Deep Sky Magnification

[Aled B]

Hi. i have recently purchased my first scope and trying to understand location of stars and galaxies. if i were to look for e.g whirlpool galaxy. what magnification will i be requiring to be able to seek this?

 

Look forward to seeing your comments. Thanks

[fifeskies]

Aled ,

Welcome to the hobby.

 

 

It will be necessary to know what scope you have before anyone can give you a definitive answer.

It will also depend on your location (Bortle rating for your sky) , you need to give this in order to be able to help you properly

You can look up your Bortle value here   http://clearoutside.com/forecast/50.7/-3.52   just input your location (it defaults to the FLO location.)

Just let us know the Bortle value , no need to post your actual location. Higher values are poorer skies.

(you need good dark skies for the dimmest of the Deep Space Objects like galaxies (DSO).

 

generally you want low magnification to find most of the dim DSO

 

I use 40x or 50 x with a 6 inch refractor and an 8 inch Newtonian in order to find the fainter fuzzies , but I have reasonably good Bortle 4 sky here.

 

With smaller scopes you probably will need to start on lower magnifications than this to find the fainter objects , if you magnify them up too far they get spread out and too dim to see.

 

 

You are unlikely to see eg whirlpool galaxy if you have a very small aperture scope and/or are in Bortle 6 or above skies. , though often a small change in location (not allowed just now of course) will enable you to take your scope out to a site with much darker skies.

 

M51 the whirlpool is dimmer than the (relatively) nearby M81 which is easier to find and has a companion galaxy M82 which is smaller but can often be seen in the same view with low magnification eyepieces.

 

 

Edited May 4, 2020 by fifeskies

[Aled B]

thanks for commenting. bortle level 4 i also have here  scope is skywatcher 102R 4.9f 

.   i have standard 10mm and 25mm wide eye. recently purchased 7mm-21mm stop zoom and barlow x3 lense.

 

 

 

 

Edited May 4, 2020 by Aled B

[fifeskies]

You are lucky enough to have good dark skies and that is a great first telescope.

Use the 20mm eyepiece (20x mag) to look and you will certainly find M81 and on a clear night M51 should be visible.

 

Use stellarium (free) or a free phone app to help locate the area of sky they are in , both these are well placed at the moment being high overhead where there is less distortion and the sky tends to be darker at this time of year.

 

the supplied eyepieces are very much starter ones and benefit from upgrading.

Your zoom is good for brighter objects like the moon and globular clusters but less suited to DSO.

 

When I started out I upgraded my supplied 25mm , probably the same one you have , to a better 25mm.

I got a Celestron X-cel 25mm second hand and it made a big improvement especially looking for galaxies, these are available fairly often on here or other similar sites. 

 

 

With that telescope you have do not be tempted by anything much over a 30mm eyepiece as the exit pupil will be too wide for most eyes and you will be wasting light.

I use a premium 30mm eyepiece now for locating galaxies.

 

 

 

 

[miguel87]

Yep I would say around 30-50x for finding. Remember that these things are not small really, just dim.

I use 31x mag for scanning for galaxies then maybe anywhere between 50x and 111x for viewing, depending on the object.

Enjoy the skies!

Edited May 4, 2020 by miguel87

[fifeskies]

You have good dark sky and a very capable scope that should let you see the DSO like M51 and M81 as long as you have a nice clear steady night.

Your 25mm eyepiece will give you 20x which is the one to use for finding the galaxies.

 

Both the 10mm and the 25mm are "starter" eyepieces and you would benefit from upgrading these.

 

The zoom will be good for brighter targets like moon and some of the star clusters but is less suited to DSO.

 

 

 

[Aled B]

great advice i appreciate all of this. with the barlow x3 lense if ive understood this will change the magnification by a 1/3 so with the 25mm it will act as a 8mm? this will help me to look further to the deep sky right?

