alan potts

Well thank

38 minutes ago, carastro said:

I just ran your image through Gradient Exterminator and there is definitely a gradient there.

BEFORE

 

AFTER Gradient Exterminator

 

Getting rid of the gradient allows you to further stretch your image. 

This is a further stretch and an increase in the colour.

 

 

You've got some nice data there by the way.

Carole 

Thank-you Carole, this I guess is the only part of my sky where there is a touch of LP, believe me you would kill for sky like mine. It was much better over to the SE area where there is a town Sevlievo about 4 miles away. They changed the lights about 3 years back to these LED type, before this there realy wasn one, even now I can see a 4th mag star in this so called LP, but the targets I have been on lately are over that way.

Alan

I wonder if it is worth trying another (7th set) of Flats and Dark Flats?

Alan

2 hours ago, Davey-T said:

If you have P'Shop there's a YT video by Doug German showing a gradient removal process which works with a bit of experimenting particularly on galaxies in a no t too dense starfield.

Davde

I know this technique well but it is no good on say the Sole Neb, I have used it many times on Globs and clusters, not tried Galaxies though.

Alan

3 hours ago, carastro said:

What do you normally use for processing Alan?  

If you use Photoshop Gradient Exterminator is a plugin which is not free, but a lot cheaper than buying Pixinsight.  Also Pixinsight is not exactly user intuitive.

I get gradients all the time and use GE in most images.  I think it depends on the Moon, and whether there is any distant or local LP which may not be obvious to you when imaging.  

Carole   

I use PS CC and have no plug-ins. Astro Flat I have been told is good too. I don't really have any LP Carole apart from to the SE with could affect this shot. I see nothing in the image at all until about the 4th stretch. I have even use tools in PS to measure each side and the differences is 1-2 in RGB using PS and this I would have thought was normal but after this 4th or 5th stretch the differences can be 20 and I just struggle to see this is SKY over just over 1.4 degrees from side to side, it is not the Moon that I am sure of.

I have just done this stretch and level adjust 4 times, cropped edges out to start, now you see it clearer. The 1-3 stretch saw nothing, it looked flat.

Alan

13 minutes ago, Laurin Dave said:

Yep looks like a sky gradient..  very minor though (he says jealously).. Here it is after a quick gradient removal (Dynamic Background Extraction DBE)  in PI..

Dave

 

 

 

 

I am assuming PI is Pixs insight, where do you buy this if I wanted it, I see FLO only have Astro Art, looks half decent now you have done that, I feel it could stretch more than I have done.

Alan

Thanks all of you I did wonder, some images don't have it but are in different areas of the sky. The problem only seems to be visible after 3-4 stretches, I have even check image both sides with the appropriate tool and can't see anything in the data but after a couple more stretches is comes out, I have manage to hide it a fair bit in most images. I thought iI was doing something wrong, I think after I come out of hospital i will get something like, Astro Flat which Steve uses, and there isn't much wrong with his images.

Alan 

This is 3 hours of 4 minute subs on M33, you know this.  I am getting a darker area to the left hand side most of the time no matter what I shoot. I tend to collect 10-15 subs per night on a target and move on, this is from a few nights and some of the subs will have been taken when the the camera was in or could have been in a slightly different position as I took it off to clean the bunnies out. Is this causing the issue or something else, I have checked the camera is not at an angle and though not perfect stars are pretty round, misshape caused by lower down guiding. I have not spent much time processing so I know it can be better.

Is this just a gradient of a different nature, if so I must get some software soon.

Alan

Yes excellent image and as said rare to see the whole object.

Alan

Stunning image you have taken there, low down for me at little more than 24 degrees but I hope to try this one next year, as I can't be bothered to get up in the night.

Alan

I had a 115mm advertised as the same 6-7 years ago but as far as I can recall several changes have been made to new model though I feel this is mainly in the area of the focuser, the objective in the one I had here was good, very good in fact, good value I would say.

Alan

50 minutes ago, grjsk said:

Wow, I'm jealous, I haven't had a clear night since october 7th..

I would be happy for you to have a few of my clear nights if you could send some rain, grass is yellow and gave up growing weeks back.

Alan

Staggeringly good, only word I could come up with that hadn't been used, so much detail in there, excellent job!!

Alan

24 minutes ago, vlaiv said:

Only issue I have here at the moment is that there is quite a bit of fog in the evening - high humidity and probably high air pressure. With LP, I can hardly make out Orion's belt in the evening. Don't know why is it so humid - we haven't had rain in quite a while.

That is just because I use yr.no as my weather provider - they give forecast for much of Europe and are precise enough

I use the same YR no, we get fog but it only develops around 4 in the morning, skies here are superb, with a touch of wind and after rain they are as good as I have seen anywhere and I have traveled a lot. I too like you wonder where the fog comes from as we had 43 clear nights and days then a bit of rain for two days and now this 16 night run.

Alan 

35 minutes ago, vlaiv said:

Over here it's been quite interesting 25-26C + during the day. We had warmest October day in past 60+ years couple a days ago with temperatures over 28C.

Heating season starts around 15th of October (for those on remote / central heating) and most people that do their own heating start even earlier than that - second week of October. Average daily temperature for October here is about 12.4C. Last two weeks we did not get down to that temperature even in the early mornings. It's also much drier than usual.

Warm weather will apparently continue until beginning of the next weak.

Btw, I'm also currently in my shorts

 

Vlaiv, we have had another 16 clear nights on the trot and 29-32 every day, we will pay for this I'm sure, clear again tonigh and tomorrow.

Alan

Now that's very nice indeed Knobby, I want to shoot this but I need to change scopes over, I feel the Borg at 330mm and the 183mc will get it all in.

Alan

I thought it was more in line with keeping the weight as far inboard as possible, I tend to use as few as possible though.

