VintageBigBlue.org

 

Re: 1200GTO carrying 18" f/4.2 Newt?


Sep 4, 2008

 


----------------------------

#22881 Sep 4, 2008

I am building an 18" Dob for visual use which I would also like to

convert for astroimaging riding on my 1200GTO. Is the 1200 going to

be able to handle a truss based 18" scope about 65" long? The mirror

will be in a truss tube specifically designed for the 1200 not just

placing the dob truss on the 1200, total weight will be about 75lbs.



Thanks,

Joe



----------------------------

#22883 Sep 4, 2008

maybe

.

the issue I predict will be balance with the camera load fore in the newtonian design and wind load

.

my 18" f/12.6 classical cassegrain weighs in about 100 lbs on my 1200 mount and it works great there: so long as the wind is light to non existent

.

the key difference in my config and yours will be the balance point

.

here are pix of mine and some images taken using it.

.

www.narrowbandimaging.com/Stinger_gallery_page.htm

.

here are some recent shots taken at f/12.6 (5760mm focal length)

.

www.narrowbandimaging.com/dwb111_mk1sn2_pl9k_baader_halpha_page.htm

.

www.narrowbandimaging.com/ngc6888_mk1sn2_f12_pl9k_baader_ha_page.htm

.

www.narrowbandimaging.com/sh2_112_mk1sn2_f12_pl9k_baader_ha_page.htm

.

if things are well collimated (needs tweaking about once a month or so) and the winds light and the seeing typical it gives very nice star shapes.

.

.

.



--- On Thu, 9/4/08, joeastroc joeastroc@...> wrote:



From: joeastroc joeastroc@...>

Subject: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

To: ap-gto@yahoogroups.com

Date: Thursday, September 4, 2008, 10:08 AM













I am building an 18" Dob for visual use which I would also like to

convert for astroimaging riding on my 1200GTO. Is the 1200 going to

be able to handle a truss based 18" scope about 65" long? The mirror

will be in a truss tube specifically designed for the 1200 not just

placing the dob truss on the 1200, total weight will be about 75lbs.



Thanks,

Joe































[Non-text portions of this message have been removed]



----------------------------

#22884 Sep 4, 2008

I hope the answer is yes too :-). The mirror is 1.625" thick (Swayze Optical).



Joe







----- Original Message ----

From: Jerry A. Wilson JerryAWilson@...>

To: ap-gto@yahoogroups.com

Sent: Thursday, September 4, 2008 1:16:27 PM

Subject: Re: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?





Joe



I hope the answer is yes. I'm starting a similar project, with an 18

inch f/4. How thick is your mirror?



Jerry



At 10:08 AM 9/4/2008, you wrote:

>I am building an 18" Dob for visual use which I would also like to

>convert for astroimaging riding on my 1200GTO. Is the 1200 going to

>be able to handle a truss based 18" scope about 65" long? The mirror

>will be in a truss tube specifically designed for the 1200 not just

>placing the dob truss on the 1200, total weight will be about 75lbs.

>

>Thanks,

>Joe

>

>



[Non-text portions of this message have been removed]













[Non-text portions of this message have been removed]



----------------------------

#22885 Sep 4, 2008

In a message dated 09/04/08 12:55:38 Central Daylight Time, joeastroc@... writes:

I hope the answer is yes too :-). The mirror is 1.625" thick (Swayze Optical).









Interesting idea........however almost all 'Dob's I have seen and/or looked through do not have the rigidity to be imaging instruments.

They go out of collimation even when moving from 30 degrees above the horizon to 70 degrees. This would make imaging with one very frustrating.



Of course, you may already know this and are building your 18inch to address this.



Kent Kirkley





[Non-text portions of this message have been removed]



----------------------------

#22887 Sep 4, 2008

Kent brings up a good point: you need a "real" mirror support, not a sling...

