Location: Tucson, before that Wisconsin, before...
Posts: 231
good luck, please post back when you resolve that issue, it's good to hear what the culprit(s) was(were).
BTW, from the Yahoo group's correspondence, I think Gary K has a string in his neck that he pulls in response to 99% of the queries by new customers: "check that there is no encoder bearing slippage, then perform a daytime encoder test" That resolves about 90% of first-time troubles, and I speak from painful experience.
...I never did like reading the instructions...seems...un-manly, somehow....harrumph
good luck, please post back when you resolve that issue, it's good to hear what the culprit(s) was(were).
BTW, from the Yahoo group's correspondence, I think Gary K has a string in his neck that he pulls in response to 99% of the queries by new customers: "check that there is no encoder bearing slippage, then perform a daytime encoder test" That resolves about 90% of first-time troubles, and I speak from painful experience.
...I never did like reading the instructions...seems...un-manly, somehow....harrumph
s
I don't have any problem reading instructions for this kind of thing although I might miss 'a detail or two' until a second or third read.
Things I have determined
It seems my rocker box verticals are not flexed; i.e. measuring them at the bottom where they fix to the az board gives me 700mm and measuring at the top gives about 700.5mm. They don't seem to flex when the OTA is moved up and down, but I haven't tried your laser test yet.
There is some slack in the az bearing (bolt). Perhaps a shim or something wrapped around the bolt to act as a kind of collar would help here?
Cloudy skies last night, so I tried an 'indoor/poor-mans encoder test': I clamped a laser to the rocker sideboard and noted the point where the laser hit. I rotated 10000 increments and the point was spot on, as far as my eye could tell. Didn't try anything with the alt encoder. I'm still going with the assumption encoders are a-ok until I can do a proper daytime test. (This test was probably 100% useless, but I was bored... ).
Things I will try next clear night
Use Auto Adjust
Leave off diffraction modelling
Put my dob on a solid surface rather that soft ground as I do now
Other things to do Daytime encoder test
Improve (reduce) my stiction and general smoothness of motion
Try TPAS
Try out Gary's solution
Shoot the possum that keeps scaring the **** out of me in the dark
Anyway, enough surmising until I can try under clear skies.
Shoot the possum that keeps scaring the **** out of me in the dark.
Scaring me whilst astronomising is only the half of it. The other night one got in to the engine bay of my wife's car and shredded the soundproofing to make a nest. The next night it got in through my partly down car window and pissed on the back carpet. That carpet is now dead and gone, as will the possum be shortly.
Problem is, as soon as you 'move one on' another comes in to take it's place. Hopefully the next one will be more placid. If not, the world will run out of possums one day!
Aren't they a nuisance! Whenever I set up in the back yard they charge along the top of the wooden fence and make a hell of an unexpected noise.
Yes exactly Eric, along the top of the fence making lots of scrabbling noises. The only thing scarier is the sudden flight of a bird from a nearby tree
Location: Tucson, before that Wisconsin, before...
Posts: 231
I love possums...they taste great.
Our North American possums are ugly as hell but almost never approach humans or their possessions. Yours are cute, but darned nuisances. My wife wanted to sneak one of them out when we left....I think most of you probably would be happy to part with one or a billion or so.
Re the az play, I never could track down a bushing thin enough to insert between the bolt and base hole...but I'm sure there's a fix to be found. Gary K might be able to offer guidance on what magnitude, and type of pointing issue this could introduce, I dunno. Were I to fix it, I might either swap out the entire groundboard for high-end plywood (that chipboard will wear away and absorb moisture over the years), or bolt a drilled metal plate to the center to take the wear of the bolt.
good luck and good finding. I loved the Argo down there, it helped me find tons of stuff I didn't have the time (a year only) to spend learning to find.
Drop me an email at sales@wildcard-innovations.com.au and we are looking
at a solution whereby we supply you with smooth shanked locating pins
to allow the tangent arm to float.
Hi Programmer,
As promised, we shipped to you today an alternate set of Az and Alt tangent arm
brackets along with associated screws, washers and sleeves which allow the
tangent arms to 'float' with respect the mount.
With regards the OTA shifting from side to side with respect the rocker, another
suggestion is to obtain some self-adhesive felt padding such as used on the feet
of furniture to prevent it scratching floors. You can find a selection of material
at any good hardware store. Affix the pads on the inside sides of the rocker beneath
the Alt bearings.
Thanks also to Scott Tannehill for the various suggestions on getting the
mount ship-shape. Any slop, play, shifting or skewing you can address
will pay off in pointing performance. TPAS can help compensate for some
systematic geometric fabrication errors within the mount/OTA but no system
can ever compensate for a random error.
