SW dob 6" or 8"?

[lulaz]

Hi to all!!!

I know that the biggest apperture is the best, but if I follow this I'll end up with a 20" dob... so that is not the point.

1º - how much does the 6" and the 8" weighs? do you feel like carring it outside and going to the your's street corner, even kowing that this night is supossed to be cloud (and even starts to rain)?...

2º - Is the 2" a SUPER MEGA HIPER HUGE of a difference? Do you think +2" values 250 dolars more? (remember that I live in Brazil, so that is the difference between 6" and the 8") People told me that the f/8 for the 6" dob is very, very long, so the DSOs would be very small and very dim... does the 8" solves that "dim" problem?

3º - If I buy the 6" I'll get some EPs and a good pair of binos and maybe a better finderscope or something else like a filter or something around this price... If I buy the 8", I can only pic one of these (and I'll delete the binos and finderscope from the list)...

Last things I'd like to know: Do you guys know if a lot of people buy the 6" comparing to the 8"? Do you know if those who ouns a 6" are happy with it? or they think it is trash and think they have wasted their money on nothing?

Do you know any Review of the 6" and the 8"?

Which of them would you buy and why (or why not)?

I'm considering this 3 essential points because here in Brazil, things get very, very expensive so is not something simple to say "get more 2 inches because it is just 50 dolars more..." because it isn't =\ 2" more is very expensive on a lot of ways, so I would only get one of these if the 6" is very, very bad!

thank you all!!!! And I'm sorry for these toooooo long posts with a bunch of questions!

[rabbithutch]

Hello lulaz!

I'm in the middle of the same deliberations. I have come to the conclusion that an 8" is that much better than a 6" that I will have it over the smaller one.

Understand that I don't yet own a scope; so take that into consideration wrt to my response. One assumes that you are considering a Newtonian reflector (you mentioned a 20" dob). I've decided that a dob is best for me, too. I posted here, too, and most advised that the 8" would be greater value than 6". To see why, I did the math to determine how much more area the aperture of one would have over the other. Using the formula for the area of a circle (A = r * r * pi), I determined that a 6" would have 28.27 square inches and an 8" would have 50.27 square inches. The difference is 77.8% (if I've done the math right).

Doing the math for a 10" aperture would lead one to make that choice over the 8", as well; however the size of the scope then comes into play for me. I'm nearly 70 years old (still healthy, thank God) and live in a small place. I decided that the difference in size between the 10" and the 8" would be too much. The 10" would be too heavy and too large to store or to move about in the car, whereas the difference between the 6" and the 8" didn't seem to be a limiting factor. Remember, I'm speaking of Dobsonians here, not other mounts.

Finally, while the difference in price between the 6" and the 8" is significant, the 8" is still within what I can stretch retirement income to cover. And, as this is likely to be a one and only purchase (considering age, etc.), I decided that the more aperture the better - especially as I want to see DSO's.

I'm currently shopping between the Zhumell and the Orion 8" dobs without any automation. I decided that adding automation just adds more gear to haul around (power, cables, etc). I hope to get a scope after Christmas and plan to use the dob and my iPhone with Stellarium and charts to keep it as simple as I can.

These were my considerations. Yours are quite likely very different but I'm giving you the benefit of the way I've gone about choosing. Perhaps it will help.

Good luck and clear skies.

[NGC 1502]

Hi lulaz. If you take a look at the review section on " Cloudy Nights " there are

a lot of reviews of Dobsonians of all sizes. Some of the reviews are quite old, but

they will still help to resolve your 6" or 8" question. Either is a good choice. When

I started doing astronomy in England in 1979, a 6" scope was considered large, and

an 8" out of reach for many. Things have moved on since then of course, but those

6" or 8" scopes will still give you lots of great nights under the stars.

Yes, eyepieces can get very expensive, but a lot of good observing can be done

without spending a fortune. Again, lots of reviews on " Cloudy Nights ". You don't

need many eyepieces, 3 is ok, a low power, 40-50x, medium power 100x, and a

fairly high power about 150x is good. With a 6" or 8" Dob with a 1200mm focal

length, 25mm, 12mm and 8mm eyepieces would give you that. I would not rush

to get a very high power eyepiece, over 200x, until you are sure you will use it often.

Hope this helps, best regards, Ed.

Edit : just reread your post lulaz.

A 6" tube weighs about 6 kilos, an 8" about 8 kilos. These are the tube only without

the mount. I think you would be happier with an 8" and not get some of the extras

you mention, like filters. Filters can help with some objects, but the 8" will help with

ALL objects. Good luck ! Ed.