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Posts Made By: John Biretta

September 25, 2005 04:52 PM Forum: Refractors

Re: Reasonably priced mount...

Posted By John Biretta

I've use this on a Losmandy G-11 with acceptible results,
but make sure you get the Gemini drive as the servo motors
are much smoother than the stepper motors. But it is just
big and heavy enough, and enough setup effort, that it does
impact my viewing. At least 5 trips outside with really
heavy stuff to set it up (tripod, head, weight shaft+weights,
battery+OTA rings, OTA).

I also tried it on a GM-8 once or twice. Setup is much
easier, but the stability is barely adequate. I would not
recommend it.

September 30, 2005 10:26 AM Forum: CCD Imaging and Processing/Solar System

Anyone using Toucam NO-RAW mod?

Posted By John Biretta

One feature of the Toucam that has sometimes bothered me
is the in-camera image sharpening. It sometimes generates
over-shoot artifacts where the image suddenly
goes from bright to dark (stars, planet limb, etc.).
Over on the Cloudy Nights forum I noticed some discussion
of a firm-ware mod on the Toucam to shut off the
image sharpening. It seems to be called "NO-RAW mod"
or "optimized color mod." There was some discussion
about it roughly 9 months ago, but not much since.
Is anyone using this or tried it?

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/1,2,3,4,5,8,9,10/Number/256719/page/0/view/collapsed/sb/5/o/all/fpart/1

October 5, 2005 01:13 AM Forum: CCD Imaging and Processing/Solar System

Mars Monday AM

Posted By John Biretta

Finally got some nice seeing and was ready for it.
C9.25 + TV 4x + 1.6x. Toucam 740 with the NO-RAW mod;
mod seems to help, though there is still some ringing
at the limb. 15fps. 600 of 2250 frames with Registax.

Interesting to compare with Alan's beautiful image taken at
about same time; nearly every feature shows up in both.
I have sometimes been a skeptic of image processing, but
it is obvious there is considerable reality to these images.

I have been wondering if the ringing at the edge was partly
due to the large central obstruction in these SCTs. Perhaps
it is a manifestation of the bright first Airy ring?
Processing seems to pick-up on it and further accentuate it.
Comments?

January 5, 2006 06:47 AM Forum: Refractors

Re: New Meade S5K ED

Posted By John Biretta

Wasn't there some Meade ad copy about 8 years ago
to the effect that "triplets are poor lenses for
astronomy because the middle element will never
cool down?"

March 8, 2006 11:40 PM Forum: CCD Imaging and Processing/Solar System

Saturn from WSP

Posted By John Biretta

Saturn from Winter Star Party in nice seeing.
StarMaster 11 on a Tom O. platform with ToUcam.
5000 frames over about 20 minutes (rotation probably
smears fine details on the planet). Enjoy!
- John B.

March 15, 2006 11:01 PM Forum: CCD Imaging and Processing/Solar System

Another Saturn from WSP

Posted By John Biretta

Still digging through AVIs from Winter Star Party. Another nice
one from a different night. I like the coloration of this one
perhaps better. Slightly more detail. Ball of planet seems
visible through outer A ring, but not B ring.

March 18, 2006 07:49 AM Forum: Eyepieces

Re: Repair Issues with EPs

Posted By John Biretta

(1) Dust, haze, crud between the elements is one reason
for factory service. If you are careful in storing
and using the eyepieces, it will probably be a very long
time before this is an issue.

(2) Cement between elements becomes cloudy or separates
from glass. I see this alot in certain brands of
eyepieces from the 60s and 70s.

(3) Lens coatings flake off. Usually if they are
properly coated this does not happen. But again I have
seen a fair number of very old eyepieces where the
coatings are partially gone, even on the internal surfaces.
I suspect they were not coated properly in the first
place. I can think of two models of old eyepieces where
everyone I have seen has the coating coming off one
particular surface inside.

April 7, 2006 02:34 AM Forum: Astro-Physics

Re: Elephant in the room?

Posted By John Biretta

Whatever Roland is working on, I am sure we will not
hear about it until it is nearing delivery. AP does
not seem to traffic in "vaporware." And I'm sure both
you and Roland want it to be worth the 6+ year wait.
As you indicate there are many other worthy entries
into the 4" - 5" APO market, and I expect the challenge
of producing a truly exceptional scope is increasing.

April 18, 2006 08:23 AM Forum: AstroMart FAQ

ioptics?

Posted By John Biretta

When you click on the ioptics sponsor link, you get
a blank page and error message. Sounds like they
make great stuff (zerodur flats?), wish I could get
some info. They have no website, no contact info?

June 18, 2006 07:39 AM Forum: Equipment Talk

Re: Naglers & Schiefspieglers & f/3.5?

Posted By John Biretta

Herbert, Another interesting post.... some comments....

You are making too much of the F/3.5 light cone & eyepiece business. The F/20 Schief light cone, while 7 degrees off axis, is still F/20. It does not have the same eyepiece aberrations as a filled F/3.5 light cone, since only a tiny portion of the F/3.5 is illuminated. Below I will include a spot plot for an F/20 Schief with an old fashioned 6-element Erfle. All of the light is well within the Airy disk shown by the circle. Whats the problem? There is no problem.

In my next message I will post the same Erfle in an F/5 Dob. The performance of the Erfle in the F/5 Dob is similar (maybe a little worse) than the Schief. 1980's eyepieces killed the Schief no more than they killed the Dob.

I can report that Naglers work fine in Schiefs. But Erfles were fine too.

Next lets talk about size and weight. Whats your comparison scope? Lets compare apples and apples -- un-obstructed, apochromatic systems for planetary observing. An 8" F20 Schief is about 60 pounds and 68" long. A nice 8" F9 TMB APO refractor is 68 pounds and 65" long. Pretty similar.

Three mirrors? No more than your average SCT, Mak-Cass, Classical Cass + diagonal. I don't see this as a big deal.

So... bring out your Schiefs.... the waters fine....