Re: [APML] 4x5 astrocamera (again?)

["D. Kodama" <kodama@alumni.caltech.edu>]

Wei-Hao,

Thanks for the info.  I now have some E100S, so when I get a chance to
shoot some it will be interesting to see if I get the same green cast.  If
so, then I'll try another processor.

As I mentioned, the scope I'm using (Borg 100ED) has published specs of
minimum spot sizes smaller than 20 microns at f/4 (using their super
reducer), so if it is performing to spec, the sampling could be marginal.
The curves are here:

  http://www.sciencecenter.net/hutech/borg/techdocs/100.pdf

In practice, factoring seeing and tracking into the real world images, it
could be too conservative to sample at 10 microns, but I prefer not to
weaken any part of the imaging chain if I can avoid doing so.

By the way, where can the specs for the Pentax 67 lenses be found?  I have
the 75, 105, and 300 lenses.

Dave

> Hi Dave,
>
> E100SW has a warmer color because its blue density is suppressed.
> In terms of red sensitivity, there is no difference between E100S
> and E100SW.  The tech data for E100S/SW on kodak.com are incomplete.
> You can look at the tech data for E100G/GX.  They have identical
> spectral sensitivity and spectral dye density.  The only difference
> is their B HD curves.  However, the difference on actual slides
> is really small and should not be like what you described.  I never
> had this when I used E100SW before.  I suppose there is something
> wrong with the film or development.
>
> Loke made a good point about scan resolution.  2500 dpi sounds low
> according to today's standard but is high enough for most astro work.
> I'm not familiar with 4x5 lenses so cannot comment on this part.
> If you are using a telescope (such as an APO + field flattener),
> you can expect 30 to 40 um stellar size at the field center using
> E100S or Provia 100F.  This means 15 to 20 um pixles (1200 to 1600dpi)
> are enough even for the highest resolution region on your film.  This
> should help to decrease your file size without losing details.  If you
> compromise between the center and edge of the field, you can even
> use 1000 dpi.
>
> My scanner can only do 1600 dpi.  The finest star I ever got with my
> refractor is 30 um so 1600 dpi is enough for me.  On the other hand,
> Pentax 67 lenses produce stars smaller than 20um.  For these pictures,
> I feel I need at least 2400 dpi.  If this is also the case for you,
> then you have to live with 750MB files.  My largest mosaic has about
> this size.  You are not alone.
>
> 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 Fri, 7 May 2004, D. Kodama wrote:
>
>>
>> Wei-Hao,
>>
>> Thanks for the info on 4x5 film choices.  I recently picked up my own
>> combo 4x5" and 6x9cm setup (Mitsuboshi) so the info is appreciated.
>>
>> Regarding E100SW, awhile back I tried it in 4x5 format but found that it
>> had a tendency to go to yellow-green on long exposures.  I thought the
>> "W"
>> (warm) version of E100 would have better red response for nebulosity,
>> but
>> the green seems to overwhelm things.  I'd be interested in hearing if
>> anyone has had a similar result.  I just shot a couple of test frames
>> before becoming too busy to proceed further.
>>
>> By the way, one of the "downsides" of 4x5" is the size of the digital
>> files.  My scanner can only do 2500 DPI, but at that resolution a 48-bit
>> TIFF file is 750,000,000 bytes!
>>
>> Dave Kodama
>>
>>
>> > Date: Thu, 6 May 2004 15:27:29 -1000 (HST)
>> > From: Wei-Hao Wang <wang@IfA.Hawaii.Edu>
>> > Subject: Re: [APML] 4x5 astrocamera (again?)
>> > To: astro-photo@seds.org
>> > Message-ID: <200405070133.i471Xml07592@galileo.ifa.hawaii.edu>
>> > Content-Type: TEXT/plain; charset=us-ascii
>> >
>> > Hi Bobby,
>> >
>> > Yes, E100S is discontinued.  Now only 4x5 format (perhaps some
>> > 120 format E100SW) is available.
>> >
>> > Wei-Hao
>>
>>
>>
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>>
>
>
>
>

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