Re: [APML] 2 new images

[Wei-Hao Wang <wang@ifa.hawaii.edu>]

Hi Jerry,

I would say, Centuria 800 is simply a grainy and perhaps high-speed
version of Centuria 400.  Both have low reciprocity failure under
low intensity.  Both are sharp.  It was confirmed that Centuria 400 
has very good red (H-Alpha, in particular) and blue sensitivity.  
Ron Pearson posted a comet picture by Centuria 400 on Astromart.  
>From that picture, it seems that Centuria 400 is sensitive to green 
light as well.  

I only used E200 one or two times.  So I cannot comment too much
about Centuria vs E200.  Judging from other people's pictures by
E200, Centuria 400/800 seems to have better RGB balance over
E200.  E200 is too red.  Centuria seems more grainy than E200.  
This month, I used Centuria 800 and E200 on the same target and
with the same telescope setup.  After I scan and process the 
images, I should be able to make better comparison of these two.

I have a larger picture of IC2177:
http://www.ifa.hawaii.edu/~wang/gallery/picutres/I2177-large.jpg
Although the images is a stacked of threee shots and is heavily 
smoothed in PhotoShop, you can see the noise (grains) of Centuria
800.  

About measuring stellar diameters, I do this on the scanned images.
For example, my scanner is a 1600 dpi one.  1600 dpi means that
each pixel is 25.4mm/1600 = 16 micron.  So if a star has diameter
of 3 pixels, its physical diameter is ~50 micron.

Cheers,

Wei-Hao

______________________________________________________________________
Wei-Hao Wang  :)

Institute for Astronomy at University of Hawaii

Address:                       Phone: 808-956-9867                  
2680 Woodlawn Drive            Personal Website:
Honolulu, HI 96822             http://www.ifa.hawaii.edu/~wang
______________________________________________________________________



On Thu, 26 Feb 2004, Jerry Lodriguss wrote:

> 
> Hi Wei-Hao,
> 
> These are some very nice shots. The Centuria 800 looks great, at least at 
> web resolution. The color sensitivity is great too. Do you find the 
> Centuria 400 to be pretty much the same?  How would you compare it to E200?
> 
> How did you measure the star diameters?
> 
> Jerry
> 
> 

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