After sitting on the optics for over 20 years, I'm finally about to start building my 17.5" f/4.5. I want to avoid collimation each time I set-up; due to the fast focal ratio it must be dead-on accurate. A laser collimator alone is insufficient and a star-test is mandatory for fine-tuning. The optical axis must coincide with the focuser axis to within a fraction of a milimeter and no commercial laser can accomplish this (that I'm aware of). I am a veteran of star-testing but have never done it with a Newtonian of this size- I've always been able to have my fingers on the collimation screws while looking through the focuser. Also the telescopes were driven, a big help at the high magnifications needed to see diffraction patterns big enough to be useful. I know many large scope owners only use the laser and call it "good enough". For deep-sky work at low and moderate magnifications, they are right, especially if the focal ratio is only moderately fast. But for maximum lunar & planetary detail, and splitting the closest double stars, "dead-on" collimation is mandatory on an f/4.5 scope. I've also thought about carrying an artificial star with the big scope, so a star-test could be performed before true darkness falls, and the scope need not be tracking- but this still means another chunk of time must be devoted to set-up each and every time. All this means I have all but made up my mind to make the scope with a standard tube, keeping the optics in-place at all times. It will still fit in my SUV (why I bought the thing in the first place, no kidding) and can be set-up quickly and easily by one person thanks to some design details- in less than five minutes (tops). I also like a "tubed" scope better for aesthetic reasons. I've never liked the look of trusses. I think I can get excellent contrast with a tubed design, as another bonus. If I ever build a larger scope, then certainly a truss-tube will be mandatory, but I can avoid it on this one. The scope will have a 3.5" ma secondary and a low-profile 2" r&p focuser. Active primary cooling, probably in the form of a blower across the face of the mirror. I already have all the hardware, optics, etc., and will be using composite materials for the tube and possibly the mount. A Dobsonian mount will be built initially but I'm designing a compact split-ring equatorial in Solidworks, for the future. The short f-ratio also means a tall ladder will not be needed. A step-stool is all that's needed for a person of average height. Observers over six feet may need nothing to stand on. So the reason for this post is one last chance for input from folks with different observing habits or ideas. I am pretty sure I've covered all the bases but it never hurts to step back and go over it all one more time before spending (more) money. Thanks! __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
Congrats on this ambitious project, Chuck. I know it'll be a great 'scope. Best wishes, Joe
Thanks, Joe. It should be big enough to christen with a bottle of champagne when it's done! --- Joe Bauman <bau@desnews.com> wrote:
Congrats on this ambitious project, Chuck. I know it'll be a great 'scope. Best wishes, Joe
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I have a bit of leeway with the overall length of the tube itself, but it will be somewhere close to 76". That's pretty short for a 17.5" aperture, thanks to the f/4.5 ratio. BTW, I have a Lumicon coma corrector that I purchased long ago, just for this scope. --- Joe Bauman <bau@desnews.com> wrote:
So how long will HMS Light Bucket be?
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Are you familiar with holographic laser collimation? http://web.telia.com/~u41105032/holographic/holographic.htm http://www.collimator.com/coltext.htm --- Chuck Hards <chuckhards@yahoo.com> wrote: <snip>
A laser collimator alone is insufficient . . . The optical axis must coincide with the focuser axis to within a fraction of a milimeter and no commercial laser can accomplish this (that I'm aware of). <snip> But for maximum lunar & planetary detail, and for splitting the closest double stars, "dead-on" collimation is mandatory on an f/4.5 scope. <snip> So the reason for this post is one last chance for input from folks with different observing habits or ideas. I am pretty sure I've covered all the bases but it never hurts to step back and go over it all one more time before spending (more) money.
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Yes, actually. The first time I used it on my f/5.6 Newtonian was with Rich Tenney at the Lakeside site some years ago. Even this method is not accurate enough for precision collimation with very fast optical systems. At f/4.5, collimation must be within a fraction of a milimeter. Even projecting a grid leaves too much room for subjective (or perceptive, really) interpretation. Repeating the procedure could probably average-out any residual errors. But even if it worked without a star-test tweak the first time, it still takes time that I don't want to spend at every set-up. It occured to me that one could possibly use a video feed at the eyepiece, and watch a screen while tweaking the collimation screws- if the camera were sensitive enough to detect the diffraction rings, which isn't likely. But here again, I don't want to HAVE to adjust collimation every time I set-up. I'll check it each time, but only want to adjust it if necessary. Assembling a telescope every time means at least a minor adjustment for precision collimation with a large reflector. At this point, there is probably no way to convince me of a necessity for a truss-tube design at this aperture. Thanks, Kurt. --- Canopus56 <canopus56@yahoo.com> wrote:
Are you familiar with holographic laser collimation?
