Alien 13

I use my laptop screen (calibrated with a spyder) to do all my photography and astro work, now a laptop screen has a very limited gamut but what calibration does and is the the critical thing with any photo processing is to set an accurate white and black point and of course good stable transition between the two with a smooth greyscale rendition. Alan

The Spyder and many others of a similar type of calibrator fully automates the whole calibration process by outputting various levels of R G B and taking measurements of them but does not have the ability to change the monitors internal settings. The result is a dedicated profile for your PC/Monitor combination. The software will set up some basic starting points that you will have to set on your monitor manually to ensure that any profile used by your graphics card wont overdrive it. Proper monitor hardware calibration is usually a manual affair unless the manufacturer makes a dedicated calibrator for it but you can get reasonably decent results by using a phone and app. Alan

I would like to add a small note regarding Monitor calibration using devices like the Spyder, I have the Spyder 5 pro and what it does is create a custom colour profile for your graphics card but does not in fact calibrate the Monitor itself. Alan

Even a std DSLR will have much more sensitivity to the extreme red and violet ends of the spectrum compared to the human eye so this might explain this CA. Alan

I do wonder if projects like star link dont in fact increase the interest in astronomy massively, I myself much prefer transient object like SN/Meteors etc. Alan

+1 to that.. Alan

I expect the manufacturers of Maks and SCTs optimize the performance for use with the std diagonal and eyepiece spacing but then add a T2 thread on the visual back so maybe they have optimized for both visual and imaging at differing points. Alan

The sensor on the Canon 6D will have been shimmed to minute tolerances so that is your benchmark, as Adrian has said you need to add whatever spacers are necessary to match that with the QHY camera. Alan

I have played around with spacing but have never convinced myself as to which is best so in general I try to put my DSLR sensor at the same point as that obtained with a diagonal/eyepiece combination. I would like to know though what is likely to be the best distance to minimize any vignetting.. Initial thoughts are greater spacing=longer focal length=shallower light cone=less vignetting caused by the focus tube but then the longer focal length may cause issues because the secondary might not get fully illuminated. Alan

I agree Simon, a star test will show if the spacing is critical or not.. Alan

It certainly is strange, from memory every bit of glass in the optical train adds on average 1mm to the required backfocus distance so 1mm for the filter and 1mm for the sensor window. It could be interesting to see how much extra spacing is required to get the focus mark in the correct place.. Alan

I admit that its very odd but still think the infinity mark on the lens is telling the truth as shown when connected to the Canon camera. Have you tried measuring the overall spacing with a vernier? Alan

It does sound as if your spacing is a little short, did you allow extra for the filters? It depends how the focusing is done on this lens, some lenses move the whole assembly and others certain elements only, if its the former then it wont matter at all where the focus position is but might do with the latter. Alan

I use one of these dovetail bars in conjunction with a ball head on my EQ3-2 for my DSLR.. The ball head lets you choose the orientation of the camera and hence the composition. Alan

I have the 70-200 f/4L and its fine for AP even wide open plus you can use it with some teleconvertors if you want a longer FL, the reports I have seen on the 200mm prime suggests it needs stopping down to f/4 for AP so has no real advantage. Alan

I had the 18-55mm IS lens and it was fine, a pain to focus with its sloppy focus ring but provided you picked a feint star away from the center to get focus then it could be used wide open, it performed far better than my nifty fity which still struggled even when set at f/8. Alan

Correct, I had forgotten about the floppies, the 5 1/4 was realy floppy and did play with some even bigger ones. Alan

It was normal in the old days to have a single hard drive and CD/DVD drive that usually got allocated as drive D. I often wonder why we never had A and B drives.. Alan

Drive D is usually allocated to an external type drive, I installed mint on my win 7 laptop keeping it as a dual boot machine but created a partition on the C drive for that purpose. Alan

I used to love the way the junior officers took over the "night shift" on Voyager as though expecting that the whole Galaxy was asleep... Alan

The spacer is there to prevent any direct glass to glass contact, have made suitable spacers from various things like coke cans/milk cartons in the past but that damage you mention is probably the main culprit. Alan

Usually the inner two surfaces of the lens elements match each other in curvature, if they are dirty might as well clean them and try reversing the front element but make sure this doesn't cause any glass to glass contact. The flattish surface should point towards the eyepiece end of the scope like this. Alan

That might work, Achros do usually have a bit of free play in the lens cell to avoid pinching effects. Alan

Looks like someones had the lenses out and put them back in the wrong order, curvy less curvy inverse curvy flatish is the normal configuration I think. Alan

I have no doubts that the only Aliens that had the technology to send radio signals and have the ability for space travel would look pretty much like us.... Alan