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Posts Made By: Dan D DuBal

February 21, 2004 05:13 PM Forum: Maksutovs

MK67 diagonal

Posted By Dan D DuBal
My Intes MK67 behaves similarly. Most recent-vintage units were designed to accomodate 2-inch diagonals. As such, most 1.25-inch diagonals are "too short" to reach focus in a typical set up.

An extension of some sort will allow you to reach focus just fine. If you have a short Barlow -- one with a removable lens assembly -- it should do the job. Simply remove the lens assembly and install the Barlow between diagonal and eyepiece (or adapter and diagonal).

Orion also sells extension tubes (both 2-inch and 1.25-inch diameters) which back things up 2 inches. I'm sure Anacortes offers similar items.

A 2-inch diagonal might also accomodate focus -- depending on how much (or little) "reach" your particular Mak needs.

Hope that helps.
Best wishes and luck.
-Dan

February 24, 2004 06:51 PM Forum: Equipment Talk

Help - What did I buy - G-102 Galileo Mak?

Posted By Dan D DuBal
Hello, Mike.

Can you tell if this is your scope?

If so, its focal length is 1400mm (~f/13.7). It's *not* a Synta product. I haven't heard any feedback from owners/users.

Best wishes.
-Dan

February 25, 2004 03:55 PM Forum: Equipment Talk

Refractor F.L. for Colorless Image

Posted By Dan D DuBal
Depends on aperture and your own definition of "color free." The larger the aperture, the "slower" the objective needs to be in order to yield similar achromatism (of a smaller achromat). A 60mm f/15 achromat will yield less chroma to the average eye than a 150mm f/15 achromat. To my own eye, a 4-inch f/12 achromat is hardly color free. A 4-inch f/20? Dunno -- never seen one.

My 60mm f/13 achromat fits both "rules" -- with lots of room to spare -- but I don't consider it color free.

Best wishes.
-Dan

February 26, 2004 11:53 PM Forum: Takahashi

CN-212

Posted By Dan D DuBal
I know of a few 2-inch-to-SCT-thread adapters. There may be others (perhaps Hutech/Borg?).
Scopetronix ("Adaptaview" -- also available at Anacortes)
Optec (also available at Anacortes)
Intes (available at APM)
Van Slyke Engineering

I have the Scopetronix unit; it's very nice.

I believe standard SCT ports are:
2" diameter
.302 "effective thread length"
24 tpi

Best wishes.
-Dan

February 27, 2004 05:17 PM Forum: Refractors

Are we seeing the Orion ED effect?

Posted By Dan D DuBal
I haven't noted a significant increase in Stellarvue sales. My recollection is that plenty of folks we re-selling theirs *before* the Orion ED80 appeared.

Another possible factor is simply the *number* of Stellarvues out there, now. If production, sales, & ownership volumes increased, then I imagine resale volumes would increase as well.

Best wishes.
-Dan

February 28, 2004 08:33 AM Forum: Wildlife Photography

What kind of bird is this?

Posted By Dan D DuBal
Dunno, but I bet it tastes like chicken.
:-)

Nice pic, nonetheless. Looks like a young adult -- not too big.

Best wishes, and thanks for sharing.
-Dan

February 28, 2004 06:38 PM Forum: Equipment Talk

What do you think, Legit or Scam?

Posted By Dan D DuBal
FYI -- here's an excerpt from Astromart's policy regarding use of the message boards (forums):

"...The following are cause for suspension from the boards or possibly Astromart, depending upon the nature of the posting: Posting contact information about another individual, including their real-world name, address, or phone number. Using profanity or hate speech. Posting material (graphic or text) of an adult nature. Posting information about another on-line astronomy classified and/or auction service..."

Best wishes.
-Dan

February 29, 2004 06:26 AM Forum: Bad to the Bone Autos

Umm, Bad like HOT? or bad like, well...BAD

Posted By Dan D DuBal
I very-much LIKE.
Thanks, Tony.
Best wishes.
-Dan

February 29, 2004 05:20 PM Forum: Meade

Meade 152ED/APO Collmination

Posted By Dan D DuBal
My hunch is that the 152ED's objective is a smidge (or would that be a *smudge*?) misaligned -- the objective's axis is tilted with respect to the scope's mechanical axis. Net result is coma (and some astigmatism). You can verify this with a high-magnification star test and/or by viewing the extra-focal patterns (fresnel rings) on either side of best focus. When the objective is tilted with respect to the optical axis, you'll see non-centric fresnel rings -- an off-kilter bull's-eye pattern, similar to figure D in the .pdf which Bob noted. Even a millimeter can skew things and show that smear or flare you're seeing.

If/when you make adjustments, do so "straight through" -- without a star diagonal in place. And if you end up going solo, I recommend using simple sketches to record the progress of the focal and fresnel patterns -- before 1st tweak, after 1st tweak, after 2nd tweak, etc. Nothing fancy -- a circle on paper where you can note positions/orientations of the brightest/best "point" of focus -- similar to a clock face.

Although the process can be tedious, correcting misalignment is pretty-much straightforward. You do have one big/huge advantage -- the adjustable cell simplifies the process *very* much.

Best wishes and luck.
-Dan

March 5, 2004 02:19 AM Forum: Astro-Physics

For the APUG

Posted By Dan D DuBal
...(drool drool) *pant*...

{:-P

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