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Observing >> Deep Sky Observing

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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Starman1]
      #5538638 - 11/25/12 12:15 PM

In this case, evil may be in the eye of the beholder. I enjoy observing the Moon. There's not much else worth looking at in my light-polluted, glare-ridden, scotophobic neighborhood. But I also enjoy going to my dark site as often as I can.

At least the Moon can give you something to look at when you can't look at the faint stuff.

Mike


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GlennLeDrew
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Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Starman1]
      #5538651 - 11/25/12 12:25 PM

Same-focal-length eyepieces having differering apparent fields are much like naked eye viewing through paper towel tubes of differing length. The longer tube constricts the field, blocking potentially interfering sources. In the case of ye olde Horsehead, a narrower FOV puts blazing Alnitak out of the picture.

If there are no particularly bright stars about, a larger AFoV can be useful. Particularly if the object is large, and when no particularly offending stars are in the area, a larger 'frame' places more sky around the target, facilitating edge detection. And there is more room for nodding the scope, this technique taking advantage of the visual system's great sensitivity to object movement.

Here's another potential benefit of a larger AFoV, as it appears to me after many years of observing. When using averted vision, while directing my gaze away from the target I seem to prefer not having the field stop anywhere close to my fovea. Strange as it may seem, a vast expanse of sky glow across my field of vision is for some reason better than a sharp discontinuity to black nearby. This might result from the naked eye experience, where the dome of the sky largely fills my field of vision, particularly when gazing near overhead.


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Astrojensen
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Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: GlennLeDrew]
      #5538669 - 11/25/12 12:36 PM

Quote:

Here's another potential benefit of a larger AFoV, as it appears to me after many years of observing. When using averted vision, while directing my gaze away from the target I seem to prefer not having the field stop anywhere close to my fovea. Strange as it may seem, a vast expanse of sky glow across my field of vision is for some reason better than a sharp discontinuity to black nearby. This might result from the naked eye experience, where the dome of the sky largely fills my field of vision, particularly when gazing near overhead.




I have found the same thing. When there's a bright, nearby light source, I get better results with a narrow field, through a telescope or with the naked eye, blocking the light with my hands, but if there is no distracting lights, I get better performance by going as wide as possible, or nearly so.

100 AFOV eyepieces are awesome! And very expensive...


Clear skies!
Thomas, Denmark


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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Astrojensen]
      #5538753 - 11/25/12 01:46 PM

The only possible benefits I've seen from wider AFOV eyepieces are that they allow for larger TFOVs and I don't have to nudge the Dob as often.

Narrower AFOVs will block glare from nearby brighter objects. Other than that, I see no benefit from a narrower AFOV.

IME, any other benefit of either wide or narrow AFOV is merely aesthetic or due to some personal eccentricity of the observer ... which pretty much amounts to the same thing.


Mike


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Dave MitskyModerator
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Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Sarkikos]
      #5538853 - 11/25/12 02:31 PM

Here's a quote from a report by a fellow CAS member regarding observing B33 through an 18" f/4.3 StarStructure Dob (equipped with a Paracorr) from the peak of Spruce Knob, West Viriginia, back in October:

A special treat was when I borrowed Bill Hs 2 H-Beta filter and sought out the Horsehead with my 17mm Ethos (133x, 3.4mm exit pupil). The image was surprisingly LARGE, taking up about 1/3 or more of the right side of the field of view. When I shared the view with Dave M, he said it was the highest magnification he had ever seen of the Horsehead and was surprised it held up so well. He suggested I use something with about a 5mm exit pupil, so out came my 24mm Panoptic (4.9mm exit pupil) and he was right. It popped much more easily, with the Horsehead now a clear stand-out against the brighter nebulosity. As I write this Im kicking myself for not thinking of trying my 31mm Nagler, too.

