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The H400 can be completed with a 6-inch scope under dark skies, so you've got a pretty decent chance, I would think.

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The H400 can be completed with a 6-inch scope under dark skies, so you've got a pretty decent chance, I would think.

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I'm sorry but the six inch scope will have very limited visual use for the H-400. I like to see objects, not just detect them. Btw, that 12" scope has over 100% light gathering over an 8". 400% more than the 6". Aperture is everything when it comes to DSO observing.

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I would probably not go quite that far. A number of the open clusters and planetary nebulae in the Herschel 400 look quite nice in a six inch. Most galaxies won't show much detail, but they will be seen (and not just marginally "detected"). The larger the scope, the more you will see, but under fairly good conditions, even a six inch is more than up to the task of doing the Herschel 400. Out of the list, I culled about 150 of them as "notable" objects for my "best-of" deep-sky listing I used when writing observing reports for my Astronomy Club's newsletter. In fact, Jay Freeman has done the list with a considerably smaller scope than a six inch:

http://astro.isi.edu/reference/herschel.html

Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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The H400 can be completed with a 6-inch scope under dark skies, so you've got a pretty decent chance, I would think.

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I'm sorry but the six inch scope will have very limited visual use for the H-400. I like to see objects, not just detect them. Btw, that 12" scope has over 100% light gathering over an 8". 400% more than the 6". Aperture is everything when it comes to DSO observing.

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I would probably not go quite that far. A number of the open clusters and planetary nebulae in the Herschel 400 look quite nice in a six inch. Most galaxies won't show much detail, but they will be seen (and not just marginally "detected"). The larger the scope, the more you will see, but under fairly good conditions, even a six inch is more than up to the task of doing the Herschel 400. Out of the list, I culled about 150 of them as "notable" objects for my "best-of" deep-sky listing I used when writing observing reports for my Astronomy Club's newsletter. In fact, Jay Freeman has done the list with a considerably smaller scope than a six inch:

http://astro.isi.edu/reference/herschel.html

Clear skies to you.

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And to you, too sir. You're gonna need the darkest skies available to you. But no thank you to puny scopes for the H-400. I choose not to believe the 55mm refractor claim I read. I apologize in advance if that offends you and mean no disrespect, but that seems a little hard to believe given the limiting magnitude of such a teeny scope. That's all I'll say about it.

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Two eyes and a preference to use both

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And to you, too sir. You're gonna need the darkest skies available to you. But no thank you to puny scopes for the H-400. I choose not to believe the 55mm refractor claim I read. I apologize in advance if that offends you and mean no disrespect, but that seems a little hard to believe given the limiting magnitude of such a teeny scope. That's all I'll say about it.

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Well, again, the limiting magnitude of a telescope is not a hard and fast figure. It depends on a variety of factors from the quality to the design to the size of the central obstruction to the use of a star diagonal, and (the most important), the sensitivity of the person doing the observation and their experience. There are various formulae for calculating the limiting magnitude of telescopes, but I'm afraid that all they offer are "ballpark" figures. Depending on the situation, many can be easily off by up to two full magnitudes or so, especially if the observer is experienced and has very sensitive vision. Published references are also somewhat variable in what they claim for a magnitude limit. One reference (STARWARE by Phillip Harrington), gave the limiting magnitude of a 10 inch Newtonian as 13.8. This is claimed by the author to be a somewhat conservative estimate, but he also states that people might better this by half a magnitude or more.

In practice, however, Harrington has made something of an understatement here. I have done studies of how faint I can go with my own equipment under a variety of conditions and the results were surprising. With my own 10 inch Newtonian, I have gone a little past 15th magnitude on a good dark night using some photometrically calibrated star fields as references. Some nights I won't go quite that faint, but on most halfway decent dark nights from my rural ZLM 6.5-6.8 site, I can usually at least get to 15th magnitude on a fairly regular basis. If I use one formula which does give a number of, say, 15.3 for a 10 inch aperture, a 55mm (2.17 inch) aperture should be able to show stars down to around 12th magnitude or so. In fact, some observers have done limiting magnitude research with various apertures and note that a 2 inch aperture has reached 12.1 or even 12.2 (see AMATEUR ASTRONOMER'S HANDBOOK, by J.B. Sidgwick, p. 25-29). Indeed, one British observer reached 11.9 in only a 1.7 inch aperture (W.H. Seavenson). To do this, one must use moderate to high power, be properly dark adapted, and be experienced with the use of averted vision to push things to their absolute limits. However, from my 40 years of experience, I see no overriding reason why I should not believe that a 55mm aperture could reach 12th magnitude. In a cheap 80mm f/5 "Short tube" refractor, I could just barely see the 13th magnitude star sitting next to the Ring Nebula, which again is a little past what my little "off the cuff" formula I use gives for that scope's magnitude limit (12.8).

