Posts Made By: David Colton

Given that you are such a diehard Televue aficionado, I'm surprised you didn't go for the Gibraltor. Either way, I think the TV102 works great on an Alt-Az.

I wonder what, if any advantage there is to having a smaller objective scope than your ST80. All of the aforementioned scopes have short focal lengths and are therefore optimized for rich field observing rather than viewing the moon and planets, so whether the scope is an achro, semi-APO, or APO shouldn't make a profound difference. Some differences, such as contrast, may not warrant an additional $200 to $600 in cost and may, in part literally be "in the eye of the beholder."

I think you will find that us TV102 owners are very biased; like AstroPhysics and Takashi owners, we think our scopes are the cream of the crop. So with that bias in mind, if you can find a used TV102 for $1500 (and I haven't seen any at that price) go for it. You won't be disappointed.

Since a long focal length will reduce, but not entirely eliminate CA, does anyone manufacture 70mm or 80mm lenses with a long focal length? If so, how long would an f15 70mm scope be and how portable do you think it might be?

Also, because Itz is apparently looking for a mid-range priced APO, wouldn't the Orion 80mm and some of William Optics semi-apos fit the bill?

From your questions it seems like you're looking for an affordable refractor with good color correction. From the reviews that I have read, the Orion 100mm sounds like it would fit the bill. No, its not an AP, Televue, Tak, or Tec, but it appears to be (in the upper limits of) your price range.

Most importantly, consider HOW you plan to use the telescope. Will you be doing a lot of "all-nighters" or do you tend to be a casual viewer going out for an hour or two? If you plan to have lengthy viewing sessions, then a scope that takes a few minutes to set up and break down is not an issue. However, if you are a more casual observer than you may be more interested in portability. So the size and weight of the scope will matter.

When I was deciding on which scope to buy, I made a list of the pros and cons of each one - and then ultimately bought both of them! However, I've found that my viewing habits have helped in deciding which one to keep and which to sell (the LX90 is now posted in the classifieds).

I doubt that you will be satisfied with a "semi-apo" or a chromacor corrected achromat as you'll always wonder if you should have saved just a bit more for an APO. So, since you're taking the time trying to decide, save some more money and get the scope you really want.

Something to consider with a GOTO scope, such as the ETX or LX series is your location. I've found that my LX90 is not well suited to my yard, where I do most of my viewing, because of tall trees. If I have to move the scope then I have to re-align.

Another consideration is weight. the LX90 is not excessively heavy, but it's cumbersome to lift and move. That wouldn't be the case with the ETX series, but of course you're giving up aperture compared to an 8" or 10" Dob. In other words, there's a lot to consider when purchasing a scope so don't rush into it.

I think www.focuser.com carries a focuser to fit your scope. They could probably tell you how to remove and replace the existing unit.

Going back to your original question, in addition to differences in the lens, there are differences in the overall construction; what some refer to as "fit and finish." For example, I understand that the higher end APO's are made of a heavy spun metal, whereas lower cost versions may be made with a welded tube. The focusers also tend to be different with the higher end versions now including fine focusing mechanisms as a standard feature. It's clear however, that there are now more choices in the marketplace for 4" APO's and the differences in viewing may be due as much to the observer's eyesight and nighttime viewing conditions as it is due to the scope.

If they work as advertised (and that's a BIG IF), you may want to consider mounting a Celestron Sky Scout on the OTA. That will work like DSC without the need for encoders and at $400, cost less than DSC and encoders. And you won't need to go through a two or three star alignment process.

As I mentioned in a reply to another post, if it works as promised, Celestron's new Sky Scout (due out in April) may be an affordable alternative to DSC, as it doesn't require encoders. That means you can move it from scope to scope as you acquire new hardware. However, I wouldn't buy one immediately as I'm sure the first batch will have bugs that need to be ironed out. So read the literature on the unit and start saving your money.