Akarsh Simha
member
Reged: 03/27/07
Posts: 61
Loc: Bangalore, India
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Hi.
One of my friends is very keen on buying a 25x100 binocular for comet hunting.
1. Is this an advisable choice?
2. What are the best deals available for a 25x100?
3. What is the limiting magnitude of diffuse DeepSky objects through 25x100?
4. What are the pros and cons of a binocular over a telescope for a task of this sort?
5. Can you refer me to some success stories of binocular comet hunting / hunters?
Thank you very much, in advance. :-)
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Regards,
Akarsh
http://bas.org.in
8" f/8 Equatorial
17.5" Discovery Dob in the making...
Nikon FM10 Camera
Nikon Nikkor 50mm f/1.8 lens
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Mark9473
Carpal Tunnel
Reged: 07/21/05
Posts: 2695
Loc: 51°N 4°E
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Hello Akarsh, welcome to the forum!
Several people will no doubt answer in full detail on your specific questions, and a lot (if not all) of what you ask is already available in the 'best of' thread in this forum.
I just want to reply that for the purpose of comet hunting, I personally would look long and hard at the new 20x110 to come out of China. The increased exit pupil diameter when compared to a 25x100 would help in finding low-surface-brightness diffuse objects.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63
WO Megrez II 80 FD + Baader 90° T2 Amici
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Phillip Creed
Idiot Seeking Village
Reged: 07/25/06
Posts: 1032
Loc: NE Ohio
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Akarsh,
I would second Mark's opinion that a pair of 20x110s would be better for comet hunting than a set of 25x100s...but then there's weight.
A set of 25x100s weighs typically around 10 lbs. A set of the Kunming Series 8 20x110s will run around 16 lbs, making mounting a lot more expensive. The difference in price between the binoculars themselves, though, isn't that much, around $200 U.S.
Clear Skies,
Phil
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"Why suffer from insanity when you can revel in it?"
Wilderness Center Astronomy Club member since 1995
ICQ Comet Observer Code: CRE01
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12565
Loc: Cumberland, R I , USA42N71.4W
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Quote:
The increased exit pupil diameter when compared to a 25x100 would help in finding low-surface-brightness diffuse objects.
While I just got done answering another post this morning by stating maximum exit pupil was not the way to achieve maximum LM, I'd have to agree about increasing exit pupil for this purpose.
You are after faint extened objects and this is much different than trying to achieve maximum LM. This is all about gathering the faintest light, providing enough contrast and providing the brightest image.
With 25x100 binoculars I have seen close to mag12.5 stars and Sb 15.0 under mag 5.8 skies.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Phillip Creed
Idiot Seeking Village
Reged: 07/25/06
Posts: 1032
Loc: NE Ohio
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Quote:
3. What is the limiting magnitude of diffuse DeepSky objects through 25x100?
Akarsh,
From a really dark sky (NLM ~ 7.0 or better), you should be able to see deep-sky objects down to about 11th- or 12th-magnitude.
From personal experience, I've seen the faintest members of Markarian's Chain (mag 12.4) with a set of 25x100s under a dark sky in Ohio. Plus, India's got plenty of spots that are significantly darker than the best Ohio skies.
Clear Skies,
Phil
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"Why suffer from insanity when you can revel in it?"
Wilderness Center Astronomy Club member since 1995
ICQ Comet Observer Code: CRE01
*****
16" f/4.5 Truss Dobsonian (FOR SALE!!)
Orion 120mm ST Refractor
23mm Axiom LX
13mm Nagler Type 6
9mm Nagler Type 6
1.75X Siebert Barlow
*****
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Mok Chong Kin
newbie
Reged: 01/12/06
Posts: 55
Loc: Macau
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For comet hunting , the new China made 28x110 is better than the 20x110 and 25x100 .
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Mok Chong Kin
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12565
Loc: Cumberland, R I , USA42N71.4W
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We've had similar discussion in the past referencing the differences between limiting magnitude of objects and surface brightness of extended objects. This discussion is captured thru our best of threads:
SURFACE BRIGHTNESS
The ability to Observe Deep Sky Objects will not always be indicated by the magnitude of the objects. For extended objects, Surface Brightness comes into play. Visual magnitude (Mv) of a deep sky "extended" object is almost always NOT the appropriate measure of how faint an extended object will appear. Determining which faint extended objects, such as galaxies, might be observed is complicated by the fact that books generally list the visual magnitude (Mv). That would be how bright the object would appear if all the light could be compressed in a small spot only 1 sq arcmin. More often, a better indicator of whether or not the object might be seen is Surface Brightness (Sb), which is usually much fainter than Mv, and even that can vary. Read this brief explanation.
