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eshy76

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Everything posted by eshy76

  1. Thank you very much! Something to devour this weekend!
  2. I hear you! The basic theory is that each sub should be long enough to drown out the read noise and with the really low read noise of CMOS cameras, that level is reached quickly with light pollution. Of course you can shoot longer than that for practicality, but if subs are too long, stars and highlights could get saturated. That is it in words - there are mathematical formula that try to calculate the optimal sub lengths! Those cameras have really good reputations - I was looking at a 071, but ended up getting a 294, which I'm still learning. I think the 071 has an APS-C sensor? Thank you for the kind words!
  3. Thank you - that sounds interesting - I like the theory side of things as a guideline to what I do! And I did not know that about Sharpcap...I've got the pro version for the polar alignment routine, but have been using APT for capture.
  4. Thank you! That is the golden question which I intend to find the answer to - with my level of light pollution, 15 secs at unity gain on my camera is more than enough for my Lum subs to drown out the read noise...so I've always used that sub length... ...which was fine for 200-300 subs, but this project really brought home the impracticality of stacking 1000+ subs. I just was thinking in terms of total Lum integration time (250 mins) and set the number of subs that way. As far as I am aware, SNR benefits of stacking enter the realm of diminishing returns from about 200 subs onwards...so going forwards I'm going to lower the gain from unity (139 on the ASI1600) to 76 or 0 to try and get sub length up to between 30s and 60s and hopefully more like 200-400 subs to stack. I can then answer your question fully. The 15sec approach benefits in terms of guiding being less critical, and things like clouds or planes or satellites not meaning minutes of data being binned. The Lum integration WAS beautifully smooth at least!
  5. Thanks! Yes - an incredible part of space. There is a tiny barred spiral in the bottom middle of the image which is just beautiful and perfectly formed...I'll focus on that one one day when I have some more focal length!
  6. Thank you! Yes indeed...so while I got, erm, stacking benefits, the practical side was an issue in terms of the time it took to stack on a good PC. I also didn't dare drizzle the integration - that might have taken 2 days!
  7. Hi everyone, This is Markarian's Chain shot from my back garden over three nights in late March. Probably the deepest single image I've taken in terms of integration time...which leaves me feeling my processing is not quite doing the data justice...maybe I'll come back to it. In any case, this is an incredible part of space; looking away from our galaxy reveals countless others! The crazy number of Lum subs took a whole day for APP to chug through and so I've resolved to lower the gain from unity going forwards to get more manageable sub lengths than 15 seconds! L: 1050 (!) x 15s R: 92 x 60s G: 165 x 30s B 165 x 30s....total integration time 8.2 hours. Captured using APT, stacked in APP and processed in Pixinsight. Thanks for looking! Edit: Link to higher res version
  8. From left to right - 1. Minix mini-PC - this runs all my imaging and guiding. I remote into it using an iPad via the little white travel router on top 2. Bottom - yes a lithium ion battery for the dew heater 3. On top of the battery is a Lacerta dew heater controller which measures the ambient temperature to regulate my dew heater. I velcro all this to a dovetail which is bolted onto the scope rings...I've since moved to a lighter dovetail, as the one in the picture was unnecessarily heavy. Next stop is to shorten as many of the cables as I can....
  9. Thanks for the clarification - when I said I wasn't scientific in PHD2, I mean I still tweaked the more "obvious" settings...but I haven't spent an evening fine-tuning all the settings to perfection for example! Here is a picture of my rig:
  10. Polar aligning with a Polemaster and using an OAG, I average between 0.5"-1" (pixels right? The number in brackets on PHD2). I've seen better guiding than that but not often. This could also be due to having the wrong settings in PHD2...I've not been that scientific with it.
  11. I would add a yes to this, I've had mine for a year and have been using it with a William Optics Z73 to great effect. I think it is hard to beat in terms of performance vs. weight vs. cost, if you are looking for a portable or beginner mount, as I was. You can see images from the setup from the Astrobin link in my signature...most of the pictures are with the CEM25P. Autoguiding is a must, though, 45 seconds was the most I could bear unguided, although I've seen some people get amazing results with 2 minute subs. Seems robust - used it in winter temperatures of -5C and also took it with me to Mauritius last year (I live in the UK).
  12. This was single shot taken with a Samsung S8 (Android) on my father in law's rooftop in Vacoas, Mauritius on April 18th. I was facing East/North East and was mesmerized by seeing Orion "on its side" for a Northern Hemisphere dweller such as my myself. No processing, just straight from the phone. The mountain is Corp de Gardes and was 3 miles away. Also visible are Castor and Pollux and I think also Alhena. I was imaging the Carina nebula when taking this...thanks!
  13. Hi everyone! I was lucky enough to spend Easter in Mauritius and managed to get a night of imaging in despite the tropical night time clouds! As someone who lives in the Northern hemisphere, the Carina nebula has always been a target I've coveted, but during my holiday, I also loved Crux as prominent constellation in the Southern sky. So when I ran into polar alignment issues with my Skyguider Pro, I decided to play it safe and go for a wider field, capturing both those targets rather than focusing purely on Carina as was my original goal. This was shot from my father in law's rooftop in Bonne Terre, Vacoas, Mauritius and my basic polar alignment meant significant field rotation, but I still got some usable data. Cropped, processed and finally upsampled. Data was shot at f/2.8 with a 50mm lens, unguided on an unmodified Sony a6500. 174 lights at 30 secs each = 1.4 hours of integration. Bortle 5. From the colours it looks like these objects sit right on the disc of the Milky Way and I know there is more in the picture I haven't mentioned! Thanks for looking!
