I have tried both options. First I mounted a 80mm WO refractor on top of the C9.25 and had a 127mm MAK side by side. Now I have the C9.25 on the left and a WO 110mm on the right with a WO 88 on top of it. All mounting by the way is using Losmandy side saddle gear - very solid stuff!
I think the side by side is a better option for my needs. My logic is:
1. It lowers the turning moment - that's three heavy scope I have on my mount - plus all the focusers, OAGs, lens, and camera's - lets make the mount's job as easy as possible
2. It places less stress on the SCT outer tube and there its front corrector plate - less distortion means less differential flexure which is a very good thing
I always think the more time and effort planning how all your gear will integrate and inter-operate before you purchase is a great investment of time. The mechanical construction of your observatory itself is a example of this - I really am in awe of what you have achieved!
A few things I would like to know:
1. What is the light pollution like where you will be observing?
2. Do you plan to do strictly narrowband imaging if its poor?
3. What imaging camera/s and/or filters do you plan to match to your OTAs?
4. Are you forward planning peltier or water cooled gear out of interest?
You have build a great observatory that will allow you to do many things over time.
PS
To Clive's post - you put the OAG on your scope with the longest focal length, ahead of the point where it focuses! My PHD guiding graphs can jump one or two bars vertically at a time - which may raise eyebrows until one realises that's still 0.8 of an arc second - so its most likely seeing. On a shorter focal length scope you aren't getting the guiding sensitivity that a long focal length SCT requires - in my opinion / experience!
I had a couple of illuminating conversations a month or so ago.
First one was to Andrews' coms. I was basically trying to sort the fact from fiction wrt the 16" GSO RC which is ostensibly in the pipeline. The price they were quoting was $4500. I asked about optical quality, they said 1/20th of a wave p-v. I responded something along the lines of; look, I would be satisfied if you could guarantee a good honest 1/4 wave.... I have the means to verify this interferometrically via a (professional) third party, would you be prepared to stand by the quality of this product?... all I'm asking for is a genuine 1/4 wave. Their response was jaw dropping... quote: Look, we would not be interested in selling this telescope to you on those terms, I suggest you call Bintel, they are the people you should deal with!
I was speechless.
Next conversation was to someone I have known personally for decades and has been in the business for almost as long. I wont say who, but I am sure a lot of you know him as well. He said that GSO (as of 6 weeks ago) had no intention whatsoever of producing a complete 16" RC OTA... period. And that was direct from the horses mouth. He went on to say that A coms sell 'grey imports' that are not backed by a factory warrantee. Which explains a bit.
Anyway.... keep that in mind when you go to buy your RC12.
You would think that the following statement would be so bleeding obvious as to be unnecessary; the place for the oag is ahead of the focal plane of the main instrument (not the piggyback scope)
It beggars belief that there is at least one RC12 gathering dust (that I know of) because the owner is obtuse and deaf to reason specifically on this point.
Sounds like you know all about it Clive. As usual you have all the facts correct. I take it your talking about my system here.
Just to put things straight here. I have been automating a wide field unit in anticipation of automating the RC12. ie a full robotic internet remote system. Not a trivial task. I did one image with a guide scope to test it. I am not nor did I ever intend to use a guide scope to image with that focal length. I am using a MOAG next to my STL11. When I produced the image of NGC253 I was still testing the scope. It is not gathering dust. Automation is difficult to achieve and requires a great deal of time to integrate all the systems thoroughly. In other words just for you Clive it takes many hours to get it working properly. I know the RC12 is good and can produce good images even with a guide scope (which has large amounts of flexure). The MOAG does not have that same problem.
Just for the sake of accuracy I have guide scope guided my CDK 17 with a reducer at 1761mm focal length (the reducer bars the use of anything but a self guiding camera for guiding due to the lack of back focus) with good success.
So it can be done and I could easily tweak from what I had with a much larger T-point model, a more refined polar aligment using the Sky X and a supermodel.
But yes its a bit fussy for routine imaging and MMOAG leaves it for dead of course.
As far as getting a guide star with a MMOAG is concerned I routinely image with one on my CDK17 at nearly 3 metres and Sbig STi guider (lovely unit) and I usually have no trouble. It has happened a few times I had to reframe the image to find a guide star but usually the object was still not far from centre and plenty of chip real estate left to capture it.
If you setup a MMOAG on the main scope you also use that to guide the refractor when you use it. You simply leave the guide camera on the MMOAG and plug off the end opening where the CCD cam goes on the MMOAG and put your imaging camera on the refractor.
With a 300mm RC you will probably want to use Tpoint to get the required accuracy of polar alignment and a well done PEC curve to settle it down even more. Drift alignment takes you a long way but there is still some accuracy left behind that t-point can detect and refine the polar alignment even more.
Also I agree with getting the carbon fibre version. I think expansion becomes more critical with longer focal length scopes and especially RCs which are sensitive to the spacing between mirrors.
I prefer Carbon Fibre - the alternate to me would be a really, really good - temperature compensating focuser. However I'd rather simply avoid the issue. It's amazing how well CF holds focus with temperature variances.
