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wetcoaster

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About wetcoaster

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    Nebula

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    Vancouver
  1. wetcoaster

    Master Dark subtracts too much noise?

    Alan - Your detailed replies are much appreciated. I need to wrap my mind around the electron to ADU explanation. I'll post a flat when I have some time. As for the floating point output, it is the default. I'm not clever enough to know the meaningful differences between the various options. Perhaps a signed integer might be better. I'm focusing on tonight's run. I am enjoying a wonderful streak of good weather while battling some issues like why my Polemaster Polar Alignments are sub-standard. Last night I had 3 attempts that gave different locations for the NCP. In the past I used to single PAs but they seemed not to be accurate. So I went to a minimum of 2 and often 3. The NCP was sbtantially different. Not only that, using a different star for the mount's rotation gave a result that suggested the run failed. I have to set up my mount each night because of where I live. Therefore a good PA is essential. Don
  2. wetcoaster

    Master Dark subtracts too much noise?

    Thanks Alan. Interesting stuff. I noticed the XISF format. Here is a link to a 32bit FITS file. <https://www.dropbox.com/s/tok0tgm8bjtuxhg/Bubble O3 600 integration FITS.fit?dl=0> When you say "in the linear portion", that is the 20-80% range according to something I've read. I don't know if SharpCap's histogram for its Capture Flats function is showing the Full Well range. It does give a readout in ADUs. 28K is roughly 40% of the histogram but that was too bright. Your flats are real interesting. I had one that simply blew me away. My Nikkor Ai 600/5.6 ED lens can go to f/32. During my manhandling of it the f-stop ring wound up at f/32. I joked with my frineds that I now knew how to find out if there was dust in a lens! It looked like something blasted by shotgun with fine pellets..... It also showed something very close to the sensor and a quick look confirmed that was so. I had a better capture of the Bubble last night with Oiii. It appears my star bloating could be caused by over exposure! I cut the gain to 150 from 200 and ran 5 minute exposures. The subs looked a lot better. I intend to process them shortly. Don
  3. wetcoaster

    Master Dark subtracts too much noise?

    Here are the links. <https://www.dropbox.com/s/hxapx9k20u0dok6/00_18_21 Master Dark 300s g200.fits?dl=0> <https://www.dropbox.com/s/91d35hdkc3ipr89/Bubble O3 600 integration.xisf?dl=0> Don
  4. wetcoaster

    Master Dark subtracts too much noise?

