which filter?

[robbieboy]

Looking through my Turn Left At Orion book there are some nice deep sky objects to look at around this time of year. On some of the objects it recommends using at filter, so my question is what do you recommend? It says use one for M57 but i can see that clearly through my 18mm bst eyepiece. What do they actually do? or should i just put my money towards building up my eyepiece set? Cheers Rob.

[Moonshane]

the light we see comes as white light and includes all spectra although we can only see some of course. filters only allow through certain wavelengths and these help reduce light pollution or increase the darkness of the sky. if an object emits the wavelengths allowed then it becomes relatively brighter. it's not really becoming brighter, just that it is less 'drowned' out by the other wavelengths blocked by the filter.

I have several filters used as follows:

Baader neodymium - used as a lunar / planetary filter but some use for anti-light pollution

Castell Oiii filter - my most used narrowband / nebula filter. this allows some objects to be seen with smaller apertures which are not even visible in my 16" dob from home. I can see the Veil in my 6" scope and have also seen it in a 90mm refractor from home. from a darker site even a 6" scope gives great views.

Castell UHC filter - also very good and useful on many objects. it tends to enhance objects you can already see.

Skywatcher H-beta filter - restricted to a few nebulae (Horsehead etc) and for bigger apertures / dark sites. not even used this yet!

All of the above filters have their uses as different nebulae react differently to filtration. If I had to choose only one it would be Oiii for all apertures but others will differ in this view. my wish from a filter is that is should firstly show me things which are not visible without it and then secondly enhance things that I can see.

my order of purchase was

Baader Neodymium

Oiii

UHC

H-Beta

[Bart]

if i had to pick one it would be the UHC, more useful in terms of numbers of objects it enhances. Then probably OIII and then what I would consider the nice to haves. The Veil Nebula is a beauty and is really enhanced by the OIII, worth the purchase money alone

[John]

I find an O-III all I need. I prefer to view most nebulae unfiltered but there are a few objects where the O-III makes a heck of a difference and thats when it earns it's place in my eyepiece box

My O-III is the Astronomik in the 2" size and combined with the 31mm Nagler renders breathtaking views of the Veil Nebula complex.

[NGC 1502]

Looking through my Turn Left At Orion book there are some nice deep sky objects to look at around this time of year. On some of the objects it recommends using at filter, so my question is what do you recommend? It says use one for M57 but i can see that clearly through my 18mm bst eyepiece. What do they actually do? or should i just put my money towards building up my eyepiece set? Cheers Rob.

Great advice above. But if it were me, I'd get some nice eyepieces first, as they are used on all objects, then get a filter or two later, because they are only used on selected objects.

I have UHC and OIII. If I had to own only one, it would be the UHC, but opinions genuinely vary on that............

Regards, Ed.

[Qualia]

I'm not a big fan of filters but sometimes use a Baader UHC-S filter and have found it useful on occassion.

It works well on objects such M 57 or M 27 but it does cut out a decent bit of light except, of course, on that narrow band the nebulae emit. But, all this is with a 10". On the 4", it's a bit more of a case of 'touch-and-go' and often I prefer just to be without the UHC-S filter and simply do with as much light as possible. So, the general warning here is, don't expect magic. UHC filters will bring out the nebula but as a consequence will cut light from the gorgeous star field framing the nebula and obviously are completely redundent on objects such as galaxies.

Rightly or wrongly, I always figured that O-III and H-Beta were a tad more aggressive than our UHC-S counterpart, so I imagine they would darken the sky background even more. Here, then, I guess they would also be great filters but perhaps work best with decent aperture (+8"?) at a dark site.

As Moonshane suggests, the Baader neodymium is recommended by many folk here at SGL and I have read that along with Lunar work it can also be useful in planets. Again, on Jupiter, I have found a cheap light blue filter to sometimes be very effective, but find Saturn to never take well to any colour.

Personally, I agree with ED, at this stage it is probably better to be funding a new EP but with that said, there is one filter I'd strongly suggest you buy and as soon as possible: a Baader Solar Filter for white light sun viewing. They are cheap and with care and attention are easy to set up and you can enjoy observing and learning from the sun on any bright, sun-shining day.

[scarp15]

I only really use one filter, a Lumicon 2" OIII. For the objects that it does enhance, it does a thumping good job. For example last weekend I looked at M97, The Owl Nebula, a dim shadow without the filter. Add the filter and then pop it is there! The Veil is the show piece, which may be invisible without this filter and there are many other objects that benefit to.