Deep Sky Objects in light-pollution with 4" Dob - Given up for now

[flord.lord]

Unfortunately, I have mobile Stellarium+ and I don't think I can enable that feature. Here is what I have currently got

Now that's a shame. I have discovered that I prefer decimal. In the desktop version you make the change once for the entire program, including the oculars and angular distance plug-ins. (I found an exception: the location window remains in minutes and seconds mode.)

The sexagesimal system is from the 3rd millennium BCE. Maybe the makers of Stellarium mobile can be moved to update to decimal, at least as an option. Ask them!

Good luck.

[mention]Ruud[/mention] I'll see what I can do, but is what I've currently got "right" for my scope and 25mm eyepiece?

[Ruud]

Here is what I have currently got

  
If I understand correctly, your telescope is f/4 with an aperture of 100 mm and focal length of 400 mm.
Your 25 mm eyepiece probably has a 50° field of view. (That's kind of standard for the 25 mm kit eyepiece.)

In this is all true,

• your magnification is 400 / 25 = 16 x

• your true field of view should be 50°/ 16 = 3.1°

Stellarium says that your true field is 0° 51'. This is probably incorrect as it is less than a degree (51' = 51/60 degrees = 0.85°). My guess is that you may have entered the wrong info about your telescope or the wrong field of view of your eyepiece. Please check.

[ARock]

@Ruud
Unfortunately, I have mobile Stellarium+ and I don't think I can enable that feature. Here is what I have currently got

From the pic it seems to be the Stellarium on the mobile does not calculate the FOV but depends on the user to specify it. My earlier comments on the Ocular pliugin calculating the true FOV were for then Laptop/Desktop version of Stellarium.

I think you should set the FOV angle to 3.1 degrees in the app. You can figure out the true FOV of any eyepiece using the site
https://astronomy.tools/calculators/field_of_view/

[flord.lord]

Here is what I have currently got

  
If I understand correctly, your telescope is f/4 with an aperture of 100 mm and focal length of 400 mm.
Your 25 mm eyepiece probably has a 50° field of view. (That's kind of standard for the 25 mm kit eyepiece.)

In this is all true,

• your magnification is 400 / 25 = 16 x

• your true field of view should be 50°/ 16 = 3.1°

Stellarium says that your true field is 0° 51'. This is probably incorrect as it is less than a degree (51' = 51/60 degrees = 0.85°). My guess is that you may have entered the wrong info about your telescope or the wrong field of view of your eyepiece. Please check.

The Stellarium app is rather limited. In fact, that's the only "optics" settings there are. Can't enter a telescope. I've tried again, getting as close to 3.1 as I can...

[Ruud]

That's close enough. Eyepieces usually have a few percent of angular magnification distortion, so that the real "true field" is a little smaller than the calculation (from apparent field of view -assumed 50°- and the calculated magnification) suggests.

If you want to do more eyepieces: here is a handy decimal <--> deg/min/sec converter. It says 3.1° = 3°6'
https://www.rapidtables.com/convert/num ... conds.html

[KingClinton]

Like Ruud says, you are close enough to resemble the eyepiece view.
Also remember to flip the view horizontally, then the image will match the stars in the eyepiece and make star hopping that much easier.

I think the basic version of Skysafari is now free?
Not sure how the basic version stacks up against stellarium.

[flord.lord]

Like Ruud says, you are close enough to resemble the eyepiece view.
Also remember to flip the view horizontally, then the image will match the stars in the eyepiece and make star hopping that much easier.

I think the basic version of Skysafari is now free?
Not sure how the basic version stacks up against stellarium.

[mention]KingClinton[/mention] Are you sure I should check that option? I've found that my telescope view is vertically flipped (upside down) rather than horizontally flipped (mirror image [?]). I was under the impression that that was for refractors with star diagonals... I could be wrong though

[KingClinton]

Like Ruud says, you are close enough to resemble the eyepiece view.
Also remember to flip the view horizontally, then the image will match the stars in the eyepiece and make star hopping that much easier.

I think the basic version of Skysafari is now free?
Not sure how the basic version stacks up against stellarium.

