Help me understand why a CDK14 is out of spec on the Mach2GTO #Mach2GTO


Karen Christen
 

Hey Deon,

I don’t see any marking on the capacity chart – will you check it and maybe send again?

In order to answer your question we could use more information.  What is the weight of the “bunch of extra equipment” that you’re hoping to include?  Where would it go?  E.g., on top of the OTA vs on the end.  A bit more context would be helpful.

Thanks!

Karen

AP

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of deonb
Sent: Thursday, December 29, 2022 12:00 AM
To: main@ap-gto.groups.io
Subject: [ap-gto] Help me understand why a CDK14 is out of spec on the Mach2GTO #Mach2GTO

 

Preface: I don't want to put a CDK14 on my Mach2GTO. I want to put a CDK12.5 on it with a bunch of extra equipment and I'm trying to read the capacity chart.

I know from many recommendations though that the CDK12.5 is within spec and the CDK14 is out for the Mach2GTO.

In trying to read the capacity graph to see if my equipment will fit, I realized I don't know how to read it... 

According to my numbers, the CDK14 is not only in capacity, it's on the lower side of it. I indicated it on this picture:
https://i.imgur.com/MZ4OlAe.jpeg

From experience, currently running an EdgeHD 14 on a Mach2GTO, I know this can't be true though. The EdgeHD 14 is very much at the edge of the Mach2GTO performance and you have to be very careful to precisely balance or it will stall the mount. I expect the CDK14 to be similar or worse... but that's not reflected in the chart above (at least how I read it).

What am I doing wrong?


--
Karen Christen
Astro-Physics


Bill Long
 

The AG Optical 12.5" iDK has very good optics in it. Sure it's 1.5" smaller aperture, but that diet makes it a perfect companion with the Mach 2 as one of it's biggest scope options. It's also $4k cheaper. Nice big 60mm corrected field. When I tested the combo my configuration was a little into the red on that chart but changing the camera package out to a much lighter CMOS would pull that back into the green no problem. 



From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Patrick Sparkman via groups.io <psparkman@...>
Sent: Thursday, December 29, 2022 8:12 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Help me understand why a CDK14 is out of spec on the Mach2GTO
 
As Bill noted, the CDK14 is 19" in diameter, so that puts you at the far right of the chart and right at the limit with just the base scope weight.  So any additional weight for the camera/focuser/filter wheel/anything else will put you high into the yellow or the red.


Roland Christen
 

For the weight, remember to include all mounting components such as dovetail plates, clamps, and also your imaging equipment. This can add considerable weight. The CDK14 weighs 48 lb all by itself. The additional components can easily bring that up to 60 lb. I would not put that much weight at such a diameter on the Mach2. This scope is more suited for an 1100 mount.

Roland



-----Original Message-----
From: deonb <deonb@...>
To: main@ap-gto.groups.io
Sent: Thu, Dec 29, 2022 12:01 am
Subject: Re: [ap-gto] Help me understand why a CDK14 is out of spec on the Mach2GTO

Ugh. groups.io mangled my link above. Here is my modified chart:

https://i.imgur.com/MZ4OlAe.jpeg

--
Roland Christen
Astro-Physics


Patrick Sparkman
 

As Bill noted, the CDK14 is 19" in diameter, so that puts you at the far right of the chart and right at the limit with just the base scope weight.  So any additional weight for the camera/focuser/filter wheel/anything else will put you high into the yellow or the red.


Bill Long
 

The OTA is 19" per their documentation so I highly doubt that's going to work.



From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Bill Long <bill@...>
Sent: Wednesday, December 28, 2022 11:01 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Help me understand why a CDK14 is out of spec on the Mach2GTO
 
One would need to measure the length with focuser and imaging train components all attached and the scope at focus. That will place it much longer than 35 inches for sure. If you only added the backfocus as a rough estimate of what length it would be then (and it would be longer) you are at 46 inches at that point. Weight is similar in that you need to weigh it with everything on the scope, including focuser, imaging train, accessories, etc. 

I am not sure what the height of the OTA attached would be. You would need the scope handy to measure this.

I was able to use a 12.5" AGO iDK on the Mach 2 with a very heavy FLI PL16803 camera setup. With light CMOS cameras, you would save a lot on weight. I am not sure it would be enough to make it work though.  



From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of deonb <deonb@...>
Sent: Wednesday, December 28, 2022 10:01 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Help me understand why a CDK14 is out of spec on the Mach2GTO
 
Ugh. groups.io mangled my link above. Here is my modified chart:

https://i.imgur.com/MZ4OlAe.jpeg


Bill Long
 

One would need to measure the length with focuser and imaging train components all attached and the scope at focus. That will place it much longer than 35 inches for sure. If you only added the backfocus as a rough estimate of what length it would be then (and it would be longer) you are at 46 inches at that point. Weight is similar in that you need to weigh it with everything on the scope, including focuser, imaging train, accessories, etc. 

I am not sure what the height of the OTA attached would be. You would need the scope handy to measure this.

I was able to use a 12.5" AGO iDK on the Mach 2 with a very heavy FLI PL16803 camera setup. With light CMOS cameras, you would save a lot on weight. I am not sure it would be enough to make it work though.  



From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of deonb <deonb@...>
Sent: Wednesday, December 28, 2022 10:01 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Help me understand why a CDK14 is out of spec on the Mach2GTO
 
Ugh. groups.io mangled my link above. Here is my modified chart:

https://i.imgur.com/MZ4OlAe.jpeg


deonb
 

Ugh. groups.io mangled my link above. Here is my modified chart:

https://i.imgur.com/MZ4OlAe.jpeg


deonb
 

Preface: I don't want to put a CDK14 on my Mach2GTO. I want to put a CDK12.5 on it with a bunch of extra equipment and I'm trying to read the capacity chart.

I know from many recommendations though that the CDK12.5 is within spec and the CDK14 is out for the Mach2GTO.

In trying to read the capacity graph to see if my equipment will fit, I realized I don't know how to read it... 

According to my numbers, the CDK14 is not only in capacity, it's on the lower side of it. I indicated it on this picture:
https://i.imgur.com/MZ4OlAe.jpeg

From experience, currently running an EdgeHD 14 on a Mach2GTO, I know this can't be true though. The EdgeHD 14 is very much at the edge of the Mach2GTO performance and you have to be very careful to precisely balance or it will stall the mount. I expect the CDK14 to be similar or worse... but that's not reflected in the chart above (at least how I read it).

What am I doing wrong?