I do have a 2" 2x barlow from Bintel, http://www.bintel.com.au/Eyepieces-a...oductview.aspx but wanted to know if anyone has had experience with the 5x and 3x Barlows? Interested in quality and sharpness of the image.
I thought about getting these to try out so see if they will work with my system for planetary viewing, if they work ok, then I will consider the 5x or 2x powermates from Televue for imaging.
The scopes are a GSO 8"f/4, Skywatcher 8" f/6 and later on a GSO 12" f/5
I don't need to know about image scale etc.. as I have already seen the differences. Just interested in quality etc...
I think you'll find most of these are GSO barlows with GSO crossed out and Bintel written in with a crayon. Optically the GSO barlows are pretty good. Rather good when considering price/performance ratio.
I have the 5x barlow and have found the magnification is too high to get a sharp image with my 10" f4.8 newt. It might be ok on a clear night with great seeing, but I have not had one of those to try it out on yet.
Thanks Adrian and Rick, I aso remember now I can effectively increase the magnification of the barlow by using extension tubes etc... forgot about them... I found a formula to work it all out but need to find out the focal length of the Barlow :/
As Adrian said they are GSO barlows (all Bintel branded gear is GSO). I've only had experience with the 1.25" 2-element 2x barlow (the cheapest one) and the 2" standard 2x and ED 2x barlows. They all perform well enough for the price. I found no difference between the ED and non-ED barlows.
Much of the apo vs semi-apo vs achro barlow thing is about marketing. An achromatic lens is all that is needed to make a good traditional barlow free from any false colour. An "apo" or ED lens may still be relevant in short high magnification barlows ortele-converters/extenders.
I have not tried the newer models: the 3-element 2.5x and 5x units. I am tempted to get one for planetary imaging because they are cheap. Most GSO gear is bang-for-buck and I assume these would be too. They don't make anything that is appallingly bad. You definitely get what you pay for and often more.
I don't think you need to worry about sharpness of images. They will be as sharp as seeing and your scope allows. Barlow lenses are easy to make and hard to stuff up (although some still manage to do just that uhmm meade and there are the obvious junk ones that you can tell by looking at them).
I used to own the 1.25" and 2" 2x GSO barlows, but I sold the optical elements from both and only kept the empty barrels to use as extension tubes. There are better barlows out there for more money. I suspect the GSO barlows can be improved by better blackening of the insides of the barrels and by installing baffles. Most of what I gained from more expensive, better made barlows can be attributed to better stray/scattered light control. If I lost all my barlows I'd probably just get a basic GSO and improve on it in the way I described.
I am very fond of my extra long 2x barlows (Orion Ultrascopic style. 1.25" and 2", fully-baffled, Japan made). I don't know if anyone makes anything like these any more. Long barlows tend to result in flatter fields and less off-axis aberrations. They can make an inexpensive EP perform very well in fast scopes. Most barlows on the market today won't do that to quite the same degree.
I aso remember now I can effectively increase the magnification of the barlow by using extension tubes etc... forgot about them... I found a formula to work it all out but need to find out the focal length of the Barlow :/
I practice you don't need to worry about formulas. Just have a few different extension tubes handy and tune the magnification by eye. It helps if you have compression rings on everything and no safety undercuts on the barrels. That way you can "telescope" one bit inside another: continuously adjusting the light path shorter or longer as needed.
Thanks for the info Steve, i agree about the experimenting... I had a 2" 80mm extension tube made up at work once, I might see how that goes with the Barlow Also got a couple of 50mm and a 35mm so I have a few to play with. Now to wait for clear skies again...
Here is the scope with Barlow and a couple of extension tubes on it.... I think its a little overkill though.... may require tweaking when the weather improves.
It usually does end up looking ridiculous if you push the power high enough and your focusser needs to be up to the job of coping with all that torque from the long barlow+EP barrel (looks like yours is a good one). One thing you may have issues with is focusser travel. Long barlows are more flexible for this sort of setup.
How well blackened the insides of your extension tubes are will matter for contrast. They should be matte black with no shiny bits. Installing a baffle or two may also be a good idea.
You love the moonlite its a great focuser, so bloody strong and everything feels really secure.. I think I might have enough travel, if now always got more extension tubes...
The raw aluminium tube has a black felt inside. The others are standard anodised black.
Hi Andrew.
I use the Bintel 2" ED 2x barlow with my bintel 12"dob and find it very good. Also, I found that for imaging, you can unscrew the lens section off the bottom of the barlow and screw it on the bottom of a 2"-T2 adapter.
Cheers!
Also got a couple of 50mm and a 35mm so I have a few to play with. Now to wait for clear skies again...
