Telescope Reviews: ETX-80 and filters

Hello...I haven't seen too many posts about using filters with the ETX-80, so I thought I'd post my results. Last night I was able to take the scope out for a short time (until thin clouds and dew chased me away...I'd forgotten to bring my dew shield) but it gave me a chance to play around with some filters a bit. I recently purchased the Astronomic CLS & UHC-E filters. The CLS is allegedly a clone of Lumicon's Deepsky and the UHC is a mid range filter...with a bandpass about midway between the CLS and a narrowband UHC filter. My target was the Lagoon nebula (my latest favorite Summertime object...I just can't get away from gazing at it for long stretches). Anyway, with out the filter I have a decent view and can just make out some structure to the nebula. With the CLS filter in place (and using the 9.7EP), the sky is darker and I can easily see structure in the nebula, with a pronounced dark lane and subtle wisps of veins running through it. I was impressed at the improvement. I'd say detail went up 40 to 50%. (This was in mag 4 skies with considerable man made sky glow).

The UHC-E filter seemed gave me quite a bit more contrast, but this was offset by the darker image overall. However...whereas without the filter I thought I could just barely make out the Trifid nebula (it was so faint I could easily discount it for a bit of scattered light), it was clearly visible in the UHC as a faint wisp of light that stood out against the background. (I forget which eyepiece I was using at the time). I also tried to check out M57, observing first without the filter. I then dropped the filter in and saw only a dim haze. Upon checking my objective, it was dew covered so that was the end of that!

Tonight I spent a bit of time observing the Moon. It was my first lunar observation through the ETX-80 and it's superb! Much less chromatic aberration then I was expecting. With that said, I still popped in the Orion V-block and the view was breathtaking. Tiny little craters that were not readily apparent across the maria using the 9.7 and the barlow suddenly popped into view using the filter. The rough edges of craters also looked much more crisp. I was also able to make out some tiny pinpoints of light on the dark side of the terminator where the sun was just beginning to catch the tops of mountains and crater ridges. (These pinpoints were also visible without the filter, but the filter seemed to make them stand out more...perhaps due to the image being slightly less intense and thus easier on the eyes). Most of my lunar observations were made using the 6.4mmEP. I was amazed at the subtle details that were visible...I liked the image better then what I get with me Newtonian (although it may be that I was simply able to enjoy it more since I wasn't having to spend my time chasing the moon...I simply made a correction every minute or so).

Final conclusions: A broadband skyglow filter can be useful with this scope under light polluted skies. A more narrowband filter is useful, but watch that exit pupil...you have to do a balancing act there between magnification and image brightness. For lunar observing get yourself a V-block or other fringing filter....they do wonders for you image!

Craig