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Posts Made By: Nathan Murphy

November 17, 2004 03:24 AM Forum: Equipment Talk

not ANOTHER collimation issue

Posted By Nathan Murphy

i must apologize in advance - i've read enough forums, talked to enough people, etc. to know more than i ever wnated to know about how to collimate my newtonion reflecting telescope. none of us need another question about collimation. i am, however, at my wits end to explain the following phenomenon:
my new orion xt8 came with a neat little collimation cap -a focuser dust cap with a shiny underside and a small hole in the middle. i later bought a laser. it's an antares single beam type.
i've practiced collimating with the cap so much, i enjoy it, and am lobbying for it to be an olympic sport in 2008.
so why, when i collimate my scope with my cap (the hole-in-the-dust-cap contraption), then check it with my brand-new single beam laser, does the beam hit 1.5" from the center of the primary?!
what is going on? focuser not square? secondary not concentric with focuser? collimator out of collimation? rift in space-time continuum?
i briefly checked that my laser was collimated. i quickly went through floyd's article (i told you i did my homework) and the beam doesn't move more than 1/8" at 10ish feet.
also - the star test (i've even been reading dick suiter's book) looks about right when i collimate with the cap, but i haven't looked yet with laser collimation.
assume, for the sake of argument, i went through the correct collimation procedure for both the laser and the cap.
scope is 203mm, 1200mm FL F5.91
thanks, nate

November 17, 2004 07:42 PM Forum: Equipment Talk

not ANOTHER collimation issue

Posted By Nathan Murphy

Thanks fellas.

i've got fellow astronerds here with glatters, kendricks, both barlowed and not. i'll try copmaring them with my cap.

sounds like i underestimated the role focuser->adapter->collimator slop can play in collimation.

of all the methods i've seen, the holographic projection to get everything 95%, followed by the barlowed laser is the most fun/easy/cool. it also requires the use of not one, but two lasers which means more dangerous radiation to play with. plus more equipment is always cool, in my book.

thanks again.

August 30, 2005 06:36 PM Forum: Star Parties

Anyone going to the Black Forest Star Party?

Posted By Nathan Murphy

doug and i will be in attendance with a large group from our astronerd club.

look for the duelling portaballs. (10 and 12.5)

i'll have my 10" Pball and a TV60, all wired up to keep the rain off. i'm hooked up a 42V dew heater system that vaporizes rain (or dew, or birds) up to 4' from my OTA. really makes for dry viewing of the cloud and skyglow nebulas.


the wife was going, but a sudden change of job has left me as a bachelor this time around. she really was coming. honest. i swear. she might even join me on saturday...

November 16, 2005 07:55 PM Forum: Equipment Talk

Whats the differance.

Posted By Nathan Murphy

i'm a relative youngster here, but started my astroitis about 18 months ago. a fairly experienced observer (portaball 12.5") recommended an 8" dob as a start. I promptly started hunting down faint globs and glaxies, looked at the moon, all was fantastic. i've since moved on to my own portaball (10") and in the meantime spent some time with an 18" dob from a friend. oh, and the 8" orion dob got an upgraded mirror (0.991 strehl). The guy who lent me is 18" has a 24" starmaster. we pushed that baby _way_ over the tasco limit last april whilst looking at the eskimo nebula in gemini. the seeing was amazing. We barlowed (2x powermate) a Televue 2-4 zoom, set at 4, 3 and yes, 2mm. That equates to 2700x+ at 2mm. the tracking could only hold the nebulae in teh FOV for a brief moment, but wow. holy #@$!#@@. pert'near 3000x and it looked like that S&T SBIG ad. try that with an APO!

I bought a TV60 last january for a travel scope, and it too, was amazing. 4.3° views of orion and the veil, outstanding (though lowish-power) planetary views. my observing buddy has a TMB105. i always thought the views were sorta dim, being a dob guy. however, mars at 700x was awesome through it at BFSP. never mind saturn at equally illegal powers.

sufice to say i broke down and just bought a TMB80/480, as 60mm wasn't big enough. the TMB is still extrememly portable, and it fits in a pelican case with the 2" diag and 9 eyepieces. hoo-ah.

the TMB gets over 5° views, I've had it shortly on the moon and (duh) mars, as well as M31 and assorted messier eye-candy.

the APO views are mesmerizing. so contrasty, such dark skies, and the airy disks, mama mia.

