123 replies to this topic

[Joe1950]

GS. I don’t know what I’m talking about. 

The older I get, the less I know about more things. Eventually I’ll know nothing about everything.

Ciao, bud.

[GSBass]

Actually your post was the most education I’ve gotten all day... everyone should read it to have a basic understanding, they should pin it to the top of the vast numbers of threads here debating telescopes and numbers

GS. I don’t know what I’m talking about. 

The older I get, the less I know about more things. Eventually I’ll know nothing about everything.

Ciao, bud.

[Joe1950]

That’s very nice of you, GS! Thank you!

[abcdefghii]

For example the 80EDT and 80EDL are $50 apart, and only differ in focal ratio from F/6 to F/7. So it's going to be a tough decision for anyone wanting one or the other.

One is also 480mm the other 560mm.

[2112_Mike]

Yes, it will be fun the compare - visually - my current AT80ED with the new AT80EDL that I just ordered.  

(Based on current shipping ETA's that might be some time from now)

[GSBass]

That will be an interesting review, I suspect they will perform close to the same, although f6 and f7 are very close it would seem from my reading that just about every scope below f6.5 or so has to be a triplet to correct for color.... it just becomes technically impossible to do at faster f ratios without having additional corrective glass

Yes, it will be fun the compare - visually - my current AT80ED with the new AT80EDL that I just ordered.  

(Based on current shipping ETA's that might be some time from now)

Edited by GSBass, 08 April 2021 - 08:36 AM.

[SeattleScott]

Yeah I have seen those representations before. Going from 1/10 to 1/20 was really hard to see. 1/4th to 1/8th was more noticeable, but certainly not dramatic.

Of course with the ED, it won’t have the same level of color correction, so it would tend to lag the EDL on bright objects even if the figure is just as good. In reality a lot of the Chinese stuff is 1/4th, 1/5th, 1/6th. Versus the premium brand stuff is usually 1/8th, 1/9th. So typically a subtle improvement for high power viewing but no real difference for most medium power DSO viewing.

Scott

[GSBass]

We are very fortunate the Chinese have brought this level of quality to the masses, I do have issues on the whole eggs in one basket thing but our hobby has benefited greatly from synta and others, pretty obvious that especially in the world of refractors the cost would be out of reach for a lot of us..... kind of a golden age because I suspect we are pretty close to the bottem as far as pricing goes and close to the top in quality

Yeah I have seen those representations before. Going from 1/10 to 1/20 was really hard to see. 1/4th to 1/8th was more noticeable, but certainly not dramatic.

Of course with the ED, it won’t have the same level of color correction, so it would tend to lag the EDL on bright objects even if the figure is just as good. In reality a lot of the Chinese stuff is 1/4th, 1/5th, 1/6th. Versus the premium brand stuff is usually 1/8th, 1/9th. So typically a subtle improvement for high power viewing but no real difference for most medium power DSO viewing.

Scott

[SeattleScott]

The Chinese (or other mass produced scopes) do offer great value. Typically there will always be some gap with premium brands because mass produced brands compete on price where premium brands compete on quality. For a mass produced brand to produce the same quality, their costs would be too high to compete with other mass produced brands on price. And their reputation as a mass produced brand would make it difficult to compete with premium brands, even if the quality was essentially equal. So you see mass produced brands with a premium line, like SW Espirit, which is their way of saying we are building these scopes to compete with premium brands in terms of quality versus competing with mass produced brands on price. And being made in China, they can still come in significantly under the price of premium brands. Now is Espirit really just as good as Tak or TEC for a bit less money? Or is it a bit less good for a bit less money? Idk.

Scott

[Joe1950]

Don’t know either, Scott.

 

But often if someone who has observed through both scopes, side by side and gives an objective opinion, might say the China export was within 95% of the quality of the domestic premium brand, which still costs more. Or they may say it was very close, but the domestic premium brand held power to a little higher level. Or they may say there was no difference except for the color hue of the object viewed.

 

On the other hand, there are some owners of domestic premium brands who will say their scope was significantly better than the import. Or even that it ‘blew away’ the other scope.

 

I don’t know either how accurate claims are. And since I don’t attend star parties or comparison tests, I probably won’t know personally. And that’s fine.

 

I’ll read the comparison of the AT-102ED/EDL when the fellow’s scope arrives. With interest. And most people are objective with their claims. But some aren’t. Or they see things differently than others. Or they have better vision than I do and see differences that I don’t see.

 

But I do know the difference between a sharp and soft image and between an image with contrast and color and a washed out image. So if I see a sharp image with contrast, I feel very satisfied with the instrument without going over it with a fine tooth comb.

 

It's a slippery slope to be sure. 

