Telescope Reviews: Field of view

You mean "how do you observe wide objects at close to optimal detection magnification for the details when at the optimal magnification the object doesn'fit in the field of a narrow AFOV eyepiece"?

Mhhh..picking up chicks sounds a lot nicer.

It's pointless to argue with deSitter - he picks tests designed to favour non wide field eyepieces and then simply dismisses any observing style that doesn't fit that model as irrelevant. It's not a proof of anything but circular reasoning.

Nobody in his sane mind would pick a Nagler over an ortho for looking at the trapezium in M42 only. What's good about an Ethos is that you can often use enough magnification to detect E and F *and* still see more whisps of nebulosity extending very far away from it, all without moving the scope or losing context.

Sketching large objects is a pain in the lower back without a wide field. With an ortho, you never seem to get the location of your field stars vs. the other star and the location of small details right, or the proportions exactly right, because you can't see it all at once at the magnification the object deserves or needs. In effect, you have to do what photographers do when they make mosaics.

Of course, you *can* use low magnification, get your reference stars on the sketch, and then start navigating, going back to lower magnification to get the orientation of a small detail just right when the high mag view has too few field stars to do it well, but forgive me for thinking that it's like flogging yourself on the back and telling yourself it doesn't hurt.

And there's no hard rule that makes photons count the number of air-glass transitions and nothing else: Pentax XOs have one more lens group than orthos but the excellent coating and baffling makes a 5mm handsomely outperform all 5mm orthos except the Zeiss ones (ubt including the old Pentax ones!).

And on Jupiter, some nights ago, I actually picked a Zeiss-barlowed Pentax XW as the eyepiece of choice. Yes, it has lots of lens groups and "too much glass", but the added eye relief actually helped to reduce the glare caused by the reflection of Jupiter on the eyeball (even at 400x in my scope I have an exit pupil close to 1mm and Jupiter can be darn bright), and the excellent coatings means that even the barlowed combination almost feels like a simple eyepiece design (and the scatter around Jupiter is markedly less present than in e.g. a T6 Nagler).

That night I could also use an ortho and Pentax XO with a filter to reduce that irritating glare (I have both at similar effective focal lengths to my barlowed Pentax XW) and I actually tried it -- and would have expected to prefer it, because I only happened to use the XW because I had been gawking

at deep sky objects.

But I couldn't achieve the same depth of colour that I could with the unfiltered Pentax XW (even though the detail was still there, with a complex group of three barges playing with each other in the NEB, the subtle tone differences weren't as vivid and the festoons close by didn't seem quite that blue anymore).

Guess what? I used the Pentax XW because that night it worked better, somehow. I don't like to be guided by religious fervour above all else.

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400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Orion Starblast (114mm f/4 reflector, Alt/Az)