Archive for November, 2010
How long does it usually take to build a telescope?
Question by Skive: How long does it usually take to build a telescope?
Preferably not a telescope with the dinky cardboard tubes overlapping each other (although I should probably build that first for experience..). I’m in a class that is enabling us to have an independent study, and I was wondering if an amateur like me could build a telescope (not from a kit) if I had the right mentor, instructions and materials. The project of the independent study is due in 3 months. Is this possible, and if so, what kind of telescope would it be?
Any tips/advice/helpful hints would be greatly appreciated!
Best answer:
Answer by eri
Sure. Look into a Dobsonian, that’s probably the easiest one (you don’t have to worry much about the mount). I remember some guys in our local astronomy club even ground their own mirrors (they had to send out for them to be coated) to make their own telescopes.
What do you think? Answer below!
6 CommentsComet Lulin
Check out these Astronomy image processing images:
Comet Lulin
Image by zAmb0ni
Photo of Comet Lulin taken on Feb 23, 2009. That is Saturn in the bottom right.
Details:
Canon 300D – 75-300mm USM III lens @ 200mm.
39x 180s sub-frames taken @ ISO 800
Images stacked in Deep Sky Stacker aligning on the comet and letting the stars streak. Overlayed an image of the stars to give things a different look. Post processing in PS CS3.
NGC7000, the North America Nebula
Image by write_adam
NGC7000, the North America Nebula, is located in the constellation of Cygnus. It is a very large area of emission nebula — a cloud of superheated gas and dust — extending some 2.5 degrees to the east of Deneb. It was discovered in the early 1890s during experiments in wide field astrophotography.
This image was taken through a narrowband (13nm) hydrogen-alpha filter. Details for the astro-geeks:
NGC7000 North American Nebula
Capture date: May 28, 2008
Scope: WO FLT 110 (TMB) @ f/7
Mount: HEQ5 Pro, autoguided through a ZS66 and DSI-C using PHD
Camera: modified Canon 350, ISO800, Astronomik 13nm 2" h-alpha filter
Exposure: 88 minutes, 11x480sec lights, 3 darks, no flats
Conditions: poor seeing (it was very windy), good transparency
Processing: stacked in DeepSkyStacker, processed in PS CS2
M33
Image by madmiked
Image of galaxy M33
Telescope: 70mm Stellarvue.
Camera: Hutech modified Canon Rebel XT
ISO: 800
Exposure: 61×90 seconds, 25 dark frames
Processed with MaxDSLR, Photoshop with Astronomy Tools plugin
I really need to start doing flat frames. There was some vignetting in the original uncropped image and dust shadows, which can be seen near the HII region above.
No CommentsMost popular Planet Neptune auctions
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telescope eyepiece size help ?
Question by astro writer: telescope eyepiece size help ?
Ok, so i’ve had my Orion xt10i telescope for 2 years. I’m looking to get a wide field eyepiece. The xt10i accepts 1.25″ or 2″ eyepieces, and it makes sense that the really wide fields would come in 2″ varieties. There are two effects that contribute to wide field. One is magnification, and the other is apparent field of view. There are calculators that can give you numbers for a scope/eyepiece combination.
There’s sort of a lower limit on magnification. If the exit pupil turns out to be bigger than your eye, then any extra is wasted light – so images stop getting brighter. The exit pupil for a scope/eyepiece is the aperture divided by the magnification. So if my eye’s pupil can dilate to 7 mm, and my scope is 254 mm in diameter, then the minimum magnification is 36x, which corresponds to a 33 mm eyepiece (for a 1200 mm scope).
But i might want a big field of view without regard to exit pupil. How much focal length for an eyepiece can i use before i start seeing the central obstruction or the inside of my scope? I’ve not been able to find this anywhere. There should be some simple math to check this. The approach i’ve been using so far is to try various eyepieces in my scope. It’s an approach i trust more than math anyway.
