Limiting magnitude on a sct

13 years 11 months ago #23758 by bertthebudgie
Limiting magnitude on a sct was created by bertthebudgie
Hi

Just wondering what level of magnitude should one expect to get down to (visually) in the light poluted skies of dublin with an 8' sct

Thanks

Eqipment
Lx90 8' SCT, UHC Narrowband filter
SPC900 Webcam, Atik 16ic
Astrozap Dew Heater
Meade eyepieces & barlows 9,26 and 32mm
Moonfish 32mm 2"
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"Always pass to the man in space"

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13 years 11 months ago #23759 by martinastro
Replied by martinastro on topic Limiting magnitude on a sct
Normally around mag 14 in a dark sky however its hard to say because i dont know the extent of the light pollution there however on the plus side stellar objects should be easier to detect than fuzzies of the same mag. What are your observing targets?

Good luck and clear skies David :D

Martin Mc Kenna

coruscations attending the whole length of the luminosity, giving to the phenomena the aspect of a wrathful messenger, and not that of a tranquil body pursuing a harmless course..comet of 1680

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13 years 11 months ago #23761 by Skylord
Replied by Skylord on topic Limiting magnitude on a sct

Hi

Just wondering what level of magnitude should one expect to get down to (visually) in the light poluted skies of dublin with an 8' sct Thanks


David,

The limiting stellar magnitude typically quoted for an 8-inch scope is 13.5, perhaps a bit better under really good skies. It's difficult to say what you'll reach under Dublin's light polluted skies, as it depends on where you are and how much dust or moistness is in the air reflecting light etc.

Deep sky objects such as galaxies, nebulae and the like are a different matter as the surface brightness is what counts, not necessarily quoted magnitudes.

I usually try a few well known objects first and how they look gives me some idea of what to try for after that.

Starlord

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13 years 11 months ago #23762 by bertthebudgie
Replied by bertthebudgie on topic Limiting magnitude on a sct
Well Was hoping to try for something deep sky like m51 or something which is below naked eye visibilty

Eqipment
Lx90 8' SCT, UHC Narrowband filter
SPC900 Webcam, Atik 16ic
Astrozap Dew Heater
Meade eyepieces & barlows 9,26 and 32mm
Moonfish 32mm 2"
_______________________________________

"Always pass to the man in space"

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13 years 11 months ago #23773 by Keith g
Replied by Keith g on topic Limiting magnitude on a sct
David, It all depends on the extent of the local light pollution, but at the zenith, I typically can get to 13.5 on a good transparent night, but maybe at about only 11 really low down.

You should get M51 alright, just depends on where it is in the sky at the time your looking,

Keith..

If a telescope can fit into your backyard it's too small. If you can't move it, it's too big." -- John Dobson

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13 years 11 months ago #24171 by jeyjey
Replied by jeyjey on topic Limiting magnitude on a sct
David --

I think you're going to have trouble with M51 from Celbridge. In my 8" (from 15m north of Drogheda), I get two dim smudges, and I've got a *lot* less light pollution.

Keep in mind that with our damp air, the altitude has a dramatic effect on the light pollution. So if you wait until 4am or so (when M51 is approaching the zenith), your chances will be much better. In April, midnight will do.

Even better would be to go someplace dark. There's a dark spot on my light pollution map half-way between Kinnegad and Tyrrellspass, a bit south of the N4.

Good luck,
-- Jeff.

Nikon 18x70s / UA Millennium                              Colorado:
Solarscope SF70 / TV Pronto / AP400QMD             Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO               Tak Mewlon 250 / AP600EGTO

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13 years 11 months ago #24174 by michaeloconnell
Replied by michaeloconnell on topic Limiting magnitude on a sct
David,

From a dark sky, an 8"SCT is well able to pull in M51 and it's associated galaxy NGC 5195. From a dark sky, I've seen two of the spiral arms.
From a dark sky, you'd typically be able to get down to about 13 to 13.5. On clear nights, about mag 14. On one exceptionally good night, I could see down as far as 15.3. However, that only happened once.

