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Questions for the dobsters in here

dob equipment Orion reflector
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#1 makeitso

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Posted 01 July 2020 - 08:24 PM

A few days ago, I purchased a used telescope, an XT12i. There are a few issues I would like to address. I’ll start with one most important to me right now, the base. The base on this is not steady. I’m not sure if this is a common problem or if the one I have is worse than normal. Anyway, I would like to stiffen it up. I’m looking to put some sort of gussets in to do that.

 

What do others do to stiffen up there dob mounts? I’m looking at Home Depot, they have some stamped sheet metal gussets for under a dollar each. I don’t want to spend much on this mount as I plan on getting another one at some point, probably. I figure 6 would do it, one on each side board inside and outside, same for the front board. Two more inside for the sides to the front board (maybe two for each side board). On the sides, would higher or lower be best (if using one per board)?
 

I’m going for function, quick, easy and inexpensive, although, function is most important. I can go to HD right now and be finished in two hours if I take my time. I don’t know if this will accomplish the result I’m wanting to get though. Has anyone tried this? I can paint them flat black so they don’t stand out to much. All it would take is drilling a few holes, screwing in some screws and done.

 

In any case, any recommendations are welcome.

 

The other issue is “i” part doesn’t work. It does not go to the correct place for objects. I’ve done some reading on this subject. I’m sure there’s more out there. Again, recommendations are welcome for this too, I would like it to work but it’s not that important. The COL powers up, I’ve aligned it. When I move it the numbers change, it does not end up pointing at the right place though. I’ve read where the sensor slips.

 

Thanks, Jack



#2 moonrakercat

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Posted 01 July 2020 - 08:55 PM

Sounds like your base has been dropped or damaged somehow - they shouldn't be that loose.

 

Not sure what gussets your looking at from hd - but I used 90 degree shelf brackets from hd - I think they come in black - do a good job of stiffening up the base (you can put them inside the base & the tube should just clear)  - just remember to use something like a pan head steel self tapping screw - do not use wood screws !!!  they break up the particle board & you will end up with a broken mess if you have to remove them - they don't hold near as well either.   Also - I think your base might be 3/4" thick - so you will need 5/8" long screws  - want to be careful of that too.  

 

Can't help you with the goto - sorry.


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#3 eyeoftexas

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Posted 01 July 2020 - 09:33 PM

How far off does the pointing end up?  I have the XX12g, and hence full SynScan GoTo, but often I find that the GoTo gets close, but may be more than 1° off which means that the object is outside the FOV for most of my eyepieces.  I thus have to slew around a bit follow star patterns to find the object.  Using the SynScan Pro on my iPad allows me to align with each object I go to while connected via WiFi, and that tends get the pointing more accurate.  


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#4 havasman

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Posted 01 July 2020 - 10:10 PM

If the base is wobbly and/or loose there's no chance the intelliscope function will be accurate. If you think about it just a little you'll see how the uncontrolled base hamstrings the pointing function. When you stabilize it, take particular care to get everything square to the groundboard, the bottom plate to which everything is built. If you can get the back and sides 90 degree square to the ground board and to each other it's likely the intelliscope function may be greatly improved. Check to see that the round pads on which the tube rides up and down are in good shape and that the bosses on the tube that ride on them are too. At that point you may expect a test of the intelliscope system valid. The manual for the XTi scopes say clearly that the goal of the system is to put an selected object w/in the field of the finder and my experience is that it does that well.

 

Many of us have these scopes. My 1st scope was/is an XT10i I bought 4th hand off ebay 'cause I didn't know better and it's been great. I've been all through it as many of us have. We can probably help you as you get this one up & running.


Edited by havasman, 01 July 2020 - 10:14 PM.

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#5 icomet

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Posted 01 July 2020 - 10:23 PM

Your DSC's are magnetic not optical to start with, I believe.

 

I've experienced slipping with optical encoders, but never worked with

the magnetic ones.

 

I think I'm correct on this, after consideration. Long day.


Edited by icomet, 01 July 2020 - 10:29 PM.


