Telescopes & Tele-monoculars
Cyclops
Telescopes & Tele-monoculars
If you are prepared to venture into the secondhand Ebay etc market, the following models, all under 500g (excluding case), can survive the years in good condition. So if you have a favourable description by an Ebay seller who seems to know his or her stuff, or a chance of a 'try before you buy' purchase, a punt may be on.
Eg research a Soviet Lzos 33T 10x30 single-draw telescope, weight 257g, length 8" collapsed, 12.5" extended, 13.5" extended + lens hood. Near focus distance very roughly estimated 30'. Caveat: narrow field of view. I found the later Soviet Lzos Turist 4 10x30 to be inferior in design (and possibly also in survivability).
Or a Soviet Lzos Turist-p 8-20x32 non-extending zooming 'pocket scope', weight 383g, length 12.5" or 13.1" with focusser screwed out. Field of view at 8x magnification narrow, but useful. Near focus distance at 8x very roughly estimated 20'. I think Binastro recommended 15x zoom as a level of zoom that might be usable unsupported in the field. We are all different, but my experience is the same.
I don't estimate fields of view, but I can safely say that, for the 33T at its fixed magnification, or the Turist-p even at 8x, fields are well below 5 degrees. Ie the two telescopes are tools for observing, or spotting & laying on, rather than scanning at close range.
You say you want a 'straight tube'.
But if you compromise in favour of a porro tele-monocular, then note that the Glanz Micro T-M 7x35 (440g) has a field of view of 10 degrees, and the Glanz Micro T-M 7x40 (462g) one of 9.5 degrees.
Tele-monoculars with a similar specification to the Glanz 7x40 were also marketed under other brand names
Stephen