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Equipment Discussions >> Reflectors

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George N
Carpal Tunnel
*****

Reged: 05/19/06

Loc: Binghamton & Indian Lake NY
Re: How large does your relector have to be to.... new [Re: mantrain]
      #6485516 - 04/24/14 12:35 PM

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I don't know how long it would take to systematically attempt to see the whole NGC catalog. I would assume my 14.5 inch mirror under dark skies would be enough. Under light polluted conditions I imaging some low contrast objects would be very difficult. Some objects like the California nebula (NGC 1499) I have only successfully detected when imaging. I have tried using a Hydrogen Beta filter without success under very dark skies. It a pretty easy target for my C11 EdgeHD in Hyperstar mode.




I would suggest another try at it. I have seen the California nebula from my dark sky site with my unaided eye by just holding the H-Beta filter up to my eye and shielding it from any external lighting. In my 100mm f/6 refractor at 15x (4.39 degree true field of view) using the Lumicon H-Beta filter, it is fairly easy to see, although it isn't terribly bright. It won't fit in the maximum field of my 9.25 inch SCT, but with the H-Beta filter, I can still pan around and see a couple of its very broad diffuse filaments. Clear skies to you.





Well if the NGC catalog was indexed using 72" and 49.5" reflectors, that changes everything --even if the efficiency was 50% o today. I had no idea they were using a 72" scope for some of those objects originally.




A goodly number of the fainter galaxies in the NGC were discovered with 12 to 15 inch refractors - typical of the better observatories of the latter 19th Century. Several observers were in 'competition' and they believed that dimmer 'galaxies' clustered around brighter ones. That is why there tends to be the most errors in the NGC around bright galaxies. (Example: several of the faint fuzzies around NGC 7331 are actually double stars, or erroneous re-observations of the same object, or simply don't exist.) Also, with the NGC, a goodly number of the open clusters don't exist either.

I would bet that nearly all of the actually existing NGC objects could be seen in an 18-inch, but a 14 might be able to do it, as long as it is used under dark skies.

Of course, when we are talking visual observing, the human eyeball is as important as the scope. One thing is almost certainly true: If you can see the entire NGC in a 14-inch at age 30, you will probably need an 18 or 20 by age 65. An avid observer friend of mine who is an MD (owns a 22" Dob, several AP refractors, etc) told me: it's not matter of 'if', it's just a matter of 'when' your eye lenses start to cloud up. His suggestion: go outside the USA to get eye lens implants that are not coated with UV filters (required in the US), but then you'll need to wear UV filtered glasses whenever going outside to prevent damage to your retina.


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sgottlieb
scholastic sledgehammer
*****

Reged: 07/22/07

Loc: SF Bay area
Re: How large does your relector have to be to.... new [Re: George N]
      #6486719 - 04/24/14 10:22 PM

Quote:

A goodly number of the fainter galaxies in the NGC were discovered with 12 to 15 inch refractors - typical of the better observatories of the latter 19th Century. Several observers were in 'competition' and they believed that dimmer 'galaxies' clustered around brighter ones. That is why there tends to be the most errors in the NGC around bright galaxies. (Example: several of the faint fuzzies around NGC 7331 are actually double stars, or erroneous re-observations of the same object, or simply don't exist.) Also, with the NGC, a goodly number of the open clusters don't exist either.

I would bet that nearly all of the actually existing NGC objects could be seen in an 18-inch, but a 14 might be able to do it, as long as it is used under dark skies.

Of course, when we are talking visual observing, the human eyeball is as important as the scope. One thing is almost certainly true: If you can see the entire NGC in a 14-inch at age 30, you will probably need an 18 or 20 by age 65...




A number of excellent points, George. There's really no definitive answer on the minimum aperture required to view the entire NGC as there are so many variables, but ....

As far as observing all the existing NGC objects with an 18-inch, you would win that bet as I finished up the entire NGC last month! Well, at least as far south as -45° dec, with almost 300 left in the far southern hemisphere.

I started this project off in 1978 with a 6", switched to an 8" a couple of years later and then a 13" in 1982. Although several thousand NGC's were observed with this scope, nearly all the rest were done with an 18". So, observing the NGC extended over 36 years (with lots of interruptions for the IC's, Arps, Hicksons, Palomars, Abell clusters, Vorontsov-Velyaminov interacting galaxies, etc.) All observations were made at fairly dark rural sites or dark, high elevation California sites.

There are quite a number of large-aperture discoveries in the (northern) NGC. Probably many more than folks realize. Here's the breakdown (rounded to nearest 10)

William Herschel: 2360 with an 18-inch (speculum) reflector (England)
John Herschel: 650 with an 18-inch reflector (England and Cape of Good Hope)
Albert Marth: 650 with a 48-inch reflector from Malta
Lewis Swift: 460 with a 16-inch refractor (Warner Observatory in N.Y.)
Édouard Stephan: 410 with a 31-inch (silvered glass) reflector at Marseille
Leavenworth/Muller/Stone: 380 with a 26-inch refractor in Virginia
Lord Rosse (and assistants): 250 with a 72-inch from Birr Castle, Ireland.

