1364 replies to this topic

[quilty]

My new 3" frac: f/3.7 doublet short (Benriach 12 yo whisky) paper tube powered by gaffertape

Edited by quilty, 03 May 2025 - 06:56 AM.

[VA3DSO]

My new 3" frac: f/3.7 doublet short (Benriach 12 yo whisky) paper tube powered by gaffertape

3in.JPG

Love it! Many years ago I put the 80mm objective and focuser from an Orion Short Tube 80 into a canister for 12 yr old Glenfiddich (the canisters were round back then) and I called it the Single Malt Refractor. I wish I had a picture of it.

[quilty]

The single malt frac on earth :-) Already fixed the lens to the tube professionally, searching for the end reduction to take the diagonal.

Maybe a 2" Baader BBHS?

Just found out it seems to like Plössls. The Bresser 26 mm does well though I'd prefer like 15-20x and +60° AFOV

Ordered a 20 mm Plössl

Edited by quilty, 03 May 2025 - 08:05 AM.

[jcj380]

OK, this is more of a newbie question...

I live in a Bortle 7/8 area, suburb of relatively large city. I have an old 80ST (my first telescope), as well a 90mm Svbony SV48P [...] I've been thinking of getting an 72mm ED refractor - but would ED make a difference for wide-field visual use? 

I'm B8/9 whatever, it's a mess.  Anyway, I have a Meade ST80 achro, an AT72EDii, and an AT60ED.  One thing I notice is that the EDs do a much better job on double stars and lunar detail.  The EDs are just generally sharper / crisper to my eye.

 

The EDs do ok on wide field, but maybe you don't need / want to spend the extra $$ on an ED.  To my eye, the 80 does fine.  

 

If I could only keep one scope, I'd keep the 72ED.  YMMV.  (Well, actually, I'd maybe buy a Borg 90FL, but that's a bit more plata than I have for hobbies right now.   )

Edited by jcj380, 03 May 2025 - 08:50 AM.

[Bomber Bob]

I agree... I feel that a 4 inch refractor is the most practical all around instrument and most of the others are niche scopes to greater or lesser degrees.

 

Rick

Niche to me means single-purpose.  I think my TAK FC-76 F8 is more versatile than that, while my Mizar GT-80S F7 is like my other ACH RFTs, which are limited to specific nights & targets.  All 5 of my TAKs stay sharp at 75x per inch or higher -- my niche refractors can't do that.  The TAKs are limited only by aperture -- but that applies to a lot of scopes.

[revans]

Niche to me means single-purpose.  I think my TAK FC-76 F8 is more versatile than that, while my Mizar GT-80S F7 is like my other ACH RFTs, which are limited to specific nights & targets.  All 5 of my TAKs stay sharp at 75x per inch or higher -- my niche refractors can't do that.  The TAKs are limited only by aperture -- but that applies to a lot of scopes.

Still, if most people could only have one scope I have to think they would choose a 4 inch refractor over a smaller one, but there are many people that would want more than a 4 inch aperture.  But as you go beyond 5 inches, larger refractors become increasingly more niche scopes with the possible exception being those in a permanent observatory.

 

Rick

[kasprowy]

Following up on my earlier post, I have the ST120 out with the SVBony 26mm. Just watched the Moon occult Asellus Borealis (Gamma Cancri), with Mars and the Beehive in the same field of view. A really nice sight, one for the memories. I can lift this setup with one hand.

Edited by kasprowy, 03 May 2025 - 09:30 PM.

[Jon Isaacs]

Well, I think everyone knows that 12"-16" Dobsonians have the potential resolution advantage over 4" refactors. But this thread is about the joy of a "small" refractor NOT the joy of a "large" Dobsonian. 

 

If we stick with small refractors, the gain in light gathering and resolution percentages increases noticeably with every inch of aperture – precisely because one-inch is a huge percentage gain when you are talking about 3" to 4", where 4-inches is the total. The percentage gain in resolution and light gathering per-inch is 25%. But one-inch is a very small percentage gain when the total is 16-inches. There, the percentage gain "per-inch" is only 6.25%.  

 

When you use a 70-80mm refractor you are giving up around 25% of the resolution and light gathering capability of a 4" refractor. And if that 4" refractor can ride on the same mount as a 70-80mm refractor and can be taken on an airplane and has superb optical quality then I'll take that 4" over the 70-80mm size. If I want a ultra-wide fields, I'll reach for binoculars. If low power, ultra-wide fields are really a "top priority", those binoculars will be image-stabilized – so no shakes. 

