vlaiv

Of course - smaller telescopes have their use and are much more portable. You can also do wide field with large telescope. It is more involved - but 8" F/5 Newtonian is (almost) as fast at wide field as is 100mm F/5 refractor. Trick is to do mosaics and to bin data to get the same resolution as smaller scope. You then need to spend only a fraction of time on each panel of mosaic and it adds up to same time (say 2x2 panels - each panel for 1/4 of the imaging time).

I don't think it is good for either - planetary or guiding. This is really overpriced web camera. I'm sure one can find web cam with similar specs for less money and make 1.25" nose piece adapter for it. Problem is that this camera is USB 2.0 yet can achieve 30fps at 1920x1080. How so? It uses compression like any other web camera. It does not support raw format. This will introduce compression artifacts in planetary images and also will skew precise star position and affect guiding. It is really "electronic eyepiece" type device - that you insert into scope and instead of using eyepiece - project image onto computer screen. That is it.

Contrary to popular belief - even for astrophotography, bigger is better. You will usually hear that for astrophotography, size does not matter and you can image everything with even modest 80mm scope. While that is true - more aperture means faster imaging time as speed of system is best defined as "aperture at resolution". Larger scopes simply have more aperture and hence for given resolution / sampling rate - they will be faster. Another point is that larger aperture telescopes can image at higher resolution than small telescopes. This is very pronounced in planetary imaging, but also holds true for long exposure deep sky imaging. In long exposure imaging aperture is not sole factor for resolution and things of course depend on mount used and sky conditions, but at smaller side of things, resolution does depend on aperture size (below 8" or so) significantly. Above is of course related to proper imaging telescopes. Using achromatic refractor adds quite a bit of twist to the whole story as chromatic aberration is kind of a blur and reduces resolution of telescope further.

So the focuser will also be sourced and not printed? I was thinking of doing such a small refractor myself, but good focuser units are really expensive. Best I could find was GSO single speed crayford unit that is meant for dob but can be adapted for refractor use (only drawback is rather short tube travel). I have access to rather cheap aluminum tubing - that is worth getting instead of 3D printing one.

Is it all going to be 3d printed? Where did you source the lens itself?

You can produce some good images with said scope - but it requires some skill and tricks to do it. I would not dismiss it straight away - you can use it to learn few tricks and get the hang of imaging and then move to something better. I took this image with my ST102: And this was with ASI185 - which is camera with much smaller sensor than yours (x3.5 times smaller).

I guess admins should be able to merge accounts or something to sort it all out for you

Two important things to note here: - use super pixel mode for debayering - that will make recording at actual 2"/px vs 1"/px - as is normal for OSC cameras. Color/OSC (short for "one shot color") cameras have something called bayer matrix of pixels instead of regular pixels. This means that each other pixel records different color - they are arranged in grid of 2x2 pixels and each grid element records - one red, one blue and two green color (each pixel has different filter applied to it). You probably heard of RGGB or similar being mentioned as bayer order - that just explains how pixels are arranged in 2x2 matrix. In any case - this means that there is only single red and blue pixel per group of 2x2 pixels and that actual resolution of color camera is less than of equivalent mono camera (where each pixel records the same information - depending on filter used for whole sensor). Super pixel mode acknowledges this and treats image accordingly. - you are using achromatic refractor and level of chromatic aberration will be severe in comparison to all other things in the image. I took following image with ST102 and 3.75um pixel size camera: Star bloat is evident and since you have smaller pixels - it will be even more severe. You can lessen it by using super pixel mode, but even then, best results will be if you really under sample. While above image has poor stars - if I presented it like this: Then it would not be as bad. That is about 4.5"/px - so if you use super pixel mode and then additionally bin x2 before processing - it will be more pleasing and less bloated. All of this also means that at 4"/px - you don't really have to worry that much about mount performance. If it guides at 2" RMS - you'll be fine. @Same old newbie alert What happened to your old account?

