Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Making wire rings to use on the Pocket Sky Atlas.

  • Please log in to reply
17 replies to this topic

#1 Dpasqa

Dpasqa

    Mariner 2

  • -----
  • topic starter
  • Posts: 249
  • Joined: 23 Nov 2021
  • Loc: Asheville NC

Posted 14 January 2022 - 05:01 PM

I want to make wire rings to use with my Sky Atlas. I’d like to verify if my calculation is correct. Below is a formula that I used followed by an example of an eyepiece used in my SW100. Am I on the right track? Please disregard any errors in terminology, I am doing the best I can, I’m relatively new at this especially thinking at this level.

 

​Magnification equals

Focal Length\Eyepiece mm = magnification

 

TFOV equals 
AFOV\magnification = degree of eyepiece

 

This example is for my SW with a focal length of 900mm and using a Pentax 40mm eyepiece which has an AFOV of 70°

 

Magnification

900mm\40mm = 22x

TFOV
70°\22x = 3.18°
 

My assumption is I would take 3.18° and find it on the edge of the pocket atlas and make my ring the size that it indicates. Is this correct.


Edited by Dpasqa, 14 January 2022 - 05:04 PM.


#2 wrvond

wrvond

    Soyuz

  • *****
  • Posts: 3,907
  • Joined: 25 Sep 2014
  • Loc: West Virginia

Posted 14 January 2022 - 06:14 PM

Yes, you are correct.



#3 dadorfman

dadorfman

    Vostok 1

  • -----
  • Posts: 111
  • Joined: 24 Jan 2021

Posted 14 January 2022 - 06:26 PM

When I bought my Coulter Odyssey 10.1" dob in the 1990's, one of my first purchases was a laminated desk edition of Wil Tirion's SkyAtlas 2000.0.  I also bought the Field Finder, a publication of Spectra Astro Systems of Reseda, CA.  The Field Finder is a clear plastic sheet which overlays the pages of the SkyAtlas.

 

Directions: Lay the crosshairs over the center of the sky field you are aiming at.  The rectangles and tick marks outline photographic fields of view through a 35mm camera at the indicated focal lengths.  (lenses or telescopes)  Use the full Field Finder for the approximate 45mm field.  The inner three concentric circles correspond to the view through a TelRad finder.  The larger circles show the field of view 7X50, and 11X80.4 binoculars.

 

With the popularity of the Pocket Sky Atlas, hasn't someone come up with something like this for the PSA?


  • Dpasqa likes this

#4 wrvond

wrvond

    Soyuz

  • *****
  • Posts: 3,907
  • Joined: 25 Sep 2014
  • Loc: West Virginia

Posted 14 January 2022 - 06:36 PM

When I bought my Coulter Odyssey 10.1" dob in the 1990's, one of my first purchases was a laminated desk edition of Wil Tirion's SkyAtlas 2000.0.  I also bought the Field Finder, a publication of Spectra Astro Systems of Reseda, CA.  The Field Finder is a clear plastic sheet which overlays the pages of the SkyAtlas.

 

Directions: Lay the crosshairs over the center of the sky field you are aiming at.  The rectangles and tick marks outline photographic fields of view through a 35mm camera at the indicated focal lengths.  (lenses or telescopes)  Use the full Field Finder for the approximate 45mm field.  The inner three concentric circles correspond to the view through a TelRad finder.  The larger circles show the field of view 7X50, and 11X80.4 binoculars.

 

With the popularity of the Pocket Sky Atlas, hasn't someone come up with something like this for the PSA?

Most people that bother with the TFoV rings at all, only make one for each of their finder scopes. I think it the rare bird that makes one for the TFoV for each of their eyepieces in each of their scopes.


  • esd726 likes this

#5 Dpasqa

Dpasqa

    Mariner 2

  • -----
  • topic starter
  • Posts: 249
  • Joined: 23 Nov 2021
  • Loc: Asheville NC

Posted 14 January 2022 - 07:22 PM

Most people that bother with the TFoV rings at all, only make one for each of their finder scopes. I think it the rare bird that makes one for the TFoV for each of their eyepieces in each of their scopes.