 

Bob  

 

Bob:

 

It's important to keep the context of my comments in mind. 

 

It had been said that 70-80 mm refractors were unsatisfying and that a 4 would provide better planetary views, better resolution.

 

My point was that I find the views of 70 mm-80mm refractors quite enjoyable, quite satisfying. That's because I don't judge them based on what they're not good at but rather what they are good at. 

 

There's no doubt a 4 inch provides better planetary views but planetary views are not a strong point for either 3 inch or 4 inch refractors.  If I want the good planetary views, neither one is my choice.

 

When thinking about going small, one has to use a different paradigm than bigger is better.. 

 

Small is good... What is it that small scopes do better than large scopes?

 

Jon

Edited by Jon Isaacs, 03 May 2025 - 09:56 PM.

[Jon Isaacs]

True, but one could just as easily use a 30mm eyepiece with a 100-degree field of view. Then you would have a Magnification: 17x  and True Field of View: 5.9° and Exit Pupil: 6 mm. That's pretty wide. 

 

If you want a flat field, you can also get a field flattener for that really inexpensive 102mm F5 achromat.  

 

You can add a field flattener and you can use 100-degree eyepieces with that 102mm. But you can't add the extra 25% of light gathering and resolution capability of the 102mm to the 70-80mm size refractor.

 

At least that's my way of thinking. As always, these things get get personal. And others may want to take a different path.

 

Bob 

 

The 30 mm 100° is a 3 inch eyepiece and requires a 3 inch diagonal. The eyepiece weighs over 5 lbs and lists at $1070. The matching diagonal weighs 2 lbs and costs $590. And that doesn't include the cost and weight of a 3 inch focuser.  And I know of no 3 inch visual field flattener, do you?

 

All this to brighten the view over an ST-80 with a 2 inch focuser by half a magnitude?  

 

I have an ST-80 with a 2 inch focuser.. and a TSFLAT2 and a 31 mm Nagler.. 

 

Are you planning on upgrading your 4 inch F/5 achromat and spend a cool $2500?

 

A 6° field in a 70 mm or 80 mm under dark skies is plenty good enough for me. The important part, the dark skies.

 

Jon

Edited by Jon Isaacs, 03 May 2025 - 10:19 PM.

[bobhen]

The 30 mm 100° is a 3 inch eyepiece and requires a 3 inch diagonal. The eyepiece weighs over 5 lbs and lists at $1070. The matching diagonal weighs 2 lbs and costs $590. And that doesn't include the cost and weight of a 3 inch focuser.  And I know of no 3 inch visual field flattener, do you?

 

All this to brighten the view over an ST-80 with a 2 inch focuser by half a magnitude?  

 

I have an ST-80 with a 2 inch focuser.. and a TSFLAT2 and a 31 mm Nagler.. 

 

Are you planning on upgrading your 4 inch F/5 achromat and spend a cool $2500?

 

A 6° field in a 70 mm or 80 mm under dark skies is plenty good enough for me. The important part, the dark skies.

 

Jon

Yes I should have used the 25mm ES 100 as the eyepiece example but doing so would not change the parameters much at all.

 

Well yes, the view is better in the 102mm than the 80mm, just like the view in the 80mm is better than a 60mm etc. And just like the view is better in a 120mm than a 102mm. And by better, I mean the sacrifice of some field of view for more light gathering capability. At these small apertures, all incremental aperture increases make a difference.

 

Going down from 102mm, if my "top priority" was field of view, I'd rather skip the 80mm and 70mm refractor apertures and "under very dark skies" grab a pair of binoculars. Two-eye viewing at low powers is a real plus. My best ultra-wide field of view of the Milky Way was with binoculars under very dark CO skies – and I had my 80mm F6.6 refractor about 5 feet away and used them both that night.

 

And yes, I agree, dark skies are the key to rich field observing. 

 

Well, I did upgrade the 102mm F5. I purchased a Takahashi 100mm, which is a better all-round general use refractor.  But I kept the 102 F5 because I can reduce it to a very fast F3.5 for use with the image intensifier.

 

Bob

Edited by bobhen, 04 May 2025 - 06:56 AM.

[Bomber Bob]

...  if most people could only have one scope I have to think they would choose a 4 inch refractor over a smaller one  ...

