152mm A+M Refractor(OfficinaStellare 1200mmF/L) using at Prime Focus ... a TeleVue 8mm Ethos Eyepiece without and filter and a RebelT7i modified UV-IR @ Hutech using the WB Custom-icon as a BlackCard image for the 'color balance' in the DSLR . This image here is to demonstrate a calibrated 'light' frame . What I saw in some images like of a far distant tower pole during the daytime was large dust donuts and small black specks . I also had to use on a 'single' image of the tower pole ... in MaximDl Pro V6.16 was the 'Auto Flatten Background' which removed the slight vignetting around the perimeter of the image and being it was a short 2.5sec exposure because it was starting to get a little darker as compared to bright daytime and it worked , but the dust donuts were still there . So , on March 29 2022 I thought that being it was clear and the would be clear , I made 'Flat' frame with the 8mm Ethos as eyepiece projection and without using a 'pin' or 'white' shirt to cover the Telescope . I could see the dark specks in the image and the large dust donuts and a smudge with a short ' 0.05 second ' exposure at ISO800 . I then took the DSLR off the eyepiece adapter and I cleaned the 'sensor' with a mixture of distilled water and 90% isopropyl alcohol and a q-tip and other q-tips to dry it to look clean . I attached the DSLR to the eyepiece again and I tried another exposure ... the specks and large dust donuts were still there ..!! ? . I cleaned the 'sensor' again and the 8mm Ethos glass and I did another exposure and the same artifacts were there . I realized they weren't on the face of the 'sensor' or the glass of the eyepiece directly in front of the DSLR ... maybe they are on the other side of the eyepiece glass or the other side of the 'sensor' glass or embedded in the 'sensor' glass during manufacturing and they can't be removed .... except with the use of 'flat' frames that show the artifacts existing . I did eight 'flats' and eight 'darks' for each ISO at the ISO's I use as ISO800 , ISO1600 , ISO3200 , ISO6400 , and ISO12800 . I didn't move the DSLR during this during a blue sky day and I imaged at night for the M1 for eight RAWMonochrome 16Bit Autosave Sequence 'light' frames with 67secISO200 flush-frames in between the 'light' frames ... the 'light' frames were 200sec each for ISO1600 and ISO3200 and ISO6400 and I did the "Calibrate" with the DARK and FlatMaters and then the "Convert Color - Scaling at 100% for the 'R' and 'G' and 'B' and the 'Auto' for Background 'un-checked' and the 'Reset' button used to put the Background data at 0% and the 'Under Sample' box 'checked' and the 'High Quality' box 'checked' for a Full ' color' application to the image which is a very ' red ' image " and after stacking you can then use the "Color Balance" which will change form 'red' to the approximate colors you want ; and NGC2392 and NGC6543 . I did NGC2392 which is this 200secISO800 FITS 'light' frame , one I did a "Convert Color" and the other I did the "Calibrate" with a DarkMaster that was done as Average and Auto-Optimize for Scaling .... but when I used the DarkMaster which still has the Bias included in it on the 'flats' for the FlatMaster , there wasn't any data in the FlatMaster . I tried making a FlatMaster without any DarkMaster and when I did a "Calibrate" the image was removed and the FlatMaster was the look of the image and total loss of the real 'light' frame . I tried for the Darkmaster 'calibrating' the 'flats' to make a FlatMaster with 'Auto-Scale' and that didn't work either . Then I did the 'flats' again with the original DarkMaster and this time I used the 'None' for the Scaling and the FlatMaster looked like a 'single' 'flat' frame . I did a "Calibrate" with the DarkMaster and the FlatMaster as 'None' for Scaling and the 'light' frame wasn't damaged . Both images were done with "Convert Color" , and then "Color Balance" with the 'Mouse' for 'Background' which made the background color look more normal ;; but when using a DarkMaster and FlatMaster ... you must do a 'Save As... IEEE Float to retain the image or it will not have any data in it as 16Bit FITS ... like during the "Batch Process" command which you must also have the 'Save As...' command 'checked' so you can then manually do the 'Save As... IEEE Float' and then the image will leave the 'buffer' and then next RAWMonochrome image will appear for the 'batch