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Posts Made By: John Biretta

July 21, 2007 06:30 PM Forum: CCD Imaging and Processing/Solar System

August 25, 2007 04:03 AM Forum: Eyepieces

Re: Cleaning?

Posted By John Biretta

Be sure to read the MSDS carefully, especially
the parts about "explosions", "distant
ignition sources", and "sensitive to static
discharge." I've had the stuff flash and
explode while cleaning a mirror. Not something
I would recommend. If you've got a fire-proof,
static-free room with halon, then go for it.
But otherwise I'd leave acetone to the professionals,
and look to less reactive agents like 93% (or less)
alcohol. Or some of the enzyme based cleaners.

The other reason to avoid it, as if one needed
a second reason, is that it will dissolve most
of the stuff used to blacken lens edges. Unless
very careful, you can quickly get a black smeary
mess all over your nice lens -- one which will
make a finger print or water spot look like nothing
at all.

MSDS Acetone:

5. Fire Fighting Measures
Fire:
Flash point: -20C (-4F) CC
Autoignition temperature: 465C (869F)
Flammable limits in air % by volume: lel: 2.5; uel: 12.8
Extremely Flammable Liquid and Vapor! Vapor may cause flash fire.

Explosion:
Above flash point, vapor-air mixtures are explosive within flammable limits noted above. Vapors can
flow along surfaces to distant ignition source and flash back. Contact with strong oxidizers may cause
fire. Sealed containers may rupture when heated. This material may produce a floating fire hazard.
Sensitive to static discharge.

October 7, 2007 12:30 PM Forum: CCD Imaging and Processing/Solar System

Re: Venus in orbit

Posted By John Biretta

Very nice!!

November 2, 2007 12:06 AM Forum: Refractors

Re: TMB Designed APM 152mm f/8 Achromat

Posted By John Biretta

Buy a used Celestron CR-150 (or clone) for $250 - $400.
Remove the old lens, and re-drill the lens cell flange
to accept your lens.

November 2, 2007 07:02 AM Forum: Refractors

Re: TMB Designed APM 152mm f/8 Achromat

Posted By John Biretta

Another thought. Perhaps a Meade AR-5 OTA would
be a better choice. On the CR-150 the dew shield
mounts to the lens cell, but on the AR-5 the
dew shield mounts to the OTA main tube. On an AR-5
the dewshield would already be mounted for you.
There are some old pics of a AR-5 here
http://www.astromart.com/classifieds/details.asp?classified_id=470884
Could probably find an AR-5 owner and get them to
take some measurements for you, to make sure your
lens cell will fit the tube.

Some outfits (handsonoptics.com, antaresoptical.com)
might even sell you an empty OTA tube (no lens)
or the parts.
http://www.antaresoptical.com/atm.htm

Moonlight sells a nice focuser upgrade for couple
hundred bucks, if you don't like the stock one.

November 10, 2007 01:13 PM Forum: Equipment Talk

Re: Unknown Adapter

Posted By John Biretta

Sounds like an adapter that will allow you to use your
Celestron accessories on smaller scopes that
have a standard 36.4mm (1 3/8") thread on the back.
Sometimes call a Large Accessory Ring or LAR.

January 5, 2008 01:05 PM Forum: Chinese Optics Imports

Re: CHINESE MADE 152MM APO IN CELL

Posted By John Biretta

They obviously have an interferometer. See if they
will agree to include an interferogram with matching
serial numbers for each lens. And promise that minimum
quality is 0.25 wave PTV, and RMS is no
worse than 0.025 wave, on the interferogram.
(Strehl in green then about 96% or better). That would
make the deal in my view. Also find out what their
after-sale warrantee is. For example, if it goes out
of collimation during shipping from China, etc.
Or has bad behavior at cold temperatures. I would try
to get this agreement, rather then pushing the price
much lower. For a good lens, this is a great price
already. But if quality is bad, any price is too much.

February 15, 2008 11:39 AM Forum: CCD Imaging and Processing/Solar System

Mars from WSP2008

Posted By John Biretta


Here's a shot of 11 arcsec diameter Mars
from Winter Star Party last week. Breezy conditions
made for merely "good" seeing, though there were some
moments with very nice image detail.

Exposure details:
02/07/2008 3:17-3:28 UT from Winter Star Party 2008
StarMaster 16" F4.3 on Tom O. Equatorial Platform
TeleVue 5x Powermate
Baader UV/IR cutoff filter
Lumenera SKYnyx 2-1C color camera, 19fps, 51msec/frame
1500 of 10000 frames
Aligned and stacked in K3CCD v3
Wavelet processing in Registax 4.0

- John B.

March 30, 2008 01:34 AM Forum: CCD Imaging and Processing/Solar System

Saturn from WSP 2008

Posted By John Biretta

Hi folks,

Here's a shot of Saturn from Winter Star Party
back in Feb. Been too busy for much processing.

Taken with StarMaster 16 using a TV 5x PowerMate (F22) and
Lumenera SKYnyx2-1 color camera. All riding on a
Tom O. EQ platform. Used 16 FPS and about 1500 frames
(out of about 2400 frames). 9 Feb 2008 0032-0038 UT.

Seeing was not up to the "usual" WSP standards. Not many
frames at full diffraction limited resolution, but enough
to pull out some details. Cassini most of the way around
and bits of Enke gap in the corners.

- John B.

May 16, 2008 03:04 PM Forum: AstroMart FAQ

Re: Unscrupulous?

Posted By John Biretta

My feeling it that its pretty early to be getting this
worked-up about it. Regardless of what he may have
promised, most people would feel it is reasonable to
receive payment before shipping an item, and perhaps
even waiting for the check to be deposited and cleared.
So that would put a plausible ship date around May 5
or even later, depending on whether it was international,
etc. Depending on how it was shipped, it could still
be in transit somewhere. I think all that is clear at
this point, is the seller is not a great communicator,
but thats pretty far from any irregular or fraudulent
activity. More likely they are just busy, having
some crisis, hospitalized, pending divorce, etc.

The other person's experience with this seller is not
really relevant, except it might serve as a warning
for the future.

IIRC, USPS will refund your money order after 30
days (?), if it has not been cashed. I had to go that
route once, but its been a few years, so details are
fuzzy. That might be one resolution for you. You
fill out some form, and USPS sends you a check for it.

For now, I'd just be patient, and keep trying to make
contact. Good luck!