Re: [APML] AP 130/F6 LPR filter help

[Matthias.Felsch@t-online.de (Matthias Felsch)]

----- Original Message ----- 
From: Gerry Cichocki <gcichocki@hotmail.com>
To: <astro-photo@seds.org>
Sent: Thursday, February 22, 2001 2:18 AM
Subject: Re: [APML] AP 130/F6 LPR filter help

Hi Gerry,

I tried the Tokai/IDAS filter with my AP130/F6.

I put the filter (just for a quick test... not as a permanent solution) 
into an Astro-Physics extension tube, that I happened to have.
It was pure tinkering... but before spending money on a custom made
filter holder, I wanted to perform a little testing.
So the filter (it's the glass of the 67mm- version, that I took out of the metal ring) 
sits between the 2.7" focuser and the field flattener, about 3.5 cm (app. 1.4 inch) 
from the flattener's front lens.
It works very well, I don't have more vignetting than this combo
(130EDF / fieldflatterner with the 2.7" focuser) normally produces without the filter
(and it *does* produce a little vignetting... in addition to the one caused by the small 
opening of the pentax body .....I wish, I could buy a 4" focuser  and a 4" flattener lens 
for
the 130 EDF....). 
Since with the filter the background is not so present in the slide, the vignetting 
even seems to be reduced.... but if I really expose to the sky fog limit or further (what 
I
did), I can see it again (of course)....

Regarding reflections, there was only one:
I found a single blue reflection (a kind of halo) in a picture of M42, around jota 
orionis.
I took images on E 200 of the rosette, of IC 410 and 405, of M38 with LBN 794, 
of IC 1805 (Heart Nebula), but the very bright jota orionis was the only star with such a 
visible halo.

Normally, without the filter, I don't have such halos around bright stars.
The halo is a rather "sharp" disc, like the one, jota produces on the film, but
app. 10- 20 % bigger in diameter and blue. It is not completely concentric to the disc
of the star itself; jota was near the center of the field, but not exactly in the middle.

I'm not quite sure, wether this halo in fact is related to the use of the filter, but I 
tend to
think it is. Jota was the brightest star on all the images, I took with the filter.
Unfortunately I don't own a scanner yet, so I can't show you the halo.

On the other hand, it's not a real dramatic thing, this little halo; it should be very 
easy to
remove it digitally.

Well, so far I'm very content with the results of my filter experiments.... I plan to 
have made
a custom filter holder now.. (with the option to rotate the camera....)
You should see the provisional "filter holder", I use at the moment.... it looks
completely ridiculous...<g>   but it works.... 
Hm, do I really need the custom made filter holder for a lot of $$$ or DM ?? <bg>

Matthias


> Anyone out there actually photograph with the LPR filter & field flattener 
> on a 130/F6 ? If so how & where did you install the filter? and was there 
> any vignetting or reflections? Gerry
> 






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