[fifeskies]

the barlow will indeed effectively change your 25mm to an 8mm ,

but this will dim down your galaxies by 9 times as well

(3x wide x 3 times height so spread out 9 times thinner)

 

be good for the moon though which has plenty brightness to spare

 

[miguel87]

1 minute ago, Aled B said:

great advice i appreciate all of this. with the barlow x3 lense if ive understood this will change the magnification by a 1/3 so with the 25mm it will act as a 8mm? this will help me to look further to the deep sky right?

No, not further into the sky. In fact, if you are viewing something really distant and faint I would stay under 100x magnification.

Magnification just tries to make the image bigger but dimmer.

So your barlow will make your image bigger but dimmer. You can only afford to go high mag on bright objects like the moon, planets etc.

I never use more than about 150x on deep sky. Whereas Jupiter might take 333x on a good night.

[miguel87]

What allows you to see 'further'is gathering more light (aperture) not magnification.

I have a microscope that can acheive 500x, much higher than my telescope. But my microscope is useless for deep sky observing 😂

[Aled B]

im still trying to get the calculation of mag strength in my system. so 1000x is the lense x focus? so 20mm x 4.9f in my instance?

[fifeskies]

As miguuel87 says if you want to chase deeper galaxies you will need to be buying a larger aperture telescope

but get a feel for things with your perfectly good first scope,

 

(beware the aperture fever though , enjoy the scope you have it will let you see plenty before changing to another ……….. says the person who went from 90mm to 150mm to 200mm to 250mm within a year …. all second hand , they were bargains ….. honest)

 

[Aled B]

ahh ok .. ye so what would you say my limits in regards of objects i should be observing then? is there an app/book which will help me see how deep these galaxies are and what magnification would be necessery?? 

 

and im afraid of having same issues  can't say no to bargain.

15 minutes ago, miguel87 said:

No, not further into the sky. In fact, if you are viewing something really distant and faint I would stay under 100x magnification.

Magnification just tries to make the image bigger but dimmer.

So your barlow will make your image bigger but dimmer. You can only afford to go high mag on bright objects like the moon, planets etc.

I never use more than about 150x on deep sky. Whereas Jupiter might take 333x on a good night.

 

[fifeskies]

magnification is obtained by dividing your telescope focal length  (yours is 500mm) , by the eyepiece focal length.

 

so for your 25mm eyepiece      mag =    500/25     or x 20

for the 10mm                            mag =    500/10    or  x 50

 

 

(corrected my maths error 500/10 = 100 ??? in what galaxy is that then)

Edited May 4, 2020 by fifeskies

[Stu]

Much depends on the size of the object don’t forget. The Andromeda Galaxy is huge in the sky (approx 6 moon widths long or 3 degrees. This needs lowest power and a wide field to fit it in. Conversely, something like M57 the Ring Nebula is tiny so needs much higher power to see it properly, over x100 most likely. So the answer depends on the object, as well as the scope and the conditions.

[fifeskies]

for DSO you need to get used at how to look at them as well

looking directly at them middle of vision you are less sensitive

by looking slightly off centre (averted vision) you can see them better , just needs a bit of practise

[Aled B]

is there a way of knowing what magnification you would require? e.g distance by magnification?

[Mr niall]

The job of a telescope (when used in astronomy) is not to magnify things but to collect more light than the human eye. The magnification is not, therefore, the most important consideration.

To work out magnification you only need to know the focal length of your telescope (i.e) how long it is. If your scope is a 102 f4.9 then it has a focal length of 500mm.

So a 25mm eyepiece will give you 20x

A 10mm eyepiece will give you 50x

and so on...

For looking for galaxies and fainter stuff, the aim is not really to magnify them per se; because they aren't really that small (comparatively speaking). A magnification of 20-50x will be ample for most stuff. Like I said above - the aim of the scope is to make the invisible visible - not to make the very small much bigger. 

That's why "bigger" telescopes are better in an absolute capacity - as they collect more light. Broadly speaking, the bigger the aperture of the scope, the more light it collects, and the "further and fainter" it can see. Adding more magnification will never make something invisible suddenly become visible.

