Use newtonian for astrophotography
Use newtonian for astrophotography
Hi guys. i'm Jingguo. 1) I would like to know if anyone has try astrophotography using a 'fast' newtonian. 2) What is its pro and cons of using a 'fast' newtonian? 3) i heard that stars might end up with spiky edges due to d spider of the newtonian. 4) How to correct that error? thanks alot.
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carlogambino
- Posts: 222
- Joined: Fri Jul 09, 2004 9:10 pm
- Location: The Void
Yeah thats the diffraction spikes from the newtonian. For my personal preference, I like them. Spikes are caused when light is diffracted as it grazes past a spider vane. These spikes are oriented perpendicular to the edge of the vane and each vane will produce an opposing pair of spikes. For example, a single vane will produce two spikes, each extending in opposite directions from the object. A three-vane spider produces six spikes, spaced 60 degrees apart. A four-vane spider produces eight spikes, but they are stacked in pairs and visibly appear as four brighter spikes spaced 90 degrees apart. A curved-vane spider does not produce diffraction spikes but instead smears the diffracted light across the image. Perhaps you could use a curved-vane spider
as far as i know, 'fast' newtonians are damn good for astrophotography.
for qns 1: contact remus =p
for qns 2 : they can drastically cut down the exposure time, but still yield very impressive amount of details.(u have the tak 160 astrograph at f/3.3
)
for qns 3: each vane causes a two pointed spike. . Overlapping spikes will reinforce one another.Three vanes will cause six spikes.
for qns 4: curved vanes may be used to eliminate spikes, but at the cost of a (slight) increase in background illumination. (Since the diffraction effect is smeared over the whole image). Also, the curved vanes will block a larger area of the incoming light.
cheers,
wenyi
for qns 1: contact remus =p
for qns 2 : they can drastically cut down the exposure time, but still yield very impressive amount of details.(u have the tak 160 astrograph at f/3.3
)for qns 3: each vane causes a two pointed spike. . Overlapping spikes will reinforce one another.Three vanes will cause six spikes.
for qns 4: curved vanes may be used to eliminate spikes, but at the cost of a (slight) increase in background illumination. (Since the diffraction effect is smeared over the whole image). Also, the curved vanes will block a larger area of the incoming light.
cheers,
wenyi
Last edited by gwenyi on Sun Sep 12, 2004 4:12 pm, edited 1 time in total.