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Hey Chuck, For whatever it's worth, my 10" F/4.5 sonotube dob needs collimation every time I go out (probably has something to do with gravel roads and long drives). I'm sure that your mechanical work on your new scope will be considerably better than my Frankenscope, but unless you've got something special up your sleeve I'll bet you've still got to turn those knobs. Wonder if you could do something with DC motors and worm gears. Then you could stay at the eyepiece. MC On Jul 24, 2006, at 10:49 AM, Chuck Hards wrote:
Yes, actually. The first time I used it on my f/5.6 Newtonian was with Rich Tenney at the Lakeside site some years ago.
Even this method is not accurate enough for precision collimation with very fast optical systems. At f/4.5, collimation must be within a fraction of a milimeter. Even projecting a grid leaves too much room for subjective (or perceptive, really) interpretation. Repeating the procedure could probably average-out any residual errors. But even if it worked without a star-test tweak the first time, it still takes time that I don't want to spend at every set-up.
It occured to me that one could possibly use a video feed at the eyepiece, and watch a screen while tweaking the collimation screws- if the camera were sensitive enough to detect the diffraction rings, which isn't likely.
But here again, I don't want to HAVE to adjust collimation every time I set-up. I'll check it each time, but only want to adjust it if necessary. Assembling a telescope every time means at least a minor adjustment for precision collimation with a large reflector. At this point, there is probably no way to convince me of a necessity for a truss-tube design at this aperture.
Thanks, Kurt.
--- Canopus56 <canopus56@yahoo.com> wrote:
Are you familiar with holographic laser collimation?
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Michael Carnes MichaelCarnes@earthlink.net home.earthlink.net/~michaelcarnes
Hey Michael: Do you have lock-knobs on the collimation bolts? Is the primary rattling around in it's cell? I know a "loose" fit is recommended, but there are ways to restrain a mirror without introducing mechanical stress, not in the literature. None of my solid-tube Newtonains need collimation every time they are used. Unless I disassemble them, only a tweak about twice a year is typically required- even after hauling them repeatedly over those darned Utah back roads. Of course, these tubes are either aluminum or fiberglass, not cardboard. My old 10" cardboard Dob with commercial cell did require frequent collimation. And I use a padded transportation cradle for the OTA now. "Something special up my sleeve" is my trademark... ;o) --- Michael Carnes <MichaelCarnes@earthlink.net> wrote:
Hey Chuck, For whatever it's worth, my 10" F/4.5 sonotube dob needs collimation every time I go out (probably has something to do with gravel roads and long drives). I'm sure that your mechanical work on your new scope will be considerably better than my Frankenscope, but unless you've got something special up your sleeve I'll bet you've still got to turn those knobs. Wonder if you could do something with DC motors and worm gears. Then you could stay at the eyepiece.
MC
On Jul 24, 2006, at 10:49 AM, Chuck Hards wrote:
Yes, actually. The first time I used it on my f/5.6 Newtonian was with Rich Tenney at the Lakeside site some years ago.
Even this method is not accurate enough for precision collimation with very fast optical systems. At f/4.5, collimation must be within a fraction of a milimeter. Even projecting a grid leaves too much room for subjective (or perceptive, really) interpretation. Repeating the procedure could probably average-out any residual errors. But even if it worked without a star-test tweak the first time, it still takes time that I don't want to spend at every set-up.
It occured to me that one could possibly use a video feed at the eyepiece, and watch a screen while tweaking the collimation screws- if the camera were sensitive enough to detect the diffraction rings, which isn't likely.
But here again, I don't want to HAVE to adjust collimation every time I set-up. I'll check it each time, but only want to adjust it if necessary. Assembling a telescope every time means at least a minor adjustment for precision collimation with a large reflector. At this point, there is probably no way to convince me of a necessity for a truss-tube design at this aperture.
Thanks, Kurt.
--- Canopus56 <canopus56@yahoo.com> wrote:
Are you familiar with holographic laser collimation?
