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Sirius CEF & NEB1 Filters vs. Lumicon UHC

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Date: NA
Price: Sirius Optics...1.25" $74.95 2" $119.50
Lumicon UHC.....1.25" $99.50 2" $199.50 
Design: Contrast Enhancement filter vs. the Lumicon LPR filter
Description: 1.25-inch and 2-inch filter with common threads.  Designed to increase contrast and provide a minimal reduction in light pollution.

Review

Here's an initial "first light" impression of my recently purchased 
Contrast Enhancement (CE1) and Nebula (NEB1) filters from Sirius 
Optics. I would like to say that I didn't have the best sky conditions. Transparency was 6-7 with an average limiting visual magnitude of 5.2. I am also including Lumicon's UHC for comparison purposes since I have made many observations with it over the past 15+ years. I used my Skywatcher 150mm achromatic refractor. Additionally, the views I got were shared with 3 of my astro buddies. This amounts to about 100+ years of combined observing experience. I didn't let them know what kind of filters they were looking through. I simply said I had some new filters and asked if they wanted to take a peek. The comments below reflect our combined opinion on some very familiar objects.

Vega

The CE1 has some very interesting qualities in regard to its spectral range. The image presented by Vega is well known to us achro users. At 150X, Vega usually has a large blue/violet halo and 2 diffraction rings around its disc. With the CE1, the blue/violet halo turned into a blue/green ring. Vega's color had a yellow/orange cast and its disc had become noticeably smaller. Vega's airy disc was sharper and had more brightly concentrated light than the "naked" view. It looked like a "bull's eye" inside this ring. This is not the expected aqua tinted star color. 

M13


I tried M13 during the last moments of twilight. At 60x and 109x, the 
core of M13 seemed to be about 15% brighter with the CE1 and the core's stars were resolved. The background sky was dark gray at this time. The NGC galaxy close to M13 was invisible without filter, but appeared on the edge of visibility with the CE1. 

Conclusion


With the sky getting darker the "naked" view was preferred. When it 
got darker, the unfiltered view showed M13 to its full extent from core to edges. As a side note, at 60x with the CE1, the sky background was as dark as unfiltered view at 109x. These dimmer stars appeared "natural" in color.

Lagoon Nebula


The Lagoon was about 15-20 degrees above the horizon in a light dome. 
It was not visible to the naked eye. 80X magnification was used.

The CE1 made the sky blacker with a great view of the gas clouds and 
associated star cluster (about 36 stars visible in cluster). The 
nebulosity had almost doubled in size as compared to the unfiltered 
view. More dark lanes were visible. The impression was that of a very 
natural and aesthetically pleasing view. 

With the Lumicon UHC the Lagoon took on its familiar shape. All 
nebulosity was brighter with higher contrast compared to both the sky 
and dark lanes. Star cluster was reduced to about 24 stars. It also 
produced the blackest sky. 

With the NEB1, wow, wow! Lots of undulations. All nebulosity is brighter and more extended! It grew almost 1.5 times brighter and 1.5 
times larger than the UHC's view. Star cluster had about 31 stars. There were noticeably more brightness variations in cloud and dark lane structures. What really struck us was the "dimensionality" this filter imparted. 

Conclusion


The CE1 and NEB1 really did the Lagoon justice in different ways and 
were unanimously preferred. The CE1 gave the "purist" view. The NEB1 
gave the most detailed view and had the biggest "wow" factor. The UHC 
just gave a flatter view with the darkest sky background and the least 
amount of visible stars. Note: The number of stars in the cluster was 
just a quick count.

M27


At 109x this planetary, for all intents and purposes, doesn't really 
need a filter. 

That said, the CE1 showed a bit more than the profiles and details that are visible in those photos we've all seen. The lobes showed their brightness variations with more starkness. The loops were fully extended around the "apple core" and really showed well for a 6" aperture. The star field wasn't suppressed that much at all. The dimensionality of this view was strikingly impressive. It left the "air" in the view.

The UHC once again had the darkest sky background and the most star 
obliteration. Those line of sight stars that are superimposed in front 
of the planetary would blink.

The NEB1 closely showed the profile and texture variations that's most 
familiar in photos. It showed the distinct "apple core" shape with short arcs extending from the lobes. All the usual superimposed stars (4) were there without the blinking.

Conclusion


The CE1 was clearly the best and held true even with magnifications as 
high as 200x. 

The Veil


I used a 24mm Wide Field Eyepiece. This gave 50x and has a FOV similar 
to a 32mm Plossl.All filters showed both extensions to good effect but in varying degrees. 

The CE1 once again showed the most "natural" view. 

The UHC showed the hardest edges and most contrast separation between 
it and the sky background. The UHC gave a higher visibility factor

The NEB1 showed a bit more of the ribbon-like contours that one 
associates with images in larger scopes. This appeared to me in one 
small section of the Veil's brighter portion. 

Conclusion


On this object, most of us gave the nod to the UHC. 

Final Conclusion


There were many other objects observed on this night. On balance, the 
performance of these filters came down to the following:

The CE1 drew unanimous praise even though the NEB1 gave way more 
dramatic effect, say on the Lagoon. Again, what stuck out most to all 
of us in regard to the Sirius Optic's CE1 and NEB1 filters was that 
"dimensionality". This word was spoken repeatedly. 

The CE1 was clearly welcomed by those of us who don't like to use 
filters. This filter just won't squash the life out of the field of 
view and didn't have that "I'm looking through a filter" feel to it. 
Additionally, the contrast boost was quite noticeable with an 
on-average sky darkening effect that is similar to doubling the 
magnification.

The NEB1 had the best "visual drama with brightness gradation scale". 
There were plainly more variations of brightness in nebular cloud 
structure. It showed more detail and stars than the UHC.

The UHC is a familiar frame of reference in nebular filters. It more 
aggressively blacked out the background and stars. It also had the 
flattest dimensional "feel" to the views we had. 

Lastly, we all agreed that it was easier to achieve a hard focus the 
CE1 and Neb1.

Submitted by Sol Robbins - solrobbins@aol.com - USA

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