How to properly pick Dovetails and Rings

[Hiddenpalm]

I've been looking for a dovetail and rings in various places online but I don't know what exactly to look for. For example at ADM they have everything divided in V, D, DV, and MDS series. I don't know what they all stand for. When I look at rings I'm not exactly sure what to get.

I'm trying to piggy back a 1.5kg (3.5 pound) William Optics Zenithstar 66mm scope on a Nexstar 8SE to use the 66mm as a guiding scope and for comparison views. They also look really great together, since they're the same color. I've seen pictures of someone who did the same thing, except it was on a 6SE.

The WO ZS 66mm has a tube diameter of 75mm (2.95") and a tube length of 360mm (14.2") when fully extended. The PDF manual for the ZS shows 100mm rings under recommended products. Should I look for "100mm" rings when shopping for them? Or is there more to it?

Any advice on what I should look for when shopping for a dovetail and rings to attach the Zenithstar on the 8SE would be greatly appreciated. A simple primer on what to know and what to do would be appreciated even more.

[DRT]

Hi,

The ADM naming convention is quite simple once you know it:

V Series = Vixen-style dovetails, like those supplied with most scopes when new

D Series = 3" wide Losmandy-style dovetails, designed for heavier scopes or when you need maximum stability

DV Series are clamps and bars that are interchangeable between D and V series bars

MDS = Mini dovetails and clamps designed specifically for mounting guide scopes  

These bars fit your 8SE...https://www.firstlightoptics.com/adm-mini-dovetail-series/adm-mini-dovetail-bar-celestron-8.html

As for the rings, you should be looking at the style with three long screws in each ring used the hold and align the guide scope. The ring will be significantly larger that the outer diameter of your guide scope to allow for these screws to provide a suitable amount of adjustment. 100mm sounds about right but the spec for the rings should tell you what the minimum and maximum scope diameter can be and you should look for something that accommodate your 75mm scope.

These would do the trick...https://www.firstlightoptics.com/adm-mini-dovetail-series/adm-mini-dovetail-guidescope-rings.html

 

Hope that helps.

[LightBucket]

I had the same scope as you piggybacked, and the only rings available for it are the 76mm Skywatcher ones...I searched everywhere and could not find any others with a 76mm internal diameter...

These are the ones I used..

https://www.365astronomy.com/SkyWatcher-76mm-Tube-Mounting-Rings.html

Sorry forgot to say, you certainly don’t want 100mm rings they will be far far too big....

[DRT]

4 hours ago, LightBucket said:

Sorry forgot to say, you certainly don’t want 100mm rings they will be far far too big....

You linked to tube rings rather than guide scope rings. How did you align the guide scope with your C8 without any adjustment bolts?

[LightBucket]

3 hours ago, DRT said:

You linked to tube rings rather than guide scope rings. How did you align the guide scope with your C8 without any adjustment bolts?

Because as long as the guidescope is as close as possible then all will be good and with a fixed bar on top of my scope and fixed rings then they are pretty much perfectly parallel.. and also no chance of flexure which you can get with guidescope rings....worked great for me and got lovely round stars with 15min subs...

[DRT]

11 minutes ago, LightBucket said:

Because as long as the guidescope is as close as possible then all will be good and with a fixed bar on top of my scope and fixed rings then they are pretty much perfectly parallel.. and also no chance of flexure which you can get with guidescope rings....worked great for me and got lovely round stars with 15min subs...

Disclaimer: this is a dedicated Observer asking a Astro Photographer about guide-scopes  

 

That all sounds perfectly good, so why do guide scope rings have adjustment screws? Why wouldn't everyone just use your solution to the problem?

[LightBucket]

4 minutes ago, DRT said:

Disclaimer: this is a dedicated Observer asking a Astro Photographer about guide-scopes  

 

That all sounds perfectly good, so why do guide scope rings have adjustment screws? Why wouldn't everyone just use your solution to the problem?

