symmetal

I've used the latest PS CC camera raw de-fringe on your posted image. Your blue halos have a solid hard edge and are clipped while the red and green halos fade into the background, so  de-fringing blue will leave you with a hard grey edge. On the sample I posted the blue halo fades into the background so the defringe tool can leave the underlying yellow while neutralising the blue, giving a nicer edge.

Alan

To remove any halos left after processing with Startools, I use Photoshop rather than the Startools fringe killer, using this handy tip. It uses the camera raw de-fringing option which is selectable as a filter. Not sure if CS4 has all the features mentioned but here's an example using a crop of the Sadr region. Normally you don't need to mask the image beforehand but with Sadr itself it took several passes using the filter so I made a soft-edged masked around Sadr.  Here's a before/after:

Alan

Here's an animation of the past 48 hours showing the progression of the duststorm in false colour IR channels. Data from EUMETCast. Cornwall seems to have escaped it as the wind from the west is keeping it away. 🙂

The bandwidth is the difference between the highest and lowest wavelengths that the filter passes. 

From the chart read the values at around 50% transmittance. For example, the red filter bandwidth looks to be around 685nm - 580nm = 105nm.

For narrowband, the bandwidth is stated in its description, so a 7nm Ha filter has a bandwidth of 7nm. In reality, optimum narrowband exposure durations are as long as you can get away with before you run the risk of mount tracking errors, or aircraft etc, spoiling the image.  I usually use 10mins exposure for NB, even though the calculated optimum values are over an hour for my Bortle 3 skies. 😉

If you have heavy light pollution, then the calculated NB exposures may be more useful values to use.

Alan

Carole,

This detailed article gives a good description, and the animation half way down the page, and below, shows the difference between an eq and alt-az mount. An interesting point is that if you're pointing exactly East or West there is no field rotation as that's where it stops and reverses direction, and it's at a maximum when pointing North or South.

From the article:

The stars rotate around the central aiming point, but over 24 hours they WOULD NOT make a complete circle.
Orion does not "flip upside down" as it progresses from the western horizon, under the Earth, and back to the Eastern horizon.
The following animation shows what would really happen if you or your camera had X-ray vision and could see Orion as it passes under the Earth (shown in green).
Note that the Celestial Equator (shown in dark red) as well as the frame as seen from an Equatorially mounted camera (yellow) stay with the figure constantly. The Alt-Azimuth view (always level with the ground) is shown in red.

Alan

4 hours ago, Martin Meredith said:

I had a similar question having just obtained my first CMOS camera (ASI 290MM) and that reply really helps - thanks Alan. In particular, there's quite a lot of information on the web about changing the offset every time the gain is changed, which sounds like a nightmare... so its good to know that it can be set at a fixed value with a reasonable certainty that black clipping won't occur. I have mine set at 25. I also tend to use unity gain only, no doubt suboptimal but I'm finding it gives me results close to what I get with a CCD and an absence of stress!

Martin

Martin,

Changing the offset means you need to take a set of darks for every different offset value you use. 😲 Just not worth it. The easiest way to check you aren't black clipping is to take a bias frame or a short dark frame of a second or two and look at the histogram and image statistics. Here's the master bias from my ASI6200 below. As you can see the peak in the signal occurs at ADU 500 on the histogram, due to the offset value of 50 used as I mentioned above. Due to the noise distribution there are actual ADU values varying from 452 to 618 ADU shown on the statistics. Individual bias frames will vary to some degree around these figures. I only use the camera at one gain setting of 100, where the HCG (High Conversion Gain) mode kicks in. I could use an offset of say 20 and that wouldn't create any black clipping on this camera, but for the tiny increase in dynamic range, it's not worth changing from the default offset 50 .

Some CMOS cameras, the ASI1600 being one, had different internal processing on exposures less than a second compared to longer exposures, so the bias calibration frame was not representitive of the bias contribution to a long exposure image so the image would not calibrate correctly. This meant that darks had to be used for calibration, rather that just using bias, like with CCD cameras. Although amp glow with many CMOS cameras made darks necessary anyway.