Now, as to viewing the Herschel 400 list in such a small aperture, as Jay notes in the article, the precise magnitudes of a number of the objects on the list are *not* well established (some don't have magnitude measurements or estimates at all). Thus, many are very probably brighter than 12th magnitude. Jay is one of the more established amateur astronomers in the U.S. and is a long-time contributor to the articles and reviews here on Cloudynights.com. I believe that, while he may or may not have seen quite all of them, he definitely saw *most* of the Herschel 400 objects in his little 55mm aperture. Whether he saw quite all of them is perhaps open to question, but as I have seen all of them in an 8 inch (Herschel Award holder #12), I can testify that many of them are fairly easy and many would pose little challenge to a 4 inch aperture under halfway decent conditions. In fact, those who observe under very good conditions probably will be able to get the Herschel 400 award using *only* a four inch, although I would still recommend using a six inch to give the observer a little "breathing room". Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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Is it possible to complete Hersecell 400 list using 8" scope under mag 5.5 skies???

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reflector74 posted:

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And to you, too sir. You're gonna need the darkest skies available to you. But no thank you to puny scopes for the H-400. I choose not to believe the 55mm refractor claim I read. I apologize in advance if that offends you and mean no disrespect, but that seems a little hard to believe given the limiting magnitude of such a teeny scope. That's all I'll say about it.

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Well, again, the limiting magnitude of a telescope is not a hard and fast figure. It depends on a variety of factors from the quality to the design to the size of the central obstruction to the use of a star diagonal, and (the most important), the sensitivity of the person doing the observation and their experience. There are various formulae for calculating the limiting magnitude of telescopes, but I'm afraid that all they offer are "ballpark" figures. Depending on the situation, many can be easily off by up to two full magnitudes or so, especially if the observer is experienced and has very sensitive vision. Published references are also somewhat variable in what they claim for a magnitude limit. One reference (STARWARE by Phillip Harrington), gave the limiting magnitude of a 10 inch Newtonian as 13.8. This is claimed by the author to be a somewhat conservative estimate, but he also states that people might better this by half a magnitude or more.

In practice, however, Harrington has made something of an understatement here. I have done studies of how faint I can go with my own equipment under a variety of conditions and the results were surprising. With my own 10 inch Newtonian, I have gone a little past 15th magnitude on a good dark night using some photometrically calibrated star fields as references. Some nights I won't go quite that faint, but on most halfway decent dark nights from my rural ZLM 6.5-6.8 site, I can usually at least get to 15th magnitude on a fairly regular basis. If I use one formula which does give a number of, say, 15.3 for a 10 inch aperture, a 55mm (2.17 inch) aperture should be able to show stars down to around 12th magnitude or so. In fact, some observers have done limiting magnitude research with various apertures and note that a 2 inch aperture has reached 12.1 or even 12.2 (see AMATEUR ASTRONOMER'S HANDBOOK, by J.B. Sidgwick, p. 25-29). Indeed, one British observer reached 11.9 in only a 1.7 inch aperture (W.H. Seavenson). To do this, one must use moderate to high power, be properly dark adapted, and be experienced with the use of averted vision to push things to their absolute limits. However, from my 40 years of experience, I see no overriding reason why I should not believe that a 55mm aperture could reach 12th magnitude. In a cheap 80mm f/5 "Short tube" refractor, I could just barely see the 13th magnitude star sitting next to the Ring Nebula, which again is a little past what my little "off the cuff" formula I use gives for that scope's magnitude limit (12.8).

Now, as to viewing the Herschel 400 list in such a small aperture, as Jay notes in the article, the precise magnitudes of a number of the objects on the list are *not* well established (some don't have magnitude measurements or estimates at all). Thus, many are very probably brighter than 12th magnitude. Jay is one of the more established amateur astronomers in the U.S. and is a long-time contributor to the articles and reviews here on Cloudynights.com. I believe that, while he may or may not have seen quite all of them, he definitely saw *most* of the Herschel 400 objects in his little 55mm aperture. Whether he saw quite all of them is perhaps open to question, but as I have seen all of them in an 8 inch (Herschel Award holder #12), I can testify that many of them are fairly easy and many would pose little challenge to a 4 inch aperture under halfway decent conditions. In fact, those who observe under very good conditions probably will be able to get the Herschel 400 award using *only* a four inch, although I would still recommend using a six inch to give the observer a little "breathing room". Clear skies to you.