I’m new at this concept. I never heard of it til I got my Sky Atlas, I guess I missed the point and thought you made one for the eyepieces you use the most. The book referred me to the S & T article on this subject. It talked about making one for the finder but mentioned making one for your highest magnification eyepiece. I wonder why they suggested that. I think it would be good to make several so you have an idea of what to expect, No? I like looking at the sky with my 25mm eyepiece at 22x with a 2.72 TFOV. I often use it as my finder because I see more stars and brighter than me 8x50 finder scope. I think in this case it would pe prudent to make one for that, right?


  • wrvond likes this

#6 Chris K

Chris K

    Viking 1

  • *****
  • Posts: 581
  • Joined: 20 Sep 2017
  • Loc: Long Island, Earth

Posted 14 January 2022 - 07:43 PM

I made one with a ring on both ends, like the wand you'd get in a jar of bubbles as a kid.

 

I made them to TFOV of the eyepiece i'd be star hopping with. I think one was 5º and the other was 4º.

 

I also went to the hardware store and picked out a few keyrings and put them on a string, but liked the wire version better.


Edited by Chris K, 14 January 2022 - 07:43 PM.

  • wrvond likes this

#7 Dpasqa

Dpasqa

    Mariner 2

  • -----
  • topic starter
  • Posts: 249
  • Joined: 23 Nov 2021
  • Loc: Asheville NC

Posted 14 January 2022 - 08:16 PM

I made one with a ring on both ends, like the wand you'd get in a jar of bubbles as a kid.

 

I made them to TFOV of the eyepiece i'd be star hopping with. I think one was 5º and the other was 4º.

 

I also went to the hardware store and picked out a few keyrings and put them on a string, but liked the wire version better.

That’s a good idea. One for my 25mm and the other for a second favorite eyepiece. What did you use for wire. BTW with the BT200 my widest TFOV is only 2.75”. You’re fortunate. To have 3 to. 4” FOV. Oh yea I’ll make one for the finder too. 



#8 Chris K

Chris K

    Viking 1

  • *****
  • Posts: 581
  • Joined: 20 Sep 2017
  • Loc: Long Island, Earth

Posted 14 January 2022 - 10:50 PM

That’s a good idea. One for my 25mm and the other for a second favorite eyepiece. What did you use for wire. BTW with the BT200 my widest TFOV is only 2.75”. You’re fortunate. To have 3 to. 4” FOV. Oh yea I’ll make one for the finder too. 

Ha, first i tried a wire hanger and realized i needed a strong man from the circus to get it into a nice circle.

 

I found some brass wire at Ace Hardware in the section that has picture hanging hardware. It was in a blister pack with cardboard backing hanging on a hook. You can also look at florists wire, you might even stop into a florist and as for some to test out.

 

I used a D-battery or C-battery to get the round shape I think. 


  • Dpasqa likes this

#9 wrvond

wrvond

    Soyuz

  • *****
  • Posts: 3,907
  • Joined: 25 Sep 2014
  • Loc: West Virginia

Posted 14 January 2022 - 10:56 PM

I’m new at this concept. I never heard of it til I got my Sky Atlas, I guess I missed the point and thought you made one for the eyepieces you use the most. The book referred me to the S & T article on this subject. It talked about making one for the finder but mentioned making one for your highest magnification eyepiece. I wonder why they suggested that. I think it would be good to make several so you have an idea of what to expect, No? I like looking at the sky with my 25mm eyepiece at 22x with a 2.72 TFOV. I often use it as my finder because I see more stars and brighter than me 8x50 finder scope. I think in this case it would pe prudent to make one for that, right?

Absolutely nothing wrong with making rings to match the TFoV of any eyepiece you wish. The idea, of course, is to use the ring to preview on the chart what you are going to see in the finder/eyepiece making it easier to identify what you are seeing.

