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Bound and determined : Horsehead thru a ten..BUT..

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#26 Sarkikos

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Posted 22 November 2012 - 04:38 PM

Thomas,

The brightness of IC434 is similar to that of the Veil.


I beg to differ. It must be considerably fainter. The Veil (eastern half) is easy as pie in any of my telescopes, even unfiltered, but I've never seen a hint of IC 434, despite looking for it on some very good nights in the past.


What you say matches my experience. I've seen all three major parts of the Veil, many times in many scopes - 80mm to 300mm - at my yellow zone site. Not difficult at all. I've tried several times to see IC 434 and B33 here at the same site and have failed ... or have given up after trying for awhile, which amounts to the same thing. I have heard that if you can't see IC 434, don't try for B33. Makes sense to me.

In the meantime I've observed about 900 other faint and fuzzy objects at the same site.

I'd rather spend an hour or so observing a dozen other objects I've never seen before than trying once again to see this one object I've never seen before. Eh... Maybe one day. :shrug:

:grin:
Mike

#27 Astrojensen

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Posted 22 November 2012 - 05:38 PM

I have heard that if you can't see IC 434, don't try for B33. Makes sense to me.



Uh, yeah, that makes sense... A lot of it, actually.

:grin:


Clear skies!
Thomas, Denmark

#28 Sarkikos

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Posted 22 November 2012 - 08:04 PM

So actually the objective should be to see IC 434 ... and then try to see a notch along its eastern edge. That notch might be B33.

It's on my list, but so are many other objects.

Mike

#29 Bill Weir

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Posted 23 November 2012 - 12:16 AM

Carol's sketch with that lovely reference triangle is perfect as a guide in looking for this elusive dark nebula. That little angled trio of stars on its western point (left) are always what I show people as a guide in looking for B33. The faintest of them points right at the snout. You can still see these stars even with a NBP, H-Beta or Ultra Block in place. I suggest to people to forget about everything at first and only focus on those stars and where they are pointing. Often that's all it takes to get people to see B33. You have to be looking exactly in the right spot. For a best view it also requires observing it with an eyepiece that gives you an appropriate exit pupil to work with an H-Beta filter. This is from 4-7mm. Match all of this and I've found seeing B33 isn't as difficult as people think. I've had total newbies seeing it from not all that perfect conditions.

Story time;

In early September I was at a star party at a fairly nice location. Late in the night I wandered over to someone I'd met earlier to look through his 16" Starmaster. A bunch of them were looking at the "Flame" as Orion had finally risen above a ridge to the east. I asked if they minded if I had a look for the Horse Head. They all said sure as most had never seen it. Because I knew where to look although it was faint I could clearly make out the dark notch in the faint band of IC 434. Seeing that the eyepiece was a 13 Ethos I asked if anyone had a 1.25 H Beta. "No". So, "I'll be right back" and wandered off to get mine. With the H Beta in place B33 was then much easier to see and showing them those pointer stars all there could make it out although most were having difficulty. Then I started to think about the scope we were using. "What's the focal ratio?" "4.5" So that meant the exit pupil was only about 3mm. "Anyone got a 25-30mm 1.25" eyepiece?" "No" "I'll be right back." and went and got my 30 mm Orion Ultrascopic and plopped that along with the H Beta into the focuser. The change was remarkable. IC 434 had a hard N-S straight edge to the east side and the western edge feathered off to the west. Etched into the eastern edge like a chess piece was the Horse Head completeing the photographic view. My job there was done. For the rest of the time I was at that star party, every time I ran into that scope owner he thanked me for giving him the most memorable view he'd ever had with his scope.

This is not an object that needs magnification as much as it needs appropriate exit pupil. With my little ED 80 refractor from my reasonably dark backyard I've detected it on a perfect winters night.

Bill

#30 Sarkikos

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Posted 23 November 2012 - 01:02 AM

The bottom line is: If you can't see IC 434, you won't see B33.

Mike

#31 bassplayer142

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Posted 23 November 2012 - 02:22 AM

Thanks carol for the amazing sketch. I can't wait to give this a go with a near identical setup at home. Likely a tad more light polluted but will give a great representation.

#32 JayinUT

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Posted 23 November 2012 - 03:21 AM

Stephen Waldee has an excellent discussion on sketching the horse head located Here. a copy of and explanation of my observation using my XT10 is there from a few years ago. Stephen has returned me to focusing on the details more.

#33 Achernar

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Posted 23 November 2012 - 08:05 AM

I have seen it through a 10-inch, but it's faint and very indistinct even with a H-beta filter. It's easier to see with my 15-inch, but unless skies are superbly dark, it's still indistinct and take real effort to make out the horsehead shape. It's much, much easier with a 15 or l8-inch telescope even from a very dark area. One more thing, if the nearby nebula NGC-2024 of Flame Nebula is hard or impossible to see, you can be sure you will not be able to see IC-434 and B-33 that night.