--- On Thu, 9/4/08, KG KIRKLEY kgkirkley@...> wrote:



From: KG KIRKLEY kgkirkley@...>

Subject: Re: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

To: ap-gto@yahoogroups.com

Date: Thursday, September 4, 2008, 11:04 AM















In a message dated 09/04/08 12:55:38 Central Daylight Time, joeastroc@yahoo. com writes:

I hope the answer is yes too :-). The mirror is 1.625" thick (Swayze Optical).



Interesting idea........ however almost all 'Dob's I have seen and/or looked through do not have the rigidity to be imaging instruments.

They go out of collimation even when moving from 30 degrees above the horizon to 70 degrees. This would make imaging with one very frustrating.



Of course, you may already know this and are building your 18inch to address this.



Kent Kirkley



[Non-text portions of this message have been removed]































[Non-text portions of this message have been removed]







----------------------------

#22889 Sep 4, 2008

--- In ap-gto@yahoogroups.com, "joeastroc" joeastroc@...> wrote: >

> I am building an 18" Dob for visual use which I would also like to

> convert for astroimaging riding on my 1200GTO. Is the 1200 going to

> be able to handle a truss based 18" scope about 65" long? The mirror

> will be in a truss tube specifically designed for the 1200 not just

> placing the dob truss on the 1200, total weight will be about 75lbs.

>

> Thanks,

> Joe

>



Do not forget that you will need an excellent quality mirror cell with

an excellent 9 or 18 point floatation system and even edge support. A

Dobsonian "sling" design will not work.



I run my 16" on an AP1200 but I designed it first and foremost as a

Newtonian. You will need a mirror cell firmly mounted to a rigid truss

or tube and a rigid spider. My 16 has a 2 inch thick mirror, rolled

aluminum tube with aluminum compression rings to keep it round and the

complete scope weighs in at about 90 pounds. I looked at going with a

truss system but the additional cost of aluminum welding and build

precision deterred me at the time, even though I could have lightened

up the OTA by the weight of the rings I need to carry it, about 20 pounds.



----------------------------

#22890 Sep 4, 2008

Nice scope. Are the square cross section members Al or steel and

what's the primary f/ratio?



Jerry



At 10:32 AM 9/4/2008, you wrote:

>maybe

>

>the issue I predict will be balance with the camera load fore in the

>newtonian design and wind load

>

>my 18" f/12.6 classical cassegrain weighs in about 100 lbs on my

>1200 mount and it works great there: so long as the wind is light to

>non existent

>

>the key difference in my config and yours will be the balance point

>

>here are pix of mine and some images taken using it.

>

>www.narrowbandimaging.com/Stinger_gallery_page.htm>www.narrowbandimaging.com/Stinger_gallery_page.htm

>

>here are some recent shots taken at f/12.6 (5760mm focal length)

>

>www.narrowbandimaging.com/dwb111_mk1sn2_pl9k_baader_halpha_page.htm>www.narrowbandimaging.com/dwb111_mk1sn2_pl9k_baader_halpha_page.htm

>

>www.narrowbandimaging.com/ngc6888_mk1sn2_f12_pl9k_baader_ha_page.htm

>

>www.narrowbandimaging.com/sh2_112_mk1sn2_f12_pl9k_baader_ha_page.htm>www.narrowbandimaging.com/sh2_112_mk1sn2_f12_pl9k_baader_ha_page.htm

>

>if things are well collimated (needs tweaking about once a month or

>so) and the winds light and the seeing typical it gives very nice star shapes.

>

>

>

>

>--- On Thu, 9/4/08, joeastroc

>ahoo.com>joeastroc@...> wrote:

>

>From: joeastroc hoo.com>joeastroc@...>

>Subject: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

>To: mailto:ap-gto%40yahoogroups.com>ap-gto@yahoogroups.com

>Date: Thursday, September 4, 2008, 10:08 AM

>

>I am building an 18" Dob for visual use which I would also like to

>convert for astroimaging riding on my 1200GTO. Is the 1200 going to

>be able to handle a truss based 18" scope about 65" long? The mirror

>will be in a truss tube specifically designed for the 1200 not just

>placing the dob truss on the 1200, total weight will be about 75lbs.

