Adreneline

Thank you. The PS Action I used was from Annie's Astro Actions; Straton is stand-alone Windows software. HTH

Really like the starless image. We go to a great deal of trouble to image nebula and sometimes I feel the stars kind of get in the way of appreciating the beauty of the very thing we are trying to image! I would be interested to know which method you used to remove the stars; so far I've used PS Actions and Straton with some success. Thanks for sharing. Adrian

Sorry about that - it's getting late and I wasn't concentrating on what you wrote regarding the flats. You can take darks at any convenient time as long as they are at the same temperature, exposure, gain and offset. Complete darkness is essential. People often use the sensor cover supplied with the camera; some advocate wrapping it in tin-foil. The considered view is poor darks introduce more problems than they solve. I guess you can say the same for any calibration frame! I usually take my flats the following morning - I'm usually too tired to do it at the end of an imaging session. I can't see it being an issue providing you don't disturb the imaging train at all. If dust bunnies move they can often be reduced during processing. The flats will really help with the vignetting. You should take the dark-flats at the same time but with the lens cap on. It's all going in the right direction and looking good! Apologies again for not registering the lack of flats and darks. Adrian

Hi David, Well I've had a go. On the positive side this is a really well framed image of M101. I would say you have definitely improved the focus issues you were experiencing. Don't forget that achievable absolute FWHM is dependent on so many things and trying to achieve some magic low value on any given night is pointless. In my view you need to achieve the lowest value you can for a given filter - they will all vary. With my ED80DS I find that blue never focusses as well as red, green or luminance. Many of my rgb images suffer from blue bloat around the stars. On the negative side the flats are clearly not doing what they should be doing as all the masters exhibit severe vignetting and evidence of dust bunnies; I would suggest the latter are on the filters as they move from filter to filter. Having said that I have done my best (I'm sure others could do better) to reduce the effect of vignetting and dust bunnies as much as possible, probably at the expense of some of the outer arms of M101. I've processed pretty much as before but this time I also used the Luminance image as a 'Lighten' layer in Photoshop at about 45% opacity. Can you post one of the master flats - anyone - so I can have a look please. HTH Adrian

Will certainly take a look and get back to you later/tomorrow.

Good luck David! Hope you get some good results tonight; not easy on these short nights when Mr Moon is up and about but it's still a good opportunity to sort out a few niggling issues and problems. Next time I get my gear out I will be sure to screenshot the focussing results I get with SharpCap for comparison. Looking forward to seeing the results of tonights endeavours! Adrian

From purely personal experience I have found SGP hdr focussing not to yield good or consistent results. I have wasted so much time trying to get autofocus to work that I now focus manually, albeit with a stepper motor focus unit - I go and stand outside and use SharpCap on a laptop - five minutes (if that) and I'm done. As for SharpCap I've decided £10 year is money well spent; it is constantly being updated and improved. I use both the FWHM Measurement and Bahtinov Mask options and find I get very good results. Solving problems is all part of the fun! Not sure you ever reach the point where you've solved 'em all though! Good luck. Adrian

Hi David, I've used a BM with and without success. I've recently started using SharpCap (£10 per year) to help me focus with a preference for FWHM measurements but success depends on so many things, including the 'seeing'. I do pretty much the same but I have had more success using a uniform light source; I use my iPad running a lightbox type app and get very consistent results; the flats also work! Well done you! I'd be happy to have that average over an imaging session. tiff is just fine but I wonder whether it is DSS that decided to save as rgb rather than greyscale. I presume you have checked it is expecting to process mono images - it's in one of the Settings menus somewhere - can't exactly remember where though. As for the artefacts I'm really not sure what to say - it doesn't look like dew to me. It may be the flats just not doing their job properly. Another thing I would say is that the advice seems to be not to use Bias with a ASI1600 Pro. Rightly or wrongly (but it seems to work for me) I've started using flats + dark + dark-flats (instead of bias). If I'm doing something very wrong then hopefully someone will pop up and put me straight! Dark-flats are exposures taken with exactly the same exposure times as the corresponding flats but with the lens cap on - hence dark! You can use them in DSS. I would have another bash at taking your flats. I know dust bunnies may have moved but it might correct the vignetting problems you are experiencing. People use a variety of white light panels; I tried using one of the Huion panels but found it gave me severe 'banding' when used with both my dslr and ccd's so I gave up. HTH Adrian