Very  good question and I am sure there is a good answer too, I would guess it’s because with guidescope rings you can get absolute perfect alignment, which i suppose would make the guiding software not work so hard, but I have never seen the need with modern sub pixel guiding software.... 

Also not all guidescope will have perfectly fitting rings and so adjustable ones are then the answer, but many scopes do which people use for guiding rather than dedicated guide scopes.. I have an 80mm Altair Astro dedicated guidescope now and have to use adjustable rings as there are no fixed rings that fit it ..

Someone with much more experience than me will be along soon to give you a better answer... or I hope they will...

[DRT]

5 minutes ago, LightBucket said:

Very  good question and I am sure there is a good answer too, I would guess it’s because with guidescope rings you can get absolute perfect alignment, which i suppose would make the guiding software not work so hard, but I have never seen the need with modern sub pixel guiding software.... 

Also not all guidescope will have perfectly fitting rings and so adjustable ones are then the answer, but many scopes do which people use for guiding rather than dedicated guide scopes.. I have an 80mm Altair Astro dedicated guidescope now and have to use adjustable rings as there are no fixed rings that fit it ..

Someone with much more experience than me will be along soon to give you a better answer... or I hope they will...

Thanks, @LightBucket, I'm really hoping the OP will get the best advice before he makes a purchase. I have the benefit of not needing a guide scope  

[Hiddenpalm]

First of all, THANK YOU! This is information that should of been explained at ADM. It's been very helpful. I love the Lounge.

Regarding the rings Lightbucket posted, it does have thumb screws for adjustments. "By loosening the thumbscrews, the telescope can be easily balanced and rotated." Whether that is less or more adjustable than standard ones, I'm not sure. It is a very good price compared to others, by far. But weighs a bit more than others, 0.80kg (1.76lbs). I'm thinking, It also might not be as steady because only one screw connects it to the dovetail.

DRT, I can see the usefulness for the MDS as they are lighter. But I am torn if I should go for the V series orange dovetail at 0.56kg or the MDS you posted for 0.34kg. The problem is I am not sure how much more weight the 8SE can take and the orange bar might be the kicker for me. The WO ZS 66mm is already at 1.58kg (3.5lbs). And I still want to add a green laser to it. I wrote the dealer, Highpoint Scientific, about it but still haven't gotten a reply yet.

Here are the builds I'm looking at.

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

[DRT's recommendation]

MDS-C8- MDS Series Dovetail Bar for Celestron 8″ SCT Telescope - 12oz (0.75lbs) (0.34kg)

MDS-R100- MDS Series dovetail Ring Set. 100mm Adjustable Rings - - 18oz (1.12lbs)

Total 30oz (1.87lbs) (0.84kg)

1.87 + 3.5(WO ZS 66mm) = 5.37lbs (2.43kg)

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

[DRT's recommendation with a 90mm ring, since Lightbucket suggested the 100mm is too big]

MDS-C8- MDS Series Dovetail Bar for Celestron 8″ SCT Telescope - 12oz (0.75lbs) (0.34kg)

MDS-R90- MDS Series dovetail Ring Set. 90mm Adjustable Rings - 16oz (1 pound)

Total 28oz (1.75lbs) (0.79kg)

3.5(WO ZS 66mm) + 1.75 = 5.25lbs (2.38kg)

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

This is the one I'm leaning towards since it has an orange bar, even though it weighs slightly more than the MDS.

VR90- V Series Dovetail Ring Set. 90mm Adjustable Rings - 20oz (1.25lbs) (0.56kg)

VC8- V Series Dovetail Bar for Celestron 8″ SCT Telescope. Orange Anodized - 14oz (0.87lbs) (0.34kg)

Total 34oz (2.12lbs) (0.96kg)

2.12 + 3.5(WO ZS 66mm) = 5.62lbs (2.54kg)

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

So what do you guys think? Can my 8SE handle 2.54kg (5.62lbs)? Would it work? I still want to add a green laser pointer. I haven't seen a MDS orange dovetail bar. I really want an orange bar. Please don't judge me, lol

[DRT]

I don't think the weight is an issue with these options provided you place the guide scope in a place that does not affect the balance of the set-up.