See a preface on Surface Brightness in
Deep sky limits on 25x100s
Some Notes on Surface Brightness
If you have an object that is mag 8 visually, Mv=8.0 (in a 1 arcmin area) and you spread the light out over an area of 10x10 arcminutes, or an area of 100 arcmin sq, then the Surface Brightness would drop by a factor of 100x from the visual magnitude. That equates to a drop of 5 magnitudes. Surface brightness and visual magnitude are very different. A mag 8 object that is 10x10 arcminutes in area would have a surface brightness of Sb 13.0. In all likelyhood it would be slightly brighter towards the middle and the outer edges would not be visible.
Let's assume a comet is mag 11, Mv=11.0. Let's also assume the comet is round and is about 5 arcmin in diameter (has an area of 19.6 sq arcmin). Each time the object is speard out 2.5x greater area, it becomes 1 magnitude fainter by surface brightness. A comet that is 5 arcmin across has a surface brightness that is about 3.5 magnitude fainter than its visual magnitude. Therefore it would have Sb~=14.5, near the threshold of a 25x100 binocular under a mag 5.5 sky.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Wes James
Carpal Tunnel
Reged: 04/12/06
Posts: 2457
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Soooo... given a choice- would a 20x110- or 28x110 be the better choice? Obviously, I would certainly think the 25x100's would be outclassed by either of the others due to the increased objective size, am I correct?
I am in the decision making process myself- trying to decide between the 20's & the 28's... trying to determine if there's any situation the 20x110's would have an advantage over the 28's??
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Wes
Atlantic Beach, FL
Some bino’s from Miyauchi 5x32 Binon's up through Garrett 20x110 Signature's,
Some telescopes from a Stellarvue 80mm NHNG up through a couple of 8” reflectors…
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KennyJ
Reged: 04/27/03
Posts: 10142
Loc: Lancashire UK
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< trying to determine if there's any situation the 20x110's would have an advantage over the 28's?? >
Hi Wes ,
The 20x is actually 20 grams heavier than the 28x , so for those who prefer extra weight , it looks like the 20x is the one for them ! :-)
Slightly more seriously , I'm sure there will be some people and situations favouring the larger exit - pupil , wider field of view , longer eye relief , less critical collimation requirements and reduced visible C.A associated with the lower magnification versions .
Specifically for comet hunting , I'm not sure which would be the more suited .
Kenny
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Two eyes and a preference to use both
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
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Various eyepieces barlows tripods mounts etc.
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Rich N
Post Laureate
Reged: 09/22/04
Posts: 5311
Loc: San Francisco Bay Area, Calif...
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Hi Akarsh,
Don Machholz has discovered at least 10 comets. He has done it by direct observation. He uses a telescope.
I'm not sure if he has used binoculars for comet hunting.
Don's website:
http://us.geocities.com/donmachholz/
Rich
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hallelujah
Carpal Tunnel
Reged: 07/14/06
Posts: 1659
Loc: Colorado Rocky Mt. High
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Akarsh, Rich,
Others have used binoculars to find comets....
http://www.meteorobs.org/maillist/msg06919.html 
Speaking for myself, the best deals and quality come from Garrett Optical. I am looking forward to receiving a GO Gemini 25x100mm WP-CF in the next couple of weeks. 
Edited by hallelujah (06/09/07 12:57 PM)
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Rich N
Post Laureate
Reged: 09/22/04
Posts: 5311
Loc: San Francisco Bay Area, Calif...
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Thanks very much!