@KingClinton Are you sure I should check that option? I've found that my telescope view is vertically flipped (upside down) rather than horizontally flipped (mirror image [?]). I was under the impression that that was for refractors with star diagonals... I could be wrong though

Yes, both must be set when using a Newtonian scope. I set both when using Skysafari.
Horizontally and vertically.
This will vastly improve your star hopping as the eyepiece views match your screen view.

[flord.lord]

Globular clusters will look like a puff of smoke, so are sensitive to sky contrast. It should be visible in your scope. Not sure about your sky darkness though.

Things to try, assuming you are using Stellarium, a red dot finder, and the 25mm EP.

1. In the Red Dot finder , find Arcturus and Cor Corioli and place the scope close to midway between them towards Arcturus.
Then try the EP.

2. In stellarium, set up the Oculars plugin with your scope and EP settings so that you have the FOV circle for the EP. Start from Arcturus and move short distances towards M3 by way of the brightest stars. At every step match the stars you see in the 25mm with what you see in Stellarium. It helps if you set the LP level in stellarium to match what you see in the scope.
Long hops need patience and lots of tries. A 10x50 bino can help you scout the area.

3. Make a paper setting circle for the Az axis and an digitial inclinometer for the Alt axis and use it as a pushto. Google Manual setting circles for a Dob.

M22 is another bright globular and an easier hop. You can use it to figure out if your sky permits seeing globs at all now. If it doesn't you can look for open clusters, which are easier to see.

Do you have the book "Turn Left at Orion" ? It is very useful for beginners.

Good luck

[mention]Helicon[/mention] [mention]Ruud[/mention] [mention]ARock[/mention] I tried again on M3 last night with my 25mm and the Stellarium oculars finally sorted out. I started at Arcturus, then tried again from Muphrid, then Cor Caroli. I could see the stars that I was supposed to see in the 25mm, but when I got near M3 I couldn't see anything. Once or twice I thought I might've done, but that was with averted vision, and not enough to center or switch eyepieces on. I found the limiting magnitude with the 25mm to be about 7.3, but even then I had to really squint and hold your eye focus on it. (Bortle 7/8 ).

My guess is sky contrast and sky darkness. I was observing at 22:45 in nautical twilight, with the sky being a greyish hue. I understand globs are sensitive to this kind of contrast; they need a dark background.

Astro twilight doesn't start until midnight here, and quite frankly I'm not prepared to stay up till then.

Thanks for all your advice about starhopping and such, it's been very helpful . I posted this just to ask for suggestions on any other DSO targets that I might be able to see :'). I might try M22 as you suggested or maybe open clusters.

Thanks

[Ruud]

Try A Simple Guide to Backyard Astronomy Using Binoculars or a Small Telescope
Assembled by Carol Beigel

It is a pdf with finder charts for the best targets, tables, books, gizmos, etc., all that you need.

This is a direct link: http://carolrpt.com/astroguidev9complete.pdf

[KingNothing13]

I might try M22 as you suggested or maybe open clusters

M22 is pretty stunning - especially the first time you see it - it is one of the grandest GC's in our skies.

Apologies if you have answered this already - are you in a position to be able to see M13? It should be fairly easy to find, if you are.

[flord.lord]

I might try M22 as you suggested or maybe open clusters

M22 is pretty stunning - especially the first time you see it - it is one of the grandest GC's in our skies.

Apologies if you have answered this already - are you in a position to be able to see M13? It should be fairly easy to find, if you are.

Yep, M13 is visible from London. That'll be my next target.

[ARock]

My guess is sky contrast and sky darkness. I was observing at 22:45 in nautical twilight, with the sky being a greyish hue. I understand globs are sensitive to this kind of contrast; they need a dark background.

It should get much better in a month. You could also try some double star observing in the meantime.
https://www.astroleague.org/al/obsclubs ... star1.html (pdf list at the bottom of the page).
Get the book "Turn Left At Orion" (used copies are fine). It contains a list of DSOs viewable by smaller telescopes, sorted by seasons/months. It also describes how to find them in the night sky.

One thing worth trying if your surroundings are not completely dark, is to use an observing hood. A towel/inverted T shirt works. It will make the space around your eyes dark when you are observing, and might make it easier to see fainter objects.

