Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

O-iii filter or UHC

accessories Celestron eyepieces LP reflector dso
  • Please log in to reply
75 replies to this topic

#26 TheFacelessMen

TheFacelessMen

    Viking 1

  • -----
  • Posts: 511
  • Joined: 15 Sep 2014
  • Loc: Canberra, ACT

Posted 21 October 2018 - 02:06 AM

The links already provided are a good general guide to using filters.

 

In terms of my favourites to use the DGM NPB is excellent and the Astronomik UHS (not UHC-E) is also excellent.

 

I have used a couple of cheaper alternatives as well as Baader variants without the same level of performance.

 

The Astronomic OIII is very good too but is a lot more specific to Targets, while the NPB and UHC are applicable to broader targets.



#27 penguinx64

penguinx64

    Soyuz

  • *****
  • Posts: 3898
  • Joined: 12 Nov 2013
  • Loc: Manama, Bahrain

Posted 21 October 2018 - 03:40 AM

I couldn't see squat with O-III filters.

BeatingADeadHorse.gif



#28 Simon B

Simon B

    Viking 1

  • *****
  • Posts: 941
  • Joined: 16 Jan 2017
  • Loc: Vancouver, BC

Posted 21 October 2018 - 08:06 AM

The bandwidth is likely a far bigger factor than transmission.  Think of it in terms of signal to noise ratio.  Wider bandwidth means a lot more noise.  While scotopic response does decline some to the edges of these bandwidths, 48/28 means roughly 70% more noise in the denominator.  On the signal side, 95% transmission for key bands would be awesome, 90% is good and even 85 or 80 are preferable to very wide bandwidths.  Even 95 vs. 80 is less than a 20% boost in signal, so substantial difference in bandwidth is the bigger factor when considering trade offs.
 
FWIW my 22+ year old Orion Ultrablock has held up very well.

 
 
Oh ofcourse, I don't doubt that bandwidth is more important than transmission, but... Orion's filters come with spectral graphs that do not match the true performance of the filter at all. There have been examples of Ultrablocks that only pass 50% at H-beta.
 
Many of them only pass 70~85% at H-beta/O-III.... 85% is okay, but 70%? Hmmm
 
I actually own an Ultrablock - it's been tested, and passes 92-98% at H-beta/O-III, with a bandwidth of 28.4nm. Here's mine:

 

 

Orion Ultrablock
 
 
 
But some are not so good. So it's a gamble.. For $20 more, you can get an Astronomik/Televue/Lumicon, which consistently perform at 90+% with 21nm width.
 
 
Here are 3 Optolong tests (I've seen more, they are all more or less the same):
 
 
Optolong UHC (1.25)
 
 
Optolong UHC (2-1)
 
 
Optolong UHC (2-2)
 
 
 

They all performed exactly as they should - they're advertised as having a 48nm width, so you know what you're getting before you buy. No fake graphs, no nonsense, just a cheap, wide UHC


Edited by Simon B, 21 October 2018 - 08:27 AM.


#29 sickfish

sickfish

    Fly Me to the Moon

  • *****
  • Posts: 6731
  • Joined: 13 Jan 2009
  • Loc: Watertown Ma.

Posted 21 October 2018 - 08:19 AM

My TV cost $220



#30 Spartinix

Spartinix

    Mariner 2

  • *****
  • Posts: 268
  • Joined: 25 Apr 2017
  • Loc: Crete, Greece

Posted 21 October 2018 - 11:32 AM

...............

 

In terms of my favourites to use the DGM NPB is excellent and the Astronomik UHS (not UHC-E) is also excellent.

..................

What's a UHS? Confusing with CLS ccd filter? UHC-E is generally recommended for smaller telescopes, no?



#31 Miranda2525

Miranda2525

    Surveyor 1

  • *****
  • Posts: 1583
  • Joined: 12 Jul 2016

Posted 21 October 2018 - 01:54 PM

Side note:

 

Celestron/Baader UHC are very wide (~60nm) and more expensive than the Optolongs, so I wouldn't. DGM NPB is okay but some examples clip H-Beta line, people love these but on paper they're not quite as good as Astronomik/Televue/Lumicon.

