Faintest magnitude I can see with my scope?

[Manok101]

With my 10" assuming moderaate light pollution what is the dimmest magnitude star/object I can see?

[Ad Astra]

You should easily be able to reach down toward Mag 13 or better, depending on light pollution.

I use a C-11, and I can get little moons of Saturn in this range without problems. Mimas & Enceladus are often dimmer than mag 13, and I can get them consistently. Hyperion is usually around Mag 14.5, and I have an awful time with that one.

Point objects are also different from larger, low surface brightness things like galaxies and diffuse nebulae. Your limit on those will probably easily be a full magnitude less, perhaps more. Diffuse things are harder to see and collimation and contrast become critical when you are pushing the limits of the scope.

By far the best thing you can do to improve your 'reach', is to take your machine to darker skies and higher altitudes. These two both make a tremendous difference!

All this said, your mileage may vary, as they say. A bit of time spent with Stellarium to identify dim targets, and then plunge into the dark and see what you can bag at the eyepiece. The moons of Saturn are a nice test for faint point objects just now!

I hope that helps,

Dan

[Manok101]

I did see juno last night and that was visible in my wide field EP if extremely difficult to observe and that (an asteroid if you don't know) the magnitude according to my app was 10.3 so I can at least see that. I'd be happy with 13th mag.

[Ad Astra]

Hi Manok,

One thing I forgot to mention, where I live, the humidity is often less than 30%, sometimes down in the single digits. Our little village is also at roughly 850 ft alt, both of which help improve the view.

If we decide to go for really dark skies, we head out to the Joshua Tree National Park area or with the Riverside Astronomical Society (RAS) to their GMARS facility, or Idylwild / Big Bear, parts of which are over 5000 ft.

Wow!

Dan

[NGC404]

From my Mums back garden (middle of nowhere) I can to to mag 15 with my 10" dob

[John]

From my semi-surburban back garden (with some light pollution issues) I managed to see supernova SN2011b earlier this year which was reported as around magnitude 13.0 at the time. I found it 1st with my 10" newtonain then a couple of nights later (when it might have been around mag 12.8) with my 6" mak-newtonian.

Of course point sources are much easier to see than extended ones - I doubt that I could spot a mag 13 galaxy from my garden.

[brianb]

This depends on your eyes, your experience, your physical condition as much as the scope ... and overwhelmingly on the atmosphere. With 10" and a reasonable site with about x200 I could reach 15.8 when conditions are ideal. Mag 15 ought to be reasonably easy once you've got used to using averted vision.

[banner001]

some quick and fast numbers for you (from the book Star Ware):-

diameter (in) / max. mag

4.5 / 12.0

6 / 12.7

8 / 13.3

10 / 13.8

12.0 / 14.1

minus 1 mag for easily visible stars (i.e. the mag at which you dont need averted vision), add one mag for averted vision/good seeing...so for a 12" you can view to 14.1, 13.1 comfortably, and 15.1 with averted vision or at a dark sky site.

incidently under ideal conditions, across the whole visible sky a 4.5" should show you ~1.5 million stars, 10" ~13 million stars, 12" ~20 million, 16" ~40 million and a 20" ~60 million

[Falcon]

Hi Manok101,

Take a look at this interesting scale: Bortle Dark-Sky Scale - Wikipedia, the free encyclopedia

It’s for naked eye and 12,5” Newton, but It gives roughly what you ask for. As you may see, all depends on the light pollution. The best sky that I’ve ever seen is about class 4 – green .

If you have “Google Earth”, there is a light pollution map for Europe region - see bellow.

We are lucky in East Europe .

[Falcon]

... and for USA

[legoalan]

Does anyone know what the faintest magnitude I can see with my 150mm aperture, 1400mm focal length with a 25mm lense with 2X barlow?

[brianb]

Does anyone know what the faintest magnitude I can see with my 150mm aperture

It depends on your sight & experience.

With 150mm I'd find the optimum magnification for faint stars to be around x120 and I'd expect to be able to creep into the high 14s in good conditions. I used to get to 14.5 - 14.6 with my 6" Newtonian & would expect to be able to beat that by a couple of tenths with the improved efficiency of modern coatings.

Barlows are a good way of losing light. Avoid if at all possible. Simple eyepieces (orthoscopic, Plossl) tend to work better than multi-element types for the faintest objects as they have a higher transmission due to containing less glass and having fewer surfaces to scatter light.

[banner001]

Does anyone know what the faintest magnitude I can see with my 150mm aperture, 1400mm focal length with a 25mm lense with 2X barlow?

congratulations for not bothering to look at post #8

its ~12.7 mag, at a dark sky site with averted vision you might get to 13.4 - 14, but thats your absolute limit, you should comfortably see things of mag 11 to 11.5

[legoalan]

Haha, silly me. I will definitely read any other previous posts before asking stupid questions =P. I'm not sure my scope will function as well as a normal 150mm aperture, 1400mm focal length telescope as I got it off ebay second handed and it's not branded at all and I still haven't got round to collimating it (yeh I know thats really stupid of me)