What size telescope to see Hercules D crater on the moon?

[John Baars]

I meant for doing star test. not for observing with.

edit:
ok I dont know exactly what I did but now I see absolutely flawlessly circular airy disks with a ring around it. perfectly round. (for moderate to dim point sources)
brighter ones probably will have several rings though.
They also seem to look much smaller than they did previously.

I can even push my scope past its theoretical limit and still see smaller details when the atmosphere is calm enough. beyond 140x
most of the time its too turbulant for more than 70x!
in/out focus is still inconclusive. i think adding spacing is the wrong way around. it seemed to make it worse. and when i put back the original thinner spacer ring it was better.
might need to reduce spacing but im not sure what the right spacing is. 0.01mm? or 0.1mm? 0.2mm? it'll take forever and i dont want to smudge up the lenses anymore with the prints spacers make.
the alignment is so perfect this time i can't fathom it being any better. the airy disk is so perfectly round with the ring very neatly around the disk. with no distortions.

Congrats! Apparently you came across the right configuration. I wouldn't change it anymore. Never change a winning one! For startesting in an achromat I use a yellow/greenfilter.

[MistrBadgr]

I meant for doing star test. not for observing with.

edit:
ok I dont know exactly what I did but now I see absolutely flawlessly circular airy disks with a ring around it. perfectly round. (for moderate to dim point sources)
brighter ones probably will have several rings though.
They also seem to look much smaller than they did previously.

I can even push my scope past its theoretical limit and still see smaller details when the atmosphere is calm enough. beyond 140x
most of the time its too turbulant for more than 70x!
in/out focus is still inconclusive. i think adding spacing is the wrong way around. it seemed to make it worse. and when i put back the original thinner spacer ring it was better.
might need to reduce spacing but im not sure what the right spacing is. 0.01mm? or 0.1mm? 0.2mm? it'll take forever and i dont want to smudge up the lenses anymore with the prints spacers make.
the alignment is so perfect this time i can't fathom it being any better. the airy disk is so perfectly round with the ring very neatly around the disk. with no distortions.

Congratulations! That happens more often than one might think. You don't know what you did for sure, but all of a sudden, it works! My advice is to not go back into the scope unless something slips and you loose the good collimation or positioning otherwise. Do not fix it until it breaks!

[realflow100]

yeah this time i didnt even change the spacing. its just whatever it is and it looks pretty perfect.
its almost so perfect the slight bit of mis-spacing of the elements doesnt even matter. maybe it slightly softens the contrast of fine details but i can still see the fine details.

[realflow100]

OMG I SAW MAGNITUDE 9.5 STAR (or 9.75 not sure which one)
in pleiades!
at about 93x magnification in my 70mm F6 double refractor scope!

[John Baars]

The Pleiades shroud themselves more or less in a slight mist as you know. Although these nebulae are not directly visible, they still obscure the limiting magnitude of the telescope by tenths. Outside the Pleiades you will therefore be able to get a few tenths deeper!
Attached a nice test because I think you can still go a step deeper!

http://arksky.org/images/pleiades.jpg

[realflow100]

I doubt the nebula in pleiades is even taken into consideration in my high bortle 7/low bortle 8 observing location.
Maybe in a bortle 1 you'd see a slight difference lol

OK I checked in stellarium desktop version and the star I saw is actually magnitude 10.5 (air mass reduced to 10.84 magnitude)
so thats even more impressive
the web version may be out of date?