Which filter?

[houston]

Thinking of ordering a uhc or o-iii filter but cant decide which i would get most use of. Will be used mainly with 200p dob and sw 26mm panaview eyepiece.

[Spec-Chum]

Pros and cons for both Buddy, with one working better on some targets and vice versa.

It is said the the UHC is more of a general filter (ie works well on most targets) if you're only getting 1 I'd go for that.

Sent from my Nexus 4 using Tapatalk

[Reeny]

I got the OIII by mistake on the advice that:

- the UHC will only show you the stuff you can see already.

- the OIII will reveal the hidden nebula which are only visible with an OIII.

In practice the 8" and OIII used in town does not let quite enough light in for my liking.

The Ring and Dumbell nebula are the only two I have found so far without a filter.

Adding the filter changes the image - but darkens it so much that most of the clarity is lost

I will need dark skies and more practice to make the OIII work properly.

I will get there eventually, but in hindsight the UHC might have been a more forgiving filter to start with.

[houston]

Live in coventry so not great skies. Was thinking the uhc might be used more so will go for that i think.

[YKSE]

I got the OIII by mistake on the advice that:

- the UHC will only show you the stuff you can see already.

- the OIII will reveal the hidden nebula which are only visible with an OIII.

In practice the 8" and OIII used in town does not let quite enough light in for my liking.

The Ring and Dumbell nebula are the only two I have found so far without a filter.

Adding the filter changes the image - but darkens it so much that most of the clarity is lost

I will need dark skies and more practice to make the OIII work properly.

I will get there eventually, but in hindsight the UHC might have been a more forgiving filter to start with.

I'd like not to think that buying OIII was a mistake, the advice is correct IMHO.

I had a very difficult time to find any object when I got my first 130P for nearly a year ago, even though I knew some famous constellations, It was first after I got a Star Atlas I could star-hoping to right spot, even then it was difficult to see the faint fuzzies I was looking for, becaus of untrained eyes. But it was really satisfying when you found what you're looking for. It's much better not using any filter when star-hoping, and the widest possible EP make star-hoping easier too. UHC works better on more nebulae than OIII, but many times you really can see them without the filter.

I find B chart of this free star atlas very useful. http://www.uv.es/jrtorres/triatlas.html

Our light polluted skies make observing more difficult, but it also make it easier for beginners to recognize the constellations, you can always start star-hoping from a known position -even though may be a bit far away, and work slowly towards your target.

Also, no filter works on galaxies, the only way to see them is working systematically, and train our eyes.

About the filters, my advice would be "No hurry", get a star atlas and train your eyes first, when you decide to buy one, get an 2" one (UHC or OIII or both), you can put it in your 2" diagonal to work with all your EPs.

[Joves]

If you're wanting a more general purpose filter, definitely get the UHC. The OIII is a great filter also, but darkens the image to the point where you will actually lose some objects. I did a very rough comparison of different filters used to view the Tarantula Nebula on another similar thread on here only a day or so ago. I'll see if I can copy and paste that into here.

Yong, I wouldn't say it was a mistake getting the OIII filter, as it really is a fantastic one to own. It just won't give you as broad a range as the UHC does.

[Joves]

I have all of the Astronomik 1.25" filters and, personally, I think the UHC is a better "all-round" filter. It gives nice views of objects that are supposed to be best viewed with an OIII filter, but doesn't darken the image as much as the OIII itself. I also find the CLS to give very similar results to the UHC. Last night, whilst viewing the Tarantula Nebula (which is supposed to be best viewed with an OIII filter), I decided to do a comparison between each of them. I should mention that, whilst seeing was pretty decent, there were fair moments of haze and I live less than a km from Sydney CBC, so light pollution is about as bad as you'd expect it to be. The results were, as follows (in very basic format, of course):

No filter - could definitely see that the nebula was there, but had to use averted vision to see any distinct shape or detail

OIII filter - haziness completely gone, sky very dark, nebula easily seen with direct vision, but surrounding stars also pretty well gone. It's important, I think, to note that their is a strong glue cast when using this filter. Point the scope at a bright white star like Canopus and it is entirely blue!

