RayD

Rodd just to confirm, can you focus the main camera with the filter wheel and spacer on i.e. does your OTA have enough inward focus travel?

I think you accidentally stuck this in the wrong thread Rodd: Here is my setup--please keep in mind that I did try a spacer between the OAG and filter wheel--despite my supplier insisting it was not correct. It did not solve my problem. If you are wondering why the Loadstar is off to the side, its because without a spacer, it can't be rotated to be vertical because the shoulder of the lodestar receptacle impinges on the edge of the filter wheel. This is as far as I can rotate it--Maybe it does not matter where the prism enters the light cone--but I am used to imaging sensors and guide sensors to be oriented the same way (self guiding filter wheel. This definitely won't work, and no matter what your supplier has said, you definitely need spacers between the OAG and filter wheel as your camera only has 6.5mm of back focus, which means from the sensor to the prism in your filter wheel is only about 17mm (give or take), which means your guide sensor can never be far enough away. With all this noted, the one thing we can't confirm is whether you have enough inward focus travel on your actual OTA focuser to reach focus with this short a back focus, but that's another issue.

Where did you fit the spacers Rodd? For it to work they would definitely need to go between the OAG and the FW, not in front of the OAG as you would normally expect.

Yes I've seen those, that's what I wondered if they supplied with the OAG? It's definitely going to be a squeeze I think.

Good job, looks neat. I think Rodd would need to have measure up with the Lodestar as they are C mount with no T2 option. It's 12.5mm from the end of the well, so anything added is simply added. I had the same issue using mine on my SX and Atik OAG's. The only possible help is if the turret is very thin, like on the SX, and it then slides up inside the camera chamber right up to the lens window, which can resolve the issue. I'm not sure his supplier has given him the right spacers. I did ask earlier whether there are spacers for between the OAG and FW but he doesn't seem to think so. I can't see how it can work any other way due to the short 6.5mm back focus on the ASI 1600. Your image is a great visual representation now as the CN post I linked to earlier seemed to indicate that the only reason the guy installed the internal spacer was to align the sensors, but that didn't make sense.

Nice work well done. This confirms what I said earlier, which is spacers are needed between the OAG and the FW otherwise it can never work. Does the OAG come with a shallow profile T2 to C mount adaptor as the Lodestar is C mount, not T2 like the ASI?

Just by coincidence, this was just posted on another thread. https://stargazerslounge.com/topic/311042-guidescope-mount/?do=findComment&comment=3404750

Ok I see. For me personally, if you are imaging with your C11, I would use OAG for sure. As noted above, it isn't impossible to image/guide without one, but to coin a phrase, "it ain't 'arf hard".

Oh crikey a guide scope is definitely easier. I don't think anyone would suggest going with OAG unless you need to. The only reason I have them is because it all worked out easy, but they can be a mare to get right if you are mixing and matching. The main benefit of a OAG is to remove flexure, and this is accentuated at longer focal lengths. At your focal lengths, providing you have a good secure fixing, then this should not be an issue.

I would think something like that would be ideal. My 60mm is 225 fl and it works great. Never had an issue with getting stars and the Lodestar focuses with no issues. It is possible that you could need a short extension, but it would only be a standard eyepiece type one. If you image at a longer fl then you can just look at a bigger guide scope. As is the case with @LightBucket, the 80mm seems to be a good choice, but at your noted fl you probably wouldn't need to go that big, particularly with the X2.

As long as you can stick around the 1:5 ratio, and the aperture is big enough to get a star (shouldn't be an issue with the X2 as it is very sensitive) then there are a lot of options out there. What about the new Skywatcher Evoguide (50mm). Veeeery nice.

Oh yes it can definitely be done; that's why I refer to things as a guide. You just need to have a really good mounting and be brave enough to try it. I'm sure most imagers would recommend OAG at this type of fl, me included, but that's not to say it is essential by any means.

Not at 1000mm focal length, no. I would have thought a good bet for you would be something like an ST80, or something else 60mm +? I have 2 of the Altair 60mm guide scopes and they have been great, but I know a lot of people use the ST80 with great success at longer focal lengths. There's some info here which is a bit of a guide, but I think you could do a lot worse than looking at a 60 to 80mm scope.

I think a rough guide is targeting a ratio of 1:5 or lower (I think some say 4 and some 6, so in between these is probably nearer to reality). Obviously with OAG you could technically be 1:1. Many will guide successfully higher, but I think if you can achieve around this then it will be pretty good. I have heard another thing mentioned of the fl of the guide scope being 1/3 of the main scope, but I'm not sure how accurate that would be as the pixel size of the camera would have an effect. I don't think it needs to be exact, and of course the biggest thing to get right is eliminating flexure. I image with my Esprit at about 2.5 "/p and guide at 7.5 "/p and this works great being a ratio of 1:2.5. This is with a 225mm fl (Altair 60mm) guide scope and Lodestar X2. I'm sure there are others with more expert experience of guiding who could advise in more detail, but I can't emphasise eliminating flexure enough.