>

>Thanks,

>Joe

>

>[Non-text portions of this message have been removed]

>

>





[Non-text portions of this message have been removed]



----------------------------

#22891 Sep 4, 2008

Steve makes excellent optics. I've looked through some of his

work. On mine I'm making the mirror myself. I just got the blank

from Newport Glass. It's the same thickness as yours. It'll be a

little lighter since I'm coring the primary for a cassegrain

option. It'll be a faster cassegrain than Richard's.



Jerry





.At 10:55 AM 9/4/2008, you wrote:

>I hope the answer is yes too :-). The mirror is 1.625" thick (Swayze Optical).

>

>Joe

>

>----- Original Message ----

>From: Jerry A. Wilson

>40verizon.net>JerryAWilson@...>

>To: mailto:ap-gto%40yahoogroups.com>ap-gto@yahoogroups.com

>Sent: Thursday, September 4, 2008 1:16:27 PM

>Subject: Re: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

>

>Joe

>

>I hope the answer is yes. I'm starting a similar project, with an 18

>inch f/4. How thick is your mirror?

>

>Jerry

>

>At 10:08 AM 9/4/2008, you wrote:

>

> >I am building an 18" Dob for visual use which I would also like to

> >convert for astroimaging riding on my 1200GTO. Is the 1200 going to

> >be able to handle a truss based 18" scope about 65" long? The mirror

> >will be in a truss tube specifically designed for the 1200 not just

> >placing the dob truss on the 1200, total weight will be about 75lbs.

> >

> >Thanks,

> >Joe

> >

> >

>

>[Non-text portions of this message have been removed]

>

>[Non-text portions of this message have been removed]

>

>





[Non-text portions of this message have been removed]







----------------------------

#22920 Sep 6, 2008

VERY interesting. I'm not an imager, but currently researching a few

points towards building a ~300MM F20 Dall-Kirkham. I was a little

concerned about the FL of the scope and how it would work on the

AP1200. Looks like it's a non issue. My pier was built using

Dennis's "Pier Design" paper, found in the links section.



Thanks.



Tom

Tucson, AZ



--- In ap-gto@yahoogroups.com, Richard Crisp rdcrisp@...> wrote:

>

> Thanks Joe

> .

> the Cassegrain configuration is a lot easier to balance but it

usually has a lot longer focal length too.

> .

> With a 5.7meter focal length I am able to get nice results

consistently with little effort in the guiding side: i use a Lumicon

Giant Easy Guider and an ST7E for guiding: even at 5.7 meters.

> .

> I do not use the PEM or any of the software to improve the PEM,.

Maybe I will someday but I am happy with the results I have now and

prefer less complexity versus more unless absolutely necessary.

> .

> there are a lot of single points of failure that can shoot us down

so I like to minimize them to improve my odds in the field.

> .

> Good luck. I'd recommend really making a different sort of mirror

cell. a holed primary is nice since it will not move laterally....

> .

>

>

> --- On Thu, 9/4/08, Joseph Colosi joeastroc@...> wrote:

>

> From: Joseph Colosi joeastroc@...>

> Subject: Re: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

> To: ap-gto@yahoogroups.com

> Date: Thursday, September 4, 2008, 11:07 AM

>

>

>

>

>

>

> Richard,

>

> Very impressive setup and results. I understand the possible

(probable) issues with balancing you mention. I will be imaging with

a DSLR and ST10, the DSLR should not be an issue as it is very

lightweight (less than many eyepieces). The ST10/w filters will be a

problem. I am willing to give it a shot, and by your results it looks

like it is at least in the realm of possibility.

