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Orion SKYGLOW Broad-band Light Pollution Filter

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#1 mloffland

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Posted 12 January 2010 - 03:32 PM

Orion SKYGLOW Broad-band Light Pollution Filter

By: David Knisely

#2 FirstSight

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Posted 12 January 2010 - 04:33 PM

Another solid practical and technical review of filters by our resident filter-wizard.

#3 Ed Sunder

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Posted 12 January 2010 - 05:44 PM

I've noticed a similar threading mismatch on my Orion SkyGlow Imaging filter - it's like it's the wrong thread pitch. It can go on very securely (almost too securely), but I'm worried that over time it'll mess up either it's own threads or those on a nosepiece. Anyone else run into this?

Thanks for the review, by they way!

#4 John Kocijanski

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Posted 12 January 2010 - 06:35 PM

Thanks for the review. I had one a while back but I tended to use the narrowband filter I have more so I got rid of it.

#5 yowser

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Posted 12 January 2010 - 08:12 PM

I had the same problem with difficulty threading an Orion UHC 2" filter on my Astro-Tech and ES eyepieces as well as my William Optics diagonal. So I sold the Orion filter and went with Lumicon.

#6 8ballsct

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Posted 12 January 2010 - 09:46 PM

Another one of your steller reviews. However I have been told that glass in metal holders are often slightly loose to allow for the different expansion rates. Is this wrong?
John H

#7 David Knisely

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Posted 12 January 2010 - 10:58 PM

Another one of your steller reviews. However I have been told that glass in metal holders are often slightly loose to allow for the different expansion rates. Is this wrong?
John H


In some cases, that may be correct, although glass usually has a lower coefficient of expansion than many metals. However, this is about the first time in many years I have seen a new filter that did that (loose in its mounting). The tightening issue was a very mild one, as it took only a very slight turn of the ring to secure the filter in its mount so it no longer rattled, and I would never really crank things down, as that might cause problems. Clear skies to you.

#8 8ballsct

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Posted 13 January 2010 - 12:45 AM

Thanks for the clarification. I have gained much insight from many of your postings over the years
John H

#9 Midnight Dan

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Posted 13 January 2010 - 09:38 AM

Hi David:

Thanks for the nice review. I'm moving to 2" filters and reevaluating my filter needs so this comes at a good time!

I have a question about light pollution levels. When you use terms like "moderate" and "mild", can you define what you mean in terms of SQM or ZLM? Also, when you mention 5.6 ZLM, is that a visual evaluation of the sky or are you using a meter of some kind?

In general, I view in skies that are in the 20.4 to 20.7 SQM range and I'm wondering how effective this filter would be. I don't know if that qualifies as "mild" or "moderate" pollution" for you.

-Dan

#10 jrbarnett

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Posted 13 January 2010 - 01:18 PM

David:

First rate review. The pictures really help convey the impact of each of the filters.

I have an old Orion Skyglow filter (1.25") from the "Made in Japan" era. If you would like to borrow it to play with/compare, PM me and I'll send it along for your evaluation.

Regards,

Jim

#11 David Knisely

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Posted 13 January 2010 - 02:34 PM

Hi David:

Thanks for the nice review. I'm moving to 2" filters and reevaluating my filter needs so this comes at a good time!

I have a question about light pollution levels. When you use terms like "moderate" and "mild", can you define what you mean in terms of SQM or ZLM? Also, when you mention 5.6 ZLM, is that a visual evaluation of the sky or are you using a meter of some kind?

In general, I view in skies that are in the 20.4 to 20.7 SQM range and I'm wondering how effective this filter would be. I don't know if that qualifies as "mild" or "moderate" pollution" for you.

-Dan


I have yet to "bite the bullet" and purchase a Sky Quality Meter, so I generally use the visual Zenith Limiting Magnitude (ZLM) for my estimates. On a moonless night, for example, my front yard has a ZLM of typically between 5.0 and 5.7, although portions of the sky closer to the horizon are considerably worse. I sometimes use following light pollution scale:

SEVERE: only stars brighter than mag. 4.0 are visible with bright skyglow over most of the sky.
MODERATE: mag. 4.0 to 4.9 stars visible (variable skyglow depending on direction of observation).
MILD: mag. 5.0 to 5.9 stars visible (some notable darker areas visible).
DARK SKY: mag. 6.0 to 6.8 stars visible (dark, sometimes with a few light domes along the horizon).
PRISTINE: mag. 6.9 and fainter stars *consistently* visible (little or no light pollution in any direction).


