eshy76

Just like in PI, APP (Astro Pixel Processor), allows you to weight subs by quality, including FWHM, when stacking. There is even a control to choose the percentage of subs to stack, so if you think that 10% of your subs are potentially bad, you would select 90% and would get the best 90% subs weighted by quality. This is a faster process than PI I find, as it's two settings then click, but you can always inspect the sub stats after weighting and manually remove ones you don't want in the same way if you wish. In your position that's the approach I would take and see if I was happy with the result.

All very sensible tips here. I would just add that I don't really use those exposure tables for exposure time per se - I used the underlying maths to work out what ADU I should, theoretically, be aiming for per sub. So at unity gain and default offset, the maths chucks out a minimum ADU per sub for me of about 1400. You can then use the readout in your capture software to judge the right exposure times. It's a one-time thing unless you image in different places with different skies. So I aim for this when judging exposure time, which is dependent on light pollution. With my bortle 7-8 skies this works out for me at about 30-60 seconds for RGB subs (much less for Lum) and 300 seconds for narrowband subs. Results seem good, which is, of course, the acid test!

Another vote for unity gain (139) to start off with. I've had the Pro version for nearly a year and it is only now that I am experimenting with other gain settings. As you say, the move from DSLR has many different aspects to it without complicating it by fiddling with the default gain which will give you great all round results as mentioned above. That sub exposure table/thread is a good place to start to judge sub length. Good luck! It's a great cam!

Hi everyone - it's been a while! This has been on my hard drive for almost 2 months and I finally got round to processing it...it was quite optimistic of me to try and image this from my Bortle 7-8 back garden, but I gave it a go! While the nebula itself is clear to see, all those gorgeous dust clouds surrounding it were extremely hard for me to capture from my location without a lot more integration time. I think I'll head to dark skies to capture this one next time, along with some more focal length! LRGB shot with ASI1600MM Pro and WO Z73. 2.9 hours of integration time. Full details here. Thanks for looking!

Hi there - Yoddha has been super helpful in addressing any problems I have had with APT...he helped me with the Platesolve2 approach I've settled on...I haven't really felt the need to go to blind solving yet.

Hi there - I also have not been able to get blindsolve to work in APT...so I just stopped trying. I just use Platesolve2 instead. My workflow is: 1. Turn everything on - usually my mount is in zero position here 2. Slew away from Polaris (apparently platesolving can go haywire at the pole) - I usually use the simple GoTo function in APT to pick an object for this or Cartes du Ciel - do not worry if the slew is inaccurate, you are just trying to get away from Polaris 3. Hit "Shoot" to take an image - 10 second exposure or so should be fine 4. I then click on Pointcraft and then on "Scope position" which populates the coordinates the scope thinks it's at. Then I hit "Solve" Within about 20 seconds this is successful on the first attempt and I then hit "Sync" to make sure APT is dialled in - all the Goto++ functionality works perfectly after that and subsequent "Solves" are usually successful within 10 seconds. The only step which might be superfluous is the "Scope pos" bit, you might be able to hit "Solve" directly after the initial slew. I'd love to get blindsolving working, but the above method has been foolproof for me, and given the blind solve takes longer as it's solving more of the sky I believe, I'm not sure it would necessarily be faster. Hope this helps!

Congratulations to the winners for some stunning images. This was a fun challenge!

Hi Mark - I got 2.4 hours of integration time over three nights, 89x75s at ISO400 at 135mm and 6x300s at ISO800 at 430mm. APP put it all together easily - I think the lack of noise is due to 1. Antares being overhead in Mauritius away from light pollution 2. Using dithering 3. Using quality weighted subs when stacking in APP 4. Processing technique - I used TGV Denoise and MMT in PI, with bright masks. Hope that helps. Here is a link to the higher res version: https://www.astrobin.com/356347/C/?nc=user

Mark's great pic has inspired me to post mine. Shame I only had a stock DSLR but lucky I had the Lacerta MGen to rescue my haphazard Southern Hemisphere polar alignment!