Thing is - those mass produced mounts have quite a bit of sample to sample variation so there is no telling what sort of mount you have. Positive side of things is that you can usually substantially improve mount performance by adjusting / tuning it. I've seen reports of EQ3 being 2" RMS down to sub 1" RMS. Just recently someone reported having second hand mount that works great. Maybe previous owner did adjusting / tuning of it? There is also a thread started recently on tuning EQ3 type mount by replacing some nylon washers with proper roller bearings for better performance. Look it up.

What do you want to know exactly? Tracking performance is best characterized by couple of parameters: - drift rate. - periodic P2P together with period. Two are connected, but periodic error is just in RA while both RA and DEC can have a drift rate. Drift rate due to polar alignment error is mainly constant and is only in DEC, while drift rate in RA changes and is mostly due to periodic error. Very rough calculation of drift rate in RA can be made by P2P * 2 / worm period. For actual peak and average drift rate - it is best to record periodic error and then analyze it in software like PecPrep Drift rate is expressed in arc second / second and helps determine max exposure length without significant trailing. Say you have 0.1"/s drift and you image for one minute or 60 seconds - then you will have 60 * 0.1 = 6 arc seconds of movement between start and end of exposure. If you working resolution is 3"/px - this means elongation of 2px in direction of drift. Guiding performance is characterized by total guide RMS and RA and DEC RMS errors. Those are connected and total RMS is telling you how much your image will be additionally blurred over having perfect mount. Difference in RA and DEC values will tell you of any star elongation. Number is calculated as standard deviation of measured star position with respect to where it should be. Measurement is performed on guide star of course. When guiding, if you have round stars - that does not tell that you are guiding good - it only tells that RA and DEC RMS figures are about the same. What tells you that you are guiding good is total RMS error in arc seconds. As a rule of thumb you want total RMS guide error to be about half of your working resolution, but actual impact on final image resolution (star FWHM) is a bit more complex. Here is list of values and how they fare: 0.2-0.3" RMS - top tier mounts 0.5" RMS - very good performance 0.6-0.7 RMS - good performance 0.8-1.0 RMS - average performance >1.0 RMS - poor performance, acceptable only on low end mounts like EQ3 / EQ5 and AzGTI which are used to do low resolution / wide field work. If I'm using short FL lens and doing wide field image with say 8"/px - then I really don't care if I have 2" RMS error - as it really won't affect image at all (remember that half working resolution rule of the thumb).

Yes, it contains the same level of detail - if you process two images the same, you should get the same result. Only difference is that 3000x3000px one is 200% "zoomed in" versus 1500x1500 one. This is however too much of a zoom - everything there is in the image can be seen in 1500px version - although it is smaller - it is also sharper:

If you are using DSS - default settings are using interpolation to debayer and recover color information. This process allows to recover "full resolution" - so 3000x3000 color image, although there are in reality only 1500x1500 red pixels in bayer matrix (blue as well, and x2 this green ones). Here is how to setup DSS to use super pixel mode - it will result in 1500x1500 px image though:

Since you are using OSC camera - yes it would if you process OSC data properly and without interpolation. 0.69"/px is far to high sampling rate, but OSC cameras are in effect sampling at half of that - so 1.4"/px - that is very good working resolution for 8" scope (depends on the mount and your guiding performance as well). Use extender, and do super pixel mode or equivalent instead of interpolation.

Some people have very tough time collimating those. I managed to collimate mine without much issues (have 8" one). They produce flat field up to a point - after that you need some sort of corrector. On 8" version I use 4/3 sensor without issues. For APS-C sized - field flattener should probably be used (although it says corrected field up to 28mm). They are back heavy - plan for counter balance on the tube itself (I use 1kg Baader that attaches to the vixen rail). Stock focuser is not the best for AP (not sure which version comes with StellaLyra version - mine had simple 2" monorail with clamping attachment - I replaced that with 2.5" R&P and M68 threaded attachment). Other than that - I've seen quite a few people not happy with theirs and selling it. I guess it is down to "ease of use". I'm quite happy with mine and don't find it particularly hard to use.

