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Hi guys! What do you think?? a) Is it better to do 5-min subs or 10-min subs? Does anyone have experience? b) Is it OK to combine different length exposures in DSS when they are put into different groups? Camera: ZWO 533 MC Best Regards Jan |
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Hi! I allways did 600 secs (10 min). It was way more signal and less noise. Had the same camera 😝 Its a very good combi. For 10 mins make sure the object is at least 30 degrees obove the horizon. Seeing is really bad underneath it. At leat here in munich 😅 |
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Diffrent focal length is tricky. Depends on how much diffrent. I conbined 750 with 1000 (same camera and pixel pitch) was not a problem at all. I think 400-1000 is too much ( same camera) The pixel per arc sec is important. You can combine a 400mm apo with 3.6 pixel pitch apsc and a 1000mm fullframe pixelpitch 6.8 for exampe. Both have a quite similar pixel/arcsec value. |
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| I usually use 20-minute exposures with L-eXtreme and now the Antlia ALP-T. When I have compared images with 20-minute and 5-minute exposures having the same total exposure time on my equipment, the longer exposure result has always had more detail in the very faint areas. In theory, with perfect linearity in the ADC, it should make no difference, but the result I get says otherwise. It may also depend on the amount of light pollution you have - I'm in a bortle 5 location. |
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Hi Jan, You may find that even five minute subs is way too much. With older CCD cameras, such long exposure times were necessary to swamp the read noise of the camera. Modern CMOS cameras like yours have such low read noise that this is no longer necessary. I used to do five minute subs for broadband and ten minute subs for narrowband imaging with my ZWO camera. Then I did a sensor analysis using SharpCap Pro and it indicated that under the Bortle 3 skies where I live that the ultimate best exposure to record the faintest detail possible was 96 seconds for broadband, two minutes for Oiii and five minutes for H-alpha. The individual subs may not look wonderful, but when they are stacked you get beautiful, noise-free images. The manual to SharpCap and a video by the author clearly demonstrate the diminishing returns achieved by imaging subs for any longer length of time. Depending on the brightness of your sky, presence of light domes and the altitude of your target, your times may vary. The beauty of the sensor analysis and Smart Histogram calculations, though, is that it gives you the best exposure times for your individual conditions and equipment and prevents wasting precious dark sky time on unnecessarily long sub exposures. Arnie |
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I think 600s is excessive with this camera, it leads to blurring and insufficient number of frames for CFA drizzle and proper pixel rejection. Remember you have 2 x 7nm passes in this filter, effectively 14nm. The only time I'd use more than 300s is with a mono camera and 3nm NB filters in dark sky location. Stick with 300s, less smearing, more frames for CFA drizzle which is quite important. You won't get anything more with 600s, it's a vestige of old CCD camera which required such exposures due to having huge read and dark noise components that had to be swamped. |
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| Guys, thx a lot to all of you! I was not sure if 5-min subs are enough with L-eXtreme, because subs looked not great (The Wizard Nebula; Bortle 7 & under full moon), but know I believe it's the better way! Thank you kindly! |
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Several reasons why I will not go over 300S. Depending on filter, and image I have a few settings that I use, and none of them are over 300s. These types of cameras do not need it. Also, imaging time is very dear, and rare, I hate it when I have to toss a 300s sub, I cannot imagine the rage I would feel to have to toss 1 or 2 of these super long subs. I also have this filter, and what I can say is the only filter I every go for 300s subs is my QUAD filter. I found with the LExteme, images that were longer than 180 sec, tend to start to over saturate, and look faded. I remember when the best I could do was 15 sec subs, I so wanted to do "long" exposers, yet when I finally had the ability to track properly to do so, I found that it is not such a great idea, nor was it needed. Sharpcap as well opened my eyes. I watched one of his training sessions where he talked about exposure times. I also use sharpcaps feature to analyze the area you want to image, and provide you with settings you can use, while I do not always agree with some of the settings it offered, I never once had to tell me to ever go longer than 5. As for mixing different exposure times, yes as long as you have the correct calibration frames. I image over several days, and sometimes I will use different exposes and filters, again, as long as you frame correctly, and have the correct calibration frames to match each exposure time, you are good. At the end of the day, it is your image, your vision, and if you are happy with your work, that is all that matters. |