>

> Thanks,

> Joe

>

> ----- Original Message ----

> From: Richard Crisp rdcrisp@sbcglobal. net>

> To: ap-gto@yahoogroups. com

> Sent: Thursday, September 4, 2008 1:32:28 PM

> Subject: Re: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

>

> maybe

>

> the issue I predict will be balance with the camera load fore in

the newtonian design and wind load

>

> my 18" f/12.6 classical cassegrain weighs in about 100 lbs on my

1200 mount and it works great there: so long as the wind is light to

non existent

>

> the key difference in my config and yours will be the balance point

>

> here are pix of mine and some images taken using it.

>

> www.narrowba ndimaging. com/Stinger_ gallery_page. htm

>

> here are some recent shots taken at f/12.6 (5760mm focal length)

>

> www.narrowba ndimaging. com/dwb111_ mk1sn2_pl9k_

baader_halpha_ page.htm

>

> www.narrowba ndimaging. com/ngc6888_ mk1sn2_f12_

pl9k_baader_ ha_page.htm

>

> www.narrowba ndimaging. com/sh2_112_ mk1sn2_f12_

pl9k_baader_ ha_page.htm

>

> if things are well collimated (needs tweaking about once a month or

so) and the winds light and the seeing typical it gives very nice

star shapes.

>

>

>

>

> --- On Thu, 9/4/08, joeastroc joeastroc@yahoo. com> wrote:

>

> From: joeastroc joeastroc@yahoo. com>

> Subject: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

> To: ap-gto@yahoogroups. com

> Date: Thursday, September 4, 2008, 10:08 AM

>

> I am building an 18" Dob for visual use which I would also like to

> convert for astroimaging riding on my 1200GTO. Is the 1200 going to

> be able to handle a truss based 18" scope about 65" long? The mirror

> will be in a truss tube specifically designed for the 1200 not just

> placing the dob truss on the 1200, total weight will be about 75lbs.

>

> Thanks,

> Joe

>

> [Non-text portions of this message have been removed]

>

> [Non-text portions of this message have been removed]

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

> [Non-text portions of this message have been removed]

>



----------------------------

#22921 Sep 6, 2008

the biggest problems I have are



1) the wind

2) portability is not so great since it takes some time to get setup and collimated when I tear down



I haven't moved it since the summer of 2006 though so it is sort of like an observatory scope while out in the backyard so that makes #2 a non-issue and usually the wind isn't a factor in my backyard.



----- Original Message -----

From: tucstargzr

To: ap-gto@yahoogroups.com

Sent: Saturday, September 06, 2008 5:08 PM

Subject: [ap-gto] Re: 1200GTO carrying 18" f/4.2 Newt?





VERY interesting. I'm not an imager, but currently researching a few

points towards building a ~300MM F20 Dall-Kirkham. I was a little

concerned about the FL of the scope and how it would work on the

AP1200. Looks like it's a non issue. My pier was built using

Dennis's "Pier Design" paper, found in the links section.



Thanks.



Tom

Tucson, AZ



--- In ap-gto@yahoogroups.com, Richard Crisp rdcrisp@...> wrote:

>

> Thanks Joe

>

> the Cassegrain configuration is a lot easier to balance but it

usually has a lot longer focal length too.

>

> With a 5.7meter focal length I am able to get nice results

consistently with little effort in the guiding side: i use a Lumicon

Giant Easy Guider and an ST7E for guiding: even at 5.7 meters.

>

> I do not use the PEM or any of the software to improve the PEM,.

Maybe I will someday but I am happy with the results I have now and

prefer less complexity versus more unless absolutely necessary.

>

> there are a lot of single points of failure that can shoot us down

so I like to minimize them to improve my odds in the field.

>

> Good luck. I'd recommend really making a different sort of mirror

cell. a holed primary is nice since it will not move laterally....

>

>

>

> --- On Thu, 9/4/08, Joseph Colosi joeastroc@...> wrote:

>

> From: Joseph Colosi joeastroc@...>

> Subject: Re: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

> To: ap-gto@yahoogroups.com

> Date: Thursday, September 4, 2008, 11:07 AM

>

>

>

>

>

>

> Richard,

>

> Very impressive setup and results. I understand the possible

(probable) issues with balancing you mention. I will be imaging with

a DSLR and ST10, the DSLR should not be an issue as it is very

lightweight (less than many eyepieces). The ST10/w filters will be a

problem. I am willing to give it a shot, and by your results it looks

like it is at least in the realm of possibility.

