I think that next year I will try making a 20" f/10. I plan to fold the optics and view from the ground. I am researching this year to see how I can correct for Astigmatism and Coma because I would like to put the secondary off axis. So far I think I will have the 20" ground to f/10. I will use a 10" secondary and f/8 and bring the light back down to a diagonal to put the light in my eyepiece. Dave -----Original Message----- From: Brent Watson [mailto:brentjwatson@yahoo.com] Sent: Friday, February 21, 2003 11:06 AM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Mirrors My 22 inch is f6.3. Only a couple of folks have required oxygen. Brent --- Greg Taylor <astronomus_maximus@yahoo.com> wrote:
Imagine a 30" f/7...
"Pass me that pressure suit willya?"
"Sure thing; oh, and watch out for those satellites, they come a little close. By the way, did you remember your parachute?"
"Naw, I'd just burn up if I fell anyhow..."
Cave made some sweet mirrors, so I've been told. You can probably get some nice high power views with it too.
Agreeing with what Chuck said, my 10 f/5.6 does a better job than it would if it were f/4.5, being mass produced and all. On a rare night of perfect seeing last summer (very far from here), I was able to push it to 580x without image degradation. I saw detail on Uranus! (Boy that dob driver comes in handy at those high magnifications)
--- David L Bennett <dlbennett@mac.com> wrote:
Don't forget considerations of field of view! My 10" f/5 Cave with a 40mm Tele Vue Wide Field gives some very impressive Milky Way shots ;)
On Friday, February 21, 2003, at 09:58 AM, Chuck Hards wrote:
Everyone should, unless there is a specific reason for going "short". Of course, legitimate reasons include transportation and ergonomics.
Brent's always been right-on in that department! :)
C.
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Hey, my 16-inch f/6.25 only requires an 8-foot ladder. :-) -Rich --- David Dunn <david.dunn@albertsons.com> wrote:
I think that next year I will try making a 20" f/10. I plan to fold the optics and view from the ground. I am researching this year to see how I can correct for Astigmatism and Coma because I would like to put the secondary off axis. So far I think I will have the 20" ground to f/10. I will use a 10" secondary and f/8 and bring the light back down to a diagonal to put the light in my eyepiece.
Dave
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Dave Dunn wrote: I think that next year I will try making a 20" f/10. I plan to fold the optics and view from the ground. I am researching this year to see how I can correct for Astigmatism and Coma because I would like to put the secondary off axis. Dave I would be very interested in what you come up with. Please let us know, I would love to do the same type of thing if I know what I was doing. Jim David Dunn <david.dunn@albertsons.com> wrote:I think that next year I will try making a 20" f/10. I plan to fold the optics and view from the ground. I am researching this year to see how I can correct for Astigmatism and Coma because I would like to put the secondary off axis. So far I think I will have the 20" ground to f/10. I will use a 10" secondary and f/8 and bring the light back down to a diagonal to put the light in my eyepiece. Dave -----Original Message----- From: Brent Watson [mailto:brentjwatson@yahoo.com] Sent: Friday, February 21, 2003 11:06 AM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Mirrors My 22 inch is f6.3. Only a couple of folks have required oxygen. Brent --- Greg Taylor wrote:
Imagine a 30" f/7...
"Pass me that pressure suit willya?"
"Sure thing; oh, and watch out for those satellites, they come a little close. By the way, did you remember your parachute?"
"Naw, I'd just burn up if I fell anyhow..."
Cave made some sweet mirrors, so I've been told. You can probably get some nice high power views with it too.
Agreeing with what Chuck said, my 10 f/5.6 does a better job than it would if it were f/4.5, being mass produced and all. On a rare night of perfect seeing last summer (very far from here), I was able to push it to 580x without image degradation. I saw detail on Uranus! (Boy that dob driver comes in handy at those high magnifications)
--- David L Bennett wrote:
Don't forget considerations of field of view! My 10" f/5 Cave with a 40mm Tele Vue Wide Field gives some very impressive Milky Way shots ;)
On Friday, February 21, 2003, at 09:58 AM, Chuck Hards wrote:
Everyone should, unless there is a specific reason for going "short". Of course, legitimate reasons include transportation and ergonomics.
Brent's always been right-on in that department! :)
C.
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Dave, That's a VERY ambitous project. The off axis correction will be a fun project, and you will have a very interesting scope. I'm anxious to see it. Brent --- David Dunn <david.dunn@albertsons.com> wrote:
I think that next year I will try making a 20" f/10. I plan to fold the optics and view from the ground. I am researching this year to see how I can correct for Astigmatism and Coma because I would like to put the secondary off axis. So far I think I will have the 20" ground to f/10. I will use a 10" secondary and f/8 and bring the light back down to a diagonal to put the light in my eyepiece.
Dave
-----Original Message----- From: Brent Watson [mailto:brentjwatson@yahoo.com] Sent: Friday, February 21, 2003 11:06 AM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Mirrors
My 22 inch is f6.3. Only a couple of folks have required oxygen.
Brent
--- Greg Taylor <astronomus_maximus@yahoo.com> wrote:
Imagine a 30" f/7...
"Pass me that pressure suit willya?"
"Sure thing; oh, and watch out for those satellites, they come a little close. By the way, did you remember your parachute?"
"Naw, I'd just burn up if I fell anyhow..."