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Robert Winslow: @Robert Winslow Yep, I saw these Sharpcap videos few days ago => and it was clear that for broadband imaging are long subs not needed, but not so clear to me for narrowband 🙂 Tell me about these QUAD filters - it's worth the money? Is it way bettter than L-eXtreme? Also worth mention - I read that not every filter L-eXtreme is the same in case of performance, so I am a little bit suspicious that my L-eXtreme is not performing well in HA... |
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Hi! i usually use 1000sec on focal ratio f/5.35 and ASI294MC at gain 120, and i have a good compromise with time/details/noise. For the theory the result is the same for same integration time, then 10x300sec is the same like 3x1000sec, but in the practice, relative to your shooting system, the solution with longer frames is less noisy. Are not only good things, loss some frame, for any case happening, with long frame is a lot of time wasting, with short frame is a small problem. You can find your correct exposition time by a compromise with shooting system, subject, camera and sky |
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Jan Klíma:Robert Winslow: Yes, the Quad is well worth it, especially if living in light polluted areas. I wish I had purchased it before I spent the money on the L Extreme, and a dedicated SI filter, but I know they will still have uses. The image quality from these filter is insane, I get so much more dynamic range. It does require longer exposures, and this is the one filter where I do run it at 300s. Yes, it is an expensive filter, but it lives up to the hype. Check out my image of the witches broom, it was done with that filter, and i feel it is my best image so far. A few of the days the moon was up and bright, added to a backyard that has lots of light pollution. Now, some objects will image better using a different filter, this one is strictly for nebula, however I did hear some people use it on nebula like galaxy's. Many times we are fooled by the claims of vendors, and many times we are disappointed with the product. I was also a bit worried as only one company makes this filter, so I did not have any way to compare. This product was worth every penny, and I would highly recommend it to anyone who images nebula. So here, you be the judge https://www.astrobin.com/kag5v8/ I did normal post processing, I did not have to up the color saturation. I also have the option of extracting the Ha and OIII to use the HOO color combo, or you can process it as RBG. That image was processed with just RBG. Note that I was even able to capture some of the very fine filaments, from what I understand that is not so easy to do. |
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Robert Winslow: Frankly I'm flabberglasted by the kind of money they're asking fo a single filter and I can hardly believe people are paying more money for it than the scopes it is sitting on. Wouldn't it be better saving up for a mono camera and normal SHO filters? |
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| Another option to consider is the 5nm Antlia ALP-T. I have switched to the Antlia from l-Extreme and it doesn't have the issue with the star halos like the l-Ex does. |
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andrea tasselli:Robert Winslow: Yes, I agree, all these filters are expensive, but from what I understand they are not easy to make. I can assure you, I would never pay more for a filter than my scope, I have the Recat 71, as well as the ESpirt 100 ED APO. I would first upgrade my image train before sinking that much in. AS for Mono, and SHO filters, yes it is better, but it has its own problems, and as a person starting out, I wanted to deal with one set of problems. It was hard enough for me to manage all the different calibration frames required without adding to that number. Now will I one day go that route? Yep, you bet as mono allows much greater dynamic range. For now, this over priced filter, provides me an advantage I did not have prior to it. I do admire people that have the skill to do that long complex process, one day perhaps. |
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Jan Klíma:Robert Winslow: @Jan Klíma The SHarpCap procedure is the same for narrowband as for broadband filters. All it does is measure background sky brightness in the number of electrons received per pixel on your sensor per second. The narrowband filters reduce this number by reducing sky brightness, but the result is still tailored to your individual circumstances of sensor, light pollution and altitude of the object. As an example, I used to take thirty minute H-alpha exposures with my SBIG ST2000 CCD camera. Under the same conditions, SharpCap recommends 4' 36" exposures with my ZWO ASI6200MM camera. I round it up to five minutes for the ease of creating a dark library. Armie |
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| I live in a bortle 6/7, and with a dual narrow-band filter for with my 533 or 2600, I typically go with 300s. BUT, you should experiment with different exposures on your own. Your equipment, light pollution, etc will be the determining factors. |
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I live in a bortle 6/7, and with a dual narrow-band filter for with my 533 or 2600, I typically go with 300s. BUT, you should experiment with different exposures on your own. Your equipment, light pollution, etc will be the determining factors. Good morning Mikey! Yep, that's my case! And whatabout targets with magnification 11 and so? Still 300s? RegardsJan |
