APO Upgrade for Megrez – How To.

[Miaplacidus (Brian)]

I just replaced the lens cell on my William Optics Megrez 80mm II SD with the TMB designed Fluorite doublet that fronts the 10th anniversary Zenithstars. The WO web site says that you can upgrade the following scopes: Megrez 80 II SD, ZenithStar 80, ZenithStar 80 Short, Orion Express, Stellarvue Nighthawk 2, Revelation 80, Astronomica 80, Geoptik 80, and all the other ZS80 achromat clones . The lens alone costs US$399, but a package that includes a 2 speed microfocuser and 2" extender as well costs US$429. (You need the extender anyway.)

Anyway, I was a bit nervous to fiddle around with my scope, but it was actually dead easy. Here’s what you do.

1. Fully extend the dew shield and remove the silver retaining ring that is about 1 cm inside the front end of the dew shield.
2. Fully retract the dew shield (it retracts further now) and expose the lens cell.
3. Rotate the lens cell anticlockwise and completely unscrew it.
4. Carefully screw on the new lens cell.
5. Peel the adhesive felt strips provided and carefully attach them around the outside of the lens cell.
6. Fully extend the dew shield and replace the silver retaining ring.

I took some photos but I won’t post them unless people are interested. (I’m not sure I know how to post photos in the forums.) The scope is slightly longer, but it still fits in the backpack that the Megrez came with. You have to lose an eyepiece spot to the extender, though. The scope was previously an F6.25, now it is F6.9.

So that's the “How to” for anyone who might be interested. Don't be put off thinking it might be hard. (The “Was it worth it?” I’ll post later.)

Cheers,

Brian.

[Miaplacidus (Brian)]

Part two of this upgrade is to replace one of the focuser knobs with a WO 2-speed microfocuser which has a 10:1 ratio (really about 10.5:1, but who's counting?). This allows fine focus, and is probably only important if you are imaging, but is a cheap add on to the package (and I guess you always think about resale value). The fit and finish is typical of WO, i.e. excellent, although the finish this time is matt rather than glossy.

Once again, the process is pretty easy. William Optics website have a set of instruction on their website that you can download as a PDF (look in Manuals, under Support), and there is a helpful article on Cloudy Nights. I won't repeat all that stuff here. Just make sure you read everything carefully, and take your time. And have a clean, well-lit work area.

One thing I will mention, though, is that removing the tension screw (Allen key) was surprisingly very difficult, and when it came to the point where I was meant to insert the new, longer tensioning screw into the same hole, it wouldn't go in. I think the original screw had been cross threaded. This was a crucial event, and I was looking at having to send the telescope's focuser back to Taiwan to have it fixed. Fortunately a friend was able to re-tap the hole for me and the problem is now solved. (Thanks Joseph!)

The other thing I will mention is the excellent communication and customer service from William Optics. I sent them quite a few emails and these were always answered promptly. The information I was given was always accurate, to the point, and politely presented. And their mail service must be the fastest on the planet. Only three-four days to get to Hobart. (Once for the lens, once for the microfocuser. I ordered them separately. Don't ask. But note, WO didn't make me pay extra.)

Oh, and the 2-speed focuser works just as advertized.

On a different note, this upgrade has been for me almost cost-neutral. This modular approach to parts has allowed me to upgrade my scope with very little financial loss compared to buying a new fluorite doublet. Any other brand of scope would have meant selling what I have at a substantial loss and buying better at the new price - a substantial change-over cost. And I still have a nice SD 80 mm lens to do something with if I want. (Maybe buy someone else's and make some excellent binoculars!)

To me, it seems as though WO are always innovating, always trying to anticipate the market, always looking to satisfy a customer's emerging wants and needs.

You've just got to love that.

[JohnG (John)]

Hi Brian

Did you order direct from the WO website, reason I ask is that they state quite clearly they only deal in the US.

JohnG

[Miaplacidus (Brian)]

Good question. I had not noticed that on their website. (Until your post I was still unaware of it.)

The way this came about is that I had a problem when a spider got caught under my lens cap and made itself a web on the lens. (!) I emailed WO for advice on how to properly clean the lens. In amongst their suggested answer (distilled water, but in the end it was isopropyl alcohol that did the trick), they spontaneously offered me this new "apo-upgrade" lens for $399. Naturally it took me less than a millisecond to accept.

Only after I'd ordered it did I notice on their website that they also had a package that included the microfocuser. (Still didn't notice the USA only bit.) I emailed them again and they unhesitatingly agreed to send me that too, for the cost of the gap.

So I don't really know what the story is for regular Aussie amateurs. They did say that they were doing this because they wanted to promote the lens (I didn't even know that this was a regular offer for anyone at that stage.) Why they thought I would be in a position to promote it I've got no idea, but it seemed only right, fair and just for me to post details here on IIS. (Do you think I should have declared a conflict of interest? )

Anyway, my suggestion to you is email William Yang. Tell him you've had this funnel web get itself under your lens cap...

[GrampianStars (Rob)]

Great report Brian
let me know what the lttle "Fluorite Doublet" Megrez performs.
I'm interested in doing a conversion on the ZS80

[JohnG (John)]

Thanks Brian

If a Funnel Web gets in there, it can call it home

I will email them and see what happens, if all else fails, I have a brother living in the US of A.

