Is Bigger Always Better?

MooEy · Post by **MooEy** » Fri Oct 17, 2003 11:41 am

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~

chris shaw · Post by **chris shaw** » Fri Oct 17, 2003 12:10 pm

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....

I would have ordered an 8 inch Mak but Meade doesn't make any and I wanted the GPS capability!

Chris

Post by **weixing** » Fri Oct 17, 2003 12:57 pm

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)...

harlequin2902 · Post by **harlequin2902** » Fri Oct 17, 2003 2:34 pm

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....

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.