80mm ED telescope with 2" eyepiece

 

The Vixen SD81s has a loyal following on CN refractor group but there are other options.  But you might be getting into the $500 range instead of the $150 range.  Be sure to run the numbers on calculating true field of view and the eyepieces you intend to use as well as focal ratio, aperture, and size of focuser.  

 

Greg N


Edited by gnowellsct, 01 October 2020 - 09:29 PM.

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#23 Abb

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Posted 01 October 2020 - 11:16 PM

I've got an ST80 and a 102 Mak and love them both! However they each serve a different purpose. Like previously mentioned, the ST80 is for wide field viewing like clusters. My 102 Mak, and this would apply to the 127 Mak as well, are narrow field scopes great for the moon, planets and doubles. I have both permanently mounted on tripods. Also, the lenses that came with these scopes are in a "sock drawer" as I have good lenses and that makes a lot of difference.

 

Abb


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#24 ABQJeff

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Posted 02 October 2020 - 12:41 AM

An ED80 will not give as wide field of views as the ST80. HOWEVER, you also won't get CA and will have an easier time finding EPs that work (f/5 scopes can be picky on EPs, thus gets things like "beaning").   Also Daystar Quark solar filters prefer ~f/6 or slower refractors (if solar is a possibility).

 

So you will have to decide, what objects are you doing and what field of view do you really need.  

 

If seeing star fields (like Double Cluster in Perseus, M45, etc.) crisply and without added color is your thing, go with an ED.

 

The f/7.5 600mm FL Evostar or Orion ED80 will give about 2.9 degrees without any CA and you can use your pick of EPs, inexpensive ones will work fine.  And if you want wider, can always go to 2" EP (and all set for solar).

 

If you really need 4 degrees with 1.25" EPs, are looking primarily to view nebula, galaxies or globular clusters, which will be hazy/whispy by their nature, and are willing to buy Pentax, TV, or ES eyepieces, especially for brighter targets, then go with the ST80 (and can get a semi-apo baader filter to control the CA if it is bothersome).

 

Now, not to throw you off, if you decide you are going the achro route, have you thought of a 120ST?...gets you more aperture, still f/5 so still get as wide a field of view as an ED80, less expennsive than an ED80, and it is only 6 lbs so also can be put on light weight mounts.  Currently I am thinking that may become my future low mag, nebula/"Milky Way sojourning" scope mounted on a VersaGo II (or Vixen Porta II) mount.

 

RE: focuser comment above, on both the ST80 or 120ST it is very common to do the GSO dual speed focuser upgrade.  Gets you 2" capability with the ST80, uses compression rings (stock versions are set screws only), it is a better focuser mechanism, and has capability to hold two finder scopes.  I did this on my ED80.

 

BTW, my 150mm Mak outperforms my ED80 on everything...in its field of view.  And that is the rub, I can easily put all the Pleiades and all of M31 (that I can see) in my ED80 which has its own "WOW" factor, I can't do that in the Mak. But as mentioned above nothing splits a double star, gives views of Mars or sees smaller DSOs like a good Mak and that also has its "WOW" factor.

 

Here's to the Mak and Frac combo!!

 

ABQJeff


Edited by ABQJeff, 02 October 2020 - 12:32 PM.

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#25 Jon Isaacs

Jon Isaacs

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Posted 02 October 2020 - 01:15 AM

You're skim reading these replies again Jon. Technically it will give 127x for a 1mm exit pupil. As far as I know the resolution of a 127mm aperture basically limits it to a resolving power of 127x. You can increase the magnification of course, but you can't really increase the resolution limit. 

 

The 127 Mak resolves better than the 80ED as it is a larger aperture. My point is that 240x in both scopes can be achieved, but although the larger aperture of the Mak gives a slight improvement with resolution, it is offset by the better contrast and sharpness of the smaller refractor. 

 

It's a bit 'swings and roundabouts' as we say, but I tend to prefer a smaller refractor over a larger reflector.

 

I read your entire post. It's just that what was written is incorrect. This is what you wrote:

 

"You can't compare refractors with reflectors. Even with a greater resolving power (R = 11.6/D D in centimetres, R in arc seconds) the Mak' can only effectively magnify to 127x. Anything over 127x will be bigger but will show no more detail than at 127x."

 

A 1mm exit pupil does not result in the maximum resolving power.  Consider double stars, a common measure of resolving power.  No one splits Dawes limit doubles at a 1mm exit pupil. 

 

Jon


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