For the daytime encoder test, if you can position the scope somewhere
on the driveway in the street, something like the insulator on a distant
power pole makes a good target.
Once you have established the encoder direction sense signs, use AUTO ADJUST
ON, which can refine your estimate of the Altitude encoder reference point after
you perform a two-star alignment.
There is some slack in the az bearing (bolt). Perhaps a shim or something wrapped around the bolt to act as a kind of collar would help here?
Hi Programmer,
As Scott mentioned, in mechanical circles, such a 'collar' is referred to as a 'bush'.
Typically they are manufactured in materials such as bronze. Some come with
a flange.
The Az pivot bolt is 1/2" in diameter. You can find bronze bushes with 1/2" I.D.
that then come in various O.D. and lengths. For example, you might use one with
an O.D. of 3/4" and then the appropriate length to feed through the base of the
rocker. Drop me a line at sales@wildcard-innovations.com.au for a lead
on a supplier in Sydney where you might find something suitable.
If you have a power drill, you then might consider borrowing or investing in
a hole saw with appropriate O.D. A jig for the drill so that you can cut the hole
exactly at right angles to the inside surface the of the rocker is highly recommend.
You also want to take care in centering the hole as best you can.
Adding a bush to the Az bearing will not only reduce chipping, wear and tear
and reduce wobble, the movement of the Az bearing can also be made to be
considerably smoother.
Thanks Gary. After some initial frustration tonight with the alt encoder binding again (ever heard a grown man cry?), I soon settled down to some REAL frustration. Anyway, LONG story short, I changed the az encoder direction sense and all was ok again. Again, all tests seemed to indicate I had determined the direction senses correctly, but pointing was WAY out (i.e. completely wrong part of sky). On a hunch I changed the Az direction sense and started getting some sort of reasonable pointing. I guess that means the direction senses are right? I might add I went back to factory defaults at the start of the session. I'll get back out there soon and experiment some more.
Will consider modifying the base, adding a bush, etc. And will definitely get around to doing that daytime encoder test.
Location: Tucson, before that Wisconsin, before...
Posts: 231
Hey Programmer,
Ironically, I lived about 3 km from you last year, in Sandringham. We have probably trod upon much of the same real estate there...
Is your Alt arm screwed to the sideboard now? I just floated it, letting gravity hold it down (thus, it's best as close to 90 degrees as you can secure it to thereby allow it's weight to hold it down...if it's straight down gravity won't really help!
s
Quote:
Originally Posted by programmer
Thanks Gary. After some initial frustration tonight with the alt encoder binding again (ever heard a grown man cry?), I soon settled down to some REAL frustration. Anyway, LONG story short, I changed the az encoder direction sense and all was ok again. Again, all tests seemed to indicate I had determined the direction senses correctly, but pointing was WAY out (i.e. completely wrong part of sky). On a hunch I changed the Az direction sense and started getting some sort of reasonable pointing. I guess that means the direction senses are right? I might add I went back to factory defaults at the start of the session. I'll get back out there soon and experiment some more.
Will consider modifying the base, adding a bush, etc. And will definitely get around to doing that daytime encoder test.
Ironically, I lived about 3 km from you last year, in Sandringham. We have probably trod upon much of the same real estate there...
Is your Alt arm screwed to the sideboard now? I just floated it, letting gravity hold it down (thus, it's best as close to 90 degrees as you can secure it to thereby allow it's weight to hold it down...if it's straight down gravity won't really help!
s
Just came in from a quick tour around some brighter objects (crappest night ever, both seeing and full Moon) so open clusters were the go. Couldn't see much better than mag 5. Naked eye there must be 10 stars in the whole sky. Anyway, after an alignment on a near-zenith star and Jupiter I actually got all targets (albeit large ones) within my 17mm EP. More tweaks and experience and I'll be having a ball! Thanks to all for their fantastic help thus far.
Scott, yes the Alt arm is screwed in, and all seems well, but I think Gary's 'floating' arm idea will be great.
And Scott, I was born in Sandringham, so chances are very good indeed we have trod the same ground. Lovely real estate it is too
Hi Programmer,
Just wondering if you've sorted this out as I'm considering the AN for my 12" GSO Dob.
Are you happy with the encoder mounting etc now?
Any chance of a couple of photo's?
If you heavily epoxy the bushing to ONLY the ground board you can reduce the amount of wobble on the az axis. There are other ways of doing the central bearing to ensure that the wood is not used as a bearing surface. I have made a few and used some commercial models over the years. I have also always used a slotted tangent arm to avoid loading the encoder shaft. There have been many mounts which have benefited from four small pads of teflon in between the edge of the altitude bearing and the side board. Also reinforcing the sideboards and front board to the base board with shelf brackets reduces flexure.