Taras


#34 ensign

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Posted 23 November 2012 - 10:55 AM

I'll throw my $.02 in: having searched for the HH using a 10", I finally did manage to _detect_ it with averted vision on a very clear night under a very dark sky using an Orion H Beta filter and a Nagler type 4 17mm. I think the 3.6 mm exit pupil may have helped.

Does anyone have thoughts on an ideal exit pupil for viewing the Horsehead?

#35 Sarkikos

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Posted 23 November 2012 - 10:57 AM

Taras,

I routinely see the Flame Nebula (2024) from my yellow zone site. I'd say it's about as easy as seeing all three sections of the Veil, maybe even a little easier. The real test for the possibility of seeing B33 is IC 434.

But yes, I'd say that if you can't see the Flame, you definitely won't see IC 434 and B33. Give it up and focus on other objects that make more sense for that night.

Personally, I have very limited time at my dark site - such as it is - and I don't won't to waste time looking for something that I have zero chance of seeing on a particular night.

Mike

#36 Sarkikos

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Posted 23 November 2012 - 10:59 AM

Mike (ensign),

Barbara Wilson's link from the second post in this thread will give you a good idea of what you need.

Mike

#37 Dave Mitsky

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Posted 23 November 2012 - 11:56 AM

A 5mm exit pupil, à la Barbara Wilson's article, really seems to enhance views of B33, in my experience. Using an ultra-widefield eyepiece is probably not the best choice in this case.

Dave Mitsky

#38 Sarkikos

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Posted 23 November 2012 - 12:45 PM

For an f/5 scope, a 25mm eyepiece should be about right. I've actually setup a turret focuser with a 25mm UO Ortho, 25mm Kellner and 25mm Sterling Plossl in order to see the Horsehead with my 10" f/4.8 Dob. Still no go. Apparently what's needed is a dark site on an exceptionally transparent night, exceedingly well dark-adapted eyes and plenty of patience. I've seen many, many very faint things at my yellow zone site,so I know how to ferret out the difficult stuff, but so far not B33. I suppose if I travel the 600 miles to my nearest blue/black site, it would be much easier ... except for the time, gas money and effort involved.

Mike

#39 Bill Weir

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Posted 23 November 2012 - 12:57 PM

Does anyone have thoughts on an ideal exit pupil for viewing the Horsehead?


I already mentioned it in my response but will link to the Lumicon page that halfway down shows the suggestions of exit pupils for their filters.
http://www.lumicon.c...id=1&cn=Filters

Required exit pupil is somewhat dependant on how dark the location is.

I've seen B33 many times from a location where the SQM reading only gets to 21 to 21.31, ie my back yard.

Bill

#40 Carol L

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Posted 23 November 2012 - 02:01 PM

Thanks carol for the amazing sketch. I can't wait to give this a go with a near identical setup at home. Likely a tad more light polluted but will give a great representation.


You're welcome! :rainbow:

BTW, if your ground is snow-covered when you get a chance at the Horse Head, the reflected stray light can be bothersome - be sure to shield it from your eyes with a dark cloth or something similar. It also helps to make sure the eyepiece is kept fog free - put it in an inside pocket to warm it up, or use an anti-dew strip if you've got one.

Good Luck!! :grin:

#41 Dave Mitsky

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Posted 23 November 2012 - 02:03 PM

..a location where the SQM reading only gets to 21 to 21.31, ie my back yard.


Bill,

I wonder how many of us would sell our souls to have a nearby 21.3 SQM site, let alone in our backyards. ;)

#42 Sarkikos

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Posted 23 November 2012 - 02:44 PM

Yeah, only 21 to 21.31. I'd have to travel six hours for that.

:roflmao:
Mike

#43 GlennLeDrew

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Posted 23 November 2012 - 06:23 PM

There is probably no one 'ideal' exit pupil, for B33 or any object. The relevant factors are object size, contrast against the sky and aperture, all of which play a role at all times. For any given object:

- A darker sky allows a larger exit pupil. This is because with more contrast the object need not be magnified as much.

- A larger aperture allows a larger exit pupil. This is because for unit magnification the image is brighter.

A light bucket could permit the largest exit pupil, while a small scope may necessitate a smallish pupil. In the latter case, the lesser light grasp necessitates a higher magnification per unit aperture. The overall dimmer view will necessitate more thorough dark adaption and sheilding from ambient light.

#44 KidOrion

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Posted 23 November 2012 - 08:07 PM

..a location where the SQM reading only gets to 21 to 21.31, ie my back yard.


Bill,

I wonder how many of us would sell our souls to have a nearby 21.3 SQM site, let alone in our backyards. ;)


*raises hand, whistles*

#45 Carol L

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Posted 24 November 2012 - 12:14 AM

The discussion on exit pupils has got me wondering something about my two 26mm ep's.

The first one is a 1.25" Meade Super Plossl with a 50° AFOV and a 42.6' TFOV.
The other one is the 2" QX that came with my 16" Lightbridge - it has a 70° AFOV and a 59.7' TFOV.
Both give 70x magnification with the f/4.5 16LB.

