UHC-S filters - how much do they dim the view?

[osbourne one-nil]

I've just received my Baader UHC-S filter and having fathomed how to open the box (a feat of which I am very proud) I've had a quick look and, to me anyway, it seems that the filter must dim the view. 

Is this the case? It looks like it might be a while until I can try properly for myself judging by the snow and wind outside. 

[ronin]

All filters effectively dim the view, they all cut something out.

The UHC-S will pass 98% of 460 to 530, then basically nothing from 530 to about 630, then 95%+ from 630 to 680 then it's gone and your eyes stop seeing much beyond that.

So a lot of the incoming light is blocked the 530 to 630 bit and some below 450.

You get no violet, the blue and half the green then some of the red, half green is gone and no yellow or orange. Just used approximate ideas for wavelengths to colours.

The purpose is to pass Hb (480 blue), [OIII] doublet (495 green), Ha (656 red) and [sII] doublet (670 cyan) and stop the rest.

The idea is that although light is removed the removed bit causes the contrast to be greater and so the target stands out a bit more.

You could write an instruction guide to opening the box. :grin:

[osbourne one-nil]

Well I'm not sure I could because I can't open it again. I've reached that age - packaging is becoming a problem!

[John]

They do dim the background stars as part of the way they work but the payback is that the nebulosity stands out more. The UHC-S does this less than almost any other UHC type filter though as it's band pass width is more generous than other UHC's. It's designed that way to suit smaller aperture scopes. I have a soft spot for the UHC-S because it was the 1st filter that showed me the Veil Nebula though my ED100 and ST80 refractors. Without the filter the nebula was invisible with these scopes under my skies

[Reeny]

I remember when the view through my OIII went funny on the Orion nebula.

The clouds had come over and the filter was still working through the mist - just like an X-ray machine.

The nebula filters will take a bit of getting used to.

It's similar to someone turning the lights out.

[osbourne one-nil]

Thanks both - I've got it to show me those things I've never seen through my 8" dob and 4" frac...so once the skies clear and the Moon goes, I'll give it a go. Makes perfect sense what everyone says, so I'll stop worrying that it just looks like something from some sunglasses!

[damnut]

They can certainly help to provide just that extra bit of detail, but that would also depend on how many pints you had downed at the Tufton

[John]

I tend to use UHC and O-III filters only when they will make a really noticable difference to the appearance of the target object. As far as possible I prefer to view without a filter but there are some objects where the difference is really pronounced. Not that many though but the Veil Nebula justifies the price of the filter on it's own in my opinion.

[osbourne one-nil]

I've never seen the Horsehead, so I'm hoping it might work on that too (it's an emission nebula isn't it?)

..., but that would also depend on how many pints you had downed at the Tufton

Now there's some local knowledge! They've done it up and put all this wooden flooring down and stuff - not old-man enough for my tastes anymore, but I'll be there later as I've got to nip in to do the post so I might as well say hello to a pint of Corby Ale!

[John]

The Horsehead is a very, very, very tough target. Your skies might be darker than mine but I've yet to see it with the optimum filter which is an H-Beta and my 12" scope. It was seen (just) at the SGL star party a couple of years back with an H-Beta filter and a 16" scope.

I'm not saying you won't be able to see it with your 8" and the UHC-S under a really dark transparent sky but it would be a massive achievement if you did I reckon, simply massive.

Good luck !

The Horsehead Nebula is a dark nabula that projects across a very faint emission nebula.

[John]

PS: if you want to have a bash at the Horsehead, here is some useful information:

http://www.skyhound.com/observing/archives/jan/IC_434.html

[alan potts]

Being a total brand snob I have just tried for a Astronomik UHC on A B&S, in truth I could do with a cloud removal filter, now there is a way to make money if you could manufacture such a thing. March has been dire, two nights .

[John]

My Astronomik O-III was superb Alan. I'm sure the UHC will be similarly good. I've recently moved to using a Lumicon O-III and an Omega DGM NBP filter (a UHC type) and those seem excellent as well. The Lumicon H-Beta is my least used and appreciated filter but thats hardly it's fault

[alan potts]

I have a 2 inch Astronomik Olll which I got a while back now on the strength of what you said, it's great on the Veil and I am looking forward to trying the new scope on this target though it will never show all of it, maybe an 18 inch F 2 would be required.

I have a 1.25 inch Lumincon H Beta coming from German and should be here next week. I went for thr smaller size as I thought my 24mm Panoptic would be the eyepiece of choice and the 2 inch filter is 275 euros which is much more than in UK, TS have whopped the prices up of late and I think unjustly, a 21mm E is now 910 euros, I can see the queue from here.

[John]

I have a 1.25" H-Beta for the same reason. Not that I've seen much with it !

[scarp15]

Its getting too late in the season now for an attempt on the Horsehead and with the approaching full moon. Try your filter on M97 the Owl Nebula, should work a treat. 

[osbourne one-nil]

Thanks, will do and good link John! At least it's no fault of mine I've never spotted the horsehead...I need a bigger scope.

I did hear back from Mag1 Instruments yesterday and am sort of tempted by their 12.5" dobsonian because I know what fantastic scopes they are and just what a pleasure they are to use. But then for perhaps half the price I could get a 16" Skywatcher! Still, a truly top notch 12.5" instrument with a Zambutto mirror plus its portability does make it tempting. 

[scarp15]

Good comprehensive information regarding filter types on here.

Filter Performance Comparisons For Some Common Nebulae | The Prairie Astronomy Club

[alan potts]

Scrap15,

That is a really good piece of info I have bookmarked it, I am lucky being here that Orion is still high enough for at least two hours after dark with being further south, if I ever get another clear night

Alan

[scarp15]

Good luck Alan, if the weather clears and your H-beta filter arrives in time, your Sumerian 18"  will be worth an attempt on the Horsehead. Very difficult subject, becomes a bit easier when you have gained in familiarity and become accustomed to placement of a selective eyepiece into the location, that combined with time and patience. I am already looking forward to tackling it again next season.

[alan potts]

John,

Still on filters but a tad off original subject matter. You used to have an Astrononik Olll and now use a Lumicon Olll. Now I knowyou  have tried out Baaders and the like but said if I recall they take out too much and dim the background stars a great deal.

Do you prefer the Lumicon, it is something that I wanted to explore but the deal fell through due to me not having a Paypal account, sadly there was also a Lumicon UHC as well in the offer. I have landed the 2 inch Astronomik UHC BTW.

Alan