DaveHKent

It depends on what you are imaging. I have only ever done a mosaic for lunar imaging and I do that manually, though I'm aware there are tools that can help.

Once I have stacked the videos and got my final stills, I use GIMP

• Create a new image and make it large enough to fit all the stills. I often default it to a bright green background, rather than black so I can really see where I have put things
• Open all the other images as layers, either as a bulk operation or pull one in at a time as needed.
• If you open all of them, make sure the Layers tool box is open and use the eye icon to make them all invisible
  • You may wish to name your layers at this stage if that will be helpful
• Make the first layer visible and position it to roughly where you think it should go in your final image
  • Lock the layer in place
  • Hit save! Hit save again and keep saving after every operation.
• Now make the next layer visible. This should be one that overlaps a little with the first.
  • Drag the opacity slider down to about 50%
  • Use the move tool to position the second layer over the first. With the lower opacity you should be able to align far easier, placing craters directly over the same crater from the previous layer
  • Once you are happy, drag the opacity back to 100% and you should have a neatly aligned image
  • Optional: Sometimes you can get a visible but not too obvious line where they join, due to slight colour variations. On the second layer select the erase tool with a fairly wide and medium hardness airbrush. Go down the joining edge and remove some of the image to give a softer edge
• Repeat for the other layers.
• Crop the final image to remove the green around the borders, or if you do need to fill in border gaps, use the colour dropper tool to select the background sky from the image and flood fill that colour. If you pick black (#00000) from the colour pallet you will find the sky you captured was less black than you thought. (Fans of Father Ted, think priest socks)
• Once complete, you can leave it as it is or merge all the layers down. When you export into another image format it will merge the layers down anyway, so I usually leave all the layers in my GIMP .xcf file in case I want to go back to it later.

Depending on your equipment, you might also have to rotate some images. I have an altz mount, so if I'm imaging an almost full moon, for me that is 9 images and the final shots can be rotated in relation to the first by a couple of degrees, depending on how long the imaging session took.

Thanks for all the advice. I've tried Siril and it does looks pretty good. Following a couple of videos, the background removal was nowhere near what they got, but I could see on the histogram view that I had a lot of noise there. I'm annoyed at myself for not capturing darks, flats and bias, which would have made a lot of difference and got rid of all those red and green flecks.

I've have nothing to learn if the first one was perfect. I think this is the best I'm going to get it. Most of the work done in Siril, as per the advice here, but I did use gimp at the end just to bring down the brightness of the background a bit. I'm reasonably pleased with the final result.

Thanks. That looks like the opposite of what I did, which was stretching first.

More googling and learning required. Having only done planetary and lunar imaging before, it is amazing just how much of this is in the post processing.

Cheers, I do seem to have lost the running man in my processing.

What did you do to bring that out?

My first attempt at the Orion nebula. I'd appreciate any comments about my image processing technique.

Taken on a night with a lot of humidity in the air and a half moon giving a nice haze over everything.

Skywatcher StarAdventurer, Canon EOS 700D 75-300mm lens at 300mm f5.6. 75x30 second shots. Stacked in DeepSkyStacker and processed in Gimp. I didn't take any flats or darks, but clearly should have done.

Processed mainly by dragging levels. This brought out a green halo around the nebula, so I used curves to remove the green. I think I've perhaps stretched it too much because at higher magnifications the gradients between the colours are very visible. I think when I selected just the background to darken that, I've given too harder edge to the nebula and should have taken some shorter stills as the core is over exposed. I'm not sure what all the small red and green flecks across it are. Perhaps something that could have been removed with darks.

Should I have gathered more data? Would it have been better to select around the nebula for a lot of the stretching, so the stars don't seem blown out?

It's my first attempt at any DSO so I am pleased with what I've got, but want the next one to be better!

Attached, the processed image and the original TIFF.

2021-01-09-m42_stacked.TIF

Is this thread still the best place for issues with oaCapture?

I'm running oaCapture 1.9.0 on astroberry (Rpi 4, Raspbian 10) and it fails when trying to save an AVI file. It does preview the camera and save as a SER.

