Filters for use when viewing Nebula (advice needed)

[Paulhenry85]

I really struggle when viewing nebula as they appear really, really faint and barley distinguishable (expect M42, M43 due to shear size and brightness) this is due to heavy(ish) light pollution, I have seen there are a couple of filters that claim to reduce light pollution and or improve visuals of different types of nebulae. Do these filters work? And which one will (if they do work) work best for my scope (the standard 8" SW dob 1200/200)?

[Reeny]

I got the OIII Castell filter - but it takes a lot of getting used to.

The filter works by taking around 90% of the background light away.

So a faint object becomes even fainter.

The improvement comes from viewing nebula on a darker background.

UHC are weaker filters, and easier to use.

The UHC-S will be weaker again.

I suggest you try to borrow a filter to try, then decide what you might need.

If you need to take a guess, try the UHC first, then you can go up or down from there if you need to part exchange.

Apparently dark skies work much better than filters for nebulae.

You can drive a lot of miles into the countryside for the price of an OIII filter.

[swamp thing]

As a galaxy and nebula observer I put dark skies above everything else. Dark skies are quite simply THE key. They, above everything else control what you will or won't see.

After one has found a good dark site then we can look at filters to further enhance the views of nebulae. Galaxies are not helped by filters.

A good set of filters is a great asset to have when observing nebulae, but they still work best from dark skies.

You won't go far wrong with either the UHC or O-III filters.

[BillP]

O-III filters are very much more restrictive than UHC filters, so they present a much dimmer image.  Look at the transmission profiles of this UCH vs O-III to see.

O-III:  http://www.google.com/imgres?imgurl=http://www.astronomik.com/media/produktabbildungen/astronomik/transmission/full/astronomik_oiii_trans.png&imgrefurl=http://www.astronomik.com/en/visual-filters/oiii-filter-visuell.html&h=600&w=799&sz=68&tbnid=mORu6eVD5p700M:&tbnh=90&tbnw=120&zoom=1&usg=__aeQO0baCpfodI6EYydVQdlc7d98=&docid=O_C3NfbQevgB7M&sa=X&ei=LvqZUp6eNITnoATwh4LYDw&ved=0CE0Q9QEwAQ

UHC:  http://www.google.com/imgres?imgurl=http://www.astronomik.com/media/produktabbildungen/astronomik/transmission/full/astronomik_uhc_trans.png&imgrefurl=http://www.astronomik.com/en/visual-filters/uhc-filter.html&h=600&w=799&sz=70&tbnid=Itz0lJJn5gujJM:&tbnh=90&tbnw=120&zoom=1&usg=__vLxTkxYeIfENFCtiCB44Fsb2i-s=&docid=XRerVYhv6Y2WoM&sa=X&ei=0fmZUvi4FJLkoASp54DwCA&sqi=2&ved=0CFIQ9QEwAA

Not all UHCs are the same either, some allow in more lght than others; like the Meade UHC allows more spectrum in than the Astronomik as example.  From my moderately light polluted yard, I prefer the ones that let in a little more light and are less restrictive. 

A key to getting some better performace from them is to use eyepiece-telescope combinations that produce brighter exit pupils.  The show much better if your eyepiece-telescope combination is producing a bright exit pupil, like 5 to 7mm, so the nebula is bright enough to view well.  So this means lower magnifications work best with the filters generally.

Another key is choosing the right DSO to view with them as not all respond as well.  As already mentioned, galaxies generally do not respond well.  The list below is one I compiled from user reports of targets that responded *best* to filters like these:

M1—Crab Nebula

M8—Lagoon Nebula

M16—Eagle or Ghost Nebula

M17—Swan Nebula

M20—Tri fi d Nebula

M42—Orion nebula

M57—Ring Nebula

M76—Butter fl y Nebula

M97—Owl Nebula

NGC281—Pacman Nebula

NGC896—Heart Nebula

NGC1514—Crystal Ball nebula

NGC 2070—Tarantula Nebula

NGC2174—Monkey Head Nebula

NGC2237—Rosette Nebula

NGC2264—Cone Nebula

NGC2359—Thor’s Helmet Nebula

NGC2371/2372—Gemini Nebula

NGC2392—Eskimo Nebula

NGC2440—Bow Tie Nebula

NGC3242—Ghost of Jupiter Nebula

NGC6210—Turtle Nebula

NGC6445—Box Nebula

NGC6543—Cat’s Eye Nebula

NGC6781—Big Ring Nebula

NGC6888—Crescent Nebula

NGC6905—Blue Flash Nebula

NGC6960−6995—Veil Nebula

NGC7008—Fetus Nebula

NGC7009—Saturn Nebula

NGC7293—Helical Nebula

NGC7635—Bubble Nebula

NGC7000—North American Nebula

IC1848—Soul Nebula

IC5067−5070—Pelican Nebula

[scarp15]

As above, preferably dark skies (which includes little or no moon light) and wait until the intended target is close to, or at its highest point. After which the list above and applicable filter will either be required or additionally enhance.

[Paulhenry85]

I agree nothing beats a dark sky,

I've always been happy with the views from my dark skies spot of galaxies and nebulae but was hoping to improve views from the back garden if these filters don't work under light polluted skies I'm more inclined to take reenys advise and drive out for the cost (only problem is weather prediction and time it take to get there, setup ect)

[John]

I don't use my Astronomik O-III filter all that much as I prefer viewing objects without a filter where possible. There are some objects though where the filter makes a really large difference, in some cases enabling something to be seen where nothing is otherwise visible. One of these objects is the Veil Nebula which, with the O-III filter, goes from barely detectable to a vast and beautifully structured group of objects which, in my opinion, are one of the finest sights in astronomy. This one object is worth the price of the filter alone to me 

My skies from my garden do have light pollution to contend with but the filter delivers in all my scopes from 4" to 12" in aperture despite this.

[Reeny]

We had the first view of Orion last night.

It made the cost of the OIII worth it for this view alone.

The clouds rolled in, and the filter allowed the nebula light to come through the mist as a clear image (filtering out the backlit clouds)

It as like having an X-ray telescope.

When the clouds dissappeared, the OIII worked it's magic again.

Darkening the background, and sharpening the edges to give a nice clear outline.

I am very happy now with all the gear recommended on this forum. 

If the OIII is that good on a bright Nebula - we definitely need to find a dark site for Ring, Dumbell, Owl etc

[Pig]

I have the 1.25 Lumicon O-III and I find the views vary quite considerably dependent on the seeing.

I have not tried it on the Veil but I will give it a shot during my next session.

[rgm]

I started with an UHC and then purchased an O-III.   I observe under dark skies and find both great.  As already mentioned, the target object dictates the best filter.

[allen g]

I find the UHC and OIII necessary to have - with dark skies on certain nebula it makes a big difference. This august I viewed the veil for the first time with my Lumicon OIII in my NP-101 (4"fract) with a 31 nagler and it was like a picture in a book. The entire nebula was seen as this set up gave approx 4* field.