neo-achromatic telescope ???

[Ukastronomer (Jeremy)]

This is on ebay and described as a 4 element ED scope ?????

Vixen say neo-achromatic telescope

New to me ?

[Outcast (Carlton)]

Jeremy,

I've sent you an email... was just easier than trying to post the info on the thread..

The info I found dated back to 2007 so, it would seem not a recent invention... you'll read the info I sent you.. people seemed quite happy with them but, they are just opinions & like bumholes... everyone has one... So, make of that what you will...

Cheers

[rrussell1962]

https://www.myastroshop.com.au/produ...sp?id=MAS-046C

[Wavytone]

UYOk has The Petzval design - which is what this is - dates from 1840.

https://en.wikipedia.org/wiki/Petzval_lens

Singlet lens - no attempt to correct for dispersion (chromatic aberrations)
Doublet lens - better: corrected for two wavelengths
Petzval - better than a doublet and cheaper to make than a full triplet APO.
Triplet - corrected for three wavelengths
Refrlector - corrected for ALL wavelengths.

For refractors there is a trade-off: colour correction vs cost and durability. Recent glass types have tipped the balance in favour of triplets in the range 80-130mm aperture though IMHO beyond that catadioptics are good for 120 - 250mm, beyond that reflectors reign.

[LewisM]

I have used a couple - nice, but definitely not colour-free (quite evident IMHO on bright stars and the Moon) - an apochromat they are not, but apparently CA reducing filters help.

Vixen has had these out for MANY years now.