I was merely pointing out that if a person created a ring for every eyepiece and every telescope, it could get difficult to keep track of which is which - especially in the dark. 


  • Dpasqa likes this

#10 astro744

astro744

    Viking 1

  • -----
  • Posts: 875
  • Joined: 22 Sep 2007

Posted 14 January 2022 - 11:29 PM

Another option is to draw up in a CAD type program all the circle sizes (labelled with angular size) to scale and then print to normal letter or A4 sheet.  Fit as many as you can on the sheet including Telrad.  Once you’ve printed then photocopy onto copy safe clear acetate sheet, (or simply print direct onto this sheet but may have to be laser rather than inkjet).

 

Maybe for the Pocket Sky Atlas use a sheet size with the same dimensions as the pages of the PSA and then you can carry the sheets inside the pages of the book.   My Millennium Star Atlas has such clear sheets for its scale.  Uranometria too.  I think it’s better than wire rings as it’s easier to carry and store.

 

I’ve probably used the deg circles half a dozen times in 37 years and this in the first year.  The field of view is what it is in the finder or eyepiece and I simply match the stars up with no need for field rings.

 

Edit:

I should acknowledge the publishers/authors.

Millennium Star Atlas, Copyright, Sky Publishing Corporation/ESA

Uranometria, Copyright Willmann-Bell/Tirion, Rappaport, Remaklus

 


Edited by astro744, 14 January 2022 - 11:58 PM.

  • lphilpot and wrvond like this

#11 Dpasqa

Dpasqa

    Mariner 2

  • -----
  • topic starter
  • Posts: 249
  • Joined: 23 Nov 2021
  • Loc: Asheville NC

Posted 15 January 2022 - 04:57 AM

Absolutely nothing wrong with making rings to match the TFoV of any eyepiece you wish. The idea, of course, is to use the ring to preview on the chart what you are going to see in the finder/eyepiece making it easier to identify what you are seeing.

I was merely pointing out that if a person created a ring for every eyepiece and every telescope, it could get difficult to keep track of which is which - especially in the dark. 

I am doing this for fun and as an education. I doubt I’d have the patience to make one for each eyepiece nor the dexterity. I think I’ll follow your advice and make one for the view finder and maybe one for the lowest magnification eyepiece if I make any. I usually start there, center the object and change eyepieces to increase the magnification. In the S&T article I was surprised how little of the sky I’m seeing. It has changed my perspective of how to star hop. 


  • wrvond likes this

#12 Dpasqa

Dpasqa

    Mariner 2

  • -----
  • topic starter
  • Posts: 249
  • Joined: 23 Nov 2021
  • Loc: Asheville NC

Posted 15 January 2022 - 05:00 AM

Another option is to draw up in a CAD type program all the circle sizes (labelled with angular size) to scale and then print to normal letter or A4 sheet.  Fit as many as you can on the sheet including Telrad.  Once you’ve printed then photocopy onto copy safe clear acetate sheet, (or simply print direct onto this sheet but may have to be laser rather than inkjet).

 

Maybe for the Pocket Sky Atlas use a sheet size with the same dimensions as the pages of the PSA and then you can carry the sheets inside the pages of the book.   My Millennium Star Atlas has such clear sheets for its scale.  Uranometria too.  I think it’s better than wire rings as it’s easier to carry and store.

 

I’ve probably used the deg circles half a dozen times in 37 years and this in the first year.  The field of view is what it is in the finder or eyepiece and I simply match the stars up with no need for field rings.

 

Edit:

I should acknowledge the publishers/authors.

Millennium Star Atlas, Copyright, Sky Publishing Corporation/ESA

Uranometria, Copyright Willmann-Bell/Tirion, Rappaport, Remaklus

Thanks but for me I never used CAD software, it be another learning curve. If I can get my formula to work I found a drafting circle template made of plastic that can work. It has lots of circles. But my formula doesn’t match up to what I see. 


Edited by Dpasqa, 15 January 2022 - 06:44 AM.