>

> Thanks,

> Joe

>

> ----- Original Message ----

> From: Richard Crisp rdcrisp@sbcglobal. net>

> To: ap-gto@yahoogroups. com

> Sent: Thursday, September 4, 2008 1:32:28 PM

> Subject: Re: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

>

> maybe

>

> the issue I predict will be balance with the camera load fore in

the newtonian design and wind load

>

> my 18" f/12.6 classical cassegrain weighs in about 100 lbs on my

1200 mount and it works great there: so long as the wind is light to

non existent

>

> the key difference in my config and yours will be the balance point

>

> here are pix of mine and some images taken using it.

>

> www.narrowba ndimaging. com/Stinger_ gallery_page. htm

>

> here are some recent shots taken at f/12.6 (5760mm focal length)

>

> www.narrowba ndimaging. com/dwb111_ mk1sn2_pl9k_

baader_halpha_ page.htm

>

> www.narrowba ndimaging. com/ngc6888_ mk1sn2_f12_

pl9k_baader_ ha_page.htm

>

> www.narrowba ndimaging. com/sh2_112_ mk1sn2_f12_

pl9k_baader_ ha_page.htm

>

> if things are well collimated (needs tweaking about once a month or

so) and the winds light and the seeing typical it gives very nice

star shapes.

>

>

>

>

> --- On Thu, 9/4/08, joeastroc joeastroc@yahoo. com> wrote:

>

> From: joeastroc joeastroc@yahoo. com>

> Subject: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

> To: ap-gto@yahoogroups. com

> Date: Thursday, September 4, 2008, 10:08 AM

>

> I am building an 18" Dob for visual use which I would also like to

> convert for astroimaging riding on my 1200GTO. Is the 1200 going to

> be able to handle a truss based 18" scope about 65" long? The mirror

> will be in a truss tube specifically designed for the 1200 not just

> placing the dob truss on the 1200, total weight will be about 75lbs.

>

> Thanks,

> Joe

>

> [Non-text portions of this message have been removed]

>

> [Non-text portions of this message have been removed]

>

>

>

>

>

>

>

>

>

>

>

>

>

>

>

> [Non-text portions of this message have been removed]

>











[Non-text portions of this message have been removed]







----------------------------

#22932 Sep 7, 2008

My mounts are in an observatory, so as long as the tube is kept below

the wall height neither 1 or 2 will be a problem ;-)



There are few luxuries like having a scope ready to go within one

minute of walking out the back door.



Tom

Tucson, AZ --- In ap-gto@yahoogroups.com, "Richard Crisp" rdcrisp@...> wrote:

>

> the biggest problems I have are

>

> 1) the wind

> 2) portability is not so great since it takes some time to get

setup and collimated when I tear down

>

> I haven't moved it since the summer of 2006 though so it is sort of

like an observatory scope while out in the backyard so that makes #2

a non-issue and usually the wind isn't a factor in my backyard.

>

>

> ----- Original Message -----

> From: tucstargzr

> To: ap-gto@yahoogroups.com

> Sent: Saturday, September 06, 2008 5:08 PM

> Subject: [ap-gto] Re: 1200GTO carrying 18" f/4.2 Newt?

>

>

> VERY interesting. I'm not an imager, but currently researching a

few

> points towards building a ~300MM F20 Dall-Kirkham. I was a little

> concerned about the FL of the scope and how it would work on the

> AP1200. Looks like it's a non issue. My pier was built using

> Dennis's "Pier Design" paper, found in the links section.

>

> Thanks.

>

> Tom

> Tucson, AZ

>

> --- In ap-gto@yahoogroups.com, Richard Crisp rdcrisp@> wrote:

> >

> > Thanks Joe

> >

> > the Cassegrain configuration is a lot easier to balance but it

> usually has a lot longer focal length too.