 

Yeah, that's why I have a TAK FC-100 F8, plus a Meade 8" F6 Newt, plus a C8.  If I had to, I could get by with those 3 old scopes, and still have more objects than I could observe in a lifetime.  For folks who are limited to just 1 refractor, I'd recommend getting the very best 4" they can afford.  Ditto for that 1 reflector, and that 1 CAT -- 8" aperture is my current practical limit.  As I get even older, I already have much lighter 130mm versions waiting...

[quilty]

3" frac completed. Supposed to do as finderscope.
Doesn't seem to take more than 20 mm ep (14x)



That way with 1.25" diagonal and ep it's 29 cm long and weighs exactly 1 kg

Edited by quilty, 04 May 2025 - 03:52 PM.

[Terra Nova]

I agree... I feel that a 4 inch refractor is the most practical all around instrument and most of the others are niche scopes to greater or lesser degrees.

 

Rick

I’ll second the 4” as I’ve said many times it’s a one-scope-to-do-it-all. But after my past year with my AT90CFT, I’d say an excellent 90mm will run a good race in the competition!

[John R.]

Last night I pushed my inexpensive (current retail $70) Spectrum 60/500 to what should be silly magnifications. The moon was high overhead and I have just bought an 8mm and 3.2mm AT Paradigm eyepieces. Although intended for use on my AT70 and AT80 I wanted to see what a modern and cheap 60mm could be pushed to, magnification wise. 

Apparently, at least with this sample, the answer is....a lot. 

The 8mm offers up 62x and everything appeared very sharp, right to the edge of the field. Then I switched to the 3.2mm for 156x. Precise focusing was a bit of a chore, but once dialed in the visual was still very crisp, (eye floaters becoming my major issue). With a 'in for a penny, in for a pound' attitude decided to go for broke by screwing the optical component from a shorty barlow for about 1.5X EP mag, or about 235x. Quite dim with a .25mm exit pupil but resolution held up surprisingly well. 

Turning to Jupiter, now only 25 degrees up, results of this experiment were less positive, as expected. On that target the objective reached it's limit at 125x with a 4mm Astromania planetary eyepiece. 

Next, splitting Castor with the 3.2mm presented no problems, with round and even diffraction rings. 

I have always been a bit suspicious of claims here on CN of high quality 60mm refractors such as Takahashi getting pushed to 4x and 5x aperture. But what I observed last night has made me reconsider. 

[Jon Isaacs]

Yes I should have used the 25mm ES 100 as the eyepiece example but doing so would not change the parameters much at all.

 

Well yes, the view is better in the 102mm than the 80mm, just like the view in the 80mm is better than a 60mm etc. And just like the view is better in a 120mm than a 102mm.

 

Going down from 102mm, if my "top priority" was field of view, I'd rather skip the 80mm and 70mm refractor apertures and "under very dark skies" grab a pair of binoculars. Two-eye viewing at low powers is a real plus. My best ultra-wide field of view of the Milky Way was with binoculars under very dark CO skies – and I had my 80mm F6.6 refractor about 5 feet away and used them both that night.

 

And yes, I agree, dark skies are the key to rich field observing. 

 

Well, I did upgrade the 102mm F5. I purchased a Takahashi 100mm, which is a better all-round general use refractor.  But I kept the 102 F5 because I can reduce it to a very fast F3.5 for use with the image intensifier.

 

Bob

 

Bob:

 

Actually, the 25mm 100 degree offers a slightly narrower field of view than the 31mm Nagler.  It does change things quite dramatically.  That is 4.7 degrees in a 102 mm F/5, not the 6.0 degrees offered by the 30mm 100 degree.  

 

And by better, I mean the sacrifice of some field of view for more light gathering capability. At these small apertures, all incremental aperture increases make a difference.

 

 

That is the bigger is better paradigm. That is not what this thread is necessarily about.  In my world, what is important is a wide range of capabilities. I have an excellent 4 inch F/5.4 that provides a wonderful color free flat field as wide as 4.9 degrees.  But I also enjoy wider fields, 5.5 degrees, 6.0 degrees, even wider. 

 

For some objects, more magnification is better, we all know I have the capabilities to gather a lot of light and crank up the magnifications. For some objects, wider fields are better.  That's one reason why I enjoy 70mm and 80 mm refractors,.   This thread is about small refractors.. Sometimes you gotta think small, sometimes you gotta think big.   

 

I have a nice pair of 15x70 binoculars, the Orion Resolux's, they're the same as the Astro-Physics 15x70s.  A 4.4 degree field, not filter compatible, nice for short looks, even with a parallelogram mount and/or a zero gravity chair, I will take a small refractor for just about everything but viewing brighter comets.  

