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Equipment Discussions >> Reflectors

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mantrain
scholastic sledgehammer
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Reged: 07/22/11

Loc: San Diego
How large does your relector have to be to....
      #6482297 - 04/22/14 11:12 PM

Assuming excellent conditions, etc how large of a reflector is required to be able to view every object in the NGC catalog?

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azure1961p
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Reged: 01/17/09

Loc: USA
Re: How large does your relector have to be to.... new [Re: mantrain]
      #6482350 - 04/22/14 11:45 PM

Tackling some that THAT big - Id want 12" and wouldn't dip below 10". Something like 6.5v sky's or better.

Pete
Edit: I was too optimistic on this mentioning the 10" minimum . Sorry for a any mislead. A 12" would be a better choice. And even then its got its work cut out.

Edited by azure1961p (04/23/14 08:25 PM)


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mantrain
scholastic sledgehammer
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Reged: 07/22/11

Loc: San Diego
Re: How large does your relector have to be to.... new [Re: azure1961p]
      #6482443 - 04/23/14 12:53 AM

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


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Bill Weir
Carpal Tunnel
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Reged: 06/01/04

Loc: Metchosin (Victoria), Canada
Re: How large does your relector have to be to.... new [Re: mantrain]
      #6482484 - 04/23/14 01:40 AM

It would be tough and totally depend on your skill level. Also expect it to take a good deal of time. Many you would probably find difficult with your 16". Ths is from personal experience as I work my way through the Herschel 2500, mostly so far with my 12.5" and now my 20". I started in 2009 and due to sky/weather conditions as well as side observing desires I'm only now closing in on 1900. It also has taken a good deal of planning as no DSS are involved.

Bill


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svdwal
Vendor (mBrain Software)


Reged: 03/10/13

Loc: Leiden, The Netherlands
Re: How large does your relector have to be to.... new [Re: Bill Weir]
      #6482659 - 04/23/14 07:03 AM

O'Meara states in his "Herschel 400 observing guide" that a modern 10" with excellent coatings under a properly dark sky should be equivalent to Herschels own 18.7 inch speculum mirror. Herschel did not find all the objects in the NGC, so a 10" is probably too small.

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MitchAlsup
Pooh-Bah


Reged: 08/31/09

Re: How large does your relector have to be to.... new [Re: svdwal]
      #6482908 - 04/23/14 09:46 AM

6" a tracking drive and a camera.
12"-14" visually under pristine skies.


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JMW
Pooh-Bah


Reged: 02/11/07

Loc: Nevada
Re: How large does your relector have to be to.... new [Re: MitchAlsup]
      #6483180 - 04/23/14 11:49 AM

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.

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mantrain
scholastic sledgehammer
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Reged: 07/22/11

Loc: San Diego
Re: How large does your relector have to be to.... new [Re: JMW]
      #6483231 - 04/23/14 12:13 PM

Thanks everyone,

Now please allow me to rephrase the question, I was unclear:

What size reflector would be needed for nearly all the NGC objects to be view-able under good skies?Not assuming one wants to get through the entire catalog, just know the expectation that any particular object is view-able.

And what about the IC ?????

Edited by mantrain (04/23/14 12:15 PM)


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JMW
Pooh-Bah


Reged: 02/11/07

Loc: Nevada
Re: How large does your relector have to be to.... new [Re: mantrain]
      #6483300 - 04/23/14 12:47 PM

I just downloaded an spreadsheet of the NGC catalog. There are a small number of objects with a visual magnitude of 16 or greater. My 14.5 mirror should be able to go to about 16.4 magnitude under perfect conditions. The visual magnitude can be misleading for objet that are very spread out. Dark skies are very important to help with contract. Seeing can also be a factor.

A 12 inch scope can be purchased for under $800 and would give you the potential to see objects with a magnitude of about 16. Under dark skies with perfect conditions you would have the potential to detect the vast majority of objects in the NGC catalog. Being sure that you actually recognize the object in the field is another mater that relates to the observers experience and access to could catalogs that show what you should expect to see in the eyepiece.


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David Knisely
Postmaster
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: How large does your relector have to be to.... new [Re: JMW]
      #6483794 - 04/23/14 04:37 PM

Quote:

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.


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mantrain
scholastic sledgehammer
*****

Reged: 07/22/11

Loc: San Diego
Re: How large does your relector have to be to.... new [Re: David Knisely]
      #6484197 - 04/23/14 08:01 PM

Ok, so it sounds like a 10" is good enough to see most any NGC object (assuming reasonable conditions).

What about the IC ???


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: How large does your relector have to be to.... new [Re: mantrain]
      #6484224 - 04/23/14 08:15 PM

Quote:

Ok, so it sounds like a 10" is good enough to see most any NGC object (assuming reasonable conditions).

What about the IC ???




The Index Catalog is all over the place in terms of visibility of the objects in that catalog. Some like IC 4665 are ridiculously easy to see, but other IC objects can push the visual capabilities of even very large (18 to 30 inch) amateur instruments. There are also quite a number of the IC entries that are either unknown or do not exist (faint stars, double stars, or just plain errors). You just have to go and see what you can see. Clear skies to you.


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Achernar
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Reged: 02/25/06

Loc: Mobile, Alabama, USA
Re: How large does your relector have to be to.... new [Re: mantrain]
      #6484349 - 04/23/14 09:02 PM

The original NGC catalog was compiled with a 10-inch telescope. I would say you'd want at least a 15 or 16-inch telescope to see every NGC object, and at that some are going to be very faint. I have observed some 1,100 deep sky objects so far, the faintest being about 15th magnitude with my telescopes.

