FS60Q vs Zeiss Telementor

[vineyard]

2 hours ago, Stu said:

I don’t know for sure, but guess it’s quite possible for an eyepiece to be optimised to compensate for a specific scope’s characteristics.

I tried it out earlier this evening (when the moon was quite low), and it was interesting.  I think the CZJ orthos may v well be corrected to compensate!

I saw only a thin, thin sliver of blue and that was just around the top edge of the limb, and what looked like a hint of gold around the bottom bit of the limb.  So I'm guessing that's atmospheric dispersion as if it was CA it would track all round the limb?  (To be more accurate, Clavius was at the top, ie N-S inverted as we all E-W, so in reality the blue sliver was around the southern limb which I think is what would happen w dispersion?).

When I put the Vixen 6-O in, there was a larger ring of blue all the way around the limb, which I guess would make sense as the Vixen EP is not corrected for the TM objective and so that was the CA coming through?

If that is case, those clever, clever CZJ designers!  Colour-free viewing through a TM 🙌🏾.  Does anyone have any CZJ orthos they'd like to sell? 😂

Edited January 12, 2022 by vineyard
typo

[Andrew_B]

3 hours ago, F15Rules said:

Interesting Mike.. last night I used my 2" dielectric diagonal Cyclops with some large 2" eyepieces for the first half of the session.

Looking at M42 with the dielectric and an excellent 23mm Axiom LX eyepiece, I could look to the North East of the Trapezium (right way up reversed diagonal view) and see the two faint stars immersed there in the nebula..the "right hand side" star was visible with direct vision, the left hand side star was visible only with averted vision.

Half an hour later, I switched to my Revelation binoviewer in a Baader Zeiss BBHS T2 prism and a pair of Kson 16.8mm orthos, and was very surprised to see both these stars, very clearly, with direct vision!

To be fair, I was using a higher magnification with the bv, which made the contrasting sky background darker, but set against that, the binoviewer is usually held to lose around 0.5 to 1.0 order of magnitude due to the light beam splitting..so, I tend to think that the BBHS prism was reducing light scatter and possibly having better transmission than my dielectric diagonal? I believe the Baader website claims 98% transmission for the BBHS T2 prism..I don't know what the claimed transmission of my Astro Tech diagonal is though..

Dave

 

I suspect the difference is mostly down to the mirror having more scatter and reducing contrast as a result. The eye isn't very sensitive to small brightness differences so I doubt that's what you're seeing.