f/? bigger better?

[draco]

hi

i now know how to work out the f/ number of a telescope but would apreciate if someone could advise me as to disadvantage/advantages of smaller/larger focal lengths.

just ordered a 150/1400 eq3 mount motorised scope that was within my budget(quite cheap) and thought apeture was king but am now beginning to wonder due to my lack of experience that maybe i should have gone for something shorter

can anyone help please. ;-)

[anthony]

Hi Draco,

Congratulations on your purchase!!!!!!

Now, that is a question with a thousand answers! (And a good question too)

That focal length will allow you decent magnification of brighter objects with detail (moon planets and star clusters) The aperture at 6" is decent aperture and will allow a good light grasp for viewing fainter things.

So there are good aspects for both brighter things and faint fuzzies. What you will learn is that no telescope covers every base and owning and using one is the best way to find out what suits you best.

I presume it is a reflector (newtonian) you have gone for and if so, study the various articles on collimation on this forum carefully to get the best out of it. If it is a "newt" you might find that the telescope tube to be quite long and so make sure that you balance it well.

Have you a link to the scope?

[Ant]

That's a 6" F9.3, not seen that ratio before.

There are a few advantages / disadvantages for that F ratio.

It'll be designed with higher magnification views of the planets and moon in mind not so orientated to DSO's. Buying eyepeices will be easier (a fast scope F5 or faster, needs a much better quality EP for a good result). Collimation will be easier to find the sweet spot.

The disadvantages are that it'll be a heavier / longer tube. It'll be more affected by wind than it's short tube cousins. It's not ideally suited for DSO's - but it will still show them OK (maybe all but the largest - Double Cluster, M31 etc).

I would think that the scope weight will be at the upper limit of the EQ3 mount.

You may find that this is actually a short tube scope, but with a barlow built into the focuser - giving the long / high focal length / ratio.

I'd be interested in seeing pictures of it. That'll tell us more.

One thing is for certain, if it's your first scope then the moon is going to blow you away

Ant

[Psychobilly]

Could it possibly a seben big boss as it sort of fits the description....

Billy...

[draco]

thankyou for your help and yes billy you are right on the money. the scope in question is the seben big boss. I would like to view dso`s but have gathered that due to thier magnitude they are difficult to find. I think that seeing my first planet will be enough of a hook to keep on putting my pennies in the piggybank for more equipment. can see jupiter out of my bedroom window most nights. Can,t wait to take a closer look. thanks again.

[Ant]

I'm pretty sure that they do have the "barlow" built into the focuser, to give the long FL with a short tube.

So it'll not be that big - certainly less than 3'

Ant

[John]

thankyou for your help and yes billy you are right on the money. the scope in question is the seben big boss. I would like to view dso`s but have gathered that due to thier magnitude they are difficult to find. I think that seeing my first planet will be enough of a hook to keep on putting my pennies in the piggybank for more equipment. can see jupiter out of my bedroom window most nights. Can,t wait to take a closer look. thanks again.

You should be able to see some of the brighter DSO's through it once you find out where they are in the sky (get a good book like "Turn Left at Orion") and Jupiter, the moon and Saturn will look nice. Don't try viewing through a window though - take the scope outside as the heat in houses plays havoc with the quality of viewing.

John

[draco]

thanks for the tip jahmanson