UHC filter - haziness gone, but sky not quite as dark. Surrounding stars still visible. Nebula easily seen with direct vision.

CLS filter - haziness gone, but still a brighter sky than with the other filters attached. Nebula easily seen with direct vision, but not quite as distinct as with the OIII or UHC.

SII filter - extremely darkened FOV. Some surrounding stars visible, but barely a hint of the nebula.

Ha filter - nothing visible

Hb filter - nothing visible

Planet IR Pro filter - didn't try

L Filter Type 2C - didn't try

MC Klarglass - is just a clear glass filter, so didn't bother trying

Not sure if any of this helps at all, but there are definite differences between Astronomik OIII, UHC and CLS filters. They do very similar things, particularly the UHC and CLS, but there are absolutely noticeable differences. As for the SII, Ha and Hb filters, these are entirely different beasts altogether.

[houston]

Just got the 2" uhc. Trying to hide it from missus or she will be wanting to wrap it up for christmas with the eyepiece in the post.

Sent from my GT-I8160 using Tapatalk 2

[Joves]

Just got the 2" uhc. Trying to hide it from missus or she will be wanting to wrap it up for christmas with the eyepiece in the post.Sent from my GT-I8160 using Tapatalk 2

Good choice and well done. Be keen to hear how helpful you find it to be when you get a chance to use it!

[John]

I have all of the Astronomik 1.25" filters and, personally, I think the UHC is a better "all-round" filter. It gives nice views of objects that are supposed to be best viewed with an OIII filter, but doesn't darken the image as much as the OIII itself. I also find the CLS to give very similar results to the UHC. Last night, whilst viewing the Tarantula Nebula (which is supposed to be best viewed with an OIII filter), I decided to do a comparison between each of them. I should mention that, whilst seeing was pretty decent, there were fair moments of haze and I live less than a km from Sydney CBC, so light pollution is about as bad as you'd expect it to be. The results were, as follows (in very basic format, of course):

No filter - could definitely see that the nebula was there, but had to use averted vision to see any distinct shape or detail

OIII filter - haziness completely gone, sky very dark, nebula easily seen with direct vision, but surrounding stars also pretty well gone. It's important, I think, to note that their is a strong glue cast when using this filter. Point the scope at a bright white star like Canopus and it is entirely blue!

UHC filter - haziness gone, but sky not quite as dark. Surrounding stars still visible. Nebula easily seen with direct vision.

CLS filter - haziness gone, but still a brighter sky than with the other filters attached. Nebula easily seen with direct vision, but not quite as distinct as with the OIII or UHC.

SII filter - extremely darkened FOV. Some surrounding stars visible, but barely a hint of the nebula.

Ha filter - nothing visible

Hb filter - nothing visible

Planet IR Pro filter - didn't try

L Filter Type 2C - didn't try

MC Klarglass - is just a clear glass filter, so didn't bother trying

Not sure if any of this helps at all, but there are definite differences between Astronomik OIII, UHC and CLS filters. They do very similar things, particularly the UHC and CLS, but there are absolutely noticeable differences. As for the SII, Ha and Hb filters, these are entirely different beasts altogether.

Very interesting post 

I have a 2" Astronomik O-III filter and find it really effective even with my 4" scope, leaving many background stars visible to set the nebula I'm viewing in context.

Having tried lots of UHC and O-III filters (plus a few rather ineffective broadband ones !) I've found the Astronomik O-III a pretty good "single filter" solution in all my scopes.

I wonder if the spec has changed in between my O-III and yours being made ?

[Moonshane]

could the differences be that there are differences between visual and imaging filters? some of the ones Joves has are imaging filters; maybe they all are?

[Moonshane]

my own recommendation is for an Oiii. in fact I think it was my advice repeated above!

[John]

could the differences be that there are differences between visual and imaging filters? some of the ones Joves has are imaging filters; maybe they all are?

Good point Shane. Imaging filters tend to have less throughput than visual ones from looking at the specs.

[Joves]

Could be the case. I'm not for a second saying the OIII isn't a great all-round filter. I personally find the UHC to be the better option, if only one is going to be purchased. Hence, when deciding which 2" filter to add to the collection, I opted for the UHC. That being said, I will most certainly add the 2" OIII at some point.