 

I am not a one scope guy.  I like them all.  One scope is like one hammer, one screwdriver... one needs a variety of hammers, a variety of screwdrivers, wrenches etc.  

 

Big scopes for small objects, small scopes for big objects.. 

 

Jon

[bobhen]

Bob:

 

Actually, the 25mm 100 degree offers a slightly narrower field of view than the 31mm Nagler.  It does change things quite dramatically.  That is 4.7 degrees in a 102 mm F/5, not the 6.0 degrees offered by the 30mm 100 degree.  

 

 

That is the bigger is better paradigm. That is not what this thread is necessarily about.  In my world, what is important is a wide range of capabilities. I have an excellent 4 inch F/5.4 that provides a wonderful color free flat field as wide as 4.9 degrees.  But I also enjoy wider fields, 5.5 degrees, 6.0 degrees, even wider. 

 

For some objects, more magnification is better, we all know I have the capabilities to gather a lot of light and crank up the magnifications. For some objects, wider fields are better.  That's one reason why I enjoy 70mm and 80 mm refractors,.   This thread is about small refractors.. Sometimes you gotta think small, sometimes you gotta think big.   

 

I have a nice pair of 15x70 binoculars, the Orion Resolux's, they're the same as the Astro-Physics 15x70s.  A 4.4 degree field, not filter compatible, nice for short looks, even with a parallelogram mount and/or a zero gravity chair, I will take a small refractor for just about everything but viewing brighter comets.  

 

I am not a one scope guy.  I like them all.  One scope is like one hammer, one screwdriver... one needs a variety of hammers, a variety of screwdrivers, wrenches etc.  

 

Big scopes for small objects, small scopes for big objects.. 

 

Jon

I'm not a one scope guy either. I also have a couple of binoculars.

 

For "me," a few extra degrees of field is a secondary priority. On my list of observing priorities, 4.7-degrees versus 6-degrees of field is inconsequential. What matters to me is what's "in the field" and can I see it easily and is there enough image scale to satisfy.  

 

My preference for light gathering over ultra-wide fields probably stems from my use of an image intensifier. The narrow field of the intensifier is many times richer with stars than any wide field binocular of fast refractor view I've had. And with an intensifier, the use of filters adds a lot more contrast than when filters are used visually. That contrast makes objects really stand out. 

 

IMO, objects that are much easier to see are far more impressive than objects that are dimmer or at the limit of detection. And that's what makes the view memorable – not how wide the field is. That's why I like 100mm refractors over 70-80mm refractors. If you point a wide field scope to a point in the sky where there is nothing to see, does it matter how wide the field is? If you point a wide field scope to a point in the sky where there is something to see, wouldn't you want to see those objects brighter and with more contrast, no matter what the field of view was? 

 

These days, my answer to binoculars is my 50mm F3.75 monocular refactor with the image intensifier attached. The 8x view is narrower than binoculars but what's in the view is far more impressive. What would you rather have? Some folks actually use 30-50mm camera lenses with intensifiers for ultra-low power observing.

 

Different preferences and styles of observing for sure. But the end result is a love of what's out there and wanting to see it the best we can.

 

Bob

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[revans]

I'm not a one scope guy either. I also have a couple of binoculars.

 

For "me," a few extra degrees of field is a secondary priority. On my list of observing priorities, 4.7-degrees versus 6-degrees of field is inconsequential. What matters to me is what's "in the field" and can I see it easily and is there enough image scale to satisfy.  

 

My preference for light gathering over ultra-wide fields probably stems from my use of an image intensifier. The narrow field of the intensifier is many times richer with stars than any wide field binocular of fast refractor view I've had. And with an intensifier, the use of filters adds a lot more contrast than when filters are used visually. That contrast makes objects really stand out. 

 

IMO, objects that are much easier to see are far more impressive than objects that are dimmer or at the limit of detection. And that's what makes the view memorable – not how wide the field is. That's why I like 100mm refractors over 70-80mm refractors. If you point a wide field scope to a point in the sky where there is nothing to see, does it matter how wide the field is? If you point a wide field scope to a point in the sky where there is something to see, wouldn't you want to see those objects brighter and with more contrast, no matter what the field of view was? 

 

These days, my answer to binoculars is my 50mm F3.75 monocular refactor with the image intensifier attached. The 8x view is narrower than binoculars but what's in the view is far more impressive. What would you rather have? Some folks actually use 30-50mm camera lenses with intensifiers for ultra-low power observing.

