Xilman

Some optical astronomers are not affected much about daylight either, though clouds are still a PITA.

Solar work has to be done in daytime.

It is very common for planetary observers of Mercury through Saturn to sketch or image in daylight, as do lunar observers of course.

Bright stars are easily visible telescopically in full daylight, especially through a near-IR filter. One item on my bucket list, and it has been there for years now, is to image as many Messier objects as possible while the Sun is above the horizon. M45 should be trivial. I have high hopes of M13, M36, M37, M92, ...  The main problem is finding them, though offsetting from the Moon, Sun or Venus may be a solution.

So don´t come over all superior. You are allowed to sneer about how clouds cripple us.   😉

There are quite a few variable stars in Messier 5, though few people seem to go looking for them. This image shows V42, a RV Tauri type of pulsating variable. It was close to maximum brightness when the image was taken on 2021-07-02.

Those of you who like imaging M5 may wish to monitor how the VS changes the appearance of the cluster over time. Even if you prefer to use a Mark-1 eyeball the star's varying brightness is fairly easy to follow as it is around 11th magnitude.

35 seconds on an unfiltered SX 814 camera attached to a 0.4m Dilworth reflector.

It is not clear from your description whether you are taking separate flats for each filter you use. I hope you are, because each filter will have its own distribution of crud on its surfaces.

Ideally you should take flats before each observing session so that changes in dust distribution are accounted for. Twilight flats are generally used for this approach, though dome flats are also a possibility. In my experience, very few people are this fastidious --- I am certainly not, but I have a very stable set up with a fully enclosed optical train mounted in an observatory so I can get away with re-using flats for a period of a few weeks.

It started as a discussion about noise in images. I provided a link to my experiments with FABADA, which can do quite amazing things with noise in images. The discussion all rather snowballed from there, sorry.

If a moderator wishes to move some of this thread elsewhere, somewhere more suitable, I would be quite happy with that.

As for equipment, all I have used is the fabada software. The data was provided by @alacant so I can't say anything meaningful about how it was taken.

Paul

On 11/12/2023 at 10:47, Xilman said:

That is a new one on me.

What is the alleged size of the image? Do the FITS headers agree with the data which follows? I would hope so or something is very seriously wrong.

Is it a colour image? I only ever process monochrome images so there is only ever one HDU. If so, you may need to specify each plane separately and re-merge the three after smoothing. If this is the case, use the -hdu option setting its value (presumably) to 0, 1 and 2 in turn.

If you still can't get it to work, I suggest contacting the author for assistance.

Good luck!

OK, I sussed it. The code as written can not handle anything bu 1D (spectra, etc) or 2D (monochrome image) data. A colour image is 3D data, the third dimension being the colour channels.

So what I did was to separate out each channel in your image, smooth them separately, and re-combine into a tri-colour smoothed image.

Added in edit: I contacted Pablo about this issue.

1 hour ago, alacant said:

python3 fabadaCMD.py -out smooth.fits r_pp_cyg-1_Light_stacked.fits  100
Starting smoothing with fabada in r_pp_cyg-1_Light_stacked.fits image...
Warning: Size of array not supported
Warning: Size of array not supported
---

Any ideas?

 

That is a new one on me.

What is the alleged size of the image? Do the FITS headers agree with the data which follows? I would hope so or something is very seriously wrong.

Is it a colour image? I only ever process monochrome images so there is only ever one HDU. If so, you may need to specify each plane separately and re-merge the three after smoothing. If this is the case, use the -hdu option setting its value (presumably) to 0, 1 and 2 in turn.

If you still can't get it to work, I suggest contacting the author for assistance.

Good luck!

10 hours ago, alacant said:

Thanks. Downloaded and installed. I'm by no means a Python expert but promise to feed back my findings. I had an error with the noise switch. Could you give me an example cli for a fits file?

I call it as "fabada -out smooth.fits raw.fits 100" for an appropriate value of 100.

The noise value is chosen by experiment! Too small and no smoothing is done. Too little and artefacts appear.  I am sure that there must be a better way but I have not yet found it.

What sort of error do you get? There may be a bug in the code. I found a couple when it was first released but the author is very responsive and within 2 days he  told me that he'd fixed them. As I had already implemented my own fixes I didn't bother downloading a fresh copy.

I have two 150mm (6 inch) refractors from which I may be persuaded to part. No mount, just the OTA,

1 hour ago, johnturley said:

I spend ages looking at things I've no intention of buying. 

John 

My favourite telescope porn can be found at https://planewave.com/product/pw1000-observatory-system-rc-optical-design/

If I had a megabuck to spare I would buy one like a shot.

I see you are using Ubuntu (like me) so you may wish to investigate FABADA. It can be quite spectacular when it comes to noise reduction so perhaps you could continue taking longer exposures.

Doubleplus ungood. 8-(

Only two ornaments are visible. Do you have all three?  Earache, headache and toothache that is.

Now hoping my Meade out in La Palma is not in a similar condition.

A 120mm refractor makes a very good guider. 😉

That's what mine is used for mostly. It is also far far better for solar work than the 400mm for which it acts as a guider most of the time. Solar heating would destroy that one.

I concur: contact SX.  Very very helpful. I also recommend joining their mailing list which is run as a Yahoo Group.

I suspect they will tell you to lubricate the wheel, but contact SX first.

As with many things concerning astronomical equipment, it's not how big they are but what you do with them.

Do you rate a large field of view higher than a larger image scale? Do you have steady hands? And so on.

