bargain achromats

janoskiss (Steve H) · #1 08-08-2005, 10:29 AM

Anyone after an achromat should check out AOE's current prices.

I was just browsing for a mount for my ED80 when I spotted the new specials on refractors. Ranging from 80mm on AZ3 for $249 to 102mm on EQ5 for $599.

I'm almost tempted to scrape together enough for yet another scope. Would the 4" f10 make a good planetary scope? I could also use the mount & tube rings with my ED80.

elusiver · #2 08-08-2005, 11:05 AM

how many scopes do u have jano.. didn't u just get the ED?? will it ever be enough

el

ving (David) · #3 08-08-2005, 11:08 AM

been looking at them too...
the price of the 102mm barely covers the mount!

wonder what the quality is like?

janoskiss (Steve H) · #4 08-08-2005, 01:40 PM

That was my thinking exactly David. What I'm really after is a half decent mount + tube rings + mount plate for my ED80. With the 102mm package I'd be pretty much getting a free scope. Even if I don't like the scope and decide to sell the OTA + finder + diagonal + EPs real cheap, say $200 total, I still would have gotten a good deal.

cahullian · #5 08-08-2005, 01:49 PM

with the 102 mm the tri pod is alumunium not steel but it looks very interesting. Might think about one for my trip south of the border later in the year.

cahullian · #6 08-08-2005, 02:05 PM

would an EQ aluminium mount be any good?
Does anyone own one?

ballaratdragons (Ken) · #7 08-08-2005, 04:39 PM

Steve, you could piggy-back mount the spare refractor onto one of your other scopes!

ballaratdragons (Ken) · #8 08-08-2005, 04:47 PM

What is the difference between these 2?
I know nothing about refractors. I've never had one. But I am interested in one of these!!! They are on the site Steve provided above.

AOE90S 90x600mm F6.6 Price...$299.00

AOE90L 90x900mm F10 Price...$299.00

Is one better for deep space or what?

ving (David) · #9 08-08-2005, 05:10 PM

focal length ken, the 900mm will give more magnification but like adding a brlow to your scope it makes the image dimmer and narrower too. the 600mm will give a brighter image and wider, but the trade off is less magnification.

the mounts are probably interchangable even tho the f6.6 is shown on a az mount and the f10 on an eq.

so yeah the 600mm is better for wider field and deep space i'd assume

ballaratdragons (Ken) · #10 08-08-2005, 05:15 PM

Ta David,

I am thinking of one for my boys (and me). If the f6.6 is a very good scope I would like to get them (us) one.

Unless someone explains to me why the f10 would be better.

And it says you get to pick which mount you want. I think EQ!

janoskiss (Steve H) · #11 08-08-2005, 05:23 PM

The 102mm is a bit too long to piggyback on the Dob, but the short tube 80 or 90mm would make a great finder. I've been meaning to buy a right angle finder anyway. Just got to work out what's the most cost effective option. The ED80 has an oversized 4" OTA, so the tube rings of the smaller scopes would not fit it.

Got a quote for EQ5 + tube rings from AOE: $548. So that's just $51 extra for the 4" f/10 + accessories. I read several reviews about 100-105mm f10 Chinese achromats, and the general impression I got is that this sort of scope at best could equal the ED80 on some targets and would be inferior on others. I wonder what the resale value of the 102mm OTA would be.

janoskiss (Steve H) · #12 08-08-2005, 05:38 PM

Ken, the main reason f10 is better because flaws inherent in the design of these scopes are worse at shorter focal lengths. All else being equal, spherical and chromatic aberrations get worse as the f-number goes down. This becomes more important at high magnifications, i.e., planets.

BTW, at the same magnification both the short and long tube scopes will be just as bright as each another. It's just that you'll need different EPs to achieve the same magnification.

One thing to consider is just how wide you want to go. With a 30mm PL (which is probably the longest FL EP you'd use), the 90x600 will give you 20x, i.e. about 2.5 degree FOV, and the 90x900 will do 30x or about 1.7 degrees. So at its lowest magnification you'd get away with not having a finder on the short tube, but you'd need one with the f10.

ballaratdragons (Ken) · #13 08-08-2005, 05:52 PM

So a good compromise between the 2 f ratios might be:

AOE80S 80x600mm F7.5 Price...$249.00

Yes or No?

janoskiss (Steve H) · #14 08-08-2005, 06:00 PM

No. Mask down the 90mm to 80mm and you would have turned the 90mm f6.7 into an 80mm f7.5. For an extra $50 the increased aperture of the 90mm is probably worth it.

ballaratdragons (Ken) · #15 08-08-2005, 06:04 PM

Sounds to me that the: AOE90L 90x900mm F10 Price...$299.00 is the way to go then.

And get it on the EQ mount. It is an: EQ-3A Equatorial. Hope they are OK for that size and length of scope.

janoskiss (Steve H) · #16 08-08-2005, 06:20 PM

EQ-3A looks identical to what I have, and what I have is a wobbly, flimsy and badly designed mount. I'd say the AZ3 will probably be a lot more stable & easier to use.

janoskiss (Steve H) · #17 08-08-2005, 06:31 PM

Ken, another variable in the equation: Coatings. See below.

Quote:

the 80mm believe it or not has fully multicoated lenses, and very sturdy construction. The 90mm is the same except it has the same coatings as most of the other good quality refractors sold. Our 102mm and above refractors are made by the same manufacturer as Meade so they are good quality.

--- in email from Dan at AOE

I'd say contact AOE by email or phone and discuss the pros & cons with them. I've found them to be very good at providing information, and willing to patiently answer question after question.

ving (David) · #18 08-08-2005, 08:37 PM

Quote:

Originally Posted by ballaratdragons

Ta David,

I am thinking of one for my boys (and me). If the f6.6 is a very good scope I would like to get them (us) one.

Unless someone explains to me why the f10 would be better.

And it says you get to pick which mount you want. I think EQ!

yeah i was thinking of getting one at one stage for beckie (me) because it would be a great starting point for her (me).

of course she isnt interested so I'd have to have it

and of course cheryl say "you dont need another scope david!!!"

wouldnt buy one behind her back of course... I'd do it infront of her back

ballaratdragons (Ken) · #19 08-08-2005, 08:48 PM

David, to save arguments with you wife, I'll go you halves in one.

I get it for the first 5 years and then you get it for the next 5.

Starkler (Geoff) · #20 08-08-2005, 08:52 PM

My thoughts are that anyone with a dob here looking for a second scope may be better served by a short focal length refractor for rich field viewing. The longer f10 types are closer to the focal length of the dobs and wont do anything better than what your dob does, and be considerably dimmer and shakier.
A long fl refractor on an eq3 with aluminum legs will be diabolical.