120mm ED latest wisdom

[LewisM]

Originally Posted by alocky

Actually Lewis, it performs well because of its relatively slow f-ratio. Strehl is usually an on-axis measure, and the faster the scope the harder it is to keep under control as you move off axis. That's why the FSQ has 4 elements, and most of the 3 element APOs are a lot faster. Before fluorite glass was available, a flint and crown doublet around 100mm had to be f15 or thereabouts to produce an acceptable fov. That's how vixen killed Unitron!
Cheers,
Andrew.

Thanks for that!

[Richard Gamble (Richard Gamble)]

Why compare apples to oranges?
You certainly do not need to spend 6 grands to enjoy the night sky.
Infact, a humble pair of binos and a good pair of eyes is all you need!

[Kunama]

Originally Posted by Richard Gamble

Why compare apples to oranges?
You certainly do not need to spend 6 grands to enjoy the night sky.
Infact, a humble pair of binos and a good pair of eyes is all you need!

Totally agree but I can also understand why some people want to take it up a notch or two, it has nought to do with showing off. Whether imaging or visual is ones goal, if we were all content to view the heavens through a pair of binoculars there would be a lot of opticians, telescope manufacturers, accessories makers etc out of work.

I think its great that amateurs like us are able to access equipment of the caliber of Astro Physics, Takahashi, Obsession and SDM for a very reasonable price (compared to owning such equipment a few decades ago, when a good scope cost as much as a family home)

If we all settled on a mediocre scope without critical reviews and opinions on forums like this, then that is all the makers would give us.

Having said that I would not think any less of someone who chose to spend less and were content with what they got for their $$$. There are certainly premiums paid for certain logos. A $6000 Tak is not going to be 4 times as good as a $1500 William Optics, nobody expects it to be.

[Profiler (Profiler)]

Originally Posted by Kunama

Totally agree but I can also understand why some people want to take it up a notch or two, it has nought to do with showing off. Whether imaging or visual is ones goal, if we were all content to view the heavens through a pair of binoculars there would be a lot of opticians, telescope manufacturers, accessories makers etc out of work.

I think its great that amateurs like us are able to access equipment of the caliber of Astro Physics, Takahashi, Obsession and SDM for a very reasonable price (compared to owning such equipment a few decades ago, when a good scope cost as much as a family home)

If we all settled on a mediocre scope without critical reviews and opinions on forums like this, then that is all the makers would give us.

Having said that I would not think any less of someone who chose to spend less and were content with what they got for their $$$. There are certainly premiums paid for certain logos. A $6000 Tak is not going to be 4 times as good as a $1500 William Optics, nobody expects it to be.

+1

Indeed I suspect the ED120 will outperform most bino's on planets - even 2-4k bino's

[Profiler (Profiler)]

I have to admit looking back at this thread - whatever peoples different views may be between reflectors v refractors one thing is certainly clear - 'Refractors' whatever their size or quality certainly do engender passions amongst AA's

[Profiler (Profiler)]

Originally Posted by brian nordstrom

against physics , my Tak sky90 f5.5 and SW 102 f5 , both 500mm f/l's , the Tak shows more on luna, planetary and deep space than the sky watcher? .
Don't give me the "Coatings" thingy , ok , the SW coatings are new generation . The SKY90's are 10 years old , technology wise ? don't think so ..
Please explain ..
( See my post in Celestial events chapter titled this , spotted something this morning ....) ..

In my opinion a 120mm SW using an fl53 doublet APO is the bees knees , grab one and enjoy . Gonna be a classic like the ED80 .

Brian

Not sure I am following this post. My experience with the issue of coatings more pertains to their longevity and resistance to potential harm. In this context I don't believe there is any contest between the applied coatings in premium brands compared to the budget brands. I have come across plenty of Synta Tech equipment wherein the coatings show signs of natural decay (i.e. not damage from misuse etc). Your 10 year old Sky90 is a tribute to the quality standards of Tak equipment and why it is still going strong even today.