#6 kfiscus

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Posted 01 July 2020 - 10:26 PM

Without being there in person to see your dob base, here are some ideas for you to consider:  The base may have been taken apart too many times.  The particle board can really suffer and the bolt holes can get enlarged.  You could take the base apart one last time and only one piece at a time using 15-minute epoxy on the edges and in the holes.  Slipping a half piece of wooden toothpick into each bolt hole can get things to tighten up nicely.  As mentioned above, be sure to use a square to get everything plumb.  The advice you have already gotten is good.  Let us know how you do.


Edited by kfiscus, 02 July 2020 - 12:07 AM.

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#7 havasman

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Posted 01 July 2020 - 10:39 PM

Your DSC's are magnetic not optical to start with, I believe.

 

I've experienced slipping with optical encoders, but never worked with

the magnetic ones.

 

I think I'm correct on this, after consideration. Long day.

The sensors are Hall-Effect sensors, so yes magnetic in nature and as far as I know unique in the hobby. It's an old tech used in automotive ignition systems in the '70's.



#8 gwlee

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Posted 01 July 2020 - 11:29 PM

Worst case, Ken Fiscus, who is participating in this thread, might be able make you a plywood base to replace the stock base. He made one for me a few years ago, and he had some good suggestions here for repairing the stock base if that’s the problem. Do you know whether the shakiness you are seeing is the typical shakiness or worse than normal? 
 

Regarding the Intelliscope feature, Orion is getting very hard nosed about not selling replacement parts or providing technical support to anyone other than the original owner, so hope you don’t need parts. If you do, sometimes you can find used parts on the Cloudy Nights classifieds. I sold some there a few years ago. I have had some luck getting Orion to sell me parts even though I wasn’t the original owner, it seems to be hit and miss. The good news is that you don’t need the DSCs to starhop. 


Edited by gwlee, 01 July 2020 - 11:30 PM.


#9 Asbytec

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Posted 02 July 2020 - 07:52 AM

The base on this is not steady. I’m not sure if this is a common problem or if the one I have is worse than normal. Anyway, I would like to stiffen it up.

 

Thanks, Jack

Not sure what you mean by steady, whether it's loose or just shakes a lot. If the latter, I cannot stress enough how important it is to ensure your feet are in line with your altitube bearings (if you have altitude bearings instead of a lazy Susan configuration). Mine had the shakes - not steady - pretty bad. It made high power focusing difficult. After replacing the feet under the bearings, the improvement was very dramatic. Unbelievable how signifigant that small mod is. From shakes to rock steady in 15 minutes. Serious. I no longer feel the need for a 10:1 fine focus knob. 


Edited by Asbytec, 02 July 2020 - 07:54 AM.


#10 makeitso

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Posted 02 July 2020 - 09:42 AM

How far off does the pointing end up?  I have the XX12g, and hence full SynScan GoTo, but often I find that the GoTo gets close, but may be more than 1° off which means that the object is outside the FOV for most of my eyepieces.  I thus have to slew around a bit follow star patterns to find the object.  Using the SynScan Pro on my iPad allows me to align with each object I go to while connected via WiFi, and that tends get the pointing more accurate.  

The pointing is way off. No measurement but significantly off in azimuth, no so bad in altitude. It seems the azimuth is the one that’s off the most. The altitude seems decent but hard to tell with the azimuth off so much, it’s not even close.

 

If the base is wobbly and/or loose there's no chance the intelliscope function will be accurate. If you think about it just a little you'll see how the uncontrolled base hamstrings the pointing function. When you stabilize it, take particular care to get everything square to the groundboard, the bottom plate to which everything is built. If you can get the back and sides 90 degree square to the ground board and to each other it's likely the intelliscope function may be greatly improved. Check to see that the round pads on which the tube rides up and down are in good shape and that the bosses on the tube that ride on them are too. At that point you may expect a test of the intelliscope system valid. The manual for the XTi scopes say clearly that the goal of the system is to put an selected object w/in the field of the finder and my experience is that it does that well.

 

Many of us have these scopes. My 1st scope was/is an XT10i I bought 4th hand off ebay 'cause I didn't know better and it's been great. I've been all through it as many of us have. We can probably help you as you get this one up & running.

It’s not terrible, it wiggles in even the slightest breeze. I did find out last night, I had not checked the base the side board bolts. After tightening them down, it was better. Still to wobbly for my liking though. I did take the base apart and cleaned it up. I cleaned the bearings with alcohol and lubed them with soap. This was after I had already tried the push to. The seller did say it has never worked.