And i discovered another issue. Coma. The 2″ 28 to 36 mm eyepieces i’ve tried so far all are unable to focus both at the center and the edges of the field without a Paracorr coma
corrector. At least i got to see how it works in my scope.
Best answer:
Answer by Charles
Time to do a little reading! This is one of the best resources I have found in selecting a good eye piece set. As my eyes have aged my needs have changed. Selecting wide field without coma is a challenged especially if you have a fast scope.
http://tinyurl.com/5ms6py
I hope this helps. It did help me.
HTH
Charles
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Cool Astronomy Image Processing images
A few nice Astronomy image processing images I found:
M31 1920×1200 crop
Image by vetenskapsman
ciliceastro.blogspot.com/2010/09/m31-redux.html
M31 center crop
Taken at Ghost Ranch near Abiquiu, New Mexico August 4th and 5th, 2010
Canon T2i (stock), 200mm EF-L @ f2.8
Astrotrac Travel System mount
Imaging temperature range: 52-58F
87 60sec exposures @ ISO3200 (taken over two evenings)
64 darks, 21 flats (1/5" ISO 100) 21 flatdarks
pre-processed in Nebulosity
post-processed in CS4
Black Holes May Ripple Fabric of Space (NASA, Chandra, 04/06/06)
Image by NASA’s Marshall Space Flight Center
Editor’s Note: Ten beautiful years of Chandra! This image from 2006 shows black holes getting closer and closer to each other.
This composite X-ray (blue)/radio (pink) image of the galaxy cluster Abell 400 shows radio jets immersed in a vast cloud of multimillion degree X-ray emitting gas that pervades the cluster. The jets emanate from the vicinity of two supermassive black holes (bright spots in the image). These black holes are in the dumbbell galaxy NGC 1128 (see optical image), which has produced the giant radio source, 3C 75.
The peculiar dumbbell structure of this galaxy is thought to be due to two large galaxies that are in the process of merging. Such mergers are common in the relatively congested environment of galaxy clusters. An alternative hypothesis is that the apparent structure is the result of a coincidence in time when the two galaxies are passing one another, like ships in the cosmic sea.
Careful analysis of the recent Chandra and radio data on 3C 75 indicates that the galaxies and their supermassive black holes are indeed bound together by their mutual gravity. By using the shape and direction of the radio jets, astronomers were able to determine the direction of the motion of the black holes. The swept-back appearance of the radio jets is produced by the rapid motion of the galaxy through the hot gas of the cluster, in much the same way that a motorcyclist’s scarf is swept back while speeding down the road.
The binary black holes in 3C 75 are about 25,000 light years apart. They are likely at an earlier stage in their evolution than the pair found in NGC 6240, which are about 3,000 light years apart. Computer simulations indicate that binary supermassive black holes gradually spiral toward each other until they coalesce to form a single, more massive black hole, accompanied by an enormous burst of gravitational waves.
These gravitational waves would spread through the Universe and produce ripples in the fabric of space, which would appear as minute changes in the distance between any two points. Sensitive gravitational wave detectors scheduled to be operational in the next decade could detect one of these events, which are estimated to occur several times each year in the observable Universe.
Image credit: X-ray: NASA/CXC/AIfA/D.Hudson & T.Reiprich et al.; Radio: NRAO/VLA/NRL
Read more about this image: www.chandra.harvard.edu/photo/2006/a400/
Read more about Chandra:
www.nasa.gov/chandra
p.s. You can see all of our Chandra photos in the Chandra Group in Flickr at: www.flickr.com/groups/chandranasa/ We’d love to have you as a member!
The moon, second take
Image by MedO42
The moon. Again. I didn’t even take any new pictures, so why on earth upload the same stuff again? 
Well, this time, the mapping is far more accurate, I color-corrected the images somewhat and did some post-processing for enhanced contrast. Also, I filled up the nasty empty areas from a different picture I shot that night. Those spots are still ugly, but I think overall the picture is a lot better than the last one, so here you go.
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