Advice needed - Which telescope to buy

[jessquek]

Hi bros and sis

I intend to buy a telescope but have absolutely no idea which one to buy.

my requirements:

- where we will be viewing: from the 39th floor of a hdb flat.
- what we will be viewing: golf course, greenary, buildings in the vincinity. The nearest object is around 150m away, the golf course is approx. 700-800m from us. Last but not least, is it possible to see the squirrel on a tree 15km away?
- portability: not important. intend to mount the scope on a tripod and place it in the living room.
- user-friendly and easy to maintain for a newbie like me: no need frequent adjustments or special setups or configurations.
- budget: $1k. if not realistic, pls advise the amount required.
- any shops to recommend where i can buy this equipment

thanks for reading and thanks in advance for your kind advice.

cheers!
Jessie

[weixing]

Hi,

Hi bros and sis

I intend to buy a telescope but have absolutely no idea which one to buy.

my requirements:

- where we will be viewing: from the 39th floor of a hdb flat.
- what we will be viewing: golf course, greenary, buildings in the vincinity. The nearest object is around 150m away, the golf course is approx. 700-800m from us. Last but not least, is it possible to see the squirrel on a tree 15km away?
- portability: not important. intend to mount the scope on a tripod and place it in the living room.
- budget: $1k. if not realistic, pls advise the amount required.
- any shops to recommend where i can buy this equipment

thanks for reading and thanks in advance for your kind advice.

cheers!
Jessie

Not many people come to an astronomy forum to ask for advice on telescope for terrestrial use, but since it's telescope related some of us might be able to help...

Anyway, are you going to use it for astro use? If no, what you need is a spotting scope (a type of telescope design for terrestrial use). I don't have experience in them, but many photographic shop do sell them and their price vary a lot depend on brand, name and model. May be some of us here will be able to help you.

As the question "is it possible to see the squirrel on a tree 15km away", need to do some calculation ( just wonder what is the typical length of a squirrel? :-P ) before can answer this... but most likely you won't be able to see it clearly even with very high magnification(power)... this is due to the air turbulence (cause by the heat on the ground) which will blur the image.

Have a nice day.

[MooEy]

hmm..

assuming height of squirrel = 15cm

taking 1/2 of height of squirrel as opposite, 7.5cm

adjacent is the distance, which is 15km

let S be half the angular size of squirrel

tan S = 7.5cm/15km

given a 8" telescope, maximum magnification of 400x

angular size of squirrel at 400x magnification = 400 x S x 2


i don't have a calculator with me, anyone can help with the math?

~MooEy~

[kochu]

I think you can use this calculator.

http://www.1728.org/angsize.htm

When I used this calculator assuming the squirrel is standing on its rear legs , all of 15 cm tall, it will appear 2 seconds in angularb size. Remember moon'a angular size is 1800 sec . So you will know how the squirrel will look like 15 km away.

Kochu

[shirox]

i think u can also consider a bino. with 20 or 25 times u can see km away lol

[jessquek]

good morn!

thanks to all seniors for your replies, i had a good laugh!

initially i thot of getting a good bino. but if i can haf a good scope, i may venture into stargazing in future ;p

am looking at this scope currently, need to do more research and find more info

Orion StarMax 127mm Equatorial Maksutov-Cassegrain Telescope
http://www.telescope.com/Telescopes/Cas ... p/9826.uts

[Davegn]

Just a side note. Do Check out the design of a telescope first before using it for terrestrial. Some of it might cause invented images.

[jessquek]

Hi bro Davegn

can teach me wats invented image? and what are the things i should look out for?

thanks

Just a side note. Do Check out the design of a telescope first before using it for terrestrial. Some of it might cause invented images.

[Davegn]

Hi Jessquek,

Sorry for the typo, was chatting with my boss at my work place when I made the post online.

What I mean is inverted image (Maybe right becomes left Or Up becomes down Or maybe both). It have to depends on the telescope design or how many mirrors the scope is using.

Basically there are 3 types of Telescope designs,
- Refractor
- Reflector
- Maksutov–Cassegrains

Reflector on the other hand, can’t be used for terrestrial as they may cause inverted or mirror image due to the fact that it uses mirrors to catch the light.

For Maksutov–Cassegrains, I am not quite sure. Did not own one of this before. But basically the design uses both mirrors and lens. So is like a mix in between Refractor and Reflector.

For terrestrial use, Refractors are the commonly used with a 45 degree diagonal for easier seeing.

For terrestrial wise, if I am not wrong you would not need a really big telescope.

[rlow]

Inverted image. Meaning upside-down image.

Most telescopes do not give an upright image. All spotting scopes and binos give upright or erect image. To see an upright image in a telescope, you need to use an erect-image diagonal, not the standard star diagonal. For both terrestial and astronomical use, i would suggest you get a 80mm ED doublet refractor which can cost under $1000.

I dont think it is practical or realistic to observe a squirrel at 15km away