SW Evostar 120ED vs Startravel 150?

[Ben the Ignorant]

4 hours ago, John said:

So not your own personal experience then ?

 

No, can't try them all.

[Ben the Ignorant]

2 hours ago, spaceboy said:

This is interesting. Is the ES127 FPL51 or similar spec as I have seen reviews suggest this also shows false colour which I found odd as it's a triplet and only has 7mm over the ED120 which tend to only show fringing in defocused stars.

 

The answer is two-fold:

The YouTube guy did find a tiny bit of fringing because the glass is in the FPL-51 class.

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http://www.davidesigillo.eu/test_120ed.html

http://www.davidesigillo.eu/test_127ed.html

The italian reviewer (a professional optician who improves scopes and eyepieces) finds more fringing in a Meade 127mm (otherwise excellent) FPL-51 triplet than in a Sky-Watcher 120mm FPL-53 doublet.

Sorry for the german and italian languages but I take info where I can find it.

 

[Ben the Ignorant]

1 hour ago, TSRobot said:

Do folk really need ed apo to enjoy the heavens?

Of course, not! I have an achro, a SCT, two newtonians and one apo. What makes the difference between enjoying them or not is collimation, not optics type.

[John]

I've read a number of reports where a triplet (Meade, ES, other branding) has shown a touch more CA than the ED120. Here is one:

https://www.astromart.com/reviews/article.asp?article_id=678

I own an ED120 and have used a Meade 127mm triplet.

 

 

[spaceboy]

Well this has sure put my mind at rest. I'd long regretted not pulling the trigger on a 152ED when one came up for a fairly reasonable price. All I could think was the mention that the ES ED127 f/7.5 showed some fringing and that was supposed to be a better corrected triplet so I sat on my hands. With the larger 152 f/7.9 being a doublet with FPL51 I'm guessing the views could be quite colorful for an "ED APO"

[John]

1 hour ago, spaceboy said:

Well this has sure put my mind at rest. I'd long regretted not pulling the trigger on a 152ED when one came up for a fairly reasonable price. All I could think was the mention that the ES ED127 f/7.5 showed some fringing and that was supposed to be a better corrected triplet so I sat on my hands. With the larger 152 f/7.9 being a doublet with FPL51 I'm guessing the views could be quite colorful for an "ED APO"

They can be pretty good:

https://www.cloudynights.com/articles/cat/user-reviews/first-impressions-of-the-lunt-152mm-f8-ed-apo-r2889

(the Lunt is the same scope as the APM branded one)

I had concerns over issues with the objective lens cell design which I could not get enough re-assurance on from APM so I decided not to go for one.

[spaceboy]

How do you mean John? The one thing that appealed to me most was the cell was collimatable on top of it being a doublet and not having a 3rd lens to worry about if the scope ever did take a knock. The doublet advantage being based on talk that loosening of the lens and gently tapping around the cell often sits doublets back in to place with in the cell should the untoward ever happen??? Between that and a collimateable cell you'd always have the piece of mind your collimation at least was going to be bang on, which for a large CA potentially producing refractor is a plus.

[spaceboy]

Sorry for taking the thread a little of topic 

[John]

Because of my concerns I started a thread on the Cloudynights forum:

https://www.cloudynights.com/topic/535732-apm-lunt-152mm-f8-ed-doublet-optical-quality/

I didn't find the responses to that or my questions to APM reassuring enough to proceed. I believe that the lens cell has been re-designed in the later models.

I don't mind messing with the objective of a £200 chinese 6" F/8 but I don't want to have to fiddle with a £2000-£3000 scope.