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UHC Filter any good?

steve_bham

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Moonshane

Moonshane

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Posted

I though just what you did - I don't know about these things really but assumed that a wider banding means more wavelengths and light through the filter therefore a slightly brighter throughput? I suppose it's just whether the coatings are as well applied and durable plus whether the glass is a good grade/flat etc?

for the price, they might be worth a punt. maybe we should buy one each and then compare notes:D

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  • 1 month later...
Ogri

Ogri

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Posted

I got the 2" Castell UHC Steve, and it was an eye opener for me, even though viewing conditions haven't allowed it to exactly 'fire on all cyliners' yet.

Simply from the contrast aspect.

The 'scope I'm using it in is a Skywatcher ST120.

Quality of glass and coatings seems to be 'up there', and a simple hand held test showed it performing well when held up to a streetlight. The orange glow just disappeared leaving the tiny dull red glow of the the bulb itself.

I have rubbish eyes (Glaucoma, Astigmatism, etc) which have been compounded by a laser eye operation going wrong, and welding up the eye internals while the pupil was dilated for the operation.

Because both eyes are linked, this means neither eye will now shut down to control light input (to the extent I get arc eye if I look at the moon even with a Meade Moon Filter fitted).

With low magnification in the ST120 (32mm gives 18.75 x mag, 20mm gives 30 x mag), and 'eyes wide open', I get star swamped {eta: maybe this is a wrong description of what I am getting, if you look at the 'fuzz' in this image http://whwastro.homestead.com/files/temp/M66_Lum_28x300s_no_filter_histo.jpg I get that but much more severely - original filter discussion here http://www.cloudynights.com/ubbthreads/showflat.php/Cat/1,2,3,4,5,8/Number/3781381/Main/3781381}. There's so many stars in the field of view, it's a real struggle picking anything out. A bit of a pain if you are doing Rich Field to avoid all the bright suff, as you may imagine.

Which is where the importance of contrast comes in, perhaps particularly for me, but illustrative of a potential problem for everybody?

The contrast with this UHC filter, is superb. Even though it has been too hazy for me to be able to see any nebulosity anyway, the intensity of the UHC contrast pushes the vast surplus of background stars out of view and allows me to see some perspective of the scene.

To be fair to the filter, in unsuitable viewing, this is definitely over the top, but in those circumstances I wouldn't be using the UHC anyway.

But I intend to use similar but milder versions of it now. My next purchase will be a Light Pollution filter, which will give a much milder contrast than the UHC, and should be much more suitable for use in more demanding viewing conditions.

If that proves to be not quite enough contrast for many circumstances, and the UHC is still a bit too contrast heavy, then I'll add a Baader Contrast Booster, which is in between the two (many thanks for the insights robhal9000).

If the LPF is still a bit contrast heavy for many circumstances, then I'll bite the bullet and add a much milder semi APO filter at some point.

As you can see, I'm doing it the cheapest route first. *grins*

From what I have seen so far, in good to excellent viewing conditions, the UHC definitely will have a very worthwhile place, as down here we normally get a pretty high percentage of such nights. It should function to a similar degree with otherwise similar viewing conditions, but with the addition of light pollution as well, if its impressive performance directly in front of a streetlight is anything to go by.

It might be fair to say that in a much larger 'scope than my ST120 (say a 200mm and bigger Dob?), the UHC might perform pretty much how a LPF will perform in mine?

Getting that UHC has been such an insight into the importance of contrast, that I now wish I had bought a LPF at the time I ordered the 'scope. Due to not suffering particularly from light pollution, I simply didn't think of it. It's really sealed my certainty that I can now tame the light gathering of a larger 'scope, without damaging my eyes (especially with the addition of variable polarising filters as well).

When I get that bigger 'scope, there may even be a place for an OIII filter to use in it as well.

All but the pair of polarising filters, will be 2", to use in front of the diagonal, and as all the 'really bright stuff' I will be viewing with 1.25" eyepieces, I put one polarising filter in the end of the 1.25" to 2" adaptor, and the other onto the eyepiece, and just rotate it to get the light blocking that I need.

Not a great insight due to not having had good viewing conditions to use the filter with yet, but hopefully that's an insight to its potential as well as other benefits due to its contrast capabilities. Obviously I don't know how well this Castell compares to other UHC filters either, as this is my first one.

I'm certainly glad I bought it though, it seems fair value for money, but there is the additional caveat that due to the state of my eyes, I may get a heck of a lot more out of such a filter, than just about anybody else.

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Ogri

Ogri

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I must admit, I'd be really interested in finding out how the Skywatcher LPF compares for contrast with the Baader Neodymium LPF?

Anyone had a chance to compare them?

If the contrast is noticeably different, it may pay me to get both.

eta: *laughs* googled it, and came up with a comparison http://stargazerslounge.com/equipment-reviews/71126-skywatcher-lpr-filter-vs-baader-neodymium-filter.html ant's comparison shows them close enough not to worry I think. :D

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riklaunim

riklaunim

Posted
Posted

BTW did anyone used Castell O-III filter. It looks like O-III + H-beta filter - very narrow UHC. It be handy for some monochrome (planetary) nebula imaging I guess, where primary O-III emission gets some hydrogen addons from H-beta.