 

I own the DGM NPB. I've used it on these things below with surprisingly great results: 

 

NGC 7293 (helix nebula) (OIII is the filter of choice for this, but the NPB showed it really bright)

M 27 (dumbell nebula) (Outer extensions showed up as well as the apple core)

The Veil / both sides (OIII is the filter of choice for this, but the NPB showed it really bright. Less knots, etc, but v.good)

NGC 6888 (crescent nebula) 

M 42 (best filter for this IMO)

NGC 281 (pac man nebula)

M 17 (OIII better on this object, but the NPB was not far behind)



#32 Redbetter

Redbetter

    Fly Me to the Moon

  • *****
  • Posts: 7333
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 21 October 2018 - 04:11 PM

Oh ofcourse, I don't doubt that bandwidth is more important than transmission, but... Orion's filters come with spectral graphs that do not match the true performance of the filter at all. There have been examples of Ultrablocks that only pass 50% at H-beta.
 

 

I have heard people say that, just haven't seen it.  The old Shimadzu strip charts were real from what I can tell, and in my case seem to match the performance of the filter.  The cut off on mine is around 75% at the H-beta line, but there is some blue shift on average because of the light cone, effectively making the transmission in H-beta higher.  Mine is narrower than yours at about 26nm.  A 1 nm shift on the steep slope is about the difference in 75 vs. 50 based on what my strip chart shows.    So even a 50% H-beta would effectively be running around 75% from what I recall of earlier discussions on the shift, and with the O-III transmission much better than that.   



#33 Simon B

Simon B

    Viking 1

  • *****
  • Posts: 941
  • Joined: 16 Jan 2017
  • Loc: Vancouver, BC

Posted 21 October 2018 - 10:13 PM

I have heard people say that, just haven't seen it.  The old Shimadzu strip charts were real from what I can tell, and in my case seem to match the performance of the filter.  The cut off on mine is around 75% at the H-beta line, but there is some blue shift on average because of the light cone, effectively making the transmission in H-beta higher.  Mine is narrower than yours at about 26nm.  A 1 nm shift on the steep slope is about the difference in 75 vs. 50 based on what my strip chart shows.    So even a 50% H-beta would effectively be running around 75% from what I recall of earlier discussions on the shift, and with the O-III transmission much better than that.   

 

Some of their O-IIIs have shown cutoffs at the 501 line. I saw one that was 70%, and another, that was 24%! So if blueshifting is taken into account then those would perform even worse. The blueshifting might improve the performance of those filters that came out of production that just so happen to be redshifted from 'ideal', but what about all those others that aren't. Seeing all this variation in quality, I can't see myself recommending these to anyone when a better filter is only $20 more.

 

Well, $20 more for the 1.25" filter. A 2" Ultrablock is only $100, which is significantly cheaper than an Astronomik/Televue/Lumicon 2" ($200-220), but still, it's a gamble.

 

The filter graphs do not match independent testing - so either Orions spectrophotometer or method of scanning is faulty, or it's the independent tester. But there have been multiple independent testers.

 

I just wish Orion improved their quality control a bit more, i.e. threw out the filters that had, lets say, below 80% trans, and got rid of the false filter graphs


  • Miranda2525 likes this

#34 Redbetter

Redbetter

    Fly Me to the Moon

  • *****
  • Posts: 7333
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 21 October 2018 - 11:07 PM

Haven't seen that anywhere.  Must have missed the threads.  What I have seen matched my results.



#35 Orion1802

Orion1802

    Explorer 1

  • -----
  • topic starter
  • Posts: 56
  • Joined: 10 Sep 2018

Posted 21 October 2018 - 11:42 PM

Hmm. Well too much recommendations for UHC. So I think lunicon or optolong, that's it. One last question, what is the advantage of 2" filter if my eyepiece are 1.25"?

#36 otocycle

otocycle

    Apollo

  • *****
  • Posts: 1159
  • Joined: 08 Jun 2005

Posted 22 October 2018 - 01:40 AM

Hmm. Well too much recommendations for UHC. So I think lunicon or optolong, that's it. One last question, what is the advantage of 2" filter if my eyepiece are 1.25"?

 

If you use a 2" diagonal or extension tube that is threaded for filters with your refractor, the 2" filter will screw on easily and be usable with any eyepiece in the diagonal or extension.



