Re: [Losmandy_usekrs_io] PEC training
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I am going to put a 2X barlow in front of the SX guide camera and use binning on my SX 814. I will then see if that has an improvement. I am sure it will. I have used the 2x Barlow in the past when I had an F10 C11 and it helped. I had just forgot about it until I bought this SX 814 and its smaller pixels. Thanks for reminding me. ? Aubrey ? ? ? Sent from for Windows 10 ?
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From: Brian ValenteSent: Friday, December 11, 2020 7:58 PM To: [email protected]Subject: Re: [Losmandy_users_io] [Losmandy_usekrs_io] PEC training ? Aubrey if you are going to stick with your current setup, i suggest binning your imaging camera bin 2. that will definitely help ? Thanks for info on OAG. I have tried them on my gear before and it is mostly frustrating. Hard to find star bright enough to use. I also have a STT-8300 with self guilding but The 340 chip is not very sensitive. ? Aubrey? ? ? Very good data. I can add a Barlow of 2x on the guide camera and that? should drop it to 2.00 /arcseconds. ? I am not sure I have been keeping the guide log. I see and send the data to you if not I will start it and send it later. ? Aubrey ? Sent from for Windows 10 ? ? Hi Aubrey based on that information here's some details for you: your image scale for your guidescope is 4.00"/pix or 4 arcseconds per pixel.? your image scale for your imaging setup is 0.47"/pix or about 1/2 an arcsecond per pixel So your imaging camera is about 8x finer than your guiding setup. My guess is you are guiding as too coarse of an image scale to guide effectively for that imaging setup your guiding would ideally be <0.5" which for your guiding setup would be 1/10th of a pixel on your guide camera. that is about the limit of what phd can handle.? There are a lot of other things that would need to come together for your imaging image scale as well.? do you have an example guidelog to look at? might be able to give you some more feedback there ? OK here we go. ? Guider:? SX Super star guider on 60mm guiding telescope F/4 ??????????????? Pixel 4.65x4.65 ???1392x1004 V ? Main camera: SX Trius Pro 814? ??????????????? ??????????????? 3.7 x 3.7?? 3388 x 2712 ? Telescope AT 10¡± RC 2000 mm FL ??F/9 No focal reducers, etc. ? ? Thanks. ? Aubrey Sent from for Windows 10 ? ? Hi Aubrey Aurun pretty much nailed the answer.? the relationship depends on the image scale from your guiding setup and the image scale on your imaging setup if you can supply this info i can give you a better answer Imaging camera (make/model, pixel size, sensor size in x-y pixels) imaging scope (make/model, focal length f-number) ? Very good Arun, I have never heard that before. So if you move from an STT 8300 with the Kodak Chip 5.6 Pixels to a Starlight Express 814 with 3.6 pixels, on an 2000 mm f/9 scope what effect would you expect to see? ? Aubrey ? Sent from for Windows 10 ? ? RMS stands for Root Mean Square. It is a measure of, on average, how large the deviations are from the baseline. An RMS value of zero means a perfectly flat graph.
In the context of autoguiding, we are concerned with how far the centroid of the guide star deviates from the point where it should be (or we want it to be). These deviations are measured in two directions which are at right angles to each other - Right Ascension and Declination (RA and DEC),
Now think of your star as a circle with two diameter lines at right angles to each other.
If the deviation in the direction of RA is greater that in DEC, the diameter of the circle is greater in the RA direction than in DEC. The circle is "stretched", it is no longer a circle, but an oval or ellipse, longer in the RA direction than DEC.?
If the RA and DEC RMS are close to each other, then the circle remains a circle.
Now you can also think about the case where the deviations in RA and DEC are both close to each other, but both very large. That's still a circle, but a rather bloated one. Your images will have round stars, but large ones. Fine features of your image will be smeared.
The ideal case is when both deviations are much smaller than one pixel in your image. At that point, all the deviations are "contained" within one pixel, and your guiding no longer limits the size and roundness of your stars, nor feature resolution. The finer your image scale, the more demanding your guiding becomes, and the more you'll be able to see faults in your guiding. Many people consider that a value of lower than 0.8 " RMS to be a good number to aim for. Because at point, under most conditions, deviations caused by things like atmospheric seeing become more critical. With proper polar alignment, balancing, appropriate clutch tightening, etc., you should be able to guide consistently under this value with good mounts. That has certainly been the case for me (with some work) with the GM811G and a small (80mm) refractor.
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