Rustang

17 minutes ago, geeklee said:

Yeah, it's frustrating and I sympathise.  When I saw your thread title, I knew exactly what you meant!  I find the lack of clear nights exacerbates that feeling of urgency/frustration for issues that require testing.  All you can do next time out is have a plan - try the tools suggested in Apt first, maybe get it bang on according to the Bahtinov Aid, then check using the Focus Aid as a reference, take a frame or two and check them zoomed in etc.  If you're happier all good, if not, start to tweak the focus through the zone and keep checking the frames.  Ensure to check back with temp changes or just every 30/60 mins maybe (I like to focus on filter change too)

Yeah it's a frustrating struggle, I hate that I've lost a good set of data as well but I now need to be a bit more thorough and don't just assume things are ok, we live and learn 👍

1 hour ago, geeklee said:

Sorry, I don't.  It will only be testing out of focus, in focus, out of focus and back will you see the best values.  One thing I noticed is the screen view and peak value looking like 8bit, in the Apt manual it says you have to switch to 1:1 preview mode to use the raw FITS data for calculation.  Just double click the image to get this 1:1 view.

https://astrophotography.app/usersguide/focusing_aid.htm

No worries, l have a try. I would rather be getting on with improving other aspects of the hobby but never mind. I'm a bit embarrassed it's looking like user error though after all this time but strange that I've always just eye balled it and been ok, still I would rather that then it be an issue with the scope. 

1 hour ago, BrendanC said:

I gave up on APT's focus on tools and now use the standalone Bahtinov Grabber tool which, although APT's version is based on it, is actually much easier to use and more reliable. 

Thanks, il look into that. 

17 minutes ago, geeklee said:

Apt has another tool that lets you put a box over an area and get x3, x5 and maybe something higher (I think I have that right but am going off memory)

The Bahtinov Aid is worth using and those spikes look clear. The WO masks with the clear material do seem to create bright spikes. 

yeah it was nice to use, I will give it another go using any APT aids I can and try and get it better. Do you know what values mentioned above are low enough for good focus so I can use that also to help check through the night?

17 minutes ago, Astro Noodles said:

Hi Rustang. Which star did you use for focusing? It wasn't a double star was it?

Nope, Polaris! I should probably use a brighter star to see the spikes better! 

Thanks guys, purhaps my eye isant as good as I thought if two of you think it's out. I used Polaris, just been lazy but I've used it many times and my images have been sharper. I don't have the option to zoom in anymore as it's a CCD camera. I've not used the APT bahtinov mask so could try that to improve on. It's still strange as I've always just eye balled it, but I guess I've got it wrong this time I guess, maybe I should book an appointment at Spec Savers! 😁

It seems this is the case with lots of aspects of this hobby! I really wish one thing would just stay working so I could concentrate of all the other things to improve on. Anyway I thought it would be easier to start a new thread in regards to this issue. I have since day one of starting out doing astrophotography, used a bahtinov mask to focus. Ok so there might still be room to improve of focus but until now Ive been ok with the focus of my images. I now have a knew scope, WOZ73 with a built in B mask in the lens hood. First light on Friday just gone, took my time with the mask to focus, got focus and started imaging (see image below). Because I have always done this and its been fine, the stars appeard the size I'm used to seeing so I just carried on. Its not until you start to zoom in you can see that its not in focus. I took an image straight after the mask was removed and that is out of focus when you zoom in and contiunes to be that way through all of my data. So why? should I be worried about Collimation of the new scope? what else could it be? I know lots of people use a mask and get on just fine. Valv has mentioned about using the FWHM of HFD values on the APT focus aid, from his help and info I know the figures fluctuate and they need to be small but I dont know how small to know I'm in good focus. I have attached below 3 subs that I opened in APT and opened the focused aid on them, they have different sets of numbers so are any of them showing good focus or not? if they are then that's probably not good I guess and could still mean an issue with the scope!?

17 minutes ago, vlaiv said:

I don think it is much worse than doing it with B mask, is it? I mean principle is the same - except you look at the numbers instead of spike pattern.

