MartinB

Great stuff, glad you are sorted.

You need to create an OIII copy so you have 2 distinct OIII images. The images need to be greyscale and must be exactly the same dimensions. The go to channels and select merge.

I got this wedge second hand in 2006 and I remember that when I received it had a similar problem to yours. I spoke to the guy I bought it from and he also said he hadn't used it for a couple of years. The problem was that the plastic/teflon material between the base plates of the mount which allows rotation had perished. It was a very easy fix, I simply replaced it with a new plastic sheet (from a large margerine tub iirc!). Worked a treat. I sold the wedge on many years ago but it was a lovely piece of kit.

Oh wow! Fist pumping 100% appropriate. Both images are superb but the wide field has been put in my "sublime" category. Well done indeed!

Well, I am currently considering getting another camera set up for my observatory to use with my Tak fsq. It will almost certainly e anASI 1600mm. If the asi2600 was available in mono I would definitely consider it, but no way will I go back to Osc. Regarding exposure times the choice is yours! I have been very satisfied with 300 sec subs for NB and my data indicates that, with my sky, I am above read noise threshold. I might change to 600 secs because the large number of subs can be a pain (with simeis-147 I had 31 hours worth to contend with!). With my ccd I need 30 min (1 hour would probably be better still) and this is a real pain, any wisp of cloud destroys the sub. My ccd camera has a very high QE and, of course is 16bit, but none of this seems to make any difference when it comes to real world data, the asi is the better performer. The main advantage of ccd is that you can do "proper" binning and use bias frames during calibration. Being able to bin colour data when lrgb imaging at longer focal lengths is a big plus for ccd.

In my experience, having done a fair bit of imaging with both types of camera, mono cameras gather data more effeciently (require less time to achieve a given SNR), and are more flexible than osc. The main issue is one of expence.

I use a combination of PS and Photoshop. One thing to consider is the amount of internet support available. There are loads of great youtube videos out there for PI and PS. Also, do you do a lot of daytime photography or widefield nightime DSLR stuff? If so Lightroom which comes with the CC package is very powerful. From what I can gather Affinity Photo is pretty much on a par with PS but will probably work out cheaper in the long run. Gimp is much updated software, free and with plenty of tutorials on YouTube.

One thing to remember is that people who are imaging with 3nm filters are investing huge quantities of money into their imaging. Their other kit is also likely to be high end and they are likely to have a zero compromise approach when it comes to their imaging. Each channel will be given many hours of total exposure and a good strategy when doing this is to collect Ha when there is a significant moon and OIII when the moon isn't an issue. The solar reflection from the moon will affect OIII images more than Ha. For less high brow imaging an OIII filter will perform surprisingly well even with quite a large moon provided you aren't pointing too close. Yes, you will have more background sky brightness and less contrast but for cutting your teeth NB imaging teeth you will be fine.

If there is any drift, and there always is , then making dec adjustments one direction only (in the direction that pushes against the drift) should work very well. Also have the RA slightly out of true balance, weighted to the east so that the motor is pushing against the gear and properly in contact.

I still haven't done an imaging run in anger yet but lots of hassle free observing. A friend is currently using the mount whilst he gets his HEQ5 repaired. When I get it back I will send some pics re reducing backlash. Backlash shouldn't be an issue if you aren't guiding. It is worth having the RA axis slightly heavier the east side to ensure the RA gear stays well meshed. I haven't done pec training.

Haha, yes, that's the other form of bias that needs needs calibrating out!

Apparently monitor characteristics change over time and the Spyder default recommendation is to refresh the calibration every month. It pops up a reminder. Fortunately the refresh routine is much quicker than initial full one. Of course, it's one thing to have an immaculate calibration, and very worthwhile, but quite another to expect people viewing your images to be seeing them as you intended!!

There is so much to think about and some of the questions you are posing will generate conflicting views! If you are prepared to fund the additional cost of a motorised filter wheel and filters then my personal view is that mono is a more effective and flexible way to image. That opinion is based not just on theory but also practical experience of using both types of camera. With regard to pixel size and sampling rate, my experience is that my seeing conditions rarely let me get close to the theoretical sampling rate of my ASI 1600. Obviously seeing is site dependent but on good deep sky imaging nights, with a transparent sky my stars are twinkling! I think the optimum sampling rates people bandy about are ideal for cloud cuckoo land! I have been absolutely delighted with my ASI 1600 and use it with a 200mm lens and a Tak FSQ106. Here is an example with the 200mm lens (sampling rate 3.92 arc secs/ pixel) I think a ZS61 and an ASI 1600 MM Pro would be an outstanding combination.

Looking on my laptop now, and yes, the latest version has pulled out the faint OIII nebulosity and the Ha colour looks great. I was interested to hear that the PI gurus were suggesting that you should stretch each channel before doing the combine. I stretch in PS but the principles are the same. It makes sense to do an optimal stretch for each channel separately and then combine and I've certainly tried this plenty of times. Certainly combining at the linear stage and then boosting OIII and SII to match the Ha permaturely can trash the Ha. However, gradually bringing the histograms to a balance giving the Ha a reasonable stretch before they are fully matched does give you a great deal of control over the final colour balance at the different brightness levels. Using the autostretch in PI for each channel definitely doesn't work very well! However you went about it, it has worked like an absolute dream. This is a cracking image.

I'm only looking on my phone at the mo. The ha seems a better colour and their is some nice OIII in the background so, overall I would say better. Will have a look on my calibrated monitor tomorrow.