If, for example, you wish to observe variable stars the larger field of view makes life markedly easier. If you wish to look at double stars or the moon, a higher magnification helps.

Horses for courses.

1 hour ago, cacophonist said:

Thank you both, that's really helpful!

I'll of course upgrade the mount in time but at least for now I won't spend more than a few hundred on guiding when I have such a basic mount.

You may wish to consider a software solution before, or as well as, spending money. It will not be anywhere near as good as a decent mount or a decent autoguiding system but it may well help.

Essentially, find out the difference between a true point object and what it looks like after it has been through your system and onto the camera. That is the point spread function (PSF) and is the combination of seeing, diffraction effects, optical misalignment, poor guiding and more besides.

Once you have your PSF you can then feed it into deconvolution software. As I said, it will not solve all your problems but could well improve your image quality. From my experience it can improve resolution by a factor of somewhere between 1.1 and 2.0 and I have a good mount and optics. What I rarely have is superb seeing.

Do not expect miracles. Do not use it if you wish to perform precision photometry or it will destroy your measurements --- that is why I rarely use this technique.

One further thing: it is likely that a half-way decent autoguider will improve the results even after getting a better mount, so your investment is unlikely to be wasted. At the very worst, it won't harm anything.

9 minutes ago, John said:

I will be 101 in 2061 so probably won't see it's return. 

I'm glad that I had a decent 6 inch scope back in 1986 - it was rather dim in binoculars !

I will be 104.

The chances are not good, but still non-zero, that we will be capable of observing it.

Comet Halley is at aphelion today. It will be getting ever brighter from now on so start planning your observing sessions!

😉

Paul

12 minutes ago, Paul M said:

Thanks Paul, I tried that already. ASTAP has that function available but my one attempt with this data so far didn't go right.

I've used it in the past with success so maybe worth another, less rushed attempt.

Anyway, other than play with the data already collected, I'll leave this one alone.

Upwards and onwards!

An obscure Jovian satellite next, maybe

Go for it. Nereid would also be a worthy target for you. Saturn has a whole bunch of accessible satellites too. Phoebe would be a nice and easy one for starters.

I am sure that's a success. Well above the noise level.

There are other things you could try to enhance the image.  Obvious ones are to stack on the calculated motion of the TNO so that its pixels are slightly less trailed (though the stars will be, of course) and to separate the RGB frames of each sub and then stack them as a monochrome image. Not only will that raise the SNR slightly but monochrome images are generally more resilient to extreme contrast enhancement measures.

Note that sky brightness is an important hindrance but it is certainly possible to image stellar objects which are fainter than the sky background. I've managed 10% of sky, or better. Professionals commonly achieve 1%. If it is not obvious how this is possible, it is most certainly worthwhile working out how it can be done.

You should be able to get below mag 20 if you really push your equipment and your software.

5 hours ago, Elp said:

I assume their FWHM may change slightly? I ask because three or four of the red ones I think I've captured in my stacks, one of which was done before December.

FWHM? I do not understand. The outburst rises from below mag 23 to maximum - typically 17.5 - in less than a day. If you do not image it in the next 2-3 days it will too faint for you to do so.

12 hours ago, Elp said:

Intrigued by this, would these not be present in images prior to December 2023?

The NR has a very short eruption period.  It wasn't visible 24 hours before that image was taken. It will likely have fallen below magnitude 21 within 3 or 4 days. If you want to see it, you have to be quick.

Anyone who wishes to image a recurrent nova on M31 ought to plan to do so within the next day or few. It erupts with a period of about 12 months and has been visible since at least 2023 Dec. 05.54775 UTC. Discovery announcement in this ATel   https://www.astronomerstelegram.org/?read=16361.  Note that 120 seconds on a 0.5m telescope puts it well within range of most amateur equipment.

Nick James of the BAA-VSS has produced this image. Coordinates are given in the image, as are the magnitudes for four sequence stars. Any photometry will be valuable.

Just now, Xilman said:

Have you checked with the MPC to see whether you picked up any asteroids unintentionally?

Not very likely, as most random fields contain at best an asteroid at mag fainter than 22 or, perhaps, as bright as 20 if you are particularly lucky.

Worth checking anyway. Once I was imaging Nereid and found a rather nice trail form (16095) Lorenball in the frame.

Paul (the other one)

My apologies.  I did not examine your image closely enough. It appears that you have checked for other asteroids in the district.

Have you checked with the MPC to see whether you picked up any asteroids unintentionally?

Not very likely, as most random fields contain at best an asteroid at mag fainter than 22 or, perhaps, as bright as 20 if you are particularly lucky.

Worth checking anyway. Once I was imaging Nereid and found a rather nice trail form (16095) Lorenball in the frame.

Paul (the other one)

4 hours ago, Paul M said:

My subs ran between 01:19 and 03:58 on  01/12/2023

I got the position from SkySafari using a central time (not that it matters over the span of the subs) 02:07 giving: RA= 05:22:46.12  DEC = +03:58:32.2, which is where the box is. 

It seems that I didn't verify my coordinates with MPC or any other source. Looking at Stellarium it gives coords much closer to those you give from MPC and had I used them the target would have been in the field.

It's a definite miss, but if the camera had been rotated 90 deg then !Gunk would have just made it into the frame, waiting for you to correctly identify it! I just know it would have been there....

Oh well, a lesson learned. But SkySafari has been reliable in the past. 

 

 

As Ronnie famously said, having learned it from, Mikhail Sergeyevich, "Trust but verify".