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Michael, now you have me re-thinking some aspects of my design, due mostly to the scale of the project. Rich and I discussed this briefly a few weeks ago. A 17.5" mirror is considerably more massive than a 10" mirror! I think I'll re-examine some of the cell details with this in mind. Somewhere, years ago, I remember seeing photos of two approaches to remotely operating primary collimation screws, but both required a fairly loose setup, so large operating torques would not be required. Unfortunately this also meant that gross collimation was required almost every time. --- Michael Carnes <MichaelCarnes@earthlink.net> wrote:
Hey Chuck, For whatever it's worth, my 10" F/4.5 sonotube dob needs collimation every time I go out
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Chuck, my email server caused some problems this morning and I lost most of the earlier messages regarding your undertaking. I've given a lot of thought (but neither time nor $$$ yet) to upgrading my 18-year-old 10" alt-az, the design of which is based largely on Richard Berry's book, Build Your Own Telescope. I followed Berry's instructions for attaching the mirror to the plywood mirror cell, with silicone glue. I rarely need to re-collimate; usually I only have to tweak the collimation once or twice per year. Near-perfect out-of focus star images show that it seems to hold the collimation from observing trip to observing trip, and I have never noticed any mechanical stresses on the mirror. BTW, my mirror is a high-quality, full-thickness Parks mirror. Do you or does anyone else have experience using silicone glue on larger and/or thinner mirrors? What kind of mirror cell are you contemplating? Have you considered any alternatives to both solid-tube designs and truss-tube designs? If so, I'd be interested to know your thoughts if you're willing to share. Kim -----Original Message----- Michael, now you have me re-thinking some aspects of my design, due mostly to the scale of the project. Rich and I discussed this briefly a few weeks ago. A 17.5" mirror is considerably more massive than a 10" mirror! I think I'll re-examine some of the cell details with this in mind. Somewhere, years ago, I remember seeing photos of two approaches to remotely operating primary collimation screws, but both required a fairly loose setup, so large operating torques would not be required. Unfortunately this also meant that gross collimation was required almost every time.
Hi Kim: --- Kim <kimharch@cut.net> wrote:
Do you or does anyone else have experience using silicone glue on larger and/or thinner mirrors?
Not on anything larger than 6". It worked well mechanically for that size, but I had trouble getting it off when it came time to recoat the mirror, at the request of the person doing the aluminizing.
What kind of mirror cell are you contemplating?
9-point floatation, though an 18-point cell is also a possibility. Aluminum framwork, steel adjustment springs. This mirror has a 1:10 thickness-to-diameter ratio, not quite full thickness but not especially "thin", either. Pyrex, old Coulter manufacture. Ronchi test shows a good figure, slight hill in the center that will be in the secondary shadow.
Have you considered any alternatives to both solid-tube designs and truss-tube designs?
Yes. One possibility is a two-piece tube that has no possibility for slop or mis-alignment when assembled. I also have considered a "short-truss" design, with a tubular front and rear end, and very short truss tubes in-between, of larger diameter than usual. The truss section could even be built as a unit, that is, the tubes themselves permanently attached to front and rear rings and so not as subject to misalignment. In this case, it's really a 3-piece tube. It is much easier to design a multi-sectioned tube to assemble perfectly each time, than a conventional truss, IMO. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
Kim, I should emphasize that minimizing set-up time is a major requirement. Simplicity is preferred over engineering "wow" factor or compactness for transportation. Minimal knobs, tools, few parts, simplified procedure-even if it means lifting an extra 20 or 30 pounds- which it shouldn't. --- Chuck Hards <chuckhards@yahoo.com> wrote:
this case, it's really a 3-piece tube.