My ASI6200  doesn't exhibit this behaviour with short exposures and has no noticeable amp glow, similar to the ASI2600, so bias frames could be used as calibration frames, although by habit I still use darks. 🙂

The ASI290 seems to be a fairly new camera and has a HCG mode kicking in at around gain 60. Unity gain is the way to go as well, for the best overall performance, at least when starting out, and the ASI290 unity gain is at 110 so no problem there. If you wish check your bias frame and a 1 sec dark to see if they are noticeably different in peak value and noise spread, unlikely I would think on recent cameras. As your camera is uncooled though you would need darks for long exposures anyway. For planetary I don't bother with calibration frames, though you could use a bias or matching short exposure dark if you wished.

Alan

Edit: Offset isn't a feature peculiar to CMOS cameras, CCD cameras have an offset value too for the same reason. It's just fixed, as well as the gain, by the manufacturer so isn't user adjustable.

The offset is an analogue DC voltage added to the analogue signal read from each pixel before it goes to the A-D (analogue to digital) converter in the camera. The offset needs to be large enough that no black clipping occurs on the output from the A-D, that is, no pixel has a digital value of zero. This is especially important when taking bias and darks as this will lead to calibration errors which can't be fixed. Increasing the offset effectively increases the 'brightness' of the image and so sets what level corresponds to actual 'black' in your image.

If the offset is too large then you will lose some dynamic range in the image as the number of discrete digital levels available to represent the image signal reduces. When CMOS cameras came out there was some discussion on making the offset as low as possible to avoid loss of dynamic range. The ASI1600 when it first appeared recommended changing the offset depending on the gain used, but this was quickly dropped and the offset was recommened to be set to a fixed level where black clipping was not an issue at any gain.

On the latest cameras this is usually set to quite a conservative value, and you could probably lower it a little without issues but in reality the loss of dynamic range due to it being set a bit too high than necessary is not significant.

For the 16bit ZWO cameras like the ASI2600, an offset increase of 1 increases the ADU output by 10, so the recommended setting of offset 50 means the 'black'  output from the camera is around 500ADU. Clipped stars which correspond to 'white' are at 65535 ADU so you're left with 65035 levels to represent your image which is fine. 12 bit cameras like the ASI1600 only have 4096 levels to represent the image anyway, and they still give good results. 🙂

Alan

The plate solving angle is the angle of the camera sensor edge orientation compared to a line through the sky joining all points at the same RA. In other words the long axis of the camera is parallel to, (at the celestial equator), or elsewhere tangential to a circle in the sky joining all points at the same declination. 'Up' can be considered parallel to this imaginary line joining all points at the same RA.

It's easiest to use Stellarium for example and overlay the sensor outline using the oculars plugin and see how the sensor orientation changes as you move around the sky. At the celestial pole the sensor overlay spins around rapidly for tiny changes in pointing position. 

It looks like you're plate solving at Polaris. You should never do this. Lines of RA which are say 1 hour apart, are well spaced near the celestial equator, but get closer and closer together the higher your target declination, until they all converge to the same point at the celestial pole. Likewise the circle joining all points at the same declination gets smaller too, and is a single point at the pole. If you are not absolutely perfectly polar aligned, and no-one actually is, a small pointing error near the pole will likely show a large error in RA and/or DEC, and likewise a large error in the angle shown by platesolving. These values shown are really meaningless.

To accurately get your camera angle correct always plate solve and adjust the required camera angle at a low declination. Then slew and platesolve to your intended target and your camera angle will stay the same wherever you're pointing. It's usual to set the platesolving camera angle to 0 degrees, or sometimes 90 degrees to best frame your target. 

Alan

To get an accurate reading of what power you are actually using it may be worth getting something like this to plug into the RCD and then plug your extension into the meter. While you're imaging, It will give a continuous display of the actual power being used (watts), as well as the curent (amps) which would then give you a good indication of how long the portable power unit would last delivering that same power. 

Current/power ratings printed on your devices like camera, mount and laptop are the maximum power they can use rather than the average power in use, which is normally much lower, so are unreliable as actual indicators of power required.