[SeattleScott]

Oh yes context is important. I have read reports of 4” Japanese Apos besting SW 120 ED. Obviously not on DSO! Yeah maybe a detectable improvement on Jupiter at 150x or higher but most DSO won’t look as good. In my situation with a 100ED versus my Vixen 103, DSO at 100x magnification looked identical. The only difference was high power lunar/planetary views, and even that was relatively subtle. I will say my 100ED had a less than perfect star test. I’m not good enough to estimate Strehl very accurately based on star test. I just know I could see there was an issue that indicated some sort of correction issue with the lens figure. I’m sure there are better 100EDs out there. But overall it was a fine performer for the price, and compared fine against other mass produced scopes. It just clearly wasn’t quite premium. So you pay a lot to get that extra bit of performance for lunar/planetary.

Scott

[GSBass]

The only comparison you will get from me is with a 7” mak lol.... but I do have a nice televue Barlow so that might be interesting, the refractor should be dimmer and the theoretical resolution will be less however if you do take in to account the better wave accuracy of the refractor and the central obstruction of my mak then they could actually appear close, I’m rooting for my mak though, in my mind my mak will be for everything over 100 and my edl will be for everything under

Don’t know either, Scott.

 

But often if someone who has observed through both scopes, side by side and gives an objective opinion, might say the China export was within 95% of the quality of the domestic premium brand, which still costs more. Or they may say it was very close, but the domestic premium brand held power to a little higher level. Or they may say there was no difference except for the color hue of the object viewed.

 

On the other hand, there are some owners of domestic premium brands who will say their scope was significantly better than the import. Or even that it ‘blew away’ the other scope.

 

I don’t know either how accurate claims are. And since I don’t attend star parties or comparison tests, I probably won’t know personally. And that’s fine.

 

I’ll read the comparison of the AT-102ED/EDL when the fellow’s scope arrives. With interest. And most people are objective with their claims. But some aren’t. Or they see things differently than others. Or they have better vision than I do and see differences that I don’t see.

 

But I do know the difference between a sharp and soft image and between an image with contrast and color and a washed out image. So if I see a sharp image with contrast, I feel very satisfied with the instrument without going over it with a fine tooth comb.

 

It's a slippery slope to be sure. 

[Joe1950]

Ok GS. I thought you had the AT102ED and were getting the EDL.

 

Thats another thing that shows me the over-reliance on things like the Strehl number, star testing, etc. You would be prone to think scopes like a Mak, or SCT, or even a Newt would be terrible performers based on the fact that the central obstruction lowers the suggested performance so much. But it doesn’t work that way in actual use. The scopes with COs perform great in many cases.

 

I think Maks, especially, do a wonderful job on the moon, planets and doubles. If you go head to head with a same size triplet APO, especially one that has a longer focal ratio, the refractor will give a view with better contrast, at least. But the long focal length Maks and SCT seems to lend them to seeing great detail on those targets.

 

And, it illustrates the fact that once you are around the 1/4 wavelength level, improvements are not as much as one may think. Strehl number is one way of gauging the performance of an optical system, but it does not, IMO, tell the complete story. Same with the star test. It can be very misleading.

 

I read an essay by Roland, of Astro Physics. Essentially he said, and I hope I get this correct, that if he were to design and make a triplet APO that gave a perfect star test, and he certainly could, it would not give the best image at focus! He figures his lenses to show the best Airy disc pattern, with as much energy going into the central disk as possible. That, he says, gives the best images.

 

He also made note of a Maksutov and how, ideally, they are corrected with some leve of under-correction. This will also not show a perfect star test, but will give a better in-focus image because the under-correction cancels higher level aberrations caused by the steep sloping optical elements.

 

I am far from competent at the topic of optics. But I do feel you have to judge by what you see, in-focus rather than simply relying on numbers and tests.

 

Someone said that optical testing has ruined more good telescopes than any other cause. 

 

Phew. I’m getting typers cramp! I guess hashing over optics and scope performance keeps us from fixating on some of the dire things happening in the world. Been there, done that.

Edited by Joe1950, 08 April 2021 - 12:42 PM.

[GSBass]

One of my early scopes was a 7” mak and always missed it when I sold it, back in those days and kinda still , I had to sell something if I wanted something else...at that time I wanted a questar, then got aperture fever and sold that for a 10” mak newt, it collected dust mostly and finally went full circle and got a 7” mak again.... it simply makes me happy.... but it is limited to high magnification and that’s where the edl comes in, will be mounting it on a side saddle for a perfect spread from low power wide to high power narrow. As far as aperture fever which we all get from time to time I’m going to round out my set up with one of those Vespera gadgets that come out at the end of the year, basically an automated camera for deep sky, it will be more satisfying to me then wrestling a light bucket again

Ok GS. I thought you had the AT102ED and were getting the EDL.

 

Thats another thing that shows me the over-reliance on things like the Strehl number, star testing, etc. You would be prone to think scopes like a Mak, or SCT, or even a Newt would be terrible performers based on the fact that the central obstruction lowers the suggested performance so much. But it doesn’t work that way in actual use. The scopes with COs perform great in many cases.