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For a "little beathing room" for the H-400, I recommend a 12" minimum aperture. Surfact brightnesses are often significantly less than the magnitudes stated. Using 2" for the H-400 is a quick way to kill the interest of any novice observer. For the Messier objects, 8" is a nice start.

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Two eyes and a preference to use both

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The original question was CAN IT BE DONE. The consensus answer is clearly yes on the 8" scope, so-so on the 5.5 mag skies with help from darker skies on some objects.

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From the Foreword of Observe The Herschel Objects, by the Ancient City Astronomy Club :

"We decided that the proposed Herschel Club should consist of enough objects to present a distinct challenge, yet still be within range of amateurs who possessed only modest equipment and were affected by modern light-pollution problems."

"...most of these observations were made with the city of St. Augustine, with approximately 14,000 population, in average to good sky conditions. Faintest naked eye star visible at the zenith was about 5.5 magnitude in most cases."

So, agreed - Go for it! I did most of mine using a 10", but there were few objects that I would have called really difficult. Some showed minimal detail, etc., but were not overly difficult. My biggest concern was that it seemed at times Herschel considered "two stars a cluster make"!

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Len Philpot
len@philpot.org ><> http://pages.suddenlink.net/lenphilpot

14.5" TeleKit, 8" Hardin DSH, Orion ST80, Orion 10x70, Celestron 8x40 ... How long 'til the next TSP...?

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For a "little beathing room" for the H-400, I recommend a 12" minimum aperture. Surfact brightnesses are often significantly less than the magnitudes stated. Using 2" for the H-400 is a quick way to kill the interest of any novice observer. For the Messier objects, 8" is a nice start.

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Such discouragement is highly unlikely, as the Herschel 400 is *not* a intended as a project for the novice observer. A 2 inch attempt at the list is a "challenge" and not a recommendation as to the minimum aperture needed. Even doing the Messiers may not necessarily be for the rank beginner, although it is probably the first deep-sky observing project which the relative newcomer to amateur astronomy will probably attempt. The Messiers can usually be done with a three inch with little trouble, and from a dark site, over 30 of them are visible *to the unaided eye*. As for a 12 inch, that is definitely not required to get all of the Herschel 400 or to observe detail in many of them. With the Herschel II project, a 12 inch *might* be a good recommendation, although the list can be done with a 10 inch (I finished that project with my own 10 inch about two years ago). Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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I'm sorry but the six inch scope will have very limited visual use for the H-400. I like to see objects, not just detect them. Btw, that 12" scope has over 100% light gathering over an 8". 400% more than the 6". Aperture is everything when it comes to DSO observing.

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Here's a relevant quote from the Introduction to the Herschel 400, All the objects can be seen in a six-inch or larger telescope. All descriptions have been taken from observations by two or more members of the A. C. A. C.; most of these observations were made from within the city of St. Augustine, with approximately 14,000 population, in average to good sky conditions. Faintest naked eye star visible at the zenith was about 5.5 magnitude in most cases.

As should be clear from the introduction, it is possible to observe these objects with small aperture from moderately dark skies. It's been done and, ignorable comments aside, there's no reason it can't be done, again. Of course, regardless of the aperture one uses for deep-sky observing, a dark sky is the key to better views.

Regards,

Bill in Flagstaff

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Grand Canyon Adventure
Lowering the Threshold

18" Obsession
4.5" Meade 4500
10x50 Swift Audubon

Cosmic Voyage

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So, agreed - Go for it! I did most of mine using a 10", but there were few objects that I would have called really difficult. Some showed minimal detail, etc., but were not overly difficult. My biggest concern was that it seemed at times Herschel considered "two stars a cluster make"!

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I didn't run into this with any of the Herschel 400 clusters, but on the Herschel II's, there were a few which bordered on "two stars make a cluster". In fact, there is one cluster on the list which simply *does not exist* (NGC 2253). There was another one with maybe 4 or 5 stars in it (and none were all that bright), but M73 is that way, so I suppose we should expect this as Herschel got to, "the bottom of the barrel". Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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