process' . Then after stacking you can do other commands , but , to begin with you might have to do the "Resize" if you use it and then a Bin2 because the "Half Size" which is a more strick Bin2 command might put line artifacts into the image . Then I did a "Resize" as 3.72microns to 6.5microns and then a Bin2 . I then used the "Kernal Filter-GaussianBlur to smooth the background around NGC2392 using 'pixels-restrictions' from 500 the about 2000 and Radius: 2 and Feathering: 3 which smooths good enough . I put the two images at Max-Val 'screen-stretch' and I used the "Digital Development-GaussianBlur: 1.0 and the two 'check' boxes 'checked' for 'Auto " ; then the "Color Smoothing as FFT Low Pass and FFT Hardness as Hard and Weight % 25.00 " . And these two JPGs show their differences . The 'not-calibrated' JPEG has distortion in the background and the 'calibrated' JPEG shows a smoother background with out the distortion . << I think if I try on another clear blue sky day using the Telescope and then the RebelT7i using a 2in. 'nosepiece' to do a Prime Focus shot and with a 'focus' position at a far distant horizon object and the back at the blue sky facing away from the Sun ... some 'flats' without an t-shirt covering on the front of the Telescope to then check the 'flat' frame for the above mentioned specks and large dust donuts .... and if they are there that means they are behind the 'sensor' glass and they can't be removed ... except with the use of 'flat' frames like mentioned above . It might also be possible to use this type of 'flats' on any Configuration without having to make then at a Configuration because with a mild 'flat' frame that mainly reveals the artifacts to remove them might be an all purpose DarkMaster and FlatMaster 'calibration' technique that might not add unusual vignetting to a 'light' frame using different PowerMates or eyepieces ... but something you always use might need it's own 'flats' if the spacks and dust donuts can be seen using them especially if you know the artifacts are seen at just Prime Focus without any Flattener glass or filter . Just by using the "Auto-Flatten Background" on these stacked images might only be putting a large donut artifact of it's own and can't be used . If the 'calibrated' image here also does that to other 'light' frames it might be worth trying it yourself . x ***************************** MaxIm DL Version 6.16 started on DESKTOP-QCLR41U Process, Stack 8 files added in 1 group (new) [11.03 sec] View, Zoom In: M1-0001-ISO1600-new.fit [Reference image] Added 8 images for M1 [69.94 sec] Sigma Clip factor 9.50: clipped 2.9% (2126051 of 72685584 pixels) Sigma Clip combine succeeded using 509488KB memory [16.59 sec] Process, Stack (OK) View, Log Window Screen *************************** I think I have found a better 'focus' position at the 103mm DrawTube scale on the Starlight Instruments 3.5in. Focuser and Monday night it should be clear and I'l try the M1 Crab Nebula again ; I did use the 103mm line on the DrawTube which isn't mm's and is just a scale they have on it and the M1 here was at the 'focus' position with the 100mm line just out from the DrawTube , and it was close to the best 'focus' at the time . If I do find it's at a good 'focus' and the stars are good across the image I'l be glad .... but there is an alternative if the stars don't ever focus good across the image and that's a TeleVue Paracor $517.00 that must be used to do it which takes care of the 'coma' at the edges for stars . The TeleVue site has a lot of pages you can save to a Folder to read about it . Astigmatism is a blur in the eyepiece that doesn't seem to get into focus and they say the Paracor can help an eyepiece come to focus . The Paracor is a 2in. barrel that inserts into the DrawTube and the eyepiece is inserted into it and there are some adjusting options . Baader also has something like the Paracor that is an MCPP for $217.00 with two parts that are needed that cost $35.00 each and the barrel is also a 2in. size . x ***************************** In "StarryNightPro" they have 'pulsars' and there is one that will show for the M1 Crab Nebula and then when you "PinPoint Astrometry" 'solve' as J2000 coordinates the 'pulsar' is ( PSR 0534+2200 } and it's 6500lys away and J2000 RA: 05h 34m 31.98s and Dec: +22* 00' 52.08" *************************** The 'FlatMaster frame image shows the dust donuts .x