$ oacapture --debug-level debug --debug-type all --debug-log -
libEGL warning: DRI2: failed to authenticate
qt5ct: using qt5ct plugin
qt5ct: D-Bus global menu: no
[I] oaV4L2GetCameras ( 0x14ba68, 2048, 0 ): entered
[I] oaV4L2GetCameras: exiting.  Found 0 cameras
|QHYCCD|/home/pi/QHYCCD_SDK_CrossPlatform/src/qhyccd.cpp|EnableQHYCCDLogFile start
|QHYCCD|/home/pi/QHYCCD_SDK_CrossPlatform/src/qhyccd.cpp|SetQHYCCDLogLevel start
[D] oaZWASI2GetCameras: allocated @ 0x6861d0 for camera device
[D] _oaCheckCameraArraySize: cameraList was (nil), realloced to 0x6de2a0
[I] oaEUVCGetCameras ( 0x14ba68, 2048, 0 ): entered
[I] oaEUVCGetCameras: exiting.  Found 0 cameras
[I] oaToupcamGetCameras ( 0x14ba68, 2048, 0 ): entered
[I] oaToupcamGetCameras: No cameras found
[I] oaMallincamGetCameras ( 0x14ba68, 2048, 0 ): entered
[I] oaMallincamGetCameras: No cameras found
[I] oaAltaircamGetCameras ( 0x14ba68, 2048, 0 ): entered
[I] oaAltaircamGetCameras: No cameras found
[I] oaAltairLegacyGetCameras ( 0x14ba68, 2048, 0 ): entered
[I] _AltairLegacyInitLibraryFunctionPointers: can't load libaltaircamlegacy.so.1: error 'libaltaircamlegacy.so.1: cannot open shared object file: No such file or directory'
[E] oaAltairLegacyGetCameras: _...InitLibraryFunctionPointers() failed, exiting
[I] oaStarshootgGetCameras ( 0x14ba68, 2048, 0 ): entered
[I] oaStarshootgGetCameras: No cameras found
[I] oaNncamGetCameras ( 0x14ba68, 2048, 0 ): entered
[I] oaNncamGetCameras: No cameras found
[I] oaOmegonprocamGetCameras ( 0x14ba68, 2048, 0 ): entered
[I] _OmegonprocamInitLibraryFunctionPointers: can't load libomegonprocam.so.1: error 'libomegonprocam.so.1: cannot open shared object file: No such file or directory'
[E] oaOmegonprocamGetCameras: _...InitLibraryFunctionPointers() failed, exiting
[I] oaZWASI2InitCamera ( 0x6861d0 ): entered
[I] oaZWASI2InitCamera: exiting
[I] oacamSetControl ( 0x8bf870, 112, 0xbeb27af8, 0 ): entered
[I] oacamSetControl: exiting
[I] oaZWASI2CameraTestControl ( 0x8bf870, 52, 0xbeb27b08 ): entered
[I] oacamSetControl ( 0x8bf870, 52, 0xbeb27b08, 0 ): entered
[I] oacamSetControl: exiting
[I] oacamSetControl ( 0x8bf870, 10, 0xbeb277d8, 0 ): entered
[I] oacamSetControl: exiting
[I] oacamSetControl ( 0x8bf870, 10, 0xbeb278e0, 0 ): entered
[I] oacamSetControl: exiting
[I] oacamSetControl ( 0x8bf870, 27, 0xbeb275a0, 0 ): entered
[I] oacamSetControl: exiting
[I] oaZWASI2CameraTestControl ( 0x8bf870, 52, 0xbeb27b68 ): entered
[I] oacamSetControl ( 0x8bf870, 11, 0xbeb27b48, 0 ): entered
[I] oacamSetControl: exiting
[I] oacamSetControl ( 0x8bf870, 12, 0xbeb27b48, 0 ): entered
[I] oacamSetControl: exiting
[I] oacamStartStreaming ( 0x8bf870, 0x55840, 0x14a140 ): entered
[I] oacamStartStreaming: exiting
couldn't open codec 152 , error: Invalid argument
add video stream failed

The couldn't open codec 152 message appears after I click record.

It looks like the error is coming from the section at line 513 on outputFFMPEG.cc, but I'm struggling to trace back to find what it is actually trying to open. If I run oacapture as root it does work, which suggests a permission issue somewhere, but when I export the AVI file, it thinks it is only 2 seconds long and only plays a couple of frames. I think it was about 15 seconds long.

Is this a known issue, or is it better to just use ser files?

Thanks for the suggestions, a few to look at there, and I appreciate it will never be accurate. I think rather than knowing when will be good, I’m more interested in if there is a slight chance. If there is heavy cloud and rain I know it is probably worth not bothering.

