Funny you should pose this question. I'm considering making one for my 17.5" dobbie. Won't be until the new year though. If you do go DIY, I'd be happy to push ideas & suggestions too. I've got a few other projects to clear before then too...
Jennifer, the Dob bearings are gravity, but the top plate of these platforms sit reasonably flat apart from some tilt while in normal operation, irrespective of observers lattitude.
Alex, happy to exchange some ideas, but I must admit I haven't researched it enough yet to offer much at this point in time. From what I have seen of commercial products from the US, it will be a LOT cheaper to DIY.
Pardon me being a bit thick, I thought the idea of an equatorial platform was to cant the base to make it point to the pole - which would be something like 34 degrees off horizontal in Adelaide.
Hi also have a google on split ring mounts. I am doing one for my 18". These can be quiet portable and easy to mod a dob to suit and if done properly will not add a lot of overall hight to the scope and can be adjustable for a range of latitudes. They are in a way similar to a platform and many profesional observatories use this type.eg (Anglo Australian siding springs)
Stellar cat drives will function very well with this type of mount.
Mark
I will be making these due to the success of my prototype, but I am redesigning it slightly to make adjustment easier and making it more streamline.
Obviously I will have the plans for the 12" factory immediately but hope to come up with a standard dimension when asked for things like location etc and centre of gravity of the scope.
One of the problems especially with a 12" is that finer adjustments require moving the mount a few degrees side to side and up and down. This is the major re-design of the mount and not aware of anything of it type seen. I am also considering a low cost Fork mount for smaller DOB as well. I have an idea but wont run it till I have completed the final EQ Platform design.
I am also look at a kit package making it cheaper for delivery as well.
Pardon me being a bit thick, I thought the idea of an equatorial platform was to cant the base to make it point to the pole - which would be something like 34 degrees off horizontal in Adelaide.
No, not at all. What does vary (and I'm writing from memory here, as I did look into them at one point) is the arc it travels - I'm not sure I'm explaining it right. You build them to suit a particular latitude and they don't take well to travelling north or south of the original specs all that well, although someone was making adjustable ones at one point, sort of +/- 5 degrees. Have a look around at some DYI plans and they should explain how it's worked out.
EQ platforms are made for particular locations but there is a small amount of variation available. Currently it is difficult to adjust but possible.
There is another somewhere that adjust in 10 deg increments about $1-1500.00 US. This method is extremely complex to make and not for the DIY'er and made from ally
I will be looking at a generic platform with interchangle radius. This will be after making base and platform templates first.
Matt from Telescope and Astronomy was looking at this some tima ago. I know he did have a prototype made but I am not sure how much further it got than that. Might be worthwhile to ring and ask him.
Making or buying an equatorial platform for an existing commercial dobsonian is not a viable project. Principally because the azimuth bearing needs to be on a flat surface to make it reasonably stable. It is not designed to be an "RA" shaft as it has no longitudinal or side thrust support.
However it is quite possible to make a support for an existing dobsinian OTA that can allow it to operate as an equatorial mounted telescope. Doing this commercially however would not be a commercially viable project because of the wide variation in the available OTA's and a suitable "box" would cost as much to produce as a standard equatorial head of the type that are available.
Barry, the Az bearing becomes the Dec axis, the EQ platform performs the RA function....
Quote:
Originally Posted by Barrykgerdes
Hi
Making or buying an equatorial platform for an existing commercial dobsonian is not a viable project. Principally because the azimuth bearing needs to be on a flat surface to make it reasonably stable. It is not designed to be an "RA" shaft as it has no longitudinal or side thrust support.
However it is quite possible to make a support for an existing dobsinian OTA that can allow it to operate as an equatorial mounted telescope. Doing this commercially however would not be a commercially viable project because of the wide variation in the available OTA's and a suitable "box" would cost as much to produce as a standard equatorial head of the type that are available.
Barry, the Az bearing becomes the Dec axis, the EQ platform performs the RA function....
Same problem, the Az bearing still has no support for side thrust (nor does the alt bearing). It all depends on whether you want a platform to mount a dobsonian on or build an equatorial mounted telescope out of dobsonian components.
I could build an equatorial base to mount a DOB OTA as I have a proper workshop with all the necessary facilities but it would still not be a trully practical project. In time and effort it would cost as much as Paramount.
A dobsonian mount is a great, cheap and simple method of mounting a telescope for practical viewing. But as a basis for an equatorial mounted telescope it is not practical. By the time you beef up the rotating axes you may as well have built or bought a proper mount.
I had a look at their "equatorial platforms". An interesting concept but they don't make the telescope into an equatorial mount. As far as I can make from the pictures they are a device to take care of field rotation on a alt/azm mount, will only be suitable for a particular location and will still need suitable drive and guiding facilities.
If you have a nice SDM or Obsession that has cost you a mint it is a practical way to use the scope for photography. But most people looking for ways to take photographs with their dobsonians are looking at the cheaper mass produced dobsonians.
As for being pessemistic about cost. Making a device from a kit or plans may be relatively cheap but designing and building from scratch is not. Try it sometime and record your time, materials, tools etc. I have designed and built many one off projects.
To give you some idea my present project is to get the Radio astronomy dish at Wiruna operational. I have had two weekends at Wiruna and need two more, travel and time at commercial rates about $2000 a trip. Work at home refurbishing parts 20 hrs at $150/hr. Investment in electronic equipment (S/H and new) and parts $3500. This effort is only a small part of the overall project. I wonder why the original project was put in the too hard box a few years ago?
Incidently you may have seen in the news the problems with the Navy's two special landing ships. I did the original investigation and quotation for the projected modifications to the communications system. We did not get the job (politics) but the firm that got the job wanted our drawings (free). Look at the mess they are in now.
I hope you didn't give them what they wanted!
Local Councils are like that - you do all the work or they won't pass the designs, then they want CAD drawings for their own use for the DA - I usually send PDF
I hope you didn't give them what they wanted!
Local Councils are like that - you do all the work or they won't pass the designs, then they want CAD drawings for their own use for the DA - I usually send PDF
I don't think they got them free. The big problem was that I had done similar projects on other ships (successfully) and quoted for the "known contingencies" that I knew would be present in getting the systems to work. This is what the lower quotes had no idea of or the expertise to fix. Same thing happenned with the Collins class submarines. Incidently I still have my copies of the quotes somewhere.
There is one thing I found out long ago and that was to give "people wanting your job" all the information and procedures I had. This invariably led to their disasters because there is know way I know of to publish "expertise" and you got the work anyway under your conditions.
I had a look at their "equatorial platforms". An interesting concept but they don't make the telescope into an equatorial mount. As far as I can make from the pictures they are a device to take care of field rotation on a alt/azm mount, will only be suitable for a particular location and will still need suitable drive and guiding facilities.
Barry
Trust me Barry. An equatorial platform IS an equatorial mount. It just happens to be one with limited RA travel. I'll explain it to you at tonight's astroimaging meeting.
Geoff
Very simply a EQ Platform works like a EQ1 mount. I have taken a nice photo of M42 with my DOB on the EQ platform so it works for me.
Not that difficult to make so a basic system shouldn't cost a fortune to make. The distinct advantage of a EQ platform to a generic DOB ALT/AZ mount is field rotation. No need to purchace any field de-rotator.