According to the exit pupil formula, a 26mm ep has an exit pupil of 5.77 - but i'm wondering if the difference in TFOVs (and eyepiece size) should also be taken into consideration when choosing an eyepiece for the Horse Head. It seems logical to me that a wider TFOV ep would allow more light in, regardless of the exit pupil formula - or am i overthinking this?

#46 David Knisely

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Posted 24 November 2012 - 01:49 AM

I'll throw my $.02 in: having searched for the HH using a 10", I finally did manage to _detect_ it with averted vision on a very clear night under a very dark sky using an Orion H Beta filter and a Nagler type 4 17mm. I think the 3.6 mm exit pupil may have helped.

Does anyone have thoughts on an ideal exit pupil for viewing the Horsehead?


I generally like exit pupils from about 5 mm to 2.5 mm for viewing the Horsehead. 4 mm tends to be something of a "sweet spot", but it depends on what you want to view. I got a great view one night in my 14 inch f/4.6 Newtonian at 52x (6.8mm exit pupil) using the H-Beta filter, when I could see both the Horsehead and the Flame Nebula at the same time in my 36mm Hyperion Aspheric Eyepiece (about an 80' arc true field). I liked the view of the Horsehead itself better at 79x (4.5 mm exit pupil) or 104x (3.4 mm exit pupil), but it was nice to see the two nebular complexes at the same time with lots of room to spare. Clear skies to you.

#47 Tony Flanders

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Posted 24 November 2012 - 05:24 AM

The discussion on exit pupils has got me wondering something about my two 26mm ep's.

The first one is a 1.25" Meade Super Plossl with a 50° AFOV and a 42.6' TFOV.
The other one is the 2" QX that came with my 16" Lightbridge - it has a 70° AFOV and a 59.7' TFOV.
Both give 70x magnification with the f/4.5 16LB.

According to the exit pupil formula, a 26mm ep has an exit pupil of 5.77 - but i'm wondering if the difference in TFOVs (and eyepiece size) should also be taken into consideration when choosing an eyepiece for the Horse Head. It seems logical to me that a wider TFOV ep would allow more light in, regardless of the exit pupil formula - or am i overthinking this?


Logic says that the eyepiece with the smaller field of view should help you see the Horsehead.

As you say, the one with the wider field of view takes in more light -- from the surrounding nebula and stars. Both eyepieces take in the same amount of light from the area right around the Horsehead, which is tiny and takes up only the part of the field that's common to both eyepieces.

So the wider field of view means that the fraction of light devoted to the object you actually want to see is smaller. In theory, the wider field of view might reduce your dark adaptation and make the Horsehead harder to see. But in practice I have never seen such an effect. Not unless a very bright star happens to stray into the field of view of the eyepiece with the wider field of view.

#48 stmguy

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Posted 24 November 2012 - 07:45 AM

I know sometimes a Barlow helps with contrast, anyone have any thoughts on this for viewing the Horse head ?
Norm

#49 Sarkikos

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Posted 24 November 2012 - 09:57 AM

Maybe better to keep as much glass out of the optical train as possible when you're looking for something as faint as IC 434 and B33. Just use a simple glass eyepiece with a relatively narrow AFOV that will give you an optimum exit pupil. Makes sense to me.

Probably the most important factor is having skies that are dark enough and transparent enough.

Mike

#50 BillFerris

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Posted 24 November 2012 - 10:59 AM

According to the exit pupil formula, a 26mm ep has an exit pupil of 5.77 - but i'm wondering if the difference in TFOVs (and eyepiece size) should also be taken into consideration when choosing an eyepiece for the Horse Head. It seems logical to me that a wider TFOV ep would allow more light in, regardless of the exit pupil formula - or am i overthinking this?


As long as the object you wish to observe is fully contained within the field of view, different eyepieces used in the same telescope will deliver the same intensity light packet from that object. In other words, the object will have the same apparent integrated brightness, regardless of the exit pupils and true fields produced by the eyepieces.

Since B33 is a dark nebula, it does not have an integrated magnitude, per se. The Horsehead is lower in surface brightness than the surrounding sky and even darker than faint IC 434, the nebula against which B33 is seen. At about 4' by 4' in size, a magnification of 75X will give B33 an apparent size of 5 degrees in the eyepiece. This is more than large enough for the eye to discern the Horsehead as an extended object. 30X magnification will present it as 2 degrees in apparent size, which is still large enough for the dark-adapted eye to discern and is probably a more useful magnification for small apertures.

With 1.9 magnitude Alnitak just one-half degree to the north, a modest true field of view offers the advantage of preventing the bright star from limiting your dark adaptation. I've found a true field of about 45 arcminutes works quite well to frame the B33 & IC 434 complex for viewing. I used a Meade 13.8mm SWA eyepiece with my old 10 inch Meade Starfinder and a 22mm Nagler T4 with the 18 inch Obsession.

Bill in Flag






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