New Orion "thin" OAG
Posted 26 August 2013 - 07:20 AM
Posted 13 September 2013 - 06:11 PM
Looks like no one has taken the plunge yet. I'm surprised there has been no interested here as it's the first "thin" OAG easily available in the US. I'd love to grab one and review it here, but I'm so new to this I'm afraid that my observations, and comments would be a little merit.....
I'm hoping that with the proper adapters attached it will be no thicker than a standard T Ring thereby replacing the T ring with no spacing changes?
Posted 13 September 2013 - 06:47 PM
Posted 13 September 2013 - 07:39 PM
Posted 13 September 2013 - 08:14 PM
Posted 13 September 2013 - 08:29 PM
Posted 14 September 2013 - 11:19 PM
The manual says it has a c mount adapter too. Ordered.
Let us know what you think! I notice this OAG looks a lot like the Lacerta unit.
Posted 14 September 2013 - 11:27 PM
I picked up one from the local office. It comes with a Canon and T ring adapter for the sensor end. Overall thickness of the assembly is 13mm. They use a special ring with "ears" that's recessed past the mirror. This ring allows slight rotation of the assembly - maybe 45 degrees. The pick off mirror can be moved sideways a little bit, too. The recessed ring and the mirror can be secured by two thumb screws. This seems to reduce chance of flexure.
Up for more measurements?
I measured my T-ring from the outer edge of the canon EOS bayonet to the start of the threaded portion on the other side that accepts the T2 adapter nose piece.
I get 16.6mm
I'd love to know how the OAG measures in the same configuration.
Posted 15 September 2013 - 01:23 AM
Posted 15 September 2013 - 01:53 AM
I put the Canon adapter in place and measured it with my depth gauge and show 19.22 mm. This is measured from one side to the end of the flange bayonet. There might be a slight protrusion beyond the standard depth because of the thickness of the metal part. As best I can measure to the flange surface (the face of the bayonet) it shows 15.00 mm.
Hmmm, I kinda confused as to your 2 different measurements?
I just dropped my T-ring between the jaws of my digital calipers and got 16.6mm total thickness -end to end.
This is with the EOS bayonet on one side, and T2 female threads on the other.
Sounds like you got 19.22 mm making this measurement? That could be an issue if you current imaging train already had perfect back focus spacing using a T-ring! Then again thats just 2.5mm difference. Are all T-rings about the same thickness I wonder?
Anyone know the total thickness of the EOS version TOAG9, and the Lacente OAG?
Posted 15 September 2013 - 02:31 AM
Here are some images, hope these help to clarify. My wiggly hands trying to hold the gauge and my camera at the same time makes accuracy a bit of a challenge.
Pentax T ring:
OAG with T ring:
OAG with Canon ring:
OAG with the Canon ring at shoulder:
Posted 15 September 2013 - 03:02 AM
It is what I was thinking - 19.22
That Canon bayonet really seems to stick out from the main body compared to the T2 ring pic. That must be where the extra 2.5mm is coming from? Wish I had one in my hands, but alas, the Orion store is across the Country from me!
Just measured the thickness from the bayonet "Face" as you did and got 11mm! A 4mm difference from the Orion OAG. That should have also been a 2.5 difference so I don't know what that's all about
I think I need to just buy one......
Anyway, thank for those awesome pics. That was above and beyond!
Posted 15 September 2013 - 07:31 AM
Posted 15 September 2013 - 09:05 AM
Posted 16 September 2013 - 12:13 AM
On the camera side, there are no integral threads. Instead, there are two different adapters, one is a T thread and one is a Canon mount. The Canon mount is slightly longer than the T thread.
Hope this helps.
Posted 16 September 2013 - 08:23 AM
Posted 16 September 2013 - 09:21 AM
When installed, one end or the other will have threads, or a bayonet, which will be internal to the mating component and will therefore not add anything to the imaging chain length.
Posted 16 September 2013 - 10:58 AM
Posted 16 September 2013 - 06:51 PM
Yes, the M48 to T thread adapter on the telescope side of the OAG does add some thickness. It appears to be about 2.5mm. I don't have a lens spanner wrench, so I can't remove it to measure more directly. If you had a system that could use that thread size, then you'd be able to reduce the length accordingly.
So 2.5 on the Tele side, and another 2.5 on the camera side when using the EOS adapter gets us to the over 15mm mark.
That makes it quite a bit thicker than a standard T-ring. I would be connecting to a C8 Edge T adapter that gives the proper backfocus with a normal T-ring. I'm thinking this won't work.
I believe the TOAG9 comes closer to the proper size. Of course it's double the price, and reported to be less than robust. The Lacerta Is more robust, but I believe it suffers again from the extra thickness issue!
Posted 16 September 2013 - 09:17 PM
Posted 16 September 2013 - 11:01 PM
Posted 17 September 2013 - 08:18 AM
The instructions recommend checking initial focus during the daytime on a distant object. I must agree this is prudent suggestion as it makes it much easier to changes things, make adjustments, etc. However, there are a couple of errors or inaccuracies in the instructions. First there is a reference to Figure 10 and there is no Figure 10. I also think the instructions would be better with a diagram showing which Allen screws to loosen to adjust the prism and the focus of the autoguider. Second it is implied that distance from the main camera to the center of the TOAG and the distance from the camera to the center of the TOAG should be the same. However, if you work on this assumption you will not be able to obtain focus on the autoguider.
In order to obtain focus the distance between the main camera sensor to the center of the TOAG and the distance between the autoguider sensor and the center of the prism need to be about the same. For my Canon 60D DSLR this distance is around 49mm. To get the distance between the autoguider sensor and the prism to be around 49mm a spacer is required. I used the 5mm spacer from the Orion T-Thread Spacer Ring Kit, (which thankfully I already had). I then loosened the screws close to the autoguider platform to refine the focus by slightly pulling out (about 1mm) the autoguider, (with the main camera in focus). Then moved the prism down so the assembly rests on the TOAG body to lessen the chance of flexure of the prism stalk.
I also removed the step down ring and I am using a modified Hotech Self-Centering Camera T-Adapter for the nose piece. It screws right into the M48 threads.
Also the instructions don't mention it but you can screw on the SSAG until finger tight. Then back it off to align the long axis of the opening with the long axis of the sensor. You can then use the three Allen screws to tighten this down. Works with the Orion spacer too as there is a lip in the spacer.
As soon I get a chance to do some real star testing I will post more info.
Posted 17 September 2013 - 08:24 AM
Posted 17 September 2013 - 09:22 AM
Posted 17 September 2013 - 09:57 AM