80mm dia, 500mm FL, f6.2 semi APO telescope

Hi,

I wrote a rather extensive review of the APO upgrade from William Optics that fits this scope and others.

Here are two links to the review on astronomy sites...
http://www.astromart.com/articles/article.asp?article_id=398
http://www.cloudynights.com/item.php?item_id=1420

I have used it extensively with a Canon 20D and taken several pretty nice birding pictures so far. I have them here
http://www.birdforum.net/pp_gallery/showgallery.php/cat/500/ppuser/33350

You can also see a number of pictures on the William Optics website Gallery to get a feeling for what the improved APO optics can provide.
http://www.william-optics.com/wo_gal/catalog/

Hope this helps anyone who has a compatible Achromat or Semi-APO and is interested in upgrading it and seeing the difference that it will make.

Timm

Hi there I got one of these scopes and I wasnt really satisfied with the optics,
more about that later. The scope is quite fancy looking but it does do what it says
on the tin, though Im a little unsure about the Semi-APO descriptions these
companies are using as having spoken to people who know about optics these are a
design which is about 200 or more years old and are actually called Achromats.

The scope is a little on the heavy side compared to spotters but its very portable
for an astronomy & spotting crossover telescope.
The real advantage is that you can use loads of eyepieces and other gadgets with the
scope and you can use it for digi-camming or video - the focuser is sturdy enough to
hold a large SLR with battery pack too which is a real departure from most spotters
and thats its strength. Also you can (theoretically) use it at up to about 150 x
power according to manufacturers though really it works up to about 60-80 x before
it packs up - Im not satisfied with the optics which as you can see.
I spoke to some people about the optics and they explained that this is actually
quite normal. Binoculars and small telescopes usually have achromat lenses - cheaper
to make. Anyway I looked at the APO versions of these scopes because I realised the
mechanics were basically sound, and I ended up buying an Apograde lens cell which is a way to get better performance from just about any of these 80mm William Optics clone scopes. I decided to do this after a lengthy discussion with the folks at a UK company called Altair Nature Optics who do a lot of William Optics products they have a info page on their web site below, which explains the concept with before & after pics:

http://www.bazaarbuilder.com/cgi-bin/nickaltair/myshop.php?merchant=nickaltair&prodid=496&sinprod=1

Basically its a spare lens cell for about 300 quid which screws into the front of these 80mm scopes and upgrades the lens to a better colour corrected one. It also included an extension tube and a really great little dual speed micro focuser knob which attached to the existing focuser and made it so much easier to get a fine focus. Well the whole upgrade package made an absolutely amazing difference - I could really see a lot more, especially at about 100-140x power which previously the scope just wasnt capable of, and started using it for having a look at the moon & planets. Before there was always this purple haze around bright objects in the image just like in the photos, and it was always a little soft. Contrast and sharpness was so obviously improved too it was like night and day. I know this is a birding forum but its really amazing what you can see with these things if you point them upwards, or at really distant targets - especially Saturns rings and such.

Anyway, I had some cheap eyepieces with the scope, so I decided to sort out that end of the scope too. Ended up getting a whole lot of extra stuff to use the scope on land and sky. I got a 45 degree prism diagonal (also William Optics) to give an erect image and also William Optics 20mm & 4mm wide eyepieces which have given amazing views (I wear glasses so the eye relief is great and the field of view is stunning). Took this up to Beachy Head one evening, and it was great from the landscape to ships to the moon and back.

Anyway, the controversial point is that it equals my Zeiss Diascope in every way when used with the William super wide eyepieces (which are unreal) and is sharper at high powers. In my opinion its far better value than the Zeiss which cost a LOT more than the whole package and upgrade and 2 eyepieces - but then this lens was designed for astronomy at high power, so I guess thats to be expected. To be fair, the Diascope is better to use for spotting only, and its tougher and more ergonomically friendly - plus it comes with a zoom which cant work with the same performance at high and low powers. The Zeiss is great for what it is, but as soon as you want flexibility the 80mm APO beats it in every way except for toughness, portability and durability. Im not fussed though as the views are worth it.

I have spent about 600 on accessories now! Those folks at William Optics keep making more gadgets (clever them) to add on their the scopes, which work with most of the 80mm clones out there, so now that same scope is a real performer. I kind of feel like one of those people who has supercharged their old mini or something...
With the benefit of hindsight, Id probably buy a William Optics 80mm APO in the first place as I wouldnt have to upgrade and so-on.

