For testing the fate of the draw-tube, all I needed was an object at infinity...
...the Moon, with the new focusser and the 0.76mm spacers, through my GSO 32mm "Super Plossl"(it's not all that super, really), and at 9.4x...
I had my old Minolta DiMAGE F100, its shutter, set at 1/45th of a second when I took that shot, as the Moon was much brighter than that. From that, I know I'm getting the full aperture, or near enough.
I tested with the following items...
Celestron star-prism diagonal
SVBONY SV188P star dielectric-mirror diagonal(99% reflectivity, albeit alleged)
Antares 2x and 3x barlows
32mm, 20mm, 16mm, 12mm and 6mm eyepieces
Why, I had even tested the Vixen 6mm "NPL" Plossl combined with the 3x-barlow, at 150x. The view of the Moon was not bad at that power, not at all. It didn't make my jaw drop, but one of my socks did fall down a little ways towards the ankle.
But I've had one of my 70mm f/12.9 achromats up to 225x, on Polaris, and I could still make out the star's first diffraction-ring, albeit not razor-sharp. The Moon would take even more power besides, and still look pretty, hence I will expecting that from this 70/300, not that I'll realise that of course. In that event, I may contact Barska.
I can't wait to get these and other of my telescopes onto my new EQ-5, and with its wee 9V motor whirring away in the night.
Incidentally, Polaris is one of my most favourite targets, as it doesn't move.
The draw-tube was tested with each eyepiece, with both diagonals, prism and mirror. I made my measurements here...
All measurements were shortest with the star-mirror, but it is with the star-prism that I will be using the telescope stand-alone.
Although, as an optical-finder, I want to use a star-mirror. I will only be using the 32mm(9.4x), perhaps the 20mm(15x), with the star-mirror, in that capacity.
The farther the draw-tube racks inward into the telescope, the more likely the end of the focusser will threaten to cut off the short, fat light-cone formed by the fast-doublet.
The shortest measurement was with the 32mm, at about 10mm, and with the star-mirror...
That's not good, I'm thinking. Will the end of the draw-tube slice into the light-cone?
Perhaps I could just shave off the end, about 2mm or 3mm off, flush with the end of the flange, and be done with it...
The longest was with the Tani 20mm Erfle, at 35mm, with the star-prism...
No problem at all, and I wouldn't have to touch the draw-tube.
If I used star-prisms for both, problem solved, no need to cut off the draw-tube, but I just got this SVBONY star-mirror, and I want to make use of it.
I haven't tested my 90° and 45° erect-image diagonals yet, during the day, for birds in trees, ships at sea, nor at night. That testing will be forthcoming.
In that I will using this for observing, stand-alone, I wanted to transfer the specs-label from the old focusser to the new. I heated the label with a blow-dryer, whereupon it pulled off quite easily. I then placed it on a piece of glossy backing-paper from the flocking...
I can re-apply it with clear, double-sided tape, or spray-adhesive, likely the former.
I began the renovation of this achromat almost two years ago. Apparently I wasn't in any hurry, but I will be finishing it, at last, and relatively soon.