Hi Programmer,
Just wondering if you've sorted this out as I'm considering the AN for my 12" GSO Dob.
Are you happy with the encoder mounting etc now?
Any chance of a couple of photo's?
Cheers,
Jason.
I'm definitely happy with my Argo experiences to date. Due to weather and other circumstances I haven't been able to use and tweak it as much as I'd like. As you've probably seen, support from Gary has been exemplary, and I'd have no trouble recommending the system to anyone. I'll see what I can do about some photos.
If you heavily epoxy the bushing to ONLY the ground board you can reduce the amount of wobble on the az axis. There are other ways of doing the central bearing to ensure that the wood is not used as a bearing surface. I have made a few and used some commercial models over the years. I have also always used a slotted tangent arm to avoid loading the encoder shaft. There have been many mounts which have benefited from four small pads of teflon in between the edge of the altitude bearing and the side board. Also reinforcing the sideboards and front board to the base board with shelf brackets reduces flexure.
Interesting Roger, thanks for the tips. The teflon idea is interesting.. As is the epoxy.
I'm definitely happy with my Argo experiences to date. Due to weather and other circumstances I haven't been able to use and tweak it as much as I'd like. As you've probably seen, support from Gary has been exemplary, and I'd have no trouble recommending the system to anyone.
I know this thread has nothing to do with me, but as I have been reading the progress of Programmer's installation, I too agree that the level of thoroughness and attention to detail and customer satisfaction awareness of Gary Kopff is beyond outstanding!
It is great to see a company so interested in making sure their product is the best it can be and takes such a keen interest in the issues that may arise.
I have been searching around for Goto and DSC options for my scope and any future scopes I might buy and from what I have seen here and elsewhere as well as the product itself, the Argo Navis is definitely on top of the shopping list for a DSC / Pushto solution.
Great to see Gary. My compliments to you and your company.
I know this thread has nothing to do with me, but as I have been reading the progress of Programmer's installation, I too agree that the level of thoroughness and attention to detail and customer satisfaction awareness of Gary Kopff is beyond outstanding!
It is great to see a company so interested in making sure their product is the best it can be and takes such a keen interest in the issues that may arise.
I have been searching around for Goto and DSC options for my scope and any future scopes I might buy and from what I have seen here and elsewhere as well as the product itself, the Argo Navis is definitely on top of the shopping list for a DSC / Pushto solution.
Great to see Gary. My compliments to you and your company.
Cheers
Chris
Thanks Chris,
We appreciate your kind comments and would love to see you join our extended
family of Argo Navis owners at some point in the future.
How to minimize flex and OTA shift in your GSO Dob
Hi Programmer,
The following suggestion, forwarded to me by John Bambury, may be of interest.
An outfit in Michigan USA, DBA Astronomy Products LLC, which apparently no
longer trades under that name, use to offer alternative 'deluxe bases' for
the GSO Dob mounts. See attached photograph of one fabricated in birch.
However, as John points out, there are some ideas you and other GSO mount
owners might like to borrow and the same principles apply irrespective of
the construction material.
By the addition of some bracing, one can then stop any sideways flex in the
sides of the rocker. John reports that he successfully applied the same
modifications to his own GSO Dob by simply fabricating his own braces
and retrofitting them to the existing chipboard mount.
As John reports -
Quote:
You see the brace running from the base up the side of the rocker box to almost the top, just forward of the altitude trunnion? That is what one needs to fit to the GSO base. It's about a 30 minute to one hour job for someone with a saw, a sheet of 12mm chipboard or MDF and a can of black paint, so it looks professional. It is fitted with countersunk screws (long ones because it''s going sideways in to chipboard) from inside the rocker box and underneath the baseboard of the rocker box.
Once the brace is installed which stops all sideways flexure of the rocker box itself, you then "shim" the insides of the rocker box with virgin Teflon pads (felt is a "fair" alternative) to stop any sideways movement of the scope itself within the rocker box.
With less flex, this pays dividends with your pointing performance when the mount is
fitted with optical encoders. Plus you get the benefit of a more rigid mount.
Many thanks to John for forwarding this suggestion.
although I might miss 'a detail or two' until a second or third read.
).
Aren't they a nuisance! Whenever I set up in the back yard they charge along the top of the wooden fence and make a hell of an unexpected noise. 
I actually got all targets (albeit large ones) within my 17mm EP. More tweaks and experience and I'll be having a ball! Thanks to all for their fantastic help thus far.
How to minimize flex and OTA shift in your GSO Dob