With this impressive array of glass and speculum metal, quite a few toughies are found in the NGC for an 18-inch or smaller scope. If you want to start from the beginning, take NGC 4 for example. It was discovered by Albert Marth with the 48-inch built by William Lassell (equatorial fork driven by a hand crank). This faint galaxy has a magnitude of just V = 15.9 and B = 16.8. It's visible in an 18-inch from a dark site, but its certainly not easy. Of course, having a detailed (computerized) finder chart helps immensely -- it's much easier to detect a faint galaxy when you know exactly where to look, then to discover it in the first place like Marth!


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BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: How large does your relector have to be to.... new [Re: mantrain]
      #6486842 - 04/24/14 11:26 PM

Quote:

So a 10" could potentially view every object in the NGC?
(assuming that would travel to northern and southern hemispheres.


If that were my goal,then I'd figure out how to get a 16" if finances are a major factor;and if lots of money was available then I'd get one the largest aperture fast scope (and the newest coma correctors and eyepieces)with a proven goto (push-to) system.Going from a 4.5 to a 10 to a 12 inch reflector revealed more stars every step but galaxies and diffuse objects still need the dark sky.If you just want to see as much as possible on a budget ,one of the 12" Dobs is the ticket!

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christheman200
sage


Reged: 06/12/13

Loc: Toronto, Canada
Re: How large does your relector have to be to.... new [Re: BigC]
      #6486971 - 04/25/14 01:04 AM

For most objects in the NGC list in a 12", you should be able to spot them if they are in the field of view. From personal experience, if you can't find it, it's because you're looking at the wrong place.

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David Knisely
Postmaster
*****

Reged: 04/19/04

Loc: southeastern Nebraska
Re: How large does your relector have to be to.... new [Re: christheman200]
      #6487007 - 04/25/14 01:54 AM

Quote:

For most objects in the NGC list in a 12", you should be able to spot them if they are in the field of view. From personal experience, if you can't find it, it's because you're looking at the wrong place.




Or that the object actually does not exist (and there are a number of them, like the "glare in the eyepiece" nebula NGC 1990 or the so-called "open cluster" NGC 2253, both of which made the Herschel II listing). For a few questionable entries, the NGC/IC project has a page for 85 of the "not found" NGC objects:

http://www.ngcicproject.org/projobslist.htm

Clear skies to you.


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BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: How large does your relector have to be to.... new [Re: christheman200]
      #6487485 - 04/25/14 10:22 AM

Quote:

For most objects in the NGC list in a 12", you should be able to spot them if they are in the field of view. From personal experience, if you can't find it, it's because you're looking at the wrong place.


My philosophy is :"it will be much easier to find objects that are well within the reach of a big scope,as opposed to straining to see objects at the limit of a small scope".

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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: How large does your relector have to be to.... new [Re: BigC]
      #6489105 - 04/26/14 01:48 AM

I have not failed to find any "real" NGC object I have sought with the 12.5".
The non-existent ones I've expunged from my viewing list.
I observe, typically, at high altitude, under NELM 6.8+ skies, and occasionally at sites with even darker skies. "Challenge" objects I try to observe only when on/near the meridian. There are some of magnitude 15-16 in my log.
I've had a little more trouble with some UGC, PGC, and MCG galaxies, with quite a few NF (Not Found) markings.
When a catalog lists the magnitude as fainter than 15, look at the size. I find that if it's under 1' in size, it's often a lot easier than the 2-3' size at magnitude 14.
Note that there is a difference between "detect" and "observe". Some of the NGC objects are quite faint. And some of the UGC, PGC, MCG and ESO galaxies are easy enough you wonder why they aren't in the NGC.

For a list of the brighter 23,000 galaxies, see the 3rd Reference Catalogue (RC3) of Vaucouleurs, list downloadable from the web. That'll keep you busy for a few weeks.


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Eddgie
Postmaster
*****

Reged: 02/01/06

Re: How large does your relector have to be to.... new [Re: David Knisely]
      #6489371 - 04/26/14 08:48 AM

Quote:

under dark sky conditions




I was careful to report that my observations were from my back yard and I live in Central Austin.

I encouraged the OP to seek dark skies if he wanted to be successful.

Sounds like we were in general agreement.


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Shneor
scholastic sledgehammer
*****

Reged: 03/01/05

Loc: Northern California
Re: How large does your relector have to be to.... new [Re: George N]
      #6491175 - 04/27/14 02:20 AM

Quote:

An avid observer friend of mine who is an MD (owns a 22" Dob, several AP refractors, etc) told me: it's not matter of 'if', it's just a matter of 'when' your eye lenses start to cloud up. His suggestion: go outside the USA to get eye lens implants that are not coated with UV filters (required in the US), but then you'll need to wear UV filtered glasses whenever going outside to prevent damage to your retina.
Quote:


I have an implant lens in my left eye. I can see into the ultraviolet a bit with it. If there's a UV filter coating on it, it still allows some UV through. And it was done here, in the US.

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