andrew s

If horizontal, he might be a peeping Tom or neighbourhood watchman. Twitching lace curtains and all that. Regards Andrew

IHSAHAKAT ?

The BAA has a section on this area BAA section . Regards Andrew

@theropod, I was not intentionally trying to ignore your points. I was just commenting that we can make our own judgements. You clearly feel strongly about this but generally I try not to assign motive (good or bad) without evidence. I will decline to comment further. Regards Andrew

We are a special subset of all "grown-ups". Clearly not totally immune to stupidity as we spend a fortune on kit the weather conspires to stop us using. I did understand your point but failure to agree does not necessarily equate to lack of understanding. Regards Andrew

We have all been in a similar state due to one cause or another. Regards Andrew

I suspect, given the demographic, that we are experienced/old enough to make our own judgements on joining a collaboration or not. Personally, I am a lone wolf by instinct but have made contributions to the HOYS project in the short summer nights. While, they acknowledge all who contribute data, I can't say it matters much to me. I did it as I felt like it. Regards Andrew

This is a good modern spectral library Miles it and selected Calspec (HST) and Pickles (calculated) spectra and other are in Buil's ISIS database here ISIS some in Fits and some in .dat format. Regards Andrew PS The Miles spectra in the link have been dereddened those in ISIS have not and are how we would see them.

What a fascinating discussion conducted with such good manners. It's like two chess grandmasters exploring the possibilities of a position. Regards Andrew

...and don't buy any more Takahashi refractors as I have more than my fair share.

The SDSS filters did not have a gap in the in originals used in the survey. If you look at the M Fukgita et. al paper referenced by Astrodon there slight overlaps between adjacent bands. The paper is worth a scan for a feel of the effort needed to put measurements on a standard absolute scale. Of course the SDSS filters are designed for photometery not RGB imaging. Regards Andrew

But what about the noise in the blue and the minimal discrimination between red and green. Needs neural processing by the brain to make sense of it. 😏 Regards Andrew

The eye had a response like this. I am sure no set of filters for AP would be so poor! Regards Andrew.

Sorry I not clear enough . Is the shift in RA or Dec or a combination. Looks like the RA drive is sticking then slipping occasionally or possibly periodic error. Hopefully, someone with experience of this mount will comment. Regards Andrew

Can you provide some more information. What is the orientation of the image RA / Dec? Were you guiding? Was it windy? Regards Andrew

You might want to look at C Buil's ISIS software. It has several catalogues built in and the tools to manipulate them. Getting the true QE of the whole imaging train will be difficult as it's not just the sensor but absorption and reflectivity of the lenses and mirrors. You could take images through filters of spectroscopic stars and then compare the values derived from published spectra and the filter profiles (assuming these are accurate). You will still have the issue of airmass! It a very hard problem to do accurately. Clearly PixInsight put a lot of effort in even if, as you feel, it's not right to use white point. Regards Andrew

As the image shows the black body that fits the continuum will have a much higher bolometric output than the star due to the Balmer jump. The stars from the same class ( both primary and luminosity) will be much the same but for interstellar reddening though they can be de-reddened using V-B etc. There can be small differences due to metalicity. Regards Andrew

No the drop is real. It due called the Balmer jump it due to electrons being ionised directly from the second level in the H atom causing a strong absorption. Regards Andrew

Quick go at this need to check I did the sums correctly for the plank curves. The plots are relative so the A0V spectra can be translated vertically with respect to the plank curves Teff for A0V is 9727k Regards Andrew

Beware Effective Tempetature. It is the temperature of a black body that has the same luminosity per unit area as the star. For many classes of star, especially the cooler ones, it does not match the spectrum of the star as the spectrum is far from that of a black body. Regards Andrew

The engineering needs to be be excellent to ensure no backlash or tilt, with possibly both heavy and off axis loads, independent of the position resolution. I use mine to ensure my slitless spectra avoid field star and their spectra. Regards Andrew.

Forgetting the camera / eyeball for a moment I had always thought that for emissive objects the Sun, G2V, was by definition white. Not sure if the definition is outside the atmosphere or at unit air mass. Hence the use of G2V stars in image processing (with due regard to interstellar reddening). Regards Andrew

They are all expensive. They need to be very well engineered to work well. I use the Optec Pyaxis LE. Regards Andrew

2nd hand should be ok try here and astrobuysell uk Regards Andrew

Which brings us full circle as reflection nebula can be blueish and transmission redish. The "ish" is to imply uncertainty and trying not to restart the debate.👹 Regards Andrew