#13 astro744

astro744

    Viking 1

  • -----
  • Posts: 875
  • Joined: 22 Sep 2007

Posted 15 January 2022 - 05:26 AM

I only thought of CAD because I use it everyday and it’s easy to scale correctly.  Get your self a sheet of clear acetate overlay and a black marker.  Either draw different circles with a simple drawing compass that would hold the marker or use anything round as a template scaled to match your chart.  You can draw circles to match your eyepiece/telescope combination or simply circles to represent different fields say every 1/2 deg of whatever you prefer.



#14 firemachine69

firemachine69

    Viking 1

  • *****
  • Posts: 647
  • Joined: 19 May 2021

Posted 15 January 2022 - 07:11 AM

Most people that bother with the TFoV rings at all, only make one for each of their finder scopes. I think it the rare bird that makes one for the TFoV for each of their eyepieces in each of their scopes.

 

 

My AT102edL with the 30mm ES82 gives a TFOV of just under 3.5 degrees, nearly the size the of 4 degree circle that comes with the clear overlay in my deluxe guide.

 

I'll get a smaller bit similar one printed out on a Cricut printer. 



#15 Dpasqa

Dpasqa

    Mariner 2

  • -----
  • topic starter
  • Posts: 249
  • Joined: 23 Nov 2021
  • Loc: Asheville NC

Posted 15 January 2022 - 07:14 AM

Hey folks, thanks for your comments and help with this. At first when I visually looked the degree marks and looked at Orions sword I thought my calculation was way off. But I found my old drafting circle template and placed it over the degree marks on the atlas, I found the correct circle size. Once I got the right circle I placed it over Orions sword it was right on. The drafting template has Too many circles so I’ll try astro744’s idea and make one out of Mylar or something I can find at a hardware store. I can also use it as a bookmark. The wire ring is good but hard to keep in my book. This has been a fun learning project. 


Edited by Dpasqa, 15 January 2022 - 09:02 AM.

  • wrvond likes this

#16 Blueox4

Blueox4

    Viking 1

  • *****
  • Posts: 843
  • Joined: 26 Nov 2015
  • Loc: Upstate New York

Posted 15 January 2022 - 07:50 AM

This article touches on this. 
 

https://skyandtelesc...-the-telescope/


  • wrvond and Dpasqa like this

#17 Dpasqa

Dpasqa

    Mariner 2

  • -----
  • topic starter
  • Posts: 249
  • Joined: 23 Nov 2021
  • Loc: Asheville NC

Posted 15 January 2022 - 12:11 PM

I only thought of CAD because I use it everyday and it’s easy to scale correctly.  Get your self a sheet of clear acetate overlay and a black marker.  Either draw different circles with a simple drawing compass that would hold the marker or use anything round as a template scaled to match your chart.  You can draw circles to match your eyepiece/telescope combination or simply circles to represent different fields say every 1/2 deg of whatever you prefer.

Hey Astro744. I took your advice and got a piece of mylar from the cover of an old binder. I drew my circles and it works perfectly. Now I have a second bookmark too. It’s not very accurate because using a marker is hard to get it just right. But it’s in the ballpark. I did one for my BT highest and lowest magnification (lowest just for grins). I did one for my highest magnification on my SkyWatcher too. I’m amazed at how little of the sky that I am viewing in how many stars I see, I can’t see them with the naked eye.

 

I know this is quite silly. After doing this I can guesstimate with my high when I look at the sky charge. But I’ve learned a lot in the process and I sure as heck never knew how little of this guy I was seeing. I always thought I was seeing the better part of a constellation when I was only seeing one star, ha ha. It’s all fun. 


Edited by Dpasqa, 15 January 2022 - 12:13 PM.

  • astro744 and wrvond like this

#18 astro744

astro744

    Viking 1

  • -----
  • Posts: 875
  • Joined: 22 Sep 2007

Posted 15 January 2022 - 01:19 PM

Extend your arm out toward the sky and hold your index finger out perpendicular to your arm.  The width of your fingernail is about one degree.

 


  • Dpasqa likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics