Magnitude, getting a handle on it,

[drahyrt (Steve)]

Hi all,
Just trying to get a handle on what I can expect to see and not see, so I'm not looking for things I'm never going to see....
I understand it depends on my location, time of night, surrounding contamination of light, eyepieces etc etc etc,

I have a 150mm reflector.

ON AVERAGE in regional NSW, what should I expect to see down to with an average quality reflector with average eyepieces?

I did a search on this forum, no luck but found this link to magnitude, but thought I could get a real perspective.

http://www.cfa.harvard.edu/icq/MagScale.html

(My main motive - to look at stellarium, and pick DSO's to find based on what approximate magnitude they are and what equip I currently have).

Based on the harvard site, I might be lucky with "good" viewing conditions to see mag 10-11??? or am I dreaming? (insert "the Castle" film quotes here).

Ok so hit me with the reality,
TIA
Steve
Newbgazer

[Ian Robinson]

You can see 11th mag stars with a 60mm refractor and easily with a 80mm refractor or binos.

A 6" newt will give you stars about 13th mag I believe depending on you visual accuity and seeing conditions

http://www.twcac.org/Tutorials/limit...tude_table.htm

http://www.go.ednet.ns.ca/~larry/astro/maglimit.html

[drahyrt (Steve)]

Wow great links,
THANK YOU.

[Kal (Andrew)]

With DSO it is difficult to know which objects will be visible just by looking at their magnitude. While a magnitude 9 star will be easily visible because the light is a single point, a magnitude 9 DSO such as a galaxy will have that light spread over a larger area. Imagine taking that same star and defocusing it until the light is spread over the same area in the eyepiece as the galaxy, I'm sure you can understand what I am saying.

[bmitchell82 (Brendan)]

... Easy, get a star map that has a legend to what size dot equates to then start star hopping untill you cant see them anymore! Heypresto. Do the hard yards first learn a bit while your there.

Get Astronomy 2009 from Quasar publishing or where i brought it for 29.95 Australian Geographic (yes i missed the bulk order boat on ISS.. ) but this has some good star maps.!

[drahyrt (Steve)]

Hi Andrew,
Yes that does make sense, cheers.

I have astromomy 2009, and just waiting for a trip to Syd to get a better star map. Thanks Brendan.

You all have helped me get a handle on it, just after a rough guide though which is what you've done, thanks.

Steve

[Terry B]

Originally Posted by Ian Robinson

You can see 11th mag stars with a 60mm refractor and easily with a 80mm refractor or binos.

A 6" newt will give you stars about 13th mag I believe depending on you visual accuity and seeing conditions

http://www.twcac.org/Tutorials/limit...tude_table.htm

http://www.go.ednet.ns.ca/~larry/astro/maglimit.html

I looked at these tables.
I have reasonable eyesight and very dark skies. With my scope (200mm) I have just seen pluto when it was at mag 13.9 a few years ago. The table gives "14.0 or 15.2" as the limits for my scope size. I think the 14 is pretty close. To image a 15.2 mag star with a reasonable SN ratio would need a ~10 sec exposure minimum. I think this value is unrealistic for visual limits.

[bmitchell82 (Brendan)]

there are also some very comprehensive star maps avalible from this site, have a lookseee around youll find them

[Ian Robinson]

Originally Posted by Kal

With DSO it is difficult to know which objects will be visible just by looking at their magnitude. While a magnitude 9 star will be easily visible because the light is a single point, a magnitude 9 DSO such as a galaxy will have that light spread over a larger area. Imagine taking that same star and defocusing it until the light is spread over the same area in the eyepiece as the galaxy, I'm sure you can understand what I am saying.

Yes extended "fuzzies" make the limiting mag more so so. Probably take 1-1.5 mag off that max for fuzzies if you are trying to see them , even more if the contrast if bad , ie light polluted , moonlit , bad or no=existant baffling and flokking , maybe take 2 or 3 mags off ....

More subjective , as often tricks like averted vision will help.