Keep a log of your observations. It might help you in the future deciding what objects can be seen in which months.

[helicon]

I agree that M13 and M22 should be your next targets. Good luck.

[flord.lord]

My guess is sky contrast and sky darkness. I was observing at 22:45 in nautical twilight, with the sky being a greyish hue. I understand globs are sensitive to this kind of contrast; they need a dark background.

It should get much better in a month. You could also try some double star observing in the meantime.
https://www.astroleague.org/al/obsclubs ... star1.html (pdf list at the bottom of the page).
Get the book "Turn Left At Orion" (used copies are fine). It contains a list of DSOs viewable by smaller telescopes, sorted by seasons/months. It also describes how to find them in the night sky.

One thing worth trying if your surroundings are not completely dark, is to use an observing hood. A towel/inverted T shirt works. It will make the space around your eyes dark when you are observing, and might make it easier to see fainter objects.

Keep a log of your observations. It might help you in the future deciding what objects can be seen in which months.

I have a digital copy of Turn Left and I'm currently reading it.

Double Stars is a good idea. So far I've managed to observe Mizar A and B.

[KingClinton]

Don't be discouraged, you will get it right.

You also need to train your seeing eye.
Seeing a target in the eyepiece also needs practice. With time and more experience your eye learns to see better in the eyepiece and you will find that you can see some of the dimmer targets that you may not have seen when starting out.

If you don't see anything now that's fine, come back to it in a month or two and you might find that you now see it as your eye adapts to seeing more detail and much fainter wisps in the eyepiece.

I know your light pollution must be horrible in London. Soon you will figure out what can or cannot be seen. From my background I don't bother with DSO from 8th magnitude or more as I rarely see them.

[flord.lord]

I agree that M13 and M22 should be your next targets. Good luck.

[mention]Helicon[/mention] Great advice! Finally found a GC (M13). It was much easier than finding M3, as all I had to do was draw a line between Zeta and Eta Herculis.

Though an amazing first find, through each eyepiece, while it did get bigger, it remained dim. Is this due to Bortle 8 or would you recommend I invest in an LP filter (https://www.firstlightoptics.com/light- ... ilter.html)?

Anyway, I should have a chance to travel to Bortle 4 soon.

Thanks.

[John Baars]

LP filters generally don't work on stars. In fact they make the image darker. So they won't work on GC or Galaxies.

They do work on emission nebulae
They consume a lot of light, so be sure your magnification is very low, which means a big exitpupil.

If you want the GC to be brighter there are two possibilities:
1. Use a gasoline filter: drive to a nearby very dark area.
2. Increase the aperture dramatically.
#1 is the best of the two for the time being. In the end you will probably prefer 1 & 2.

When you stay at home , without filters, a higher magnification will show more stars, up to a certain limit of course. It won't become brighter though.

[KingNothing13]

I agree that M13 and M22 should be your next targets. Good luck.

@Helicon Great advice! Finally found a GC (M13). It was much easier than finding M3, as all I had to do was draw a line between Zeta and Eta Herculis.

Though an amazing first find, through each eyepiece, while it did get bigger, it remained dim. Is this due to Bortle 8 or would you recommend I invest in an LP filter (https://www.firstlightoptics.com/light- ... ilter.html)?

Anyway, I should have a chance to travel to Bortle 4 soon.

Thanks.

Glad you found M13 - it is a very pretty cluster. Likely the best in the Northern Hemisphere.

[Buckethead 2.0]

I took a look at M3 last night @flord.lord (it has been awhile) in the 10" Dob. Pretty well resolved at 135x with some sparklers at the edges. Found by aiming the scope at the point about 2/5 of the way between Arcturus and Cor Caroli. The sky was not completely dark (9:45) meaning the view was slightly muted. About 20 minutes later (more darkness) I peeked at M13, which was a bit more impressive, and also, the sky was darker.

Just sort of a test to see whether M3 was fully visible in a darkening sky...

Pardon me for interrupting, Michael, but is that 2/5 of the way from Arcturus to Cor Coroli, or vice versa?