 

Worst case, Ken Fiscus, who is participating in this thread, might be able make you a plywood base to replace the stock base. He made one for me a few years ago, and he had some good suggestions here for repairing the stock base if that’s the problem. Do you know whether the shakiness you are seeing is the typical shakiness or worse than normal? 
 

Regarding the Intelliscope feature, Orion is getting very hard nosed about not selling replacement parts or providing technical support to anyone other than the original owner, so hope you don’t need parts. If you do, sometimes you can find used parts on the Cloudy Nights classifieds. I sold some there a few years ago. I have had some luck getting Orion to sell me parts even though I wasn’t the original owner, it seems to be hit and miss. The good news is that you don’t need the DSCs to starhop. 

I’m trying to save money right now. I do want to get a better base at some point. I want to get the wheel barrow handles for it too. Can’t afford it right now, have to go cheap.

 

Not sure what you mean by steady, whether it's loose or just shakes a lot. If the latter, I cannot stress enough how important it is to ensure your feet are in line with your altitube bearings (if you have altitude bearings instead of a lazy Susan configuration). Mine had the shakes - not steady - pretty bad. It made high power focusing difficult. After replacing the feet under the bearings, the improvement was very dramatic. Unbelievable how signifigant that small mod is. From shakes to rock steady in 15 minutes. Serious. I no longer feel the need for a 10:1 fine focus knob. 

I’m not completely sure what you mean here, the feet are static and in the same position relative to the ground. When I turn the tube, the altitude bearing spin around the base where the feet are. Depending on where the tube is pointing, the altitude bearings may or may not be directly over the feet. This base has three feet so the altitude bearings are never both over a foot at the same time.

 

Sounds like your base has been dropped or damaged somehow - they shouldn't be that loose.

 

Not sure what gussets your looking at from hd - but I used 90 degree shelf brackets from hd - I think they come in black - do a good job of stiffening up the base (you can put them inside the base & the tube should just clear)  - just remember to use something like a pan head steel self tapping screw - do not use wood screws !!!  they break up the particle board & you will end up with a broken mess if you have to remove them - they don't hold near as well either.   Also - I think your base might be 3/4" thick - so you will need 5/8" long screws  - want to be careful of that too.  

 

Can't help you with the goto - sorry.

I don’t think it’s been dropped, no signs of that I can see. I may try this. I didn’t think of shelf brackets. I was looking at corner gussets made from stamped steel. The shelf brackets seem like a better idea. How high from the bottom did you put the brackets? What size of bracket did you use? I’m thinking 6” would do it.

 

Last night before observing I did tighten the bolts holding the base to the sides and front board (didn’t tighten these the first time). That helped a bunch but still a little wobbly in a breeze

 

I have no idea what a normal amount of wobble is for these. I don’t have much experience with dobs. The dobs I’ve used seemed less wobbly that this one is.

 

As for the push to, I’ll update on that. I planning to do the test outlined in the manual. I’ve found it online and printed it.

 

Thanks for the replies, This is a work in progress as is most of my telescope gear.

 

Jack



#11 havasman

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Posted 02 July 2020 - 10:31 AM

FWIW, normal amount of wobble very closely approaches zero. The job of the support system for a scope, any scope, involves holding the optics steady enough to allow you to see objects very far away. Any movement at the base will multiply at the long end to make viewing impossible.

 

Ken Fiscus posted some ideas above that you should consider carefully. He is a professional supplier of Dob scope bases and has built more of them than the rest of us combined.


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#12 makeitso

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Posted 02 July 2020 - 10:50 AM

Without being there in person to see your dob base, here are some ideas for you to consider:  The base may have been taken apart too many times.  The particle board can really suffer and the bolt holes can get enlarged.  You could take the base apart one last time and only one piece at a time using 15-minute epoxy on the edges and in the holes.  Slipping a half piece of wooden toothpick into each bolt hole can get things to tighten up nicely.  As mentioned above, be sure to use a square to get everything plumb.  The advice you have already gotten is good.  Let us know how you do.

Ken, this suggestion seems to be popular. I may try the shelf brackets first. If that doesn’t do it , this is what I’ll do next. In conjunction to the shelf brackets, this should make it rock solid. A new base is somewhere on the future, funding available of course.