As for B mask precision, well, I'm not an expert, or to put it more precisely - I have almost 0 knowledge and experience with it   Used it couple of times, saw that I don't get good focus and decided not to use it anymore. Have two of them gathering dust (one for each imaging scope).

I've just looked at a sub in APT with the focus aid, I know you said the values will change but low numbers are good, these seem low but are they low enough!? 

8 minutes ago, vlaiv said:

I don think it is much worse than doing it with B mask, is it? I mean principle is the same - except you look at the numbers instead of spike pattern.

As for B mask precision, well, I'm not an expert, or to put it more precisely - I have almost 0 knowledge and experience with it   Used it couple of times, saw that I don't get good focus and decided not to use it anymore. Have two of them gathering dust (one for each imaging scope).

Yeah your probably right, my brain is just hesitant with change! The image below is where I thought I had achieved good focus, I think I'm right in saying that it should have been ok going off those spikes patterns but it's failed somewhere. One step forward, one step back! 😔

2 hours ago, Pete Presland said:

It's great to see the Milky Way again, i had similar views from North Norfolk a couple of weeks ago. What a crying shame it is that society has become obsessed with illuminating the world into "perma daylight". Weybourne had streetlights, but they lit the street. The big difference for me was the absence of illuminatd buisneses, carparks, shope fronts, factories........ Incredible to think how much money is wasted as well!

Been thinking about a short break in the winter maybe somewhere, only thing that puts me off is the weather.

Yeah it seems the only hobby where we have to wait, and wait, and wait sometimes! It gets really frustrating especially with imaging when you just wont to make some tweaks to improve but again, you just have to wait for that next clear night, you cant just get up the next day and improve straight away. I would definitely be booking some breaks under dark skies as much as possible but as you say, you just cant predict the weather so haven't bothered yet.

Just now, vlaiv said:

I don't use APT, but here is APT help file section that describes focus aid tool:

https://astrophotography.app/usersguide/focusing_aid.htm#

It shows both FWHM and HFR values.

You should not look for particular values in either - they are both relative, and smallest value indicates best focus, but it will change from session to session as it depends on both seeing and guiding performance.

Idea behind using those is to use short frame & focus exposures (but make them at least 2-3 seconds long in order for seeing to average enough) and monitor values. Tweak focus until you get the lowest number. Numbers will change each time you make focus adjustment and you need to change focus until you get lowest values (that will include going "thru" actual focus position once or twice as you need to verify that numbers first fall and then start to rise once you go thru the actual focus position - pretty much like focusing visually - you rack focuser in/out until you are certain you have the sharpest view).

 I see, sounds like a lot of faff but I have just seen that where Ive gotten away with just using the focus mask before (probably could have still been improved) It now doesn't seem to be the case.  Ive just looked at the subs where I was achieving focus on the last session and its not great. The last sub with the mask was good,  the sub straight after with the mask removed, when zoomed in is not in focus, I missed this and so every Ha sub after is out, my bad but can the focus mask be that out when Ive never had it that bad before!?

6 minutes ago, vlaiv said:

If you want to search for progressing defocus - just visually compare first and last sub of the evening.

First sub should have tight stars and last one should have stars as in above image. Difference should be obvious.

Apologies, I meant what values to look out for when imaging, I use APT so is there away of checking values in that software?

24 minutes ago, vlaiv said:

Yes. Check individual subs to see if there is progression in defocus.

As telescope cools down - tube gets shorter because things shrink at lower temperature. If there was rapid temperature change during imaging session and you did not refocus (people usually just focus on the beginning of the session) - it can lead to loss of focus over time.

Another possibility is that scope was not properly cooled when you focused - if you focused at the beginning quickly after putting the scope on the mount and that it cooled before you started imaging.

Third option is simply - poor judgement of bahtinov mask pattern. I don't use B mask at all as I've found that I can't reliably tell if I have good focus with it or not. It is far easier to just check stars on computer screen and look at FWHM / HFR values.

Thanks, what values should I be seeing!? Ive always done it the lazy way so guilty on that one but Ive not had an image that to me has seemed as out of focus as above before.

5 minutes ago, vlaiv said:

Yes, it does look like little bit out of the focus. You can see that on fainter stars - they are also like little discs rather than stars. Bright stars can appear disc like due to stretch - but faint ones should be pin point like - and they are not - they look like small circles.