Baz, just some inside experience of the RC12 from GSO.
Focusor, through that away. It is ok but cannot haul a decent load up hill. Start looking at focusors with 6-9kg capacity and those that allow automated focusing (you will want to use this later so think ahead now). Some starting points are Moonlite focusors, Feather Touch focusors and FLI Atlas. Each are progressively more expensive, but each are strong. Look at rack and pinion on the Feather Touch. I am not sure if Moonlite make a rack and pinion but take a look there too. Each focusor has to be 3" to protect the light path from the mirrors. You should not use a 2" on these scopes.
For OAG go with the MMOAG from Astrodon. Best OAG in the business and built like a tank. If you can get hold of an STL11000 camera then the MOAG is the going to work better than the MMOAG. If you want to use the stand alone OAG the MMOAG will work for you. It is pricey but worth the money. Good fittings and places that make adapters like Precise Parts will know exactly how to fit that together with other components.
The Loadstar is a good camera but also consider the ST-I from SBIG. It has its own shutter and that means a lot of if you plan on doing a lot of unattended imaging. Don't get me wrong the Loadstar has great credentials but just take a look around. Buy the best guide camera once. The SSAG works too but it was a temporary measure from my own experience. It served me well but in the end died and many months before that it was act up and not calibrate properly.
The scopes you have will be fine for wide field imaging on their own but I would just pick one and use that one on top of the mount. Work on the premise that you want about 3/4 weight capacity of the mount for total setup. With that you need to consider camera, focusors, OAG's and cabling. It starts to add up after a while and this will get you quickly close to the 3/4 weight capacity of the mount.
Personally if you consider that the gear you are going to buy is high end, then think of the RC12 as a temporary resident of the system, you may decide later to buy a bigger scope and or a more expensive scope altogether. Buying the expensive peripheral components means you don't have to upgrade again and that will save you money. Don't balk at the costs as reliability is precious in my opinion. Stuff breaking down late at night means lost time.
The RC12 is a good scope but you need to tame a few issues. Focusor is one and the other is dew protection of the secondary. These scopes dew up on the secondary, so consider putting in a dew strap by Kendrick. I found it works a treat and then keep the fans running all night on the primary. The metal tube is another but refocusing every half and hour keeps that under control.
Buy yourself a Tak collimation scope too. You will need it and it is a good tool investment for all future scopes. I found my RC came a little out of collimation in the primary and I needed to sort that out. The only way you can do that is by using a Tak collimation scope. You can use Ken Crawford's avi (on his site) which shows how to collimate the rear cell on a RC scope.
If you think of anything else you want to know by all means ask. I am more than happy to help with frank and correct knowledge from my own use, not some supposition posited. These scopes have good optics but you need to work a little to get them working well. Don't believe half the crap that you can read about the GSO RC scopes or the innuendo that appears on this site from certain individuals. Those people have their own agendum to get people to buy some other telescope design. Their comments constantly appear in the GSO RC threads and each time their comments deride the scope and yet I have never seen them actually say they have one or tested one or even imaged with one.
I'll never be able to afford any of this stuff. Way over my budget unless some Philanthropist decides to help me out.
Couple of things.. What's MOAG and MMOAG? What's the difference between off axis guiding and off axis guiding? Three inch focussers? I can only find 2 and a half max at Moonlight.
I'll never be able to afford any of this stuff. Way over my budget unless some Philanthropist decides to help me out.
Couple of things.. What's MOAG and MMOAG? What's the difference between off axis guiding and off axis guiding? Three inch focussers? I can only find 2 and a half max at Moonlight.
MOAG = Manual Off Axis Guider. MMOAG = Monster Manual Off Axis Guider.
The monster MOAG is bigger and designed for bigger sensors. I always think to the future now for purchases. Is this purchase going to be transferrable to another system of better quality? If yes then you are on the right path.
A 2.5" focusor would be ok, but not ideal for that scope. It would work fine with smaller sensors but would be too narrow for larger sensors. In that case you would need to go to a larger focusor.
Depending on budget, you might have to compromise on camera but your focusor and OAG guider are holding things up in the air. You need to have a beefy focusor with autofocus ability. You could use a QHY larger format camera and save some money there too.
Bottom line is if you scrimp on these components you will be buying problems for yourself.
It beggars belief that there is at least one RC12 gathering dust (that I know of) because the owner is obtuse and deaf to reason specifically on this point.
Without a doubt you want the SBIG model with the built in off axis guider. I think its the STF (not sure of the model names).
If you don't have either self guiding, self guiding in the filter wheel or an off axis guider you are asking for trouble big time and will end up throwing the scope into the scrap heap it will be that annoying!
Guide scopes at that imaging focal length are going to be very tricky and an ED80 whilst a lovely APO scope has a weak, semi loose focuser which will not be up to the job.
I just installed an SBIG STi guider guide kit on my CDK17. I intend testing it first clear night to see if it will guide accurately at 3 metres focal length. it is very rigid even though its only a 100mm lens guide "scope".
I can let you know how it goes.