JohnG

[Miaplacidus (Brian)]

Sure Robert, as soon as I get some decent weather I'll post a review. I must admit, I never found a problem with the original SD lens much at moderate magnifications, except on the moon, where CA was objectionable IMO. I have taken this new lens out recently and pointed it at the moon, and even though the OTA wasn't cooled and the air was moiling a fair bit (jet stream), I could tell straight away that the CA was going to be much better. Very thin yellow rim, no blue or purple at all (this with a 12 mm T4 Nagler), and I feel confident that under normal good seeing the CA will be insignificant or invisible. I'm hoping to push the magnification up a bit, too.

Good luck John. Maybe they'll want you to source it via a local supplier (like Frontier Optics). You could email Daniel there to see if he is getting any packages in. I hope there isn't much mark up, though. The WO price is pretty good on their web site, I think.

Cheers,

Brian.

[g__day (Matthew)]

Very nice report, the screw tapping bit didn't sound nice though! Love to see after shots of your upgraded scope.

BTW most USA only places do that not to contravene agreements with importers, but trade practices forbids an importer restricting supply of a product into Australia, so the original equipment manufacturer will always say if you wish us to place this into the hands of a internationally distributer like ship2u we will be delighted to.

[spacezebra (Petra)]

I understand that the optics that you are discussing a very much "top of the line" equipment when it comes to telescopes - but can can you explain a little more about the them?

I am curious, are they for specialised astrophotography?

Cheers Petra

[Miaplacidus (Brian)]

Hi Petra,

I'm no expert, but for both our sakes I will now go out on a limb and parade my ignorance, so that someone more knowledgable can leap in with corrections.

Refracting telescopes work by bending (i.e. refracting) light so that all light rays come to a focal point. Unfortunately, as you see when light is refracted through a prism, light of different wave lengths (colours) bend different amounts through any given medium (e.g. glass). Hence the rainbow. In telescopes this is called Chromatic Aberration (CA).

ACHROMATIC (Latin: Without colour) lenses are designed to correct for this to a limited extent, and by semi-agreed definition they ought to bring two separate wavelengths (colours) to the same focal point. Most cheap refractors are achromats. CA isn't totally eliminated, and is most obvious on bright objects like the moon (where most typically you can see a rim of blue on one side and yellow on the other).

APOCHROMATIC lenses (Latin: really and truly without colour, and this time we mean it) are semi-defined to mean bringing three separate wavelengths of light to the same focal point. According to some, they are also meant to correct for another sort of aberration called spherochromaticism (I'm going down for the third time now. Please, someone save me...)

True apochromatic lenses, so I believe, require at least three lenses in the light path, and sometimes more (e.g. Petzval design). But, if you use glasses of EXTRA-LOW DISPERSION, you can come close with just two lenses. (And you have the advantage of not losing contrast with all those air-glass interfaces.) Fluorite, which is actually a crystal that can be grown in a laboratory, is one of the best ED materials around, and the new fluorite doublet lens that we are referring to uses it to give apochromatic views (for real world situations, anyway). Or at least, that's what we're all hoping.

Of course, you can avoid all this by using a mirror! (It's right about now that the apochromatic aficionados will leap in and start yet another refractor vs reflector battleground.)

Is that what you were after?

Cheers,

Brian.

[spacezebra (Petra)]

Thankyou Brian for the explanation.

I had a look at the WO site to get a look at what you are discussing, very interesting pieces of equipment.

I must admit that I had a look the specs on the scopes in particular the OTA's and they are considerably shorter - in comparison to my scope - so the superior optics are the main selling point (yes) - or am I missing the point. I must admit to get my head around it I compare size of the scopes you are taking about to Bino's eg 50mm (portability) (wow they fit in a back pack!), bear with me here, but with superior optics, and the ability to change eyepieces, focus etc and photography. The finders look even smaller.

Cheers Petra

[Miaplacidus (Brian)]

No worries, Petra. A nice, big scope like yours is, well, nice. And big. Lots of light gathering potential, great for faint DSOs, pretty much perfect for everything. Everyone needs a light bucket.

But a nice refractor is certainly more portable. And easy on your back. And it doesn't have to cool down, so it's great for quick peaks. When I'm at my club, and we're all looking at the sky trying to decide if it's is worthwhile setting up our respective scopes, and everyone else decides not to bother, I find that they all start looking at me. It's like this: a short tube refractor is astronomy's urban assault rifle. Even a couple of holes in the clouds mean you've still got a chance to get in, kill a couple of double stars, dismember a DSO, and still get out before it all goes to hell. (Your GOTO owners are automatically out of the running because they can't find any alignment stars. Your bazooka dob masters can't be bothered straining their backs for 15 minutes of observing.)

Supposedly a good apo with fine optics can crank up the magnification to a surprising extent (i.e. unlike binoculars). And the apo loyalists argue that the quality of the image is superior to that produced by reflectors. (Big topic; I won't buy into that.) Certainly there are no diffractions spikes. Stars look like stars (so they say). And the wide fields are truly amazing. And you can use it during the day. And yes, it's good for astrophotography.

But I'm still glad I have a dob.

[spacezebra (Petra)]

Many thanks

I truly appreaciate the time you have taken to explain this to me - I will watch your posts with great interest.

Thanks again

Cheers Petra