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  • 3 weeks later...
Moonshane

Moonshane

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hi Rik et al

Thanks for the info on the other thread by the way. I got paid finally for a couple of insect photos and decided to save the money like a good chap.

NOT!! I bit the bullet and order a 2" Castell Oiii today. I have confirmed with Zoltan (how cool is it that you can order stuff from a guy called Zoltan) at 365 Astronomy that the manufacturer has cleaned filters with Acetone and therefore my usual method of cleaning anything (with Isopropyl Alcohol and cotton balls) will be fine - so in other words you can clean them. He was really helpful, replying to an email query, asking a question of the manufacturer and then confirming this, all on the same day. He also confirmed it has been posted the same day and is on the way to me. Great service so far!

Looking forward to using it next week and will report back - hopefully after seeing the Veil through the dob. I was going to wait and save for an Astronomik or Lumicon but given the Castell was £48 delivered for a 2" Oiii filter I thought why not. Even if it's not the best, if it allows me to see things I'd have no chance of seeing otherwise then it's got to be worth it - I'd probably miss the Veil and others this year otherwise so we'll soon see if I was right.

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LukeSkywatcher

LukeSkywatcher

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Posted

The Castell UHC filter has been mentioned/discussed here recently. I cant remember who, but one member did buy one and compared it to another brand UHC filter and posted images of the contrast etc.

The general feeling on it was GOOD.

If you google UHC filters you will be amazed at how many times you see the Castell mentioned. For its price it seems to really deliver. I plan on buying one in the near future.

*edit* It was Ogri who bought it.

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Moonshane

Moonshane

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hi Paul

I agree it sounds like for the money the Castells are really good! I'll confirm in due course.

re fitting filters, if you buy 2" ones then you can add then to the 2"-1.25" adapter (if you have a 2" focuser of course - although I don't think your scope does?) and then you don't have to keep changing the filter over to different eyepieces, you just leave the filter in. that said, I have sometimes forgotten about the filter and then wondered why my scope was not performing!! obviously at the point, it's time to go to bed! I think the UHC and Oiii filters can be useful sometimes for splitting tight doubles where the primary is much the brighter of the two. the colours might be weird but if it allows you to split them where you could not previously then not a major issue!

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LukeSkywatcher

LukeSkywatcher

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Shane...yes converting 2" EPs/filters to 1.25" is not a problem if you have the proper adapter and your scope has a 2" focuser.

If your scope has a 2" focuser.........with the adapter you can convert it to 1.25". 1.25" however can not be converted to 2".

and then you don't have to keep changing the filter over to different eyepieces, you just leave the filter in.

The only way i know of having the same filter on ANY EP that you use is by using a filter tray (the filter sits below the EP without screwing into it). Other then that you have to unscrew the filter and screw it into every EP you use.

This is a real pain and i am thinking about ways to construct a filter tray that sits below my focuser on the Heritage so that i dont need to keep taking filters off of my EPs and putting them on others.

Anyone with the know how are more them welcome to englighten me.

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Moonshane

Moonshane

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Posted
Shane...yes converting 2" EPs/filters to 1.25" is not a problem if you have the proper adapter and your scope has a 2" focuser.

If your scope has a 2" focuser.........with the adapter you can convert it to 1.25". 1.25" however can not be converted to 2".

and then you don't have to keep changing the filter over to different eyepieces, you just leave the filter in.

The only way i know of having the same filter on ANY EP that you use is by using a filter tray (the filter sits below the EP without screwing into it). Other then that you have to unscrew the filter and screw it into every EP you use.

quite right Paul - I realise about the one way adapter of course - I was making this point generally for others that might not appreciate this benefit of 2" filters. :p

if using a diagonal then you can put a filter in the end you insert into the focuser with the same effect. :D

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LukeSkywatcher

LukeSkywatcher

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Posted
quite right Paul - I realise about the one way adapter of course - I was making this point generally for others that might not appreciate this benefit of 2" filters. :p

if using a diagonal then you can put a filter in the end you insert into the focuser with the same effect. :D

Oh, if your star diag has threads on it then that is fine. I just had a look at the star diag on my 90EQ and there are no threads on the end that go into the scope.

I must check my Heritage if i can screw filters in on the opposite end of the focuser to where i insert the EP's.

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Moonshane

Moonshane

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bummer! you might find a nosepiece on Astroboot that might do? I think I saw one once.

I don't think this is 'usually' possible BUT you never know. could you buy a cheapo filter and knock out the glass. you could then glue the ring inside the focuser tube end? might work but would be a but fiddly to fit the filters I suppose.

I wonder if this is threaded or could be adapted in a similar way? - scroll down to the 30mm extension.

from Ian King Imaging

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Moonshane

Moonshane

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hi Paul

this is not an imaging part it just fits into the end of the focuser where an eyepiece would go. I thought it might be a solution to the filter 'problem' - not really a problem but might make it a bit less fiddly.

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