Issues of optical performance more relate to the optical lens design, quality of glass and quality of construction/correction etc Thats my 2 cents worth at least

To put this all into perpsective with a hypothetical - hands up anyone who honestly thinks one of the mass produced particle board 10' Synta tech Dobs will still be in one piece if purchased today and used reasonably regularly over such a time period?

[alocky (Andrew lockwood)]

This is a very good point - I have friends who own and use 'good' quality fork mounted SCTs and have had them for a few years, with no issues. On the other hand, exactly the same scope subjected to the level of use of regular public outreach sessions at Perth observatory has not fared as well, with drives wearing out surprisingly quickly. Horses for courses! Meanwhile, the 100 year old Calver does its thing without any fuss night after night, and in the main dome, the Boller and Chivens has been going about its business for many decades, every clear night. I think this level of quality is another step in cost beyond AP, Tak etc...
regards,
Andrew.

Originally Posted by Profiler

Not sure I am following this post. My experience with the issue of coatings more pertains to their longevity and resistance to potential harm. In this context I don't believe there is any contest between the premium brands and the budget brands. I have come across plenty of Synta Tech equipment wherein the coatings show signs of natural decay (i.e. not damage from misuse etc). Your 10 year old Sky90 is a tribute to the quality standards of Tak equipment thus why it is still going strong even today.

Issues of optical performance more relate to the optical lens design, quality of glass and quality of construction/correction etc Thats my 2 cents worth at least

To put this all into perpsective with a hypothetical - hands up anyone who honestly thinks one of the mass produced particle board 10' Synta tech Dobs will still be in one piece if purchased today and used reasonably regularly over such a time period?

[bigjoe (JOSEPH)]

In some countries there seems to be a few 30 yr old temma tak mounts still going strong with only maybe the bearings changed (not a hard job),the gearings being made of silicon bronze.So very tuff, even when a lot of them have been overloaded with C11s and all the astro gear. Thats just one of the reasons these mounts are so coveted.Cheers

[Satchmo]

Originally Posted by Profiler

To put this all into perpsective with a hypothetical - hands up anyone who honestly thinks one of the mass produced particle board 10' Synta tech Dobs will still be in one piece if purchased today and used reasonably regularly over such a time period?

Depends if you are after an heirloom to pass down or not - I'd rather a larger dob with a tired looking mount in 10 years thats actually shown me some serious stuff than a pristine refractor that has not , but will be a nice heirlom for a family member when you are gone.

If you are looking for longevity then you get what you pay for. Most of the SCT's around today will end up in garage sales because their electronics can't be maintained rather than mechanical failure.

[LewisM]

In the past decade, I have owned and resold a lot of scopes; refractors and reflectors (Maks, Cats, Dob Newts, Newt astrographs).

Out of all that mess, I kept 2 scopes - both refractors.

All depends what you want to get out of it and your own precepts. Refractors fit my needs and tick all the right boxes in my lists.

[Profiler (Profiler)]

Originally Posted by Satchmo

Depends if you are after an heirloom to pass down or not - I'd rather a larger dob with a tired looking mount in 10 years thats actually shown me some serious stuff than a pristine refractor that has not , but will be a nice heirlom for a family member when you are gone.

If you are looking for longevity then you get what you pay for. Most of the SCT's around today will end up in garage sales because their electronics can't be maintained rather than mechanical failure.

Yes - but the hypothetical was who honestly thinks a 10 year old Synta tech dob will be in one piece with a functional mirror with coatings etc

[LewisM]

I was surprised that my crappy Bushnell 8" Dob lasted 10 years - and it was cheaper than any Skywatcher. But, it did, with absolutely minimal damage. I resold it here, and it is still going strong.

Though, I have to admit, it was that exact scope that put me off Dobsonians for life. Utterly frustrating! I will say though, it held collimation INCREDIBLY well!

[Satchmo]

Originally Posted by Profiler

Yes - but the hypothetical was who honestly thinks a 10 year old Synta tech dob will be in one piece with a functional mirror with coatings etc

The 3.9m telescope at Coonabarabran has to get a new coat every six months

Recoats are just basic maintenence- kind of the tax you pay for getting all that light so cheaply! We have allready seen in other recent threads that an 8" refractor free of false colour ( as a reflector is ) can cost around $250,000 .....You would not expect to run your car for 10 years without changing the oil regularly.

