SoftwareDeveloper

The 4 spikes on the stars is likely due to the spider at the front of the Newtonian OTA. The 2 oclock blur is odd, its not symmetrical with another one at 7 oclock, so this is a reflection off of something, look at your setup, its most likely something very simple once you see the source. If you are new to imaging, I would call this a very satisfactory starting point! Improvements are slow and tedious and sometimes they happen in the "wrong direction" and the improvements have to be undone.. such is life I suppose! As to the spider, one with curved arms can reduce that diffraction pattern and fix that. The 2 oclock issue is not so obvious, let us know what you find.

Hello Lee, when you take an image the orientation is usually changed by the geometry of the mount, especially with a German equatorial mount. However, when you take the image you can post it to nova.astrometry.net. The result will give you the orientation, but in a form that is not in "plain English". The trick is learning to understand four numbers: CD1_1 = -0.000183421732869 / Transformation matrix CD1_2 = 0.000492781214588 / no comment CD2_1 = 0.000492636225707 / no comment CD2_2 = 0.000182967937627 / no comment Those 4 numbers are a complete description of how the camera was rotated relative to the celestial sphere. I dont remember the exact equation, but the direction of the north celesial pole from the center of the image is something like: North=atan(CD1_1/ CD1_2) I regret its been a while since I needed that info and have forgotten the specifics. Its in the FITS specification pdf files. (Boring reading) But the angle is very very precise. So you might look into that and save the wear and tear on your hardware. The scale of the 4 values is the scale factors for X and Y in the image, so that is related to the image size of a single pixel. The second 2 numbers are directly related to the first set, and indicate if the image is "direct" or "mirrored". Another little detail: the SIP part of the FITS header describes any distortion found in your image, this can be from refraction, seeing, etc. If you dig into the math there is a ton of info in there. I can certainly understand if that seems like too much trouble tho. That can be a useful diagnostic source when you get the hang of what it means. Hope that makes sense- and was useful!

@vlaiv The issue is noise. Red is 2x more noise than Green or Blue, that is with cooler ON and at 0C. The images are more noisy than my other cameras, that can be overcome with more subs.. Hope that explains the issue. @Zippy_McSpeed Since you and your wife have computer backgrounds, you will find you can write a great deal of your own software (as I have). Getting started, I strongly suggest use off-the-shelf software and hardware until you get your first good results, then look at where you can supplement the programs you use at the beginning with ones you customize to your needs. Before you buy a camera from any vendor, I suggest you download their developers API interface. Does that make sense to you? If so.. you are in good shape. If not.. find one that does, as that may be a key to getting the most from your equipment in the future. Also, you mentioned mounts. Look into the computer interface to the mounts, not just ASCOM and ALPACA, can you communicate with them directly? Some mounts allow direct communication with the hardware in the mount itself (via wifi, ethernet[X-BaseT], USB, or RS232), others require you plug into a hand-controller via RS232. The hand controller then becomes a dongle that is always in the way. See if the mount can run with no hand controller, much better for direct computer control. Another issue is the connectors mount manufactures seem to prefer: phone jacks. RJ-11 et. al. Those were designed by the telephone industry for only a few insertions/removal during their lifetime. Using them for a hand controller, or RS232 interface is asking for a short lifespan as those get plugged/unplugged often. That is not a huge sticking point, but it does become an issue. Most of the folks I know who have owned their telescope for several years or more have had to replace cables with broken connectors. Then sometimes the replacement cable is a 'reverse' cable of the one needed and the next thing that happens is some magic smoke comes out from somewhere. (This has happened to me, and no doubt others.) Good luck, whatever you start with, you and your wife will have fun. It certainly provides something to talk about, and that is a very positive thing! :)

Since your question is posted in the starting imaging forum, I presume you intend to use a camera without an eyepiece. Physics is not your thing, but a simple calculator can provide you the answer: If the camera active sensor width is W millimeters, and the focal length of the telescope is L, the rigorous equation for FOV (field of view) is: FOV = 2*atan(W/(L*2)) a good approximation for the FOV just drops the two "twos" and is: approximate FOV = atan(W/L) That is for a camera with no eyepiece involved. Hope that helps