 

Different preferences and styles of observing for sure. But the end result is a love of what's out there and wanting to see it the best we can.

 

Bob

50mm plus image intensifier is not quite enough aperture.  I have  prismless StellaBino 50 binoculars that I use with twin image intensifiers on 15mm eyepieces.  They show a lot more than regular 50mm binoculars but globular clusters still aren't resolved well and still mainly show as fuzzy cotton puffs.  When I put the twin intensifiers on my BT-82 it is a whole different story and you take a quantum leap up from using them on a 50mm setup.  

 

Rick

[Jon Isaacs]

So I have been out at our place in the high desert for much of the period between the third quarter moon and the coming first quarter moon.

 

The skies have gotten darker again and I have been enjoying the views in my Dobs along with the low power wide field views in the WO Megrez 90FD.  Last night, according to ClearDarkSky and Astrospheric, there as some potential for clear skies after midnight.  It was to be my last night in the high desert as friends are coming to visit.. 

 

I went to bed and woke up around midnight.  A quick trip outdoors, mostly clouds with some sucker holes.  1 am, not good.  2 am, some radiation fog.  2:50 am, I look outside, the skies are clear with the Milky Way blazing overhead.  Astronomical dawn begins at 4 am.  I have to get dressed in my warm clothes.. 

 

Do I setup the 16 inch which will take 5-10 minutes or just grab the 90 FD and go with it?

 

I grab the 90mm and some eyepieces and away I go. Skies are about 21.24 mpsas.  I check out M22, along with 6642 and 6638, mag 9 globulars,  M23 and 6645, a mag 10.9 nebula and 6640, a mag 9 globular.  I catch M6 and 7, 8 and 20, 24, 16, 17, 11.  From 11 I catch 6712, a mag 8 globular.  Somewhere in their is 6231.. Off to 6633 along with IC4756, both clusters fit in the same field of view.. 

 

I head off to the Veil and the north American.. M57 and 56, 71 and 27, the double-double.  I finish off with Caroline's Rose. 

 

A lot of stuff for an hour and half and a lot of fun. 

 

The Joy of a Small Refractor.

 

Jon 

[lwbehney]

If I may ask, how is M24 in your 90 mm refractor?  Is the cloud difficult to resolve into stars?

I read in SkySafari that the stars belonging to M24 reside 12,000 to 16,000 light years distant and belong to the Norma Arm. That description in Sky Safari puzzles me, because the Scutum-Centaurus Spiral Arm is both nearer and larger than the Norma Arm, but perhaps the stars mentioned to be 12,000 light years distant are the Scutum-Centaurus Arm and the 16,000 light year distant stars are the Norma Arm. I have not yet been able to find a source to confirm the Sky Safari description. 

[John R.]

That's some list Jon! It does not take near that much to make me happy. From my back yard tonight I was able to split both stars in the double double and that was enough of a thrill. The scope was a SkyWatcher 705, a 70/500 achromat. I was using a Svbony SV188 diagonal plus 8mm AT Paradigm + shorty 2X barlow for 125x.  

Poked around for a bit after that but was exhausted from a hard day of cleanup, both the back porch, back yard, and my shop. All overdue projects. Feel like Basil Fawlty when Sybil is running him ragged.   

Edited by John R., 30 May 2025 - 01:30 AM.

[quilty]

So I have been out at our place in the high desert for much of the period between the third quarter moon and the coming first quarter moon.
 
The skies have gotten darker again and I have been enjoying the views in my Dobs along with the low power wide field views in the WO Megrez 90FD.  Last night, according to ClearDarkSky and Astrospheric, there as some potential for clear skies after midnight.  It was to be my last night in the high desert as friends are coming to visit.. 
 
I went to bed and woke up around midnight.  A quick trip outdoors, mostly clouds with some sucker holes.  1 am, not good.  2 am, some radiation fog.  2:50 am, I look outside, the skies are clear with the Milky Way blazing overhead.  Astronomical dawn begins at 4 am.  I have to get dressed in my warm clothes.. 
 
Do I setup the 16 inch which will take 5-10 minutes or just grab the 90 FD and go with it?
 
I grab the 90mm and some eyepieces and away I go. Skies are about 21.24 mpsas.  I check out M22, along with 6642 and 6638, mag 9 globulars,  M23 and 6645, a mag 10.9 nebula and 6640, a mag 9 globular.  I catch M6 and 7, 8 and 20, 24, 16, 17, 11.  From 11 I catch 6712, a mag 8 globular.  Somewhere in their is 6231.. Off to 6633 along with IC4756, both clusters fit in the same field of view.. 
 