That being said , to my knowledge 98% of all the mirrors I have made with a basic quartz overcoat are still in service with their original coatings many which are coming up to 15 years old.

[David Niven (David Niven)]

You will see more per dollar with a dob than with an over prized refractor.
Sharp flourite lens are useless, without sufficient light !
This is especially true for visual DSO imho.

[Steffen]

Originally Posted by Profiler

Yes - but the hypothetical was who honestly thinks a 10 year old Synta tech dob will be in one piece with a functional mirror with coatings etc

Probably not a lot of people. But it doesn't really matter, the 10" SkyWatcher Dob costs $800. You could buy a new one every three years and still be ahead (by a large margin).

Cheers
Steffen.

[Profiler (Profiler)]

Its interesting that few can actually answer the hypothetical and instead have to re-characterise and alter the posed issue.

The hypothetical isn't whether recoating of a mirror should be viewed as a routine maintenance issue, it isn't whether you can purchase several new dobs at separate time intervals for the same or less money and it isn't about the perceived visual capabilities of a dob v refractor.

The hypothetical is who honestly thinks after 10 years a Synta Tech dob would still be in one piece and operating fine. This point is made in contrast to Brians Tak Sky90 which is 10+ years old and essentially in the same optimal condition.

Given that no one really seems able to answer this without resorting to conflating the posed issue I think my point is made

[Steffen]

Originally Posted by Profiler

Given that no one really seems able to answer this without resorting to conflating the posed issue I think my point is made

I thought I answered it, not many people would believe that a particle board Dob would last 10 years with frequent use, dewy conditions etc.

What isn't clear to me is the point you consider made. That expensive equipment is expected to last longer? Wouldn't that be a default assumption?

Cheers
Steffen.

[LewisM]

Richard,

As I intimated above, I partially agree, but mileage varies.

My FL102S is around 20 years old, PROBABLY. In pristine optical condition. Can't ask for a better scope in MY opinion.

The Bushnell 8" Dobsonian I had was subjected to some sordid conditions, including living in red dust at a friend's place for 3 years whilst we moved away for work. It survives to this day in pretty much the condition I bought it in, and, after I cleaned the red dust off the primary, there was only 1 TINY coating deterioration spot. I call that pretty respectable for a cheap scope.

I personally have aversion to ANYTHING astronomical being made from either plastic, cardboard or particle board (let alone god forsaken MDF!), but that is a personal subjective objection only

[Profiler (Profiler)]

Yes - you do concede the point that Synta Tech equipment doesn't last

With respect to the automatic expectation that higher quality more expensive equipment will last longer - well - wouldn't the analogous logic to that assumption extend to the earlier point about the optical performance of high quality refractors aren't going to be the same as Synta Tech refractors

Otherwise - as I keep on stating ad nauseum - if a Synta Tech ED120 was the same or even close to a TV-NP127 (for example) then companies like Tak, AP, TV, APM etc would have been out of business decades ago and we would all be using ED120s

[Profiler (Profiler)]

Originally Posted by LewisM

Richard,

As I intimated above, I partially agree, but mileage varies.

My FL102S is around 20 years old, PROBABLY. In pristine optical condition. Can't ask for a better scope in MY opinion.

The Bushnell 8" Dobsonian I had was subjected to some sordid conditions, including living in red dust at a friend's place for 3 years whilst we moved away for work. It survives to this day in pretty much the condition I bought it in, and, after I cleaned the red dust off the primary, there was only 1 TINY coating deterioration spot. I call that pretty respectable for a cheap scope.

I personally have aversion to ANYTHING astronomical being made from either plastic, cardboard or particle board (let alone god forsaken MDF!), but that is a personal subjective objection only

Hi Lewis

I missed your previous post - okay - point noted but then I find it very poignant that you conclude that it also put you off Dobs forever