Rich
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Mok Chong Kin
newbie
Reged: 01/12/06
Posts: 55
Loc: Macau
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I think the best instrument for comet hunting between 50s and 60s was the Zeiss 25x100 with 90 degrees eyepieces.( ( Somet 25x100 ), I also use Russian 20x110 . German 25x100 and China 30x120 .http://www.cloudynights.com/photopost/showgallery.php?cat=3104&password=paddakob&thumb=1
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Mok Chong Kin
Edited by Mok Chong Kin (06/08/07 09:22 PM)
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hallelujah
Carpal Tunnel
Reged: 07/14/06
Posts: 1659
Loc: Colorado Rocky Mt. High
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Akarsh,
This was posted not too long ago:
http://www.skyhound.com/sh/comets.html
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Pentax 12x50mm PCF WP II FMC/WP/FP
Pentax 16x60mm PCF WP FMC/WP/FP
Pentax 20x60mm PCF WP II FMC/WP/FP
Orion 12x63mm Mini Giant FMC/JAPAN
Orion 15x70mm Little Giant II FMC/JAPAN
Orion 16x80mm Giant FMC/JAPAN
Orion 20x70mm Little Giant II FMC/JAPAN
Orion 30x80mm MEGAView FMC/JAPAN
Barska 30x80mm X-Trail LW FC
Burgess Optical Series II 20x90mm FMC/WP/FP
Handel's Messiah**Hallelujah! For the LORD God Omnipotent Reigneth
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Jim Rosenstock
Carpal Tunnel
Reged: 07/14/05
Posts: 2394
Loc: MD, south of the DC Nebula
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Akarsh,
By "comet hunting", does your friend mean searching the skies for undiscovered comets, or just observing known comets?
Either way, big binoculars are a good way to go, I think.
But for scanning the skies for undiscovered comets, I think a very high-end (i.e. expensive!) pair of big binos is needed. You see, the "bargain" 25X100s, while they provide some wonderful views, tend to be pretty "soft" around the edges. That is, stars at the edge of the field of view will appear to be "comets", not acceptable for methodically scanning large areas of the sky for new visitors.
I hope your friend understands that VERY few comets are discovered by human observers any more....most are now picked up first by automated observing programs. Still, there are a few human successes every year...generally by people who obsessively spend hundreds of hours searching each year.
Of course, he'll get quite a few beautiful views if he embarks on this program, whether or not he ever gets to put his name on a comet!
Clear skies,
Jim
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QUESTION AUTHORITY!
"errr....sez who??"
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starramus
Pooh-Bah
Reged: 09/01/04
Posts: 1124
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The only successful comet hunting I am aware of with binos was with the Fujinon 25X150s. But then you are staring at insurmountable cost. I think it was Hyakutake that was discovered with these.
I have been known to be wrong though. 
Regards and clear skies,
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hallelujah
Carpal Tunnel
Reged: 07/14/06
Posts: 1659
Loc: Colorado Rocky Mt. High
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star,
Did you read the link I posted above?
"COMET HUNTING NOTES FROM JAN. 1998: Of the last 100 visual comet discoveries, 28 were made by amateurs using binoculars. The smallest pair of binoculars used was 7x35's by William Bradfield in 1980 to find a magnitude-six comet. Three were the 80mm size while six finds were made using binoculars with objectives of 110-120 mm. Four finds were made with my homemade binoculars (130mm). And half (14) of all binocular comet discoveries were made with 150mm (6-inch) binoculars". 
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Pentax 12x50mm PCF WP II FMC/WP/FP
Pentax 16x60mm PCF WP FMC/WP/FP
Pentax 20x60mm PCF WP II FMC/WP/FP
Orion 12x63mm Mini Giant FMC/JAPAN
Orion 15x70mm Little Giant II FMC/JAPAN
Orion 16x80mm Giant FMC/JAPAN
Orion 20x70mm Little Giant II FMC/JAPAN
Orion 30x80mm MEGAView FMC/JAPAN
Barska 30x80mm X-Trail LW FC
Burgess Optical Series II 20x90mm FMC/WP/FP
Handel's Messiah**Hallelujah! For the LORD God Omnipotent Reigneth
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starramus
Pooh-Bah
Reged: 09/01/04
Posts: 1124
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No I hadn't read the link. I would imagine that the other finds ( albeit the 7X35 discovery was pretty darn amazing) were of insignificant comets. None on the order of a Hyakutake. Probably why i hadn't heard of the binocular discoveries. Thanks for the link.
Regards and clear skies,
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coopman
Pooh-Bah
Reged: 04/23/06
Posts: 1209
Loc: South Louisiana
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There is a comet hunting discussion group on Yahoo. Might be worthwhile to get their input on this.
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Regards,
Clay
"The heavens declare the glory of God; the skies proclaim the work of his hands." Psalms 19:1
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Jim Rosenstock
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Reged: 07/14/05
Posts: 2394
Loc: MD, south of the DC Nebula
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Quote:
No I hadn't read the link. I would imagine that the other finds ( albeit the 7X35 discovery was pretty darn amazing) were of insignificant comets.
Insignificant comets?:?? 
A contradiction in terms!
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QUESTION AUTHORITY!
"errr....sez who??"
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