Cave made some sweet mirrors, so I've been told. You can probably get some nice high power views with it too.
Agreeing with what Chuck said, my 10 f/5.6 does a better job than it would if it were f/4.5, being mass produced and all. On a rare night of perfect seeing last summer (very far from here), I was able to push it to 580x without image degradation. I saw detail on Uranus! (Boy that dob driver comes in handy at those high magnifications)
--- David L Bennett <dlbennett@mac.com> wrote:
Don't forget considerations of field of view! My 10" f/5 Cave with a 40mm Tele Vue Wide Field gives some very impressive Milky Way shots ;)
On Friday, February 21, 2003, at 09:58 AM, Chuck Hards wrote:
Everyone should, unless there is a specific reason for going "short". Of course, legitimate reasons include transportation and ergonomics.
Brent's always been right-on in that department! :)
C.
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Dave, consider a modified Newtonian approach, where the diagonal is set at a much lower angle than 45-degrees. The light beam is shot back down the tube and exits at a grazing angle, basically as low on the tube as you want. A third mirror can then turn beam back out at a right angle to the tube. Once you get above 16" inches or so, the light loss of a secondary mirror becomes minimal in proportion to total area. The major advantage of an unobstructed system is a lack of diffraction artifacts, but unless you get the correction JUST RIGHT, the lack of diffraction spikes & better energy distribution in the diffraction rings won't offset the astigmatic images. And even the best unobstructed systems I've seen don't produce textbook-perfect spot diagrams. Also, typically the larger the unobstructed system, the more difficult the optical work, -AND- an absoulutely rigid tube assembly is mandatory. My 6 cents. C. --- David Dunn <david.dunn@albertsons.com> wrote:
I think that next year I will try making a 20" f/10. I plan to fold the optics and view from the ground. I am researching this year to see how I can correct for Astigmatism and Coma because I would like to put the secondary off axis. So far I think I will have the 20" ground to f/10. I will use a 10" secondary and f/8 and bring the light back down to a diagonal to put the light in my eyepiece.
Dave
-----Original Message----- From: Brent Watson [mailto:brentjwatson@yahoo.com] Sent: Friday, February 21, 2003 11:06 AM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Mirrors
My 22 inch is f6.3. Only a couple of folks have required oxygen.
Brent
--- Greg Taylor <astronomus_maximus@yahoo.com> wrote:
Imagine a 30" f/7...
"Pass me that pressure suit willya?"
"Sure thing; oh, and watch out for those satellites, they come a little close. By the way, did you remember your parachute?"
"Naw, I'd just burn up if I fell anyhow..."
Cave made some sweet mirrors, so I've been told. You can probably get some nice high power views with it too.
Agreeing with what Chuck said, my 10 f/5.6 does a better job than it would if it were f/4.5, being mass produced and all. On a rare night of perfect seeing last summer (very far from here), I was able to push it to 580x without image degradation. I saw detail on Uranus! (Boy that dob driver comes in handy at those high magnifications)
--- David L Bennett <dlbennett@mac.com> wrote:
Don't forget considerations of field of view! My 10" f/5 Cave with a 40mm Tele Vue Wide Field gives some very impressive Milky Way shots ;)
On Friday, February 21, 2003, at 09:58 AM, Chuck Hards wrote:
Everyone should, unless there is a specific reason for going "short". Of course, legitimate reasons include transportation and ergonomics.
Brent's always been right-on in that department! :)
C.
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Go for it! Folded designs are the wave of the future. Greg --- David Dunn <david.dunn@albertsons.com> wrote:
I think that next year I will try making a 20" f/10. I plan to fold the optics and view from the ground. I am researching this year to see how I can correct for Astigmatism and Coma because I would like to put the secondary off axis. So far I think I will have the 20" ground to f/10. I will use a 10" secondary and f/8 and bring the light back down to a diagonal to put the light in my eyepiece.
Dave
-----Original Message----- From: Brent Watson [mailto:brentjwatson@yahoo.com] Sent: Friday, February 21, 2003 11:06 AM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Mirrors
My 22 inch is f6.3. Only a couple of folks have required oxygen.
Brent
--- Greg Taylor <astronomus_maximus@yahoo.com> wrote:
Imagine a 30" f/7...
"Pass me that pressure suit willya?"
"Sure thing; oh, and watch out for those satellites, they come a little close. By the way, did you remember your parachute?"
"Naw, I'd just burn up if I fell anyhow..."
Cave made some sweet mirrors, so I've been told. You can probably get some nice high power views with it too.
Agreeing with what Chuck said, my 10 f/5.6 does a better job than it would if it were f/4.5, being mass produced and all. On a rare night of perfect seeing last summer (very far from here), I was able to push it to 580x without image degradation. I saw detail on Uranus! (Boy that dob driver comes in handy at those high magnifications)
--- David L Bennett <dlbennett@mac.com> wrote:
Don't forget considerations of field of view! My 10" f/5 Cave with a 40mm Tele Vue Wide Field gives some very impressive Milky Way shots ;)
On Friday, February 21, 2003, at 09:58 AM, Chuck Hards wrote:
Everyone should, unless there is a specific reason for going "short". Of course, legitimate reasons include transportation and ergonomics.
Brent's always been right-on in that department! :)
C.
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participants (6)
-
Brent Watson -
Chuck Hards -
David Dunn -
Greg Taylor -
Jim Gibson -
Richard Tenney