Hi everybody,
I posted this thread in Equipment forum, but I also think that this forum is the right place. I am wondering what is the optimum magnification for viewing deep sky objects, especially galaxies and planetary nebula?
Is 200X sufficient? I asked because I am considering an eyepiece that yield 200X and my viewing preferrence is DSO.
Thanks.
Just my opinion, It really depends on what you want to look at that is
deep sky. I very rarely (that I can remember) using 200x on DSO's unless
maybe a faint small globs. Using a 10mm @ 120x in my scope singular
objects (but not always the case) using 20mm @ 60x for larger nebula
and galaxy clusters. 30mm @ 40x for larger objects again but even then
it can be hard and or some dont fit into the FOV. 200x is getting rather
high but not out of the question for DSO but seeing can come into play.
I mostly use that sort of power (200x plus) on planets and such. What
sort of scope are you using?
I have a 16"F 4.5, my most used eyepiece is my 13mm Nagler which gives a mag of 140x.
If your 16" is F 4.5? a 9mm will give around 200xmag, I do supernova searching so I am not exactly looking at the galaxy but the possible star in it.
If you want to view with reasonable mag and a good field 13-15 mm eyepiece is a good size one to use.
It all depends what kind of observing you want to do.
Ron
I find that I mostly use 60, 90 or 125x for DSOs and will occasionally push it to 160 (with a nagler so I have a wide FOV). Like Rob, I really only go over 200 for planets.
Thanks guys. My scope is 16" f4.5. So a 9mm will give 200X. I have not seen any galaxies yet so have no idea on their size and the magnification required. But thanks to your opinions, 200X is really only good for planets. Since I have a 2X barlow I should just get a 13 - 15mm EP.
Thanks mate.
With a beast like yours, point it at the Virgo-Coma cluster (to the lower right
of where Saturn is at present). Whack in a low powered EP and go for it.
There is a heap there you'll see for sure.
Here's a chart of galaxies mag 12.5 and brighter in the Virgo-Coma cluster, as
well as a couple in Leo along with the Leo triplet noted in the chart NGC 3627,
3628 with NGC 3623 to the west not labelled.
These should give you something to feast on, the Chart is for around 8pm
and should appear just to the east of due north above your northern horizon.
regards,CS
Last edited by CoombellKid; 30-04-2008 at 08:27 PM.
Thanks CS. I am hoping that the sky will be clear this weekend for me to appreciate these alien worlds.
I don't have a dark site where I live. So it is a test to see how far I can go under those annoying street light outside my house.
I think that with the light gathering capabilities of your 16" scope you can go better than the suggested mags put forward by other posters.
If you notice they are using telescopes with only half to two thirds of the capacity of yours.
start at a low mag and work your way higher, you will soon find what suits you.
You will also find that higher power has a tendency to darken the sky a bit more.
I think you will be selling your scope short if you stick to those mags.
Ron
I've not had much experience trying to view deep sky objects at high magnification but I remember reading somewhere that using high magnification on stars and deep sky objects is irrelavent becuase of their distance it's light gathering power that makes a difference when viewing these objects.
I think it's not true when I said I haven't seen any galaxy at all. I have seen the great Andromeda galaxy with a pair of bino, it is was stunning despite the small bino, and that was before I acquire my current scope. I then used it to have a peek on the LMC. Not bad. Found Tarantula by randomly scannning the area without the help of a star map. But I suppose they are easy targets. When come to those small tiny little galaxies, it's a different ball game. I am excited.
So Ron, since you are a supernova seacher, you keep lots of photographic records of those galaxies? My impression is that you need some form of basis to compare the before and after scene when a supernova occurs so that you are pretty sure something has happened.
General rule of thumb is to use a magnification that gives 2mm exit pupil. Use lower power when this is too much to allow object fit in FOV or when seeing conditions demand it. I found the ~2mm exit pupil rule works well for picking up the most detail on galaxies. That would mean a ~9mm EP with the f/4.5 LB.
Yes TrevorW, to continue on with your post. I have the light bucket, and now I want to make sure I see those DSO's with the right magnification. Wouldn't it be a magnificient view when a DSO like galaxy cover two third of your ep FOV area when you view them? I am interested to know how you all appreciate DSO's? Do you find it satisfactory by looking at them from a far using a low power ep (some use the premium one)? Or you tend to bring it closer to you to examine the details with a short FL ep, like what you do for planets?
some dso's can handle a lot higher power than others, planetary nebula are an example of this. in most cases though i stick to my Pentax XW10 which gives me 150x (exit pupil of 2mm)
So Ron, since you are a supernova seacher, you keep lots of photographic records of those galaxies? My impression is that you need some form of basis to compare the before and after scene when a supernova occurs so that you are pretty sure something has happened.
That's right, you need to have something to compare with to what you see in the eyepiece, I and most S/N searchers have thousands of images.
Give it time, you will find your niech in Astronomy, so just enjoy the jurney.
Ron
another good question, ..and several good answers. ..the 2mm exit-pupil seems a worthwhile 'rule'..and thus a 150x for >8" apertures...
..and as always, the "what if's".. "darksky/urban pollution", "novice/seasoned/jaded eyes"... there's no "what's right"..
as one who rushed in , averse to the "set-in-concrete" & the "from-on-high" ,..and ever the more satisfied that I did.. I can vouch for the logical "bite more when you've chewed enuff to swallow yer present mouthful without choking on it.."
...scales fallen from the eyes and an open mind will see far more in 30mm of rudimentary refractor than 500yrs of improved glass and unimproved mind....
but whatever your 'soup du jour', the expectation pixies will lead you a-merry stray, .. and leave you disenchanted if you let them.
every mag' opens into another room behind.. it's further into the trees, trying to 'see' that forest.... ..and perhaps 'the lesson' is "less is more"
I mainly use 3 eyepieces, a 21mm for open clusters and large nebulae, a 13mm for small nebulae, globular clusters and galaxies and an 8mm for planetary nebulae. The powers and fields with the 12" dob are 21mm=71x=33', 13mm=115x=20' and 8mm=188x=12'. A UHC filter is great for nebulae. A 16" should show almost all of the southern NGC objects, they were discovered by John Herschel with an 18.5" scope that is equivalent to a modern 16.5".
nebulae - i usually stay around 50-150x, depending on size. Obviously larger objects are best at lower powers whereas smaller ones command higher mag to tease out extra detail. However, don't be afraid to expirement - I've viewed Eta Carina at 280x and found all those small dark bays, inlets and lagoons very fascinating to study 'close up'.
planetaries - larger ones look good at about 100-200x, on the smaller ones I go all out and push it to over 500x when seeing permits.
galaxies - larger objects are best at around 100-150x, smaller faint stuff warrant powers of around 200x-250x.
Globulars - I like 250x on virtually all globulars.
I remembered where I read it now 3rd edition "All about telescopes" Edmund 1976, and I quote "100x is enough power for most objects and better seeing is a matter of a bigger diameter objective rather than mere magnification".
