> A few years ago I remember reading an article in S&T (I think) about
being
> able to view solar promences (SP) by using a combination of 3 relativly
> cheap color eyepiece filters (of course in combination with a suitable
solar
> filter in front of the corrector plate). The article claimed that this
> "arrangement" produced results comparable to those obtained with a
$3,000.00
> sub angstrom HA filter. Does anybody in the MAPUG world remember this
article?
>

A standard solar filter reduces light at ALL WAVELENGTHS by 10,000 to
100,000. So it is completely impossible to see any proeminence with a
filter of this kind.
In order to see anything you need a objective filter called "Energy
rejection Filter" (ERF) that almost eliminates UV and other unwanted
wavelengths and let pass about 50% of the H-alfa wavelenght. Remeber that
proeminences are seen at only one wavelength: the H-alfa.
Now, if you combine two eyepiece color filters you will get only the common
area of both. The ideia there should be to use two or more filters with a
common area around the H-alfa wavelength.
The problem is that in order to see proeminences you need to have a very
narrow bandpass (<3A), wich I seriously doubt you can get with standard
color filters.
If you dont want to spend the money of a DayStar filter try a Lumicon or
1000 Oaks 1.5A filter around $800 complete. You will have to get the ERF
anyway.

Pedro Santos

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