Filter advice

[OptiGone]

Hi been a forum lurker here for a while now so guess i should speak up at some point .

I have a SW 130p (with the EP's noted in my sig) and would like some advice as to which filters would benefit me.

Firstly the Moon is way to bright, to the point it can hurt my eyes ! So i need a Moon filter but what percentage of transmission is best for an all round filter ( i see lots of types for sale).

Secondly - Planets. Had some great view of mars during the winter months but again it was very bright and only basic detail was seen. From other peoples pictures at the same time using the same scope + a filter things seemed clearer and more detail shown.

Thirdly - DSO's . Again during the winter i got some very faint but enjoyable views of the Orion nebula on good nights. A light pollution filter could help here yes?

Not looking to spend alot on these so what would any of you recommend would be good for the cheap end of the market?

Matt

[nicnac]

Moon & Neutral Density Filters - Variable Polarizing Moon Filter

i find this one great for the moon

and a neodymium filter for LP, these two are the only ones i bother with at the minute

[LukeSkywatcher]

If you buy one of these, it does a great job of killing 2 birds with one stone. Its a really good afforable LPF and works really well as a moon filter too (well i think so anyway). But certainly its a really good LPF for getting rid of the orange sky glow most of us suffer. I have pointed it directly at an orange street light and the light from it was pure white and not a hint of orange glow in sight.

Light Pollution Reduction - Baader Neodymium Filter

As for filters to use on planets...........

A standard set of coloured filters is fine. Yellow works well on Saturn and Jupiter, Red on Mars etc. They are more effective for observing finer details on planets with larger apeture scopes but i also have a SW 130P and they do help a little.

[John]

For nebulae, narrowband (as they are known) filters such as UHC and OIII are the most effective. The OIII filters generally work better in mid-larger aperture scopes so I reckon a UHC would be worth considering for your scope. I had a Baader UHC-S filter for a while and that seemed quite effective in scopes down to 80mm aperture.

Filters are no substitute for dark skies though and I think you would be amazed what your scope would show if you can get it to a really dark sky site occasionally, especially for galaxies which filters don't help with.

[LukeSkywatcher]

John...........so its UHC filters for smaller apeture scope with regards to nebs and OIII for larger scopes?

Good to know. A neb filter will be my next purchase and i would hate to have got the wrong one.

Now............is there such a thing as a cheap UHC/NB filter for say about £30-40 purely for observing.

[Ogri]

Castell UHC Deepsky Filter for 1.25-Inch Eyepieces [Castell-Duhc1] - £35.25 : 365Astronomy: Discovery for every day! the 2" is just over £10 more.

It is definitely 'contrasty' and if I had known what I know now, would have got the Skywatcher LPF first (definitely added this UHC after though, it is very good from what I have seen of it so far - no great viewing opportunities as yet).

This from the Skywatcher blurb on the LPR filter:

"Bright, light-polluted skies appear darker, and the contrast between object and sky is improved significantly. This contrast-enhancement effect is particularly apparent on nebulae. Unlike stars, emission nebulae give off light in a very narrow range of wavelengths. The filter allow maximum transmission of the important wavelengths of H-alpha, H-beta and doubly ionized oxygen – the ones most commonly emitted by nebulae. "

Personally, apart from the nebula filtering, I am at least as interested in the contrast capability being milder than the UHC, so I will use the UHC for good to excellent viewing, and the LPR for everything (hopefully) else.

I could well need different rates of contrast either side of the LPR, and when I get a bigger 'scope, I'll get the added contrast that the OIII offers beyond the UHC.

Hope that made sense.

eta: not living in a particularly light polluted area, I had no idea how useful these filters were, even with no light pollution.

PS for polarising filters, these seem good value, especially as you can use just one, or, put one on the diagonal/adaptor, and the other on an eyepiece, and just rotate the eyepiece to get the density you require http://www.scopesnskies.com/prod/Scopeteknix/dual%20polarising/filters.html

[OptiGone]

This is great guys. Thanks for the replys.

That Castell UHC looks well priced going by the reviews.

[LukeSkywatcher]

Ogri this is about the 3rd time today that i have seen Castell filters mentioned across the web.

Its bang on budget for me.

Methinks i will bookmark this and purchase soon.

Thanks.

[Ogri]

I got the 2" Paul and the coatings and finish seems to be 'up there'.

My experience is with all sorts of exotic coatings on my eyeglasses over quite a few years now, but this is the first astronomy filter I have bought other than a Meade Moonfilter for dad which I used and found to be nowhere near what I needed for protecting my eyes (eta: this isn't to say that Moon Filters aren't perfectly adequate for people with normal eyes - mine simply can't contract the pupil to block out excess light).

So a 2nd opinion from someone other than myself would make sense, though with the important contrast side of things, I feel my findings are valid, and I do feel this filter is worth the money just for that contrast in good to excellent viewing conditions.

After all, other UHC filters might be far more efficient and worth the price difference, but as I have never seen or used them for myself, I can't really comment on the relative effectiveness or value.

[John]

John...........so its UHC filters for smaller apeture scope with regards to nebs and OIII for larger scopes?

Generally, yes although the specifications of various brands of UHC and OIII vary which alter their suitability for various apertures. The Baader UHC-S is a fairly "mild" filter which has a slightly wider band pass than some other UHC's but the Baader OIII filter is a bit more severe that some other OIII's making it best for use in larger apertures.