@Zippy_McSpeed Regarding your thought about getting a ZWO ASI183MC: I have several cameras, one of them is the ASI183MC, its the only camera I have regrets for purchasing. Its not a "bad" camera, its just not as good as it "should" be. I have several other ZWO cameras and they all work well, the issue is the sensor used in that model. Several other models get very good reviews in the community, so I suggest you look into one of the others that does not use that particular imaging chip. If that was the only camera I had, I would use it. Sometimes I use it for a guide camera now, most of the time it sits on a shelf unused. ZWO stuff is very good overall, I have nothing bad to say about them (many positive things in fact!). QHY products are good also, pricier, but not ASIAIR compatible (a competitive issue most likely), but QHY upper end cameras have one other possible advantage- the GPS box which will stamp each image with precision time and location, ZWO doesnt offer anything equivalent (I wish they would). For simple imaging the time of the exposure does not matter, but with anything that moves, its really useful info. Things that move- the moon, sun, planets, comets, asteroids, satellites, etc. Precise time is an advantage if your hobby grows in that direction. You can also purchase another camera later when that becomes desirable. Just my suggestion- look into other cameras. I suspect there are folks getting great results from the 183, it just makes me wonder how much better they might have been with something else..

JackO, I took the liberty of downloading your images, and since you specify what camera you used- I had my plate solver measure the images and give the measured focal length for the images. Assuming the ASI2600 was used for both images: The measured focal length for the Andromeda image is 346.2mm, and for the westveil it is 347.6mm. That is a 1mm shift in focal length between the two, one possibility is one includes a filter in the optical path that the other does not. But the focal lengths should be almost identical when the images are in focus. So what SHOULD the focal length be with the flatner and without it? You did not specify what optics train was involved in each case. I thought the results worth sharing as they may help suggest adding or removing spacers until the design focal length matches the measured value. Note- the plate solver does not know what sensor is being used, so several common cameras are given as possibilities. It assumes the correct value can be chosen from the table. Also the output is in HTML format, which is a container for a copy of the image, annotations, etc. I will attach the plate solver output for each image. Hopefully this helps with deciding what correction may be most productive. andromeda.jpg.962de187d741884cc019fd3cdcf384b7_data8.html westveil.jpg.0473a1dc1ef3505f30e1aa15b1151e34_data8.html

I own a ASI183MC Pro, and have had mild regrets. The Bayer filter is not great, all images start out with a blue cast to them, even with the lens cap on. I have wished I had bought the MM version, the resolution however is very nice and I can could have gotten color from RGB filter sets just as I do with my other monochrome cameras. The 183MC is one of my two color cameras and I find I prefer monochrome cameras, for me as a software developer that is not an issue. Your choice should be based on your needs and capabilities. Color cameras are less sensitive than monochrome, so I have wondered how much better the 183MM would have been at the same images. Too small of a budget to find out! Sigh. LIkwid, you will find either camera enjoyable and the slight advantages that one might have over the other in a particular situation is so minor its not worth the fear it causes. I suggest the MM version of either camera, but that is for my style of photography. Pick one and get started! You can have a great time with either one! You will get good experience either way. :)

Uranium 235.. I thought I would borrow one of your images to test a platesolver I wrote. Thought I would share the result. Enjoy 12936956565_1e1bbd6b20_b_data8.html