Alan

Glad to help Brendan. 😀 

I've just noticed that the program as it is will detect '-C' in the filename as being a temperature, as I've included '-' as a temperature character, in order to detect minus temperatures, although you didn't request minus temps in your initial post. If you think this may cause an issue, let me know, and I can modify it slightly so that an actual number must appear in front of the 'C' character, before the sub-string will be treated as a temperature value. 🙂

Also, you may prefer the temperature sub-folders to have a more consistant format, where there are always two numbers before the C, like 02C, 08C, 10C. This will then show them in ascending order in the folder, if alphabetically listed.

Alan

Glad it worked for you Brendan.

I've removed the Temp_ from the directory names as you requested. The program is a bit larger now as on rebuilding using static libraries as I thought I had before (so you don't need extra .dll files included) it stated that extra libraries need to be downloaded from Microsoft to enable this which I did. It's now added some static libraries to the executable. Anyway, here it is without the Temp_ 

TempSort.exe

Alan

Hi Brendan,

To amuse myself I've written a cheap and cheerful program 🙂 that should do what you want.

It looks for a 'C' character in the filename and works backwards until it finds a character which is not a number or a minus sign. If the result contains a number it creates a subdirectory named 'Temp_12C' for example and moves the file into it. If the filename happens to contain a number followed by C which is possibly in the filename as a target name, it will take this as a temperature. Surrounding the temperature with underscores or possibly spaces in the filename would make it more robust in picking the temperature correctly.

It's a CLI program so works from a 'DOS' screen though the easiest way to use it is to copy the program into the folder containing your image files and just double clicking on it. The DOS box flashes for an instant and then your files will all be moved into their temperature subdirectories.

The program works on the current directory so if you want to run it from a DOS window, go to the directory where your image files are are and type the full path and filename name to the TempSort.exe program. This will list all the files found and whether they were moved. I could have had the image file directory passed to the program on the command line but it's no quicker really so left it as the current directory as the working directory. It doesn't search through subdirectories for image files as it stands, and assumes they are all in the same directory to start with. 

I can make any changes if you wish, like it's picking up files you don't want it to for example. For testing it I recommend you copy some of your image folders to a test area and work on them there just to check nothing untoward happens. No files are deleted, just renamed with from, to parameters causing them to move (if it's possible to do so) so no data should be at risk, but I have to say to use it at your own risk to absolve myself. 😊 Here's the program

TempSort.exe

Here's the C++ program listing from Visual Studio if you want to see it.  😉 It's fairly small as you can see. Hope you're happy with it.

Alan

Edit : I assumed your temperatures were in whole numbers as in your first post. If you wanted decimal degrees included It just needs a small alteration to the program. Can you spot where in the listing? 😀

I'm no expert in scripting languages, but if no-one else offers a script, I can write one using C++, either as a CLI version that should run on any OS, or if you just use Windows, with a Windows GUI front end to make it more friendly to use.  🙂

Alan

According to the Beelink site they do support auto boot on powering. I don't have this particular model but all the mini-pcs I've used including Beelink work fine in headless mode, with no dummy HDMI plug, or keyboard/mouse required. The resolution can be set by the remote computer over vnc or remote desktop and that resolution is kept after repowering.

Alan

A common mistake if you're not too familiar with soldering, is when you seem to need three hands. One to hold the wire on the board, one to hold the soldering iron and a third to hold the solder. In this case it's tempting to pick up solder on the end of the bit and then carry it to the workpiece and apply it to the joint. This however, allows the solder flux embedded in the multicore solder to burn off before it's reached the joint leading to an uneven 'dry' joint which doesn't flow nicely into a smooth shiny surface.

The technique in this case is to 'tin' both surfaces beforehand. In other words with the wire lying on the workbench, held down by any weight to stop it moving around, apply the soldering iron and solder to the end of the wire at the same time for about a second until the wire end is fully coated in a smooth layer of solder. Not too much that it forms a blob. Then do the same to the PCB, applying the iron and solder to the PCB track, again forming a slight smooth mound of solder on the PCB. Then hold the wire against the pcb with one hand and apply the soldering iron with the other hand, for about a second, to the 'tinned' wire and pcb track at the same time, so both solder surfaces fuse into one smooth shiny curved surface. Enough flux should still be remaining in the two tinned surfaces, to allow this to happen. 🙂

Alan

Hi Nigella,

I think you need a higher wattage soldering iron, or a larger bit, as your solder connection on the rear of the board is very 'crystalline' and not flowed, due to the solder temperature not getting hot enough. This forms a 'dry joint' which can lead to a future intermittant connection. There's also a bit too much exposed wire visible, particularly on the +ve wire which could cause a short if the wire flexes a little. 