I head off to the Veil and the north American.. M57 and 56, 71 and 27, the double-double.  I finish off with Caroline's Rose. 
 
A lot of stuff for an hour and half and a lot of fun. 
 
The Joy of a Small Refractor.
 
Jon

Guess what happened to me some nights ago. Coming back in the late night, not too much of alc and the sky was bright and beautiful

They were all there, C11, C9 and Skymax6 under the stars ready to use. And I went to bed directly.
No true observer I am.

[Jon Isaacs]

If I may ask, how is M24 in your 90 mm refractor?  Is the cloud difficult to resolve into stars?

I read in SkySafari that the stars belonging to M24 reside 12,000 to 16,000 light years distant and belong to the Norma Arm. That description in Sky Safari puzzles me, because the Scutum-Centaurus Spiral Arm is both nearer and larger than the Norma Arm, but perhaps the stars mentioned to be 12,000 light years distant are the Scutum-Centaurus Arm and the 16,000 light year distant stars are the Norma Arm. I have not yet been able to find a source to confirm the Sky Safari description. 

 

I really didn't spend a lot of time on M24 at higher magnifications.  With a small scope, it's the wide field that's impressive.  I can get nearly all of it in my 12.5 inch Dob.

 

I spent more time on the small globulars and nebulae, I know them well from observing with large apertures and it is fun to eek them out in a small scope. And the NGC6633-IC4756 is a nice pair of open clusters.  Both are visible in a large scope but not as a pair.  IC 4756 is one of my favorite clusters, relatively large but with many stars but no bright stars.. 

 

Jon

[Jon Isaacs]

That's some list Jon! It does not take near that much to make me happy. From my back yard tonight I was able to split both stars in the double double and that was enough of a thrill. The scope was a SkyWatcher 705, a 70/500 achromat. I was using a Svbony SV188 diagonal plus 8mm AT Paradigm + shorty 2X barlow for 125x.  

Poked around for a bit after that but was exhausted from a hard day of cleanup, both the back porch, back yard, and my shop. All overdue projects. Feel like Basil Fawlty when Sybil is running him ragged.   

 

 

There are many nights where the double-double and a few others are more than enough to satisfy me.  Wednesday night, the summer Milky Way was blazing away, it was to be my last night under dark skies until the next new moon cycle.. 

 

Jon

[kmparsons]

Still, if most people could only have one scope I have to think they would choose a 4 inch refractor over a smaller one, but there are many people that would want more than a 4 inch aperture.  But as you go beyond 5 inches, larger refractors become increasingly more niche scopes with the possible exception being those in a permanent observatory.

 

Rick

Some years back, a reviewer with S & T said that if you could only have one telescope (shudder!) a 4" apo would be the choice. That said, over the years the one I have used the most has probably been my 80mm SV FPL-53 triplet with the FT focuser. It cannot be beat for optical and mechanical excellence, ease of use, and portability. lately, I have mostly been enjoying my two 90mm-class scopes, the AT92 and the AT86EDQ, both of which also hit the sweet spot. My largest scope now is my AT115, which is also great but anything heavier and bulkier would be starting to reach my limits on weight and size. I fully agree that anything larger than a 5" refractor is a load. If I get anything that size again, it will probably be a MAK.  

[John R.]

I believe that my ‘personal’ limit for “small” refractor has been reached. However, over the course of this thread that limit has been creeping upward. 
Besides small, I am irresistibly attracted to achromats because; 

1. They are lighter. And. Especially important. 

2. They are cheaper than ED and APO refractors. 
I have managed to snag a Spectrum 90mm x 660mm OTA only for $70 to my doorstep. 

This is a new, out of box unit where the mount, eyepieces, diagonal, RFD, and 2X barlow are not included. If I wanted the whole kit it would have been $170 direct from Spectrum. Of the kit, only the AZ mount is possibly viable, but only for shorter, lighter, OTA’s and it just wasn’t worth the extra C note. 
Here is the unit on an AZ mount made up from SkyWatcher dec bracket bits. 


 

Total length with diagonal at infinity, 29.5 inches. 
Total weight with diagonal + 25mm plossl, 4lb. 2oz. or, for most of the world, 75cm. and 1868gm.

The OTA is only 4.7oz. heavier than my ST80 which to be fair, does have rings and dovetail while this one has a dovetail attached directly to the tube. 

Edited by John R., 05 June 2025 - 08:51 PM.