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About magnification for DSO.


katdhoom
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Hello everyone.. today i bought gso10"/1250mm dob .. but my bad luck is there are unexpected changes in weather so have to wait for 2-3 days to start off..

my question is how much magnification is needed for dso's (only the popular ones) like orion nebula or m83 or andromeda etc and use of barlow is advisable or just ep??( i heard barlow deems the object)

And last one will i be able to see any dso in colour through my 10"dob or just b&w??

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Hello and welcome to the forum :smiley:

For the larger DSO's like M42 and M31 ( Andromeda Galaxy) use your lowest magnification, that is the eyepiece with the largest mm on it, ie: 25mm or 20mm. For the smaller DSO's like the Ring Nebula, once you have found it, medium magnfications are useful to increase the image scale. You won't need the barlow lens though.

DSO's do vary in size enormously so there is no real "best eyepiece" for them as a whole. A low power eyepiece is useful as a "finder" for even the small ones though.

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If you look up the size of the DSO you will get an idea of the "magnification".

M42 is usually given as 1 degree so a 1.5 degree view will fit it in nicely.

1.5 degrees means 30x, so low magnifications

M31 you will find is too large to get it all in and what happens is you see the central core only. M31 is 3 degrees across so even with a 60 degree eyepiece that is 20x or about a 60mm eyepiece on your scope.

The Pinwheel galaxy (M33) is the same as M42 (1 deg)  - Bit odd I see 2 objects in the list I am reading called Pinwheel Galaxy ?? Seems M101 is sometimes called the same, it is half a degree,

M45 is close to 2 degrees (25x-30x)

More or less everything else is smaller.

Most Messier clusters seem to make half a degree or less M7 and M44 being bigger.

This gives a list of Messier Obj and their apparent sizes. http://kenpress.com/MessierListObjects.pdf

To get a bit more then 1 degree you are looking at a 25mm BST or 30mm plossl, which useful to aid in locating DSO's - wide filed and images are brighter if smaller.

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today i bought gso10"/1250mm dob .. my question is how much magnification is needed for dso's

Congratulations on the purchase, Kat :grin:.

In my own 10" f5, I've found my most used EPs for general DSO viewing (not open clusters) have always been around that 120x mark and then backing off from that with something around 90x. The former gives an exit pupil of around 2mm and the latter around 2.8mm. If you get a 24mm , you'll have a nice finder eyepiece and one useful for open clusters and if you got yourself a decent barlow with just these 3 EPs you'd have a nice spread like this:

24mm / 12.5mm = 52x, 104x.

14mm / 7mm = 90x, 180x.

10mm / 5mm = 125x / 250x.

The lower mags would be helpful for general hunting and framing largish objects, the middle ground for globs, galaxies, planetary nebulae, lower power lunar and planetary work, the more limited higher range for Saturn, Jupiter and Lunar work and the 250x for those exceptional nights. If you got yourself some Baader solar filter, your 24mm would be also be fine for white light Sun observations.

I'd also advise you to choose these three eyepieces well, for if you do it right, you'll not have to upgrade too soon, if ever. You'll also gain the peace of mind knowing that this end of the optical/light path is about as good as it is going to get. Make sure there is sufficient field of view and comfortable eyerelief. In my own case, I saved slowly, kept an eye on the secondhand market and after a good year or so, eventually bought a 24mm Panoptic, a 14mm and 10mm Delos and a x2 TV Barlow.

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I can get hints of colour from some of the planetary nebula but not much else for DSOs in any of my scopes.

Regarding 'magnification' you may find it useful to get the Sky Safari App or similar. This lets you configure all of your various scope and eyepiece combinations and then overlays them on the view of the night sky. In this way you can get a representation of your field of view and the extent of the object or objects contained within it.

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If you want colour in DSO's, you might want to look into astrophotography or it's new incarnation: Video-astrophotography. Film and digital-imaging allow the light to build-up and this will allow the object to exhibit it's colouration. Our eyes don't do this, after some dark-adaptation has been accomplished - that's all we get. Blame the human genome.

Clear & Dark Skies,

Dave

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Expect lots of colour in stars and planets though!

I get a bit of green and purple on the Orion Nebula but not much else on the DSO front.

Paul

Should i buy any filter? Like Olll or ir cut filter or sky glow?? Will any give remarkable difference in viewing??
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Should i buy any filter? Like Olll or ir cut filter or sky glow?? Will any give remarkable difference in viewing??

In short. Yes you will probably get some filters at some stage. But I would concentrate on getting a few quality eyepieces first.

Filters can help but there are only a few objects where filters make a big big difference. Once you start getting into the wonderful world of Planetary Nebula, You'll be spending on UHC and OIII filters as a minimum.

Paul

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And last one will i be able to see any dso in colour through my 10"dob or just b&w??

This can depend on your age when referring to some objects like M42. Younger people see more colour up there than older ones. 

It's also not limited to planets as has been suggested. Many stars show colour and a good few planetary nebula display quite striking colours. even globular clusters can have colour in them. 

It's not all black n white visually :)

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Should i buy any filter? Like Olll or ir cut filter or sky glow?? Will any give remarkable difference in viewing??

Now I have an UHC filter, it's surprising how often I'm seeing this question asked.

I'm sure it was always as frequent, I'm just noticing it more. :D

Filters won't add anything to what you can already see.

They won't make the object brighter or more colourful.

What they do is remove or reduce other wavelengths of light from surrounding stars and other objects that would make the target less visible.

If it's a faint fuzzy blob, it will still be a faint fuzzy blob, just more obviously so.

With your 10" dob, I imagine more detail will then be apparent, I know I can see more of M42 with the UHC in my 8" 'scope.

The drawback, for me, on M42 is that it does take on a bit of a green tinge!

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Generally I agree with Bens assessment of the impact of filters on deep sky objects. There are some objects though where a UHC or an O-III filter really makes a significant difference - in some cases the difference between seeing a nice view and seeing virtually nothing at all. The Owl Nebula (M97) is one example of such an object and an even more impressive one is the Veil Nebula. With an O-III filter and a wide angle, low power eyepiece even my 4" scope shows much structure in the various parts of the Veil Nebula. Take the filter off and there is barely any suggesion of anything there at all. Personally I feel that this object is worth the price of the filter alone :grin:

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This can depend on your age when referring to some objects like M42. Younger people see more colour up there than older ones.

It's also not limited to planets as has been suggested. Many stars show colour and a good few planetary nebula display quite striking colours. even globular clusters can have colour in them.

It's not all black n white visually :)

Im 28 and i don't have glasses.. [emoji41] [emoji12]

Sent from my SM-G7102 using Tapatalk

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