Newbie Qn: About focal length and Aperture

MooEy · Post by **MooEy** » Mon Oct 13, 2003 11:59 am

i tot samuel oso dealing in skywatcher product. maybe can ask him lor, dunno he still got the manfrotto 410 tripod boh.

actually the 25mm and 10mm quite gd for starters liao la. 5mm eyepiece i think u better see it for urself b4 deciding whether to buy, usually higher power eyepiece, 7mm and below have beri little eye relief. need to put eyes beri close to the eyepiece to see, not gd for specs wearer.

as for barlow, no nid consider la, double ur eyepiece collection wor. wif a 2x barlow, 25mm become 12.5mm, 10mm become 5mm. a gd mixture liao.

~MooEy~

Post by **VinSnr** » Mon Oct 13, 2003 12:04 pm

IceAngel wrote:ooh.. so wat's the max mag. that this 90mm scope can go up to???

oh God!! i am more and more confused... is really a bad thing to have such a low stupid budget..

I would say max at around 150x. The general rule is 50x/inch, but that's only if you have a very good optics and very good sky. I prefer to use 40x/inch for better visual.

IceAngel · Post by **IceAngel** » Mon Oct 13, 2003 12:09 pm

I would say max at around 150x. The general rule is 50x/inch, but that's only if you have a very good optics and very good sky. I prefer to use 40x/inch for better visual.

if it is like tat, i really feel that with my this budget, i hardly can see anything nice

as for barlow, no nid consider la, double ur eyepiece collection wor. wif a 2x barlow, 25mm become 12.5mm, 10mm become 5mm. a gd mixture liao.

hmm.. no need to consider?? means no need to buy?? sorry.. i'm very confused and lost now..

Post by **VinSnr** » Mon Oct 13, 2003 12:17 pm

if it is like tat, i really feel that with my this budget, i hardly can see anything nice

I think you got the whole concept wrong. You don't need high mag. for most of the objects. In fact, even with my 8" scope, I hardly go above 120x unless for planets and moon.

Most objects would require 40-100x at most. Moon and planets, 120-150x is already quite spectacular if you have good optics.

MooEy · Post by **MooEy** » Mon Oct 13, 2003 12:24 pm

err.. my mistake, tot it was a 5inch. dunno y skywatcher mak gif me the impression of 5inch all the time.

anyway hor, vin snr is correct abt the 50x per inch, so it's pretty much ard 150x for the 90mm. so i think maybe u can consider the barlow as optional for the time being.

no nid worry abt nothing to see la. many of the singastro members actually own 70-90mm scopes. still can find those quite obvious dso, see the moon, few of the planets. tag along wif frens who own bigger and better scope, sometimes can peep thru their scopes and enjoy the nicer view while still owning a lightweight grab and go.

~MooEy~

kayheem · Post by **kayheem** » Mon Oct 13, 2003 12:59 pm

IceAngel wrote:i guess i should be getting a skywatcher 90mm MCT with f/13.88.. and the original EPs (10mm and 25mm are included right?), might be getting a Long Eye Relief EP of 5mm and a normal EP of 40mm... i need a long eye relief for 5mm is bcoz i afraid the hole of the EP is like a pin hole and my eyes will get :roll: :roll: and faint!!
is that enough?? hehe.. or there is something more...

*ps. if i buy this set, wo hen diu bu qi samuel.. and i feel very guilty, but i know my parents like the price to be lower.. so i also bo bian..

You are indeed fortunate to have such supportive parents. At your age, I had to borrow a 40mm bino!

Anyway, I have learnt that the lowest cost is not always the best (like medical equipment). Case in point is Orion. They are basically selling a lot of stuff made in China at prices higher than others. However, many people still buy from them because of their superior customer service, after-sales service and product knowledge.

Your dealer should be able to provide you with all the info you need to make the right choices.

Kay Heem

Post by **zong** » Mon Oct 13, 2003 1:01 pm

IceAngel, don't fall into the "hi-mag" craze, cos most of the objects we see do not need so high mag. Summore, high mag. means that you will need motor, or you will have to constantly adjust to see the images, cos they'll move very fast. I tried the moon @ like 250X on my school C8, it was moving so fast that the time i took to look and adjust was far more than the time my astro people were looking thru the scope... not to mention that i nearly went blind (cos my school no moon filter!!!)

Although my experience with observation is limited (only school scope) but 80x can give you quite some nice visuals already.

Post by **acc** » Mon Oct 13, 2003 1:13 pm

IceAngel
I agree with Zong... don't fall into the hi-mag trap. The 5mm is way too much power, and would be useful for the moon at most. The 10mm and 25mm eyepieces are good choices. Throw in a 32mm or 40mm plossol, and you would have a good range of magnifications to use with your first scope.

cheers
cc

IceAngel · Post by **IceAngel** » Mon Oct 13, 2003 1:23 pm

You are indeed fortunate to have such supportive parents.

actually.. i am thinking of buying it on my own.. coz i am saving very hard now..

WooOOooo.. ok.. now i know my mistake liao.. sorry guys.. i almost done a terrible mistake..

Thanks for the advices that you kindly make for me~~ now i am more clear about magnification thingy.. hehe... Thank you very much~~!!!!
Arigato~~

Grievous · Post by **Grievous** » Mon Oct 13, 2003 1:36 pm

Hi-mag vs. Low mag = Neverending discussion.

But given excellent skies like in Mersing, Ubin or some other offshore islands, it doesnt matter anymore. Any EP will give you nice views! Unless you'll like to challenge yourself and find those little fuzzies!

Charlie