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What you see in the eyepiece and star charts


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Some help required!

I struggle with what I see with my eyes, what I see with binoculars and what I see in my eyepiece, take away the upside down etc. in my reflector and I'll explain further.

I have S&T pocket atlas, say I set Arcturus in the centre of my eyepiece (15mm Meade 4000, my 25mm is an MA and the difference in quality is massive, need to get a new 25mm), how do I match the view in the eyepiece to the view on my atlas, I've tried setting Spica in the centre of my eyepiece, timing how long Spica gets to the edge of my view and dividing the time in seconds by 120 (2.6) and I've taken the magnification and divided by the apparent field of view of the eyepiece (1.95), so even if I take a good average and say 2.0 degrees I don't see the same thing in eyepiece as Atlas (daft it might sound but Arcturus looks huge in the atlas and tiny in the eyepiece, I know magnification etc. represented in Atlas but it still looks wrong).

Help greatly appreciated as I look with eyes and can follow the constellations, I can follow with Binoculars but once I use eyepiece the number of stars visible vastly increases and I get confused moving around, hope I've explained the problem!

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I think it is the same problem for all of us. As you move from naked eye to binoculars and then a telescope more stars come into view but the field of view gets smaller. You need to turn your pocket atlas map until it matches the view of the telescope which will be giving an upside down, wrong way round view compared to the naked eye. Practice is really the only solution.  :icon_biggrin:

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1 hour ago, DavidJM said:

Some help required!

I struggle with what I see with my eyes, what I see with binoculars and what I see in my eyepiece, take away the upside down etc. in my reflector and I'll explain further.

I have S&T pocket atlas, say I set Arcturus in the centre of my eyepiece (15mm Meade 4000, my 25mm is an MA and the difference in quality is massive, need to get a new 25mm), how do I match the view in the eyepiece to the view on my atlas, I've tried setting Spica in the centre of my eyepiece, timing how long Spica gets to the edge of my view and dividing the time in seconds by 120 (2.6) and I've taken the magnification and divided by the apparent field of view of the eyepiece (1.95), so even if I take a good average and say 2.0 degrees I don't see the same thing in eyepiece as Atlas (daft it might sound but Arcturus looks huge in the atlas and tiny in the eyepiece, I know magnification etc. represented in Atlas but it still looks wrong).

Help greatly appreciated as I look with eyes and can follow the constellations, I can follow with Binoculars but once I use eyepiece the number of stars visible vastly increases and I get confused moving around, hope I've explained the problem!

If I'm misunderstanding then I apologise, but to explain, the size representations on the map just represent brightness, not the size of the star you will see. Stars are all point sources from the distance we observe them so they never get any bigger regardless of magnification.

I find Star atlases difficult to interpret for many of the reasons you say. One thing you could do is make up circles to represent the field of view in each eyepiece, that may help. If you use a Newt then you can turn the atlas upside down and the view will be correct. A refractor with diagonal is more difficult as it is left-right reversed.

For these reasons, I tend to favour star apps on my phone. You can set the orientation, field of view and magnitude of stars shown so that it exactly matches what you see. The other benefit is that they are presented as white on black not inversed so my brain finds it easier somehow.

These images show the S&T atlas view, then a matching view on a star app, and finally the view with a 2 degree field of view, upside down for reflector view and showing mag 9.5 stars, much more useful. Arcturus remains at a more realistic size and you can understand the other stars in the field.

IMG_2268.JPG

IMG_2274.PNG

 

IMG_2275.PNG

IMG_2276.JPG

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I started with S&T atlas, but found I was having the same issue as yourself, I found an atlas that showed stars to a dimmer magnitude (mag 10, I think), and found that my 2"->1.25" adapter was was a good match for the FOV of my lowest power EP, and that only a few extra, very dim stars where in the EP. I've had much better success since printing this one off.

I personally don't get on with using a phone in the field, but everyone needs to find what works for them.

WP_20170603_10_31_27_Pro.thumb.jpg.e0af618e331bb67e1e2a5a4da8b9f420.jpg

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A good star chart will help. I use Cartes du Ceil as it allows you set it up however you like.

I've used Epsilon Lyrae as an example below. I set finder fields to match my 42mm, 22mm and 13mm eyepieces - it has a built in calculator, all you do is fill in the focal length of you telescope, the eyepiece's focal length and field of view. It then gives you finder circles on the chart.

I also have my labels set to show magnitudes - very useful!

A little used feature in CdC is the ability to flip the field around to match Newtonians. So you could have a chart the right way up, upside down, or, flip left and right!

finderchart1.thumb.jpg.003293963b6506e1ce7436b07c8249fe.jpg

CdC is one of the most useful and powerful programs out there. Like most it takes time to learn but is well worth the effort.

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3 hours ago, Stu said:

If I'm misunderstanding then I apologise, but to explain, the size representations on the map just represent brightness, not the size of the star you will see. Stars are all point sources from the distance we observe them so they never get any bigger regardless of magnification.

I find Star atlases difficult to interpret for many of the reasons you say. One thing you could do is make up circles to represent the field of view in each eyepiece, that may help. If you use a Newt then you can turn the atlas upside down and the view will be correct. A refractor with diagonal is more difficult as it is left-right reversed.

For these reasons, I tend to favour star apps on my phone. You can set the orientation, field of view and magnitude of stars shown so that it exactly matches what you see. The other benefit is that they are presented as white on black not inversed so my brain finds it easier somehow.

These images show the S&T atlas view, then a matching view on a star app, and finally the view with a 2 degree field of view, upside down for reflector view and showing mag 9.5 stars, much more useful. Arcturus remains at a more realistic size and you can understand the other stars in the field.

IMG_2268.JPG

IMG_2274.PNG

 

IMG_2275.PNG

IMG_2276.JPG

Thanks, the pictures succinctly explained my query, the issue I think is getting the FOV right for my eyepiece, used my scope in the day now to make sure I've got used to the orientation which should help! I have night sky as an IOS app and also started using stellarium to plan what I want to see but liked the idea of an atlas for when I'm actually under the stars

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2 hours ago, Mr Spock said:

A good star chart will help. I use Cartes du Ceil as it allows you set it up however you like.

I've used Epsilon Lyrae as an example below. I set finder fields to match my 42mm, 22mm and 13mm eyepieces - it has a built in calculator, all you do is fill in the focal length of you telescope, the eyepiece's focal length and field of view. It then gives you finder circles on the chart.

I also have my labels set to show magnitudes - very useful!

A little used feature in CdC is the ability to flip the field around to match Newtonians. So you could have a chart the right way up, upside down, or, flip left and right!

finderchart1.thumb.jpg.003293963b6506e1ce7436b07c8249fe.jpg

CdC is one of the most useful and powerful programs out there. Like most it takes time to learn but is well worth the effort.

Thanks for information, I'm using stellarium at the moment but will have a look as CdC looks more in tune with my atlas

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34 minutes ago, Moonshane said:

Try the star hopping guide here :0)

Great thanks, I've downloaded and it makes more sense now, just need a clear sky to go out and practice more, have really caught the bug for this and got my first view of Saturn last night between the clouds

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