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Posts Made By: William Chang

March 4, 2003 02:39 AM Forum: Equipment Talk

Follow the (little) GOTO

Posted By William Chang

What do you think of this idea:

Bring along a little GOTO like the NexStar 80, and match the red-dot of your big scope to that of the little guy. Even better, put a laser beam on the N80 and everybody can point their scopes at the spot. Any problems you forsee?

This would save some big bucks retrofitting a large mount.

-- William Chang, Saratoga CA

April 6, 2003 05:40 PM Forum: Astro Binoculars

Shoulder mount?

Posted By William Chang

Has anyone seen or made a shoulder mount or harness for big binoculars? I have several for photography but don't yet have a big pair of binocs. Last time I was at Home Depot, I saw a strange-looking bent aluminum tube contraption (in various sizes too) that can rest on both shoulders or the back of a lawnchair; a crossbar can be added to mount the binocs. Any other ideas?

-- William Chang, Saratoga CA

April 6, 2003 06:08 PM Forum: Equipment Talk

Split-tube Dobs?

Posted By William Chang

I have heard a bit of buzz about new split-tube Dobs from major manufacturers, but no details. Does anyone know more? Do they also retract for storage/transport even if not for hand-carrying? Thanks,

-- William Chang, Saratoga CA

May 23, 2003 08:25 PM Forum: Equipment Talk

Airline carry-on scope/optics

Posted By William Chang

Does anyone have recommendations or experience (besides the AP Traveler or Questar 3.5)? Would like something with aperture for DSO, preferably greater than 8" :-) Willing to do some "safe" (dis)assembly, and/or transport non-optical components in checked luggage, if necessary.

Typical airline regulation carry-on is only 9x14x22", 22lb (weight can be stretched a bit), which seems to rule out the C9.25. Is there a commercial truss Dob whose thin-mirror/box can be safely removed, and whose "body" fits a suitcase?

I have looked at "Alice" and other light-weight/flying scopes on the web; but these are all completely scratch-built. And, while light-weight scopes are great, the real premium seems to be on _compact_ scopes. Even then, not many will fly. (The "Uti" looks nice but is only 8" f/5.)

And, among the cassegrain-type scopes, which is "best" for this purpose?

Let us brainstorm!

-- William Chang, Saratoga CA

May 23, 2003 08:46 PM Forum: Telescope Making

Airline portable scopes?

Posted By William Chang

Has anyone designed or built scopes that can fly? The optics at least (if not the OTA) should be carry-on (9x14x22", 22lb or so, weight can be stretched a bit); the "body" should fit a suitcase etc. Any (dis)assembly should be relatively safe to perform! I have seen "Alice" and other flying scopes on the Web, but I'd hate to baggage-check the optics...

Oh yes, I'm looking to maximize aperture for DSOs :-)

Appreciate any and all suggestions!

-- William Chang, Saratoga CA

June 6, 2003 12:38 PM Forum: Investment Discussions

March 7, 2000 and June 6, 2003

Posted By William Chang

End of yet another Fed-funded 3-month run up? -- William

June 22, 2003 10:09 PM Forum: Equipment Talk


Posted By William Chang

Guys, I see that Jeffrey is now off Astromart, after listing his astro equipment for sale < 12 hours ago. Does anyone know what happened?

From what I can tell, Jeff is a lawyer and a stargazer, both indicative of trustworthiness. So I intend to follow through with the transaction, unless you guys warn me otherwise.

(Yes, the ads were a bit strange, so was his mood I'm sure. I hope he'll be OK.)

-- William Chang (Saratoga CA)

July 16, 2003 11:50 PM Forum: Telescope Making

Airline portable design questions: 11"

Posted By William Chang

I have been designing several airline portable scopes, what I call the "91422 Series" (9x14x22 carry-on size). Disclaimer: I have not built a scope before :-)

I now have virtually all the parts for an 11" f/4.5 modelled after the StarMaster ELT (using original 12.5" ELT poles and connectors), but more compact. The mirror box (to be built) is 16Lx14Wx9H; secondary cage is 14Dx7.5H; removable alt-bearings are 14"D semi-circles; the 7"H rocker sides are hinged on the inside and fold down for transport; when upright the rocker sides press against the edges of the rocker base through tensioners.

A major challenge is the needed low-profile mirror cell -- every inch counts since a taller cell means less room inside the mirror box to nest the UTA (which partially encloses the primary); the UTA in turn has to be taller for the extra light-path, since the poles are fixed at 34"L. What if I "hung" a square mirror board at three or four points along its perimeter, using bolts/springs/wingnuts (or push-pulls) in reverse fashion, i.e. wingnuts on top? Am I more likely to run into rigidity/play issues compared to the usual design, wingnuts on the bottom and closer together? Has anyone tried a low-profile cell like this? (I realize the gap between the mirror board and rocker is "dead space" normally taken up by the cell and protruding collimation bolts; however, those things can't stick out of a portable, fixed-height mirror box.)

Finally, should I use a sling for the 11" 1.5"-thick mirror, or just silicone in-between the mirror perimeter and angle brackets (like describe in S&T last year)? Any other suggestions for the cell, commercial or otherwise?

Any questions, suggestions, or critiques welcome and appreciated.

-- William Chang (Saratoga CA)

July 16, 2003 11:57 PM Forum: Telescope Making

Airline portable design questions: 18"

Posted By William Chang

My concept of a "dream scope" is an 18" whose sides are truncated to fit 14x18 (!). I have tried to observe the effects of such an aperture mask (two sheets of paper) -- basically undetectable to me until the blockage is great. Additionally, some contrast should be reclaimed by using a smaller diagonal, since the light-path past it is 2" shorter. The 13.5x18 mirror will have 90% of the light-gathering power of the full 18", but is mechanically only 14" wide, another advantage.

I imagine four long (2-section?) poles arranged in "anti-parallel" fashion: looking from the side, the poles converge from 18" apart to around 9"; looking from the top/bottom, the poles diverge from 14" to 16". The (4) trapezoidal facets help make the truss structure more rigid, and also miss the light cone. The poles on each side are joined by boards (one holds the focuser); a pair of curved vanes, joined at the center, connect across the poles and also hold the secondary cell/mirror. (I don't know if a full secondary cage is necessary for structural/vibration reasons.) The poles may be too long to transport unless they are telescoping or sectional.

Anyway, although this is currently just a "concept", I think I would be willing to commission an 18" thin-mirror/cell with truncated sides... any takers? :-)

I realize the above descriptions are hard to get across without pictures. In any case questions, suggestions, or critiques will all be greatly appreciated!

-- William Chang (Saratoga, CA)

p.s. does anyone have a badly chipped 18" thin mirror? ;-)

July 17, 2003 12:07 AM Forum: Equipment Talk

Airline portable design questions

Posted By William Chang

over in Telescope Making forum. -- William

p.s. does anyone have a badly chipped 18" thin mirror? ;-)