#37 6opuc9

6opuc9

    Vostok 1

  • *****
  • Posts: 101
  • Joined: 21 Jun 2017
  • Loc: Seattle area, WA State

Posted 22 October 2018 - 01:28 PM

Hmm. Well too much recommendations for UHC. So I think lunicon or optolong, that's it. One last question, what is the advantage of 2" filter if my eyepiece are 1.25"?

 

 

If you use a 2" diagonal or extension tube that is threaded for filters with your refractor, the 2" filter will screw on easily and be usable with any eyepiece in the diagonal or extension.

 

The big advantage is screwing the 2" filter into the nosepiece of the 2" diagonal and leaving it there so that you can switch eyepieces (2" as well as 1.25" with adapter) without having to re-thread the filter on and off every eyepiece each time. Since I use 2" diagonals in all my scopes (refractors and SCT) it works well

 

OP mentioned that their telescope is a newtonian though, so there is no diagonal. Can any reflector users advise if a 2" filter is a good idea for a newtonian to be used with 1.25" eyepieces?



#38 Spartinix

Spartinix

    Mariner 2

  • *****
  • Posts: 268
  • Joined: 25 Apr 2017
  • Loc: Crete, Greece

Posted 22 October 2018 - 02:11 PM

Well if there's about 25mm of extra in-travel, a filter wheel or slide could be used, but if not, a 1.25" filter seems obvious. If a coma corrector with 2" filterthread is used, any filter can stay there while switching ep's also.


Edited by Spartinix, 22 October 2018 - 02:13 PM.


#39 Redbetter

Redbetter

    Fly Me to the Moon

  • *****
  • Posts: 7333
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 22 October 2018 - 02:19 PM

For Dobs I don't use 2" filters with 1.25".  Others seem to be satisfied doing it though.  Half of my six 2" to 1.25" adapters aren't threaded for it (one is specific to the 20" scope's low profile focuser), and there is potential for some eyepiece barrels (and certainly my Barlow) to make contact with the filter in the other three.  The bottoms of the T6 and T5 barrels are flush with the bottom of the adapter and that is uncomfortably close to the filter glass when threaded in.  The Nagler zoom is longer and would make contact.

 

I never cared for putting filters on the 2" diagonals of SCT's or refractors.   It is cludgier than an eyepiece swap and re-securing the diagonal so that it doesn't rotate always seems to take an extra tweak or two after removing it.  Similarly I am reluctant to change diagonals in the field, although I sometimes do for specific things, mostly with refractors and the Mak in the backyard. 



#40 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • Posts: 41085
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 22 October 2018 - 04:38 PM

Hi
I own a 5 inch reflector. I am planning to buy a deep sky filter. Should I buy the UHC or O-iii. I own a small scope so I am afraid that oiii would darken the view.
Any suggestions?
Clear skies

Bear in mind, you will use these filters at low power (say, 10x/inch or lower).  The eyepieces you use will determine whether to buy a 1.25" or 2" size.

 

Picture a gray square against a gray background.  Hard to see.

Picture the same gray square against a black background.  Easy to see.

That's how these filters work.

 

so long as the wavelengths emitted by the nebula are passed by the filter, the narrower the bandwidth, the blacker that background is.

Yes, the filters will dim the overall image of the entire field, but they won't dim the nebula.  And it is the nebula you are seeking to see better, right?

 

So, the difference between those two filters is that the O-III filter passes the O-III wavelengths at 496nm and 501nm only, while the UHC filter passes

the O-III wavelengths AND the 486nm H-ß line.  All nebulae emit H-α light in the deep red (a wavelength to which out eyes are very insensitive) and H-ß in the blue

(where our dark adapted eyes are very sensitive).

 

If you buy just one filter, I'd make it a "universal" nebula filter and get a UHC-type (narrowband) filter of 21nm to 28nm bandwidth that passes all 3 wavelengths at over 90%.

Some examples (not a complete list): TeleVue BandMate II Nebustar, Lumicon UHC, Astronomik UHC Visual, DGM NPB.

 

If your pocketbook is small and you cannot afford the above, there are many UHC-type filters of 36-49nm bandwidth.  The background will be less dark, so the contrast will be less,

and if being used in a light-polluted area, these may not be ideal, but they are certainly better than no filter at all.