Apart from that a good job. 🙂

Alan

Great image for just an hour Adam. The noise, while evident isn't the blotchy type which can spoil some cmos images without a longer integration time. The benefit of a 16 bit camera. 😊

Alan

Ah. I get it now. So the FF is before the bad base plate in the imaging train. It's hidden inside the focuser. In that case changing the camera tilt to counteract the base plate tilt would be OK as the sensor would end up orthoganal to the FF although slightly shifted to one side of the central optical axis.

As I mentioned before, this means you have to determine the sensor cover slip reflection spot, as all the other reflection spots will end up describing circles as you rotate the camera, and only the cover slip reflection will be stationary when the camera tilt cancels out the base plate tilt. The whole image train including the base plate, needs to be on the jig of course. But not with FF attached to base plate. 😁

As Laurin Dave suggests, if you show the problem to APM, they may send you a new base plate, either free or at low cost as it's clearly a problem with the plate.

Edit. If it's the whole central insert in the base plate that's tilted then that would mean the FF attachment is also tilted, so the FF is never aligned centrally to the optical axis. 😬 This means canceling the plate tilt with the camera tilt will mean good scope focus across the image but a change of FF back focus across the image and so misshapen stars. Adjusting camera tilt to be orthogonal to the FF may give round stars but the focus will change across the image. 

You could try the tilting rings on the FF side of the bad plate to make the FF on axis, and then a matching tilting ring on the other side of the plate to cancel the plate tilt. This needs M63 tilt rings though on the FF side which probably aren't available unless specially made.

Trying to get all those lined up is not an easy task. 😲

Good luck!

Alan

I'm not sure I follow where the bad base plate is now. 🤔 In your original photo the base plate was screwed to the rear of the focuser and was also included in the setup on the jig. In your latest image with the FF is that the same base plate now to the left of the FF, and the FF is now screwed to the focuser or is the separate bad baseplate still between the FF and the focuser?

If it's the former then in this case the bad base plate is just a M63 to 48 adapter. Could one of these take the place of the bad baseplate instead or am I missing something?

If the bad baseplate is still attached to the focuser, then yes, correcting it by the camera tilt will cause the FF to camera distance to vary over the image which is not what you want. The correction for the bad baseplate would need to be done before the FF either by the 'tilted' rings or a proper tilt adjuster fitted to the bad baseplate directly.

Alan

I'm not sure where the rotation occurs when you rotate the camera to change image orientation when it's mounted on the scope. If it's between the base plate and the camera then it's a problem, as tilt will change when you change camera orientation.

If the image train is fixed as you have it in the jig, then you should be able to offset the camera tilt to counteract the base plate tilt. It will act as in the earlier question where the sensor was not in the centre of the camera body. When the camera tilt is correctly set, all the laser dots will rotate in a circle apart from the reflection off the sensor cover slip which should be stationary. This should be the brightest reflected spot though may not be so easy to determine.

Doing this of course means that the image train must all be kept together in one piece so cameras cant be swapped over without tilt reappearing. This isn't ideal so it's best to correct the obvious tilt source as close to that source as possible.  Using one of the tilt rings as gorann posted fitted over the base plate thread in the correct orientation should help, assuming there is enough 'play' in the thread when loosened to allow it to achieve this degree of tilt. Check and adjust the camera on its own in the jig for no tilt, and then try the whole train in the jig with one of the tilt rings next to the base plate in the correct orientation, to see if you can again achieve no tilt indicated on the jig.

The alternative if the above doesn't work, is to fit another tilt adapter to the base plate and use that to correct the base plate tilt. As I've mentioned before, the Gerd Neumann tilt adjusters are very easy to adjust, though a little pricey. FLO don't stock them though.