[Nerf_Caching]

1 minute ago, Aled B said:

im still trying to get the calculation of mag strength in my system. so 1000x is the lense x focus? so 20mm x 4.9f in my instance?

Hi! I think you are under the impression that the larger the magnification, the 'deeper' into space you can see and the more detail you can see in deep sky objects. However, that is not necessarily the case for dim galaxies and nebulae. You see, the problem with these objects is not that they are too far away to see, but because they are too dim. Take the Andromeda Galaxy for example. If it was bright enough for us to see in its entirety with the naked eye, it would span an area the size of six full moons. Unfortunately it is too dim to be seen like this even though it is quite large from our perspective. That's why we need the extra light-gathering capability of a telescope to see deep sky objects better. This brings me to the topic of magnification. Imagine a beautiful image of some distant mountains on your computer screen. Let's say you want to crop the image to take a closer look at the distant mountains. At a certain point though you will begin to see blurring and pixelation. That's what magnification is. Just as cropping the image won't bring you 'deeper' into the photo, so does magnification. When you magnify something, you are spreading out the already-gathered light over a wider area making the view dimmer and blurrier at a certain point(That's the maximum useful magnification of the scope). As a result, you should use LOW magnification for dim deep-sky objects to concentrate the light. Attached is my sketch of a globular cluster at 39x magnification which is quite low. I hope you get the idea:)

[fifeskies]

there are a lot of factors to consider and what works well one night may be hopeless another

start on low mag to find it and try higher mag until its getting less good , often x 100 is about the best you can hope for unless its a very good night.

this is why it helps to have a range of eyepieces covering different mag

 

and what works well for 1 object may not be as good for another

[John]

9 minutes ago, Aled B said:

is there a way of knowing what magnification you would require? e.g distance by magnification?

No, it does not work like that.

Generally deep sky objects are observed at low to medium magnifications. Some deep sky objects are very large in the sky so very low magnifications are used. Some are very tiny so higher powers work on those.

How "deep" you can see depends really on the darkness of your skies and the aperture of your scope.

 

[Aled B]

im really thankfull for all comments and learning all the time. as nerf_catching said maybe my thoughts were all wrong. 

if im honest i need to be more patient and enjoy the learning and understanding which if why forums like these are so helpful for novices like me self. 

[Aled B]

12 minutes ago, fifeskies said:

there are a lot of factors to consider and what works well one night may be hopeless another

start on low mag to find it and try higher mag until its getting less good , often x 100 is about the best you can hope for unless its a very good night.

this is why it helps to have a range of eyepieces covering different mag

 

and what works well for 1 object may not be as good for another

may i give and example the  m51 whirlpool galaxy is south of the vega star and i can see the two stars where it is located but not been able to see it. as i have a x62.5 as best without the barlow is it a case of skies not clear enough or being in patient or any other factors?

[fifeskies]

Nothing beats going out and just seeing what you can do with the scope you have.

Take the time to get to know how it all works and there are some good summer targets to enjoy.

 

 

It is of course summer with short darkness and bright night skies  (I am now in twilight until august ends)

Winter is always a joy when Orion comes back as there is so much to see in that area of the sky , not the least of which is the Orion nebula and its close companions.

[Nerf_Caching]

2 minutes ago, Aled B said:

im really thankfull for all comments and learning all the time. as nerf_catching said maybe my thoughts were all wrong. 

if im honest i need to be more patient and enjoy the learning and understanding which if why forums like these are so helpful for novices like me self. 

By the way, the formula for calculating magnification is focal length of telescope divided by focal length of eyepiece(eg 10mm eyepiece divided by 900mm focal length telescope gives 90x magnification). Also the f/ratio can be calculated by dividing focal length of telescope by aperture of telescope(eg 900mm telescope divided by its 70mm aperture gives F/13). The latter formula pertains more to astrophotography though so you shouldn't worry about it; it's just for your information:)