Minimum magnification for DSO

[F15Rules]

On ‎13‎/‎03‎/‎2016 at 10:13, Ricochet said:

I think the Maxvision is only available in the second hand market now but the 24mm ES68 is still in the Bresser sale and is roughly in budget give or take the actual currency conversion.

That ES is a cracking deal, go for it!

 

I've owned both and (for me), the ES is better in every regard:

• Argon Sealed, so no dust will get inside it (or moisture, although we don't tend to observe in the rain (!), it can get very dewy outside at night
• Better ergonomics than the Maxvision
• Better build - closer to Televue than the Maxvision
• Identical optically, that is, excellent
• Nicer looking - am I the only one that thinks Maxvisions are a bit, er, bulbous looking??
• The fixed eyecup works better for me

As I say, just my thoughts, but a cracking eyepiece for the money. I bought mine from the very same website in the link :-)

Dave

[acey]

10 hours ago, vlaiv said:

You are correct that dimming is proportional (for both sky and target) with smaller exit pupil, but we have to consider the possibility that human eye/brain combo has non linear response in low light region, so we perceive or see dimming to be different if two have different brightness (so that target is theoretically detectable). I suspect that this is the reason people report that different exit pupils give best results on DSO in LP and dark site - different level of proportional dimming brings both sky and target in region where nonlinearity is the greatest and hence best visual contrast is perceived.

You are correct that contrast threshold is a nonlinear function of adaptation brightness and target size, both of which are a function of exit pupil. I refer you to my research paper on the subject:

http://arxiv.org/abs/1405.4209