> >

> > With a 5.7meter focal length I am able to get nice results

> consistently with little effort in the guiding side: i use a

Lumicon

> Giant Easy Guider and an ST7E for guiding: even at 5.7 meters.

> >

> > I do not use the PEM or any of the software to improve the

PEM,.

> Maybe I will someday but I am happy with the results I have now

and

> prefer less complexity versus more unless absolutely necessary.

> >

> > there are a lot of single points of failure that can shoot us

down

> so I like to minimize them to improve my odds in the field.

> >

> > Good luck. I'd recommend really making a different sort of

mirror

> cell. a holed primary is nice since it will not move laterally....

> >

> >

> >

> > --- On Thu, 9/4/08, Joseph Colosi joeastroc@> wrote:

> >

> > From: Joseph Colosi joeastroc@>

> > Subject: Re: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

> > To: ap-gto@yahoogroups.com

> > Date: Thursday, September 4, 2008, 11:07 AM

> >

> >

> >

> >

> >

> >

> > Richard,

> >

> > Very impressive setup and results. I understand the possible

> (probable) issues with balancing you mention. I will be imaging

with

> a DSLR and ST10, the DSLR should not be an issue as it is very

> lightweight (less than many eyepieces). The ST10/w filters will

be a

> problem. I am willing to give it a shot, and by your results it

looks

> like it is at least in the realm of possibility.

> >

> > Thanks,

> > Joe

> >

> > ----- Original Message ----

> > From: Richard Crisp rdcrisp@sbcglobal. net>

> > To: ap-gto@yahoogroups. com

> > Sent: Thursday, September 4, 2008 1:32:28 PM

> > Subject: Re: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

> >

> > maybe

> >

> > the issue I predict will be balance with the camera load fore

in

> the newtonian design and wind load

> >

> > my 18" f/12.6 classical cassegrain weighs in about 100 lbs on

my

> 1200 mount and it works great there: so long as the wind is light

to

> non existent

> >

> > the key difference in my config and yours will be the balance

point

> >

> > here are pix of mine and some images taken using it.

> >

> > www.narrowba ndimaging. com/Stinger_ gallery_page. htm

> >

> > here are some recent shots taken at f/12.6 (5760mm focal length)

> >

> > www.narrowba ndimaging. com/dwb111_ mk1sn2_pl9k_

> baader_halpha_ page.htm

> >

> > www.narrowba ndimaging. com/ngc6888_ mk1sn2_f12_

> pl9k_baader_ ha_page.htm

> >

> > www.narrowba ndimaging. com/sh2_112_ mk1sn2_f12_

> pl9k_baader_ ha_page.htm

> >

> > if things are well collimated (needs tweaking about once a

month or

> so) and the winds light and the seeing typical it gives very nice

> star shapes.

> >

> >

> >

> >

> > --- On Thu, 9/4/08, joeastroc joeastroc@yahoo. com> wrote:

> >

> > From: joeastroc joeastroc@yahoo. com>

> > Subject: [ap-gto] 1200GTO carrying 18" f/4.2 Newt?

> > To: ap-gto@yahoogroups. com

> > Date: Thursday, September 4, 2008, 10:08 AM

> >

> > I am building an 18" Dob for visual use which I would also like

to

> > convert for astroimaging riding on my 1200GTO. Is the 1200

going to

> > be able to handle a truss based 18" scope about 65" long? The

mirror

> > will be in a truss tube specifically designed for the 1200 not

just

> > placing the dob truss on the 1200, total weight will be about

75lbs.

> >

> > Thanks,

> > Joe

> >

> > [Non-text portions of this message have been removed]

> >

> > [Non-text portions of this message have been removed]

> >

> >

> >

> >

> >

> >

> >

> >

> >

> >

> >

> >

> >

> >

> >

> > [Non-text portions of this message have been removed]

> >

>

>

>

>

>

> [Non-text portions of this message have been removed]

>







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