I can attest that the difference between the two views was striking.

http://www.chesmontastro.org/node/8967

Dave Mitsky


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Starman1
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Reged: 06/24/03

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Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Sarkikos]
      #5538883 - 11/25/12 02:52 PM

Quote:

The only possible benefits I've seen from wider AFOV eyepieces are that they allow for larger TFOVs and I don't have to nudge the Dob as often.

Narrower AFOVs will block glare from nearby brighter objects. Other than that, I see no benefit from a narrower AFOV.

IME, any other benefit of either wide or narrow AFOV is merely aesthetic or due to some personal eccentricity of the observer ... which pretty much amounts to the same thing.


Mike



And if your widefields are flat and sharp to the edge, simply put the offending star or stars outside the FOV and view the object off-center. I've been doing that for years with NGC2024 (Flame Nebula). No need for a narrow AFOV eyepiece.


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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Starman1]
      #5538998 - 11/25/12 03:49 PM

Don,

Quote:

And if your widefields are flat and sharp to the edge, simply put the offending star or stars outside the FOV and view the object off-center. I've been doing that for years with NGC2024 (Flame Nebula). No need for a narrow AFOV eyepiece.




You're right. I also do that with the Flame Nebula, as well as other nebulae, without really even thinking about it.

So then, it seems there is no need for a narrow-field eyepiece qua narrow-field.


Mike


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Tony Flanders
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Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Starman1]
      #5539110 - 11/25/12 04:55 PM

Quote:

If your widefields are flat and sharp to the edge, simply put the offending star or stars outside the FOV and view the object off-center.




For me, the problem isn't image quality so much as the physical discomfort of looking at the field stop, especially in eyepieces with AFOVs bigger than 70 degrees. This often requires either swiveling my eye or bending my neck at uncomfortable angles. Oddly, it seems to depend some on the eyepiece design; two different eyepieces with the same focal length, AFOV, and even nominal eye relief may be quite different in this regard.

When putting a bright star out of the FOV is an issue, I much prefer narrower fields of view.


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tcmzodiac
professor emeritus


Reged: 11/11/11

Re: Bound and determined : Horsehead thru a ten..BUT.. [Re: Tony Flanders]
      #5539228 - 11/25/12 06:42 PM

I'd like to see you folks discuss the merits of fewer EP elements as regards the view. This has been mentioned as being a "plus" in addition to the narrower FOV/excluding Alnitak from same......

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David Knisely
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: tcmzodiac]
      #5539720 - 11/26/12 01:33 AM

Quote:

I'd like to see you folks discuss the merits of fewer EP elements as regards the view. This has been mentioned as being a "plus" in addition to the narrower FOV/excluding Alnitak from same......




With the newer eyepiece coatings and designs, the number of elements isn't an overriding factor in eyepiece selection when going for something really faint. Heck, I often use an 8 element eyepiece with a 4-element Powermate to see faint detail in planetary nebulae, so while theoretically, it may be a factor, in practice, it is less than many people make it out to be. Clear skies to you.


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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: David Knisely]
      #5539864 - 11/26/12 06:57 AM

I only notice an edge to simple glass such as orthos when I'm trying to bag faint DSO toward the limiting magnitude of my telescope. XW's are supposed to have good transmission. I use my XW 3.5 for planetaries, but I favor my BGO's for faint galaxies and BN. I'll have to compare my BGO's to my XW's to see if there is still an advantage to simple glass.

If at all possible, though, I like to keep my Baader Zoom in the focuser so I can dial in the best image scale and perceived contrast for each object. IMO, that makes much more sense than switching out eyepieces all night. K.I.S.S.

Mike


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Starboat
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Reged: 03/14/12

Loc: Texas
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Sarkikos]
      #5548088 - 12/01/12 12:06 AM

I've seen the Horsehead many times now, but never through less than 18" or without an H-beta filter, or great darkness. For first timers, I would stress that you're really trying to pick up IC 434. When you manage that, B33 will appear as a thumb in the pudding of the nebula, the snout not at first apparent. Its not tiny, just faint. Averted vision certainly helps, along with patience. In Oz through a 30" with filter under great darkness, I could see it in all its glory with direct vision, snout and all. This was because IC 434 wasn't just visible, but almost sparkling.