Anyway, bottom line is that these 80mm Achromat scopes dont really cut the mustard. The mechanics are fine but the optics just dont do it, sharpness, contrast, and colour are way below par and new technology wins. There are a lot if these semi-APO scopes around and Im not sure this marketing term is fair either, as you get the same lens design which has been around for 200 years (or so).

However, if you do already have an 80mm Achromat like the Revelation already, and get a bit more budget, then check out the upgrade options to APO. Its really worth it. If you have enough for a
William Optics original 80mm APO in the first place, then dont hesitate.

PS: If you decide to upgrade, talk to your dealer about compatibility, or have a look at that webpage link above BEFORE you buy or take your scope in to have it checked out (which they offered to do). I actually went on to buy some other William Optics stuff over the last few months as I sometimes end up in Norwich for work. I recently bought a small 50mm Toucan Spotter for birding, which I keep in the car for scenic drives after work too - I will do a review soon!

I have come into birdwatching from astronomy. This means I have a slightly different view on telescopes than a lot of other birding enthusiasts (I guess!). In my time as an astronomer, I have now had 6 different scopes, starting with a huge 8inch reflector, working down in size to this little beauty, and definitely my last scope. I could not handle the bigger scopes due to a worsening disability, so size became more important as time went on.

Right, so what is it?

It is a small but fairly heavy 80mm diameter air spaced fully multicoated doublet objective mounted in a heavily baffled, flat black interior tube, 500mm focal length, f6.2 scope, with a foot mount for std photo tripod mounting, and a two inch focuser receptacle for eyepieces and diagonals. 18inch overall with dew shield/lens hood extended, 15inch when retracted. Bought as new, you would have got a 2inch 90 degree diagonal and a 2inch to 1.25inch adaptor, as most popular astro eyepieces are one of these two diameters. I decided to get a 25mm (20x) and a 15mm (33x) with 1.25inch fitting to start, shortly to be adding 9mm (55x) and 5mm (100x) eyepieces. The mag is calculated (if you didnt know) by dividing the focal length of the scope (500mm) by the focal length of the eyepiece, so 500mm/25mm=20x etc. Close focussing is easily achieved down to 2m with an extender tube.

For visual work I use a 45 degree diagonal, giving me a comfortable viewing position, similar to other proper spotting scopes. This also gives me an erect image (whereas a star diagonal would be upside down/back to front, or any combination of those two).

Visually the scope never disappoints, and recently I had the chance to compare it to some top names (Leica, Swarovski, Opticron, Zeiss etc). Yes, the other scopes gave a flatter field, but the eyepieces had strange kidney beaning and blackouts, so Im guessing their exit pupils were very small. I can move my eyeball about and not get any blacking out at all with any of my eyepieces. Chromatic aberration is present but only if viewing against a high contrast background e.g. - bird on branch against white/blue sky , at high power magnification. At low powers it is NOT noticeable at all.

As f6.2, it has a good depth of field, esp when using my Nikon D70 at what we call prime focus - attaching the camera *directly* to the scope, with no eyepiece in between. For this you would need a T2 mount and an eyepiece nose adaptor, so the camera pretends to be a 1.25inch eyepiece. All of my bird photos with the scope are taken this way. It also has velvety smooth a rotatable Crayford focuser : Instead of repositioning your camera for various orientations, the entire focuser rotates without any loss of focus.

OK, its a totally manual set up, so Im fixed at f6.2 and have to guess the exposure time, but that comes with practise, and underexposures can often be fixed in Photoshop anyway.

Other really nice features :
* solid aluminium construction, no plastic anywhere.
* a pull out sunshade/lens hood.
* focus lock.

It is fairly well known that this is a clone of one of the famous Williams Optics scopes, and has several brands offering just about the same thing (Antares GB230, Revelation (was GB256, but no longer available), Astronomica GB295, Orion Express US$400, Astronomy Technologies Astro-Tech US$379 etc etc). Some are 480mm f6, some are 500mm f6.2. To find one, just google for 80mm semi apo.

To summarise :
A nice easy to use scope, very versatile, cheap eyepieces, easy to use as 500mm lens for DSLR, (but afocal projection only with smaller lensed digital cameras e.g. Nikon 4500). A bit heavy at about 6lbs. Generally comes with carry case, a 1.25inch or 2inch diagonal and at least one (usually 20mm) eyepiece.

Me ? I am finally happy with a small scope I can carry about and use at a moments notice (well, almost).

David Harris