Alan

Can you post an image of it set up in the jig.  Are the filter wheel and/or adapters still attached? On another thread you had to buy some screws to fit in the QHY tilt adapter plate to make it function. If the tilt plate has a 1mm gap on just one side that should have made some difference. Did you loosen off the tilt screws on the opposite side a little before making the 1mm tilt adjustment and then retightening them. Depending on how stiff the tilt plate and the camera front are, adjusting just one set without loosening off the others, may just end up distorting the tilt plate/camera connection rather than giving just tilt.

Alan  

2 hours ago, neil phillips said:

4 How do you remove the AR Protect window from the ZWO 178 Camera ? I may just get a dedicated UV Venus Filter. But even if i go that route. The removal of the AR Protect window question still stands. 

The front plate of the camera unscrews. If it's too tight a rubber strap wrench around the 2" nose piece should loosen it.  The sensor is surrounded by a rubber, or possibly neoprene ring, and the protect window sits in a recessed cutout on the front of the ring. When the front plate is screwed on, it pushes the protect window into another recess in the front plate, keeping it in place, and so stopping dust from getting in.

The 178 manual pages 9 and 10 have the response graphs of the AR protect window for the mono camera, and the UV/IR cut protect window for the colour camera which may help.

Alan

9 hours ago, bluesilver said:

I did notice a funny reflection when i was trying things out a few days ago at about 1/2 moon

I was using a bahtinov mask on a bright star to work on focusing and while i got a good spike alignment, i did notice that i could see sort of a light ghosting of the entire mask behind the star

This is most likely just an artifact from the bahtinov mask and won't appear on normal images.

I assumed the ASI2600 was a M48 thread but it's actually M42. Not that that makes much difference. As you're using a 2" filter you can still place the 14mm spacer between the filter and camera if you wish. At some distance from the camera though the M42 thread size will cause vignetttting on an APS-C sensor, so try it out and see what happens.

The 98mm back focus distance mentioned by gorann does back up why the first spacer is 43mm, as my first post queried this. 🙂

Alan

It's common to put the filters closest to the camera but this is when using 1.25" filters where vignetting may be an issue. If they are 2" filters like it seems you're using, then their position in the optical train is not really an issue. Having them further from the camera may be beneficial if there is evidence of reflection artifacts in your images from the filter surfaces but this is unlikely.

1 hour ago, The Lazy Astronomer said:

I believe the extra spacer/shim should go between the filter and the camera.

In my mind (and I may well be wrong!), the extra fraction of backfocus is needed after the light path has been slightly altered by passing through the filter.

The change in backfocus distance  is not dependent on where the light path has been refracted through the filter as the filter surfaces are parallel, so the filter location and subsequent extra spacing distance required can be put anywhere between the FF and the camera. 🙂

Alan

The spacing for 55mm back focus mentioned in the camera manual is for connecting to the many field flatteners which are designed for 55mm spacing from the FF rear flange to the camera sensor. This is because a DSLR + camera mount to T2 (or m48 if necessary) adapter is 55mm from the adaper front to the camera sensor so will screw directly on the 55mm back spacing FF without any extra spacing.

As your FF has 96mm back spacing this 55mm figure doesn't apply, though I believe there is an extension spacer included with your field flattener which  would allow a DSLR and adapter to connect to, and so achieve the 96mm. This spacer would be 41mm.

Possibly your 43mm spacer mentioned is intended to fill this role. If any glass is included between the FF and the sensor then 1/3 the thickness of the glass should be added to the 96mm to give the actual spacing distance. With a 2mm thick filter and a 2mm thick camera protect window this means 1.3mm should be added on to the 96mm. The 43mm spacer is possibly to help take account of this.

Your diagram is essentially correct for 96mm, though add the 1.3mm or the actual figure depending on your glass as necessary to the 96mm.

My only concern is the14mm spacer/adapter to your filter drawer in your picture. Its diameter looks rather small. Is it M42 (or T2) thread? Your camera is M48 thread, as well as the FF rear. Putting M42 that far in front of the camera may well cause some vignetting. If the 14mm section is actually M48 then no problem.

Alan