  14. Thanks for this comprehensive review - I've had the same scope for a year and I love it! The only fault I found was an inconveniently placed focus lock screw which means I need to turn the scope upside down if I need the dovetail to extend beyond the focuser for balance. Very minor issue. Also would have been nice if the rotator was marked for degrees...available as a £200 extra!
  15. Hi there...I managed to get a rudimentary shot of this amazing target when on holiday last year in Mauritius (southern hemisphere) where Antares is high in the sky with all the planets! But in your case, a tool you can use is the Telescopius site (formerly dso-browser). Once you've clicked on a target, you can choose to see its transit for the current night or "monthly" at a certain time like 10pm - the latter shows the altitude of the target throughout the year - I think Rho peaked very low (15 degrees) around July to August in the Northern hemisphere. I hope this helps! Edit: I just checked the site - I searched for IC 4604 and at 11pm it peaks on June 28th at 15 degrees altitude looking from my location of Surrey. Good luck with it!
  16. My L subs are 15 seconds, G and B are 30 seconds and R subs are 60 seconds. With my filters, my R needs longer to get the same ADU as G and B. The formula I used was Jon Rista's: Minimum ADU per sub = ((20 x read noise/gain in electrons)+(bias offset)) x 16 So at unity gain, associated read noise of 1.8e- and using offset of 50 that would be: ((20x1.8/1)+50)x16 = 1376 The 16 multiplier is to gross up from the 12 bits of the ASI1600 to 16 bits which is displayed in SGP etc. The 20 x read noise can also be 3 x read noise squared or 10 x read noise squared....there's some discussion about that. It's a starting point as you say! My skies are light polluted which is why my subs are so short!
  17. No probs - I forgot to mention I'm using an f5.9 scope - as vlaiv says there are lots of factors to take into consideration.... ...but if there is one thing I am aiming for - it is a certain level of median background ADU per sub (you can see this in your capture software or Pixinsight). Based on my use of unity gain (139), default bias offset (50) and the associated read noise of the camera at unity (1.8 e-), the theoretical minimum median ADU I need per sub is about 1400 to swamp the read noise (by about 20x). You'll see this in the CN thread I mentioned. That number of 1400 (for me) governs the length of the subs I mentioned....the R, G and B sub lengths get me in the 1500-1700 ADU range...the 15 second L sub actually delivers about 2500 ADU on average, more than I would want, but I can't really go much shorter than 15 seconds from a practicality perspective. So I didn't just pluck those numbers out of thin air in case you were wondering! The theoretical stuff is a nice baseline for me to hang my hat on and know I am being efficient - not under or over exposing, although there is some leeway on the latter. Ultimately, this low-noise camera allows you to take shorter subs and use stacking and sigma rejection benefits, but there's a trade off between being efficient and practicality (hard disk space as you'll need a lot of subs using my approach) and also your own preference on whether you would like deeper individual subs. Good luck with it!
  18. Hi there, I have an ASI1600 - this will depend on your local light pollution. Where I live is Bortle 7-8 and I shoot 15 second L subs, 30 second G and B subs and 60 second R subs. As far as I understand, your exposure time for each sub should be enough to swamp the read noise of the camera...and then focus on total integration time. So I get lots of subs, but am still imaging for 1-2 hours for each filter basically (more for L). If you have darker skies than me, those sub times will be longer for you. I also keep things simple in terms of proportions of integration time - I shoot 50% L and 50% RGB. I'm not sure if I can link to other sites here, but if you google "sub exposure time ASI1600", there's a great thread on CN that answers your exact question with tables of exposure time depending on different sky levels. It's an involved thread, so you can dive into all the maths or just stick to the tables in the first post. I hope this helps!
  19. Hi Ian, I really love mine, but it's my first and only mount, so bear that in mind! It is reliable, tracks well, guides at about 1" RMS consistently, but when I've polar aligned well and reduced the payload, I've guided at 0.4". Nice polar scope, easy to set up, works well with ascom. Above all it does this while being light - when I bought it I was carrying my stuff down stairs and then another 50 metres to set up and back again every time...I needed a truly portable mount and the CEM25P did that perfectly...a great combination of portability, decent performance and low price. My Astrobin pictures (see my signature) are nearly all using the mount, so you can see for yourself. The only issue I had was some play in DEC which, as a newbie, I did not detect for a few months...I fixed it with a shim...but not ideal - QC might be an issue. I'd definitely buy iOptron again although the beautiful CEM40 might not be enough of a payload upgrade for me! Hope this helps!
  20. Thanks for posting that info... permanent pec, payload capacity of 18kg, ipolar scope which does not need Polaris and through mount cabling of sorts. If I didn't have a CEM25P I'd be all over this!
  21. Not sure if this is still the case - I am able to RDP into my mini PC (W10 Pro) with my desktop (W10 home), iPad and Android phone, the latter two using the free RDP apps. For me just the scopeside PC needs to be W10 Pro for RDP to work.
  22. Well that does look rather nice...colour me interested...built in polemaster, no dec cable, simple switches instead of clutch release thingies...price and payload will be key. I have the CEM25P which has been pretty good for me...but is payload limited for imaging...
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