However, light pollution really does hinder things. From here in Monasterevin, M51 is much fainter and the background sky is brighter, so the contrast is also worse. I'd say my limiting mag with the scope here would be around 12.5 at a guess. Must measure it now that I've moved house here.

Are you thinking of buying?

Regards,

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13 years 11 months ago #24184 by bertthebudgie
Replied by bertthebudgie on topic Limiting magnitude on a sct
I have a lx90 8' and was not able to spot a lot of the deap sky objects that I know an 8' should be able to find. I guess it really is the light pollution that is to blame and will have to find and venture out to a dark site soon

Eqipment
Lx90 8' SCT, UHC Narrowband filter
SPC900 Webcam, Atik 16ic
Astrozap Dew Heater
Meade eyepieces & barlows 9,26 and 32mm
Moonfish 32mm 2"
_______________________________________

"Always pass to the man in space"

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13 years 11 months ago #24196 by jeyjey
Replied by jeyjey on topic Limiting magnitude on a sct
David --

For when you're observing from home, check out the Urban Club's DSO target list: www.astroleague.org/al/obsclubs/urban/urbanld.html .

It's specifically made for high-light-pollution areas. You'll note the inclusion of brighter galaxies such as M81 and M82, but not the harder ones such as M33 and M51. It also includes a bunch of bright NGC stuff that you might not otherwise know about.

-- Jeff.

Nikon 18x70s / UA Millennium                              Colorado:
Solarscope SF70 / TV Pronto / AP400QMD             Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO               Tak Mewlon 250 / AP600EGTO

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13 years 11 months ago #24203 by dave_lillis
Replied by dave_lillis on topic Limiting magnitude on a sct
Here in limerick with all the light pollution, I can just about catch Pluto visually with the 12" scope, I can easily use mag 11/12 star to aid polar allignment, so a 8" scope (given high light pollution) should be able to see mag 11.
Having said that, the magnitudes of faint galaxies is deceptive, they are aften alot more fainter then the rated magnitude in a catalogue, just because you can see mag 11 stars doesnt mean you cen see picture postcard images of M51.
With such objects its the brightness contrast that allows them to be visible, star points are much easier to see compared to faint diffuse objects of the same magnitude.

Dave L. on facebook , See my images in flickr
IFAS Rep. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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13 years 11 months ago #24213 by dmcdona
Replied by dmcdona on topic Limiting magnitude on a sct
FWIW...

I'm looking at imagers at the moment. SBIG claim their ST7 (just above entry level) imager will get down to mag 19 with an 8" SCT :shock:

Dave

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13 years 11 months ago #24228 by dave_lillis
Replied by dave_lillis on topic Limiting magnitude on a sct
ST7, I would have thought you go for a bigger chip, I've been looking at the st10 and st-11000 on astromart, they are amazing astronomical cameras with amazing astronomical prices. :lol:

With the canon, I can routinely hit mag 16-17 with a few minutes or so exposure, these cameras would wipe the floor with the canon.
Apparently, a 20 minute exposure with the canon is akin to a 30 second exposure with one of these beauties.

Dave L. on facebook , See my images in flickr
IFAS Rep. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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13 years 11 months ago #24239 by dmcdona
Replied by dmcdona on topic Limiting magnitude on a sct
Who said I was looking at the ST7? :wink:

I was thinking of the 6303E... Just like you were thinking of the ST1100M :D

Actually, the ST7 is more in my price range - the ST8 might be a stretch. Consider that I'd get the BVRI filter set and a filter wheel and the price rockets...

The chip size for what I want to do is actually not that critical. The bigger chips obviously give more scope for wider fields but the ST7 chipsize is fine for my needs, which is not widefield imaging.

With the ST7 in the config I'd like, its about $4k new...

Are you seriously considering the ST10?

Cheers

Dave

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13 years 11 months ago #24252 by dave_lillis
Replied by dave_lillis on topic Limiting magnitude on a sct
I am, but a second hand one in astromart, I'm not buying one of these new, and I'm talking about the next year or so, not anytime soon.

Dave L. on facebook , See my images in flickr
IFAS Rep. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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