Il will try and see what's going on then as I really took my time with the focus mask so can't think what's happened, maybe focus slip on the scope. Can there be anything else going on if the mask is good but the image is still out of focus? 

5 minutes ago, vlaiv said:

Quite strange - I mean vignetting affects light that comes in thru the aperture of telescope - regardless if it comes from the stars or flat panel.

You should see it both in your flats (as you do) - but also in your uncalibrated lights.

Its definitely strange. I think I have seen it on the lights but will have to go back and check but there's obviously no sign on this recent stack of just lights. Do you also confirm the above images are a little out of focus? When you zoom in it dies seem like the stars go a little blury quicker than normal but as I say the b mask was good and it's now a threaded connection from camera to scope. 

7 minutes ago, vlaiv said:

That is interesting.

Did you change focus position between flats and lights maybe? Change in focus position can lead to vignetting - but it usually requires racking focuser further out.

What do you use for flat source?

 

I use an LED drawing pad and paper. The focus between filters is the same so never moved it

41 minutes ago, vlaiv said:

What do your flats look like?

1 hour ago, vlaiv said:

 

The original flats had vignetting 

41 minutes ago, vlaiv said:

Different FF/FRs have different amount of vignetting and if you changed that component of optical train - then yes, level of vignetting will change.

I've just done a test with the last data from my original setup, stacked with no calibration frames and there's no vignetting either!? 🤔 

So I had my first light with the WOZ73 Friday night. I also took the opportunity to push on to my first ever 20min long subs which Ive been recommended to do by a few people as I believe my particular camera (QHY-9) is better for it and that definitely seems so.

Ive attached a J peg and Tiff of a quickly processed 2hr 20 min stack with NO calibrations frames and the results are interesting and also concerning. I'm really pleased that it looks like 20 min long subs have really brought the noise down, there's a big difference which is great. What is very strange though is that the stack has no Vignetting which Ive had to put up with for so long and thought it was down to the 1:25th filters either not being big enough or close enough to the sensor.

So what's happened to cause no vignetting, the scope has changed obviously and now uses a dedicated WO flattener so could it have been the Altair x80 reducer I was using on the SW80 ED DS PRO? or was it the calibration frames going wrong?

The attached images without any calibration frames seem much better than any of my past images with this camera and filter combo in regards to vignetting so I have no idea what has been going on. Is it also possible for calibration frames to add noise if not correct!?

In regards to the image on the whole I'm really pleased, the stars are bright but i didn't do much to protect them in the quick process but they appear nice and round and not to bad in the corners so the flattener appears pretty good in regards to its distance from the sensor. I'm a little disappointed in regards to sharpness though, the B mask was spot on but its definitely soft so I need to see whats happened there.

20minSubteststretch.tif

9 hours ago, Floater said:

Guessing you didn’t take the scope? But obviously enjoyed the dark …

I took a visual scope and we had a look at Jupiter and Saturn which is always a pleasure, my Sister in law and wife really enjoyed that. I also took my Canon 600D and camera tripod and took a few shots of the Milky way at 50mm. I'm not expecting much as I don't have a small tracking mount so I was only at 5 sec subs but you can see it so there might be an ok photo in there somewhere, il do it properly one day. But out off all of it, just looking up was a real treat 😊

Yeah pretty amazing. We were in Lamyatt near Castle Cary, its where my wife's family is. Now on our way back to Bortle 6 skies in Hertfordshire 😔

So last night I was under Bortle 4 skies in Somerset and for the first time I'm pretty sure I could see the faint strip of the Milky way across the sky which was pretty amazing to be honest. While staring up in amazement I also witnessed 3 nice Meteors so it was a great visual night 😊

Hello, not to far from me! 😊

Just think of the observatory I could have here, complete 360 views 😊

Well last night at home went well for the WO Z73's first light. I managed a good 2hrs on the Crescent nebula in between clouds. I've finally pushed on to my first 20min subs and the mount seemed ok with it. Looking forward to the possibility of a visual session under Bortle 4 skies tonight and possibly some basic milkyway shots.