 

I think Maks, especially, do a wonderful job on the moon, planets and doubles. If you go head to head with a same size triplet APO, especially one that has a longer focal ratio, the refractor will give a view with better contrast, at least. But the long focal length Maks and SCT seems to lend them to seeing great detail on those targets.

 

And, it illustrates the fact that once you are around the 1/4 wavelength level, improvements are not as much as one may think. Strehl number is one way of gauging the performance of an optical system, but it does not, IMO, tell the complete story. Same with the star test. It can be very misleading.

 

I read an essay by Roland, of Astro Physics. Essentially he said, and I hope I get this correct, that if he were to design and make a triplet APO that gave a perfect star test, and he certainly could, it would not give the best image at focus! He figures his lenses to show the best Airy disc pattern, with as much energy going into the central disk as possible. That, he says, gives the best images.

 

He also made note of a Maksutov and how, ideally, they are corrected with some leve of under-correction. This will also not show a perfect star test, but will give a better in-focus image because the under-correction cancels higher level aberrations caused by the steep sloping optical elements.

 

I am far from competent at the topic of optics. But I do feel you have to judge by what you see, in-focus rather than simply relying on numbers and tests.

 

Someone said that optical testing has ruined more good telescopes than any other cause. 

 

Phew. I’m getting typers cramp! I guess hashing over optics and scope performance keeps us from fixating on some of the dire things happening in the world. Been there, done that.

[vdog]

The only comparison you will get from me is with a 7” mak lol.... but I do have a nice televue Barlow so that might be interesting, the refractor should be dimmer and the theoretical resolution will be less however if you do take in to account the better wave accuracy of the refractor and the central obstruction of my mak then they could actually appear close, I’m rooting for my mak though, in my mind my mak will be for everything over 100 and my edl will be for everything under

I'd be interested to see a side-by-side comparison with a 7" Mak and the SW 120 ED, if only because of this claim in the product description for the 120:  "The superb capabilities of the SW 120ED provide performance on a par with a reflector of perhaps up to 7″ in diameter on lunar, planetary, double-stars, globular star clusters, and depending on your ranking of unobstructed high-contrast as a necessary attribute, even the brighter nebulae may look better to you in a SW 120ED."

 

I considered getting one of those Maks, but went with the 120 instead.  No regrets, just curiosity.

 

And I would assume they are referring to a Mak, as I'm unaware of any commercially-produced 7" Newts, but maybe there are some I'm not aware of.

[GSBass]

Btw, a little off topic but I read about refractors and how they just snap in to focus... it might be because of lower f ratio but I do have a range of focus in my mak that is readily apparent since I do planetary photography a lot...I normally can judge pretty well but sometimes I’m off just a hair and that sucks in post processing. Programs have multitudes of focus assistants but none really work that well, am hoping that eventually someone will write a program that applies rudimentary wavlets to an image on your laptop so you can actually see, yes I’m in perfect focus or no I’m not. I suggested this to both sharpcap and firecapture, there response was great idea but quickly dismissed it due to being one man shows and barely able to keep their apps updated already. Anyway... random thoughts lol

Ok GS. I thought you had the AT102ED and were getting the EDL.

 

Thats another thing that shows me the over-reliance on things like the Strehl number, star testing, etc. You would be prone to think scopes like a Mak, or SCT, or even a Newt would be terrible performers based on the fact that the central obstruction lowers the suggested performance so much. But it doesn’t work that way in actual use. The scopes with COs perform great in many cases.

 

I think Maks, especially, do a wonderful job on the moon, planets and doubles. If you go head to head with a same size triplet APO, especially one that has a longer focal ratio, the refractor will give a view with better contrast, at least. But the long focal length Maks and SCT seems to lend them to seeing great detail on those targets.

 

And, it illustrates the fact that once you are around the 1/4 wavelength level, improvements are not as much as one may think. Strehl number is one way of gauging the performance of an optical system, but it does not, IMO, tell the complete story. Same with the star test. It can be very misleading.

 

I read an essay by Roland, of Astro Physics. Essentially he said, and I hope I get this correct, that if he were to design and make a triplet APO that gave a perfect star test, and he certainly could, it would not give the best image at focus! He figures his lenses to show the best Airy disc pattern, with as much energy going into the central disk as possible. That, he says, gives the best images.

 

He also made note of a Maksutov and how, ideally, they are corrected with some leve of under-correction. This will also not show a perfect star test, but will give a better in-focus image because the under-correction cancels higher level aberrations caused by the steep sloping optical elements.

 

I am far from competent at the topic of optics. But I do feel you have to judge by what you see, in-focus rather than simply relying on numbers and tests.

