dunno abt 50% rule. from what i know, one magnitude = 2.519x dimmer. and the eyes cannot tell the difference between half a magnitude.
so if i have my 3 inch(80mm) scope now, and i compare it to a 8inch(roughly 203mm) scope. i would take 203^2/80^2 and that is 6.44x more light gathering power for the 8inch sct. so i take 2.519^x = 6.44 i could work out how many magnitude more i can see. doing the maths i get an answer around 2, which means a 8inch scope can see 2 magnitude more than my 3 inch toy scope, quite a big leap.
so now if i have a 8inch scope, and i compare it to a 12.5inch dob, using the same steps as above, i would get a value of abt 1 magnitude. an increase of 4.5inch and i only get 1 magnitude more >.<
so whenever u see those advertisement, saying that this scope can gather 150% more light than the slighty smaller aperture scope in the same family, u can safely ignore that, since u would barely see any difference.
~MooEy~
Is Bigger Always Better?
- chris shaw
- Posts: 97
- Joined: Mon Oct 06, 2003 5:16 pm
- Location: Newton area
- weixing
- Super Moderator
- Posts: 4708
- Joined: Wed Oct 01, 2003 12:22 am
- Favourite scope: Vixen R200SS & Celestron 6" F5 Achro Refractor
- Location: (Tampines) Earth of Solar System in Orion Arm of Milky Way Galaxy in Local Group Galaxies Cluster
Hi,
A magnitude seem small, but (base on Tycho Catalog projection) the number of star from magnitude +13.50 to +14.49 are around 29,457,184 and the number of star from magnitude +14.50 to +15.49 are around 85,689,537... Will miss quite a lot of star by only a magnitude...
Also, you will see more detail even the aperture difference are only a few inches (I think 1 inch won't make any practical difference, but a few will)...
A magnitude seem small, but (base on Tycho Catalog projection) the number of star from magnitude +13.50 to +14.49 are around 29,457,184 and the number of star from magnitude +14.50 to +15.49 are around 85,689,537... Will miss quite a lot of star by only a magnitude...
Also, you will see more detail even the aperture difference are only a few inches (I think 1 inch won't make any practical difference, but a few will)...
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance."
- harlequin2902
- Posts: 744
- Joined: Tue Sep 30, 2003 11:04 am
- Location: Singapore, Sengkang
Well, one sure way of bringing out that "appreciable difference" in an instant would be to set up both your scopes side by side and have them point to a large and relatively rich globular cluster - at this time of the year, I think M22 is still available. Though you won't really see a huge difference in visual brightness of the cluster in the large vs small, at higher magnifications (100+ and beyond), you'll see that the larger scope will do a much better job at partially resolving some of the individual stars within the cluster, while all you see in the smaller scope is just a fuzzy patch of light.I think there WOULD be appreciable difference between the ETX 125 and LX200 7 inch Mak but I would have to wait until my order arrives to compare....
Samuel Ng