What size threads for front of 3.5" Questar?
Posted 26 May 2012 - 08:50 PM
Posted 26 May 2012 - 09:39 PM
Posted 31 July 2012 - 08:18 PM
Posted 18 February 2014 - 01:30 PM
Posted 03 March 2014 - 03:12 PM
The optics are very good, and they use high-quality Schott glass.
There are two types of coatings available: a single coating (SC) and a multi-resistant coating (MRC). Make sure you buy the one you want. The MRC is actually harder than glass so is very scratch resistant, and you don't need to clean the MRC very often anyway because it is water-repellent. Good for dewy nights and wet days.
The B+W ring is made of brass, so is very strong and resistant to corrosion/oxidation.
The brass won’t cold-weld to steel or aluminium, so won’t get stuck on the scope if it gets left on for a long time.
The brass makes it easy to spot a fake. There are apparently cheap Chinese fake filters in the market made of aluminium, so buyer beware! Buy from a reputable source. The brass is noticeably heavy in the hand (the filter weighs 68 grams) and you can see the yellow brass colour coming through the fine laser-etched lettering on the front of the filter ring.
The B+W filter is also available in both Clear MRC and UV MRC versions. I got the UV MRC because I’ll usually be looking through miles of atmosphere (either in daytime or nighttime). If I was going to use it mostly as a long-distance microscope or other short-range activities I’d consider the Clear version.
Posted 04 March 2014 - 03:05 PM
I got the UV MRC because I’ll usually be looking through miles of atmosphere (either in daytime or nighttime). If I was going to use it mostly as a long-distance microscope or other short-range activities I’d consider the Clear version.
Well, you made the good choice!
In a Questar 3.5 with R1 secondary, the light passes twice through a thick meniscus lens made out of glass that is a good UV absorber.
So I doubt there would be any difference between the 362$ Clear MRC 'filter' (it does not filter anything) and the 325$ Clear UV Haze MRC filter.
But you are saving 37$ with the UV Haze, since it is made of regular glass which absorbs UV like the meniscus lens, and the Clear one has to be made of some special glass so as not to filter out UV...
But both are nice filters, no question.