Levenhuk CLS Filter

Started by Rod Kaufman, 12/02/2013 06:36AM
Posted 12/02/2013 06:36AM Opening Post
I've been interested in using a CLS filter for some time now but I don't feel like forking over approximately $170.00 for a 2" astronomik model. If you reference Phil Harrington's article in my thread regarding tuning your eyepieces and filters, you'll see he designates it as a broadband filter and rates it a "4" on a 0-5 scale with M81 being easily visible. Imagers reportedly use this filter as well.
I can't say whether the Levenhuk 2" model, which goes for around $89.00, is the same as the aforementioned model. I could only find one review of it on a google search and the latter was a translated page from a Russian amateur who did a spectral test on it and described it as "pretty good" in meeting its design parameters as a deep sky filter. Levenhuk's advertizing states it can be used for photo-visual work so I may get one for use with my 2" eyepieces and report on its usefulness in suburban viewing. I find my astrotech 1.25" broadband filter works well with my 16" scope and a 10mm Ethos eyepiece for viewing some galaxies in front of my home whereas my Orion broadband model is too aggressive and dims the sky by a half a magnitude which makes it less suitable for viewing galaxies. My hope is the Levenhuk unit is a bit less aggressive than the Orion model and therefore may be of use in viewing certain galaxies. We shall see...
Posted 12/23/2013 07:20AM #1
Ya know, I've got a boatload of new stuff and the weather has been absolutely Winchester. Windy, cloudy, and even if it's clear the seeing has sucked. Two new apos, a new filter and eyepiece, and for various reasons I haven't even unpacked one of the apos.
Finally, tonight(12-22)I was able to set up in front of my home and get the scope up and running ahead of the rising moon. Seeing was still ify at 3/5 but sufficient enough to allow for an eyepiece/filter comparo.
First up, my take on the meade series 5000 20mm 82 AFOV 2" eyepiece. 20MM isn't what I normally use in my 16" f 4.5 dob, preferring instead to user shorter focal length eyepieces for DSO and planetary observations. Still, there are times a longer focal length eyepiece might do better on a larger extended object so I considered either a 20mm meade 82 or an ES 100. I decided to go with the meade because it cost less and the reviews I've read were decent enough. However, I've seen some good views thru the ES100 thru other scopes and I believe it has better edge correction than the meade over its larger AFOV. Still, the meade is immerse in its views despite the early appearance of coma about 80% outward towards the edge. A paracorr is required to get the most out of it. However, the eyepiece barlows quite well and together with my GSO 2X unit, the stars appear sharp to the edge and views of Jupiter during periods of steady seeing were excellent. I felt the combo outdid the 10mm ethos although the appearance of Jupiter appeared more magnified thru the 20mm/2X GSO combo so I suspect the spacing of the lens elements was giving me more power than I realized at the time. Anyhow, if you want a relatively inexpensive 20mm 2" eyepiece that provides a widefield and you want to power up with an inexpensive barlow, the aforementioned combo is hard to beat.
The CLS filter is a winner for my purposes. It's a broadband filter that's non-aggressive, meaning it doesn't dim and kill the star images like my Orion broadband skyglow filter tend to do and the latter makes it unsuitable for galaxies. I found the CLS filter to be perhaps a bit more mild than my preferred galaxy filter: the astrotech broadband filter. I use the latter 1.25" filter with my 10mm Ethos and I've had some nice views of certain galaxies with the combo. I compared the 1.25 astrotech/10mm Ethos with the 20mm meade/2" CLS filter on several objects this evening in front of my home.
First, on NGC 278: the galaxy was visible with or without the filters, perhaps a bit more prominent in the meade/2X power combo than the 10mm Ethos astrotech combo.
Second: NGC 2403 in the camelopardalis, better in the meade CLS 2X barlow combo.
Third: emission nebula 281 in Cassiopeia: similar in both the CLS and astrotech filters. Of interest since the Observer's Guide notes either a UHC or O111 is required but both broadbands picked it up without too much difficulty.
Fourth: NGC 891: difficult under each filter eyepiece combo, discernible but a real challenge.
Fifth: NGC 1491: an emmission nebula in Perseus: better in the CLS meade/barlow combo.
Sixth: NGC 1023: galaxy in Perseus: tied in both.
I'll have to wait for dark skies for another test of the cls filter but it seems very promising now...