I must echo the sentiments of the old-timers grin here, that if you are serious about visual astronomy, you need a big-@ss dob for star parties and 500mile jaunts to dark sky sites (i.e. BFSP) and an APO to take with you EVERYWHERE.

only getting one scope? okay, i guess we'll let you (or should we?) then buy an 8" or 12.5" portaball. maybe a Uti8. I just saw a 7" starmaster for sale here on AM. poncet platforms are nice, and enhance the dobsperience.

don't forget, the other half of the equation is spending the rest of your savings on televue, pentax and/or TMB eyepieces! just ask floyd. they've given him an entire forum for just that stuff!

one scope: 12.5" portaball
two scope: 18" starmaster and TMB80/480
3 scopes: 8" portaball, TMB105, 24" starmaster

eyepieces (no choice here, you must buy them all)

41pan or
35pan (or 31 nagler, though i don't have experience with it.)
24pan
16nag
11nag
9 TMB planetary or supermono
6 TMB planeraty or supermono
2-4 nagler zoom

long post from detroit... 8O

May 10, 2006 05:34 PM Forum: Eyepieces

Who are the best eyepiece manufactures today?

Posted By Nathan Murphy

By Reputation:
1. Televue (duh)
2. Old Zeiss
3. Pentax
4. UO

By Experience:
1. Televue Nagler and Panoptics
2. Vixen LVWs (amazing. I prefer the 5 and 8 to comparable radian and naglers, even with the different FOV)
3. Televue Plossls

Star Party or Budget:
1. Burgess UWA
2. Orion Expanse
3. GSO Super View

I have only looked through a few from Celestron and Meade, and was not impressed. I realize it's a small sample, so I'm not flaming here. Everything I've looked through from Orion (save the ED-2) has been better than expected for the price - especially the expanse line. Orion's customer service has always been great to me.

IT's fashionable to give Bill Burgess a hard time, but his stuff is fine - i picked up some UWA's at a star party and they bested the Expanses of the same FL and FOV, at half the price...

We'll see how he improves his QC and customer service - i'm optimistic.

verdict:

TELEVUE AND VIXEN
(wait, they're the same company as far as North America is concerned! surprise!)

May 19, 2006 07:15 PM Forum: Chinese Optics Imports

More TMB 92mm Details

Posted By Nathan Murphy

OK, after going over my own memories of the discussion, and checking with bill, i can hopefully clear up the brick/aspheric saga:

While I was at NEAF, chatting with Bill and Tom, they indicated that:

1) the 92mm aperture was more out of neccessity than choice. bill wanted to do something other than 80mm, as there are tons of 80mm scopes now, andthe shop had tooling setup for a 95mm
blank (resulting in a 92mm clear aperture lens), so they made a run of ten lenses. these are the first "brick" design prototypes (type II, see below), to do proof-of-concept. the f/ratio was chosen to keep the tube length to 24".

2) Bill and Tom said there were 4 BRICK designs in the works (meaning
on Tom's computer, not at the optical shop yet) 3 (brick type I,II,III - their nomenclature) used a "new" (they're term, i won't speculate) airspaced triplet
design with glasses already conjectured here. *All 3* used
spherical curves, according to bill & tom. the 92mm was a type II.

3) the type IV is also a triplet but had 2 aspheric surfaces. that's the design that ought
to out-perform everything ever made ever by anyone ever anywhere,
evah. (my hyperbole grin ) this is also the most difficult to implement.

so there are 4 brick designs in the works, of which there are 10
prototypes extant of the type II, including the one at NEAT that bill wouldn't sell, lo-end tube/rings/focuser and all, for $1000 on the spot.

so brick does not equal apheric, unless it's the as-yet-unproduced type IV. bill did not give any dates whatsoever when the other "brick" scopes are coming out. the 92 from NEAF will be at BFSP, as well as possibly a 127mm (or one close to that aperture). There will be (according to Tom) other, as yet unspecified new TMB products on display there as well.

so, does that clear things up?

92 = all spherical, airspaced triplet with on-the-abbe line glass
type IV brick = not produced yet, some ashperic surfaces.
brick = airspaced triplet, first and last surface nearly plano, just a term of endearment for TMB's new designs.