    First off, thanks for the comments. On to the answers. I don't use flats because the ones I captured with electro luminessence panel gave me terrible over-correction. I use Sharpcap which gives gives a readout of ADUs. I found suggestions from the web to use 28k ADUs, low 40s in % of histogram and half of Full Well. The first two gave roughly the same outcomes but the tjhird option was different. ASI1600's Full Well is 20ke. That meant if 20ke = 20k ADUs, I should use 10k ADUs. That gave totally different results but no solution.The most common was the outer edges of the image were much brighter than the centre For reasons I do not understand, my Oiii captures have what looks similar to an Infrared hotspot (for those of you who shoot terrestrial IR like I do, i.e., central bright spot). The stars are always brighter with Oiii than for Hα. Focus problem? The amp glow is in the upper left, lower left, and lower right corners. That is when the camera is oriented with the USB port at the 12 o'clock position. 300 seconds, gain 200. I do not use "optimized" darks in PIS. I don't knowingly use scaling. I am trying to use darks captured in exactly the same environment as the lights. However, in most cases I have captured them with the camera only but the master dark I will provide was captured with the lens covered by a faux black leather bag. I also used black electrical tape to cover the opening of my ZWO manual filter wheel. Regarding max temperature cooling range, I have run into the limits of the cooling range once in a while and was limited to -18.5°C. Last night it was 7°C outdoors so there was no problem achieving -20°C. I will post that dark on DropBox and provide a link here. I'll also upload the integrated image, unstretched, 6nm Astronomik Oiii filter, used with a Nikkor Ai 600/5.6 ED lens at f/5.6. It's a stack of 22 subs, 300s, gain 200. Sky was clear but light pollution limited the SQM reading to 18.9. Good seeing and transparency according to the Clear Sky Chart. Narrowband is an adventure (translation - numerous problems for a new guy to overcome).
  5. I am using an ASI1600MM Pro. I live on the edge of a red zone known as Vancouver, As a consequence I use 6nm narrowband filters for Hα, Oiii and Sii. I shoot 5 min subs at gain = 200. Cooled temp is -20C. Earlier this week I captured the Bubble in Hα using those settings. I processed them in Pixinsight using a master dark created indoors. but at sensor temp - 20C. When I calibrated the subs using that master dark, aligned and stacked them, the integrated image showed the outer edges lighter than the core. That suggests to me that the master dark subtracted too much "noise". My question is - should I take those subs in a cooler ambient temperature? Or is there another explanation?
  6. I have an unusual situation in that I use an iEQ45 on a pier at my dark sky cottage for 3 months each summer. However I live in a townhouse complex with limited space for setup and it's under light polluted city skies. I also spend 2 months each winter in California at a timeshare resort which means I have to cart my gear from my unit to a place on the far side of the resort property. I use and like a Star Adventurer for my home and California. But I need a portable GoTo mount for my next project which is galaxies using an Altair Hypercam 174. That has a small Field Of View and finding galaxies is difficult unless they are near a bright star. So I'd like a Grab 'n' Go GoTo EQ mount. One option is to just forget about it but I am wondering if the latest S/W EQ3 Synscan GPS is sturdy enough and tracks well enough to handle an FD 300mm f/2.8 Canon lens or Nikkor AI 600/5.6 with the H174 which would make it close to a 5 KG load at worst. I will Autoguide using a StarShoot guider and Polar Align with a PoleMaster. I have tried to find User Reviews in Canada and the US but no US dealer carries the EQ3 and the handful of Canadian dealers who do, don't show any reviews. Googling was unproductive as well. I am hoping someone here has experience with the EQ3 and can offer advice.
  7. Amen to your first comment. Much of my work is with really wide angle lenses ranging from 14mm through 35mm. I have some nifty captures of the Orion Complex that I still haven't edited to my satisfaction. But I am hopeful that what I have recently learned will make a difference when I go back to it. I haven't tried multiple passes of ABE and will do so. Given how wide angle my shots are I find cropping is the best way. The problem with this image is that the two primary nebulas are near the edges of the FOV. With DBE, I find that the samples often don't get put in the area that needs fixing. In this case, the right side of the image. I bumped up the samples per row to 40 and even higher and it still din't cover the image as expected. Don
  8. Thanks Wim. I try to use Pixinsight but relying solely on it means missing the lens corrections for example. And I have found that ImagesPlus has a couple of features that are superior to what I can do in PI. Star size reduction and removing halos around stars are examples of that. perhaps PI can do them well but I haven't been able to find the tool that works for me. I have tried dozens of parameter combinations if DBE with limited success most of the time when I really need it, like for this image. It's trial and error non-stop. Don
  9. Thanks for looking at my problem William. I used a Canon EF 100/2.8 USN Macro lens at f/3.5. I do not use darks and flats. My Canon 6D has no dark current problems and is very low noise. In fact, noise is never an issue with my imaging. As for flats, I tried to create them for some of my lenses but it went badly. I now use the lens correction functions in PhotoShop and LightRoom. I can also use Canon DPP as well. The CLS filter for full frame often creates a shadow on the bottom of the frame. At one time I had problems with it loosening but after chatting with Gerd Neumann, I bent the frame a bit and it now remains seated. There are no hot pixels, just blown out stars. Here is a Dropbox link to the PI Integration image <https://www.dropbox.com/s/y9bsiw2rjhjyrjz/160928 integration ET%2BNA v1.tif?dl=0> I received some good advice in the digital_astro Yahoo group and will use that to correct later captures. However, I have decided to leave this one be because it is never going to look good enough to publish. I did a series of 3 tests using my 6D with and without the CLS filter, and my A7R with a Hutech LPS-V4 clip in filter (it works but vignettes). All runs were taken with the 100/2.8 macro lens at f/3.5. I went after the area around Deneb and Sadr so captured a number of red emission nebulas. The filtered images turned out reasonably good but the unfiltered one is not so great. I used the editing process championed by Roger Clark (clarkvision.com) but didn't get the results he achieved. That may be due to his superior editing skills although I used his recipe. Don
  10. I've moved your post to the Imaging > Image processing forum where you'll probably get more replies.

