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eshy76

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About eshy76

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    Nebula

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    Sutton, Surrey, UK
  1. Hi everyone, A bit of an odd one aspect ratio wise, but fun to put together - first light for my new ASI294MC OSC and technically my first experimental attempt at a mosaic! My first stab at using the camera meant I went for 30 second subs, I need to experiment more to settle on my ideal sub length...still, the results are decent for a low integration time of 1.7 hours. I love the Orion constellation and if I had the skies and time, I would mosaic the whole thing, but failing that, I can do bits and pieces! Orion's Belt is amazing to me, the three stars, Alnitak, Alnilam and Mintaka, very distinctive in the night sky. Full details on Astrobin. Thanks for looking!
  2. 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!
  3. 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!
  4. 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!
  5. 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!
  6. Hi Billy - I use different LRGB filters to yours, but I also have the ASI1600. For me in Surrey (Bortle 7-8), I use exposure times of 30 seconds for G and B and 60 seconds for R. That is at Unity gain (139). These get me to about 1500-1700 ADU (on a 16-bit basis) per sub per filter - I have to expose twice as long for the R filter to get the same ADU per sub. My approach is dithered shorter subs (needed due to light pollution) and lots of them for stacking. Or for your problem - I expose for half the time with G and B as the subs saturate faster with those filters. To rule out over saturation, you certainly try lower exposure times for G and B - what kind of ADU are you getting per sub and what is your gain? Assuming you are using the default bias offset of 50, then the maths suggest you should be able to drown out the read noise at unity gain with subs with background as low as 1400 ADU - you can judge your exposure time based off that as a lower limit and your own level of light pollution. I hope this helps!
  7. Hi Graham - if you've cracked platesolving that helps a lot - I think lining things up is half the battle with mosaics! Some of my comments were after some trial and error, so hopefully you can benefit from that. I think mosaics are one of those things that make sense once you attempt one - common sense will get you there! Just ensure there's some overlap of at least 10% between the panes and the software should be able to figure it out! Happy to answer any more questions, including with APT - I really like Ivo (Yoddha) - he's helped me a lot and I know a mosaic planner is on his list of updates, now that the auto meridian flip has been added!
  8. 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!
  9. Thanks Barry! Yep, as if this hobby wasn't challenging enough, why not go for mosaics?! I love your images, so your comments mean a lot!
  10. Thank you for the kind words - I consciously went for a lighter touch on this project!
  11. Hi Graham, Thank you for the kind words! In terms of tips and tricks, this was my broad approach for this mosaic: 1. I used dso-browser.com to plan the mosaic - you can enter your optics and it shows your field of view for any object and you can easily add mosaic panes. You can also view the coordinates for the centre of each pane - but be careful, the correct coordinates did not appear correctly on the mobile version for me, but did on the iPad/desktop version of the site. 2. Plug in the coordinates to APT's Pointcraft Go++ for each pane and you should be good to go - of course pay attention to your orientation. Also observe the first few frames to make sure you're pointed right - in mine above, the first few shots of pane 2 were slightly too far left (West?), so I used the Aim function in Pointcraft to choose the desired centre spot for the second pane - the central large stars were common to both panes so I knew there was some overlap there. Finally, when you are happy that APT has dialled in the right coordinates for each pane, "Store" them as custom objects from Pointcraft - crucial if you want to add data at later dates as you can select them directly for platesolving. 3. In terms of pre-processing and stacking, I first stacked each pane by filter separately (including flats, darks, dark flats), so Ha pane 1, Ha pane 2, OIII pane 1...etc. I then used the excellent APP to stitch the mosaic together for each filter, so Ha pane 1 + Ha pane 2, etc, so I ended up with three mosaics. Finally I moved all 3 images to Pixinsight, registered them and cropped all 3 using dynamic crop. After that it's process to taste! I hope this sheds some light - of course I'm sure other tools can be used for the things I've mentioned and SGP has the mosaic planner built in...but I like APT!
  12. Hi everyone! The Tadpole Nebula and the Flaming Star Nebula captured over three nights of the unexpected nice weather we had a couple of weeks ago. A number of firsts with this image: 1. My first mosaic - keeping it simple with two panes! 2. First time I left my imaging rig outside... (I used a telegizmo cover) and it was perfect, allowing me to get imaging very quickly on each night 3. First time using powerful scripting tools in my capture software, APT, to move to the second pane and starting imaging automatically...worked really well! APP was used for pre-processing and stitching the mosaic together, while Pixinsight was used for image processing. A total of 10.9 hours integration time. Full details on Astrobin Thanks for looking!
  13. 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.
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