Not seeing what I think I should

[Kingofthehill]

Greetings,

As many of you know I am the owner of an Obsession 18UC. I have been able to get out a few times in the past month, which is a little more than normal for me.
There is an issue which plagues me, however: I am not seeing everything I think I should be able to see with this wonderful scope.
I believe I know the answer, but feel free to chime-in if you believe I am missing something.

First, I believe my collimation is pretty close to perfect.
Second, I use the Argo Navis, which is really good for getting darn close to an object.
Third, I am in the mountains at 5300 feet, but still in a "yellow" zone.

Last night the faintest object I could assuredly identify was a galaxy of magnitude 12.8 (I forget its number).
Surely I should be able to find things fainter than that with an 18 inch primary and very nice eyepieces.

I think what I need is darker skies.

Is there something I have overlooked? Or, should I move?

Thanks.

[JayTee]

Hi Paul,

You live in a yellow zone. The fact that you could see a 12.8 mag Galaxy is outstanding for a yellow zone, even with an 18 inch telescope.

Please try not to judge your scope until you've had it out to at least a Bortle 2 sky, then you'll have a decent comparison from which to judge.

Cheers,
JT

[Kingofthehill]

Hi Paul,

You live in a yellow zone. The fact that you could see a 12.8 mag Galaxy is outstanding for a yellow zone, even with an 18 inch telescope.

Please try not to judge your scope until you've had it out to at least a Bortle 2 sky, then you'll have a decent comparison from which to judge.

Cheers,
JT

JT,

Darker skies would be great. I guess I should have asked what kind of dark zones are folks in where they can catch limited magnitude objects, besides stars (13 or dimmer).
Thanks for the reply.

[OzEclipse]

Hi Paul,

I have an 18"f5.6 with Galaxy optics . I observe from a site with Bortle 2 skies near the boundary to Bortle 1.

Zenith sky brightness information
SQM 21.96 mag./arc sec2
Brightness 0.177 mcd/m2
Artif. bright. 6.18 μcd/m2
Ratio 0.0361
Bortle class 2
Elevation 689 meters

The fainter members of the Grus Quartet
NGC7590 Mv 12
NGC7599 Mv 12
are both 1'x2' in size and are both easy

If you are forgetting anything, it is that the integrated visual magnitude has to be considered in combination with the apparent diameter to give the surface brightness then that compared to the background sky brightness . Do you use a shroud? My site is so dark, I can only just see my hand in front of my face. The mirror sits in a deep rockerbox but I don't need a shroud on the trusses.

Previous owner of the scope told me he just detected Polarissima Australis NGC2573 Mv 14.55 (30"x60") from dark skies. I prefer to use the larger aperture to carefully examine more detail in easily detected objects rather than looking for the barely detectable. I've done enough of that in my past observing with smaller scopes.

Hope this helps

Joe

[helicon]

Overall my experience is similar - faintest I can go is about 13 on the best of nights with unusually darker sky conditions. Other than that it's around 12.5 and I am in a red zone. The brightness of the sky background is the culprit in my opinion.

[Bigzmey]

Yellow zone is the main factor, but night to night differences in the sky conditions will contribute as well. Don't get discouraged, keep at it. There will be better nights when you can push further. Also, as your galaxy eye develops you will be able to pick fainter and fainter things.

My home is in yellow-orange zone. Even the brighter galaxies are reduced just to their cores. Two hour drive east takes me to the green-blue zone. The galaxies come alive. Even in 4" scope I see details in the disks, which are not visible in 8" from home.

[Kingofthehill]

Suspicions confirmed, I need to find darker skies. I have been considering overall size of object when considering magnitude, knowing that as size increases and magnitude stays constant, relative visible brightness decreases.
I'm trying to organize, in my head, a fall trip to Death Valley with mountain camping.

[SkyHiker]

Suspicions confirmed, I need to find darker skies. I have been considering overall size of object when considering magnitude, knowing that as size increases and magnitude stays constant, relative visible brightness decreases.
I'm trying to organize, in my head, a fall trip to Death Valley with mountain camping.

Death Valley can be good but is not the greatest IMHO. There can be dust in the air and the light dome of Vegas is a problem. Try the mountains West of 395 for instance the Horseshoe Meadows campground at 10000 feet. The Alabama Hills are also quite good. Avoid forest fires, there can be several several going on. Many astronomers from LA go to the Mount Pinos parking lot at New Moon. The Big Bear Lake area is also good. The RTMC is happening there in September at 7000 feet, you can camp there and have a super astro conference time though the Moon is not in an ideal position.

[helicon]

I like Mt. Pinos as an observing perch, been to the top several times.

I also like the White Mtns straddling the Nevada - California border. About as dark as you can get. In the daytime you can see the ancient Bristlecone pines.

[Kingofthehill]

I like Mt. Pinos as an observing perch, been to the top several times.

I also like the White Mtns straddling the Nevada - California border. About as dark as you can get. In the daytime you can see the ancient Bristlecone pines.

Bristlecones are awesome trees. Thanks.

[Kingofthehill]

Suspicions confirmed, I need to find darker skies. I have been considering overall size of object when considering magnitude, knowing that as size increases and magnitude stays constant, relative visible brightness decreases.
I'm trying to organize, in my head, a fall trip to Death Valley with mountain camping.

Death Valley can be good but is not the greatest IMHO. There can be dust in the air and the light dome of Vegas is a problem. Try the mountains West of 395 for instance the Horseshoe Meadows campground at 10000 feet. The Alabama Hills are also quite good. Avoid forest fires, there can be several several going on. Many astronomers from LA go to the Mount Pinos parking lot at New Moon. The Big Bear Lake area is also good. The RTMC is happening there in September at 7000 feet, you can camp there and have a super astro conference time though the Moon is not in an ideal position.

Thanks for the suggestions, I'll take a look at logistics.

[helicon]

If you do go to Death Valley try to camp either at the Mesquite Campground at 8,000 feet on the flanks of Telescope Peak or the Eureka Dunes campground 50 miles away from Furnace Creek in the north end of the park. Mesquite has very good seeing conditions though you can see the light dome of Vegas on the horizon. However, the elevation shields it from the extreme heat of the Valley so a Summer camping experience is possible. From Eureka Dunes you can't see the light dome. There are lots of parking spaces at Mesquite but only four at Eureka Dunes. It is a primitive campground with no water so you will have to bring some.