Somewhere in the moderate light pollution range, the broad-band filters tend to lose their effectiveness, as the skyglow intensity becomes fairly high even in the passbands of the filters. Clear skies to you.

#12 g__day

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Posted 13 January 2010 - 07:36 PM


A query for this review - does this filter shift primary colours by varying degrees making it very hard to get correct colours from an astro-photograph?

When I first looked into sky glow filters - I was warned by the experienced astro-photographers from iceinspace.com.au to beware that alot of filters shift your colour spectrum - so much or so incosistently across colours that its all but impossible to restore correct colours.

The only one that was recommended that cut enough sky glow to allow me to double my shots whilst not loosing colour fidelity was the Hutech one.

Has this been the same experience folk have found here - when you move beyond visual astronomy of faint objects from light polluted skies?

#13 Midnight Dan

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Posted 13 January 2010 - 07:55 PM

Hi G_day!

I don't do astrophotography, but the guys over in the imaging forum seem to recommend the Astronomik CLS as being as good, if not better than, the Hutec.

-Dan

#14 David Knisely

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Posted 14 January 2010 - 12:28 AM

A query for this review - does this filter shift primary colours by varying degrees making it very hard to get correct colours from an astro-photograph?

When I first looked into sky glow filters - I was warned by the experienced astro-photographers from iceinspace.com.au to beware that alot of filters shift your colour spectrum - so much or so incosistently across colours that its all but impossible to restore correct colours.

The only one that was recommended that cut enough sky glow to allow me to double my shots whilst not loosing colour fidelity was the Hutech one.

Has this been the same experience folk have found here - when you move beyond visual astronomy of faint objects from light polluted skies?


There is a slight color shift for continuum objects (stars, galaxies), but for emission nebulae, the colors should be the same. The filter does not significantly attenuate any of the major nebular emission lines. It does increase the exposure time required however. For situations where some light pollution is present, the "single notch" (5500 to 6250 angstrom) broad-band filters tend to work a bit better than the multiple passband models like the Hutech LPS filter, as the broad ugly band of high-pressure sodium contaminates the yellow 5500 to 5800 angstrom secondary passband. Clear skies to you.

#15 deSitter

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Posted 14 January 2010 - 01:24 AM

Good deal,

Hey that looks like a copy of Becvar as backdrop! Miss mine.

-drl

#16 David Knisely

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Posted 14 January 2010 - 01:47 AM

Good deal,

Hey that looks like a copy of Becvar as backdrop! Miss mine.

-drl


Nope, the atlas underneath the filter is the 1st edition of Wil Tirion's Sky Atlas 2000.0 (although I do have a copy of Becvar's ATLAS OF THE HEAVENS (1950.0, Skalnate-Pleso) sitting on the shelf next to the computer). I used the old Becvar atlas for many years and it served me pretty well, although the 2nd edition of Sky Atlas 2000.0 I have now is somewhat better (and Uranometria 2000.0 is better still). Clear skies to you.

#17 Downward Bound

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Posted 19 January 2010 - 10:10 PM

Thank you David :bow: Another very informative and useful review. You're contributions are greatly appreciated!

#18 o1d_dude

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Posted 20 January 2010 - 07:20 PM

Thanks for the review, David.

I've been thinking about a 2" filter but have held off due to the cost. The Orion is worthy of consideration at reasonable cost.

#19 Midnight Dan

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Posted 30 January 2010 - 04:34 PM

Hi David:

Just curious, what did you use for your color balance setting in your camera when you took those pictures? I assume you did not have it at automatic since you wanted to show color casts.

-Dan

#20 David Knisely

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Posted 31 January 2010 - 01:41 AM

Hi David:

Just curious, what did you use for your color balance setting in your camera when you took those pictures? I assume you did not have it at automatic since you wanted to show color casts.

