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David Knisely
Postmaster
Reged: 04/19/04
Posts: 6784
Loc: Beatrice, Nebraska
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Quote:
I can see the Crab Neb. from my deck when the seeing is good. I've seen it in my 8 inch dob and my 12.
I have to agree filters seem to be of little use on this one, at least in my backyard. 
Well, since the Crab Nebula has a lot of broadband synchrotron radiation emission, it may not be helped as much by filters as a pure line emitter, but I can't really agree that filters are not of much use on it. With my NPB filter (a narrowband unit similar to the Lumicon UHC or Orion Ultrablock), the Crab went from invisible to visible under magnitude 5 skies, although the object is still fairly faint. Clear skies to you.
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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
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StargazerJMK
professor emeritus
Reged: 04/12/05
Posts: 690
Loc: Out in the Dark Looking Up
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David, must be using the wrong filter. I'll double check my equipment and see what I have (been a while since I've been able to observe due to an accident). Maybe that I need to get an NPB filter.
Thanks for that info.
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Joan
StargazerJMK
Location:
47° 15' N/122° 30' W (Tacoma, WA)
Out in the Dark Looking UP!
Orion XT12 Classic/F4.9 w/a Wyorock Focuser
EZ CBP tracking platform
Coronado PST H-alpha
Home-made 8 in./F6 Dob
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apartment42
member
Reged: 03/15/08
Posts: 69
Loc: 43º39'N 79º32'W -ish
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I've personally found the Thousand Oaks narrowband filter the best on M1. I've also used the Orion Ultrablock and Meade narrowband, and found them slightly less effective.
It may just be my eyes, though.
A friend of mine with a 14" Dob says he sees the best detail with an OIII filter, but that its half as bright. I've never personally observed M1 through an OIII, though ... just passin it down the pipeline.
-Alex
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Facebook (I hate facebook)
Blog (Being retooled)
"Mind opening leads to compassion..."
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 6784
Loc: Beatrice, Nebraska
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Quote:
I've personally found the Thousand Oaks narrowband filter the best on M1. I've also used the Orion Ultrablock and Meade narrowband, and found them slightly less effective.
It may just be my eyes, though.
A friend of mine with a 14" Dob says he sees the best detail with an OIII filter, but that its half as bright. I've never personally observed M1 through an OIII, though ... just passin it down the pipeline.
-Alex
Some OIII filters do show the filaments a little more distinctly in large apertures, but the overall size of the object decreases a bit when the OIII is used (seems to become a little more round with the OIII). For best results, I generally use either a narrowband filter (DGM Optics NPB, Lumicon UHC, Orion Ultrablock, etc.) or a broadband filter like the Lumicon Deep-sky. Clear skies to you.
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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
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John Lacey
member
Reged: 03/12/08
Posts: 54
Loc: Central Coast, CA
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Quote:
Every time look at M1, I wonder how it must have looked to Charles Messier. It is so dim and faint without filters and I doubt he had equipment as good as we have today and certainly did not have an NPB or UHC filter. He had to be quite an observer - Bruce
Well, the nebula is less than a thousand years old, and it's growing dimmer as the gas expands. Turn Left at Orion suggests that it was probably about twice as bright when Messier was looking at it.
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John L
Orion XT8i "Jetson", Q70 32mm, Hyperion 17mm, 8mm
Orion 10x50 UltraView
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akemag
sage
Reged: 10/26/07
Posts: 442
Loc: Sweden
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I begin to wonder if it really was M1 i saw, as described in my earlier post here. You guys have 10" light buckets and still have problems seeing it sometimes. It sure was the faintest thing i´ve seen yet. But can it be spotted with a 4.7", or was it something else i saw?
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Celestron Omni XLT 120
10" GSO DOB
Bresser Skylux 70mm
5mm Ortho
6.5mm, 25mm, 32mm Plossl
3.6mm, 10mm, 25mm MA
20mm Erfle
4mm, 10mm, 12mm, 18mm RK20mm Kellner
8mm, 20mm Huygens
1.5-2x Barlow
Orange, Green, Variable Polarizing Moon filter
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 6784
Loc: Beatrice, Nebraska
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Quote:
I begin to wonder if it really was M1 i saw, as described in my earlier post here. You guys have 10" light buckets and still have problems seeing it sometimes. It sure was the faintest thing i´ve seen yet. But can it be spotted with a 4.7", or was it something else i saw?
I have seen M1 in a 60mm refractor at around 26x from a fairly dark-sky site (ZLM 5.8), so it is possible to see it in some fairly small scopes if the power is kept fairly low and you use averted vision. You won't see much detail, but you should still see the object. Clear skies to you.
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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
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