[Aavso-photometry] ST8-ST9-ST10

[Wolfgang Renz]

There are also some others:

Wise Observatory - Utilities - Signal to Noise (S/N) Calculator 
http://wise-obs.tau.ac.il/~eran/Wise/Util/SNcalc.html


CALCULATOR for Magnitude Limits for CCD and Telescope
http://www.go.ednet.ns.ca/~larry/astro/ccdlimit.html


Clear skies
 Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO



----- Original Message ----- 
From: "Michael Sallman" <msallman at pro-ns.net>
To: <aavso-photometry at mira.aavso.org>
Sent: Saturday, June 16, 2007 2:16 PM
Subject: Re: [Aavso-photometry] ST8-ST9-ST10

> Gary and all,
> 
> There is also a similar calculator online here:
> http://www.tass-survey.org/richmond/signal.shtml
> 
> Mike SVI
> 
> 
> 
> BailyHill at aol.com wrote:
>> Hello;
>>  
>> Been lurking for the referenced discussion.  Had 2 experiences that I  wanted 
>> to share.
>>  
>> Went to NEAF this year with the idea of upgrading from my ST10  camera.  
>> Talked to several manufacturers and found one that had a camera  with back 
>> illuminated E2V chip, super cooling, very low read noise,  extraordinary a/d 
>> converter---etc.  Came away thinking I would buy  one.  The fact that I had just sold 
>> a piece of equipment and had cash in  hand, made the argument even more 
>> compelling.
>>  
>> Had a discussion with Arne at the MMO (Maria Mitchell Obs) opening to  
>> celebrate their new 24 inch RC.  Arne and I did some ratios, extrapolating,  etc, 
>> and came to the conclusion that the new hot camera would not necessarily be  a 
>> miracle for reducing the errors.  However, aperture seemed like it might  be a 
>> big winner.
>>  
>> So I dug out an old Sky and Tel article, Feb 93, by Sinnott and Mallama,  
>> where they had a Basic Program to calculate the SN of a Telescope and  Camera.  
>> The program took aperture, FWHM, sky background, read noise, dark  current, 
>> scope focal length, & pixel size into account.  I converted it  to a spreadsheet, 
>> expanded the program to include binning, QE of the chip, and  filter 
>> throughput.  Now I could compare various scenarios.
>>  
>> Arne was right-what's new-the cameras make a small difference.   Aperture 
>> makes a large difference.  
>>  
>> So I decided to run the numbers for the ST8, ST9, thru my ST10 in for  
>> comparison.  For a 10 inch telescope, with 2500 mm focal length, 20 mag/arc  sec 
>> squared skies, all binned 1x1, Imaging a 15 magnitude star, with fwhm of 3  arc 
>> seconds;  the following SN ratios were calculated.
>> ST8 = 25;     ST9 = 27       ST10 = 32
>>  
>> If we 2x2 so we have 18 and 13.6 micron pixels respectively; we get
>> ST8 = 32      ST10 = 46
>>  
>> and if we bin 3x3 so we have 20.4 micron pixels; we get
>> ST10 = 52
>>  
>> So no miracles, but a quantifiable result.  I have checked at  least the ST10 
>> results with what I get on my 12 inch telescope, and it seems to  be close.
>>  
>> Epitaph:   Well the big Winner from the NEAF show was the 20 and  24 inch 
>> scopes.  As an example, the above scenario with the ST10 with a 20  inch jumps 
>> the SN from 52 to 112---Wow a big difference.  Unfortunately the  cost of the 
>> new tube is much more than the new camera, so I am sitting in  somewhat of a 
>> dilemma.  
>>  
>> Clear Skies
>> Foggy in Nantucket
>>  
>> Gary