Wow Mark - I just saw this - fantastic shot! Congratulations!

Hi Steve - yes that's exactly it - Tools/APT Settings. Once you plug in figures for gain per filter (and autofocus offsets if applicable) in the dialog in your screenshot, whenever you select the filter in an imaging plan, the same gain/focus offset will be brought into the plan...very convenient once you've settled on what you want to use.

Hi there - I'm on a pretty recent Ascom version, maybe not the latest one....however, the answer is in the post above this one. When I set up my filter wheel, I use APT's settings, not the Ascom settings, so Tools/APT Settings as specified by Steve. That should work.

Hi there - do you have the latest version of APT? I believe the gain per filter was only recently added. I have version 3.63. APT is not updated within the program - you have to download and install the new version over the old one. Settings survive that process! That would be my best guess.

Thank you Alan - yes, I collected the data pretty much as a side project to the tadpole/flaming star mosaic I was working on. It wasn't one of my primary targets for the winter - I was also after M45 and the Horsehead - so the data just got forgotten. But processing the clean narrowband data was a pleasure and NGC 281 itself surprised me with its pillars of dust and the little star cluster at its heart. It's a beautiful object in its own right, which I realised when I zoomed in.

And here's the original field of view

Hi everyone, This has been on my hard drive for some months, so nice to have finally got round to processing it! Shot over several nights in January in my back garden. NGC 281, also known casually as the Pacman Nebula, is a bright emission nebula and part of an H II region in the northern constellation of Cassiopeia and is part of the Milky Way's Perseus Spiral Arm. It lies about 9,500 light years from us and is 48 light years across. As the final version, I've gone for a crop, which I think holds up well, though I'll include the wider fov version in the next post. I used a more natural colour blend for this image: R = 76%*Ha + 24%*SII G = 100%*OIII B = 85%*OIII + 15%*Ha For some reason, I was not expecting much from this image, but the result looks like it will be one of my favourites...the narrowband data was really good! Captured using APT, stacked using APP and processed in Pixinsight. 5.4 hours integration time. Link to full details and higher res version. Thanks for looking!

Yep done that one too....one to add to the slapstick astro mess ups...though not as bad as taking 20 mins to realize that the cap was still on my polemaster once...the hot pixels looked like stars on the ipad screen...it took me time to figure out why they weren't moving when I rotated the RA axis....!

The way it works is that if you put a gain number in the little box on the camera tab, that will override whatever was in the Ascom driver pop up, for a single shot and for an imaging plan - *if* you haven't assigned a gain to each filter in settings. In APT's settings when you set up your filter wheel, you can add a couple of things per filter which are useful as defaults for every time each filter is used - (1) the focus offset, if you are using autofocus and (2) the gain. So I tend have 139 assigned to LRGB filters and 200 for narrowband filters for example. I then leave the little box on the camera tab blank to make sure it doesn't override the filter wheel settings I put in when an imaging plan starts. It works perfectly for me....APT's scripting is pretty powerful...I also used it to platesolve to another target (Goto++) and restart PHD guiding in the same night...worked fine. Glad it's working for you now!

Hi there - this seems very odd - I have the same camera and also use APT, and I'm pretty sure the gain can be set higher than 100. I tend to use 139.... My first reaction to your post is that you might not have the right driver selected in APT....to check, click on the "Settings" button next to the camera name at the bottom of the APT screen...then make sure the ASI-1600 is selected specifically from the driver drop down menu in the Ascom screen that pops up. Personally I tend to set the gain using the Ascom driver (in the same "Settings" pop up) and leave the gain setting blank in APT itself - this is because in my filter wheel setup, I have a different gain associated with each filter and I don't want that overridden by the manual gain setting on the camera screen. Let me know if you need me to explain the above more clearly...happy to help!

Yep another vote for SkySafari...has been my invaluable companion on imaging/observing nights in both the Northern and Southern Hemispheres. I also prefer its forward and backward time controls compared to the swiping in Stellarium (which is also a very good app).

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!

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!

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!

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!

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!