Low power fun with a filter

[RobertI]

Another gloriously clear and warm night last night, decided some more binocular observing was in order. Lay down and scanned the Cygnus and Cepheus region overhead. The orange star Zeta Cephei was very prominent and the nearby Garnet Star, was even more so, burning with a deep rusty red. Delta Cephei was a nice double of contrasting colours separated by 40". I decided to concentrate on some of the dark lanes, which required a slight adjustment to look for the absence of something! Once tuned in, the more I looked, the apparent they became with some very prominent long dark lanes and holes. One prominent yellow star seemed to sit right in the middle of a dark hole. I stumbled across a lovely close grouping of three stars comprising the orange Omicron Cygni , the white 30 Cygni and a third blue/white star.

I have never seen the North American nebula for sure, so thought I'd have another go with the bins. As usual I could see a brightening in the area, but no shape. On a whim I thought I would try holding my UHC-E filter in front of one of the eyepiece lenses and bingo, it popped into view! First time ever. Closing each eye to compare the filter and non-filter view confirmed how effective this filter was, the nebula having no shape at all in the unfiltered eye, but a clear shape in the filtered eye, with the gulf of mexico clearly visible. Popping the filter on my 60mm scope and the view was also very clear. The filter also made viewing the dark lanes much more enjoyable too. Sadly I didn't have time to try out any other nebs, but was more than happy to have seen the elusive North American Neb.

A final note. I noticed that the view through the 60mm scope seemed to be much smaller (ie: lower mag) than the bins, even though they were both 10x. So I looked through the bins with one eye only, and the view was similarly small. But when opening the second eye to get stereo vision, the view suddenly increased in size dramatically, almost like doubling the magnification. I know this is a optical illusion, but just shows why bins provide such good views. Does the same hold true of binocular viewers for scopes, or is the effect less marked because there is only one objective? 

Thanks for reading.....    

[Louis D]

1 hour ago, RobertI said:

Does the same hold true of binocular viewers for scopes, or is the effect less marked because there is only one objective? 

I don't know if the magnification seems any higher, but the apparent field of view definitely seems wider with two eyes in a binoviewer.  That's why I find 60 degree eyepieces fine for binoviewers.  They feel like 70 degree eyepieces in monovision.