Re: [APML]Emission Lines Question and missing Veil

["Bert Katzung" <katzung1@attbi.com>]

Hi Bill:
That's puzzling. Are you *really* sure it was in the FOV? At f/1.5 a 30
minute exposure should certainly put significant image on the film. If you
compare with my (terrible) film image (LE400) at
http://www.astronomy-images.com/images/Nebulas/veil.6992.htm you can see
plenty of image at 60 minutes through an IDAS filter at f/4.5 and 30 minutes
with no filter. Faster film, but your faster optics should easily make up
for it. As far as emission lines are concerned, most of the Veil is H-alpha
as far as I know. Visual observers like the OIII filters because you can't
see much of anything through an H-a filter and there is enough OIII emission
to make it visible while increasing contrast.
Can you try a faster film or do some fancy calibration of your pointing to
check this out?
Bert

Bert Katzung
katzung1@attbi.com
www.astronomy-images.com

----- Original Message -----
From: "William R. Mattil" <wrmattil@ix.netcom.com>
To: <astro-photo@seds.org>
Sent: Tuesday, September 03, 2002 4:32 PM
Subject: [APML]Emission Lines Question and missing Veil


> Gentlemen,
>
> I have a question that perhaps some of the more knowlegable members
> could shed some light on for me. I have tried to image the Veil Nebula
> twice now (two seperate occasions) and  failed miserably. The failure
> doesn't bother me too much, but without knowing why I am probably
> setting myself up for further failures. Set-Ups were as follows:
>
> 8" Schmidt Camera (f/1.5) - ST-4 guiding a GM-100 mount. 90mm f/11
> guidescope. Side x Side
>
> Film used was unhypered Kodak Royal Gold 100. Exposure times were 30
> minutes.
>
> First Image on the roll was the Lagoon and it turned out ... well, Okay.
> Not a trace of the Veil could be seen in any of the images attempted.
> Now I may have been not exactly centered but the FOV is such that *some*
> trace should have appeared. The only explanation that makes sense to me
> is this. The RG100 may cut off in the Red quicker than I thought and the
> Lagoon simply has enough brightness to register. NGC7000 shows up also,
> but no Veil. Any ideas would be appreciated.
>
> I have compared the images taken with Sky Charts and confirmed that
> portions *should* definently be on the negative. Microscopic examination
> of the negative says no. I chose to examine it this way in case the 1
> hour Lab got overly enthusiastic about giving me a dark sky :^)
>
> A film change is probably in order for the next attempt.
>
> Any information or sources on the emission lines emitted by this ? And
> links to sources would also be appreciated. What is confusing is that
> Visual observers seem to like an OIII filter for this object. That would
> tend to point to something on the order of ~500nm wouldn't it ?
>
> Thanks in Advance
>
> Bill
> --
> William R. Mattil | Fred Astaire wasn't so great.
> wrmattil@ix.netcom.com | Ginger had to do it all backwards
> (972) 399-4106 | and... in high heels.
>
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