Some examples (not a complete list): Astronomik UHC-E, DGM VHT, Explore Scientific UHC, Optolong UHC, Starguy UHC.

Ultimately, with a scope of your size, you will want a narrower filter.  I'd call these "mediumband" filters instead of "narrowband".

 

A few things to keep in mind:

--use them for nebulae only (bright nebulae, planetary nebulae, supernova remnants, Wolf-Rayet excitation nebulae, but NOT dark nebulae, reflection nebulae, star clusters, or galaxies)

--use at low power

--be completely dark adapted before using

--remember, the overall field, including stars, will be darker, but the nebula won't be.  It is the contrast increase that makes the nebula appear brighter and easier to see.


Edited by Starman1, 22 October 2018 - 05:31 PM.

  • Solovino, BluesNebula and Maurolico like this

#41 David Knisely

David Knisely

    Hubble

  • *****
  • Posts: 16947
  • Joined: 19 Apr 2004
  • Loc: southeastern Nebraska

Posted 23 October 2018 - 04:36 AM

I should go with the narrowband "UHC" first, for the reasons stated above. Overall, narrowband "UHC" filters are less effective on planetary nebulae because in these objects, for their nature of being "growing shells" ionized by the hottest central stars, there are more shocks events due to variation in speed of ejected gases than in HII regions; these shocks make up ionization states with high electron temperatures that, in turn, raises the intensities of the OIII lines at 495.9 and 500.7 nm with respect to the recombination of the Hbeta line at 486.1 nm typical of the "slow" and colder HII regions. So you do not want this "unuseful" and indifferentiated Hbeta light interfering slighty as bright background upon the whole planetary nebula smearing details; hence OIII filters lacks of this line (and the Ha too).

 

Leaving out the H-Beta line coverage by using a narrower passband width centered on the OIII lines can often improve the contrast mostly by eliminating or reducing any faint continuum light between the OIII and H-Beta lines as well as cutting out unneeded continuum light in the "wings" of a wider filter's passband.   If you want to see planetary nebulae which are actually helped somewhat by the presence of the H-Beta line, try NGC 40 or Campbell's Hydrogen Star to name a couple.  Indeed, some use the H-Beta line filter on those two planetaries, although generally, I like a regular narrow-band nebula filter like the Lumicon UHC or DGM NPB on those objects.  Clear skies to you.   


  • Procyon and Maurolico like this

#42 Orion1802

Orion1802

    Explorer 1

  • -----
  • topic starter
  • Posts: 56
  • Joined: 10 Sep 2018

Posted 23 October 2018 - 09:12 AM

Lumicon on my list then.
Thanks all of you for your help.
Clear Skies
Aaditya

#43 GeneT

GeneT

    Ely Kid

  • *****
  • Posts: 15401
  • Joined: 07 Nov 2008
  • Loc: South Texas

Posted 23 October 2018 - 07:22 PM

Although much more specific in application, and although I don't use any filter all that often, the O III is a must have for me as is the H-Beta, although again rarely used. When I need these filters, I really need them. 



#44 David Knisely

David Knisely

    Hubble

  • *****
  • Posts: 16947
  • Joined: 19 Apr 2004
  • Loc: southeastern Nebraska

Posted 24 October 2018 - 02:23 AM

I couldn't see squat with O-III filters.

BeatingADeadHorse.gif

 

There are a number of reasons why you might be having trouble with the OIII filters.

 

First, you have to be FULLY DARK ADAPTED (20 to 30 minutes in total darkness) before using the filters.

Second, you need to take steps to stay that way (shielding against all local lighting (observing hoods or eye patches) and observing at as dark a location as you have access to).

Third, you need to use the proper magnification range (between 3.5x per inch of aperture to around 10x per inch, with the best performance in the lower half of this range).

Fourth, you need to use them on the proper emission or planetary nebulae, as not all nebulae will be helped with the OIII over the broader narrowband nebula filters like the Lumicon UHC (see the following article:  https://www.prairiea...ommon-nebulae/)

Fifth, you need to make full use of averted vision when viewing faint nebulae.