    1. wetcoaster

      wetcoaster

      Thanks. I also forgot to ask to be notified. I'm not very skilled at finding things on the web site.

  11. I live in a light polluted urban area near Vancouver BC. Sky Quality Meter readings are typically 18.8 versus the stellar 21.5 that I get at my cottage. The best SQM reading possible is 22 by the way. I have been trying to image portions of the Milky Way. I used an Astronomik City Light Suppression filter. I pre-processed in LightRoom to apply lens corrections and a few other small edits. Then I aligned and stacked in Pixinsight and followed up with Dynamic Background Extraction and MaskedTransfer. What I got looks like a badly designed quilt. See attached. Since then I have tried to use HistogramTransformation to balance the colours but without success. I finally painstakingly edited the image in PhotoShop CC and managed to get a so-so image. I am wondering if there is some tool or technique that will colour balance this image. Or if it is Mission Impossible. The CLS filter chops out around 100nm of the visible spectrum. BY the way, I have used a Custom WB on occasion but the problem will not go away. Don
  12. wetcoaster

    Width of LVI Smartguider 2 eyepiece spacer ring

    Final post on this problem. I arrived back home last night and today I used a 12.5mm eyepiece with the ZWO guidescope focused at a point where the camera can find stars. I was able to adjust the setback of the eyepiece till a distant tree came into focus. I am now very confident that that the Smartguider 2 can find a suitable star. Now all it needs is tuning for the right guiding parameters.
  13. wetcoaster

    Width of LVI Smartguider 2 eyepiece spacer ring

    Sometimes perseverence is stubborness. It felt that way to me a few times.... Don
  14. wetcoaster

    Width of LVI Smartguider 2 eyepiece spacer ring

    Well the sky cleared around 1900hrs which was a surprise. I set up and tested the LVI SG2. The focus point setting from last night's test was almost bang on. A slight adjustment and the SG2 reported Star Found. I could not see anything through the eyepiece so wasn't sure that a star was in the field of view. I will use a 12mm e-p after I get back home on Monday. I calibrated and then started guiding. The graphs looked reasonable. I wasn't pointing at anything interesting. I selected Schedar because there are several stars around it. I won't have any time to do further testing before I take off for home. Don
  15. wetcoaster

    Width of LVI Smartguider 2 eyepiece spacer ring

    I started to run a comparison of my ZWO g-scope and a Skywatcher finderscope tonight basically to check how good the ZWO is. To make a long story short I switched to testing the SG2 on a yard light 300+ meters down the hill. In just a few seconds it found the light. Ironically I didn't verify the set back distance of the 6mm eyepiece - I just eyeballed it. I focused and switched the SG2 for the e-p. The most noteworthy aspect is that the focus point on the focuser is over 1cm from where the 6mm e-p is in focus on a star. I know there might be a slight change in focus when going after a star but it should not be much. This result suggests that the e-p might be a piece of crap. After I get back home on Monday I will go out on the first clear night and try out my decent lighted reticle 12mm e-p. I still need to centre the star so can't just leave the SG2 in the ZWO scope. While I'm not there yet, this is the first hopeful sign in a long time. Don
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