Alan

I would go for the Duo as it is what I intend to do myself, the Optolong has the better band pass from what I am told as ZWO have now brought their own to the marketplace. There is nothing wrong with using a DSLR, I have done for two years and got some nice results. Some of the other members on here have really turned out some stunning images with DSLR's, making mine look poor.

Maybe someone else will advise on a single clip on filter though It is something that didn't try and know little about, I do like the advertising of these duo band filters though.

Alan

Now after the star has been fixed I prefer this, that star would drive me mad, as they seem to you as you crop them out, if I go mono with a 1600 I would have to learn that fix.

Alan

Two really lovely images there and they look fine together. I asked a while back about mosaics and one member said there were easy in a software the name of which I have forgotten, it was one that many use though, but I don't have.

Alan 

I prefer the KAF 8300 image as it handle the bright star so much better, both are really good images but for me the bottom one steals the show.

Alan

Just now, vlaiv said:

Yes, gain is the issue.

Here is comparison of the information from fits header for darks and lights:

Darks were taken with gain 0 and lights were taken with with gain 90.

There is slight mismatch between flats and flat darks in temperature. In all likelihood it will not make much difference, but I would recommend you following:

- Take new set of darks at Gain 90 and try with those to calibrate your image

- In future make sure that you take flats / flat darks at the same temperature

- it would be best to have some settings that you will not change - offset, gain and temperature and always work on those. Offset of 65 seems fine - so keep it there, gain 90 is unity gain so again fine - keep it there and -5C looks like reasonable temperature that you can reach most of the time, so that is also something you should keep. Take all of your subs with these settings.

 

Idle hands have done the devils work yet again, look many thanks for sorting this out for me, I was clueless as to this affecting anything, I must learn to do thing at exactly the same gain etc. So in view of the fact Darks can be done now then I must take another set at 90 Gain and label them as such and stop messing. As the camera is not moved I can keep the others for zero gain subs, I am sure I will take some, grouping is the key.

Alan

1 hour ago, Skyline said:

I did try this one a few years ago, but its low in my location, and the seeing was terrible. I think at that time I only got a few subs off with an outline of the main nebula.

Yours is a good attempt, especially as the faint outer ring is starting to show.

N.

It was more a half hearted go at it, I can get more subs but with it being low the guiding is far from good, there are a few subs in the post od NGC 7293 that are not round, the time I tend to shoot the sky it always active, even though in that direction I have basically no light until Greece, so LP is not an issue.

Maybe add some subs to this and at least try and make it good.

Alan

44 minutes ago, tooth_dr said:

APT flats assist is pretty essential! I use it for my CCD flats.

1) choose a ADU you want

2) choose an acceptable range outside of that ADU eg 5%

3) select starting exposure time and max exposure

4) APT will take a number of exposures until it finds an exposure that delivers the correct ADU.

5) It then sets up an image run in the flats section

HTH

Adam 

 

Thanks Adam, does it now, I was wondering what that is, what do you do with it? I don't recall having problems in the first 3-4 images I took, this will be idle hands again I can feel it.

Alan

1 hour ago, vlaiv said:

There might be an issue with APT and the way it shoots flats - but I can't help there as I'm not using it (or have ever).

What I can do is offer you list of reasons why this can happen so you can check if anything on that list is causing issue for you.

You have under correction of the flats. Corrected value is equal to base value divided by flat value. For that number to be lower than it should, we have two options:

1. base value is lower than it should be

2. flat value is higher than it should be

Usually this happens with wrong calibration or if there is some sort of light leak in the system.

Case one can happen if you have:

mismatching darks for your lights - longer duration darks, shot at higher gain, shot at higher temperature, or there were light leak while you shot your darks (but not with lights) - i.e. You did darks on scope during the day, or you took your camera off scope and did darks and there was either IR leak, or regular light leak (cap was not good enough at blocking the light).

Case two can happen if you have:

mismatching flat darks - shorter than flats, at lower gain or at lower temperature. Light leak while shooting flats can also be a problem. People sometimes calibrate flats with bias only - again that can be a problem.

If you can post one of each: light, dark, flat and flat dark subs, we could possibly be able to tell what happened by examining fits header for information and doing measurements on each.

 

 

No light leak of this I am 100% sure. Same temperature which was about 23 degrees , does the camera need to be cooled to minus 5 like the lights.

Darks were shot cooled to minus 5.

I am wondeing if Gain here is the issue, I think the Darks could be at zero gain.

Am I correct in believing Gain has to be the same on all shots Light, darks etc etc. All frames are Fits I will try to post as I don't know how to change them apart from after stacking in DSS.

Dark

D_2019-10-12_10-38-13.fit

Flat

F_2019-10-19_18-43-38.fit

Dark Flat don't take notice of the F at the front

F_2019-10-19_18-48-51.fit

Light of M33 short last night gain 90 offset 65, I can't recall if the Darks were at this, I think they were. Feel I best not touch anything in future.

L_2019-10-19_20-39-35.fit

Thanks for the advice.

Alan

This is something I didn't have much of an issue with before when using the Canon, just set 400iso and banged away 25 or so shots at 1-2 seconds with a clean pair of Sloggies over the dew shield and light box. Then covering up and shooting Dark Flats the same values. Never had a problem.

Now for whatever reason I am seeing fairly large and not nice dust blotches on stacked results. I use APT and normally set about 1 or 2 seconds and cover with either a double layer T shirt or similar, then use my light box. I do not understand what APT's Flats CCD assist is meant to do or how it works.

I have now taken 3 sets and the problem still appears there even though I have not moved the camera at all.

I have stretched this a bit more from yesterday so people can see what I mean, can anyone give advice to stop this as I am losing faint detail hiding the problem.

Thank you in advance,

Alan