Does anyone have any recommendations for a free astro weather API?

I've been building a display screen at home for a few various sensors and have a bit of space at the bottom. Giving a rough indication of how clear the sky will be for either that night or the next 4 nights would be great. I found once reference to DarkSky, but it looks like earlier this year they were bought out by Apple and dropped all useful features. I have found a few, but not many of them give things like seeing that you get with some of the apps like AstroPanel.

On 03/12/2020 at 13:13, kendg said:

If you have a 3d printer (or know someone who does)

https://www.thingiverse.com/thing:1232862

or this (which I think is better)

https://www.thingiverse.com/thing:1232862

 

You posted the same one twice there.

The one I used is:

https://www.thingiverse.com/thing:241592

I picked up a Celestron Red Dot finder for about £15 and printed one of those, then I'm not always taking it on and off my scope. It has been really useful and cheap to produce.

There are some 3d printing services online if you don't have a printer. I'm sure they would knock one of them up for a very small amount.

I had a go at imaging Mars on Sunday night. No cloud but high humidity (I could see a triangle of light coming down from a nearby street light, which is my usual judge of conditions).

Any advice on the following image? I decided to do a mosaic of a raw frame->stacked->sharpened then reduced to normal size again. Did I sharpen it too much? The image increases in size, as I used "Drizzle 3.0x".

Kit & process: Celestron Nexstar 90 SLT (90mm scope), ZWO ASI120MC, SharpCap. Processed in AutoStakkert, taking the best 40%. Sharpened in RegiStax.

I did struggle with the focus. Being so small on screen and wobbling due to atmosphere, I could not get anything I thought was crisp. In the end, I opted for the spot in the middle of two points I could clearly tell were out of focus.

Cheers. I have been subscribed to sky at night for a few years and never noticed that service. I have probably ignored it as a spam generator. I’ll give that a go.

Rather than the long dovetail bar, I have started using the small green dovetail, which my camera ballhead can connect directly to. I polar align, slot in the ball head and adapter and swing my camera around.

It was taking me a while to get my targets framed up, so I bought a celestron style red dot finder for about £12 and got an adapter so it could fit on the camera hotshoe.

I have to make sure I don’t knock the tripod and make sure everything is nice and lose before I turn it.

Cheers for the further advice. There are a good couple of lens options there from MPB. I get another pay day in a week, I probably need to set a bit more aside but it looks like I can get something reasonable for only a bit more than I planned.

My budget at the moment is probably £100 max. I can wait for a better lens but £900 is a long way off my spending for a lens at the moment.

7 minutes ago, chiltonstar said:

An additional point: you mention "macro of bugs around the garden" - generally short-focus macro lenses are not good for this because you need to get so close to the insect that you frighten them off (most people tend you use macro lenses around 100mm fl for insects).

Chris

Cheers. Macro is not that important. I was mainly wondering why many of the lenses I was looking at were described as macro and does that make them unsuitable for astro.

2 hours ago, Nigeyboy said:

Hi

A 24mm on a crop sensor is actually nearer to 38mm so not ‘wide’ angle really.

While primes are generally better from an image quality perspective, true wide angle primes are expensive.

Take a look at the Canon EF-S 10-18mm. It is cheap but hits above its weight when it comes to image quality.

As for Macro, I would think you will always want as much focal length as you can afford!

Thanks, that does look like a pretty good lens. A bit out of my price range at the moment but I’ll keep an eye out for bargains.

That is f/4.0 at its widest and I was wondering if a lower f number would be better, or does that matter less when you are on a tracked mount?

Wow, cheers. The 14mm looks like the better choice for what I want.

I'm looking for a new lens to add to my kit, currently using a Canon 18mm f/4.0-55mm f/5.6. I want to be able to do wide field images of a Star Adventurer Pro mount. Funds are tight so I'm looking at second hand/ebay market. A 24mm f/2.8 seems fairly common, though many are described as a macro wide angle lens. Just to check, does this mean it is good for both macro and wide angle landscapes? A lens that can do great close up pictures of bugs around the garden would be great, but I want to make sure it is suitable for the prime purpose and get some lovely Milky Way shots.

With a Canon EOS 700D, does a 24mm f/2.8 sound about the right sort of lens for that?

Anyone got some recommendations for the best place to keep up with the latest astronomy news, especially what is visible from the UK?

