Xiga

Lovely M101. Nice subtle processing and not overdone on the colours.

I've been sitting on some data of this myself. Struggling to find the time to process it though. Hopefully soon! 

Just to echo my comment over on AB, this really is an amazing image Richard. From dark dust to bright reflection nebula, it makes for a very well composed mosaic with a bit of everything in it. 

I've recently started dabbling a bit with Pixinsight. It's early days, but I can certainly see the benefit of it (if not the fun!). Do you mind me asking, what processes do you usually use on your images? I know you stack in APP and finish in PS, just curious which parts you use P.I for.

3 hours ago, wimvb said:

I use the blink process to weed among images. Then I let subframe selector assign a weight to each image, deprnding on star fwhm and eccentricity. I do this for lum but seldom for rgb. Seems to work well.

Thanks Wim. 

I currently use APP for stacking and gradient reduction. I really like it for this purpose so I don't plan on changing that. Once I get a handle on Blink and SFS I'll likely just use them to identify which subs to exclude all together, before I then stack in APP. 

Very nice Wim. Lots of fine detail in the core there. 

I'm also working on M101 at the moment. Managed to get 3 hrs of RGB and a bunch of Lum this past week. I still need to sift through all the Lum files though (of which there are many, one thing i'm not exactly enjoying about CMOS imaging) as i know quite a few won't make the grade. This will be my first proper LRGB image, and i've been dipping my toe into Pixinsight for the first time. Not exactly loving it yet tbh, but i'm going to persist as i think it will be useful, if even just for a few processes. 

6 hours ago, Allinthehead said:

Would we see it vary over that short time? Might be worth a shot. How would I go about checking?

Did a little research. Yeah it wouldn't show it in such a short period of time. Turns out you would need to have some subs (though not many) taken every day (or every 2 or 3) for a month at least. The longer the better obviously, but if you managed a few months then you'd have a good chance of making a cool animation showing some ripples and maybe even some movement of dark dust. So not very likely to happen, given our skies, but still pretty cool stuff 😃

1 hour ago, Allinthehead said:

Thanks Ciarán much appreciated. I've been quiet here too lately. Work is hectic and imaging conditions have been poor.

It's been quite the winter of discontent as far as trying to get any AP done, hasn't it?! I think i've manged 2 'attempts' since September, neither of which were particularly fruitful. You do have to wonder if we are all a bit mad, taking up a hobby that you can't actually do 99% of the time 😅 🤨 😐 😑

ps - Cool to see Hubble's Variable in there. Have you tried blinking your subs to see if you caught any slight ripples? Maybe 4.5 hrs isn't a long enough period of time, but it could be fun to check. 

On 06/02/2022 at 12:41, Allinthehead said:

Hi all. The fruits of Friday nights clear sky. This image is the first pane of a planned 3 panel mosaic, hopefully I have time to finish it this year.

4.5 hours rgb in 180 second subs at gain 0 with the Asi2600mc through my Tak Epsilon 160ed, mounted on my AzEq6

I had a little Ha from a few years ago which I added in, unfortunately it didn't cover this FOV so I added it selectively to the cone area mainly.

Processed in APP, PI and PS

Richard.

Added Ha 

That Ha Added version is sumptuous Richard! The mix of Ha, Reflection Nebula, and beautifully processed stars makes for a really great image.

Ps - Congrats on the IOTD on Astrobin btw! I haven't been that active on the forums lately, but it popped up on my phone this morning on the AB App 🙂

On 15/02/2022 at 16:37, osbourne one-nil said:

Ah -  someone else has suggested drizzling to me so I shall watch a few Youtube videos on it tonight. Thanks!

I've got mine set up with a big old Losmandy plate on the back which carries my 50mm guide scope and the ASIair Pro, but even with it all rigged out, it's still weighing in at less than 10kg. I'm tempted to go down the OSG route to keep the weight down but that's more for my benefit than the mount's.. The SXD2 is rated for 15kg but I think that's a very conservative minimum, knowing Japanese manufacturers. 

Very nice. Yours is certainly a lot shinier than mine i must say! lol. 

I can see a red thumb screw at the Primary end. Did yours come with these or did you replace them? 

I think that looks great Adam. So much dust to see in this part of Orion, and because it's so bright it doesn't need that much exposure. 

I had noticed you'd been quiet lately, although i know all too well just how bad the weather's been here these last few months. 

Looking forward to the big 12 panel mosaic now! 