-Dan


No, the camera was on full manual mode but using AWB (automatic white balance), although since the 350D is unmodified, the red response of the image will be somewhat muted compared with cameras that have been modded or those with better H-alpha response. I was more concerned with the overall light density in various parts of the image rather than on the precise colors shown. The intensities pretty much reflected the differences between the filters I had seen visually in the spectroscope and when used in the telescope. Clear skies to you.

#21 SimonTelescopium

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Posted 06 April 2010 - 01:55 PM

Hi I have the Orion Ultrablock LP filter, how does this compare to the skyglow? Living in London UK, a LP filter is essential but the ultrablock does result in a significant blue cast to all the stars. When I first used this filter on M42 with my ED80 it punched me in the face! Without it it leaves this impressive nebula, unimpressive...

#22 David Knisely

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Posted 06 April 2010 - 02:43 PM

Hi I have the Orion Ultrablock LP filter, how does this compare to the skyglow? Living in London UK, a LP filter is essential but the ultrablock does result in a significant blue cast to all the stars. When I first used this filter on M42 with my ED80 it punched me in the face! Without it it leaves this impressive nebula, unimpressive...


Well, they are two different classes of filters. The Orion Ultrablock is a standard narrow-band "nebula" filter rather than a broad-band Light Pollution Reduction filter like the Skyglow is. For emission nebulae, the Ultrablock offers visibly better performance than the Skyglow, although the Skyglow filter does help nebulae to some degree, especially under mild light pollution or true dark-sky conditions. For other "continuum" emitting objects like stars or galaxies, the Ultrablock dims them noticeably more than the Skyglow filter does. Thus, the Ultrablock should be used mainly for emission nebulae only. As for the bluish-green color that the Ultrablock imparts to stars, that cannot be helped, as the passband of the Ultrablock is designed to only let through the bluish-green emission lines of H-Beta and Oxygen III while blocking everything else. One of the few nebula filters that does not impart quite that much of a bluish or greenish hue to the stars is the DGM Optics NPB nebula filter, but the differences in performance between the NPB and the Ultrablock are fairly minor in terms of what each may reveal in emission nebulae. Clear skies to you.

#23 SimonTelescopium

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Posted 06 April 2010 - 05:15 PM

For me the first consideration has to be blocking the light pollution rather than trying to glimpse that ellusive nebula. It's cloudy so I just tried a little experiment photographing the blanket cloud with different LP fiters - never thought of doing this before - to see how much the filters I have let through of the unwanted light - the hypothesis being at a very dark site on a cloudy night I would get a black image without filters, so assuming these filters let through the wanted wavelengths then the darker the image the better - not sure how valid this is but the results were interesting - if exactly as expected - I imagine comparison images of an object might be more instructive but I don't have a filter to remove the clouds (yet) :crazy:

Attached Thumbnails

  • 3729018-LP Filter Comparison.jpg


#24 kev721

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Posted 07 April 2010 - 02:11 PM

David, if I were to go out and buy one filter to improve contrast and never buy another filter again, what is my best bet for across the board improvement (nebulae, galaxies, etc.)?

Price is a factor.

#25 David Knisely

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Posted 07 April 2010 - 02:42 PM

David, if I were to go out and buy one filter to improve contrast and never buy another filter again, what is my best bet for across the board improvement (nebulae, galaxies, etc.)?

Price is a factor.


You can't, as the filter choice depends on the object. Open and globular clusters aren't helped much by any filter. Some contrast improvement for the larger more diffuse galaxies may be seen with the broad-band LPR filters (Orion Skyglow, Lumicon Deep-sky, DGM Optics GCE, etc.). However, what improvement there may be is fairly mild at best and is sometimes not seen on all galaxies. For emission nebulae, the clear "1-filter" choice would be the DGM Optics NPB narrow-band filter. However, there are a few diffuse nebulae (and many planetary nebulae) which an Oxygen III filter will tend to be most effective on. This is why most amateurs will tend to get both a narrow-band nebula filter and an OIII line filter for viewing nebulae. Clear skies to you.


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