Scope specifications..what should be given?

[Physicist13]

If you're intending to purchase a scope, what specifications would you Expect to be given so you can decide?

Also what spec would you like to be given that is not usually given???

Thanks,

Patrick

[sbooder]

Expect:

Aperture

Focal Ratio & Length

Weight

Usable Magnification

Mount fixing

Focuser type

Would Like:

Wave of mirror

Mirror Coatings

[Physicist13]

thanks in advance!!

please be as specific as possible! (eg resolution..Daw's limit?).

For all types of scope design

[skywatcher58gb]

Ther is no single answer to your question, quite a few considerations need to be taken into account to decide which scope to buy.

Budget is probably the main consideration, especially if new to astronomy, until you really are seroius then a small starter scope may be the answer.

Space considerations (no pun) if you live in a flat or have a house with plenty of street lights then a smaller travel scope to transport to a dark site may be the answer. Will astro photography be the aim, if so the an equatorial mount and refractor would be a consideration. If you are only interested in visual, a reasonable size dobsonian, say 8" may be the preffered option. Plenty to think about before spending hard earned cash.

Dave

[swamp thing]

It seems that a picture with someone standing next to the scope would give people a real idea on scale.

This could help many people when making a decision.

[GuillermoBarrancos]

It seems that a picture with someone standing next to the scope would give people a real idea on scale.

This could help many people when making a decision.

Definitely. Especially when it comes to dobs.

Because they are cheap, People too quickly go for the 12,14 or even 16 inch (because of the bigger is better / aperture Fever). Not taking the actual sheer size and weight of these Scopes into consideration.

And so end up not using it and putting it up for sale again a not too long while later.

[MrFancypants]

More detailed dimensions. I want to buy a Skywatcher 350p but I can't be certain I can get it in the trunk of my car.

[Physicist13]

Thanks!

What about things like resolution,limiting mag, focak length at different wavelengths(do u can compare APO fir eg),.... ????

[starnut]

A realistic prediction on how many times you will use in in the first 12 months

[John]

Thanks!

What about things like resolution,limiting mag, focak length at different wavelengths(do u can compare APO fir eg),.... ????

The first two of these are dependent on the observing conditions the scope is being used under so any figures given are theoretical limits only. These are often given but the actual field performance will almost always fall short through factors beyond the control of the manufacturer. Bespoke optics manufacturers may be able to provide the latter type of data but mass producers almost certainly won't because each optic set is not tested to that level.

On the relative sizes, Orion (USA) produce illustrations such as the ones below which I think give some idea:

[faulksy]

Definitely. Especially when it comes to dobs.

Because they are cheap, People too quickly go for the 12,14 or even 16 inch (because of the bigger is better / aperture Fever). Not taking the actual sheer size and weight of these Scopes into consideration.

And so end up not using it and putting it up for sale again a not too long while later.

i wouldnt say cheap, mine cost as much as my cpc 9.25, i agree on size though

[Peter Drew]

So the manufacturer states that the optics are 1/10 wave, .99 Streyl or somesuch, do you test them yourself to verify this or do you just believe them?   

[faulksy]

So the manufacturer states that the optics are 1/10 wave, .99 Streyl or somesuch, do you test them yourself to verify this or do you just believe them? 

as you say peter you have to believe them, but its like anything else including food, you just believe, but if they give you a report for the optics you could get it tested, apparently theres only 2 places in the uk that can test them a university and 00 them self's, i spoke to a telescope manufactura up north and he said hes none barry 00 to take some companys to court because they claim this and that with there optics and hes proved them wrong. so i serpose he has to be on the ball because they can do the same 

[John]

From the little I know about Zygo testing, I understand that you could do 3 tests and get 3 quite differing results depending on how the tests are conducted and the parameters used.

At the end of the day optical quality is how the scope performs under the stars.

I have a piece of paper that seems to indicate some data about a mirror in my scope that has a sticker on it with the same reference number on it thats on the piece of paper. It means little or nothing really but the scope does appear to perform well and that does make me content

[ollypenrice]

Corrected image circle and spot sizes.

Does it have a crappy cheapo Crayford which will slip, bind and sag from day one? (They'll all say 'No' but most of them are lying.)

Olly

[L8-Nite]

Expect:

Aperture

Focal Ratio & Length

Weight

Usable Magnification

Mount fixing

Focuser type

Would Like:

Wave of mirror

Mirror Coatings

This sounds like a good list to me, but I would also like to see a specification for an "optimised" optical train. In other words, the best compatible eyepieces for the scope at the time of its design. 

[Physicist13]

Thanks for responces! some good ones!

They need to be tech specs (ie where a number can be given and verified). Cannont be cross manufacturers..ie "our scope works best with xxx eyepiece"

Since, scope, mount, eyepieces, finder(?),(focuser?) tend to be bought separately, should they have separate, spectific specs.

Patrick

[Baffa]

I would say it depends on what scope it is.

If you buy a dobson you might not be interested in imaging circle while this would be highly interesting if you are looking for an astrograph.

But in general I would like to have these.

Aperture

Focal ratio/length

Focuser type (and brand i availble)

Dimensions (Could be useful for a dob or if you building an obsy)

Weight

Any info if the scope have something special, like built in flattener with mentioned correct back focus. Just an example.

Also, it should always be mentioned what kind of "extras" that comes with the scope, like dovetails, rings finders etc. I don't like when pictures doesn't match the description or what's included, kinda annoying to pick up the phone or drop an email to find out what's really included when this info should be mentioned, and showed.

While I'm at it, I think pretty much any astro dealer should improve their descriptions on accessories, scopes are usually decent, but you will never know if bolts are included when you buy a set of tube rings or what kind of back focus is needed for this flattener, for example. This is very annoying imho.

[Alien 13]

+1 for the corrected image circle and a focuser max payload would be  nice.

Alan

[John]

Of course, one of the great things about a forum like this is that you can quickly get all sorts of information about scopes from people who actually own or have owned them and are not trying to sell you one

More valuable than anything the manufacturer / vendors put out I'd suggest 

[Alien 13]

One other thing that should be in the specs is a Government Wealth Warning something like "This product will lead you down the path to poverty and to make sure you continue to spend we have included a T thread on the focuser which im most cases will be utterly useless".

Alan