 

FWIW, normal amount of wobble very closely approaches zero. The job of the support system for a scope, any scope, involves holding the optics steady enough to allow you to see objects very far away. Any movement at the base will multiply at the long end to make viewing impossible.

 

Ken Fiscus posted some ideas above that you should consider carefully. He is a professional supplier of Dob scope bases and has built more of them than the rest of us combined.

Thanks Dick, duly noted and would be the next step after shelf brackets.

 

Thanks to all who have replied and keep them coming please!

 

Jack



#13 Jon Isaacs

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Posted 02 July 2020 - 10:56 AM

I have no idea what a normal amount of wobble is for these. I don’t have much experience with dobs. The dobs I’ve used seemed less wobbly that this one is.

 

 

Jack:

 

As far as I know, the only Dobs you have used are mine and based on my experience, they are probably less wobbly than most.  I would just use it for a while, you get accustomed to it .  

 

Also, a two speed focuser is a real help.  Very often the process of focusing incites vibration and the two speed means you can use a light touch and avoid vibration.

 

My friend Jeff calls them Dobbles.. 

 

Jon


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#14 havasman

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Posted 02 July 2020 - 11:00 AM

Thanks Dick, duly noted and would be the next step after shelf brackets.

It's your choice for sure. But it makes more sense to me to use the fixes Ken suggests first. If your braces are not adequate they will have to be removed to do the other work, weakening their potential when reattached.


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#15 makeitso

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Posted 02 July 2020 - 11:21 AM

Jack:

 

As far as I know, the only Dobs you have used are mine and based on my experience, they are probably less wobbly than most.  I would just use it for a while, you get accustomed to it .  

 

Also, a two speed focuser is a real help.  Very often the process of focusing incites vibration and the two speed means you can use a light touch and avoid vibration.

 

My friend Jeff calls them Dobbles.. 

 

Jon

Jon, yes, the only dobs I’ve used are yours, I’m jealous. Want to trade? 12” for 12.5” sounds like a deal.

 (For me).

 

It's your choice for sure. But it makes more sense to me to use the fixes Ken suggests first. If your braces are not adequate they will have to be removed to do the other work, weakening their potential when reattached.

You are probably right, maybe I’ll do both at the same time.

 

Thanks, Jack



#16 Achernar

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Posted 05 July 2020 - 08:51 PM

Your problem with the object locator and the base are related, because a base that is not square is going to lead to the object locator becoming inaccurate. I would use the parts of the base as a pattern to build a plywood base to replace it, and you can insert gussets to greatly stiffen it. It would be worth the effort to also migrate to digital setting circles such as Sky Commanders or the newer and more capable Nexus system.

 

Taras


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#17 makeitso

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Posted 05 July 2020 - 09:08 PM

Thanks Achernar,

 

I’ve already got this to work. All I ended up doing is adjusting it properly. I just got this dob a week ago. Nothing was adjusted correctly on it.

 

Jack


Edited by makeitso, 05 July 2020 - 09:09 PM.


#18 Tom Stock

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Posted 05 July 2020 - 10:14 PM

Your azimuth encoder is slipping if it "never worked".

There are several threads on this.
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#19 makeitso

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Posted 05 July 2020 - 10:32 PM

I appreciate all the replies and help from all who participated. I have the encoders working fine now.

 

Next up is the shaky flaky mount, for another thread.

 

Thanks, Jack


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#20 Starman1

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Posted 06 July 2020 - 05:17 PM

Yes, buttresses.  I'd use wooden triangles instead of shelf brackets, but I worked on these scopes for years and the bases are very wobbly.

All it takes is a comparison with a really stiff scope to see the difference.

So whatever you can do to buttress the scope's rocker box side panels will help.


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#21 Tom Stock

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Posted 06 July 2020 - 08:41 PM

Thanks Achernar,

 

I’ve already got this to work. All I ended up doing is adjusting it properly. I just got this dob a week ago. Nothing was adjusted correctly on it.

 

Jack

Excellent. Have you gotten to try it out yet after the fix?


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#22 makeitso

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Posted 06 July 2020 - 09:13 PM

I tried it out a few nights ago and worked perfect, always ended up with the target in the finder. I was using an es 11-82. Didn’t always get it in that but easy enough with the finder. Life has gotten in the way since though. I can’t wait to get this out to a dark site.

Jack




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