Just a suggestion, but uncooled cameras are best for bright things, daylight imaging is what the market is for the manufacturers of the chips. The astronomy community has bright targets, planets, the moon, bright stars, etc. When the camera is cooled, new possibles exist: faint things. In astronomy more things are faint than bright, and cooled cameras have a distinct advantage. The coolers are all programmable, and can be turned off- leaving the camera in the "simple" case. The chip manufacturers big market is consumer photography, so the chips are designed for that purpose, then a few specialty shops use these chips that are already being made in large quantities, and put them into packages with TMounts and USB, for astronomy, often adding a cooler to improve the cameras for the needs of astronomers. One byproduct of this mass market product is almost all chips are manufactured with color filters on them (Bayer filters). Unless you understand what you are doing with the spectrum, using more than one filter at a time is usually a bad idea. Since one filter is already installed on color cameras, that means putting another one on is more likely to just reduce the camera sensitivity than do anything useful. So.. if possible get a monochrome camera. The good news is there is no filter police running around checking to see if folks have more than one filter installed. But imagine that a dozen filters were used at once, very very little light would get through! Just one filter with very very few exceptions. So, one other advantage to a monochrome camera is they are about 4x more sensitive because the Bayer filters lose 3/4 of the light! To sum up my suggestions, get a monochrome cooled camera if you possibly can. Then get external R/G/B filters, and you have color when you want it and sensitivity when you want that. An inexpensive uncooled color camera does get you started for less cash, and I understand that motive completely. The only caveat to my suggestion is color cameras work better things that move very fast- the one place in astronomy where they have value is "lucky imaging" where a huge number of photos of a planet are taken very very quickly, then the best parts of each image are stitched together to make images that look like they were taken with Hubble telescope. If that is the path you want to take, go color, but go cooled so you get less noise. :)

Just my $0.02 worth.. get the best mount you can afford. Then use a camera you already own and a telescope you own. This hobby is enjoyable from the very first photo. People want to take a masterpiece with their very first shot. (me too) But years of trial and error have slowly resulted in getting better equipment and understanding how to get the most out of each component. The main thing is get started! If possible start with things you already own. Figure out what would make the greatest improvement and that is where the next expense should be. If you have a camera and a tripod, try them! See what you can get with what you own. No need to go invest a gazillion in cash for the very first image (unless you are government funded!). There will always be one more thing that would be great to have. But quoting that great philosopher Cheryl Crow: "Its not having what you want, its wanting what you've got". Perhaps Cheryl has tried astro photography.. hmm..

Using more than one filter at a time is usually counter-productive. Since the ASI533MC is a COLOR camera it already has one filter above each pixel. So.. adding more filters is likely to just make frustrating imaging. Here is a more/less typical bayer filter for a COLOR camera: https://micro.magnet.fsu.edu/primer/digitalimaging/images/cmos/cmoschipsfigure4.jpg Because the pixels sensitive to each of the "human eye" perceived colors tend to reject light at other colors, a filter placed in front of the bayer filter will usually only allow 1/4 of the pixels see light (if the light passed through the new filter is predominantly red or blue Rg/gb or rg/gB ). So the result is to discard 3/4 of your sensor! Woops, not usually a good idea. If the filtered light is in the green bandpass 2/4 (rG/Gb) of the pixels will "see" the light. Better, but not a lot. The idea of discarding half of a sensors data is well.. That is why astronomy cameras are usually not color. Then ONE filter at a time makes sense. Where to put it? As close to the sensor as is practical. I suggest that the color camera will get nice photos and should get nicer photos with no additional optical filters. After the images have arrived in the computer, feel free to manipulate those colors any way you like Hope that makes sense. Save your filter budget for a monochrome camera, the results will be better as ALL the pixels can measure the light that gets through whatever filter you use, and now the meaning of the pixels is vastly easier to understand. Hopefully that makes sense.