Hi Brian, A really nice image; love the framing and I especially like the blues in the core region. NGC7023 is one of my favourite objects to image although my past efforts have hardly done it justice. I hate to be critical but there seem to be some strange 'linear' bands extending from the top of the image down toward the bottom; they are especially noticable on the left of the core. It's almost as if they are radial and the centre is way off to the top of the image. It might be my MacBook display or my eyes! I've looked at a few other images (e.g. APOD) to see if I can see the same thing but no joy. I am afraid I have no idea what might be causing them and unless someone else points them out maybe it is just me. Thanks for sharing. Adrian

Well I managed to get something for you although I'm sure those with more expertise could achieve far better. All the individual masters were rgb so I converted them to greyscale. I haven't used the Luminance master. I took them into PixInsight, cropped the vignetting (not sure the flats are doing the best job for you) and then applied AutomaticBackgroundExtraction (ABE) twice, once as subtraction and then as division. I then created a luminance mask and applied some noise reduction. I then duplicated the image and to one I applied incremental/multiple HistogramTransformation (HT) and the other I applied an ArcSinhStretch. I took the resulting images into Photoshop and layered the HT image over the ArcSinh image as a lighten layer with about 40% opacity. Finally I applied a little bit of extra noise reduction. You can definitely tell it is M81! Maybe the focus could be a bit tighter and there are a few artifacts on the masters I don't understand (especially the red for some reason) but hey! - you got a pretty good first image hiding in amongst all that data. HTH Adrian P.S. May I ask how you are taking your flats?

I always use it wide open. I have found the spacing is absolutely critical using it at f2; the slightest issue on spacing and it won't focus.

I'll have to give it a go with my 1.25" filters and wheel. Thank you!

Very nice image. NGC7000 is on my list to have a go at with the 135mm + ASI1600. I don't have any 2" rgb filters though! Adrian

Thank you for your kind comments. I can certainly give you all the details if you would like them. Essentially it is a based around a NEMA 17 stepper motor and drive unit all driven by an Arduino Uno along with a rotary encoder. The belt is from MotionCo as is the toothed pulley. The tube rings are from TS Optics. I should point out my programming days are long, long over - I'm too old to learn those sort of new tricks! - so all I did was adapt some existing code (I didn't need a digital display but you can leave that code in place as it makes no difference) and housed the Uno + stepper control unit in a weather proof box. The system is entirely manual and is not USB, ASCOM or anything else clever. I focus at the start of an imaging session by going outside and focussing the 135mm using SharpCap (on my laptop) and sometimes/rarely an external Bahtinov mask. I have found the Samyang focus never changes during an imaging session. I rarely do more than one filter per session but even when I do the focus seems to be the same for all filters - maybe I'm lucky! I don't have the luxury of a permanent setup. It takes me typically 15 minutes to be setup and running, including polar alignment and then maybe another 5 minutes to make sure the focus is as good as I can get it. It takes 15 minutes to strip down and most of that is waiting for the camera to warm up! The dual mount lets me replace the Samyang with either my ED80 or ZS71 but I tend to prefer the wide field imaging these days. HTH If you need more detail on specifics just ask.

Couldn't resist adding some SII; out of 35 lights taken 23 were spoilt by clouds and aircraft on approach to EMA (Arghh!). I find it really difficult to get the colour balance right with the Hubble Palette so any tips or help would be much appreciated. Ha, OIII and SII masters were all 'balanced' using LinearFit in PI and then combined using Annie's Astro Actions in PS. Resulting magenta halos were removed in PI followed by a final colour balance in PS to try to align the histograms. Thanks for looking.