For what it is worth, I disagree with LightBucket's assertion that 100mm rings are too big for your scope. They are recommended in your spec for a reason. That reason might be that you need to be able to insert the scope into the rings and the dew shield and or focuser will require more room than the diameter of your OTA. It also provides sufficient movement in the adjustment screws to achieve perfect alignment. 

[DRT]

And I forgot to mention, orange and black look the same in the dark ? 

[Hiddenpalm]

16 minutes ago, DRT said:

And I forgot to mention, orange and black look the same in the dark ? 

Ahhhhhh man, so true. Ideally I would want to set up before the sun goes down, giving the ladies plenty of time to know where the fun will be when it is dark. So I want to look good. But yeah, at the end of the day, you're absolutely correct.
 

17 minutes ago, DRT said:

For what it is worth, I disagree with LightBucket's assertion that 100mm rings are too big for your scope. They are recommended in your spec for a reason. That reason might be that you need to be able to insert the scope into the rings and the dew shield and or focuser will require more room than the diameter of your OTA. It also provides sufficient movement in the adjustment screws to achieve perfect alignment. 

I was thinking the same, which is why I looked at the 90mm, which claims to adjust for "60mm – 80mm" and slightly lighter than a 100mm. Lightbucket's ring was 76mm designed for a 70mm refracter. Are you suggesting the 90mm might be too small as well?

[DRT]

14 minutes ago, Hiddenpalm said:

I would want to set up before the sun goes down, giving the ladies plenty of time to know where the fun will be when it is dark.

Rule 1: don't use astronomy as a chat-up line with the ladies ? 

15 minutes ago, Hiddenpalm said:

I was thinking the same, which is why I looked at the 90mm, which claims to adjust for "60mm – 80mm" and slightly lighter than a 100mm. Lightbucket's ring was 76mm designed for a 70mm refracter. Are you suggesting the 90mm might be too small as well?

Measure the widest part of your guide scope and make sure it will fit through whichever rings you choose. The dew shield on that WO66 looks much bigger than the tube diameter. Both need to fit through the rings, as does the focuser if you need to back it in ?

 

[LightBucket]

On 05/07/2018 at 19:21, DRT said:

I don't think the weight is an issue with these options provided you place the guide scope in a place that does not affect the balance of the set-up.

For what it is worth, I disagree with LightBucket's assertion that 100mm rings are too big for your scope. They are recommended in your spec for a reason. That reason might be that you need to be able to insert the scope into the rings and the dew shield and or focuser will require more room than the diameter of your OTA. It also provides sufficient movement in the adjustment screws to achieve perfect alignment. 

When I said too big for the scope, I meant as fixed rings not guide scope adjustable rings...sorry for the confusion, as guide scope adjustable rings they would be perfect in size..

[newbie alert]

I use 75mm adm ones on my frac..

I have got some 125mm ones I used with a 80mm guidescope piggybacked on my 8 inch sct (mds)

If you want orange..look up celestron guide rails

[brrttpaul]

Got a similar problem with my MAK127 and an ed 80, ATM they are both connected via tube rings and two bars but they are not perfectly aligned and the only thing I have found is a bar that you can adjust but its expensive, the other option for me is a dual side by side rig, again I am not sure if this will work or not

[Hiddenpalm]

DRT was right, the 90mm rings are too small for the dew shield of the WO ZS 66mm, so I went for the100mm ring. I couldn't help myself and got the orange bar. But all for naught.

