Edmund Scientifics AstroScan

The AstroScan has a really impressive engineering design. See the good in-depth review here. This is how I'm rigging mine to the task.

Stock eyepieces are really good and also parfocal (28mm and 15mm). Their barrel size is interesting. It is a bit larger than a regular EP of 1"1/4. I suspect it is metric because my Russian eyepieces from TAL reflector fit the AstroScan focuser almost perfectly (this way I can use the 3x TAL Barlow lens with the AstroScan).

F=445mm, D = 105mm, A =  1 : 4.24

Reference magnifications.

Zoom Level	Magnification	Eyepiece Focal Length	Exit Pupil	Field of View (FOV)*	Best For...
Minimum Viable	15x – 17x	26mm – 28mm	~6.0mm	3.0°	Large nebulae, Milky Way scanning, and finding targets.
Medium (Low)	25x – 30x	15mm – 18mm	~4.0mm	1.6° – 2.0°	Open clusters (Pleiades), large galaxies (Andromeda).
Optimal/Resolving	50x – 70x	6mm – 9mm	~1.5mm	0.7° – 1.0°	Detailed lunar views, globular clusters, and bright nebulae.
Max Practical	100x – 110x	4mm – 4.5mm	~1.0mm	0.5°	Planets (Jupiter/Saturn) and splitting tight double stars.
Theoretical Limit	200x	2.2mm	0.5mm	0.2°	Rarely usable; requires perfect atmospheric stability ("seeing").

On the image above

g) I have outfitted each eyepiece with the rubber eye guard, which makes focusing more comfortable by providing a soft guide for the eye positioning, as well as covering the open side of the eye from stray light.

c) The scope shoulder belt. It can be also adjusted to help protect the scope from falling off the base (h) when it is mounted on a high tripod (i).

a) The button of the green laser pointer. I can keep the pointer ON simply by rolling it around so the side of the OTA will depress and hold the button. Or I can depress the button momentarily while correcting the pointing direction. This is an ultimate solution for the missing dioptric sight and much more comfortable as well. Such a mounting is possible with the unbelievable simplicity because of the precise design and fine craftsmanship of the focuser's bulge. It creates a perfectly square corner for the cylindrical laser pen's body so I can see the end of the laser beam exactly at the center of the 15mm EP.

b) The green laser pointer held in place by two rope rings (I call it "harness"), which allows for quick laser pointer installation and rotation. It's almost zero weight, which is important for a ball scope.

d) and e) The OTA "harness" is a single piece of 550 paracord, making 2 loops fixed with the figure eight knots around the OTA in two places as pictured.

e) The open ends of the rope are in the figure eight knot too, providing necessary tension for loops. Much better than any rubber bands and also serving as a carrying loop and a single finger pull handle (you can tie on the side convenient for efficient pulling along the celestial parallel).

The "ball" design is truly ingenious. It is much more comfortable compared to the classic Dobsonian design because you can place the eyepiece in almost any position to conform to your body angle and you can "move the sky" in the field of view in an arbitrary direction (or even circularly) in a single straight and smooth push or pull. That, for example, is fixing the annoying "Zenith transit" navigation problem of typical 2 axis mounts.

I'm enjoying this little telescope between large Dob sessions and always taking it on my camping trips with kids.

Updates

I've implemented multiple upgrades to this neat instrument to make it even better for certain tasks/conditions.

E.g. the 9mm WO UWA (101 deg AFOV) EP adaptor. Views are just spectacular with it! The adapter is  3D-printed so it could replace the original drawtube with the fixed focus extender with a trivial but "non-destructive" rope harness keeping it in place. Then invented a special "ball-holding" technique to amend its seriously unbalancing weight while working from the picknick table or on the laps.

You can find other writeups about these DIY upgrades later on the feed.