Merlin

Many years ago, solar observer, Bill Baxter, used to tie pieces of foam underneath his shoes or slippers when observing in cold weather. camping mat should do the job. It’s the ground itself that makes the feet cold.

Astronomy teaches us just how precious our eyesight is. My problem is double-vision due to pressing a binocular with rubber eyecups too hard against my eyes. There was a suction effect that caused a muscle to relax in the right eye. Fortunately, the double-vision can be corrected with specs.

It seems unusual that the Miranda’s are described as having good optics. I thought the Miranda’s were cheapo Dixon’s brand. The optics in the Miranda’s I looked through were mediocre but serviceable.

I have a 8X42 Opticron binocular. One day, my screwdriver slipped when I was tightening a screw. It gouged out a small pit in one of the objectives. The defect makes no noticeable difference to the optical performance because it isn’t in focus.

Expensive.

That reminds of a Pound Shop claim that it’s toilet rolls were bigger but without a corresponding price increase. All that they had done was to increase the diameter of the tube.

The stopped down bins could be a manufacturers’ trick to make us think that we are getting more than we are.

Using the rings is known as conditional collimating, not true collimation.

I recall reading somewhere that a good Newtonian reflector is superior to any folded-beam instrument.

One possible plywood currents-free solution might be to isolate the window from the room by making a small portable room within the room that you can bring up to the window and leave unheated, hence currents-free.

The thing about Cox is that he’s a particle physicist not an astronomer. If an astronomer was presenting the series, we’d pick up the vibes.

The Sky & Telescope article I saw was indeed the Alan Adler article. I’d forgotten to mention that it deals with closed tube Newtonians.

After a further investigation the cluster isn’t very ancient, it’s middling. Also, red dwarfs dominate the cluster with only eight red giants.When I first learned about this open cluster, Gaia-ESO and other space telescopes didn’t exist, but now knowledge of the cluster has increased because of them. Apparently, the cluster is regarded as important to astrophysicists these days for “calibration” purposes.

Got it. The cluster is NGC 6802 and at Mag 8.8.

The cluster has a NGC number, but I can’t remember it. Please let us know if you find it. The cluster was discribed as being very ancient and consisting mostly of red giants.

You said “mum”, but shouldn’t that be mom? Depending on where we live in the UK, it’s either mum, or, further north, mam.

An important point I’ve missed out on the previous post is that the fan should be mounted on a block of foam to absorb vibration.

Some years ago there was a definitive Sky & Telescope article showing that the most effective way to use a fan is to mount it on the side of the main tube. The fan should be blowing air across the mirror surface and exiting through three or four inch diameter, side-by-side, vent holes on the other side of the tube and on a level with the fan. This arrangement removes the blob of cold air that settles on the mirror, causing poor definition. We should forget about “tube currents” and go for the blob.

The bigger bino will collect around 80% more light.

The Coathanger’s been mentioned as an open cluster, but isn’t it classified as an asterism? There is an ancient and, apparently, understudied open cluster at one end of the Coathanger.

I have a Skymax 90mm ‘scope and get superbly sharp views of the Moon with the WO binoviewer. Jupiter and Saturn look good too for the aperture.

Perfectionists might wince at this, but I’ve made my 20cm Newtonian a closed tube ‘scope. I went to Asda’s to see if I could find a clock with a glass front big enough to play the part of an optical window. Having found a suitable clock for just £6, I removed the very thin glass front and its bright aluminium collar and found that they fitted snuggly over the front of the ‘scope. The rear end of the tube was closed off with a piece of foam. Now to try it out.. . The Moon was the first target. The new arrangement yielded sharp images at quite high magnifications. Then, I tried the stars in the Pleiades. Again, the images were sharp and, surprisingly, there was no sign of astigmatism. Finally, I made a dew shield from a piece of rolled camping mat. I haven’t tried the ‘scope yet with the highest magnification of 400x as the primary needs a recoat, but it looks promising. It’s been suggested that front aperture glass solar filters with their coatings removed would make good optical windows. A 20cm solar filter can be bought for about £100, but the problem is knowing how to remove the protective coating.

Maybe the flat itself has stress lines in it due to poor annealing.

I use a 7-21 zoom on the PST. It makes for a compact arrangement.

A small spottingscope, ranging from 65 to 80mm aperture, is recommended by some for lightweight portability.