The dealer just got back to me (days later) and informed me the nexstar 8SE mount is already at over capacity with the 8SE scope. And that adding anything to it would be bad for the motor not allowing it to track properly, which is the first time I'm hearing this. Most complaints are about its lack of steadiness. Granted, I'm not too serious about doing AP yet, I'm just checking things and slowly learning about everything, so I was willing to struggle with the shakiness as long as I learn something. I've been planning to update the mount and get a real camera next year meanwhile learning the ropes with what I got it. I was going to get the wedge to turn the mount into an equatorial one, figuring the extra weight would help with the steadiness, but it still wouldn't fix the issue about too much weight on the motor.

So maybe sometime next year I'll get a cool new mount like the cgem (40lbs / 18.14kg capacity) with orange nobs and orange screws. ?

[Hiddenpalm]

10 hours ago, brrttpaul said:

Got a similar problem with my MAK127 and an ed 80, ATM they are both connected via tube rings and two bars but they are not perfectly aligned and the only thing I have found is a bar that you can adjust but its expensive, the other option for me is a dual side by side rig, again I am not sure if this will work or not

I'm a total noob, but that does sound weird, being that the rings should allow you to make adjustments. Maybe your mak 127 needs to be collimated?

Newbie Alert, I love your toys. That's the "Ferrari" WO ZS 66mm right? I love that old look. I'm not too fond of their latest ones with white tubes. Mine is in Celestron orange. The older ones are heavier though, but they're so hot.

[newbie alert]

3 hours ago, Hiddenpalm said:

DRT was right, the 90mm rings are too small for the dew shield of the WO ZS 66mm, so I went for the100mm ring. I couldn't help myself and got the orange bar. But all for naught.

The dealer just got back to me (days later) and informed me the nexstar 8SE mount is already at over capacity with the 8SE scope. And that adding anything to it would be bad for the motor not allowing it to track properly, which is the first time I'm hearing this. Most complaints are about its lack of steadiness. Granted, I'm not too serious about doing AP yet, I'm just checking things and slowly learning about everything, so I was willing to struggle with the shakiness as long as I learn something. I've been planning to update the mount and get a real camera next year meanwhile learning the ropes with what I got it. I was going to get the wedge to turn the mount into an equatorial one, figuring the extra weight would help with the steadiness, but it still wouldn't fix the issue about too much weight on the motor.

So maybe sometime next year I'll get a cool new mount like the cgem (40lbs / 18.14kg capacity) with orange nobs and orange screws. ?

For doing astro photography with a 8 inch sct you will need at least a cgem sized mount..also you might want to look at oag instead of a separate guidescope..for reasons of mirror shift..

[LightBucket]

3 hours ago, Hiddenpalm said:

DRT was right, the 90mm rings are too small for the dew shield of the WO ZS 66mm, so I went for the100mm ring. I couldn't help myself and got the orange bar. But all for naught.

The dealer just got back to me (days later) and informed me the nexstar 8SE mount is already at over capacity with the 8SE scope. And that adding anything to it would be bad for the motor not allowing it to track properly, which is the first time I'm hearing this. Most complaints are about its lack of steadiness. Granted, I'm not too serious about doing AP yet, I'm just checking things and slowly learning about everything, so I was willing to struggle with the shakiness as long as I learn something. I've been planning to update the mount and get a real camera next year meanwhile learning the ropes with what I got it. I was going to get the wedge to turn the mount into an equatorial one, figuring the extra weight would help with the steadiness, but it still wouldn't fix the issue about too much weight on the motor.

So maybe sometime next year I'll get a cool new mount like the cgem (40lbs / 18.14kg capacity) with orange nobs and orange screws. ?

Hmmmm, not sure I agree with it being over capacity, BUT when you add something to the top of your scope you need to add matching weight to the bottom, (by way of a weight balance system) and slide forward or back to balance on both axis, I did this with mine and got perfect balance and it tracked beautifully... and yes you need to put on a wedge and make it equatorial, this might be what the guy means, but if you ad weight and get perfect balance the motors are not really doing anymore work...