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iOptron Mini Tower with Trapezium Wedge

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#1 Dr Benway

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Posted 11 June 2009 - 02:24 PM

It's been cloudy, raining and windy since I received the wedge from Steve. I checked the weather today and I MIGHT be able to find Polaris this evening! First light is on the schedule for tonight.

John Bozeman

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#2 Dr Benway

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Posted 11 June 2009 - 02:26 PM

Here is the view from the other side. This is one of the first lot of 20 made by ADM for Trapezium Telescope Services.

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#3 sam32

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Posted 11 June 2009 - 06:36 PM

John,

I have been considering getting the bearing upgrade and then the wedge. Have you tried the wedge on the MT tripod (the one in your picture appears t be a lot more sunstantial) and would that setup be okay for AP in your opinion ? I'd be using fairly light scopes in the weight range of 7-12 pounds. Also, is the wedge something that you just add and then its easy to switch back and forth between eq. and alt- az modes ? Or do you have to remove the wedge to go back to alt-az mode ?

Thanks,

Sam

#4 Dr Benway

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Posted 11 June 2009 - 07:54 PM

Hi Sam,

My MT has had the bearing upgrade. The tripod in the picture is the stock MT tripod. I shot a lot of AP with it in alt/az mode, and have been limited to 56 seconds due to field rotation. I bought the wedge to see if I could extend my exposures to around 2 minutes unguided. I use a C8 with Hyperstar3, so I am imaging at F/2.

The wedge is attached to the tripod with three M10 socket head screws. The MT head is attached with a single M12 socket head screw. It doesn't take very long to set it up or tear it down. You switch from Alt/Az to EQ with the handset. You have to remove the wedge to use it in alt/az mode.

John

#5 Sky Captain

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Posted 11 June 2009 - 08:29 PM

Thats nice looking John. Is there only one adjuster on the side for getting the right elevation\angle. Does it seem strong enough if thats the case.

#6 Luigi

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Posted 12 June 2009 - 06:21 AM

Yeah. The elevation adjustment looks a bit puny to me too.

#7 Dr Benway

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Posted 12 June 2009 - 07:55 AM

Its got plenty of beef to hold the rated load or more.

John

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#8 Dr Benway

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Posted 12 June 2009 - 07:56 AM

The other side

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#9 Chuii

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Posted 12 June 2009 - 07:57 PM

Hi John
I have a Minitower(MT) without bearing upgrade. For the visual use, does the MT with bearing upgrade perform better (without the wedge) than the stock MT?
Chuii

#10 Sky Captain

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Posted 12 June 2009 - 09:08 PM

Thanks for the close up shots John, it was hard to tell in the other photo's. Your right, they do look strong.

#11 Dr Benway

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Posted 13 June 2009 - 07:34 AM

I really can't see any improvement in visual observation. The mount is quieter. Target DSOs stay centered in the FOV for hours with or without the bearing upgrade. It's a different world doing alt/az astrophotography, however. I usually shoot a sequence of 20 exposures at 56 seconds duration. I would typically reject 50% of the frames prior to the upgrade. I noticed a sharp reduction in bad frames after the upgrade. I may throw out 3 frames in 20, worst case.

John Bozeman

#12 Luigi

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Posted 13 June 2009 - 08:03 AM

Yeah. That adjustable brace on the side opposite the adjustment screw looks like it adds what's needed for rigidity. I think it would have been better to design it with both positioned as far from the pivot as reasonable to increase the arm they work over.

#13 Chuii

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Posted 13 June 2009 - 01:32 PM

Hi John
Thank you for your comments.
Chuii

#14 Dr Benway

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Posted 19 June 2009 - 03:45 PM

I managed to get about three hours observing time on this mount earlier in the week. I had an Orion ST120 mounted and it did fine. I lined up Polaris as the PARK position, did a 3 star alignment and was off and running. It tracks very well. The sky is back to cloudy again, so I set my AP rig on the mount and took few pictures. Steve made me a Losmandy style CW shaft and it is in the picture with an 11# weight.

I just ran a fake 3 star alignment in the house, and it worked great. Didn't strain a bit.

John

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#15 Dr Benway

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Posted 19 June 2009 - 03:47 PM

Fully dressed with the hard plastic dew shield...

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#16 Figment

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Posted 19 June 2009 - 10:36 PM

It looks like the center of gravity is pretty far away from the center of the tripod. Are you noticing any stability issues?

#17 Luigi

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Posted 20 June 2009 - 08:09 AM

With it set to your low latitude, the short arm for the latitude adjustment screw looks even more precarious. It looks like the CG of the scope and mount is offset pretty far from the center of the tripod. How stable is it against toppling? On the positive side it looks like there's plenty of clearance to operate without a meridian flip of you wanted to.

So, is there an advantage of this over something like a CG5ASGT or HEQ5? It seems like taking a alt-az silk purse and turning into an equatorial sow's ear. :p

#18 Sky Captain

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Posted 20 June 2009 - 08:49 AM

:scared: CG that far over is a bit scary looking for sure.


BTW, nice CW shaft.

#19 hudson_yak

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Posted 20 June 2009 - 08:57 AM

Agreed, that does not look safe at all. The wedge should be tilted the other way so the mount is carried over the center of the tripod, more like a typical SCT fork-wedge setup.

Mike

#20 tim53

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Posted 20 June 2009 - 08:59 AM

If it were me, I'd make a tray for the bottom of the tripod and set a 25lb barbell weight on the south side of it, or attach a couple 10lb weights to the south two legs.

-Tim.

#21 Dr Benway

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Posted 20 June 2009 - 09:00 AM

It is very stable. The picture shows it in the park position. It does look like the CG is very exaggerated. Things look very different once you actually slew to an object. Meridian flip is not an issue with this set-up. Advantages over something else? None that I can think of. I also use a GM-8 with autoguider for longer exposures. I set this up as a quick grab and go for 2 minute unguided exposures, which suits the Hyperstar3 (F/2) just fine. As to the sow's ear, many people swear you can't run a mini tower in EQ mode.I built this rig to prove them wrong. I had been shooting in alt/az for several months with good results, but was limited to field rotation. My longest exposures were limited to 40-56 seconds, depending on what part of the sky I was targeting. This set-up solved that problem.

John

#22 Dr Benway

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Posted 20 June 2009 - 09:24 AM

Here is Steve Forbes' Mini Tower wedge setup with a C8...

John

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#23 EdTheEdge

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Posted 20 June 2009 - 10:30 AM

The more I see these mounts the more I want one!

#24 Renae Gage

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Posted 20 June 2009 - 09:54 PM

Pardon my ignorance, but what is the point of the wedge? I tend to doubt that the wedge will provide the alignment accuracy necessary for astrophotography, and visually, it throws off the eyepiece ergonomics.

#25 Luigi

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Posted 21 June 2009 - 12:07 PM

Does it have autoguiding inputs?






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