[Aavso-photometry] Start up question

[Rumrill, Donald M (US SSA)]

Thanks for excellent advice Arne, I appreciate it.  My main impetus
really is to build something myself; the challenge of designing a device
that precise and working with very low currents is what grabs me. Price
isn't really a concern (to a certain point!). I really started into this
whole thing over 30 years ago when I ground and polished a 6 inch
mirror.  Unfortunately they tore down the optical shop where I worked
and I never figured it.  It still sits on my garage shelf, but I finally
conceded that this wasn't going to happen until retirement, so I bought
an 8 inch Newtonian that satisfies me.  

Don




-----Original Message-----
From: arne [mailto:arne at aavso.org] 
Sent: Saturday, June 02, 2007 5:32 PM
To: Rumrill, Donald M (US SSA)
Cc: aavso-photometry at mira.aavso.org
Subject: Re: [Aavso-photometry] Start up question

Rumrill, Donald M (US SSA) wrote:
> Hello all,
> 
>  
> 
> I am a fairly recently started amateur "star gazer," though I've paid
> close attention to astronomy for many years.  I am thinking, that to
> give myself a little more focus than just gawking around the heavens,
> that I would look into photometry for a sense of purpose and perhaps a
> little contribution to the avocation.  Many years ago, I designed a
star
> simulator with a detector at the system's output as part of a feedback
> control to set and maintain the simulated star's magnitude.  I used a
> photodiode and boxcar integration to achieve this, with light levels
> down in the 10's of photons.  Based on this experience, my thoughts
were
> to build something similar to attach to my telescope and make
> measurements; similar to the photometers described in AASVO's on-line
> literature.  My question is this:  Given the state of art ofCCD
cameras,
> is it worth my while to build a photometer, or would I be better off
> saving my pennies and purchasing a CCD camera system?  I could
probably
> build a photometer for around $100 given my contacts within the
> electronics industry.  I haven't done an error budget yet, but expect
to
> be well under 0.1%.
> 
you can probably buy a used SSP-3 for not a whole lot more than $100,
and get filters included.  Might be simpler (though not as much fun)
as building your own.

Photoelectric photometers have their place.  They typically can yield
higher-quality data if skies permit, and are the only cheap way to do
high-speed work.  Since you are dealing with a single channel detector,
the data reduction is easier. At the same time, they do require
photometric skies and you cannot work as faint as you can with a CCD.

There are a few CCD systems available in the $500 range (such as the
Meade DSI Pro), and DSLR cameras can give reasonable (say, 0.1mag)
results,
if you want to get into CCD work in a simple way.  If I were getting
a new system from scratch, I'd probably go CCD rather than PEP as you
will have a wider range of projects that you can work on.  However,
if money is a problem, go with the solution that gets you measuring
stars now, and then think about PhaseII.
Arne