John

As in "She slew him when she found out how much his eyepieces had cost"

There's our problem in the UK then - our highest point is just 1345m and that is Ben Nevis in the Scottish Highlands ! Most of my observing is done from 2500m lower than your high spot Don I feel that I've glimpsed the central star in M57 once or twice with my 12 inch dob but I

The Delos are not too bad - the 10mm weighs 408 grams / .90 lb They are quite tall though especially as the focal length gets shorter. In some circles I've seen them nicknamed "turkey legs" !

That's a very useful site. Well worth reading the pop up info you get when you click on ? is this simulator realistic ? What an individual actually sees may well vary to some extent from the simulation images. Light pollution, for example, can cause galaxies and nebulae, even bright ones, to become practically invisible while under a dark sky they stand out like a sore thumb ! But it is a useful approximation.

I guess there will be some designs that never made it into production and some that were intended for a very specific purpose, maybe military, so we don't see them ?

In doing presentations to my astro society, I've tried to produce simulations of what some objects look like though the eyepiece. With the fainter ones, by the time you have toned down the contrast to get it close to how it actually looks, the target has practically vanished when you project the image onto the larger screen, even with the lights turned off !

No. It is a fair amount above the horizon at 10:30 pm from here. This was taken at around 11:00 pm last night:

I use Cartes du Ciel - also free and very accurate I find: https://www.ap-i.net/skychart/en/start 10:00 - 10:30 pm in the N / NW is about right.

The last SN observed within our galaxy was in 1604, observed by Kepler I believe. We might be due another though ?

There is something about the view of double stars through a good quality refractor that is really satisfying. Even often observed ones such as Epsilon Lyrae merit frequent re-visiting when you have perfectly formed airy disks, a faint diffraction ring around each star and the subtle tint differences Mak-cassegrains and mak-newtonians get very, very close to this as well though and are affordable in larger apertures too.

That is one of the best images of this comet that I have seen to date. Thanks very much for posting it Ken

The challenge is that the some of the factors you list are so variable, locale to locale, hour to hour etc, that I can't see how they could be factored in for locations in the world, which the software covers They do cater for atmospheric extinction which happens as an object moves towards the horizon and they cater approximately for the amount of daylight still in the sky. You can set your altitude about sea level. That's probably about as far as such a tool can go. Also, an experienced eye will see more detail than an inexperienced one with the same scope. A dark adapted eye will go deeper than one that isn't. Where would you set the benchmarks ? I see Stellarium, Cartes du Ciel etc as primarily tools to locate targets. I think what you are looking for is more of a view simulator ?

Yes, that's the one. The widest true field I can get is about 1.7 degrees. If I want to observe the whole of the Veil Nebula I have to move to my 102mm F/6.5 refractor where I can get 4 degrees with a 6mm exit pupil. With the 12 inch I can fit the whole of the East or West segments of the Veil in the FoV.

That's a good point. The cap on this 10mm Delos looks like the one that TV use on the 2 inch Powermate. In the past they used a hybrid cap on their eyepieces - 2 inch one side and a touch more on the other to accommodate the eye cup. Perhaps they have moved over to the Powermate type caps now ?

If Jupiter fills the eyepiece then it is not in sharp focus. It will appear small in the eyepiece when it is at focus. Something like this with a 26mm eyepiece:

This is an image I got last night cropped to simulate the view that I had with my ED120 refractor at 22.5x - 3 degrees true field of view. Solid clouds and drizzle tonight. Hope the comet stays bright for a while longer

I have not measured mine but generally assume that at my age it's going to be around 6mm or so, max. So with an F/5 scope I reckon 30-32 mm is the longest focal length that will be reasonably efficient. I've used a 40mm eyepiece with my F/5.3 dob and don't recall seeing the secondary shadow but it would have been when viewing a dark sky so I might not have noticed it ? I find 31mm or even better 21mm more effective in DSO observing with that scope under my skies.

The challenge with a newtonian is that the split is made but it is sometimes hard to see that it has been made due to diffraction from the secondary etc, etc.

Wish they would not use the headline "streaking across". Non-astronomers will think that they have to dash outside and watch it fly over They do qualify that in the article itself but many folks might not get past the headline and the pic.

I cool mine at around 45 degree angle with all the caps off. Takes 30-40 minutes before I can use high powers to full effect. Low to medium powers can be used more or less straight out of the house.

The one Shane pictures is / was his I think. He made an identical mount for it after he had finished mine. Mine is F/5.3.

Lumicon do make a comet filter also known as the SWAN filter: https://www.astroshop.eu/line-filter-sets/lumicon-filters-swan-band-comet-filter-1-25-/p,6750 Whether that works with all comet types I don't know.

Great selection Shane Each time I use my 12 inch dob, I say a little "thank you" to you

Chris Lord is a member here but has not visited for quite a few years.

I thought the central star was mag 15.3 ?