 

Someone said that optical testing has ruined more good telescopes than any other cause. 

 

Phew. I’m getting typers cramp! I guess hashing over optics and scope performance keeps us from fixating on some of the dire things happening in the world. Been there, done that.

[Joe1950]

That sounds like a great combo, GS! I’m sure you’ll enjoy both scopes for what they do.

 

Where I live, DSO are just not possible. I can only do lunar, planetary and double stars. And with the trees and houses all over the place the available sky is limited also. So I’ll probably get a small Mak and use it on a lightweight mount and use that most of the time. 

 

Sometimes, if the sky is good for seeing, I’ll take the refractor out, or even the C-8. But not as much. Simple, easy, lightweight and quick is very appealing at my age and situation, GS.

[GSBass]

I would guess that is a believable claim in real world use, you would have to have a really good Barlow and my guess is the image may still be a tad dimmer but any refractor that starts to remotely approach 180mm should perform as well... in most cases your starting to surpass the 1k price point though.... and price/performance has to be part of the equation

I'd be interested to see a side-by-side comparison with a 7" Mak and the SW 120 ED, if only because of this claim in the product description for the 120:  "The superb capabilities of the SW 120ED provide performance on a par with a reflector of perhaps up to 7″ in diameter on lunar, planetary, double-stars, globular star clusters, and depending on your ranking of unobstructed high-contrast as a necessary attribute, even the brighter nebulae may look better to you in a SW 120ED."

 

I considered getting one of those Maks, but went with the 120 instead.  No regrets, just curiosity.

 

And I would assume they are referring to a Mak, as I'm unaware of any commercially-produced 7" Newts, but maybe there are some I'm not aware of.

[GSBass]

You might want to research Vespera also... it’s 1500, it’s basically an automated quadruplet redcat, doesn’t have an eyepiece, you just set it and forget it and then look at your photo 30min to 2 hours later, it’s an accumulator though so you can watch the progress on your phone or iPad ....it’s the same company that makes Stellina so the photos are actually good versus evoscope

That sounds like a great combo, GS! I’m sure you’ll enjoy both scopes for what they do.

 

Where I live, DSO are just not possible. I can only do lunar, planetary and double stars. And with the trees and houses all over the place the available sky is limited also. So I’ll probably get a small Mak and use it on a lightweight mount and use that most of the time. 

 

Sometimes, if the sky is good for seeing, I’ll take the refractor out, or even the C-8. But not as much. Simple, easy, lightweight and quick is very appealing at my age and situation, GS.

[Joe1950]

I just searched and read about it. Very interesting. Much less than Selina. But any price of anything with a comma in it is out of reach.   Really amazing some of the automated stuff being produced. Turn it on, dial in what you want to image, go take a nap and check on the progress every so often with your cell phone. I like that.

[vdog]

I would guess that is a believable claim in real world use, you would have to have a really good Barlow and my guess is the image may still be a tad dimmer but any refractor that starts to remotely approach 180mm should perform as well... in most cases your starting to surpass the 1k price point though.... and price/performance has to be part of the equation.

I would expect a 6" refractor with good glass to be on par with the 7" Mak, but I thought this claim for one <5" might be a bit on the hyperbolic side.  It would be interesting to put to the test, though.

 

And, yes, that is the downside of the refractor is needing Barlows and / or shorter eyepieces to get to the magnifications I need for planets.  I have a decent Barlow (an Orion Shorty Plus), but I'm already doing my homework on good 3-4mm eyepieces.

[GSBass]

Btw... know what you mean by limited visibility... all the green is trees so my observing session require lots of waiting for stuff to emerge.... on the bright side everything I can observe is high enough so that I don’t deal with atmospheric blur 😂

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[Mitrovarr]

Thats another thing that shows me the over-reliance on things like the Strehl number, star testing, etc. You would be prone to think scopes like a Mak, or SCT, or even a Newt would be terrible performers based on the fact that the central obstruction lowers the suggested performance so much. But it doesn’t work that way in actual use. The scopes with COs perform great in many cases.

Well, the advantage that the newt or cat always has (in practice anyway) is aperture. So, while you lose something to obstruction and losses on the reflective surfaces, you gain a ton in being a much larger instrument.

I like refractors but people are pretty quick to ignore small aperture as a flaw.

[GSBass]

It’s one reason why I bumped my initial impulse to buy a 80mm up to 102mm, not a huge difference but it does count, the edl is max weight for my secondary saddle so couldn’t have gone bigger. But I mostly just wanted a wide lower power view of things I am looking at through my mak and wanted to at least be able to photograph objects as large as the full moon with my existing cameras

Well, the advantage that the newt or cat always has (in practice anyway) is aperture. So, while you lose something to obstruction and losses on the reflective surfaces, you gain a ton in being a much larger instrument.

I like refractors but people are pretty quick to ignore small aperture as a flaw.