Re: [APML] M31 filter?

[Philip Perkins <philip@astrocruise.com>]

Greg,

Roland's suggestion is the way to go.  I don't think filtering would be 
very effective at reducing the core because M31 is all broadband light and 
the colour difference in the core is due to a bias towards the red part of 
the spectrum, but there is still plenty of light in the remainder of the 
spectrum.  As for exposure times, I have no experience of tech pan, but if 
I was exposing hypered colour film using similar instrument and camera to 
yours, I would expose between 70 and 90 minutes depending on the darkness 
of your sky and the elevation of the object above the horizon.

--Philip

At 11:30 20/07/02 -0700, you wrote:
>Suggestions on exposure times?
>I've never used Hypered Tech Pan before.
>AP 6" f7.5
>Pentax 6x7 and 4" FF
>
>Chris1011@aol.com wrote:
>>In a message dated 7/20/2002 1:12:27 PM Central Daylight Time, 
>>mueller@silverlink.net writes:
>>
>>
>>>Since the inner core of M31 is different color (wavelength)
>>>than the fringes, does someone know of a filter that would effectively
>>>filter out the over powering core, but allow the fringes to come
>>>through. Needles to say I have enough core luminance, but I'd like to
>>>boost those hard to pull out blue edges
>>
>>I would take two images, one shorter exposure that brings out the core 
>>detail infull, and one very long exposure that burns out the core but 
>>shows the outer regions. Then layer the properly exposed core over the 
>>burned out one using Layers in Photoshop.
>>
>>Roland Christen



Philip Perkins - philip@astrocruise.com
Wiltshire UK & Luberon France
Astrocruise - http://www.astrocruise.com


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