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Jan Klíma:I live in a bortle 6/7, and with a dual narrow-band filter for with my 533 or 2600, I typically go with 300s. BUT, you should experiment with different exposures on your own. Your equipment, light pollution, etc will be the determining factors. It again depends on your equipment. For me, if I shoot too long, the light pollution will creep in and start to make the image difficult to work with. I personally try to make my individual frames as short as possible, while capturing as much as I can, and just shoot more of them. It does take longer to sort though and stack but I think the results are better. Being a newb, I might be taking the wrong approach! My current mount doesn't usually do so well at 600 seconds or higher, so again, your equipment is a huge part of the equation!!! |
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Jan Klíma:I live in a bortle 6/7, and with a dual narrow-band filter for with my 533 or 2600, I typically go with 300s. BUT, you should experiment with different exposures on your own. Your equipment, light pollution, etc will be the determining factors. You are definitely NOT taking the wrong approach! Between light pollution gradients and tracking errors, you'll do much better with more, shorter exposures than you will with fewer, longer exposures. Arnie |
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When I started, I was lucky to be able to image more than a few seconds without issues. I wanted to image much longer; I was thinking 30-60 minutes. After I had all the gear, and software I needed to make this happen, by that time I had learned that long exposures are a myth and should be avoided. While I am sure there are conditions as well as equipment that might make my statement false but the cost of that puts it out of most people's range. I know how much I needed to spend to get the equipment I needed, and based on what I see, I am on the low end of the price range. So, I did, I tried super long exposures and I was not impressed as I lost more data than I captured. Any slight correction shows, anything that fly's buy is a frame that is useless. I also watched the Sharpcap videos, and that was an eye opener and told me I am doing it wrong. I live in a very light polluted area, all images that I took with long exposers ended up washed out, over saturated, or so much light pollution that the images were lost to the lighting. So Sharpcap to the rescue, after playing with its suggestions, and seeing the different settings it recommended, based on object and sky brightness. I see that long images were not needed. Now, there are times when it tells you settings that are so short that the amount of data collected would be insane. What I learned from that was it was a bad object to try and image, or I needed to use a filter. Object selection is very important as well, if the time and or year are not correct for the object, you need to move on. A tool I found useful but too expensive IMHO for what it does is Skytools 4, it does a good job of giving you detailed info on the object based on your equipment, location, and filters. For me, I was not happy with my images until I learned these lessons. Now, the only time I do not have a filter on, is when I am plate solving and centering on target. Once that is done, depending on target, depends on 1 of 4 filters I will use. If it is a nebula, then the choice is one only, that is the Quad filter. |
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Robert Winslow: Hi Robert, I know what you mean about huge amounts of data. When SharpCap recommended 96 second Luminance exposures for my camera that outputs 26 MB files, a total of 10 hours integration would have resulted in 9.7 TB of data! Just for Luminance! So in those circumstances what I will do is allow SharpCap to Live Stack 3 - 5 minutes at a time, save the image, and then start another stack. I then have a much more reasonable number of sub frames to load into my processing software. Anrie |
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Arnie: I am not sure if I answered this. I am very pleased with this filter; I have images I took with the L Extreme and the Quad. For me the difference as astounding. I was able to image longer without filling the wells with noise, and the detail it pulled out on nebulas was fantastic. I also like the fact I can extract the Ha, OIII so I can do the HOO processing. AS it is Quad, I have yet to find a way to extract the Hb, and the SI, nor do I know if you can and most times, I process it just like a normal RGB, and sometimes I extract them. Yes, it is an expensive lens and lucky for me, I am not using the 2" as that price is even more. Yes, I did question my sanity in buying a bit of glass for that much, but after what I had invested to get this this point, I jumped. I started this hobby as I wanted something different than coin collecting, I figured it would be an inexpensive hobby, and I should have known better. |
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Robert Winslow:Arnie: One need not question one's sanity in this hobby. One just needs to wish it a fond farewell. I would love to have one of these, but seeing as I just bought a Celestron C14 EdgeHD, focal reducer, OAG and guide cam, it's going to be awhile. A long while! Arnie |
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Jan Klíma: 10 min subs are the best to go. About the dss question, it depends on your dss settings. https://youtu.be/EMdEhQD2WxY |