I missed the news about the new comet until mainstream media started posting impressive pictures. Typically it is set to be cloudy here for the rest of the week! I've checked a few news sites and there is no mention of it in a lot of the news sides. I need somewhere to add to my daily trawl of news that is far more interesting than Brexit and Coronavirus!

43 minutes ago, Nerf_Caching said:

I had the same problems as you; couldn't frame up the Leo triplet perfectly using a star adventurer and Skywatcher evostar 72ed refractor. I first aimed at the star Chertan by eyeballing it as I don't install any finderscopes onto the main scope. I also know that Chertan is on a similar declination to the Leo Triplet. Therefore, I use the RA fine tuning motors to position Chertan at the top of my dslr screen in live view. Then, I lock down the ra and dec clutches and begin tracking in sidereal mode. At the same time, I very slowly turn the declination fine tuning knob so the star Chertan appears to move to the left of the live view and off the screen. Here, I take a test shot. I keep turning the dec knob a tiny bit in the same direction until I find a bright sequence of stars at the top-right of my test shots as you can see in the photo I have attached. I use those stars to frame up the Leo Triplet by placing those stars at the top right corner of the frame. My method doesn't center the galaxies perfectly but then I can also crop the picture later anyway. The above steps are assuming you are photographing the Leo Triplet when they are rising. If you have meridian flipped and are imaging them as they are setting to the West then reverse all the directions(up becomes down and so on.). This is 48 minutes of integration with a Canon 650d stock dslr using 30-second subs at ISO 800 under Bortle 8 skies. I hope this helps and I apologize if my explanation is rather poor!

Cheers, that does help. I have a reasonable knowledge of the sky, recognizing most constellations and occasionally just use binoculars for that quick look about before going to bed, so I should be able to get by with this. I'll probably keep a tablet with stellarium to hand too.

2 hours ago, FaDG said:

Well, finding M81 in Leo will certainly prove difficult! (😄 tongue in cheek) 

Seriously though, there are different solutions: several members suggest fitting a red dot finder to the dslr hotshoe as you're now prepared to do, and using it to point it towards your target. Obviously a basic knowledge of the sky and a sky chart is needed. Personally, I don't use an added red dot but the LEDs inside the viewfinder. It works perfectly. Another solution is to point the camera in the generic DSO direction, take a shot and Platesolve it, applying corrections as needed knowing the target coordinates. 

Hmm, yes M66. Why I should double check what I'm saying in posts before clicking 'reply'!

What is the best way to find your imaging target with the SA mount? I have been out in clear skies but poor seeing recently with a DSLR and 75-300mm lens. I was looking towards Leo and fancied next time going up to 300mm and seeing what I could get of the M81 & co triplet. Finding what I have been aiming at has been hard where there are a number of fantastic images on this thread with targets nicely centered. I don't get a lot in the live view.

Just trying distant trees in daylight, I have found I can fit my scope (Nexstar 90SLT) to the other end of the dovetail bar and align the two to give me a visual view. However that only helps if I'm then only going to move them in RA and not DEC. Another option (if I can found a mount) is to piggyback the camera onto the finderscope mount on the telescope.

I have printed a red dot finderscope mount for my DSLR. Is the trick to use that to get approximately right then take shorter exposures until you have framed your shot?

I bought a Manfrotto 055CL tripod on ebay for about £40. I looked at the spec of a few. The Horizon 8115 was another decent one that showed up.

I used to keep mine in an alcove between a cupboard and a bookcase, with some bungees attached to the wall to stop it falling. When we redecorated and got a larger bookcase, I made a sturdy 18mm ply cupboard and put it in the garage. There is no dampness in there, not much dust or bugs but the cupboard keeps them out anyway. It keeps the tube within a few degrees of outside temperature, which hopefully cuts out some of the air currents of it cooling when I take it out.

I did try a few coats of primer to make it smooth and then paint it with a metallic black paint intended for use on metal, thinking it would give a bit of a sparkly effect. There was still too much grain showing through so it ended up looking a bit rubbish. Functional though.

Did you manage to get any shots?

After seeing your post, I went out with about 10 minutes notice. Enough to throw my camera on a tripod. There was a light cloud covering, which give a very blurred moon and venus. 55mm is the widest lens I have and from my location the ISS was much further away than I expected, so it was way out of shot. The result was a series of pretty rubbish pictures.