Gina

OIII integration auto-stretched in PI.

C-CS adapter has arrived so I can try setting the focus "screw-wise". Getting such good focus over most of the field was pure luck yesterday as I only slid the lens in and out of the adapter that is used to align it with the camera! BUT it isn't in focus over the whole field and that's what's needed. I assume the lens must be tilted in spite of the adapter. Strange thing is that the field looks perfectly flat over more than half the image then seemingly suddenly bends away. Weird! What I omitted to try last night was to remove the dome and see what difference it made. Maybe I should try that first before moving the lens. Trouble is, I can only test this on a clear night with lots of clear stars - it just isn't possible to test the focus in daytime. I tried it yesterday on distant trees and couldn't tell. Again today the visibility is too poor to focus clearly at a large distance.

Very interesting and shows the problems I've had with LinearFit. This new version looks like it should do the job

Yes indeed. I was surprised to see rings instead of dots for the Ha 5nm indicating it's out of focus - I did think they would be parfocal so didn't check. Might be clear again tonight so I'll have another go and refocus. I too have been thinking about how to correct for variation in intensity and contrast when subtracting images. This is undoubtedly going to be tricky. Yes, the images must remain linear but I agree will most likely need matching in both intensity level (offset) and contrast (multiplier). There is supposed to be a PI function to do just this for matching up RGB images but I don't think I'll rely on that as previous usage has not proved very good on RGB. Forget what it's called ATM - PI naming doesn't quite match my logic Once I have good focus on both sets of images I plan to take the integrated images, match using StarAlignment then play with PixelMath to try to match them up. I think this is going to be interesting

I used a QHY 5II but I too found it very noisy! I can unreservedly recommend the ZWO CMOS cameras - sensitive and low noise. For DSO imaging with NB filters and mono camera, you do need cooling though.

I'll leave the imaging system taking OIII 60s subs overnight (what's left of it) and go to bed. I'll process the OIII and play with the Ha star removal and subtraction tomorrow (later today actually). Night all

Full resolution versions. Both are the integration of 98 60s subs, gain 600, -30C.

Here's a screenshot of the two integrated sets in PI. Plus same histogram stretched.

Now processing the two sets of Ha subs. Blink rejection of duff frames and calibration done and now registering.

The new lens is producing such a bright image that only 10s exposures are required Here's another screenshot of KStars FITS Viewer with a touch of curves applied in GIMP. Cropped to image area.

Sky still clear

Well there's not a lot of OIII in Orion! Just the stars and M42, and some in the Rosette but can't see much else. This seems to be a general thing - so much more Ha than anything else. I don't think there's much point in increasing exposure.

No sign or the Eridanus Loop so I've gone back to Orion. Finishing off the Ha 3nm subs - to reach 100 and then I'll probably go over to OIII. Doubt there'll be enough time to take anything else on Orion before it slips below the horizon.

I've moved over to Eridanus looking for the Loop but can't see anything with 60s exposure so I'm trying 120s.

I agree - on both points The Rosette Nebula near the top of the frame is supposed to have lots of NII yet doesn't show it in these subs. There are so many things I want to image that choosing is rather difficult

Thank you I'll see if I can find the info about the dome and yes, I'm quite happy to share my 3D printed parts designs. The filament is ABS.

I've captured 50 or 60 odd subs in Ha 3nm and now capturing in Ha 5nm. Here are 2 subs, one 3nm and one 5nm captured one after the other with just a few seconds (to change filter) in between, displayed side by side in PixInsight. The Ha 5nm filter is labelled "R" (that was where the Red filter was when I did RGB). Most odf the DSOs look the same in both except the Angelfish which looks a little brighter in 5nm so maybe that has significant NII. Otherwise the main difference is in the stars.

Now that the sky has cleared considerably I can see that this lens gives nice even illumination across the whole image - the little ZWO lens had a serious variation. There is a problem with the LHS of this image - roughly north - which appears to be image tilt. I shall investigate. There is something wrong with the RPi control of both dew heaters and cooling - neither are working. Just something not connected I would think. The camera is running at +12C with an ambient of about -2C and there's no dew heating other than the heat being produced by the electronics and camera. So far no sign of dew. Yes, I do have the dome on

Most of the clouds have gone away

Another capture.

Much better

So far so good - Orion is pretty clear

I don't know how long Orion is going to be visible - there's cloud about.

This lens is certainly much better than the little 2.5mm ZWO fisheye. Seems faster This is 10s exposure with gain of 350 and Gamma at 10.

All assembled and focused manually to the best of my ability and then some ie. a lot of luck. I need the C-CS adapter so that I have finer focus. Here is the very first image of this version hung on the guttering. Not orientated - just poked out there to test