Sixth, you need to have a good OIII filter (Lumicon, Thousand Oaks, and Astronomik are three that come to mind. 

 

Good luck and clear skies to you.


Edited by David Knisely, 24 October 2018 - 05:13 PM.

  • Miranda2525, Maurolico and 6opuc9 like this

#45 David Knisely

David Knisely

    Hubble

  • *****
  • Posts: 16947
  • Joined: 19 Apr 2004
  • Loc: southeastern Nebraska

Posted 24 October 2018 - 02:30 AM

This is a *very* rough approximation as to what the various filters might do when compared to each other (and it is not 100% accurate, as the choice of filter varies from object to object, as well as on the observing conditions).   Generally, the narrow-band "UHC-like" filters will show emission nebulae with slightly higher brightness as well as showing a larger area of nebulosity than the narrower filters.  However, the OIII will sometimes provide superior contrast and dark detail even though the object may not appear as bright or as extensive as in the narrow-band nebula filters.  The OIII will also dim the stars more than the narrow-band filters tend to do, which can be helpful sometimes with finding small planetary nebulae in rich star fields.  Clear skies to you.

 

Attached Thumbnails

  • FilterCompNGC281Small.jpg

  • Jon Isaacs, Procyon, bmurphy495 and 2 others like this

#46 Redbetter

Redbetter

    Fly Me to the Moon

  • *****
  • Posts: 7333
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 24 October 2018 - 03:21 AM

Adding to David's list of O-III filters, the new TeleVue Bandmates are quite good as well.  Televue says they worked with Astronomik on these filters and the transmission is higher than the 2017 vintage Astronomik O-III while retaining comparable bandwidth from Don's scans.  Mine has performed extremely well in the field. 


  • rowdy388 and Maurolico like this

#47 WyattDavis

WyattDavis

    Viking 1

  • *****
  • Posts: 925
  • Joined: 25 Dec 2013
  • Loc: Rye, NH

Posted 24 October 2018 - 05:03 AM

David, thanks for post #45:  that does a nice job of conveying the basic differences. UHC seems like an easy starting point in a lot of cases. I use the Prairie Astronomy Club filter comparison as a standard reference. Thanks for doing that!


  • 6opuc9 likes this

#48 Maurolico

Maurolico

    Ranger 4

  • -----
  • Posts: 323
  • Joined: 13 Jan 2017

Posted 24 October 2018 - 06:56 AM

Adding to David's list of O-III filters, the new TeleVue Bandmates are quite good as well.  Televue says they worked with Astronomik on these filters and the transmission is higher than the 2017 vintage Astronomik O-III while retaining comparable bandwidth from Don's scans.  Mine has performed extremely well in the field. 

The problem with TV filter as well as Lumicon in EU is that they are pricey with respect to Astronomik. They are 100 bucks more expensive (Lumicon 60 bucks). The spread between the three is way lesser in US as far I call tell. Food for thought whether the OP lives in EU. Not a complaint, just info.



#49 Maurolico

Maurolico

    Ranger 4

  • -----
  • Posts: 323
  • Joined: 13 Jan 2017

Posted 24 October 2018 - 07:13 AM

Leaving out the H-Beta line coverage by using a narrower passband width centered on the OIII lines can often improve the contrast mostly by eliminating or reducing any faint continuum light between the OIII and H-Beta lines as well as cutting out unneeded continuum light in the "wings" of a wider filter's passband.   If you want to see planetary nebulae which are actually helped somewhat by the presence of the H-Beta line, try NGC 40 or Campbell's Hydrogen Star to name a couple.  Indeed, some use the H-Beta line filter on those two planetaries, although generally, I like a regular narrow-band nebula filter like the Lumicon UHC or DGM NPB on those objects.  Clear skies to you.   

I will do a filter comparison. Thanks for the suggestion.



#50 aatt

aatt

    Surveyor 1

  • ***--
  • Posts: 1844
  • Joined: 26 Jul 2012
  • Loc: CT

Posted 24 October 2018 - 12:08 PM

UHC is more of all purpose filter as many have already said. I second and third etc. that recommendation  for a first filter. Next would be O-III and finally a Hydrogen Beta. 




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: accessories, Celestron, eyepieces, LP, reflector, dso



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics