UHC chromatic aberation?

Hi,

I just bought UHC filter and tried to see a few objects with it. I see
big improvement when watching planetary nebuli and little but
noticeable when watching difuse nebuli. I have 114mm f/8 homemade
babydobson.

I also notices a few unexpected things:
- I can't focus as good as without UHC
- When i watch Saturn, I see multiple (green-blue and red) pictures of
it. Red picture is ussualy dancing around blue one. It's funny, but...
- Mu Cephei looks extremely strange - I see white dot "swimming" in
red patch.
- When I look street lights, they have red and blue images. Red is
shifted to the side.

Is all this normal?

Ante Perkovic
--
http://astro.fdst.hr

"Ante Perkovic" wrote in message
om...

Is all this normal?

I sure hope so. Otherwise I got a bad one too.

OTOH, it works really well on nebula, so I don't care.

"Ante Perkovic" wrote in message
om...

Is all this normal?

I sure hope so. Otherwise I got a bad one too.

OTOH, it works really well on nebula, so I don't care.

Ante Perkovic nous a écrit :

Hi,

I just bought UHC filter and tried to see a few objects with it. I see
big improvement when watching planetary nebuli and little but
noticeable when watching difuse nebuli. I have 114mm f/8 homemade
babydobson.

I also notices a few unexpected things:
- I can't focus as good as without UHC
- When i watch Saturn, I see multiple (green-blue and red) pictures of
it. Red picture is ussualy dancing around blue one. It's funny, but...
- Mu Cephei looks extremely strange - I see white dot "swimming" in
red patch.
- When I look street lights, they have red and blue images. Red is
shifted to the side.

Is all this normal?

I think it is normal. What you see in red and blue are the reflections of
the light on the two faces of the filter.

--
Norbert. (no X for the answer)

======================================
knowing the universe - stellar and galaxies evolution
http://nrumiano.free.fr
images of the sky http://images.ciel.free.fr
======================================

Ante Perkovic nous a écrit :

Hi,

I just bought UHC filter and tried to see a few objects with it. I see
big improvement when watching planetary nebuli and little but
noticeable when watching difuse nebuli. I have 114mm f/8 homemade
babydobson.

I also notices a few unexpected things:
- I can't focus as good as without UHC
- When i watch Saturn, I see multiple (green-blue and red) pictures of
it. Red picture is ussualy dancing around blue one. It's funny, but...
- Mu Cephei looks extremely strange - I see white dot "swimming" in
red patch.
- When I look street lights, they have red and blue images. Red is
shifted to the side.

Is all this normal?

I think it is normal. What you see in red and blue are the reflections of
the light on the two faces of the filter.

--
Norbert. (no X for the answer)

======================================
knowing the universe - stellar and galaxies evolution
http://nrumiano.free.fr
images of the sky http://images.ciel.free.fr
======================================

Misusing any filter will get you into troubles. Look at the UHC filter and
you will see that it filters for two bands and that is what you are seeing
on broadband light sources.
The purpose of the UHC filter as well as any of the other light polution
type filters is to bring out the ionized oxygen and hyrdogen light from the
background and thus you can see the nebulas a lot better.
Next, the filter will make a pair of images in the red and bluegreen with no
other light between and about so you are going to see the images as seperate
with the color errors that your EPs are producing on the images.
Please use the filter for what it is intended to be used for, dropping the
background level of the broadband light so that the spectral colors of the
nebula will stand out brighter.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works evevery time it is tried!

Misusing any filter will get you into troubles. Look at the UHC filter and
you will see that it filters for two bands and that is what you are seeing
on broadband light sources.
The purpose of the UHC filter as well as any of the other light polution
type filters is to bring out the ionized oxygen and hyrdogen light from the
background and thus you can see the nebulas a lot better.
Next, the filter will make a pair of images in the red and bluegreen with no
other light between and about so you are going to see the images as seperate
with the color errors that your EPs are producing on the images.
Please use the filter for what it is intended to be used for, dropping the
background level of the broadband light so that the spectral colors of the
nebula will stand out brighter.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works evevery time it is tried!

Hi there. You posted:

I also notices a few unexpected things:
- I can't focus as good as without UHC
- When i watch Saturn, I see multiple (green-blue and red) pictures of
it. Red picture is ussualy dancing around blue one. It's funny, but...
- Mu Cephei looks extremely strange - I see white dot "swimming" in
red patch.
- When I look street lights, they have red and blue images. Red is
shifted to the side.

Is all this normal?

Yes, it is. You should only use the UHC for viewing emission nebulae, as that
is what is designed for (in other words, don't use it on Saturn or other
things). What you are seeing is not "chromatic aberration" but the effects of
the multi-layer dielectric coatings which are used to create an interference
filter. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

Hi there. You posted:

I also notices a few unexpected things:
- I can't focus as good as without UHC
- When i watch Saturn, I see multiple (green-blue and red) pictures of
it. Red picture is ussualy dancing around blue one. It's funny, but...
- Mu Cephei looks extremely strange - I see white dot "swimming" in
red patch.
- When I look street lights, they have red and blue images. Red is
shifted to the side.

Is all this normal?

Yes, it is. You should only use the UHC for viewing emission nebulae, as that
is what is designed for (in other words, don't use it on Saturn or other
things). What you are seeing is not "chromatic aberration" but the effects of
the multi-layer dielectric coatings which are used to create an interference
filter. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

"Stephen Paul" wrote

OTOH, it works really well on nebula, so I don't care.

One nebula, two nebulae

A-one, and a-two, and-a.....