andrew s

Nice project @Gina I was getting a bit confused before your last post on how it would work. Regards Andrew

I have a copy of the above book which is "a guide for the amateur radio astronomer". It a practical book including the hardware software etc. Suit someone with plenty of space as the aerials are big. Maybe a school or club. Probably all available on line but nice to have it in one place. First request with postal address secures it. Just PM me. Regards Andrew

And at 1000% the Gabblerdictum bird from Space Patrol! It's an age thing. Regards Andrew

Part 4, tell you how they made what they told you. Regards Andrew

Too much sacrificing of money to FLI and not enough blood sacrifice to the weather gods. Regards Andrew

Looks like a JMI Mobile http://www.jimsmobile.com/index.htm or similar clone. Regards Andrew

I recall the US military had several spare Hubble size mirrors (different focal ratio) from their spy satellite program two of which they gave to NASA some years later. Regards Andrew

Try this https://astronomy.stackexchange.com/questions/34086/how-to-calculate-parallactic-angle-from-a-fixed-alt-az-position Regards Andrew

These is no such thing as perfect polar alignment. The position of the apparant mean refracted pole depends on the declination of the target. On some pro wide field scopes they change the alt of the mount when imaging different parts of the sky. Regards Andrew

Looks like a thermal plume. Does it change as the scope cools? Regards Andrew

Do you have astigmatism in your eye(s)? Regards Andrew

Not what the OP asked for but you can see relativistic effects with a compass. Put it near a wire carrying a current and it will deflect. The magnetic field round the wire is the relativistic effect of the moving electric charges. Regards Andrew

Yes it is it is the same equation for the Schwarzschild radius https://en.m.wikipedia.org/wiki/Schwarzschild_radius which defines the event horizon for a non rotating spherical mass. Regards Andrew

I think you can. Firstly, the event horizon forms round a collapsing massive star before the singularity forms and secondly if you were outside a massive enough spherically distributed mass that was not dense enough to form a singularity (maybe as a thin shell of material). Regards Andrew

We are blessed with wide choice of excellent CCD and CMOS cameras. Think yourselves luck we have moved on from trying to hypersensitise film to a fraction of the performance of even the worst of those available today. Regards Andrew

Measuring the Hubble "constant" is not a simple matter of taking a measurement. To get from the measured values to H requires much theory and in many cases poorly known values for example in nuclear reaction rates and hence stellar evolution. It is in some ways amazing that it is as close as it is given these constraints. Just going from the CMB era H to H today requires a model where H changes by many orders of magnitude. Regards Andrew

Two points. The speed of light measured locally is a constant. There is a lot of different coordinate speeds of light depending on the coordinate system chosen including ones related to the expansion of the Universe. Cosmological distance is dependant on the model chosen and on the exact distance requested. I.e. the distance when the light was emitted or when received. The Universe is to a good approximation on a large enough scale homogeneous and isotropic so all points are equivalent so no special point to expand from. Also the expansion is not any kind of explosion from a point. It is a change in metrical scale everywhere. Regards Andrew

Yes I use CMOS. The best modern backed thinned CMOS camera are as good as and often better than the equivalent CCD cameras. The only remaining issues is that due to the mass market the pixels are small. This can be used to advantage in removing the telegraph noise CMOS produces. Have a look at C Buil's site http://www.astrosurf.com/buil/index.html for some reviews. Regards Andrew The higher read noise in CCD cameras reduces the effective but depth so not a lot of difference but newer CMOS are 14 or 16 bit now.

Try looking up in the aavso data base. I am sure it will have both V and B estimates but expect it to vary. In fact for such stars V-B varies considerably. I would not worry about it though just give it a go. Wikipedia gives 0.181 for v-b Regards Andrew

Yes the spectral type varies as the star goes through its cycle. rr Lyr is the exemplar for a class of variables. You can find lots of info in the web about it and them. Try the astro database SIMBAD to look up the star for its V and B magnitudes. Regards Andrew

Actually we can say gravity worked up to and beyond 10000yrs ago by looking at suitably distant galaxies. Regards Andrew

Nothing in Science is fully understood. We have models that work well or less well at predicting observable effects. We judge a theory on its usefulness and to a degree its elegance. No one know what energy or entropy "really "are. We are more familiar with energy so feel comfortable with it as opposed to say entropy. Regards Andrew

The simplest theory of dark energy is a very small non zero curvature to spacetime I.e. a small cosmological constant. Regards Andrew

Sorry @ollypenrice the Universe is and always have been spatially infinite according to the best current theory. This has nothing to do with the speed of light or the age of the Universe. Regards Andrew

The current best theory us that the Universe is spatially infinite and always has been! Spacetime (not space) was finite at t=0 and has been expanding ever since. The greatestest distance we can see is called the observable Universe and is from the CMB we see to day. It is further (in light years) than the age of the Universe because of the metrical expansion in the Universe. The most distant objects we can image are receeding faster than the speed of light due to the expansion but that is due to space expanding not the kinematics of the objects. Regards Andrew @Vladi listed while I was posting this