2 hours ago, osbourne one-nil said:

Nice! I don't quite get Vixen's relatively low-key profile. Perhaps they don't cost enough? Make them Takahashi prices and you're on to a winner!

I think my scope is about 8 years old but I like it so much I am almost tempted to buy a brand new one for imaging and retire my current one for visual with my lad. I've got a Coma Corrector 3 which seems to cover my relatively small sensor well enough, but I reckon if I do get the extender, then I'd probably stick with that most of the time because if I want wide-field I have an Askar FRA400. 

Is "downsampling in post" the same as processing as Vlaiv recommends?

The weight was a big plus point for me. I only have an HEQ5-Pro mount, and i need to set up each time, so the fact it only weighs 5.3Kg was the clincher for me. My one really is in need of some TLC. though. The mirror needs removed and given a good clean, and the primary collimation screws are starting to rust (although they still work, for now) so one of the most important jobs will be to find suitable replacement ones for those (and maybe even the secondary ones too). I'm hoping the screws are the same size as other more popular scopes, that way i might be able to get some Bobs Knobs. 

If i had an OSC camera, i would do things a little differently to Vlaiv's approach, although how much of a difference it would make i don't know. I would stack using 'Bayer Drizzle', as you are dithering and will have lots of subs due to the short sub length. Bayer Drizzle also doesn't do any interpolation. Then you can just resize the stack by 50% or do it in post (i.e when processing). If you have something like APP or P.I then you can re-sample using a good algorithm such as lancsoz-3 but if not then even just a bog standard re-size in PS would get the job done ok. 

After guiding for over 5 years with a finder-guider on my SW 80ed without any issues (and doing a lot of 20 min subs during that time) i've suddenly been beset with terrible differential flexure issues. After trying everything to fix it, without success, i've had to give in and just move to an OAG. After not being able to image anything in the last 5 months (as much due to the weather as well, never mind the DF) as luck would have it there was a brief period of clear skies last Thursday so i managed to get back on the horse and get some testing done. I've had the Qhy268m for almost a year now, and only managed one image in that time (a NB image) so up to now i hadn't actually captured any BB data. When i got the camera, i picked up some cheap SVBony LRGB filters, so this was also a good opportunity to test the Lum filter. I was pleased with how it worked. Obviously, there were no super bright stars in the field, but i was still happy with the star sizes in the subs, so fingers crossed it holds up ok in tougher circumstances. 

I picked M101 as a test, because i knew i had some colour data from an image i took a few years ago with my D5300, so the plan was to just capture Lum with the Qhy268m and use the D5300 data for the colour. Unfortunately the forecast didn't hold up anywhere close to how it was supposed to, so in the end i only managed 73 mins. Not enough for a serious image, but enough to satisfy myself that the OAG and backfocus were both ok. So all in all, it was a good session, and i'm pleased to know i'm now at least able to image once again (well, for the 1 clear night we seem to get every 2 months!). 

So just for kicks, and because it's been a long, barren 5 months, i decided to process the data anyway. 

Lum: 73 mins (73 * 60s), Qhy268m, SVBony 2" L. Mode 1, Gain 56, Offset 25, -10C. Bortle 5/6. 70% Moon. 

Colour: 2.5 hrs (26 * 360s), Nikon D5300, ISO 200, 2" IDAS-D1. Bortle 4. No Moon. 

SW80ed, HEQ5-Pro

Stacked in APP (Darks, Flats, Dark Flats). Processed in PS (reduced slightly to 90% size). 

Thanks for looking and CS 🙂

On 12/02/2022 at 15:05, osbourne one-nil said:

With galaxy season here, I would like to challenge myself to get some of the more elusive little blighters. I image with an ASI533MC Pro and I could use the RC6's long focal length (1350mm), but it's very slow at f9. I also have a Vixen R200SS (800mm f4) and Vixen do a focal extender specifically for that which would take it to 1120mm and still a reasonably fast f5.6. To me, that seems more sensible of the two.

My question is, would that give me any benefit over using the scope at its native 800mm focal length and simply cropping seeing as it would result in a resolution of 0.69"/pixel?