I have an Astronomik 2" OIII filter which is not as "harsh" as some OIII's so works well even with my 4" scopes while delivering substantial contrast enhancement to planetary nebulae in particular. The Astronomik OIII also seems to be made of better quality glass as star images remain pinpoint through it which is not what I've found with other filters.

Like many things in astronomy it's not quite as straightforward as you think at first glance

[brantuk]

If it was just for the moon you don't need a filter. Just put the end cap on the tube and remove the smaller offset end cap from within it. This will reduce the light enough to make comfortable viewing - you'll be surprised how good the viewing is with such a reduction of aperture

[LukeSkywatcher]

If it was just for the moon you don't need a filter. Just put the end cap on the tube and remove the smaller offset end cap from within it. This will reduce the light enough to make comfortable viewing - you'll be surprised how good the viewing is with such a reduction of aperture

This is VERY true. For 6 months after i bought my 90EQ i only observed with the central cap removed (i didnt know the whole lens cover could be removed).

OMG................when i discovered the whole lens cap could be removed and i observed the moon with it removed....................i was near blinded.

I think the smaller inner cap on my 90EQ stops the apeture down to about 50mm.

[crazyjedi]

the Castell UHC seems hot gossip right now cuz i'ts cheap and fits into a nice middle of the road band width reduction. I like the idea of the Baader UHC-S for this reason but the Castell is less than half the price of the Baader. Direct comparisons would be great.

Any one wanna do an independent review ??????

A good UHC is usually better than a proper OIII unless you have a decent sized scope.

[crazyjedi]

Ps a good moon filter is a blessing. If the moon is up, it's always the last thing i look at for the night - cuz it is so bright it leaves moon imprints upon my retina for hours afterwards

[LukeSkywatcher]

I'm LIKING the Castell. As you say its hot at the moment due to price/performance.

[LukeSkywatcher]

Ps a good moon filter is a blessing. If the moon is up, it's always the last thing i look at for the night - cuz it is so bright it leaves moon imprints upon my retina for hours afterwards

The bog standard Celestron Moon filter that i have deals with that beautifully.

As does my SW LPF.

[crazyjedi]

I have an LPF that isn't enough to reduce the moon to a comfortable bightness. Will get a moon filter ASAp tho as i still find it so fascinating. How much was the Celestron filter paul?

[LukeSkywatcher]

The Celestron filter came as part of the EP kit i have. So i cant really tell you a price for it alone.

[Ogri]

I've just ordered a 2" Skywatcher LPF from FLO, and once it's here, I'll try and do some side by side photo's with the Castell UHC to show up any difference in contrast.

If there's a noticeable difference between them, that might be a good insight into relative performance.

I'll try and get daytime blue sky, clouds, and a white paper backdrop type of comparison, and may be able to manage a photo through them as one of those orange streetlights comes on (it'll be with a Canon A480, so fingers crossed).

[LukeSkywatcher]

Jedi..................i just found this link showing the Celestron Moon filter i have: Cheaper then i thought. Does a damn fine job though.

http://www.opticsplanet.net/celestron-telescope-moon-filter.html

[crazyjedi]

chears Paul will have to pick one up as soon as funds become available

[crazyjedi]

chears Paul will have to pick one up as soon as funds become available

[Ogri]

Well doing comparisons turned out a bit tricky, due to the mirror effect with the UHC and angular effect of the coatings, tried holding them side by side, etc.

This is them side by side on a sheet of paper, clear skies, bright sunlight, which should illustrate the problem (click on thumbnails for bigger version):

Eventually hit on holding together and photographing them well clear of the piece of paper, and clipped areas from each filter that showed up the contrast best:

Castell UHC

Skywatcher LPF

Both had the paper in the background.

The differences seem representative of what I could see when looking through them side by side at the blue sky as a background, but I just couldn't photograph them well enough to get the effect (below is the best I could manage lol!):

eta: Update. Now used the Skywatcher LPR from sundown. Viewing improved slowly as the skyglow (dusk half light rather than light pollution) eased, and the filter worked nicely giving very good contrast, from 'light' contrast early on, to a very comfortable contrast as darkness improved. I tried it with a single polarising filter on the new moon, and the views were very good. No colour fringing spotted apart from a suggestion of a really slight and thin hint of yellow right on the edge of the moon, when out of focus (at 115 x mag). Not even a hint at 30 x mag or Barlow'd to 60 x mag.

I really do like this filter, and I think it looks to be a great partner to the UHC - when the LPR is running out of steam, time for the UHC, when the UHC is too heavy for the conditions, time for the LPR. Well chuffed basically.

Obviously those parameters will vary depending on the light gathering of particular 'scopes, and I can't comment on nebula performance as yet as the skyglow has been a bit too uncooperative so far round here (and I've had to knock off the viewing a bit too early to be in with a chance).

[LukeSkywatcher]

Interesting stuff Ogri. It seems the Castell UHC does indeed give a slightly darker contrast then the SW LPF.

[Ogri]

It's noticeably different in use Paul, I'm pleased to say.

I reckon the LPR will work well from bad to good viewing, and the UHC will work well from good to excellent. In the 120mm f5 Refractor, of course.

With a 'scope with much better light gathering, the LPR may be right say from bad to fair, then UHC fair to good, and OIII good to excellent (strictly for the contrast aspects).

For what I need for my eyes, I've definitely had a smashing result.