Optolong Venus-U Filter 1.25"

[Pete Presland]

I have been looking around for a Venus filter, including a BG39 glass filter. I have come across this one Optolong Venus-U Filter 1.25" http://www.365astronomy.com/Optolong-Venus-U-Filter-1.25.html on Ebay for £99.

Anybody out the have any experience of it?

[neil phillips]

Looking on the Net I can't see one Venus image posted with this filter. It doesn't seem like there is a lot of users out there Pete. From what I can tell I think its a clone of the Baader U Venus filter. Which did have a IR leak. Its odd actually because the graph you posted showing  transmissions, shows a very small IR peak. But on the ebay sell site, it shows another graph by sky's the limit where that peak has suddenly gone ? Not sure what to make of that. Without using one I can not tell how serious that small IR spike would actually be. It doesn't look serious. But I am uncertain. As far as dedicated UV filters go for the price. I am also tempted its worth a punt. At some point if any mild leak became annoying. A IR blocker ( yes I know back to that again ) could be used to rid it of the problem. I suspect in use it may not be needed. But I am uncertain of this, as a cautionary Note. I guess these questions could be directed at Sky's the limit for there opinion. Especially why the IR peak on there graph is absent. When its plain to see on Optolong's own curve graph. Its a good price for UV though. Dedicated filters do well in my experience. But then I had a Schuler and Astrodon  both rather different, but good filters. Especially the expensive Astrodon which has the highest transmission of 90%. The optolong at 80% and the schuler less than either of those. But was still a good filter.