Great to hear from another R200SS owner! There aren't many of us out there it seems. Although i don't know why. Japanese optics, lightweight, and with the right accessories (Starizona Nexus, Vixen Coma Corrector, and Vixen Extender) it can effectively triple up as 3 different scopes. I picked up an old one (maybe from the mid noughties) last year for a very good price, with the idea of using it initially as a Galaxy scope. It's nowhere near ready for first light (probably won't be until next year tbh) but mine came with the old Vixen Extender which is F7.5 and 1,500mm, rather than the newer (and much better) F5.6 1,120mm one. I'm going to give it a go anyway and see what it can do. If it's no good, then i'll eventually add the newer Extender. My camera is a Qhy268m, so i'll be even more oversampled than yourself (about 0.52"), so i'll likely just downsample in post. 

Will be interested to see how you get on with your R200SS. Good luck! 

Congrats Adam! It's a great image, well worthy of the Apod 👋

And taken with a 130pds no less. Bravo! I just love it when people make great images with modest gear. Just goes to show that at least half this game is down to the skill of the operator. 

8 minutes ago, gorann said:

I would not say that the RASA stars are that bad unless you are a bad pixel peeper, but I had the same idea but someone beat me by an hour from buying Olly's old Tak 106😥

I agree Goran, the Rasa stars aren't that bad at all. I didn't mean to disparage them with my comment, but as Olly says, there is still a noticeable difference in quality when compared to a refractor. I've seen some incredible images taken with a Hyperstar + Tak combo where the Hyperstar captures all the dusty stuff and the Tak takes care of the stars.

You have 2 Rasa's don't you? Have you given any thought to trying out even a modest doublet on one of them, if even just as an experiment to see how well it would work? Rather than jumping in at the deep $$$ end with a Tak.  

What about a dual rig consisting of a Rasa and a Refractor. The Rasa gets the dust, the frac the stars. 🤔

Great image btw 👍

14 hours ago, vlaiv said:

Sometimes even x4.

I've posted M51 taken with that setup that is best sampled at x4 bin. That also goes for this image, for example - taken on a night of rather poor seeing:

Just look at the size of those stars - very bloated. I binned this x3 (it is something like 1500 x 1100px in size) while in reality, it is better suited for bin x4.

Hi Vlaiv

If you bin that high (x4) then you would end up with an image of only approximately 1100 X 800 pixels. Most imagers wouldn't be happy with such a small number of pixels, as the image won't fill the screen of a 1080p monitor, let alone allow for any level of zoom. 

If the tool is going to suggest a level of binning, I think it would be good if it clearly explains the number of pixels the camera is effectively reduced to, as most beginners probably won't know what binning is. And maybe a warning or such once the number of pixels goes below ~2m, the amount needed to display an image full screen at 1080p resolution.

Incredible amount of detail in the core you've captured there Rodd. Amazing what can be achieved with a 5" frac! 

Absolutely brilliant this, Dave. Especially that SHO version, which is right up my street. The colour palette is spot on if you ask me. 

@ollypenrice you didn't happen to re-install or upgrade Windows recently did you?

The last time I upgraded my version of Windows I too has difficulty with my images not looking right in PS. It turned out that my monitor's gamma just needed a small tweak, which I did using QuickGamma 

9 minutes ago, Stuart1971 said:

Thanks,

The moon was not out at this point…also I forgot to add I use an f5.3 scope, 450mm

I have  done the darks now, and will do the flats and dark flats tomorrow, but think I will get at least another 3 or 4 hours before I fully process….

I just wonder how much useable light the Idas P2 filter blocks, also i do get some vignetting and think it’s from the filter…🤔

Hi Stuart,

it's a very nice image indeed, and will look even better once you get the calibration frames done. 

If you're wondering why the nebulosity isn't popping more, it's entirely down to the Idas filter. It's certainly a very nice LP filter (i have a D1 one myself), but when it comes to shooting a narrowband target like the Heart Nebula, you would see a big improvement with one of the many Dual-band filters (such as the L-Extreme) that are popular right now. Then you will get a lot more contrast between the nebulosity and the sky background. 

1 hour ago, teoria_del_big_bang said:

I thought that was the case.

It was more the horrible halos that made me give up.
I will try another nights, whether it would be any better with less moon up or not I do not know ????

Your image on Astrobin is really nice, you have captured that OIII really well. I guess on mine there are some signs on the outer edges, maybe a bit longer exposure on OIII and more frames would add some nice detail so I must r=try at a later date (hopefully not too much later). I can deal with the halos in processing, a pain but would be worth it.

 

Steve

From my comment on AB, it seems that I shot my Oiii with a very bright moon up, so you should still do ok. I agree, I can see some showing at the outer edges on yours, and that's just a single 400s sub. Capture a few hrs and it will really show up. 