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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Starboat]
      #5548511 - 12/01/12 10:03 AM

Quote:

I've seen the Horsehead many times now, but never through less than 18" or without an H-beta filter, or great darkness.




Yep.

Quote:

For first timers, I would stress that you're really trying to pick up IC 434.




Makes sense to me. And I don't think this is stressed enough. If you can't see IC 434, forgetaboutit. Find something else to do that night.

Quote:

When you manage that, B33 will appear as a thumb in the pudding of the nebula, the snout not at first apparent. Its not tiny, just faint.




Good to keep in mind.

Mike


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BillFerris
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Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Sarkikos]
      #5548552 - 12/01/12 10:36 AM

Quote:

Quote:

I've seen the Horsehead many times now, but never through less than 18" or without an H-beta filter, or great darkness.




Yep.




Just so folks don't become overly discouraged, under a truly pristine sky (excellent darkness and transparency), the B33/IC 434 complex is rather trivial in an unfiltered 18 inch, and is doable in a good quality, unfiltered 6 inch Newtonian or smaller refractor. It's the first observation that is most challenging. But, once you've seen the Horsehead and know what to look for, it is an object that is much more dependent on sky conditions than aperture when it comes to detectability.

Bill in Flag


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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: BillFerris]
      #5548668 - 12/01/12 12:03 PM

Dependent on sky conditions including level of light pollution as well as transparency.

Mike


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blb
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Reged: 11/25/05

Loc: Piedmont NC
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: Sarkikos]
      #5549155 - 12/01/12 05:50 PM

Quote:

...it is an object that is much more dependent on sky conditions than aperture when it comes to detectability.




How True! If you are not at a really dark sky site with good transparency, well you probably will not see IC 434 and if you can't see the nebula, well, you will not see the dark nebula silhouetted against the nebula. But if all goes well and you have the conditions (darkness and transparency) that you need to make this observation, then a good 4-inch refractor will do the job just fine.


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rannoch
member


Reged: 09/11/11

Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: blb]
      #5550261 - 12/02/12 12:30 PM

May I ask what the best eyepieces size is to have the best chance to see the HH? I have a 12" Meade F/10

I have a 2" H-Beta filter and soon to own a 1.25"

What 1.25" and 2" would be be best for my scope?


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David Knisely
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Loc: southeastern Nebraska
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: rannoch]
      #5550382 - 12/02/12 01:54 PM

Quote:

May I ask what the best eyepieces size is to have the best chance to see the HH? I have a 12" Meade F/10

I have a 2" H-Beta filter and soon to own a 1.25"

What 1.25" and 2" would be be best for my scope?




You will need a fairly long focal length eyepiece to get into the proper exit pupil range to detect the Horsehead. Probably something in the 35mm to 55mm focal length range for an eyepiece would get you there. A good 40mm Plossl or 55mm Plossl might be good places to start. Clear skies to you.


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rannoch
member


Reged: 09/11/11

Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: David Knisely]
      #5550451 - 12/02/12 02:27 PM

Hi David

Perhaps a Televue 40mm 1.25" Plossl and a 2" Televue 55" Plossl?

Or even a Meade 4000 Series 56mm Super Plossl Eyepiece 2"

A lot cheaper

Edited by rannoch (12/02/12 02:49 PM)


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ensign
professor emeritus


Reged: 12/16/08

Loc: Southwestern Ontario
Re: Bound and determined : Horsehead thru a ten..BUT.. new [Re: rannoch]
      #5550840 - 12/02/12 07:00 PM

Quote:

Hi David

Perhaps a Televue 40mm 1.25" Plossl and a 2" Televue 55" Plossl?

Or even a Meade 4000 Series 56mm Super Plossl Eyepiece 2"

A lot cheaper




I saw a Pentax 40 XL on A-mart recently. I have one and like the views through my 9.25 Edge.


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