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Chuck: I've also considered options for using tubular sections that are collapsible or split along the axis of the tube to allow more room to carry other equipment in the car. Do you have the capability to form sheet metal? I've wondered about a large-diameter aluminum tube formed from two half-cylindrical pieces, joined with a simple flat joint at the seams. A couple of screws could hold the whole thing together. I've also considered beginning with cylindrical sections, then "carving" away as much as possible while keeping the strength of the cylindrical form intact. I've never seen such a tube, but I'd be surprised if it hasn't been done. Kim
I have a simple break and a shear, but not large enough for this size work. I'm sticking with composites since that's my field of expertise. A composite tube will allow high strength and rigidity without the weight of aluminum. I like your idea of a tube split longitudinally. You could hinge one side, and have a "pod" insert to carry stuff that is removed on-site. Maybe turns into a bench or table or some other dual purpose. --- Kim <kimharch@cut.net> wrote:
Chuck:
I've also considered options for using tubular sections that are collapsible or split along the axis of the tube to allow more room to carry other equipment in the car. Do you have the capability to form sheet metal? I've wondered about a large-diameter aluminum tube formed from two half-cylindrical pieces, joined with a simple flat joint at the seams. A couple of screws could hold the whole thing together. I've also considered beginning with cylindrical sections, then "carving" away as much as possible while keeping the strength of the cylindrical form intact. I've never seen such a tube, but I'd be surprised if it hasn't been done.
Kim
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Well, Chuck, have fun. I probably won't have time to work on my scope until this winter. Kim
I hear ya. I'm in the middle of our "busy season" at work myself- no time off at all this summer. The bulk of the work on my scope will be when the leaves start to fall, but I'm doing some preliminary work on my lunch breaks. --- Kim <kimharch@cut.net> wrote:
Well, Chuck, have fun. I probably won't have time to work on my scope until this winter.
Kim
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I have found the barlowed laser technique pioneered by Nils Olof Carlin (Sky and Telescope, January 2003), to be as good as the star test and better than a Cheshire. A laser collimator alone will only work if your telescope is perfectly squared off, which in practice rarely occurs. Jim Kendrick sells the barlowed laser but you can easily make one for yourself as Carlin describes in his article. I collimated several large fast Newtonians at the Bryce Canyon Astronomy Festival using my barlowed laser and the improvement was dramatic. I have seen examples of horribly collimated telescopes using the laser alone. Clear Skies Don Colton -----Original Message----- From: utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com [mailto:utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Sunday, July 23, 2006 6:48 PM To: Utah-Astro Subject: [Utah-astronomy] Design considerations After sitting on the optics for over 20 years, I'm finally about to start building my 17.5" f/4.5. I want to avoid collimation each time I set-up; due to the fast focal ratio it must be dead-on accurate. A laser collimator alone is insufficient and a star-test is mandatory for fine-tuning. The optical axis must coincide with the focuser axis to within a fraction of a milimeter and no commercial laser can accomplish this (that I'm aware of). I am a veteran of star-testing but have never done it with a Newtonian of this size- I've always been able to have my fingers on the collimation screws while looking through the focuser. Also the telescopes were driven, a big help at the high magnifications needed to see diffraction patterns big enough to be useful. I know many large scope owners only use the laser and call it "good enough". For deep-sky work at low and moderate magnifications, they are right, especially if the focal ratio is only moderately fast. But for maximum lunar & planetary detail, and splitting the closest double stars, "dead-on" collimation is mandatory on an f/4.5 scope. I've also thought about carrying an artificial star with the big scope, so a star-test could be performed before true darkness falls, and the scope need not be tracking- but this still means another chunk of time must be devoted to set-up each and every time. All this means I have all but made up my mind to make the scope with a standard tube, keeping the optics in-place at all times. It will still fit in my SUV (why I bought the thing in the first place, no kidding) and can be set-up quickly and easily by one person thanks to some design details- in less than five minutes (tops). I also like a "tubed" scope better for aesthetic reasons. I've never liked the look of trusses. I think I can get excellent contrast with a tubed design, as another bonus. If I ever build a larger scope, then certainly a truss-tube will be mandatory, but I can avoid it on this one. The scope will have a 3.5" ma secondary and a low-profile 2" r&p focuser. Active primary cooling, probably in the form of a blower across the face of the mirror. I already have all the hardware, optics, etc., and will be using composite materials for the tube and possibly the mount. A Dobsonian mount will be built initially but I'm designing a compact split-ring equatorial in Solidworks, for the future. The short f-ratio also means a tall ladder will not be needed. A step-stool is all that's needed for a person of average height. Observers over six feet may need nothing to stand on. So the reason for this post is one last chance for input from folks with different observing habits or ideas. I am pretty sure I've covered all the bases but it never hurts to step back and go over it all one more time before spending (more) money. Thanks! __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.utahastronomy.com
Don, I had completely forgotten about that article. Time to dig it out and re-read it, thanks. I corresponded with Nils when I was on the ATM listserve some years ago. The squareness requirement is extremely difficult to obtain with a very large telescope that must be assembled before every use. Have you tried it with an f/4.5 or faster scope? --- "Don J. Colton" <djcolton@piol.com> wrote:
I have found the barlowed laser technique pioneered by Nils Olof Carlin (Sky and Telescope, January 2003), to be as good as the star test and better than a Cheshire. A laser collimator alone will only work if your telescope is perfectly squared off, which in practice rarely occurs. Jim Kendrick sells the barlowed laser but you can easily make one for yourself as Carlin describes in his article. I collimated several large fast Newtonians at the Bryce Canyon Astronomy Festival using my barlowed laser and the improvement was dramatic. I have seen examples of horribly collimated telescopes using the laser alone.
