I've been on and off trying to do rudimentary astrophotography, primarily planetary observing, using my Celestron 4se, Svbony-305 camera, and Astroberry running on a Raspberry Pi. There are two primary observing suites(Planetarium/Photography) available on Astroberry, the HNSKY/CCDCiel suite and the KStars/Ekos suite. I had previously concentrated on CCDCiel/HNSKY, but now want to try KStars/Ekos.
Which leads me to this question:
CCDCiel offers the ability to immediately take previews of whatever the connected scope/camera is pointed to. Ekos doesn't seem to offer this. One must plan a sequence session and save it. I would like to ability to immediately see on screen what I'm pointing at. Does EKos offer this? Haven't been able to find it on the menus or manuals.
CCDCiel would not allow connection to a telescope that had not been manually aligned. I don't seem to see any similar restriction in Ekos, yet aligning the telescope would seem to be a prerequisite of the software knowing what it was looking at.. I think I must still manually align the scope before using Ekos. Right?
I never manually align my telescope--it isn't required.
I use the alignment module. That is, set a target and then go to align and click "Capture and Solve".
The system plate-solves the captured image, figures out where it is pointing from the plate solve,
then iteratively moves the mount/telescope to point to the target.
The system should be reasonably focused to do plate solving, and there is some setup for that -- you need to have the index files for plate solving installed, and there can be parameter tweaking needed for the plate solving to work well for your particular setup. I usually use the StellarSolver plate-solving option, but ASTAP can be simpler to get working and also works well.
So we come to the first hurdle. How does one do this? I am using the previewer but I don't know what are reasonable settings for this.
I point the scope at the sky, the sky is reasonably dark, but I can't capture anything that looks like the sky to focus on. In the attached screenshot you can see my settings and the preview that is not recognizably the sky. What should my settings be to make this initial preview so that I may focus the scope (must be a manual process, on my Celestron Nextstar 4se, no autofccusing available).
Also, I have no idea what the shadows, midtones, and hightights should be set to in the preview window. I don't understand what these controls are for.
perhaps it would be good to focus the scope during the day on a distant object to get at least the rough focus. During daytime you maybe have to reduce the exposure time to 0.01s or even less, and also play with the gain. Then dont touch the focus until night
After you get this rough focus you can point your scope at night to a bright star and play around with gain and exposure time. The problem may be, that your 4se has 1.4m focal length and therefor a quite small field of view (*). This brings some more difficulties. I think to start with an exposure time of 2-5s should be ok, then you have to play with gain until you see stars. The stars then maybe not in exact focus but near to it (since the stars are even more distant than your object during daytime).
(*) Perhaps one recommendation: use stellarium to look, what you can get into your field of view. In stellarium you can set your focal length and your camera parameters (pixel size and so on) and you will see, what area you can see.
Thanks for this excellent advice about daytime focus! I will try it at my next session.
But I haven't thought of using Stellarium in this way. I tried it and felt it wasn't that helpful. I've tended to prefer the cleaner look of HNSKY or KStars. Please explain a bit more the feature that you find useful in stellarium here.
Last edit: 2 months 6 days ago by Steve Cohen. Reason: Needed to respond to the stellarium suggestion.
You can enter the focal length of your telescope and the size of your camera sensor into stellarium and check, how "big" your field is, which you can see with your setup. At least for my stellarium (version 0.22.2) it is that way that you can click on the "wrench" in the upper right edge of the screen to go to the setup of "sensors" and "telescopes" and you can click on the circle with the rectangle in it (the third symbol from the right) on the upper right edge to get that red rectangel on the sky map.
A few pictures:look at the right upper edge with the symbols (you can also see an example for my sensor, and also the OAG but that is not important for you):
second picture shows the "telescope" list, my 8inch F% newton as example here:
And here the resulting sketch of the field of fiew for the setup (with info about pixel size and size of the FOV):
I have given daytime focusing a shot and still no joy. The scope is pointed at a mountain 2 or 3 miles away. It is clearly focused in the eyepiece. When I replace the eyepuece with the Svbony-305 I can see no detail whatsoever, focused or not. I can play with the Highlights/ Midtones/Shadows settings to darken or lighten the image but it's always a flat, undifferentiated rectangle, no detail visible. Similarly, playing with the Gain, Offset, etc.You can see the settings I used. Not sure what to try next. There are also some INDI camera settings I could play with. Grateful as always for any ideas.
Steve, if you are pointed at a mountain and you can see it in the eyepiece, what that tells you is you are pointed well. It doesn't tell you about the correct focus when attaching the camera. They will have different focus positions. So, now, given correct focus connect the camera and start hunting with your focuser taking pictures and seeing if you start to see any detail at all with some reasonable daytime exposure**. You should take relatively large steps until you find some picture with some detail, then search near there in a similar way with smaller steps, etc etc until you have a focused picture.
**In the daytime, you should likely be exposing well under a second. Perhaps .01? Not sure. Play with your exposure first and make sure you're not just getting all white over-exposures.
Of course, it is possible that your focuser doesn't allow the right amount of back-focus to put your camera sensor on the plane-of-focus. Usually there is some spec about what the backfocus of the telescope is and you can measure about where to place the camera sensor. E.g. many guide telescopes are like that, where the eyepiece attachment doesn't provide sufficient distance for a camera, and one needs to add an extension tube. However, I'd first assume that you're fine, and that you just need to hunt the full distance the focuser provides for an area that's in focus for your camera.
Steve, regarding Highlights, Midlights and Lowlights I would keep the Automatic Setting on (this is the button right from "highlights"). In the case in your picture everything is on "0", this leads to a white picture.
Regarding exposure time: I made sometimes the experience if the setting is too low I get no good results. Try 0.01s instead of 0.001s, but play with it, since it always depends on setup. Gain I would set for daytime photography to 0 or 1.
Regarding focus: Hy is right, that it might be, that it is not possible to get into focus with your camera with your current setup. Maybe you need some extensions. To check that it would be a possibility to point your telescope at the moon (or try it with the mountains, that should work too) and hold a white paper behind the scope. Remove the camera and eyepiece, so nothing should be in the focuser. Move the paper back and forth until you see a sharp picture on the paper. In that distance the camera sensor should be.
I would first check the exposure time / gain. If you get there a reasonable (maybe unfocused but good exposed picture) result you can then go on with the focus. You can watch the focus getting better or worth when moving the camera in or out and then you can see if you may need extensions or not.
In principle its easy but long to describe and for a beginner it is sometimes a little bit confusing