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How to piggyback a guidescope?

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#1 krockelein

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Posted 20 April 2019 - 09:22 AM

I am toying with the idea of replacing my current guide scope for one that is a more appropriate match for my 8" RC.  Currently I am using the Orion 30 mm mini with that all in one camera, and am looking at a 70mm or an 80mm.  Before I drop the cash, however, I'm trying to figure out how the mounting would actually work, and I can't figure it out.  The RC (GSO, steel tube) has a vixen bar on top that would be fantastic, but how?  I can't find brackets that would do the trick.  So does someone out there have any suggestions for ways that they have done this?  As always, I really appreciate any help/advice.



#2 beggarly

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Posted 20 April 2019 - 10:26 AM

2 dovetail clamps?

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#3 B 26354

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Posted 20 April 2019 - 10:54 AM

Depending on the guide-scope you end up with, there are a number of possibilities.

 

If the guide-scope comes with its own rings, and those are already attached to a Vixen dovetail-bar, you could just use a pair of these:

 

https://www.admacces...vetail-adapter/

 

...or something else from ADM:

 

https://www.admacces...-miscellaneous/

 

These and other possibilities are also available from High Point Scientific:

 

https://www.highpoin...tail attachment

 

If the guide-scope is mounted in a typical dual-mounting-ring setup, with its three plastic-tipped alignment-screws per ring format -- much like the typically somewhat "floppy" setup for finder-scopes -- there is the possibility that there will be some alignment-flexure between the guide-scope and the main scope, during hours-long tracking periods; especially with a heavier guide-scope like the ones that you're proposing.

 

Depending on how flexure-free you want the overall guide-scope attachment to be... you could also try to find clamshell rings for the guide-scope. I use a 60mm guide-scope from APM, and was unable to find commercially produced clamshell rings to match its 63mm-diameter OTA, so I ended up having some custom CNC-machined ones made by C-N member "Anurag Shevade".

 

Originally, the APM came with its own rings and dovetail, as is shown in this photo from the APM website

 

(https://www.apm-tele...xe-finder-scope):

 

APM 60mm.jpg

 

This is mine, on Mr. Shevade's CNC-machined dovetail and rings:

 

APM & Clamshell Rings on Vixen Rail 1.jpg

 

APM & Clamshell Rings on Vixen Rail 2.jpg

 

Hope this helps!  grin.gif


Edited by B 26354, 20 April 2019 - 11:00 AM.

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#4 petert913

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Posted 20 April 2019 - 10:55 AM

Since your scope already has a top rail,  you can buy two bases like this (from ADM or similar) to attach to the dovetail rail on top.

 

1OkOSZDm.jpg

 

Then put some rings on it like this (from Orion or similar):

 

SgakcQwm.jpg


Edited by petert913, 20 April 2019 - 10:56 AM.

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#5 krockelein

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Posted 20 April 2019 - 12:45 PM

Great information, thanks guys! 

 

@B 26354, with those clamshells it doesn't look like you can adjust the alignment of the guidescope, right?  Thank you for the contact info for the CN member.

 

@petert913, what are the keywords (descriptors?  names?)  of those?  I'd love to find some made by someone other than ADM with lower prices...



#6 RedLionNJ

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Posted 20 April 2019 - 01:08 PM

I would strongly recommend going with something akin to PeterT's recommendation. Rigidity is everything in mounting a guidescope.

 

I also doubt you'd find something much lower-priced than ADM's solutions. At least, not a sturdy, well-built solution. They're already usually the less-expensive among all the reputable manufacturers of robust mounting solutions. No flexure permitted!



#7 mohitk

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Posted 20 April 2019 - 01:20 PM

I bought the Stellarvue 50mm guidescope, so I went with these:

 

https://www.stellarv...idescope-rings/

 

They have bigger ones for their larger finderscope.

 

ADM Accessories does have a greater variety - for each "Series" look at "Dovetail Ring" - as an example, here's their V series adjustable from 70mm-90mm (get the right size based on scope you get):

 

https://www.admacces...justable-rings/

 

I wish they were cheaper as well!! The rings setup without the alignment screws looks more rock solid. ADM has aiming devices as well, but they are way too expensive for me. I will find out if I have flexure issues as I will be trying out my equipment soon.



#8 fewayne

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Posted 20 April 2019 - 01:36 PM

Y'all are gonna laugh at me for duct-taping a couple of D cells together for a mount and then duct-taping the guidescope to the main tube, aren't ya? I was getting about 0.75" RMS...



#9 B 26354

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Posted 20 April 2019 - 05:17 PM

@B 26354, with those clamshells it doesn't look like you can adjust the alignment of the guidescope, right?

True. I wondered about that myself. In reality, it's my feeling that the width of the guide-scope's FOV -- as compared to the imaging-scope's FOV -- will always provide enough guide-stars.