Clear Skies Don Colton
-----Original Message----- From:
utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com
[mailto:utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com]
On Behalf Of Chuck Hards Sent: Sunday, July 23, 2006 6:48 PM To: Utah-Astro Subject: [Utah-astronomy] Design considerations
After sitting on the optics for over 20 years, I'm finally about to start building my 17.5" f/4.5.
I want to avoid collimation each time I set-up; due to the fast focal ratio it must be dead-on accurate. A laser collimator alone is insufficient and a star-test is mandatory for fine-tuning. The optical axis must coincide with the focuser axis to within a fraction of a milimeter and no commercial laser can accomplish this (that I'm aware of).
I am a veteran of star-testing but have never done it with a Newtonian of this size- I've always been able to have my fingers on the collimation screws while looking through the focuser. Also the telescopes were driven, a big help at the high magnifications needed to see diffraction patterns big enough to be useful.
I know many large scope owners only use the laser and call it "good enough". For deep-sky work at low and moderate magnifications, they are right, especially if the focal ratio is only moderately fast. But for maximum lunar & planetary detail, and splitting the closest double stars, "dead-on" collimation is mandatory on an f/4.5 scope.
I've also thought about carrying an artificial star with the big scope, so a star-test could be performed before true darkness falls, and the scope need not be tracking- but this still means another chunk of time must be devoted to set-up each and every time.
All this means I have all but made up my mind to make the scope with a standard tube, keeping the optics in-place at all times. It will still fit in my SUV (why I bought the thing in the first place, no kidding) and can be set-up quickly and easily by one person thanks to some design details- in less than five minutes (tops). I also like a "tubed" scope better for aesthetic reasons. I've never liked the look of trusses. I think I can get excellent contrast with a tubed design, as another bonus. If I ever build a larger scope, then certainly a truss-tube will be mandatory, but I can avoid it on this one.
The scope will have a 3.5" ma secondary and a low-profile 2" r&p focuser. Active primary cooling, probably in the form of a blower across the face of the mirror. I already have all the hardware, optics, etc., and will be using composite materials for the tube and possibly the mount. A Dobsonian mount will be built initially but I'm designing a compact split-ring equatorial in Solidworks, for the future.
The short f-ratio also means a tall ladder will not be needed. A step-stool is all that's needed for a person of average height. Observers over six feet may need nothing to stand on.
So the reason for this post is one last chance for input from folks with different observing habits or ideas. I am pretty sure I've covered all the bases but it never hurts to step back and go over it all one more time before spending (more) money.
Thanks!