I have imaged semi successfully using a Vixen VMC 95 guide scope (over 1000mm focal length). I would sometimes get slightly eggy stars in some angles. With an offaxis guider I almost never do. And that was on a PME mount with PEC on.
Without a doubt you want the SBIG model with the built in off axis guider. I think its the STF (not sure of the model names).
If you don't have either self guiding, self guiding in the filter wheel or an off axis guider you are asking for trouble big time and will end up throwing the scope into the scrap heap it will be that annoying!
Guide scopes at that imaging focal length are going to be very tricky and an ED80 whilst a lovely APO scope has a weak, semi loose focuser which will not be up to the job.
I just installed an SBIG STi guider guide kit on my CDK17. I intend testing it first clear night to see if it will guide accurately at 3 metres focal length. it is very rigid even though its only a 100mm lens guide "scope".
I can let you know how it goes.
I have imaged semi successfully using a Vixen VMC 95 guide scope (over 1000mm focal length). I would sometimes get slightly eggy stars in some angles. With an offaxis guider I almost never do. And that was on a PME mount with PEC on.
Greg.
Thanks Greg. I take it with self guiding you don't need the separate guide-camera like a Lodestar or something because there's a chip in the main camera that does the job?
What about the MOAG or MMOAG? Do you still need that? I wouldn't think so if the camera is self-guiding.... Trying to make sense of it having never seen one set up and had a play with it.
I just sent an email away to Peter looking for a total package to go on the back of the RC300. Let's see where that goes.
Hey you guys I much appreciate all this. Once it all comes together I am sure I will be far better armed to pull the trigger because of all of your advice/experience.
You might be getting yourself into a whole world of pain if you're trying to use a very long focal length scope with an 8300 chip. The pixels are very small, so your arcsec/pixel will be very small as a consequence. You could bin it at 2x2, but there are problems with the 8300 chip when binning.
I understand budget is a significant factor for yourself. Why are you after a 12inch RC?? Aperture fever??? What sort of imaging do you want to do?? I've heard you mention community outreach stuff quite a lot - would you do better with a large newtonian for a brighter image through the eyepiece??
I've recently gone through the mental exercise of planning a school observatory (not sure if it will get the go-ahead or not) - and after getting all excited about putting in a large OTA, I realised most of the objects they'd be interested in would be more than adequately imaged by a 4 inch refractor. Much lower costs and much less headaches when it comes to guiding & focusing.
I'm not trying to be rude, but you don't seem to be abreast of the issues with heavy-duty deep sky imaging (based on some of your questions). Are you trying to bite off more than you can chew by buying a 12 inch RC??? Would you do better using your existing 120mm refractor and learning how to do monochrome imaging first, before taking the leap to a longer focal length?? All of the expensive upgrades that people are suggesting are correct - you'll have a lot of headaches if you try to cut costs.
You might be getting yourself into a whole world of pain if you're trying to use a very long focal length scope with an 8300 chip. The pixels are very small, so your arcsec/pixel will be very small as a consequence. You could bin it at 2x2, but there are problems with the 8300 chip when binning.
I understand budget is a significant factor for yourself. Why are you after a 12inch RC?? Aperture fever??? What sort of imaging do you want to do?? I've heard you mention community outreach stuff quite a lot - would you do better with a large newtonian for a brighter image through the eyepiece??
I've recently gone through the mental exercise of planning a school observatory (not sure if it will get the go-ahead or not) - and after getting all excited about putting in a large OTA, I realised most of the objects they'd be interested in would be more than adequately imaged by a 4 inch refractor. Much lower costs and much less headaches when it comes to guiding & focusing.
I'm not trying to be rude, but you don't seem to be abreast of the issues with heavy-duty deep sky imaging (based on some of your questions). Are you trying to bite off more than you can chew by buying a 12 inch RC??? Would you do better using your existing 120mm refractor and learning how to do monochrome imaging first, before taking the leap to a longer focal length?? All of the expensive upgrades that people are suggesting are correct - you'll have a lot of headaches if you try to cut costs.
Happy to chat to you by PM if you prefer.
DT
No that's fine David, happy to air it out here mate.
I intend to keep the smaller refractors I have along with a range of cheap scopes I already have to pop out on the lawn for community outreach viewing nights.
I used to own a 12 inch SCT which was way ahead of me at the time, but having images widefield for a bit I must confess I desire to go deeper. I've imaged a few distant galaxies with the Starshoot on the 120mm but I have to crop the heck out of them to fill the frame at the end of the day.
I may have bitten off more than I can chew, but I like to buy things I can grow into.
If the 8300 chip is too large for the RC300, then perhaps you guys can educate me on the optimal camera for the job.
I eventually want to get into narrowband imaging down the track and I don't want to have to keep buying more and more equipment. I'd rather get the lot in one hit then go to work on the steep learning curve. I understand it will be frustrating, but you can probably guess from my past and present projects that I have a great deal of patience.
So please, if you guys have suggestions for a total package to go on the RC300 and EQ8 I would love to hear what, why, how much and how.
Budget is a factor for now but it may not be that way for long...
I take it your talking about my system here.
