Re: Atypical variable stars...

[Thomas Droege <tdroege2@earthlink.net>]

Robert and all,

> If TN#40 is correct, parts were ordered for 10 cameras (so the
> question would be -- where are they???).

I actually ordered and received 40 ea.  5 element f/4 lenses.

I am not sure how many CCDs I ordered but it is about 40.  There are at
least 40 sets of camera parts.

> What wasn't clear from the documentation I've read is
> how many cameras/scopes were produced/installed.  The
> figures mentioned above would suggest much less than
> the map I ran across that suggested sites from Europe,
> the U.S. and Australia.
>

I wrote to a lot of people.  Slowly I sorted out where I sent a camera set.
Not very good luck getting recipients to operate them though.  The goal of
the exercise was to get someone to write working software.  It worked and
Michael Richmond wrote software that I could use to reduce the images.  So
now I am filling my house with telescopes, soon to be 5 pairs.

> It looks like details of the electronics TN#38, camera TN#40, and
> mount TN#42 may be available (though I do not see detailed schematics).

There are detailed schematics.  Each camera owner has a set so they are in
5 locations at the moment.  Some day perhaps someone will scan them in and
put them in a tech note.  There are about 40 B size prints.  Not easy to
read unless you know how things are supposed to work.  There are a few
write ups on this in the service notes, I think.

>
> If TN#40 is correct, parts were ordered for 10 cameras (so the
> question would be -- where are they???).
>

I have everything that I have not given away.  There are at least 3 systems
out there that are not being used (I think).  

> I understand this.  But it looks like the engineering behind
> the TASS effort is about 6 years old.  I actually built
> a CCD astronomy camera using a design from the mid-'90s
> for use in DNA sequencing applications though it was
> never tested (long story).  Given the advances in things
> like circuit density, FPGA's, "cheap" CCDs (???? for
> digital cameras, etc. I am wondering if there is a more
> current design/production effort to produce something
> a bit less expensive that can be put together by people
> with varied skills.
>

There have been no real changes in the CCDs used for astronomy.  Well,
people are getting better at thinning the chips and using back side
illumination to increase the sensitivity.  But there have been only limited
changes in the physics of the devices for 20 years.  Our project at
Fermilab uses back side thick chips to get IR response.  But other than
that they are similar in size (2k x 4k vs 2k x 2k of tass).  So CCDs are
not cheaper, they are more expensive as manufacturers are dropping out of
the biz.  A large device such as I use in first quality might cost $50,000.
There might be a gain in using many small devices, like the Kodak devices
which probably beat the astronomical CCDs in cost per square mm.  But then
you have the problem of patching them together in your focal plane, and you
get possibly 10% coverage of the focal plane.  What you save on the ccds is
made up in telescope cost.  All this turns out to be an engineering
optimization aiming at the cost to take a single measurement.  You can see
where I ended up.  

The CCDs used in cameras are an entirely different beaste.  One needs large
pixels which hold many electrons to get wide dynamic range for astronomy.

> I am under the impression that TASS III was operated in drift
> mode while TASS IV is operated in point and shoot mode.  Can
> anyone explain why the choice was made to sacrifice the potential
> sensitivity by giving up drift mode?
>

As soon as you get away from the equator drift scan does not work very
well.  TN-26 covers this.  
http://www.tass-survey.org/tass/technotes/tn0026.html

> Are there one or more pages that point out how to access
> the current database data?  (And is someone *really* keeping
> all of the data online???).
>

You bet.  "Hero of Tass"  Michael Sallman runs the data base.  

http://sallman.tass-survey.org/servlet/markiv/

takes you straight there.  

One of the way we sort people out in tass is that we don't give you
detailed instructions.  It is like playing "Adventure".  In adventure you
are not given instructions on how to move or that you have to pick things
up or that there is a vending machine to buy batteries for your flashlight.
You have to learn all these things by trial and error.  The same way with
tass.  If you can't figure out how to access the tass data base from the
above and the other links on the home page, then you probably don't belong
here.  It is not that we are against being helpful.  I have just spent an
hour or so trying to be helpful to you.  We just don't have the time or the
motivation to make the tass information available to those that have
difficulty with the above tests.  To keep things simple, updated and
problem free takes great effort.  We have better things to do.  There are
errors and problems with the tass site.  We fix what we can when it is
important.  You are free to step in and fix any problems you find.  Or to
improve anything.  It is like linux. 

Tom Droege







> [Original Message]
> From: Robert J. Bradbury <bradbury@aeiveos.com>
> To: Stupendous Man <richmond@stupendous.cis.rit.edu>
> Cc: <tass@listserv.wwa.com>; <mwrsps@rit.edu>
> Date: 8/24/2004 11:38:28 AM
> Subject: Re: Atypical variable stars...
>
>
> Michael wrote:
>
> >   Two sites (or more? correct me if I'm wrong!) are gathering
> > data each clear night.  One site's measurements are freely available
> > in an on-line database; the other's will be eventually.
>
> What wasn't clear from the documentation I've read is
> how many cameras/scopes were produced/installed.  The
> figures mentioned above would suggest much less than
> the map I ran across that suggested sites from Europe,
> the U.S. and Australia.
>
> >   I don't know of any single document which has all the information
> > on the design of the telescopes and detectors.  You can find a
> > great deal of information in a number of Technical Notes; browse
> > the list at
> >
> >         http://stupendous.rit.edu/tass/technotes/index.html
>
> It looks like details of the electronics TN#38, camera TN#40, and
> mount TN#42 may be available (though I do not see detailed schematics).
>
> If TN#40 is correct, parts were ordered for 10 cameras (so the
> question would be -- where are they???).
>
> >   If you want to build your own hardware which is identical to the
> > Mark IV, I'd guess many tens of thousands of dollars.  It is possible
> > to put together simpler wide-field camera systems using commercial
> > units for, oh, anywhere from a few thousand to fifteen thousand
> > dollars, depending on your preferences.
>
> I understand this.  But it looks like the engineering behind
> the TASS effort is about 6 years old.  I actually built
> a CCD astronomy camera using a design from the mid-'90s
> for use in DNA sequencing applications though it was
> never tested (long story).  Given the advances in things
> like circuit density, FPGA's, "cheap" CCDs (???? for
> digital cameras, etc. I am wondering if there is a more
> current design/production effort to produce something
> a bit less expensive that can be put together by people
> with varied skills.
>
> (One imagines auto mechanics who would have no problem
> assembling a telescope "kit" but wouldn't want to touch
> the electronics to EEs who have no problem putting together
> a PCB from scratch but would rather avoid things like
> drive motor mechanics...).
>
> I am under the impression that TASS III was operated in drift
> mode while TASS IV is operated in point and shoot mode.  Can
> anyone explain why the choice was made to sacrifice the potential
> sensitivity by giving up drift mode?
>
> >   No, there are no reasons such objects would be missing
> > from the TASS database, as long as they are bright enough to
> > be detected in both the V and I passbands.  But you would
> > have to go through the database to find them for yourself.
>
> Are there one or more pages that point out how to access
> the current database data?  (And is someone *really* keeping
> all of the data online???).
>
> Thanks for all the help.
> Robert
>
>