As far as I'm aware, the difference between the CCD and visual filters is purely with regard to the IR block/pass, which the eye isn't sensitive to in pure visual anyhow. I might be wrong. I should definitely have noted that my advice should be taken with a grain of salt, as I am by no means a connoisseur when it comes to these things

[Moonshane]

e.g.  http://www.astronomik.com/en/photographic-filters/oiii-ccd-filter.html    and      

http://www.astronomik.com/en/visual-filters/oiii-filter-visuell.html

[John]

From those diagrams the max % throughput looks similar but the bandpass width of the CCD version looks a bit narrower and shifted slightly towards the shorter wavelengths.

It would need a "back to back" comparison to see the visual difference this makes I guess.

[Reeny]

I got the OIII by mistake ........

Adding the filter changes the image - but darkens it so much that most of the clarity is lost

I will need dark skies and more practice to make the OIII work properly.

I will get there eventually, but in hindsight the UHC might have been a more forgiving filter to start with.

When I said mistake I was probably being to harsh on the filter.

It's my skills which are lacking.

The filter itself was nearly £50.

The money would have been better spent on another eyepiece at the moment

This was my mistake.

The advice I had was good advice.

One day my observing technique will get then best out of the equipment.

[Joves]

Interesting. Until recently, I've been using the filters mainly with a Mallincam video camera, but have started using them visually. Hence the ccd versions.

[bingevader]

e.g.  http://www.astronomik.com/en/photographic-filters/oiii-ccd-filter.html    and      

http://www.astronomik.com/en/visual-filters/oiii-filter-visuell.html

There's much more detailed technical data for the CCD filter: 

95% transmission at 496nm (OIII)

95% transmission at 501nm (OIII)

full width at half maximum 12nm

transmission from 494nm to 506nm

Excuse my ignorance, but what does the grey line/area depict?

Cheers

[Joves]

Good question. And it beats me! I just like to look through the things!!

[bingevader]

Nevermind, got it. 

visual filters: The gray curve shows the relative sensitivity of the dark adapted human eye at night

photographic filters: The gray curve shows the relative sensitivity of a typical CCD sensor

Cheers

[Joves]

Ah, that's interesting. Obviously a CCD sensor is a lot more sensitive than the human eye, however, I've only really considered the spectrum that the eye sees vs. a CCD up until this point. Hence, I thought the only difference between a visual filter vs. a CCD filter was the infrared spectrum. I should probably pay more attention to the spectrum graphs and not just listen to the guys in the shop

[John]

I recently bought an H-Beta filter at what I thought was a good price but when I examined the data that came with it I realised that it was the imaging version which had lower overall transmission and a slightly different band pass width than a visual observer would need. I had stipulated that it was for visual use so I referred it back to the supplier who did not know that there was any difference !

To be fair to them, they have now changed the advertising blurb for the filter now to reflect that it's suitable for imaging only.

It does pay to do a bit of research before buying as even the visual ones are not the same specification from brand to brand.

[jetstream]

When I said mistake I was probably being to harsh on the filter.

It's my skills which are lacking.

The filter itself was nearly £50.

The money would have been better spent on another eyepiece at the moment

This was my mistake.

The advice I had was good advice.

One day my observing technique will get then best out of the equipment.

These filters work within a range of magnification for your telescope,in mine exceeding a certain mag will make the image worse.They both(mine) make M42,M57 etc more easily visible from my bright home sky,with the Veil neb visible in my 90mm frac & 19.6-19.8 sky and brighter to the south.Hopefully you have tried an eyepiece within the design spec of the filter as this makes a big difference and will really give you a nice view of those objects.Since buying an OIII,the Ultrablock isn't used very much eventhough it is a good filter, and in general viewing from a darker sky really helps everything,lots.I think down the road your going to love that filter!

[Reeny]

I can use the OIII with the lowest 50x magnification eyepiece

Anything higher, and the image is blurred, or lost within the brightness of the sky.

I saw the owl nebula for the first time tonight - the 200p dob is working well for it's money.

I banged the OIII filter in to try it.

The lights went out (as normal)

And a very faint, dimmly lit, sharp edged Owl nebula came into view.

It's getting better.