Bargain Second-Hand Big Dishes For Sale

moonbase

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He needs to increase the range of the declination angle to match the offset of the dish.


Assuming a suitable frame can be fabricated of correct dimensions to accomodate the 1.8m CM dish, the increased declination could be introduced using some brackets similar to those pictured below.
These brackets could be attached to the top horizontal strut of the interface frame to provide additional declination.

Additionally, four small 90 degree brackets with a hole drilled in each face would be needed to facilitate use of the declination brackets. These 4 x 90 degree brackets could be easily made by cutting them from a lenth of angle iron.

I am not advocating modification of an IRTE polar mount as a "go for it" solution for the 1.8m channel master dish. The IRTE polar mount is unsuitable in my view and there are better options available, albeit more expensive.
However, it is possible to get a 1.8m channel master dish mounted on an IRTE polar mount but it does need some basic tools such as a hacksaw and a decent drill plus the aptitude to go for it.

.
Jaeger 1224 Offset Brackets.jpg
 

moonbase

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This would not help in this situation as you need to have an extended declination adjustment of 108mm.


Just a quick brain fart, does the top length of the IRTE polar mount have enough length to it to allow cutting/extending the declination adjustment slider hole?
I no longer have the IRTE polar mount to measure.
 

OverwatchX

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Just a quick brain fart, does the top length of the IRTE polar mount have enough length to it to allow cutting/extending the declination adjustment slider hole?
I no longer have the IRTE polar mount to measure.

Unfortunately no, I created a template for him to use to extend it easily though from a bit of steel 8-10mm thick, without the need for a wedge.

DSC_1715.JPG
 

OverwatchX

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moonbase

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This is how I adapted a Precision PM designed for prime focus to 1.8m Channel Master.


I remember that mod CJ, it was very nice.
Fortunately, you had a top class mount in the Precision triangular frame polar mount to start the job with.
 

moonbase

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Unfortunately no, I created a template for him to use to extend it easily though from a bit of steel 8-10mm thick, without the need for a wedge.

DSC_1715.JPG


Nice simple solution.
 

John

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moonbase

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.. Iv'e used 'Alternator brackets' in the past for similar ideas - various sizes and shapes.


They look like they were designed for the job of extending declination.
 

Channel Hopper

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Unfortunately no, I created a template for him to use to extend it easily though from a bit of steel 8-10mm thick, without the need for a wedge.

DSC_1715.JPG
From memory, (I'm going on the roof to check important dimensions as it is raining, again) the lower part of the bearing 'C' cage can be drilled with a hole further forward, with the bearing bolt inserted accordingly (perhaps with some metalwork shaved from the rectangular base corners to allow full arc movement), an offset closer to that of the Channel Master design should be possible.

No guarantee it is going to be fully compatible (and a 'V' wedge may still be required), but the reflector mass will be closer to the bearings and the quality of the IRTE polarmount will keep everything shipshape for near perpetuity.
 

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  • IRTE Polarmount 1.jpg
    IRTE Polarmount 1.jpg
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moonbase

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If the member asking about the polar mount for a CM 1.8m dish has potential options for another dish/mount I think they are better off going in that direction. From personal experience of modding an IRTE polar mount to accept another make of dish I would not repeat the procedure due to the moderate quality of the bearings and the lack of sensitivity on the actuator travel due to the proximity of the actuator end fixing point to the rotational axis.

Sure, it can be done, however out of choice I would swerve it and look for alternative options.
 
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moonbase

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2.4m Prime Focus dish on eBay, £40 starting bid or buy it now for £80.



Sold £46.89p, a bargain for someone looking for a C-Band dish, was it bought by a forum member, hands up !

Nicknamed "The Tin Dish" on the forum, the 2.4m Fortec Star performed reasonably well in C-Band based on observations from a few forum members, "aceb" and "s-band" spring to mind.
 

butchyboy

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guys where could i possibly get the whole polarmount 1.8m offset channel master dimensions where i could get one made up,any ideas or help please.
 

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From personal experience of modding an IRTE polar mount to accept another make of dish I would not repeat the procedure due to the moderate quality of the bearings and the lack of sensitivity on the actuator travel due to the proximity of the actuator end fixing point to the rotational axis.
The IRTE polar mount lends itself very easily to actuator modification, usually little more than drilling one or two holes with a minimum of calculation.

A child could do it.
 

moonbase

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The IRTE polar mount lends itself very easily to actuator modification, usually little more than drilling one or two holes with a minimum of calculation.

A child could do it.

It is not just a matter of drilling holes, the actuator end fixing bar needs to be replaced with a longer version.
In addition, there is still the issue of the moderate quality bearings on the IRTE polar mount.

Having modified one of these IRTE mounts for use with another make of dish I would not do it again.
In my personal opinion the IRTE polar mount fulfils a role in the market, it is at the bottom end.
 
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OverwatchX

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If the member asking about the polar mount for a CM 1.8m dish has potential options for another dish/mount I think they are better off going in that direction. From personal experience of modding an IRTE polar mount to accept another make of dish I would not repeat the procedure due to the moderate quality of the bearings and the lack of sensitivity on the actuator travel due to the proximity of the actuator end fixing point to the rotational axis.

Sure, it can be done, however out of choice I would swerve it and look for alternative options.
To increase sensitivity of the actuator he can extend the right angle bar. Only issue with this is more sensitivity = less travel. In my experience, the sensitivity isnt an issue, but the strain on the jack is. Less sensitivity = more strain on the actuator threads and motor.
 

OverwatchX

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Sold £46.89p, a bargain for someone looking for a C-Band dish, was it bought by a forum member, hands up !

Nicknamed "The Tin Dish" on the forum, the 2.4m Fortec Star performed reasonably well in C-Band based on observations from a few forum members, "aceb" and "s-band" spring to mind.
I was going to buy this and was seconds away from clicking to bid, when i realised its too far away to collect with lockdown rules. With my luck I would get fined £250 for a £40 dish!
 

Channel Hopper

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To increase sensitivity of the actuator he can extend the right angle bar. Only issue with this is more sensitivity = less travel. In my experience, the sensitivity isnt an issue, but the strain on the jack is. Less sensitivity = more strain on the actuator threads and motor.
The bar could be extended, but the design allows the existing item to be angled backwards with one additional hole drilled moving the actuator pivot further from the polar bearings.


The number of pulses per degree of rotation will increase slightly, lowering of strain on the actuator, as long as the length of the actuator is greater than the total travel east /west then it's win-win.
 
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moonbase

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I was going to buy this and was seconds away from clicking to bid, when i realised its too far away to collect with lockdown rules. With my luck I would get fined £250 for a £40 dish!


Shame, it would have been nice to see it feature in an install topic on the forum, particularly on C-Band.

I suppose you could ask the seller to contact you if the sale falls through with the winning bidder, sometimes winning bidders get buyers remorse. If the sale does fall through you could ask the seller if he will hold it for you until lockdown rules ease to allow travel?
 

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Sold £46.89p, a bargain for someone looking for a C-Band dish, was it bought by a forum member, hands up !

Nicknamed "The Tin Dish" on the forum, the 2.4m Fortec Star performed reasonably well in C-Band based on observations from a few forum members, "aceb" and "s-band" spring to mind.
That looks like my old one. I guess the seller is using the stand for his new dish.
 
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