ollypenrice

Since the imaging is now done with a robotic setup based here, I've decided on a marriage between our 14 inch Meade SCT tube assembly and our venerable Mesu 200 mount, to have a great visual observing setup. The LX200 Alt-Az mount is handy but wobbly and has now started acting the goat electronically. It's over 20 years old and I think that, even if I fixed it this time, it would most likely act up again. This is no good in my circumstances. Stuff has to work. The Mesu observatory is small for visual but the SCT is nice and short. We'll lose the convenience of alt-az but gain the convenience of a Moonlite Crayford which we can't use on the fork mount for fear of collision. So, Mesu, do you take this 14 inch SCT to be your lawful wedded wife? We'll find out when the Losmandy dovetail for the Meade arrives and I've de-forked it. (Nearly 300 euros for a dovetail? Better than over 1,100 euros for two tube rings. Not a misprint!) Olly

I must say that I thought the lens could hardly have done better. It was one of the first things I did with it, having bought it second hand. And, yes, I should do a bit more like it with foreground interest, as you say. Olly

This was with a Canon 250D and the 100-400 L series zoom, hand held but braced against the side of the house and simply autofocused. Cropped heavily as it is here, it nicely fills the frame of the PC at full size (1:1). Olly

I'm in this game at the moment as well. The problem - in part - is that the design of the Meade fork has remained variable throughout its life. The first one I did was not like the present one. Regarding the drawers, on mine at least, it's a simple question of welly... Olly

It is, but the problem for the broadband imager is that it's pretty much a monochromatic red field. Olly

Good point. I didn't realize that the Meade and Celestron flat field scopes differed in this way. If the moving mirror and Celestron's focus motor work as well on the Edge as they do on the RASA then there should be no problem. Olly

If the Edge does not have a moving field flattener element then the backfocus will be from the fixed back of the telescope, no? So can you ot lose the 20mm extension? Olly

You have your focuser extended by about 20mm according to the scale. Is this 20mm extension intentional? Olly

Just regarding the idea of using the 535 MC Pro with an 8 inch Edge: even with a 0.7 reducer this would give you an image scale of 0.55"PP. (Do check my sums.) In all probability this means you would be oversampling by at least three times. This doesn't really add up, to my mind. You could have a shorter focal length, a wider field and no loss of real resolution. Olly

Yes, I was pretty sure you'd done that and it worked well. Olly

Very easy to like. I did try this region in HaLRGB but it was very 'Meh.' This narrowband brings it to life. Olly

The second one has slewed into the magentas (too much green removal?) and has lost its naturalness for me. But the first one is great going! I found this target absolute murder to process before turning StarXterminator loose on it. There really are so many bright stars in the field. I think you have a great result. The strong and convincing star colour keeps the character of that bright starfield but keeping their size down has let the galaxy emerge nicely. Olly

Compatibility is explained here for Russ Croman's Noise Xterminator. https://www.rc-astro.com/resources/NoiseXTerminator/index.php I'm always very wary in using noise reduction but this product is astonishingly good and, most importantly, almost invisible. Olly

Yes and, even with the same software, there is sometimes an option in the capture part to save the data in a choice of orientations. If this is inadvertently changed it will disorientate the calibration files. I've had this in Artemis Capture. Oly

I sometimes get visible squares as well though, so far, only in either mosaics or very dense starfields. Have you tried the 'Large Tile' option? Olly

Do the two affected panels show any sign of their green corners if stretched individually? Olly

Good start. Here is the number one key part of stretching and you must get it right. This is your first image with the histogram opened in Photoshop Levels but all processing suites have the same. Look at the bottom left of the graph. There's a gap before the start of the data line. You must move the left hand arrow in at least as far as that flat line before the big peak. But not this far!!! This is the histogram of your re-process and now the peak is jammed up against the left hand side of the graph. This is 'black clipped' meaning you have discarded your faintest data. The sweet spot is between the two. A black clipped image cannot be rescued but your first one can be improved by moving the left hand slider in a little, removing the gap and reducing the flat line without eliminating it. This is, as I say, the number one starting guidiline when stretching. Refinements will follow but this is the basis. Olly

I don't think the video above comes up with the best way of replacing the stars. They are selected by subtracting the starless from the starry to leave the stars. There's a better way. I also think that reducing them by using the minimum filter is very invasive. The method suggested by Xiga here on SGL is, I find, preferable. - Paste the starless on top of the starry. - Invert both images. (Ctrtl I) - Top layer active, change blend mode to divide. - Stamp down. (Ctrl Alt Shift E ) which will give you a top layer. When this is flattened you have your star layer with stars at full intensity. - Paste this star layer on top of the starless and change the blend mode to screen. Now you have the stars on top as they were when you de-starred the image so you haven't necessarily gained anything - yet. But you can reduce them by using Levels and lowering the mid point (Mid point slider to the right.) This simply de-stretches them. If the stars look a bit 'hard' don't be frightened to give them a small Gaussian blur. The million-dollar question comes before all this: At what point do you de-star?. I'm still experimenting, but I don't find the linear stage to be good. I get good results at either a partial stretch or a full stretch. If you go for a partial stretch and then heavily stretch the starless, you can then replace the partially stretched stars and they'll need less de-stretchng (or maybe they'll need none.) Experimantation needed. I certainly suggest you try this method. Olly

The Startravels are certainly cheap and partially cheerful but this is not a Startravel, it s much, much better. You did well. Olly

Small apertures produce large stellar images but using a star removal-replacement tool like StarXterminator can mitigate this very often. The key thing with a camera lens is focus. Some kind of micro-focus device would pay dividends. Olly

If you are using the Samyang at a fast F ratio your dust bunnies may be blurred into insignificance, meaning only your vignetting needs correcting. Gradient removal software is very good at dealing with that. By all means get to the bottom of your flats issue but bear in mind that doing so might not bring a vast benefit. Olly

That's why it remains interesting... Olly

Well, inverse vignetting is certainly straight from the camera is certainly a new problem on here, so far as I can remember. There does seem to be a curse on OIII filters in general. I've had two Astronomik and two Baader and all were poor. Olly

I think it will be possible in PI, presumably by masking all but the over exposed areas and boosting colour saturation in what's left. It's esesntially the same in Photoshop. Just working quickly on the screen grab I made a copy layer, boosted colour saturation on the bottom layer and erased the top selectively. I didn't intend to alter the colour palette overall but forgot I was in the wrong colour space on my PC. My point was just that brightening a region always reduces its colour intensity and vice versa, so whatever method you use, you'll need to up the colour in the bright bits. The proper thing to do in Ps would be to make a copy layer of the original, create a layer mask, copy the original onto it and give this mask a huge contrast boost and blur. Such a mask would be transparent only on the bright regions so boosting the saturation on the top layer would increase the colour only on those regions. Olly

Good reds and blues and good brown dust. I really think this is one target on which you do need to use the high dynamic range technique of blending short exposures for the Trapezium. However, the Trapezium could still be brought under more control, I think, if you could boost the colour saturation for the over-exposed region, because one consequence of too much signal is burning out of colour. If you could pull the colour into the Trapezium it would boost the image, I think. Olly. Edit: Just done quickly on a screen grab.