Re: [APML] Tech Pan lives! (and a newish image)

[KGKIRKLEY@aol.com]

In a message dated 1/18/02 12:48:49 AM, jmirtle@shaw.ca writes:

>Thanks Bert;
>
>    50 minutes is about as long as I can go with the Schmidt/W92 combo
>before the negative turns into a solar filter! To think of it another way,
>4 minutes with an f1.5 Schmidt is about the same effective exposure as
>1 hour at f6. The wratten 92 isn't as effective as the Lumicon Ha filter,
>which in turn isn't as effective as the Custom Scientific filters but you
>have little choice with Schmidts - they are focused for Wratten filters
>only. If I could just get a Custom Scientific model in 8" diameter........
>:-)
>
>
>
>John Mirtle
>
>Calgary, Ab. Canada

John:
50 minute exposure with an 8inch f1.5 Schmidt with W92 and hypered Tech Pan 
is a very long time.

I use the very same set-up and if I went 50 minutes, my negs would be 
bullet-proof.
Under very dark skies, West Texas, Oklahoma Panhandle I find that 30 minute 
exposures produce beautifully rich negatives for most parts of the sky. For 
the summer southern Milky-Way, 15 to 20 minutes is about all I'll go or the 
negs are bullet proof too.

I hyper the Tech Pan by dessicating with a vacuum pump for 15 hours and hyper 
for 8 hrs. @ 50 C in forming gas. I process in D-19 for 6-8 minutes to get a 
base fog density of .4 to .5. 

Kent Kirkley

--  APML Archives at <http://astro.umsystem.edu/apml/>  ---
             Unsubscribe at <majordomo@seds.org>