Solar Max Coronado 70mm Scope

[Solar B]

I thought we'd already been over this ... it's an updated SM60 with externally mounted etalons which is an improvement over

the SMII but is a reversion of the orginal and best SMs with the US made etalons but its not a 70mm HA scope.

 

Brian 

[Merlin66]

I suppose under this "marketing hype" I could say I had an 80mm (ED80) "solar telescope" fitted with a SM60 external etalon........

[timwetherell]

10 hours ago, Merlin66 said:

Coronado solar scopes always had doublet objectives - claimed to be optomised for Ha.

the single objective lens was introduced by Lunt.

 

Mine's quite old (not sure how old cos I bought it second hand) but definitely pre Meade. I'm not game to dismantle it, but it's easy to unscrew the etalon and remove the energy rejection diagonal at the back. This is the view through it as a "regular" unfiltered telescope. There's lots of CA. It's possible that it's a doublet with odd correction for H-alpha - Perhaps the two elements are used to eliminate spherical aberration? But definitely not a classic achromat  If anyone tries this, please be sure to put the filters back on the moment you've done experimenting - a solar scope with the filters off is a very dangerous thing to leave lying around!!

[Merlin66]

Tim,

that's interesting...

which scope, a PST - With a "blue" or "gold" objective??

 

[timwetherell]

8 minutes ago, Merlin66 said:

Tim,

that's interesting...

which scope, a PST - With a "blue" or "gold" objective??

 

Actually it's a coronado solarmax 60mm single stacked scope. I've looked through quite a few PSTs and single and double solarmax 90s, but for me the 60 is about the sweet spot in terms of performance vs expense and hassle setting up

[Macavity]

I now see that the whole field of Solar Telescope objectives
is potentially "mined"! But quite interesting, nevertheless...

No exact answers elsewhere, but sometimes the focal length
is the same as a quoted "solar scope value" (sometimes not).

The inner surface of my Lunt 50 objective looks fairly FLAT?
But I don't immediately know the implications --- Compared
to say a bi-convex (singlet?) lens, re. spherical aberration!

I did once try to make of of Sir Patrick's (fabled) One Dioptre
spectacle lens telescopes, but rapidly learned about modern
spectacle lenses being a convex meniscus re. aberrations!

(Selfishly off topic?) Now looking at this Frankenscope idea!
Maybe stopping down an ST120 doublet to 90mm to match
the biggest EDF I can afford? My home made artificial star
plus solar continuum showed significantly improved results
with an ST102 objective... a not-so-bad diffraction pattern?

Don't know whether typical "ST Achromats" benefit from a
67% diameter field stop to reduce Spherical Aberration...
https://en.wikipedia.org/wiki/Spherical_aberration 
It's hard to get really HARD information, so I experiment?

As we know, Solar Scope upgrades are Expensive (sadly)!

[xtreemchaos]

so its quite a bag of ferrets then, next to some smokie mirrors  , ill stick with me Quark. charl.

[Peter Drew]

I have dismantled some of all of the various PST incarnations and all of them had cemented doublets. It's true that if you offer up an eyepiece to one of these in isolation it does give some weird chromatic effects confirming that there is an added correction of some kind to optimise the Ha performance.  @Macavity, you can place your 90mm ERF internally to safely utilise a donor telescope of suitable F ratio up to 150mm aperture.  

[timwetherell]

Interesting! sounds like my 60 may indeed be an oddly corrected doublet then

 

[Macavity]

TBH, I find myself MORE tempted to invest (sic!) in scopes
that provide as much technical information as possible. Not
asking exact details of *patented* Etalons or Quark innards,
but "incidental stuff" (pictures even!) can be reassuring...