3 hours ago, teoria_del_big_bang said:

Okay, so far so good, clouds have not yet appeared so doing some Ha and SII on Jellyfish, not bothering with OII as there is so little there and giving massive halos on the two bright stars.
So I have come down in exposure time big time from my usual 10 minutes to 4.
Looking at the statistics in EKOS I am getting a mean  of 475, so that is pretty much in line with what @Xiga suggested was correct for this gain and offset, but the maximum is 65534. When I look in Pixinsight the two bright stars are maximum ADU before any stretching, so I take it there is nothing I can do about the brightest of stars in the data itself and I will have to take care of that in the processing, because even a slightly shorter exposure time is not going to significantly reduce those two stars, if at all. I guess some stars you just cannot stop from being over blown when imaging dim targets and have to deal with them later.
 

Steve

Hi Steve

There will always be some stars that clip (it's unavoidable to some extent) so it's just about making sure the number that do isn't excessive. Those 2 stars are Very bright, so it's to be expected really. 

ps - don't give up on the Oiii either. A few years back i shot the Jellyfish in Ha and Oiii, using just a Nikon D5300, and found there to be plenty of Oiii, so you should have no difficulty with your mono CMOS. https://www.astrobin.com/384884/

@teoria_del_big_bang @scotty38 

Sorry guys, i posted the above in a hurry, and on my phone! Steve, you're right, i shouldn't have put the 2nd paranthesis in there (i've fixed it now, thanks). The figures are not fixed values, they depend on Mode, Gain, and Offset, but seeing as i never change any of these (Mode 1, Gain 56, Offset 25) i just treat them as fixed. 

The formula for determining exposure time is from a guy called Jon Rista. See post#3 below, where he explains it well, but basically the 400 is the 'Offset' (or Bias level) and the 0.45 is the gain in e-/ADU. 

https://www.cloudynights.com/topic/597682-i-need-a-primer-on-read-noise-calc-asi1600/?p=8200280

I realise now that i had just taken rough estimates for my camera gain and read noise, by eyeballing Qhy's graphs. As it turns out, you can get the exact figures from a script called "Basic CCD Parameters" in Pixinsight, so the exact figures should have been 1.56 and 0.33. See the post below as confirmation (or if you have P.I you can just do it yourself):

https://www.cloudynights.com/topic/754530-qhy268m-read-out-modes-questions/?p=11050460

So my own ideal ADU level should be 473 (not 457) and preferably no lower than 422. 

HTH. 

On 18/01/2022 at 11:57, teoria_del_big_bang said:

What sort of sub lengths and any sort of logic behind it or like me its just what seemed to work ?
I ask because there seems to be quite a consensus that more short subs are best way to go, not that they give you better data but that there is nothing to be gained over a certain sub length and that keeping the sub length low means less chance of lost data due to bad subs.

LRGB  should be easy to work out optimal sub length, NB maybe more difficult, obviously considerably longer than LRGB but also will depend on the actual bandwidth of the filters.

Steve

It's true that being able to use shorter subs is definitely a benefit. Like you say, less chance of losing a sub due to wind, guiding issues, etc, and even the good subs may well have slightly tighter stars too. 

I go by a simple formula to help me calculate my sub length. I look to swamp the Read Noise by a factor of 10. At a Gain of 56 and an Offset of 25, the formula is:

(10 X 1.6²)/0.45+400 = 457

So as long as my Mean ADU is around 457 then I know I'm swamping the read noise sufficiently and there's no real need to go any higher. For NB, that means 6 min subs so that's what I use. For BB, you will hit the limit in no time, so it becomes a balancing act between too many subs Vs too many blown star cores. All depends which bothers you the most, but something like 90s for Lum and 180s for RGB would be a good place to start from. 

22 minutes ago, Stuart1971 said:

Back to my question, why 56 and not 60, as the drop off starts at 56, but the lowest read noise seems to be at 60 on the graph…??

From reading various posts online, I believe the firmware enables HCG at Gain 56. There is no gradual transition between LCG and HCG (unlike what the graph says), you are using either one or the other depending on if the gain is below or above the toggle point.

But in all honesty, whether you use 56 or 60 is such a minor point. 56 gets you a little more FWC, but it would be nigh on impossible to tell the difference between two images taken at Gain 56 and 60. So just pick one, set, and forget 🙂