John

21 hours ago, impactcrater said:

it sounds like a long orbital period...is the typical of doubles ?

There are some big variations. Zeta Herculis, for example, has an orbital period of a touch less than 35 years. I have a sketches of it done in 2016 and 2020 and the change in position angle between the two is very obvious.

2 hours ago, Dippy said:

Your photo truly is from today! I can see the 5th magnitude star 26 Lynx (the brighter of the two) to the right of comet. Would you mind John to ask what camera you are using?

A Pentax K-r DSLR. It's not a camera that is commonly used for astro photography - I bought it so that I could use my old Pentax K fit lenses etc from my old 35mm days.

7 hours ago, Mostafa said:

Also, are the pictures in the simulation stacked and processed or not?

Again thanks,

That one aims to show images as they would appear through an eyepiece. They explain how the images are processed in the simulator.

Try this simulator. It is quite accurate if your skies are reasonably dark:

https://www.stelvision.com/en/telescope-simulator/

Stacked and processed images will not look anything like what you can see visually.

Another from just now. Slight trailing at 10 secs, ISO 1600, 150mm FL:

Surprise break in the clouds here allowed some quick shots and a view with 8x56 binoculars. Still looking lovely !

This one caught a few people out in April 2017

16 minutes ago, Stardaze said:

You can't want for much John 😆

I ought to shed some stuff really ...... then I can get some more ! 

14 minutes ago, Stardaze said:

.... Two EP's first though.... it's a never ending money pit, huh! 

Too true ! 

I found the limits of an EQ6 for visual. This scope made the EQ6 seem small and a touch puny

Another interesting challenge is that it is possible to discern the identities of the moons by their apparent disk sizes. Although very tiny, they do show some variation if you focus sharply and the largest, Ganymede, has an apparent diameter noticeably larger than the others if you look closely.

Interesting tables.

Tube lengths come into the equation having as much or more impact than weight as they get longer.

Mobile phone images of Jupiter invariably over-expose the planet so the features that can be seen quite well with the eye at the eyepiece vanish in the glare.

With a 90mm mak-cassegrain at around 120x a few nights back I could see 4 cloud belts and some festoons coming off the northern equatorial belt and into the pale equatorial zone. A couple of nights earlier, with my ED120 refractor I could see the Great Red Spot sitting in the center of the disk embedded in the South Equatorial Belt.

Here is a nice image of Jupiter (not mine) showing the various features to look out for:

1 hour ago, John said:

Some Tele Vue eyepieces include a small circular mask which is placed immediately above the eye lens to help find the exit pupil of the eyepiece for those who have difficulty with this. It is called a pupil guide.

As the focal length of the eyepiece gets shorter, finding and holding the exit pupil (the small circular spot of light that exits an eyepiece) becomes more challenging because the exit pupil reduces in diameter. Holding the head still, so that the eye is both central and at the right distance from the eye lens, becomes even more important.

When doing outreach I tend to use longer focal length eyepieces for this reason. People who have not used a scope can find positioning the eye tricky with a short focal length eyepiece.

 

 

On this topic, I find it important to position the eye cup correctly to ensure the you get the best from an eyepiece. Some eyepieces have twist up and down eye cups or top sections and, if you do not wear glasses when observing, generally the upper positions work the best. If you do wear glasses when observing, generally the lower eye cup position works the best. I use the word "generally" here because we are not all the same of course with regard to our eyes, face shape, depth of eye socket etc, etc.

I like to use the eye cup as my guide that my eye is in the right place so my preference is to gently nestle my eye brow / eye socket against it. I have come across a few eyepieces where the eye relief is so long that the correct eye position involves "hovering" the head above the eyepiece top and this I find less than relaxing for lengthy periods making maintaining the correct eye position more difficult than it should be.

These are my personal findings and preferences however. Yours may well be different !

Some Tele Vue eyepieces include a small circular mask which is placed immediately above the eye lens to help find the exit pupil of the eyepiece for those who have difficulty with this. It is called a pupil guide.

As the focal length of the eyepiece gets shorter, finding and holding the exit pupil (the small circular spot of light that exits an eyepiece) becomes more challenging because the exit pupil reduces in diameter. Holding the head still, so that the eye is both central and at the right distance from the eye lens, becomes even more important.

When doing outreach I tend to use longer focal length eyepieces for this reason. People who have not used a scope can find positioning the eye tricky with a short focal length eyepiece.

39 minutes ago, johninderby said:

...... As an unrelated verb, it's the past tense of slay.”

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" !

2 hours ago, AstroMuni said:

Dantooine & greg110902 - I have found this site useful https://www.stelvision.com/en/telescope-simulator/

As John has already mentioned its possible in Stellarium but configuring all the parameters is going to be tricky 🙂

 

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 ?

3 hours ago, Dantooine said:

John

visual simulator, yes from my point of view and possibly the op’s. In my case it’s so my eagerness doesn’t sweep straight past things. (I need to look harder). 
 

Dale. 

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 !

29 minutes ago, iwols said:

is that right

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.