As I get closer to my 8" scope, I'm starting to re

Alright, as I get closer to paying for the 8" Deep Space Hunter, I'm starting to reconsider the size I will need to keep me happier for longer. And as all of the astronomy folks keep saying "size does matter."

The 8" scope has a focal length of 1200mm with an aperture of 204mm (I think that's what the guy said), and the 10" has a focal length of 1250 (I have no idea what the aperture is, and how does one figure that out anyway?). My question is, is that much of a difference?? Am I going to see more stuff with only 2" of mirror difference? The cost is a hundred dollars more for those 2". Ugh. I feel very anxious about this. Any help would be appreciated.

The 10" will outperform the 8" without a doubt. Things will be a little brighter and slightly more magnification with the same eyepiece. 2" in mirror size is a lot really. 78.5" of glass with the 10" and 50.25" with the 8" scope. That is 56% more area!
Light grasp for each is,
8" Limiting magnitude=13.3 light grasp=842
10" Limiting Magnitude=13.7 light grasp=1316 difference is 474 or 56%

A 15" scope is BIG, I have one. My 12.5" scope next to it looks small. My friends 10" next to the 12.5' looks like the 12.5 next to the 15". Make sure you can transport what ever your buy. It must fit your car and your ablility to lift it.
The picture is of the 15" behind me is my friends 12.5" like my other one.
Floyd

Attached Image:

First of all, roughly 100mm = 4", so the ten incher's mirror will be around 250mm in diameter and the focal length, in inches, will be about 50". The gain in aperture will produce two things: First will be an improvement in resolution, and the second will be a significant increase in the size and weight of the scope itself. My point is, yes you will see more stuff with every significant increase in aperture (in this case a 25% increase in diameter over the 8"), but with that improvement comes a substantial tradeoff in the loss of portability. A ten inch Dob is a larger and heavier scope than an eight inch Dob, and if the bigger scope is too clumsy and difficult to use, the improvement in seeing will be wiped out by its inconvenience. It's hard to grasp the meaning of this statement until you find yourself wrestling a heavy load to and from your observing site some frosty evening. I recommend giving the matter of size the same consideration as seeing when deciding on a scope. After all, the best scope is the one you will use the most! Hope this helps!

Walter

Sarah, the 8" can keep you busy for years. If DSOs interest you get you a couple of nebula filters & they'll more than compensate for the extra 2" a 10" scope will yield. I'd go w/the 8".

Aperture for the 10" scope is 10" which equals 254mm if you convert over to metric (25.4 mm per 1 inch). The big number here is the 4.9 focal ratio (Aperture/focal length).

You will always see more with more aperture if everything else is the same. Light goes up on the area (pi*r^2) not on the diameter. However, if you are viewing from a light polluted sky, the difference will be minimal. If the 10" is too big to set up easily you will see more from the 8" because you will drag the 8" out more.

The biggest kicker, nothing will keep you happier longer. Read the posts. AM's with multiple scopes, giant Dobs, high dollar refractors are talking about wanting a different scope (See "Gear Aquisition Syndrome, Aperature Fever, ...). That's half the fun of it.

If it makes you feel better, I am checking off the Messier list and have 87 items done plus many many items not on the list. All were beautiful, some were faint, some were bright. I have an 8" Scope very similar to the one you're buying. It's an excellent scope, I'm very happy with it and of course I want a "better" one. And as soon as I get that, I will want a "better" one, and so on and so on.

Have fun. Enjoy. Focus on the things you want to see. You have an excellent scope coming.

Did I mention eye pieces?

Ed

I started off with an 8" dob and it kept me satisfied for 2 years; I replaced it with a 16" truss dob. For me more aperture is better. Unless the 10" will not fit in your vehicle, go with the the 10". A 12 year old boy in our club has a 10" Hardin dob, and he has no trouble moving it around; and he's a little skinny kid.

Eddie

As mentioned, take your time and consider a lot of factors and make comparisons between scopes of the same and different size. Although I considered the weight of my LX90 when I bought it, I didn't realize that weight and bulk are related. When you pick up a SCT on its mount, all the weight and bulk are centered around the scope tube, which makes it very hefty and clumsy to move as one piece. If I were to do it again, I'd probably buy the Celestron GPS SCT, because among other things its about 10 pounds lighter than the LX90. So compare different brands on a number of factors, including weight as well as aperture.

Did you see the sale price?

http://www.astromart.com/classifieds/details.asp?classified_id=283694

Although it's often said that aperture is everything, it really isn't. It is highly important, but it's not everything. One of the reasons that an 8" telescope is often recommended as a started scope is because it really is a great scope to start with.

An 8" scope has enough aperture to be a serious instrument. Deep sky objects start to have character and planetary resolution is quite nice. They are moderatly compact and quite easy to move around and take in the car.

My advice would be stay with the 8" scope. Use it, get used to it and learn what it does for you. After you use the scope for a while, attend a couple of star parties and look through other scopes. When YOU find there are things the 8" doesn't do for you, then you can consider the question many of us have come to - "what's next".

By that time you will have acquired a few more eyepieces and other accessories, which are quite important. You will then be making a decision on what YOU know and want instead of relying on the advice from others.

Relax - You should feel comfortable with your decision to get an 8" scope. And come to terms with the fact that regardless of the scope you own, there will always be other telescopes you will covet - just learn to use your instrument well.

Gary Weber

Hi Sarah,
My first scope was a 8"sct. I still have it always will but just recently built a 16" dob with the help of my friends here. While the dob is great I still love my 8". But here's the thing a girl never have too many scopes so purchase the scope and then after a while you will want a different one. Oh and I would not hesitate one minute to purchase from anybody that has good rating here at astromart. There are some good people here. I always check astromart first before I purchase something. Have fun and you will love the Dob.
Sonya