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Chuck My scope is an 18" f/4.3 and after the barlowed laser method I get perfect star images at 400x. I have also tried it on my Coulter 10.1" f/4.5 and it works very well. The Coulter has a non-adjustable secondary and even though the regular laser does not hit the center spot, by using the barlowed method I got perfectly centered star images at Wolf Creek. The Coulter as you might surmise is very far from being squared off. I also used the same method on my 7" f/5.6 scope. For the method to work you need a reinforcement label placed in the exact center of your primary mirror. This is the most difficult part but I have been told that Steve Dodds has templates and can do it in about 5 minutes. The Cheshire method is also very good providing you follow all the steps in Nils article in the June 2002 issue of Sky and Telescope. It is most important to make sure your diagonal is properly centered for the Cheshire method to work. This is not a requirement with the lasered Barlow method if you have a large enough diagonal to allow some slop such as in the Coulter 10.1" Also see http://web.telia.com/~u41105032/kolli/kolli.html and http://web.telia.com/~u41105032/kolli/kolli2.htm#barlowlaser Clear Skies Don -----Original Message----- From: utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com [mailto:utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Tuesday, July 25, 2006 12:06 PM To: Utah Astronomy Subject: RE: [Utah-astronomy] Design considerations Don, I had completely forgotten about that article. Time to dig it out and re-read it, thanks. I corresponded with Nils when I was on the ATM listserve some years ago. The squareness requirement is extremely difficult to obtain with a very large telescope that must be assembled before every use. Have you tried it with an f/4.5 or faster scope? --- "Don J. Colton" <djcolton@piol.com> wrote:
I have found the barlowed laser technique pioneered by Nils Olof Carlin (Sky and Telescope, January 2003), to be as good as the star test and better than a Cheshire. A laser collimator alone will only work if your telescope is perfectly squared off, which in practice rarely occurs. Jim Kendrick sells the barlowed laser but you can easily make one for yourself as Carlin describes in his article. I collimated several large fast Newtonians at the Bryce Canyon Astronomy Festival using my barlowed laser and the improvement was dramatic. I have seen examples of horribly collimated telescopes using the laser alone.
Clear Skies Don Colton
-----Original Message----- From:
utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com
[mailto:utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com]
On Behalf Of Chuck Hards Sent: Sunday, July 23, 2006 6:48 PM To: Utah-Astro Subject: [Utah-astronomy] Design considerations
After sitting on the optics for over 20 years, I'm finally about to start building my 17.5" f/4.5.
I want to avoid collimation each time I set-up; due to the fast focal ratio it must be dead-on accurate. A laser collimator alone is insufficient and a star-test is mandatory for fine-tuning. The optical axis must coincide with the focuser axis to within a fraction of a milimeter and no commercial laser can accomplish this (that I'm aware of).
I am a veteran of star-testing but have never done it with a Newtonian of this size- I've always been able to have my fingers on the collimation screws while looking through the focuser. Also the telescopes were driven, a big help at the high magnifications needed to see diffraction patterns big enough to be useful.
I know many large scope owners only use the laser and call it "good enough". For deep-sky work at low and moderate magnifications, they are right, especially if the focal ratio is only moderately fast. But for maximum lunar & planetary detail, and splitting the closest double stars, "dead-on" collimation is mandatory on an f/4.5 scope.
I've also thought about carrying an artificial star with the big scope, so a star-test could be performed before true darkness falls, and the scope need not be tracking- but this still means another chunk of time must be devoted to set-up each and every time.
All this means I have all but made up my mind to make the scope with a standard tube, keeping the optics in-place at all times. It will still fit in my SUV (why I bought the thing in the first place, no kidding) and can be set-up quickly and easily by one person thanks to some design details- in less than five minutes (tops). I also like a "tubed" scope better for aesthetic reasons. I've never liked the look of trusses. I think I can get excellent contrast with a tubed design, as another bonus. If I ever build a larger scope, then certainly a truss-tube will be mandatory, but I can avoid it on this one.
The scope will have a 3.5" ma secondary and a low-profile 2" r&p focuser. Active primary cooling, probably in the form of a blower across the face of the mirror. I already have all the hardware, optics, etc., and will be using composite materials for the tube and possibly the mount. A Dobsonian mount will be built initially but I'm designing a compact split-ring equatorial in Solidworks, for the future.
The short f-ratio also means a tall ladder will not be needed. A step-stool is all that's needed for a person of average height. Observers over six feet may need nothing to stand on.
So the reason for this post is one last chance for input from folks with different observing habits or ideas. I am pretty sure I've covered all the bases but it never hurts to step back and go over it all one more time before spending (more) money.
Thanks!