Greetings OK Apricot, My suggestion is pick a cooled camera you can afford, know that monochrome is about 4x more sensitive for the same sensor than color. Dont fret the details too much, find something you can afford and take the plunge. A camera and a telescope completely change the experience of astronomy. Expect to be amazed at what you can image. The most humble modern camera with a very humble telescope will usually outperform the imaging that was only possible with state of the art observatories 75 years ago. Amp glow in a modern camera would disqualify it from consideration - IMHO. The manufacturers have usually provided solutions for this problem years ago and its almost a complete non-issue. That should not add to the price. Expect a camera to be able to do long exposures of many minutes, even tho as a beginner that feature will require growing into. A good frame rate is handy for focusing. The same camera should be able to take very short exposures, a millisecond or less. Most cameras go down to a microsecond or so of exposure time, those short exposure times are good for pointing the telescope at some distant scene (Not the sun!) and focus and experiment in the daytime with your new camera. Figure how it all goes together while its easy to see. Also, there are many camera vendors who get their sensors from the same few companies. So, the important things are cooling, and sensor dimensions. Megapixel count is nice but usually these cameras get operated in a "bin mode" that reduces their resolution to make the image sizes manageable. So no point in spending money on a sensor with zillions of pixels. No matter what camera you pick, later you will have a much more intuitive understanding of what other cameras might do for you. Save some money for a second camera, and the first camera doesn't go to waste, it can be used for guiding with a very small piggyback telescope. Remember to hold come cash back for adapters. Almost no camera connects to a telescope without adapters. Put that in the budget. Lastly- Expect to be amazed!

Debayering is not a single thing, there are a good list of ways to do it. Check with the wikipedia on the subject (https://en.wikipedia.org/wiki/Bayer_filter#Demosaicing). The fastest algorithm is not great for astronomy (nearest neighbor). I cant recommend a specific program, but look for one that supports choices in the algorithms used. A downside of better algorithms is they are usually noticeably slow. Where you will find issues with debayering is when you zoom in on a star and you get "colors" that are not really there. Your noticing a green cast should not happen, that is a sign that something is wrong, even when using fast/simple approaches. Making three exposures through three bandpass filters avoids the issue completely, and allows a monochrome camera to be used which is about 4x more sensitive to light when no filter is employed. This is why many astrophoto enthusiasts use filter wheels. Personally I own color astronomy cameras, but prefer monochrome/filter wheels. The downside of filterwheels is image registration and processing into an normal color image. Another advantage of the three filter method is an RGB image can be made from narrow band filters using specific emission lines mapped to the color planes. Very impressive looking images can be created this way, but its not a "natural color" image at that point. Combining bandpass filters with a camera having a bayer filter grid, usually creates a mess and takes much longer exposures to get less satisfying results. Interpreting the results in any metric sense is shot in the process, as the bandpass for the individual RGB filters in the bayer array are usually not calibrated. Certainly good results for "natural color" images can be obtained with either approach. Pick one and you will end up making great photos if you stick with it. :)

Hello, this is my first post to SGL, so be kind with replies! TIA.. Richard, and other interested people- Its possible to measure the focal length of your telescope using astrometry.net. Take a photo of any star field with each camera and upload it to astrometry.net. In the results for each image (typically) on the fourth line of the calibration result summary is a field "Size: WIDE x HIGH deg". Wide is the horizontal (wider) field of view for the image. Using the cameras pixel width: 3008 for the ASI533MC, and the pixel width in micrometers: Pixel Size: 3.76µm (from the camera spec web page) compute the horizontal width in millimeters for your camera: xWIDTHmm = 3008 * 0.00376mm -> Width_mm=11.31008. Be careful not to use the diagonal size of the focal plane that would mess up the calculation. Now use the following equation: FocalLength_mm = Width_mm / (2.0 * (tan(FOV_X) / 2.0)) With either camera, the measured focal length should result in the same value (within about a millimeter). If not, there is a problem. If the measured focal length is significantly (more than 1% ish) different than the manufacturers spec for the telescope, again something may be wrong. Note: these measurements should be made with the filter wheel to an OPEN position. Filters change the focal length due to the refractive index of the filter material being different than that of air. Also if your calculator can only work in radians, be sure to convert FOV_X to radians before calling the tan function, otherwise some strange results would occur.. That may or may not help with your picking spacers for the your cameras, but it does check the basic math. Hope that provides a useful tool for evaluating issues like this. End of first post!