 

Also, as anyone who uses a "3-screw" dual-ring setup for their finder-scope will attest... unless it's absolutely necessary, aligning the finder with the main scope is done as seldom as possible, because it's just too painfully time-consuming.

 

Seems to me that having to perform that same procedure with your guide-scope, every time you select a new target, would get really old, really fast.

 

It would be interesting, though, to learn what percentage of AP-ers who use the "3-screw" rings or an "adjustable-platform" mount like this ADM one, as found on the High Point Scientific website...

 

https://www.highpoin...tail-mini-max-m

 

ADM Guide-scope Aiming Device.jpg

 

...actually use them to "zero in" on a guide-star, every time they choose a target.

 

Anyone out there willing to express their thoughts?  grin.gif


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#10 rkayakr

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Posted 20 April 2019 - 08:33 PM

Pic from another thread of a Stellarvue SV60EDS on a top rail using two dovetail shoes. As I mention in that post, I have never had to adjust the guide scope to find suitable stars for guiding.

 

https://www.cloudyni...newt/?p=9282919


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#11 B 26354

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Posted 20 April 2019 - 08:58 PM

@rkayakr -- Thanks for posting that link, and its comment about the sensitivity of modern guide cameras obviating the need for the ability to separately "aim" the guide-scope. I've had that pointed out to me by two other C-N members, both of whom happen to use the same Lacerta M-GEN autonomous auto-guider that I use.


Edited by B 26354, 20 April 2019 - 08:59 PM.

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#12 krockelein

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Posted 20 April 2019 - 09:13 PM

True. I wondered about that myself. In reality, it's my feeling that the width of the guide-scope's FOV -- as compared to the imaging-scope's FOV -- will always provide enough guide-stars.

 

Also, as anyone who uses a "3-screw" dual-ring setup for their finder-scope will attest... unless it's absolutely necessary, aligning the finder with the main scope is done as seldom as possible, because it's just too painfully time-consuming.

 

Seems to me that having to perform that same procedure with your guide-scope, every time you select a new target, would get really old, really fast.

 

It would be interesting, though, to learn what percentage of AP-ers who use the "3-screw" rings or an "adjustable-platform" mount like this ADM one, as found on the High Point Scientific website...

 

https://www.highpoin...tail-mini-max-m

 

attachicon.gif ADM Guide-scope Aiming Device.jpg

 

...actually use them to "zero in" on a guide-star, every time they choose a target.

 

Anyone out there willing to express their thoughts?  grin.gif

I’ve never had any real difficulty in aligning the little 30mm scope I’m using right now, but I only do it when I have had to remove it to use the camera for planetary imaging. But you’re saying that some folks re-align to center their selected guide star?  Apart from aesthetics! What’s the point of doing that?



#13 B 26354

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Posted 20 April 2019 - 10:07 PM

I think maybe these devices like the ADM one that I referenced, were originally developed for "older" guide cameras that perhaps weren't as sensitive as modern ones... so that even though the guide-scope's FOV was wider than the imaging scope's FOV, there still might not be an adequately-bright guide-star in that FOV.

 

My little Lacerta M-GEN II, on the other hand, is capable of guiding on a mag 12 star with only a 50mm guide-scope.  grin.gif


Edited by B 26354, 20 April 2019 - 11:06 PM.


#14 krockelein

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Posted 23 April 2019 - 09:39 PM

Ok, here's an update.  So far I haven't gotten a new scope because I started to wonder if flexure was indeed my problem.  Based on the football shaped stars, I thought it was.  So, I switched out the 3-pin rings I was using for the much more rigid rings that came with the Orion All-In-One camera (or did they come with the Ultra-Mini scope??) and placed the whole assembly so that one ring was on the scope and the other on the camera and tightened that sucker right down.  Well, my stars are looking much better.  Last night I was taking 10 minute NB subs with almost perfectly round stars!!  Ah, the sweet smell of victory...like napalm in the morning...


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#15 Pauls72

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Posted 24 April 2019 - 09:34 PM

The Dove  tail on the top of my AT6RC is just like the one on the bottom.

What I did was get a pair of Losmandy DVA clamps and mount them to the scope rings on my ST-80.

Then for my W.O. FLT98, I put on a dove tail bar upside down, so it matched the bottom.

Now I can move the 80mm guide scope between scopes very easily.

I did try Far Point and ADM clamps and was not happy with either one. Both of these are basically the exact same piece. The Losmandy DVA is much larger and heaftier.

 

http://www.losmandy.com/secondary.html

 

AT6RC-ST80-1s.jpg

Mounting.jpg

Mount-Small.jpg


Edited by Pauls72, 24 April 2019 - 09:35 PM.

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