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Hi friends, I wanted to let you know about a photo I just uploaded. I wanted put another on my gallery but now I can't log in again. But here's the first: http://www.utahastronomy.com/view_photo.php?set_albumName=Joeb&id=M27 It's a view of M27, the Dumbbell Nebula, that I took the early morning of July 28. I was near Vernon, Tooele County, it wasn't too cold, and the sky was clear until close to morning. What a wonderful way to spend a night. At dusk a large owl cruised past several times, usually with wings outspread, tilted, searching the ground for some of the abundant jackrabbits and voles in the area. A little after 1 a.m. the coyotes began their nightly yip-howl-barking. Later when one started again, I joined in, hoping to sing a duet, but it knew an imposter when it heard one, and shut up. -- Best wishes, Joe
--- Joe Bauman <bau@desnews.com> wrote: <snip>
http://www.utahastronomy.com/view_photo.php?set_albumName=Joeb&id=M27
It's a view of M27, the Dumbbell Nebula, <snip>
Filters used or just a color ccd? - Canopus56 __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
Hi Kurt, this is the first time I've made a photo with luminosity exposures as well as color filters. Because M27 is so bright, they were brief exposures, like 10 second each. I stacked I think eight B&W images (80 seconds) and the same number of images of red, blue and green. Thanks, Joe
Here's the central portion of M-33 in black and white only. I was going to take a series of photos, including color, but ran out time. The galaxy was disappearing in the morning light, possibly in a film of cloud cover too, and my telescope wasn't tracking as well. So I only got luminosity three images, which I combined into this view. Thanks, Joe http://www.utahastronomy.com/view_photo.php?set_albumName=Joeb&id=M_33
Lovely images Joe, keep 'em coming! --- Joe Bauman <bau@desnews.com> wrote:
Here's the central portion of M-33 in black and white only.
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Joe, this is terrific. Although it does look like a minor bit of tracking differential (elongation of some stars to my eye), could it be slightly out of focus or a collimation artifact? You are rapidly improving at this, my friend. Keep it up! --- Joe Bauman <bau@desnews.com> wrote:
...telescope wasn't tracking as well.
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It's the tracking problem -- a never-ending hassle for me. But practice makes, well, not perfect, but better. Thanks, Joe
--- Joe Bauman <bau@desnews.com> wrote:
Hi Kurt, this is the first time I've made a photo with luminosity exposures as well as color filters. . . . the same number of images of red, blue and green. Thanks, Joe
Joe, the LRGB came out great. Lots a detail. I assume we are talking the color filters that render "true" visual color images with Astrodon - Kurt http://www.astrodon.com/ __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
I hope everyone has seen Kurt's lovely aurora picture by now. Wow! -- Joe
Great shot! Looks like a Christmas ornament. ----- Original Message ----- From: "Joe Bauman" <bau@desnews.com> To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Sent: Sunday, July 30, 2006 3:54 PM Subject: [Utah-astronomy] New pic
Hi friends, I wanted to let you know about a photo I just uploaded. I wanted put another on my gallery but now I can't log in again. But here's the first:
http://www.utahastronomy.com/view_photo.php?set_albumName=Joeb&id=M27
It's a view of M27, the Dumbbell Nebula, that I took the early morning of July 28. I was near Vernon, Tooele County, it wasn't too cold, and the sky was clear until close to morning.
What a wonderful way to spend a night. At dusk a large owl cruised past several times, usually with wings outspread, tilted, searching the ground for some of the abundant jackrabbits and voles in the area. A little after 1 a.m. the coyotes began their nightly yip-howl-barking. Later when one started again, I joined in, hoping to sing a duet, but it knew an imposter when it heard one, and shut up.
-- Best wishes, Joe
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Thanks, It's really a treat to see M27. Apparentely that's what will happen to our sun someday. Best wishes, Joe
Great shot! Looks like a Christmas ornament.
----- Original Message ----- From: "Joe Bauman" <bau@desnews.com> To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Sent: Sunday, July 30, 2006 3:54 PM Subject: [Utah-astronomy] New pic
Hi friends, I wanted to let you know about a photo I just uploaded. I wanted put another on my gallery but now I can't log in again. But here's the first:
http://www.utahastronomy.com/view_photo.php?set_albumName=Joeb&id=M27
It's a view of M27, the Dumbbell Nebula, that I took the early morning of July 28. I was near Vernon, Tooele County, it wasn't too cold, and the sky was clear until close to morning.
What a wonderful way to spend a night. At dusk a large owl cruised past several times, usually with wings outspread, tilted, searching the ground for some of the abundant jackrabbits and voles in the area. A little after 1 a.m. the coyotes began their nightly yip-howl-barking. Later when one started again, I joined in, hoping to sing a duet, but it knew an imposter when it heard one, and shut up.
-- Best wishes, Joe
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.utahastronomy.com
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participants (8)
-
Canopus56 -
Chuck Hards -
Don J. Colton -
Gary Thompson -
Joe Bauman -
Kim -
Michael Carnes -
Richard Tenney