Taras


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Eddgie
Postmaster
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Reged: 02/01/06

Re: How large does your relector have to be to.... new [Re: mantrain]
      #6484366 - 04/23/14 09:09 PM

I have been hacking away at the NGC catalog for a decade using a C11, C14, and 12" dob.

I have logged a lot of "Not seen" entries.

There are a hugh amount of very dim NGC objects.

If you want to know what you have a chance of seeing, may I recommend the Night Sky Observer's Guide?

This is a two volume book that includes thousands of targets, and it has a "Star" rating along with descriptions on how these objects appear in many different size telescopes.

I would just annotate in my copy when I tried to observe something.

But there are a lot of magnitude 13 and 14 galaxies that I think would be impossible to see in anything less than a pretty large scope (15" to 20") used under very dark and highly transparent skies.

In 10 years, I think I have listed more as "Not seen" than as "Observed."

I only observe from my back yard though, so don't let that stop you.

I recommend the two volume book though. It is an amazing work and a great observation planning tool.

Good luck...


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David Knisely
Postmaster
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: How large does your relector have to be to.... new [Re: Achernar]
      #6484764 - 04/24/14 01:20 AM

Achernar wrote:

Quote:

The original NGC catalog was compiled with a 10-inch telescope.




Well, not quite. While a majority of the NGC objects can be seen in a 10 inch under very dark sky conditions, that is not the aperture that was used to make the observations for that catalog. The NGC was compiled by John Dreyer in 1888 from observations of William and John Herschel, as well as from a few other sources. The observations were done with apertures from two inches to 72 inches. Indeed William Herschel used apertures of 6.2 inches, 12 inches, 18.7 inches, and 49.5 inches for his surveys that produced a large number of the observations that went into the NGC. His speculum mirrors don't have the efficiency that ours do now, so his 18.7 inch was probably close to the performance of a modern 10 inch now. However, the survey was done with some pretty sizable apertures. Clear skies to you.


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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: How large does your relector have to be to.... new [Re: Eddgie]
      #6484791 - 04/24/14 01:42 AM

Eddgie wrote:

Quote:

But there are a lot of magnitude 13 and 14 galaxies that I think would be impossible to see in anything less than a pretty large scope (15" to 20") used under very dark and highly transparent skies.




Galaxies fainter than 13th or 14th magnitude might be difficult to see in apertures less than 15 inches, but definitely not impossible. Indeed, at least a few of the galaxies in Stephan's Quintet are visible in an 8 inch (and some have seen them in smaller instruments) even though the brightest individual galaxy in the group is close to 13th magnitude. I have managed to get about three of the very faint galaxies in the much more difficult grouping known as Seyfert's Sextet (NGC 6027 a, b, c, d, e) in my 9.25 inch SCT even though the brightest is magnitude 14.7. With the Perseus Galaxy Cluster (Abell 426), I can probably see at least 10 to 15 of its component galaxies, and many of these are fainter than 13th magnitude. While the magnitudes of faint galaxies are often not extremely accurate, with some patience and study (especially at moderate to high power), a 10 inch under dark sky conditions may be able to reveal a number of galaxies down to around 15th magnitude or so. Clear skies to you.


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mantrain
scholastic sledgehammer
*****

Reged: 07/22/11

Loc: San Diego
Re: How large does your relector have to be to.... new [Re: David Knisely]
      #6484803 - 04/24/14 01:56 AM

Quote:

Quote:

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.


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Mark Harry
Vendor
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Reged: 09/05/05

Loc: Northeast USA
Re: How large does your relector have to be to.... new [Re: David Knisely]
      #6485049 - 04/24/14 07:41 AM

Quote:

Achernar wrote:

Quote:

The original NGC catalog was compiled with a 10-inch telescope.




Well, not quite. While a majority of the NGC objects can be seen in a 10 inch under very dark sky conditions, that is not the aperture that was used to make the observations for that catalog. The NGC was compiled by John Dreyer in 1888 from observations of William and John Herschel, as well as from a few other sources. The observations were done with apertures from two inches to 72 inches. Indeed William Herschel used apertures of 6.2 inches, 12 inches, 18.7 inches, and 49.5 inches for his surveys that produced a large number of the observations that went into the NGC. His speculum mirrors don't have the efficiency that ours do now, so his 18.7 inch was probably close to the performance of a modern 10 inch now. However, the survey was done with some pretty sizable apertures. Clear skies to you.



********
And the skies were a lot darker from lack of all pollution!
M.

Edited by Mark Harry (04/24/14 07:41 AM)


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: How large does your relector have to be to.... new [Re: Mark Harry]
      #6485087 - 04/24/14 08:21 AM

Quote:

And the skies were a lot darker from lack of all pollution!
M.




There are places in the US that are far enough from civilization that the skies are not affected by light pollution. And back then, smoke from wood and coal fires was a big problem..

Jon


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aatt
sage


Reged: 07/26/12

Loc: CT
Re: How large does your relector have to be to.... new [Re: Jon Isaacs]
      #6485102 - 04/24/14 08:40 AM

I know my 6" was not cutting it from my Orange zone which is why I went up to a 15". That being said transparency and light pollution are my limiting factors now.I just had a great night last week with the NGC's in Leo's hindquarters because transparency was good. On other "muddier" nights some of them are not detectable.

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