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#1
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A question of viewing
So I was looking through my new (used) 10 inch dobs last night.
Saturn looked great I could even see a band. (or maybe it was the Cassini space craft--- Grin) I also look at Sirius and it looked -- well --umm--- grainy. Was this the viewing last night in Long Beach, Ca. Or do I have work to do on the scope? Thanks Mark -- Fly Lexx! |
#2
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A question of viewing
On Wed, 23 Apr 2008 23:51:37 GMT, "Mark F." wrote:
So I was looking through my new (used) 10 inch dobs last night. Saturn looked great I could even see a band. (or maybe it was the Cassini space craft--- Grin) I also look at Sirius and it looked -- well --umm--- grainy. Was this the viewing last night in Long Beach, Ca. Or do I have work to do on the scope? It will be rare for Sirius to look like a steady point. First of all, being a point source, its light reaches you through an extremely narrow column of air, so all sorts of seeing effects cause disruptions. This is different from planets, which subtend a finite angle. The effect is moderated somewhat by the large aperture of the telescope (which is why you don't usually see stars twinkle telescopically), but it's still there. Second, a bright point source highlights every optical aberration in your system. Are you saying Sirius looked different last night than it usually does? _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
#3
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A question of viewing
Mark F. wrote:
I also look at Sirius and it looked -- well --umm--- grainy. Was this the viewing last night in Long Beach, Ca. Or do I have work to do on the scope? Sounds like an effect of air turbulence: see for example Texereau, "How to Make a Telescope" (Willmann-Bell 1984) Fig. 15.2 (p. 292) for a drawing showing the effect of various degrees of turbulence on a point source image: if it is sufficiently severe, the central "disk" of the diffraction pattern looks more like a speckled, granular blob... -dave w |
#4
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A question of viewing
On Wed, 23 Apr 2008 23:51:37 GMT, Mark F. wrote:
So I was looking through my new (used) 10 inch dobs last night. Saturn looked great I could even see a band. (or maybe it was the Cassini space craft--- Grin) I also look at Sirius and it looked -- well --umm--- grainy. Was this the viewing last night in Long Beach, Ca. Or do I have work to do on the scope? Thanks Mark It could be that your bigger scope has introduced you to tube currents and a larger mirror's inability to reach thermal equilibrium in a timely fashion than you were used to with your smaller scope. The infinitely larger image of Saturn through the scope could seem less corrupted to your eyes than the point of light to which Sirius translates. -- Martin R. Howell Moderated sci.astro.amateur www.moderatedsciastroamateur.org ** Posted from http://www.teranews.com ** |
#5
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A question of viewing
Different in that I am using a 10 inch dobs for the first time, I was using
a 4.5 dobs. So I was looking through both scopes last night and trying to compare what I see. And then ask the good people here for a little of there knowledge. I am abput to try it again tonight and see what I come up with. Thanks Mark "Chris L Peterson" wrote in message ... On Wed, 23 Apr 2008 23:51:37 GMT, "Mark F." wrote: So I was looking through my new (used) 10 inch dobs last night. Saturn looked great I could even see a band. (or maybe it was the Cassini space craft--- Grin) I also look at Sirius and it looked -- well --umm--- grainy. Was this the viewing last night in Long Beach, Ca. Or do I have work to do on the scope? It will be rare for Sirius to look like a steady point. First of all, being a point source, its light reaches you through an extremely narrow column of air, so all sorts of seeing effects cause disruptions. This is different from planets, which subtend a finite angle. The effect is moderated somewhat by the large aperture of the telescope (which is why you don't usually see stars twinkle telescopically), but it's still there. Second, a bright point source highlights every optical aberration in your system. Are you saying Sirius looked different last night than it usually does? _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
#6
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A question of viewing
47 year old eyes.
I do have floater though. Mark "Sam Wormley" wrote in message news:s9SPj.79868$TT4.44664@attbi_s22... Mark F. wrote: So I was looking through my new (used) 10 inch dobs last night. Saturn looked great I could even see a band. (or maybe it was the Cassini space craft--- Grin) I also look at Sirius and it looked -- well --umm--- grainy. Was this the viewing last night in Long Beach, Ca. Or do I have work to do on the scope? Thanks Mark How old are your eyes? High magnification on bright sources can show you defects in your own eyes. |
#7
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A question of viewing
How old are your eyes? LOL..what an idiotic question. Probably the same age as the poster??? Duh? Unless they are a cyborg that got refitted... |
#8
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A question of viewing
MTA wrote:
How old are your eyes? LOL..what an idiotic question. Probably the same age as the poster??? Duh? Unless they are a cyborg that got refitted... Of course it is a perfectly valid question as it is well known that eye problems are more likely as age increases and many eye problems only present themselves under observing conditions. How old is your brain? (I'll add a :-) for the over sensitive or humor impaired) -- Greg Crinklaw Astronomical Software Developer Cloudcroft, New Mexico, USA (33N, 106W, 2700m) SkyTools: http://www.skyhound.com/cs.html Observing: http://www.skyhound.com/sh/skyhound.html Comets: http://comets.skyhound.com To reply take out your eye |
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