View Full Version : My dilemma: 8" or 10" LX90

2006-Apr-08, 05:45 AM
So, Discover Channel Store is running a promotion this weekend for double passport points (instead of spending $150 to get a $10 gift cert you only need to spend $75) and I've decided I want to get an LX90. Problem is, the difference between the 10" LX90 GPS (http://shopping.discovery.com/product-60251.html) and the 8" LX90 (no GPS) (http://shopping.discovery.com/product-56925.html) is about $750.

Now, I know the mantra is "aperature, aperature, aperature, get as much aperature as you can afford" but are two inches and GPS really worth that much extra green?

Opinions and comments, please!

EDIT: Another thing to consider: I'm pretty sure a 10" is all I can realistically afford and handle, and it would hopefully be the last scope I buy for the next decade at least. But if I go with the 8" I know I'm going to get the bug again sooner or later.

2006-Apr-08, 06:02 AM
I would go with the 10 inch. Me and my dad recently upgraded to a 10 inch RCX400, and it gives FAR better results than any 8" we have looked through (although part of that may be the RCX's optics). Many more stars are visible, the resolution seems a little clearer, and the alignment is very easy with the GPS. I would go 10".

2006-Apr-08, 05:01 PM
Do note that a 10 inch SCT is heavier and somewhat harder to set up. So depending on your upper body strength, and how far you have to carry your scope, and whether you observe alone or if you always have someone to help you set up, may be things that might influence your decision.

The difference in light gathering between an 8 and a 10 is noticeable, but not amazing-wow-socksrollupanddown difference.

2006-Apr-08, 08:22 PM
Yeah, the weight limitation is what will probably keep me from getting anything bigger than a ten inch.

The point, however, is somewhat moot, as I decided to wait until they have another double point weekend and I have enough cash stashed away to make me feel comfy getting the ten. As it was now I was going to have to go to the bank to withdraw cash and have the store order it for me because I couldn't order it online because my card doesn't go high enough. (A situation that will be remedied shortly...)

Thanks for your comments, though, as they have convinced me to wait for the 10".

2006-Apr-08, 09:10 PM
The ten is a good choice if the weight and storage space are not issues. Remember that (apart from the size of the central obstruction in mirror designs) light-gather capacity scales as a function of the diameter of the primary.

8x8=64 and 10x10=100, meaning that you will get over a 50% improvement in light gathering capacity in a 10" vs an 8". Will the difference impress the heck out of you? Perhaps not, until you are hunting down some faint fuzzies and you notice that you can easily find some that your observing partner with an 8" cannot seem to detect. Design and execution make a big difference, too. I've been able to locate and sketch or photograph low-contrast objects with my 6" Astro-Physics f:8 that my buddy couldn't even detect in his Celestron C8. Oh, to have a BIG apochromat!

2006-Apr-09, 02:41 AM
The price difference probably comes from the GPS-controlled GoTo-system, less from the 2" difference in aperture.

GoTo is very comfortable, but it cuts short your learning of the sky - you don't have to find things yourself anymore, so you just dial in M104, and there it is. In my opinion (yes, call me romantic), that also cuts down a lot of the observing fun. I remember shivers running down my spine when I first found M57, the ring nebula - I was on my own, with an 8".

Provided you can handle a 10" and have the money, you should go for it - but maybe you should take one without GoTo. Saves a lot of money and keeps the hunting instinct awake :)

2006-Apr-09, 05:32 AM
Additionally, regardless of which scope I buy, I'll be too pooor for a while to buy an LX EQ mount. Would it be a bad idea to not extend one of the tripod legs fully and have the whole shebang sit at the proper angle for a polar alignment?

Moreover, I have only an ETX-125 at the moment. If I'm looking for a drastic difference, will I see one with the 8", or do I need to go to the 10?

2006-Apr-09, 05:59 AM
You'll see a significant difference going to either, although (especially for faint, deep space items) the 10" will have a greater difference, and it would be a noticeable improvement over the 8". I would not attempt to get it on the equatorial angle with the tripod legs - you're asking for it to get out of balance there, or for something to happen to it. What do you primarily enjoy looking at? Me and my dad enjoy looking for faint, deep sky objects, so aperture rules. However, if all you want is planetary and the brighter deep sky stuff (like M13 for example), and you won't be peering into the eyepiece trying to discern a nebula barely within your scope's grasp, then there won't be as much of a difference. It will still be there, but you won't notice it as much as you would if you were attempting to go for the faintest objects.

2006-Apr-09, 02:49 PM
So, Discover Channel Store is running a promotion this weekend for double passport points (instead of spending $150 to get a $10 gift cert you only need to spend $75) and I've decided I want to get an LX90. Problem is, the difference between the 10" LX90 GPS (http://shopping.discovery.com/product-60251.html) and the 8" LX90 (no GPS) (http://shopping.discovery.com/product-56925.html) is about $750.Orion sells an 11" SC on a much heavier motorized German equatorial mount (proper polar alignment, so no image rotation if you want to take pictures) for $2499. Don't pay money for GoTo capability - half the fun of astronomy is learning where things are in the sky and learning to navigate there. No matter how many things are in the GoTo computer's database, they can never program in all the nice little asterisms, condensations, and faint fuzzies that you will be able to find with an 11" scope. With your eyes, brain, and some good charts, you will build up the best database you can have - YOUR database. It helps if you take notes in a journal as you observe things - you'll be surprised how much information you can glean from that in later years. As you become a more experienced observer, you will see that objects that might have been problematic for you in the early years are a snap to locate and observe later on.