You might be able to get some sort of color - but it will certainly not going to be true color or anything near it. There is no color in IR part of spectrum - but pixels can have slightly different sensitivity to same part of spectrum and that will give "impression" of color.

To me that does look like prism shadow. Take a look at actual prism/sensor and see if it is in that position relative to sensor. If it is - that will be confirmation. Make sure you move it slightly away from center of the sensor

Filter will do it's thing regardless of sensor used, so yes.

By the way - is this the same for both OSC and Mono sensor?

Is this affecting all ASI294mc-pros or just some? Could it be bug in drivers or something? I've seen many people do just fine with these cameras, and 120-190 gain range is the best one, so probably a lot of people will be using it.

I blame this part here: These clamped connections can easily introduce tilt. When assembling the setup - it is important that you hold firmly rest of the optical train against this clamping connection as you tighten compression ring screws (like "pushing in" motion with other hand). If you don't do that - it will "sag" under its own weight and be clamped like that - with a tilt. That tilt then might stay as is when pointing to the zenith as it is held by clamps. One way of checking if it is connection is to take two different exposures: 1. one as is 2. one where you rotate imaging setup by 180 degrees in that clamp You should get image that is 180 degrees rotated - if star elongation rotated as well (stayed with the stars) - then there is tilt elsewhere in the train, but if star elongation "stayed with the frame" (like again in top part) - then it is this clamping connection.

Not much of a news then - still not viable technology and going by current track record - we should not expect it working any time soon.

I've read some poor translation of this news from local news agency. Did they actually get more energy out then they put in? Unless that is achieved, it's not news really ...

It can also come from atmosphere - at least what people often perceive as chromatic aberration. If you see image like this: where there is vertical separation of red and blue parts of spectrum - it is atmospheric dispersion. It happens when bright object is viewed at low altitude - close to horizon.

Here is the thing - you can't zoom in indefinitely as there is limit imposed by optics, atmosphere and mount. Most galaxies are smaller than M101 you imaged and that one is 22 arc minutes in diameter. With something like 1"/px - being absolute maximum in realistic resolution in amateur conditions - that would make M101 be 22 * 60 / 1"/px = 1320px Even at max zoom level (if you are able to image at that resolution and still make sharp image) - you will need to crop your sensor if you are using something like DSLR with ~5000px in width. I would say that good working resolution until you really hone your imaging / technical skills is about 1.5"/px - that would make M101 - only 880px in diameter. Not sure if that would satisfy you (it is about x4 more zoomed in than above image of M101 you posted - but I guess that one was resized down). To realistically get 1.5"/px - you will need 6" of aperture and depending on selected camera - different focal lengths: 3.3um pixel size - 900mm of focal length with super pixel debayering 3.75um pixel size - 500mm of focal length (that would make setup ~F/3.2 - so not really option), or 1000mm with super pixel debayering 4.65um pixel size - 650mm of focal length (in this case - maybe go with 130pds?) or fast F/4 150mm newtonian. Alternative is to go with F/8-F/9 150mm scope for ~1300mm of focal length and use super pixel debayering. If aiming for this resolution with smaller scope - I would choose F/9 RC scope + 294 camera. Big warning - people have trouble collimating these scopes and many have given up on them. It is not easy instrument to work with for some people. Camera is also sensitive on calibration - most notably flat frames. I've seen many people report problems if they use flat assistant on APT. There were also thread about this camera saturating "early" - around 50000ADU with some gain settings - which again causes problems with flats if one is not mindful about that (and things that standard 65K is saturation point).

I don't use APP - but from what I see - it apparently can: https://www.astropixelprocessor.com/community/faq/bayer-drizzle-workflow/