No it is about making sure your pixel scales match, so your guide scope just needs to match your camera and your main imaging scale. Use this tool to see what will work best for you.

Absolutely. There are many expert imagers, including @ollypenrice who image superbly at longer focal lengths without OAG. I certainly can't see 1000mm being a huge issue. I would think it is only when you get to pretty long focal lengths (1300 - 1500mm+) that you really need to look at the possibility of going down the OAG route. You have one of the best guide cameras out there, so coupled to a decent FL scope this should work great.

Ah, sorry I can't be of any more help Rodd. It just seems the spacing isn't going to let you get the guide camera close enough. I use a guide scope on my Esprit 100 for this exact reason, as the space needed for the SW FF (55mm) means I can't fit a OAG in with my 16200. I use OAG on the FSQ 106 as I don't use a FR so the spacing isn't an issue. OAG's eh, who'd have 'em!!!!

This thread may also help Rodd, it has some critical dimensions to help work out how much spacing will be needed.

Hmmmm. What spacers/adaptors has he given you? I wonder if he has planned for it to be fitted as the CN thread, as I can't see how it can work with this combination otherwise as the 12.5mm needed by the Lodestar just makes things all very challenging.

Ok there's a thread on CN here which may help. The GPCAM 2 has the same 12.5mm back focus and is the same dimensions as the Lodestar, so this my well be applicable to you, in that you will probably need to add spacers between the OAG and the camera, otherwise you won't be able to get the OAG camera sensor in enough. Otherwise I think you are looking at the 120MM as a guide camera.

Give me half hour and I'll try to find out some dimensions from factory drawings and should be able to tell you whether it will be possible to get it to work. Do you know the type of FF you have, or better still what the recommended spacing is for your FR?

That's a good thread actually as it shows how close the guide camera needs to be to the OAG. It may work but I think you need to measure or work out how far the ASI sensor is from the centre of the prism, and see if you can get the Lodestar sensor exactly the same distance away. I think it will hard, but if others have done it, then it must be doable. The Lodestar is C mount, and it looks like the ZWO OAG (I've not seen one in person but that's what it looks like on the images) is T2, which means you will need some sort of adaptor, and even then it will only be able to go down as far at the top plate of the OAG. The Lodestar sensor is then 12.5mm back from that point, so it should be pretty easy to work out with a set of vernier gauges to see if it will fit. I can't see your supplier giving you duff information, so it must be something we're missing or something wrong with the OAG/prism.

Well, I would say the ASI 120MM will definitely work, assuming there isn't an issue with the OAG of course, and I have/do use one and it works great. However, I didn't mean to ditch the FR completely, I meant just to see if you can get the Lodestar working in conjunction with the ASI 1600, then put it on. The problem as I see it with trying to set this up with the FR on, is that you need to get the distance from the FR to the ASI and the Lodestar spot on before you can start to focus. By ditching it for now, you can get the 2 aligned just by having both in focus, and then put you FR on and set the distance just to the ASI sensor as the Lodestar will just follow suit. If you have a ASI 120MM the first part may be easier, but if as you say others have used the Lodestar with the ASI 1600 and the ZWO OAG, then it must be achievable, but perhaps just needs a little more fettling and thinking? I really do hope you get it sorted Rodd as all that kit is great stuff, so once resolved I'm sure we'll see more of your great images taken with it.

I don't think you would need to do that, it's all good kit. I just think the Lodestar was designed to work primarily with SX cameras, which typically have 17.5mm back focus. The ZWO has 6.5mm, so there will be a bit of fiddling to do to get them to work together. This of course is even more difficult with a reducer as the focal point behind the reducer is fixed which it would not normally be on the FSQ 106 if using it without it. I would give it a go without the reducer as this will give you more leeway given that you have no fixed point other than when it is in focus and see how you get on with that. But to start you will need to work out a way to to get the Lodestar sensor as close as you can to the prism, as the camera sensor is pretty close, and the pair need to match.

No problem at all, my statement wasn't meant to be antagonistic, just stating that however unlikely, once all the obvious has been eliminated, what is left must be the answer. Great if the Lodestar works with the ZWO kit as it is a great camera, I use 2 of them myself. I just wouldn't surprise me if it needed a bit of encouragement to work. I'm out of ideas I'm afraid as I have to admit, getting the OAG's I use actually working (I have 3 of them) I found pretty easy. Getting them to perform well at what they do is another thing entirely of course Hope you get it sorted though as it must be more than a little frustrating, but certainly don't think that because it's new it can't be broke. Especially if it has had a journey from China to endure.